[Paleopsych] New Scientist: Instant Expert: Christmas Science
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Instant Expert: Christmas Science
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[All articles appended. This is going to all kinds of people, Christian or
not, for its scientific interest. Enjoy!]
Special Reports On Key Topics In Science And Technology
Ever wondered how they celebrate Christmas at the [1]South Pole, pondered the
psychology behind [2]Christmas card lists and [3]Christmas dinner, or wondered
why an average of 80,000 Brits end up [4]hospitalised every holiday season? Here
NewScientist.com guides you through the science of all things festive.
[5]Partying to excess and [6]stuffing our faces have become synonymous with the
Christmas season. Watch out though - eating too much just before bed really can
give you [7]bad dreams. Turkey, [8]pudding, [9]festive spices, mulled wine and
other [10]exotically-flavoured booze are just some of the food items you're
likely to encounter.
Hulking great broiler turkeys bare [11]little resemblance to the fleet-footed
wild birds they are descended from. Though they taste good, it's important to
cook them thoroughly to avoid a bout of festive [12]food poisoning.
Christmas is the season to give, but most people look forward to receiving too.
However, if you find that after the [13]orgy of pre-Christmas spending, the
[14]tree isn't surrounded by a stack of gifts bearing your name, this is how to
[15]take action. Targeting a grandparent who has the most undisputable genetic
link to you may be the key. But be careful if you receive a gift card though,
[16]as retailers are raking in our cash from unclaimed vouchers.
On the other hand, if you've got to buy gifts for people you don't like, we have
some tips for [17]bypassing the Christmas spirit that would make Ebenezer
[18]Scrooge proud.
Ho, ho, ho!
Father Christmas is a far more loveable and jolly Christmas icon. But have you
ever wondered how - by [19]reindeer power alone - he manages the [20]incredible
feat of delivering gifts to 850 million or so households in a single night? Could
Santa could be using [21]wormholes to travel through space and time?
If the big guy ever finds it all too exhausting, he might consider moving to the
[22]north pole of another planet. However, while he is still doing a useful job
here on Earth, the North American Aerospace Defense Command (NORAD) in Colorado
provides an annual online tracking service to [23]map Santa's progress around the
world on Christmas eve.
For people of a less jolly disposition, such as those afflicted by [24]seasonal
affective disorder, Christmas is a depressing time of year. Some may choose to
[25]skip the holidays altogether. Entering into the Christmas spirit might be
better for your [26]state of mind though - research suggests just one really
fantastic Christmas might ensure that the sight of tinsel and fairy lights gives
you a warm, cosy feeling forever.
Decorating our homes with tinsel, [27]fake snow, [28]icicles and other sparkly
decorations is another longstanding Christmas tradition. Old-fashioned
decorations such as [29]holly, ivy and mistletoe may have a sinister side though,
despite their beauty, and commercial harvesting of moss is [30]depleting wild
populations.
More kitsch forms of decoration such as life-size glowing reindeer, illuminated
nativity scenes and animatronic [31]snowmen found on porches throughout the US,
are currently getting a [32]21^st century digital makeover.
John Pickrell, 22 December 2005
References
1. http://www.newscientist.com/channel/being-human/christmas/mg16021658.900
2. http://www.newscientist.com/channel/being-human/christmas/mg18024265.900
3. http://www.newscientist.com/channel/being-human/christmas/mg18424793.000
4. http://www.newscientist.com/channel/being-human/christmas/mg16021656.400
5. http://www.newscientist.com/channel/being-human/christmas/mg18825311.500
6. http://www.newscientist.com/channel/being-human/christmas/mg17223225.500
7. http://www.newscientist.com/channel/being-human/christmas/mg16822704.100
8. http://www.newscientist.com/channel/being-human/christmas/mg17022867.100
9. http://www.newscientist.com/channel/being-human/christmas/mg16822704.400
10. http://www.newscientist.com/channel/being-human/christmas/mg18825312.500
11. http://www.newscientist.com/channel/being-human/christmas/mg16021655.600
12. http://www.newscientist.com/channel/being-human/christmas/dn6820
13. http://www.newscientist.com/channel/being-human/christmas/mg14419510.800
14. http://www.newscientist.com/channel/being-human/christmas/mg14419572.300
15. http://www.newscientist.com/channel/being-human/christmas/mg18424791.800
16. http://www.newscientist.com/channel/being-human/christmas/mg18825312.200
17. http://www.newscientist.com/channel/being-human/christmas/mg16822703.900
18. http://www.newscientist.com/channel/being-human/christmas/mg15020365.000
19. http://www.newscientist.com/channel/being-human/christmas/dn4491
20. http://www.newscientist.com/channel/being-human/christmas/mg12416965.500
21. http://www.newscientist.com/channel/being-human/christmas/mg14419573.700
22. http://www.newscientist.com/channel/being-human/christmas/mg16422184.800
23. http://www.newscientist.com/channel/being-human/christmas/mg16422183.500
24. http://www.newscientist.com/channel/being-human/christmas/mg17223225.100
25. http://www.newscientist.com/channel/being-human/christmas/mg15220615.600
26. http://www.newscientist.com/channel/being-human/christmas/mg18024266.000
27. http://www.newscientist.com/channel/being-human/christmas/mg16822703.600
28. http://www.newscientist.com/channel/being-human/christmas/mg18024265.300
29. http://www.newscientist.com/channel/being-human/christmas/mg16422183.400
30. http://www.newscientist.com/channel/being-human/christmas/mg18424792.700
31. http://www.newscientist.com/channel/being-human/christmas/mg16021655.800
32. http://www.newscientist.com/channel/being-human/christmas/mg17623746.600
'tis the season to be jolly in Antarctica
* Ian Anderson
* 19 December 1998
AT THEIR base camp, the New Zealand scientists like to start celebrating
Christmas Day early. In fact, last Christmas, at Scott Base on the edge of the
Ross Sea, Christmas dinner began at 11 pm on Christmas Eve and lasted well into
the afternoon of Christmas Day. It must have something to do with the 24-hour
daylight at this time of year: with midday and midnight virtually
indistinguishable, planning any event takes on a tinge of the surreal.
At the New Zealanders' festivities, formal dress is expected-although not the
sort seen at the party held last month, when all in attendance, men included, had
to wear skirts. No, at the Christmas do, men wear tuxedos with just the women in
long dresses. Members of the New Zealand 3 Squadron, the Iroquois helicopter
squadron, donned the white jackets and pressed blue trousers of their mess kits.
The helicopter pilots, in Antarctica to ferry supplies and people to remote
locations, waited on the candlelit tables. The windows were blacked out. The best
silverware and the whitest of tablecloths were used. The Christmas tree had to be
artificial for under the Antarctic treaty no trees can be taken down to
Antarctica.
"Whether we start early this year is up to the social committee," says Paul "Ham"
Hamilton, the cook at Scott Base. "Whatever is decided, I'll be ready. When we do
something down here, we go the whole hog." Ham, and assistant cook Chris Bray,
are preparing a feast for the 60 or so people who will be on base at Christmas.
(Scott Base ordinarily caters for 80 or more during the Antarctic summer, but
some take the 7-hour ride on the Hercules back to Christchurch to be with their
families.)
Ham manages a respectable spread on the day: home-made pâté, soup, hot turkey,
ham and pork with all the trimmings, a cold meat collation, at least four salads,
steamed pudding and assorted desserts and cheeses, all washed down by good New
Zealand wine. "We don't exactly starve down here," says Mike Mahon, a technician
about to spend his third Christmas in Antarctica. Ham can even just about
guarantee fresh vegetables for the salads. They grow in a hydroponic hothouse,
set up on the ice a short walk from the main buildings. Under UV lighting, the
plants are kept at a constant temperature of 25 °C, with water supplied by a
desalination plant.
Christmas dinner is a much bigger event at McMurdo, the American base two
kilometres away. Thirty-one cooks, with at least that number of volunteers, will
use 10 convection ovens and nine baker's ovens to prepare Christmas dinner for
1200 people. They will eat in four one-hour shifts of 300 people each, beginning
at 3 pm on the day. Antarctic cod, a delicacy caught from the sea ice just
offshore, will be on the menu, as will more than 140 kilograms of duck and some
200 kilograms of fillet steak, not to mention 180 litres of gravy and over 200
litres of dressing.
In the days leading up to Christmas Day, helicopters from both bases will fly in
with hampers for the scientists and field assistants who will spend Christmas on
the ice. Some of these doughty researchers will manage to cook a chicken in a
pressure cooker. Teams with adjacent field camps will get together for the day,
and even exchange gifts-one member usually dresses up as Santa Claus. There is
music and back at base, carollers from the Chapel of the Snows, a Christian
church at McMurdo, will visit both bases. In the field someone will have a mouth
organ or a squeezebox and a songbook of carols.
There is one activity held at Scott Base on Christmases past that is unlikely to
be repeated, but you never know. The Polar Plunge involves diving into the icy
seawater wearing nothing but socks and a harness to pull you out if you get into
difficulties. Such pursuits don't go down well on a full stomach.
The psychology of the perfect Christmas dinner
* 25 December 2004
* Graham Lawton
IT'S a rite of passage that's been lurking on the horizon since you left home.
But no amount of forward planning can prepare you for this. Christmas dinner is
at your place - and you're doing the cooking.
You know the score: you're going to have to conjure up at least three courses,
along with wine and cheese. A choice of desserts is mandatory. You'll run out of
pans, and will have to wash up every 15 minutes. And worst of all, the world
expert - your mum - will be there, casting a critical eye over your efforts. So
how can you make sure dinner is divine?
It's easier than you might think. Good food, it turns out, is all in the mind.
The way people perceive your dinner has less to do with what's on their plate
than what's in their heads. At least that is what Brian Wansink, a food
psychologist at the University of Illinois in Urbana-Champaign, has found.
Among other topics, Wansink studies how the right environmental cues can make
ordinary food seem fantastic. He has spent years feeding people cheap,
mass-produced, bog-standard or downright horrible food and then bamboozling them
into believing they like it. "Taste is tremendously subjective," he says. "People
are not too smart to be fooled."
Most of Wansink's work has focused on places such as canteens and restaurants,
but you can turn a lot of what he has learned to your advantage. The basic idea
is to harness what psychologists call the "halo effect". Put simply, this means
that if you make people feel good about just a few aspects of an experience,
everything else about it will seem better.
Restaurant food benefits hugely from the halo effect, Wansink says. It is no
accident that restaurants pay lots of attention to their decor and lighting, the
appearance of the waiting staff, the look of their menus and even the names and
descriptions of their dishes. All conspire to create the belief that the chef
will be taking similar pains over your meal. And if the food is half-decent, it
works.
Wansink has shown as much by experimenting on the staff and students who frequent
his university cafeteria. In one experiment he fed people pieces of a chocolate
brownie that had seen better days, then asked them how much they would be
prepared to pay for it. People who got the brownie on a paper plate with a cheap
napkin were not impressed, saying on average that they would only stump up 57
cents for it. But when they got the same shrivelled piece of cake dusted with
icing sugar on a glass plate, they were lavish in their praise, offering to stump
up $1.12. "That's almost twice as much," Wansink enthuses. The lesson here is
simple: use your best crockery, buy some nice napkins, and camouflage your
accidents with garnish.
But it's not just about presentation. The way you describe your food dramatically
alters how people rate it. In another experiment, Wansink served people cheap
canned meatballs. Not surprisingly they weren't a big hit. But when he described
them as "spicy meatballs", people liked them much more, saying they tasted
"deeply spicy" - even though they were about the blandest thing that he could
find. And when he fobbed the same ghastly stuff off under the label of "local
family gourmet recipe", people suddenly loved it.
"Labels really help," says Wansink, but not any old labels. To pull this trick
off you have to tap into one of three basic food-related emotions: sensory
(descriptive words such as tender or creamy), nostalgic (traditional, home-baked)
or geographic (Italian, French). Of course, you can't label dishes at the
Christmas dinner table, and if you announce your dessert as "traditional creamy
Cajun trifle", people are going to look at you in a funny way. But there are
variations you can use. Take every opportunity to talk up your ingredients.
Casually mention that you got the parsnips from an organic farmers' market, even
if you didn't. And if someone remarks on the stuffing, mention with a chuckle
that they should make sure they get some more before it all goes: you won't be
hand-peeling chestnuts again next year.
Talking turkey
Even if you find it hard to tell lies about vegetables, there is one element of
the meal you must talk up. While most people can tell the difference between
spoiled meat and fresh meat, they struggle to distinguish between OK meat and
really good-quality meat. "So they look for environmental cues to reinterpret the
sensory experience," Wansink says. "There are lots of ways to make people think
'Oh yeah, this is the really good stuff'." The lesson? Pretend you know an
organic turkey farmer.
Props can create a halo effect too. Leave a bunch of flat-leaved parsley or
chervil in a prominent position, even if you didn't use any. When guests wander
into the kitchen, fiddle about with complicated pieces of kitchen equipment and
obscure-looking utensils.
At this point you may be getting worried. Surely you're inviting disaster and
ridicule by drawing so much attention to the food? Not a bit of it. Wansink has
shown that making people pay close attention to the food they're eating makes it
taste better. He once gave his long-suffering colleagues a cheap, mass-produced
vegetable juice and asked them to rate its flavour. When they were simply told it
was a "new type of juice" they said it was OK. But if he told them it was a
carefully blended mixture of vegetables and asked them to identify as many as
they could, they rated it much more highly.
The wine can also help: whatever you serve, make sure it at least sounds good.
Wansink once did an experiment where he served a French meal with complementary
wine - a dire, $2-a-bottle plonk. When people knew it was rubbish they rated the
whole meal quite poorly. But when he stripped the labels off the bottles and
replaced them with something more classy, they rated the food much more highly -
and ate more.
By now you should be well on your way to becoming a legend in your own kitchen.
But there is one more way to score points. As part of his studies, Wansink has
also investigated what earns people a reputation as a good cook. He found that a
great reputation comes in three distinct flavours. The first two are bad news for
the unskilled: Wansink calls them "inventive" and "new recipe" cooks, and to
qualify as either you need to be good at cooking. Both categories are
knowledgeable, skilled and keen; the kind of people who grow their own herbs and
think peeling shallots is fun. The only real difference between them is that "new
recipe" cooks use books, whereas "inventive" cooks make it up as they go along.
This is not the sort of thing you can fake.
But there is a third way to gain a culinary reputation, and it has nothing to do
with the food. "Social occasion" cooks stick to simple, well-known recipes -
think casseroles - and use the time they saved on shallot-peeling to make their
guests feel at home. So if you're doing Christmas dinner this year, banish all
thoughts of cooking something unusual. Don't even entertain the notion of
stir-frying the sprouts in ginger and garlic: put them on to boil, and open the
wine. Then all you have to do is mingle.
Just one more thing. These tricks are tried, tested and trustworthy, yet be
warned. By all means put them to work, but glory can come at a price. Don't blame
us if your mum books herself in for next year too.
The magic number
* 20 December 2003
* Meredith F. Small
IT'S one of the great Christmas traditions. If you celebrate the holiday at all,
by now you will probably have dispatched greetings to family, friends and
colleagues. That group is unique to you, but in one remarkable respect our
Christmas card lists are very similar: their length. It turns out that most of us
send cards to around 150 people. What's more, this magic number of intimacy seems
to be an evolutionary legacy reflecting the natural size of our species' social
groups. Even in an era of sophisticated global communication, it seems, we are
only able to keep up with the same number of people as our hunter-gatherer
ancestors.
It's not easy to probe people's card-sending habits. The holiday season is busy
and stressful enough without having to answer detailed questions about each
person on your list. But when UK-based anthropologists Russell Hill from the
University of Durham and Robin Dunbar from the University of Liverpool roped in
their own friends, they were pleasantly surprised by the response. "It was
amazing how many people already kept records of who they sent cards to and those
they received," says Hill. "A section of the population, it turns out, is
actively monitoring its social networks."
The anthropologists managed to recruit 43 card senders who sent a total of 2984
cards - about 68 per person. If you take the entire household into account, each
sender contacted a network of 154 friends, family and acquaintances, on average,
or 125 if you only count the people named on the envelopes.
The number 150 was eerily familiar to Hill and Dunbar. In the early 1990s, Dunbar
carried out a study of non-human primates, comparing the size of the neocortex -
the part of the brain associated with higher functions such as intelligence -
with the typical group size for each species. All primates, including humans, are
social creatures who depend on each other for survival, so you would expect some
kind of correlation between brain size and the ability to deal with complex
social networks. Dunbar did, in fact, discover a linear relationship, with group
size increasing as a function of brain size. And a similar pattern has since been
found among social carnivores and cetaceans. Using his non-human primate scale,
Dunbar then predicted that humans should have social networks of about 150
people.
Support for this number comes from tribal societies and from history. Modern
hunters and gatherers typically live in clans of about 150 members (although they
can range from 90 to 200); Neolithic villages in the Middle East also contained
between 150 and 200 people; and according to the General Synod of the Church of
England, the ideal size for a congregation is 154. The Christmas card list, Hill
and Dunbar suggest, is simply the modern Western manifestation of an ancient
ability to maintain only so many social contacts.
But why is 150 the magic number for our species? Ecological and economic factors
play their part. The size of hunter-gatherer groups, for example, is constrained
by the amount of territory people can cover and its productivity in terms of
food. Smallholders, likewise, are only able to feed a certain number of people
from their land. But from around 12,000 years ago, with the beginnings of
agriculture, human societies have had the economic potential to expand into vast
cities.
We can cope with such large groups because we are able to recognise the faces of
the many thousands of people we encounter in a lifetime. But, argue Dunbar and
Hill, we do not have a social relationship with all these people. Instead, we
tend to build subgroups of around 150. Dunbar suspects this must have some
adaptive value, pointing out that networks seem to fall apart if they get any
bigger. "Hutterite communities in the United States split in two when they reach
150 because they claim they can't control the group by peer pressure alone when
it goes beyond that number," he says. "There is also a folk rule in business
organisation which says you need a management structure once your organisation
gets above 200 because rivalries build up."
The other factor limiting the size of our social networks is time. Baboons and
chimps spend around 20 per cent of each day on one-to-one grooming to consolidate
their bonds, and Dunbar has argued that gossip is the human equivalent. The big
difference is that we can effectively communicate with up to three people at
once, which means we can form bigger social networks than other primates. Beyond
this limit, however, conversational groups tend to break up. And modern
technology is no help. It allows us to throw our net wider in geographical terms,
but does not increase the number of people in it. "Email and snail mail let you
maintain contact with distant network members," says Dunbar. "But this kind of
communication doesn't allow you to create a deep relationship." Because the
quality of our relationships matters, we still only have the cognitive ability to
maintain the same number as our ancestors.
Previous studies have shown that most people can define precisely a group of
about three to seven very close friends to whom they turn in times of distress, a
group of about 15 who provide sympathy and support, and a wider circle of friends
of about 35 who represents their personal community. Hill and Dunbar confirmed
this when they asked card senders to rate their emotional attachment to each
person on their list on a scale of 0 to 10. The card senders each identified a
close circle of seven friends they saw regularly, a larger group of about 21 that
they saw less often, and a group of 35 people to whom they were not so
emotionally attached, but were still closer than the full list. The researchers
also found that senders are willing to invest extra time in long-distance
relationships that they value, often including a letter or long message with
cards sent to people who lived far away and whom they only contacted once a year.
Our Christmas card lists are maps of who we know and who we care about. But
Christmas is not just a time to write cards; it also a time to reflect on what
all these relationships mean. Friendships fluctuate over time: an acquaintance
may become a friend, or a member of our inner circle might drop out. Although we
can only handle the same number of social connections as our ancestors,
globalisation means we have a lot more choice about who to include in our
network. That's why each year we need to make that list, and check it twice,
before we lick the stamps.
Lethal Xmas
* 19 December 1998
* Stephanie Pain
CHRISTMAS comes but once a year. And that's probably just as wellnot just for
those of us with Scroogish tendencies, but for doctors, fire-fighters and loss
adjusters. The season of joy is also the season of strange accidents and unusual
injuries. Never mind the perils of poorly cooked poultry and high-velocity
corkswhich are year-round hazards these days. Almost everything that makes
Christmas festive lands hundreds of people in hospital each year.
Christmas trees are a menacereal or artificial, with their fairy lights and
candles, paper chains, tinsel and baubles. Boughs of holly, ivy wreaths and
sprigs of mistletoe: poisonous every one. Artificial snow? It irritates the
lungs. An open fire to roast the chestnuts on? Forget it if you want to stay
safe. Crackers? Only if you're wearing safety goggles: the "bangs" can burn and
airborne novelties inflict serious eye injuries. Even the pudding can put you in
the emergency ward. Silver coins concealed among the currants can choke a child,
while adults face the danger of "Christmas pudding flashback". This has nothing
to do with memories of puddings past, but a lot to do with Christmas spirits. If
your pudding isn't perfect without some flaming brandy, remember to stop pouring
before you strike the match.
"In terms of accidents, home is the most dangerous place of all," says Roger
Vincent, a spokesman for Britain's Royal Society for the Prevention of Accidents.
"We tend to see home as a safe haven. We relax and forget about safety. And at
Christmas we relax even more." RoSPA reckons that over the 12 days of Christmas
around 80 000 people in Britain end up in hospitaland 130 will die.
Some injuries, particularly falls, burns and scalds, are inevitable when crowds
of people make merry in unfamiliar rooms, armed with hot drinks or glasses of
sherry, surrounded by piles of slippery wrapping paper and stray toys. The
kitchen is especially dangerous, with dishes of hot fat and sharp knives in the
hands of a tipsy and distracted cook.
Other accidents are linked to the more frivolous features of Christmas. For
instance, in a report published in 1990, Britain's Consumer Safety Unit estimated
that nationwide there were 2000 injuries caused by Christmas trees, fairy lights
and decorations. Decorations were to blame for just over half the injuries. And
almost half of these were the result of falls as people balanced precariously on
tables, chairs and other unstable pieces of furniture to hang trimmings or fix
the fairy to the top of the tree. The remainder were mostly internal injuries to
children who had chewed on glass baubles or other tempting decorations.
Around 34 per cent of accidents were linked to trees, and ranged from a poke in
eye with a stout twig to cuts and bruises from inexpert attempts to lop off
branches. Only to be expected perhaps. But there are some accidents you can't
foresee. "In one case the victim was a 28-year-old male who was walking past a
Christmas tree when an insect flew in his ear," says the report.
The final 12 per cent of injuries were attributed to fairy lights burns, electric
shocks and internal injuries to toddlers who chewed the bulbs. "Lights are safer
than they used to be," says Vincent. But Christmas is a time for tradition and if
you only use them once a year, those ancient lights should last for ever,
shouldn't they? Not when they are crumpled into a heap in the attic for the rest
of the year, the wires bent and knotted. Damaged wires can electrocute. Some
older lights have large bulbs which become hot enough to burn hands or ignite
tinder-dry pine needles. And, while fire brigades say fake trees are safer, that
doesn't include the metallic sort. Faulty wiring on the fairy lights can
electrify the whole tree.
And that's not all. According to the US Consumer Product Safety Commission in
Washington DC, trees are responsible for about 500 fires in the US each
Christmas, causing some $20 million worth of damage to homes. The risk of a fire
in the home is 14 per cent higher over the Christmas holiday in the US and these
fires are 30 per cent more likely to result in death, says the US Fire
Administration.
Christmas trees are full of inflammable resin and covered with kindlingin the
form of fine needles that quickly dry out in a heated house. The fresher the
tree, the safer it is. "Bounce its butt before you buy," advises the US Consumer
Safety Commission: a newly cut tree won't leave a pile of needles on the ground.
Assuming the tree lasts until Twelfth Night, what then? Enough people have
attempted to get rid of their tree by feeding it into the fire to prompt a deluge
of warnings each year from fire departments. One American family lost everything
but received no sympathy from their insurers.
"They decided to push the pointy end in first," says a friend of the family.
"They thought they could push the trunk in and burn it bit by bit." When the
house was razed to the ground the insurance company was reluctant to pay up.
"Tantamount to arson", was the loss adjuster's verdict.
In Britain, too, the number of house fires soars over the Christmas holiday.
There were 213 fires a day in December 1996, 8 per cent more than the daily
average during the winter months. The Home Office, which is responsible for
Britain's fire service, puts the blame squarely on Christmas, pointing the finger
at faulty fairy lights and trees placed too close to hot coals or candles.
Trees are not the only fire risk. "There's been an increase in candle fires as
decorative candles have become popular," says Vincent. Piles of wrapping paper
will ignite in a flash. And of course, there's that real fire. For most of
winter, central heating is fine, but come Christmas and suddenly there's nothing
to compare with a warm hearth and a glow in the grate. Put the cards on the
mantelpiece and hang a stocking or two for Santa, and the risks of a fire
multiply. And if you have a fire just once a year, the chances are that the
chimney hasn't been swept and no one has checked the flue.
The fire needn't set the house alight to put you at risk. If your flue is faulty,
there is a danger of carbon monoxide poisoning. Around 50 people in England and
Wales die each year from carbon monoxide poisoning. Many more people suffer the
effects of poisoning but the symptoms are often mistaken for flu or food
poisoning. A few Christmases ago, a London family decided to light their fire as
a special Christmas treat. They were found gathered around itunconscious. Tall
buildings around the house prevented the escape of exhaust gases, which flooded
back down the chimney into the room. Fortunately, this particular family was
discovered in time.
Carbon monoxide is a stealthy killer, but it's not the only poison to worry
about. Badly thawed and undercooked turkeys lay hundreds low with food poisoning
each Christmas. Last Christmas, the Medical Toxicology Unit in London received
around 100 calls about children who had eaten holly berries, 30 inquiries about
mistletoe, 80 about the Christmas cherry, 10 about poinsettias and one about the
Christmas rose. Mistletoe berries contain a mix of toxic proteins and alkaloids
which irritate the stomach and slow the heart and, in bad cases, can induce
hallucinations. Holly berries might be popular with birds but they are not good
for humans, although they were recently downgraded as a poison. "Holly is not as
toxic as we thought," says Virginia Murray, deputy medical director of the
Medical Toxicology Unit. "But I wouldn't recommend you make jam with it."
Ivy's not too good for children either, but it tastes so bad that few children
eat the berries. There seems to be some confusion about how poisonous poinsettia
is, but the leaves contain unpleasant irritants. "If you chew them you'll get a
nasty mouth rash and an upset stomach," says Rose Ann Soloway of the American
Association of Poison Control Centers in Washington DC. The Christmas rose,
Helleborus niger, causes such severe diarrhoea that the ancient Greeks used it as
a chemical weapon in the sixth century BC. Another popular pot plant at this time
of year is the orange-berried Christmas cherry, Solanum pseudocapsicum. Like its
close relatives, the nightshades and the potato, this plant contains alkaloids
that cause sickness and stomach pains.
The most common poison of all is alcohol. While most adults suffer nothing worse
than the whirling pits, a mouth like sandpaper and a bad headache, children are
at much greater risk. Every year, a small number of children suffer alcohol
poisoning, usually after draining the dregs left by adults. "People have a party
and it's not surprising they don't clear up at 2 am," says Vincent. "But then the
children get up early, go downstairs and drink the leftovers." Children suffer
worse effects than adults, and not just because they are smaller. "Weight for
weight, children are much more susceptible," says Murray.
And if you think there can't be anything else to worry about, don't forget the
presents. Leaving perfumes and chocolates under the tree is asking for trouble if
you have children or pets (chocolate can kill a dog). And toys can kill.
According to the US Consumer Product Safety Commission, in 1996 toy-related
injuries put 140 000 children in hospital in the US; 13 died from their injuries.
In most cases, accidents happen when small children get hold of toys intended for
older onesnot just the chemistry sets, says Soloway, but toys with small parts
that can choke a toddler. Lead painted toys are rare these days, but doctors
still see a few cases of poisoning. Button batteriesthe sort that power many
toyspose a different threat. "A swallowed battery," says Soloway, "is a real
medical emergency if it lodges in the oesophagus." The charge around the battery
burns a hole in the soft tissue. If the battery reaches the stomach, it is
probably safeas long as it doesn't break up and shed its load of mercury.
So how does anyone survive Christmas? There is plenty of advice around on how to
stay safe. Buy an artificial tree and invest in a new set of lights. Wrap the
mistletoe in safety nettingor better still stick to plastic sprigs. Empty the egg
nog immediately the last guest has gone. Or perhaps you'd be better off on an
Australian beach, where Christmas Day sees turkey-stuffed crowds soaking up the
sun. No worries there. Except, that is, for the big jump in the number of
drownings, barbecue burns and shark attacks. Happy Christmas.
Get stuffed
* 22 December 2001
* Kate Douglas
POURING tomato soup through someone's nose is sometimes the best way to discover
why Christmas is a weight-watcher's worst nightmare. OK, so it's a far cry from
turkey with all the trimmings, but this is still the cutting edge of
"hedonics"-the study of gastronomic pleasure. Sit back, relax, and loosen your
belt another notch if it makes you feel more comfortable, because what you're
about to read may leave you feeling rather queasy.
There's a lot we don't understand about the problems of overeating, but Martin
Yeomans of Sussex University and Steve French of Sheffield University have set
themselves the task of probing the mystery. Yeomans and French are the "good cop,
bad cop" of appetite interrogation-the one specialising in the pleasures of
eating, the other an expert on fullness and the pain of overindulgence. Between
them, they've just about got it covered. Yeomans can explain that irresistible
urge some of us have to trough an entire litre tub of Ben & Jerry's Caramel Chew
Chew even though we've just eaten a full meal. And French knows why feeling full
to bursting point prevents most people-Mr Creosote excepted-reaching for that
last, explosive, wafer-thin mint. "The novel aspect of our work is trying to
bring together two parallel strands and see how they interact," says Yeomans.
Hedonism research is no box of chocolates. In fact, for Yeomans and French's
volunteers it is mostly tomatoes. For starters they get tomato soup-through the
nose if the researchers want to measure the satiating effects of various
nutrients independently of any eating pleasure they might provide. Soup is
followed by pasta with-you've guessed it-tomato and onion sauce. The "tasty"
version of this dish contains herbs and seasonings and the "bland" variety comes
au naturel. It's a lonely business pushing out the frontiers of appetite
research. Each volunteer is tested separately, with only a computer as a
lunchtime companion, secretly assessing how much of the palatable or bland food
he has eaten and interrupting him every few forkfuls to ask how he is feeling vis
à vis the old appetite. Christmas dinner it is not, but the results are
incontrovertible: tasty food initially boosts hunger more than bland food, it
makes you feel full more slowly, and leaves you eating more overall.
But if there's one thing this duo has learned in almost a decade of nasal drips,
intragastric infusions and tasteless pasta, it's that there's no simple
explanation for gluttony. Their distasteful experiments have convinced them that
how much we eat depends on the outcome of a battle between the opposing forces of
pleasure and satiation. And if some of you are already reaching for another mince
pie, muttering that with all the pleasure on offer at this time of year you can't
be held responsible for your actions, then tuck in, because you're probably
right. French, Yeomans and an assortment of other appetite researchers have
evidence that confirms the worst fears of every calorie counter-Christmas really
is out to get you.
Everything about the festive season makes you overindulge. Just take a look at
the "big meal" itself. The simple act of sitting down with those you know and
love has already sealed your fate. John de Castro from Georgia State University
in Atlanta has found that in the company of friends, you can expect to put away
44 per cent more nosh. Your consumption increases in proportion to the number of
people at the table and, worse still, the more you're enjoying yourself, the more
courses you'll eat.
You will probably start with an aperitif. It may look harmless, but Yeomans's
experiments show that a single tipple before you tuck in sets things off on the
wrong footing. When he plied some of his gastronomic guinea pigs with a libation
disguised as apple-flavoured pop shortly before lunch, they ended up eating more
than other volunteers who had consumed real soft drinks, even though they had no
idea they had been drinking alcohol. And "bah! humbug!" to diet coke drinkers who
think they can fill up on carbon dioxide and aspartame, because several studies
show that only drinks containing large amounts of real sugar will knock a hole in
your appetite.
You might want a snack with that drink. Go on, treat yourself to a sliver of
salami, or perhaps a nice creamy dip with some of those hand-fried potato chips
on the side. Breadsticks and other carbohydrate-laden, low-fat snacks can take a
back seat because, well, it's Christmas. But be warned: you're bound to be
nobbled by those high-fat nibbles, because you are destined to eat more of
them-even supposing they tasted no better than the carb-rich, low-fat
alternatives. The explanation, according to French, is that despite containing
fewer calories, high-carbohydrate snacks fill you up more than fatty ones. So
don't trust your body to regulate your calorie intake: go easy on the cheesy
footballs.
Sooner or later, Christmas dinner proper will make it onto the table. And that's
where your problems really begin. For an hors d'oeuvre you are bound to be faced
with a rich little morsel-smoked salmon, pâté perhaps or something with a more
highfalutin French name, looking beautiful and dripping with cholesterol. You
would be wise to think of this as the place where art meets arteriosclerosis. The
look, the smell and that initial burst of flavour all conspire to produce the
hedonic qualities that are Yeomans's speciality. A few mouthfuls of this
pleasure-on-a-plate and, his studies show, you actually become hungrier than you
were before you began eating.
It's all going horribly wrong. And it gets worse. Whereas appetite researchers
had traditionally thought that we compensate for a calorific starter by eating
less later in the meal, that's simply not true, according to Yeomans, French and
co. They concocted some high- and low-calorie soups, and fed them to volunteers
who didn't know which was which. The volunteers were then allowed to eat as much
of a given main course as they wanted. The ones who had started with the
high-calorie soup ended up consuming around 1000 kilojoules more overall than
people given the meagre starter.
And it didn't make any difference whether the starter calories came in the form
of fats or carbohydrate. Some appetite researchers have reported that fatty foods
cause people to eat less but Yeomans suspects this effect is psychological rather
than physiological- if you know that a particular starter is destined to become
an insulating lining for your arteries you may consciously rein back during the
main course.
Anyway, enough of the starters. Let's move on to the main attraction, the grand
spread. The festive table is groaning with goodies, myriad assorted dishes making
a full-scale assault on your senses. The needle on the "hedonometer" is off the
end of the scale and you're in big trouble. Whether you are a traditionalist
content with turkey and all the trimmings, a gourmand who likes to experiment
with swans' tongues, wombats' pouches and pigs' ears, or a vegetarian happy to
graze on spicy nut loaf and assorted pulses, the key word here is "variety".
That's because variety is the source of strife. Barbara Rolls from Pennsylvania
State University has shown that people given four different types of food guzzled
60 per cent more at a sitting than those fed on a single item, even if this
single item was their favourite. Astonishingly, if you are given a mixture of
three pasta shapes you'll down 15 per cent more calories than if there was just
one shape on offer.
And when variety combines with deliciousness, the bathroom scales had better
prepare themselves for a battering. Perhaps you don't need Yeomans and French to
tell you this, but you will find your Yuletide spread more tempting than an
unlimited supply of gruel. Their experiments have confirmed the simple truth that
the yummier the food, the more we eat. Based on their premise that appetite is a
balance between pleasure and pain-between the hedonic value of the food we are
eating and the uncomfortable feelings associated with being stuffed to the
gunwales-it doesn't take a rocket scientist to figure out that you are going to
need a considerable amount of pain to outweigh the pleasures of this particular
meal.
And that's even before you have added liquid refreshment to the equation. There's
still debate about whether or not alcohol makes you fat (New Scientist, 27
November 1999, p 50), but there is no getting away from two facts: first, pure
alcohol has 29 kilojoules per gram (that's only about 8 kilojoules less than pure
fat) and second-and, perhaps, more dangerously-alcohol lowers your inhibitions.
"The jury is still out on what alcohol is doing at a metabolic and physiological
level," says French. But whether or not it makes you feel hungrier, it is bound
to summon that little inebriated voice in your head telling you to throw caution
to the wind. What the hell, the diet can wait until tomorrow.
In the meantime, there's dessert to think about. Will it be plum pudding with
lashings of brandy butter, passion fruit pavlova or the crème brûlée? All three
options are high in sugar and fat, which, research indicates, take longer than
protein to induce that fit-to-burst feeling. French thinks he knows why. "Once
nutrients are absorbed, the next place they have a big influence is in the
liver," he says. Here they are oxidised in a reaction that somehow creates
feelings of satiation. "There seems to be a hierarchy of metabolism," says
French. Proteins are broken down first, then carbohydrate and lastly fat. Which
could explain why protein fills you up faster, and fat fills you up least
quickly.
Better try a little of each dessert then. And while we're at it, pass the cheese
board. You can surely find space for a few hundred blue-veined calories-stilton
does pack them in so efficiently, after all.
At this stage you may find yourself flagging. But the Christmas dinner has
another trick up its sleeve. Coffee will shortly arrive to perk you up. We know
caffeine stimulates your central nervous system and dilates blood vessels, but
some research suggests it also increases gastric secretions. Result: a surge in
appetite in time for the chocolates.
Bloated now, you may already be vowing never to eat again. Give it a couple of
hours, though, and you'll be tucking into a mince pie or some fruit cake. If you
keep this up, your stomach will gradually expand, allowing you to shovel ever
greater quantities of food into it before stretch receptors in its walls scream
out to the brain for mercy. But the pain is worth it: once stretched, your
stomach will have extra capacity for tomorrow's Boxing Day feast.
If you really can't stomach the thought of a whole week of gorging yourself
silly, the best way to exercise self-control is probably to lock yourself away in
a cupboard with a half ration of Ready Brek. Alternatively, there's a more
scientific solution. High-fat food fed directly into the duodenum fills you up
more than the same food eaten the conventional way. French and Yeomans' work even
suggests that a blast of fat to the stomach may also do the trick. The downside
is that you'll need to be fitted with a plastic tube running through your nose,
down your throat and into you digestive tract. The prospect of sitting around the
dinner table at Christmas ingesting cheese soufflé, duck à l'orange and tiramisu
via a nasal drip is probably too gruesome for all but the most dedicated
weight-watcher to contemplate. Maybe it's best just to accept your fate. Eat,
drink and be merry, for tomorrow we diet.
Discovering the nature of party people
* 24 December 2005
SO MANY parties, so little time - so how to choose which one to grace with your
presence? Time was when there was no option but to line up the invitation cards
and pick the most promising. But that's all in the past, thanks to mobile phones.
Now you can find out what all those parties are like by calling friends on the
spot and comparing notes. After a few phone calls, the jury is in and it's time
to head for the Best Party in Town.
It sounds like the perfect solution to the party problem. But according to two
German physicists it is a recipe for disaster. In a paper about to appear in the
International Journal of Modern Physics, Steffen Trimper and Marian Brandau of
the Martin Luther University in Halle, Germany, show that mobile phones can ruin
everybody's evening.
Just ask Tobi. His little party in Berlin was going just fine until some early
arrivals rang to tell their friends what a fab time they were having. The result
was like a "nuclear chain reaction", Tobi later told the German magazine Der
Spiegel. Hordes of people from all over Berlin responded to the calls, and called
their friends as well, before heading straight for Tobi's flat. In the end, what
had been a quiet gathering became a full-on frenzy of 120 people. "It was barely
possible to control it," Tobi said. "The police came round three times."
It was Tobi's story that first got Trimper thinking about the way parties can go
wrong. "After reading the article, I spoke to my sister, and found that her
daughters had seen this phenomenon," Trimper recalls. "And so had my PhD
student." It seemed there was some genuine phenomenon at work.
And it was an intriguing one. To Trimper, who spends his time pondering the
actions of molecules in solids, the descriptions of how parties suddenly take off
sounded like a "phase change", such as when ice turns to water. Brandau,
meanwhile, saw hints of "social network" effects which arise from the way
apparent strangers often have unexpected friend-of-a-friend links. Were these
parallels a coincidence, or could the actions of party-goers be captured by some
bizarre combination of solid state physics and network theory? Trimper and
Brandau decided to investigate.
They began by constructing a mathematical model whose origins lie in a now famous
experiment conducted almost 40 years ago by the American sociologist Stanley
Milgram. He sent letters to around 300 randomly chosen people in the US,
explaining that the letters were to be forwarded on to a target person in
Massachusetts. Which sounds simple enough, except that the recipients weren't
told the address of the target: only his name, occupation and a few other
personal details. They were asked to send the letter to any acquaintance they
thought had a better chance of knowing the target. Milgram made a note of how
many re-postings were needed before the letters reached their target.
Unsurprisingly, most of the letters never arrived. But 20 per cent did - and,
astonishingly, usually after passing between just five or six intermediaries.
Milgram's discovery confirmed the suspicions of countless party-goers who find
mutual friends in common: it really is a "small world".
Network theorists have discovered that it only takes a sprinkling of random
long-range links to short-circuit an otherwise sprawling network and turn it into
a small world where everyone is connected to everyone else via just a few
intermediaries. But of course that doesn't explain how people home in on this
handful of long-range links so effectively. After all, we may know some of our
friends' friends, and even some friends of theirs, but the resulting circle of
acquaintances is hardly vast.
This part of the mystery was resolved in 2002 by a team led by sociologist Duncan
Watts at Columbia University in New York. The team pointed out something the
mathematicians had overlooked (some might say all too predictably): people aren't
just points on a network. We all have a host of different facets to our
character, from nationality and gender to occupations and interests. As such, the
notion of the "length" of social links is far richer than mere geographical
distance: people can be separated by continents, yet still have much in common.
Faced with choosing the next recipient of a letter in Milgram-style experiments,
people tend to pick friends with two or three traits in common with the target.
And Watts and his colleagues showed that this gives far more scope for hitting
those crucial random long-range links that turn big networks into small worlds.
Picky people
But they also found that another factor plays a key role: clannishness. If we
were all very picky about the company we keep - or highly "homophilic" in the
argot of social network theory - the world would be made up of isolated cliques
with nothing to say to each another. If, on the other hand, we found one another
endlessly fascinating regardless of background, the world would be one big babel.
The real world is clearly somewhere in between, and Watts and his colleagues
showed the small-world effect can survive a certain amount of clannishness. For
parties, however, Trimper and Brandau have discovered that the same effect can
spell disaster.
In trying to understand the runaway party effect, Trimper and Brandau
incorporated the theory developed by Watts and his colleagues into a computer
simulation. They created a virtual community of 1000 party-goers, whose overall
level of homophilia the researchers could vary from risibly snooty to wantonly
promiscuous. They set the homophilia level, gave all the party-goers virtual
mobile phones and packed them off to 10 virtual parties. Once at their party,
each would report back to their friends elsewhere. "We kept things very simple,"
says Trimper. "The idea was to see how many friends they knew at the party, and
if they heard of a party with more of their friends, they would leave and go to
that one."
With only one variable to control - the level of homophilia - the model was
certainly simple. Yet Trimper and Brandau found that once the homophilia reached
a critical level, the guests would suddenly start reaching for their virtual
coats. They became so picky about who they spent time with that they quit parties
with too few like-minded people and ended up at one party with all their snooty
friends. When that happened, all but one of the virtual hosts was left weeping
over their canapés.
The real surprise is that all this happens at a critical level of pickiness. "The
effect was very sudden, like a phase change," says Trimper. "We had no
expectation that so simple a model would give rise to something like this." Even
so, the pair are convinced the model's behaviour reflects a genuine effect, and
one with implications far beyond the party scene. For example, it may cast light
on how new ideas come to dominate the thinking of particular groups, such as
political factions. It also suggests ways of getting new products to dominate the
market by exploiting word-of-mouth recommendations.
The key lies in the homophilia level, which is somehow related to how many short
and long links there are in people's social networks. The exact nature of that
relationship is still unclear; Trimper is working overtime to get to grips with
all the implications of the findings. But, he points out, one implication is
already clear. "When your party guests arrive," Trimper says, "make sure you take
their mobile phones as well as their coats."
The nightmare before Christmas
* 23 December 2000
* Nicola Jones
YOU'RE NOT exactly sure how it happened, but somehow you've managed to plough
your way through three helpings of turkey, two helpings of sprouts, which you
don't even like, a whole plate of Aunt Edna's festive cheese balls and the
chimney off the gingerbread house. Like everyone else, you're slumped in your
chair with a self-satisfied grin on your face, glowing happily, drinking your
last egg-nog before bed. It's a lovely scene, but there might be something
nastier ahead of you than a few extra inches on your waistline.
We've all heard the story a thousand timeseating too much food just before bed
can give you bad dreams. Especially if it's spicy, or fermented, and definitely
if it's cheese that smells like your sock drawer. I've noticed it. My mom's
warned me about it. It's established fact, isn't it?
Well, not exactly. There is something called "The Pickled Walnut Theory", says
Tore Nielsen, a sleep researcher from the Dream and Nightmare Laboratory at the
Sacred Heart Hospital in Montreal, Canada. The theory simply says you can get
nightmares from what you eat (apparently especially if it's a pickled walnut).
But that's about it, says Nielsen, no explanation provided. "A lot of dream
experts pooh-pooh this as a kind of myth," he says. "But my opinion is that it's
very likely." And there is some evidence to back Nielsen up. Sort of.
That evidence mainly revolves around a number of neurotransmitters in the brain
that control the amount of time you spend in rapid eye movement (REM) sleep, one
of the most rejuvenating bits of our night and also the phase when you're most
likely to dream. Eating foods containing particular chemicals can bump the levels
of neurotransmitters up and down, playing havoc with dreams.
For example milk, considered by most parents and researchers to be a soporific,
contains tryptophan, an amino acid that is also used by doctors to relieve
nightmares. Tryptophan increases the brain's levels of serotonin, a
neurotransmitter that can cut down on your REM sleep. Ironically, that means warm
milk probably diminishes the amount of restful sleep you get at night, but it
also simmers down your dreamsbad or good. (What that might mean for Santa, with
the billions of milk-and-mince-pie donations, is anybody's guess.)
So it's probably not tryptophan in cheese that's responsible for its nightmarish
reputation. But it might be the tyraminea chemical that bumps up noradrenalin
levels in the brain. High noradrenalin, like serotonin, tends to be associated
with less REM sleep, and so less dreaming. But noradrenalin also makes blood
vessels constrict and blood pressure rise, and that could make the dreams you do
have racy, even nightmarish, suggests Nielsen. The more aged the cheese, or the
more rancid, the more tyramine it'll have. Ditto for overripe mandarin oranges.
And if the cranberries in the sauce have gone off, then hold on to your reindeer,
it could well be a bumpy night.
If food can be linked to bad dreams, then perhaps that even explains the
nightmarish visitations experienced by Ebenezer Scrooge on Christmas Eve. He
tucks into a late-night nosh and then sits down to a pan of gruel when his
long-dead business partner Jacob Marley, looking awfully ghost-like and making
frightening chain-scraping noises, appears to waft through the door. Scrooge, who
has perhaps read up on the effects of tyramine, proclaims wisely, "You may be an
undigested bit of beef, a blot of mustard, a crumb of cheese, a fragment of an
underdone potato. There's more of gravy than of grave about you, whatever you
are!"
The trouble is that not everyone is convinced by the possible links between food
and bad dreams. "There's no evidence that spicy food causes nightmares," says
Ernest Hartman, a psychiatrist at the sleep clinic at Newton-Wellesley Hospital
in Newton, Massachusetts, and arguably the world expert on nightmares. The whole
thing about cheese, as far as he's concerned, is a myth.
But maybe the explanation isn't so chemically complicated. Maybe it's just that
cheese, like most dairy products, is notoriously difficult to digest, suggests
Rafael Cabeza, a neuropharmacologist from the University of Texas at El Paso. Get
a tummy full of it, and you may spend the night tossing and turning. The more
often you wake up, the more likely it is that your dreams are interrupted and so
you remember them. If they are bad dreams that can leave you with the impression
of a night plagued by nightmares.
Apart from pungent cheese, a bellyful of Christmas cheer could also trigger a
nightmare or two. Take mulled wine. Aside from the double dose of tyramine you'll
get from the alcohol and the fermenting oranges, there's more trouble brewing. Go
to bed the worse for wear, and you'll initially dream less because alcohol
suppresses REM sleep. Once that effect wears off, usually around the early hours
of the morning, your brain "rebounds" and crams as much REM sleep into as short a
time as possible. Your dreams get more vivid, sometimes even frightening. It's
like someone shouting in your ear when you expect them to whisper, says Nielsen.
Things get worse if you're trying to go cold-turkey on cigarettes and have a
nicotine patch or two stuck to your tummy. The patch increases levels of
dopamine, another neurotransmitter, which has been tentatively linked to
increasing REM sleep. People who use patches often complain of nightmares. And if
you're doped up on beta-blockers for your high blood pressure that could cause
trouble too. These drugs initially increase noradrenalin, suppressing REM sleep.
But just as with booze, you may get a rebound effect and an onslaught of
early-morning dreaming.
Then there's the issue of just how you fall into bed after the season's
festivities. "The way we sleep, the postures we assume, even the way we touch our
spouse, that affects our dreams," says Nielsen. Hartman says that his patients
seem to complain more of nightmares when they sleep on their backs, although he
doesn't know why this might be so. The Netherlanders of the Middle Ages, on the
other hand, were apparently so convinced of the importance of posture that they
slept in cupboard-like vertical spaces called "box beds" to stop the bad dreams
triggered, they believed, by their diet rich in salted fish.
Today the jury is out on whether food, including salted fish and Christmas
binges, can really cause nightmares. But we could soon know the truth now that
Nielsen's on the case. "It would be an interesting research project," he muses.
"You could probably get a pizza company to sponsor you..."
Savour the festive flavour
* 24 December 2005
* Caroline Williams
YOU either love them or hate them. Nothing divides opinion round the Christmas
dinner table more than Brussels sprouts. If you ever have the urge to find out
what gives sprouts their distinctive taste, rest assured that food scientists
will be able to tell you.
Besides identifying flavour molecules, researchers have spent decades coming up
with all manner of methods and equations to explain the way food and drinks
release their flavours, a vital part of how they taste.
But for all their work, they are easily stumped. Ask the same food scientists to
analyse the wine, sherry and brandy you might wash your dinner down with, and
you'll have trouble getting an answer. For mysterious reasons, when it comes to
explaining taste, booze just hasn't succumbed to analysis like other foodstuffs,
liquid or otherwise.
At last, however, improved techniques may be bringing us closer to understanding
how alcoholic drinks tickle our taste buds. And along the way we may get answers
to fundamental questions, such as: does the shape of a wine glass make a
difference; does warming a brandy glass improve the flavour; and does it really
matter whether a cocktail is shaken or stirred?
Our perception of flavour is linked to the levels of aromatic compounds that are
released when we eat or drink. Most of what we think of as taste actually comes
from our sense of smell, courtesy of the olfactory receptors in the roof of the
nose. So measuring aroma release is important in deciphering not only flavour but
our whole experience of whether or not we like a food. It is vital for the "nose"
of a wine or spirit, which makes the difference between a satisfying draught and
a disappointing sniff. But until recently, no one had found a way to measure
aroma release from alcoholic drinks in a realistic way.
Aroma release is traditionally measured by placing a sample of a drink in a
sealed container and then comparing the levels of aromatic compounds in the
liquid versus the surrounding air. But flavour researcher Andy Taylor of the
University of Nottingham, UK, thinks that this method is far too crude: while it
gives an idea of what is going on before a bottle is uncorked, it bears no
relation to our actual experience of a good wine or whisky. "You cannot explain
the dynamics of flavour in a sealed container," says Taylor.
What is needed instead is a technique that can measure aromas as they are
released. So Taylor and his student Maroussa Tsachaki set out to mimic what
happens in the glass by wafting air over alcoholic solutions and measuring the
concentrations of flavour compounds coming off the drink. Using this technique,
they are confident that they can sniff out some answers.
Experiments on sealed samples have already revealed differences between how
alcoholic and soft drinks release aromas. Aroma compounds tend to diffuse out of
a water-based solution more readily than from a solution containing alcohol. Many
aromatic chemicals are hydrophobic, so alcoholic solutions dissolve them more
readily than plain water, "locking" the aromas in the solution. As a result,
there is generally more aroma in the air above a water-based solution than an
alcoholic one of the same concentration.
But while sealed jars are all very well, is this the same as what happens in real
life? When Taylor's team blew air over a water-based solution, they found that
the release of aromas dropped off as the top layer of the solution became
depleted. This is no surprise: after all, freshly made orange drink smells
stronger than a glass that has been standing around all day. Taylor expected to
see a similar drop-off with alcohol. But when the team repeated the experiment
with an alcoholic solution, the numbers didn't seem to add up.
For some reason, alcohol kept giving off aromas for far longer than water-based
drinks. His team repeated the experiment three times to check the results.
"Something about the alcohol keeps aroma levels in air high," he says. "I
couldn't explain it. It's counter-intuitive."
Understanding how alcohol keeps flavours ticking over could help improve the
flavour of your favourite tipple, allowing manufacturers to engineer a great
tasting nose in an otherwise ordinary bottle of plonk. But as yet, no one knows
what causes the effect.
One idea is that it is down to spontaneous convection currents developing as the
drink breathes. "In a solution of alcohol, the ethanol starts to evaporate when
it comes into contact with air," says Taylor. He speculates that in solutions
over 12 per cent alcohol, the rate of ethanol evaporation at the surface is
enough to cool this layer, causing it to sink down the sides of the glass. This
pushes warmer liquid at the bottom up to the surface, creating a self-stirring
effect. It could explain Taylor's results. An alcoholic drink left to self-stir
would carry on releasing aromas into the air, long after a comparable water-based
solution had lost aroma compounds from the top layer. In water, the only way to
encourage more aromas out of solution is to stir it.
Another explanation is that the structure and behaviour of ethanol molecules
helps the aroma compounds diffuse through the solution to the surface and so
escape. As yet, there is no evidence to confirm or refute either of these
theories, but physical chemist Colin Bain from the University of Durham, UK, is
putting his money on convection currents. "They are not a new concept in physical
chemistry, but maybe flavour researchers have never thought about them before,"
he says. You can see them in action by pouring a thin layer of cream on top of a
liqueur such as Tia Maria. After a few seconds, the surface of the cream starts
to break up into roiling convection cells (The Last Word, New Scientist, 25
January 2003). "If you cover the glass with a plate and turn off evaporation, the
current stops," says Bain.
In reality, he says, there are very likely two sets of circulating currents - one
in the body of the liquid and another caused by surface tension pulling liquid up
the wall of the glass. As the liquid climbs, alcohol evaporates out, which
increases the surface tension and ensures more liquid is pulled up. At a certain
height the solution starts flowing back down the sides in "fingers" or "tears".
You can see this, Bain says, if you blow gently onto a glass of whisky. This
increases the rate of evaporation and causes more fingers to flow down the sides.
But before any of this research can lead to the perfect drink, there's plenty
more work left to do. If convection currents really are driving flavour release,
for example, the shape of the glass could be a vital part of the aroma
experience. Warming and swilling the glass may affect the currents, speeding or
slowing evaporation. And since all this happens before the glass has even touched
our lips, the all-important next step will be to measure flavour compounds as the
drink enters your mouth, throwing all manner of aromas up the back of the throat
and into the nose.
Now all Taylor has to do is find a graduate student dedicated enough to spend
three years of their life drinking wine. Any volunteers?
Scary spice
* 23 December 2000
* Kathryn Brown
DECK the halls, jingle the bells, and raise a holiday toast with a glass of
egg-nogtopped with its traditional dusting of hallucinogen. No, not the booze.
Nutmeg. That fragrant spice in your kitchen cabinet has a hidden sideand, when
consumed in high doses, a mind-bending bang powerful enough to melt your granny's
muffins.
How can this be? When chefs describe nutmeg, they use terms like "warm," "sweet"
and "full-bodied". Physicians have their labels, too: "delusional", for instance,
and "psychotic". Both camps are accurate. A sprinkle of nutmeg is bitter-cinnamon
delight. But a few teaspoons of the stuff can poison you, because nutmeg contains
compounds that carry an intenseand rather unpleasanthallucinogenic high.
"Nutmeg contains a volatile oil," explains David Seigler, a plant biologist at
the University of Illinois in Urbana-Champaign. And that oil includes compounds
such as myristicin and elemicin. In our bodies, some researchers suggest, these
two compounds break down into MMDA and TMA, psychoactive substances that send a
drug-like kick to the brain. People who swallow enough nutmegabout 2 tablespoons
of the ground spice, the equivalent of perhaps a single nutmeg nutcan suffer
hallucinations, nausea and heart palpitations a few hours after indulging.
That's quite a potent punch from what is, after all, only the seed of an
evergreen tropical tree. Native to the East Indies, nutmeg trees now flourish in
the Caribbean, Brazil, India and Sri Lanka as well. The outer flesh of the nutmeg
fruit can be eaten as is, or preserved like candy. Inside sits the nutmeg seedbut
not alone. A ruby-red membrane, called an aril, coils around the pit, and is the
source of another seasonal spice: mace. The nutmeg tree has the distinction of
yielding two quite separate spices.
Four centuries ago, the only nutmeg trees to be found fringed Run Island in the
Banda Sea, in what is now eastern Indonesia. At the time, nutmeg was rumoured to
cure various ills, including the plague that was then sweeping across Asia and
Europe. Eager for control of this precious resource, the British and Dutch waged
war.
Even back then, thrill seekers knew nutmeg's secret kick, and more than a few on
both sides reportedly grew addicted. According to one account, Charles Sackville,
the sixth Earl of Dorset, regularly choked down spoonfuls of the spice, and was
once imprisoned after an evening of nutmeg frenzy for "running up and down all
night almost naked through the street".
More recently, during the psychedelic 60s, sensation seekers turned to nutmeg as
a cheap alternative to more conventional hallucinogens. One of Seigler's friends
spent several days in the hospital recovering from a severe nutmeg experience.
"He was at a boys' boarding school," Seigler says, "and they couldn't lay their
hands on the standard drugs of the day." In prisons too, nutmeg was among the
accessible routes to chemically altered reality. The black activist Malcolm X
sampled the spice in a Boston jail. Jazz musician Charlie Parker reportedly
partook as well, washing his down with cola.
Despite its fragrance, nutmeg is no sweet high. Just ask emergency room physician
Lance Becker of the University of Chicago. Becker vividly recalls an evening some
eight years ago when a 23-year-old college student stumbled in wailing: "I'm
going to die, I'm going to die." The student had smashed a nutmeg seed and
swallowed about a quarter of it. By the time he got to the ER he was sweating
profusely, with pounding heart and skyrocketing blood pressure. The hospital
admitted him for the couple of days it took for his symptoms to subside. Nutmeg
is called the "spice of madness" for good reason, says Becker."This is not
exactly a happy trip."
Indeed, reports of nutmeg intoxicationincluding at least one deathcontinue to
crop up sporadically in the medical literature. In 1998, researchers in Ireland
and Norway published two case studies. Five years earlier, doctors at Gordon
Hospital in central London described an unfortunate 25-year-old man who had
reportedly gobbled down just half a gram of nutmeg and needed tranquillisers to
calm his frazzled nervous system. Reports like these suggest that nutmeg is
usually a one-time high, notes Becker. "I doubt there are many people who do this
more than once," he says.
Not for sheer pleasure, anyway. But nutmeg is also a popular ingredient in folk
medicine. In China, people take it to calm an upset stomach or relieve
rheumatism. South-east Asian villagers dine on rice cooked with nutmeg seeds as a
remedy for dysentery, anorexia and colic. Elsewhere, hopefuls have swallowed
nutmeg to boost libido. And in the early 1990s, researchers even found evidence
that myristicinfound in parsley and carrots as well as nutmeginhibits lung
tumours in lab mice.
Most of us, though, restrict our use of nutmeg to the kitchen. If you have a
taste for nutmeg, go ahead and sprinkle it on your holiday feast. Egg-nog,
pumpkin pie and bread pudding, for instance, all beg for a little spicing up. "If
you have a reasonable diet and take in normal amounts of nutmeg, the spice
probably won't affect you at all," says Mark Kantor, a nutrition specialist at
the University of Maryland in College Park. "Remember that almost anything can be
toxic if you consume too much of it." Do store your nutmeg far from the reach of
curious children, though. "Kids will swallow anything," warns Becker.
Perhaps that classic kitchen tome, The Joy of Cooking, says it best: "Use it
sparinglybut often."
What makes a Turkey the right stuff?
* 19 December 1998
* Rosie Mestel
HERE'S something not to think about as you tuck into your holiday fare. A hulking
turkey tom, too massive to enjoy a more natural experience, is having his abdomen
expertly massaged. He soon gives up his prize: a small sample of milky-grey
semen, which is added to a pool of similar offerings from other breeder toms and
taken to the long row of turkey hens. Each hen is deftly upended. In goes the
semen. Out, rather later, come eggs, which duly make chicks and eventually the
scrumptious, sizzling slices you're about to douse in gravy and spear onto your
fork.
The wild turkey is a fleet-footed, slimline forest creature that passes its life
gobbling (and also "yelping", "putting" and "purring", for those who thought
"Gobble!" was all turkeys said), roosting in trees, grubbing for acorns and
beetles, and occasionally attacking rural postal workers. Its black, brown and
cream feathers afford it good camouflage. Its reproductive output is modest-just
12 eggs each spring (12 more, perhaps, if it loses the first clutch). A
full-grown male weighs 10 kilograms at most. Ample, but hardly ostentatious. As
for collecting semen: go ahead, just try it.
Compare that with man's creation-the snow-white, 30-kilogram domestic turkey tom,
heaving his ballast of snow-white breast meat before him as he waddles about as
best he can. Or the domestic turkey hen-slimmer, yes, but able to lay a cool 120
eggs in a 27-week reproductive marathon. How did this strange bird come to be,
and where is modern science taking it?
The turkey's origins are shadowy. Centuries ago, Native Americans domesticated
it. The Spaniards took it to Europe. Settlers brought it back to America again.
Despite this convoluted history, it was not until the 1950s that the birds were
bred for ivory feathers (Western consumers prefer a breast devoid of black,
hairy, down remnants), and even more recently that serious breeding for bulk
began.
Unwitting selection
There was a time when breeding focused on size and speedy development, and
precious little on the growth of the bones that support all that heft, resulting
in bow-legged birds that were barely able to walk. But Karl Nestor, a University
of Wisconsin turkey geneticist with 38 years of breeding under his belt, showed
it didn't have to be that way. Nestor selected not just for bulk but for wide,
sturdy leg bones and walking ability, measured somewhat subjectively on a scale
of 1 to 5. Professional breeders have done likewise, and today's turkeys, though
hardly graceful, have a better gait than their forebears.
Classical breeding requires that in each generation you select the creatures with
the most desirable characteristics to produce the next generation. You don't need
to know anything about the genes you're selecting, or the physiology that you're
changing. So does anyone know why turkeys now grow so big?
The best insights come from chickens, not turkeys, but the principles are
probably the same. Evolutionary biologist Jared Diamond of the University of
California in Los Angeles and his colleague Sue Jackson were so interested in
knowing how the broiler chicken developed, they spent long hours weighing and
measuring guts and other body parts, and compared these measures with those of
the chicken's ancestor, the svelte, fleet-of-wing wild jungle fowl.
The brain, they found, is smaller in the broiler. It makes sense. You don't need
to be astute and alert if you're cooped up in a pen all your life, and brains are
energetically expensive. Legs are thinner and lighter in the broiler, too, which
also makes sense. Sturdy legs aren't important if you're not doing much moving.
Thus, without knowing what they were doing, breeders selecting for bulk chose
animals in which energy was shunted away from "unimportant" body parts towards
"important" ones-namely, the meat.
And that's not all. Broilers consume lots more feed-there's a good chance that
greediness has been inadvertently selected for. The guts have risen to this
challenge. Gram for gram, the broiler's guts absorb nutrients such as glucose and
amino acids less efficiently, not more. But the bird still absorbs food more
effectively, as its small intestine is nearly three times more massive than that
of the jungle fowl. Selecting for bulk, breeders unwittingly selected for big,
fat digestive organs.
Like chickens, domestic turkeys have smaller brains than their wild relatives;
these are, after all, creatures that can drown themselves by staring up too long
at the rain. And their guts are more massive, says James Croom of North Carolina
State University in Raleigh. Still, turkeys aren't really like chickens: they
haven't been intensively bred for as long, so they retain more of their wild
habits. They herd. They gobble. And turkey hens, unlike commercial egg-laying
chickens, go broody.
"Broody" means that mothers become motherly, a real headache for breeders. It
isn't merely that the hen will hiss and peck when anyone tries to take her eggs.
Her ovaries can regress and she'll stop laying altogether. Small-scale farmers
nipped broodiness in the bud by putting problem hens in rooms filled with rocks,
or out in the cold-anything to help them forget the nest. Try paying that kind of
attention to a modern-day flock of 25 000.
Luckily, endocrinologist Mohamed El Halawani of the University of Minnesota in St
Paul has come up with a novel tool: an anti-broodiness vaccine.
Endless tricks
His strategy is clever but logical. Mothering behaviour is promoted by the
hormone prolactin, made in the pituitary gland when the turkey hen touches her
eggs. Stop prolactin release, reasoned El Halawani, and mothering behaviour would
be prevented too. He achieved this by injecting hens, a few weeks before laying,
with another brain protein called vasoactive intestinal peptide, needed to
trigger prolactin production. The birds make antibodies to this VIP, and these
antibodies, when bound to the bird's own VIP, inactivate it. Thus, no
prolactin-and no broodiness. The hens just keep laying and laying and laying.
Efforts, meanwhile, are being made to ensure that every turkey tom who gives of
his semen gets a fair crack at contributing to the next generation. The problem
with pooling turkey ejaculate is that some toms, no matter how wondrous their
traits, rarely fertilise an egg. Sperm from certain super-males wins out almost
every time. Today, with the help of a turkey sperm motility test, breeders can
tell just which bird's sperm does what. Toms with super-fast sperm can be
identified, and toms with wonderful traits but wimpy sperm can be given more
exclusive treatment.
There's no end to the tricks that scientists are trying. Breeding continues, for
bulk and fecundity and also for such qualities as better feed conversion and
disease resistance. Today's birds are less likely to make you sick, because they
can be sprayed with harmless bacteria that take up residence in their gut,
inhibiting growth of Salmonella, and helping to prevent food poisoning. And there
are edible films that can be sprayed on the carcass to kill such nasty bugs.
So Merry Christmas! Tuck in! As those in the business say, "May 1999 bring
prosperity to you and the turkey industry."
Undercooked turkeys can harbour superbugs
* 17:11 21 December 2004
* Andy Coghlan
An in-depth analysis of bacteria in US turkeys has revealed that high proportions
of bacteria found in the birds are "superbugs", resistant to many of the
antibiotics used on farms and to treat people.
The study sampled over 1000 turkey carcasses from two undisclosed
turkey-processing plants in the US Midwest. Of these, 94 birds "were found to
contain strains of both Campylobacter and Salmonella", says Catherine Logue, head
of the team at North Dakota State University in Fargo, US, which conducted the
study.
It is well established that commercial poultry - including turkeys - can contain
bacteria that cause serious gastrointestinal upsets if it is not cooked properly.
But this latest finding raises the possibility that antibiotic-resistant bacteria
might find their way from turkeys into the human food chain, and possibly into
hospitals.
Each year, Campylobacter and Salmonella make 2 to 4 million US citizens ill, and
could prove much more difficult to treat if they become resistant to clinical
antibiotics, such as erythromycin, ciprofloxacin, gentamicin and tetracycline.
Gene scavenging
Of the Salmonella samples grown from the infected birds, many were resistant to
several antibiotics - 88% of Salmonella samples from one plant were resistant to
tetracycline, and 35% from the other. Around 45% of the samples from one plant
were simultaneously resistant to four antibiotics.
Logue says that resistance in Salmonella may be so abundant because 68% of the
strains her team grew had genes for making class I integrase. This enzyme enables
bacteria to scavenge "cassettes" of genes that confer resistance to antibiotics,
either from the environment or from other bacteria.
Of the Campylobacter samples, 58% from one processing-plant were resistant to at
least one antibiotic, while more than 10% of samples from the other plant were
resistant to no less than 8 antimicrobials.
Although no Campylobacter had the class I integrase gene, more than a third had
"efflux pump" genes which enable bacterial cells to survive by ejecting
antibiotics.
Faster fattening
Logue says that the scale of the risks posed by resistant bacteria in turkeys is
difficult to assess. In a previous study by her group published in 2003, she
found that around 17% of processed birds were infected with Salmonella, while a
parallel study found that 35% of birds carried Campylobacter.
Antibiotics have been routinely given to turkeys to fatten them up faster and
keep them healthy. But this practice pushes the bacteria to evolve resistance to
the farmyard antibiotics, and also to related drugs used in human medicine.
Europe banned a group of antibiotic growth promoters a decade ago to try to curb
the rise of resistance. The US Food and Drug Administration is worried too, and
in March 2004 upheld a 2000 decision to stop farmers giving poultry enrofloxicin,
an antibiotic similar to the medically important fluoroquinolones.
Whatever the risk that resistant bacteria will spread from turkey farms to people
to hospitals, Logue says that turkey is safe to eat provided it is thoroughly
cooked. "Just make sure it's thoroughly de-frosted, and that you cook it right
through, all the way to the core," she says.
Journal reference: Food Microbiology (vol 21, p779)
Related Articles
* Antibiotic-boosting drug kills superbugs
* http://www.newscientist.com/article.ns?id=dn6522
* 15 October 2004
* Resistance DNA in antibiotics
* http://www.newscientist.com/article.ns?id=mg18224420.300
* 10 April 2004
* March of the superbugs
* http://www.newscientist.com/article.ns?id=mg17924046.600
* 19 July 2003
Weblinks
* Catherine Logue, North Dakota State University
* http://www.ndsu.nodak.edu/instruct/nolan/cmbid/cathy.htm
* US Food and Drug Administration
* http://www.fda.gov/
* Food Microbiology
* http://www.ingentaconnect.com/content/ap/fd;jsessionid=ijiywta4jtq.henrietta?
Drug brings relief to big spenders
* 12 November 1994
* ROSIE MESTEL
IN the weeks before Christmas, millions of people around the world will be caught
up in an orgy of spending. For most of us, the madness is only seasonal, but for
some unfortunates, the obsessive urge to shop lasts all year long. Now, say
American researchers, there may be drugs that can cure compulsive shoppers of
their incessant need to spend.
Donald Black, a psychiatrist at the University of Iowa College of Medicine, and
Susan McElroy, psychiatrist at the University of Cincinnati, have both conducted
pilot studies with compulsive shoppers - people who cannot stop shopping, even
though they know that their behaviour is causing serious problems.
Such people routinely spend the bulk of their pay cheque on personal items, and
spend hours each day planning their next trip to the shops. They are often in
debt for thousands of dollars, frequently write cheques that bounce, and exceed
credit limits on multiple credit cards. They may even be forced into bankruptcy.
"People sort of joke about it, but the problem is really extremely disruptive,"
says McElroy.
Compulsive shopping is probably closest in nature to a series of psychiatric
complaints known as impulse control disorders, which include uncontrollable urges
to light fires, steal or pull out one's hair. But it also resembles obsessive
compulsive disorder (OCD), a strange complaint that causes sufferers endlessly to
repeat pointless tasks like washing their hands, or to hoard obsessively.
The similarity to OCD led Black to test the drug fluvoxamine on compulsive
shoppers. Fluvoxamine is already being used to treat people with depression in
Britain, and is awaiting approval by the Food and Drug Administration for
treatment of OCD in the US. In Black's study, patients take the drug for eight
weeks, and the effect on their shopping urges is monitored. Then the patients are
taken off the drug and watched for another month.
In the seven patients examined so far, the results are clear and dramatic, says
Black: the urge to shop and the time spent shopping decrease markedly. When the
patient stops taking the drug, however, the symptoms slowly return. "The results
are exceptional," says Black. "I think the drug has true promise."
Fluvoxamine is not the only drug that could help out-of-control shoppers. In a
study of the medical histories of 20 compulsive shoppers, McElroy and her
colleagues found that antidepressant drugs such as fluoxetine (Prozac) and
sertraline (Zoloft), used to treat both depression and OCD, seem to help
compulsive shoppers.
The drugs in McElroy's study group were originally taken for depression, which
often afflicts compulsive shoppers. But 9 out of 13 shoppers reported that their
urge to buy also diminished while on medication.
Both Black and McElroy point out that their findings are only preliminary, and
that larger trials are needed before they can draw any firm conclusions. They are
both planning such studies.
And even though some estimates suggest that between 1 and 6 per cent of the US
population may have shopping problems, that does not mean that 15 million
Americans should be dosed with drugs to cut down on their spending sprees, says
Black. "l think that the number of people needing medication would be tiny," he
says.
Christmas trees provide pollution solution
* 24 December 1994
* David Bradley
FOR many, pine needles under the Christmas tree are the curse of the holiday
season. But Swedish chemists have turned a yuletide nuisance into an
all-year-round blessing.
Henrik Kylin and his colleagues at Stockholm University have found that pine
needles can be used to detect as maintenance-free sensors of pollutants in the
environment, such as chlorine-containing pesticides and polychlorinated biphenyls
(PCBs). The chemists hope to use pine needles to draw up a pollution map for
Europe.
The idea of using pine needles to detect pollution isn't new. It was proposed in
New Scientist in 1966, the year the magazine first reported that PCBs were a
potential environmental hazard. However, before the technique would become viable
analytical chemistry had to catch up.
The protective waxy surface of many leaves absorbs traces of organic, fat-soluble
compounds from the air. According to Kylin, finding pollutants on such leaves in
trees in remote areas show that organic compounds can travel through the air over
large distances (Airborne Lipophilic Compounds in Pine Needles, Stockholm
University).
The team began drawing its pollution map by collecting pine needles from Scots
pine (Pinus sylvestris) in western and northern Europe. The researchers took
samples from trees that were at least 20 kilometres from any city or industrial
area and at least 2 kilometres from any road. Needles normally grow for three
years and Kylin's team divided them into classes by year.
There are several techniques for detecting PCBs in needles but impurities tend to
obsure the results. To overcome this problem the team dissolved the needles' wax
coating and carried out a rough separation to produce a solution containing all
the wax compounds. They cleaned up the mixture using high-performance liquid
chromatography (HPLC). They pumped the solution through a cylinder packed with a
material that attracts the impurities but lets the PCB molecules through. By
carefully choosing this material the researchers removed the organic impurities.
Next, Kylin and his colleagues used gas chromatography to measure the precise
concentrations of PCBs. They heated the sample and separated different compounds
in a similar way to HPLC. From the position and size of each peak on a
"chromatogram" they could work out the identity and quantity of each PCB.
Kylin and his colleagues say this is a simple and effective way of mapping
airborne PCBs and identifying very polluted areas in Europe. However, such a map
will not provide absolute concentrations of pollutants in the air at any one
time. Instead, it will show deposition over a length of time.
How to maximise your Christmas presents
* 25 December 2004
* Emma Young
IT'S the countdown to Christmas, and if your tree isn't already surrounded by a
stack of bumper-sized gifts bearing your name, now is the time to take action.
But to ensure you get the best ever present this year, first you'll need some
help working out who to target with your charm - and your wish-list.
The right choice isn't always as obvious as it might seem. Grandparents are
usually a good bet, but the richest of them won't necessarily be the most
forthcoming because there's a fair chance they got that way thanks to their
Scrooge-like qualities. So if personal wealth isn't the ideal indicator of
gift-giving potential, what is? The key, it turns out, is to identify the
grandparent who has the most certain, and most exclusive, genetic link to you.
And before you say, "well, surely I am equally related to all my grandparents",
remember this chilling statistic: an estimated 10 to 15 per cent of children are
not fathered by the man whose name appears on their birth certificate.
All of which goes to explain some intriguing findings due for publication early
next year. A team led by Bill von Hippel at the University of New South Wales in
Sydney, Australia, discovered variations in emotional closeness between
grandchildren and grandparents, which, they argue, has a biological rather than a
social explanation. Maternal grandmothers emerged as having the closest
relationship with their grandchildren, followed by maternal grandfathers then
paternal grandmothers and finally paternal grandfathers.
The uncertainty principle
"A woman always knows that a child is her own, but a man has some uncertainty
about his paternity, and for grandparents the issue is compounded," says von
Hippel. The pattern that emerged reflects the degree of uncertainty involved. But
even the researchers were surprised that this showed up so clearly in the study.
"There are so many reasons to feel close or not close to a grandparent - like
health, distance, cultural differences, personality, and relationships between
the parent and the grandparent," adds von Hippel.
On the basis of this study, at least, your maternal grandmother looks like the
softest touch for that Christmas gift. And other research supports this. In a
study accepted for publication by the journal Human Nature, Todd DeKay of
Albright College in Reading, Pennsylvania, and Rick Michalski of Hollins
University in Virginia surveyed more than 200 grandparents living in retirement
communities in south Florida. "We found that, yes, grandmothers invest more in
grandchildren through daughters than through sons," Michalski says. In this
particular instance, they rated investment according to emotional closeness, the
time spent per week with a grandchild, and the money spent on the child every
month. But earlier work by DeKay is even more telling: he found that maternal
grandmothers do indeed give bigger presents to grandchildren than do paternal
grandfathers.
Case closed? Well, not quite. Before you direct all your attentions at your
maternal grandmother, you should probably consider your individual circumstances.
Von Hippel's work shows that if your paternal grandma has no grandchildren
through daughters, she is likely to feel as predisposed to you as is your
maternal grandfather. OK, so that's not up there with maternal granny, but if you
have lots of cousins on your mother's side of the family and few on your
father's, his mother is likely to give more to you. "Grandparents must spread
their time and resources across grandchildren," says von Hippel. So your paternal
granny might be the best target if she happens to be joining you for Christmas
and so perhaps feels more obliged to bring an impressive gift.
Of course, circumstances may dictate that granny is no go. You may, for example,
have upset her by pointing out some of this research and demanding a Lamborghini
as your genetic right. If so, you may have no choice but to butter up a grandpa.
But remember, your father's father will be the toughest challenge.
In this endeavour, you might think it wise to stress your similarities. If your
grandfather is nasally well-endowed and a gifted artist, now could be the time to
make the most of your own large nose and propensity to doodle. But don't count on
it, because the scientific results are not clear. "There is an earlier study that
found an effect of similarity, and we predicted that paternal grandfathers would
bias investment towards more similar grandchildren," says Michalski. "In fact we
found that maternal grandmothers bias their investment most based on similarity.
That was a quirk that we didn't expect to find."
You may be thinking, these days there is no need to suffer the effects of doubt
over paternity. But arranging DNA tests for your father, grandfather and yourself
is perhaps going a little too far. Besides, it is a very risky strategy. David
Bishai at Johns Hopkins University in Baltimore, Maryland, is investigating what
happens to grandparent-grandchild relationships following paternity tests ordered
by Maryland courts. The results of the study will not be in for a few months, but
it is already clear that when paternity is disproved, the non-biological
father/child relationship can become very sticky.
Perhaps best then to stick to grandmas unless absolutely necessary. In which
case, your main problem will be deciding what sort of present to try for. Here,
you will do best to consider the evolutionary significance of post-menopausal
women. Luckily, Virpi Lummaa and Mirkka Lahdenperä of the University of
Sheffield, UK, can help. In a paper published in March, they describe a study of
almost 3000 women living in Finland and Canada in the 18th and 19th centuries,
showing that the longer a woman lived after the end of her reproductive years,
the more successfully her children reproduced. On average, women gained two extra
grandchildren for every 10 years of life after menopause (Nature, vol 428, p
178).
Speculate to accumulate
So, women live far beyond menopause to offer child-care help and support in a bid
to forward more of their genes to the next generation. But of course granny's
desire for genetic propagation does not stop with you. What she really wants is
to become a great-grandmother, as many times as possible. Which means that to
secure the best possible Christmas gift, you should explore the frontier where
her fundamental desires coincide with yours.
Von Hippel offers the following advice, with a disclaimer that it's not strictly
based on scientific findings: "The next step would be to emphasise the gift that
will increase your own chances of having lots of offspring," he says. "Gifts that
help you attract or keep the ideal mate, or gifts that help you raise a lot of
kids, ought to be the best bet." Lummaa agrees: "At least that sort of present
should please the granny most," she says.
A new computer probably won't pass muster unless you are single and you really
can convince granny of your intention to join an internet dating service. But she
just might be willing to splash out on expensive perfume, designer clothes or -
if she's astonishingly wealthy - even that Lamborghini. As the research shows,
all gran really needs is the right encouragement. Ask for a flashy gift that will
impress the opposite sex and you can tell yourself you are not being selfish this
Christmas - you're just helping your nearest and dearest to get her own heart's
desire.
E-gift vouchers: Whose money is it anyway?
* 24 December 2005
* Dana Mackenzie
WHAT a lovely gift. Not for you, of course - you don't really want to venture
inside the local Acme tattoo and piercing parlour, let alone make use of its
services. But because you are never going to use it, Uncle Derek's desperate
last-minute purchase, the prepaid electronic gift card entitling you to an Acme
shoulder snake or tongue stud, is a great gift to the store: free money.
Gift vouchers - the low-tech, paper version of the gift card - have always been a
boon to retailers. We mutter thanks to whoever bought them, surreptitiously try
to find someone willing to swap them for cash and, having failed, stick them in
the back of our wallet, from where - all too often - they never emerge. If they
are issued with an expiry date, so much the better for the retailer: then they
know exactly when your grandmother's money is theirs to keep.
Somehow, the disappearance of this cash into retailers' pockets seems innocuous,
our own fault. It's practically a holiday tradition. But with the growth of
electronic gift cards, the cash is disappearing faster than ever - and creating a
legal headache. Imagine presenting your paper voucher to a retailer and being
told the face value has been depleted by a "service charge". Or that the voucher
is now worthless because it has a hidden, electronically encoded expiry date that
Grandma Rose forgot to tell you about. Raise a glass to progress: walking away
with your money is so much easier when the cash is digital.
Once a sort of holiday afterthought, pre-paid electronic gift cards are now
everywhere. According to TowerGroup, a Massachusetts consulting firm, American
consumers are expected to spend $55 billion on gift cards this year. On the
European side of the Atlantic, gift cards have been slower to get started, but
they are on their way. One of the first to adopt them in the UK was the
department store Harrods, which introduced the cards in November 2004. Already,
Harrods sells twice as many gift cards as traditional paper vouchers. "People
seem to spend more money on the cards than on the vouchers," says Harrods
spokeswoman Valentine Labriffe.
There is good reason for that. A card fits nicely in your wallet and doesn't get
torn or bent. It is a more tasteful present than cash, and somehow more
substantial than paper vouchers. Like postage stamps, gift cards with attractive
designs or portraits of your favourite singer are becoming collectables.
Gift cards offer benefits for merchants too. For a start, they can levy a service
charge. In the US, some card issuers are charging fees on cards that go unused
for several months. This practice already has consumers and their advocates
crying foul. "When I talk with people about it, they say, 'This is stealing!'"
says Dan Horne, a professor of marketing and "gift-card guru" at Providence
College in Rhode Island. "People are very surprised to find out that the issuers
can get away with it."
And then there's the not-so-obvious expiry date. While paper vouchers with an
expiry date have it printed or written on them, plastic gift cards don't. It's
usually in the terms and conditions, which may only be available on the seller's
website.
Up to 10 per cent of the funds on gift cards may vanish into the store's coffers.
"It depends on the category of merchant," Horne says. "For Macy's, it's less than
5 per cent, for a grocery store it might be 2 per cent. For a specialty store, a
tattoo studio for instance, it may be 10 per cent." Whatever the percentage, this
"breakage" amounts to free money for the retailer. Consumer complaints have led
several US states to ban or restrict expiry dates and service fees. The first
such law was passed in California, which banned expiry dates on gift vouchers in
1996, when cards were still just a blip in the market. The state then banned
service fees on gift cards in 2004, with one very limited exception: cards that
have been inactive for 24 months, with a balance of $5 or less, may be assessed a
$1 monthly fee.
But there are still huge gaps in the laws concerning fees and expiry dates. Gail
Hillebrand, an attorney for Consumers Union in California, says that 32 states
still have no legislation at all. The federal government has shown very little
inclination to act. In 2004, New York congressman Chuck Schumer introduced a bill
in the House of Representatives modelled after California's law, but it went
nowhere. Some companies are making a pre-emptive strike against the bad publicity
gift cards have already stirred up. Sears, for instance, eliminated expiry dates
on its gift cards in December 2003.
In the UK, the gift card phenomenon is about seven years behind the growth curve
in the US. The UK's Office of Fair Trading says that although it has so far
received few complaints about unfair charges or unexpected expiry, there are no
regulations over service fees and expiry dates yet. The WH Smith gift card, for
example, does not have an expiry date, but the Harrods card does, although it
only expires after two years with no activity (even a balance query counts as
activity), and Harrods will replace expired cards anyway. The only way you can
lose your money, as with cash or paper vouchers, is to lose the card.
Not everyone is so accommodating, though. If a store won't take your gift card,
Horne says the best idea is to "stomp your feet, kick and scream" - eventually
the manager will probably issue you a new one. In the end, he says, consumer
opinion and experience will be the decisive factor for the gift card market. "If
I get a gift card this year and like it, then I will give it to two people next
year. Then each of them will give a card to two more people. That's the way the
business grew in the US, and the way it will grow in Europe."
Of course, if the growth of gift cards is unstoppable, you'll need a strategy to
cope with unwanted cards, just as you did with unwanted paper vouchers.
Fortunately, the digital era makes this easier. Where you once might have had to
barter unwanted vouchers with family or friends, you can now auction them to the
whole online community.
Online auction house eBay lists a couple of thousand gift cards for sale at any
given time, and you can expect to find even more after the holiday. Don't expect
to sell your card for face value, though. For a better deal, you might want to
try cardavenue.com or swapagift.com, where, for a small listing fee, you can
trade cards with other unhappy gift recipients. It's worth a try; there's got to
be someone out there who'd just love an Acme tongue stud.
Bah Humbug
* 23 December 2000
* Sidney "Scrooge" Perkowitz
ONLY a Scrooge could resist the cheer of Christmas. But let's face it, the
holiday does have its darker side. Every year you have to buy gifts for people
that you rarely see, or don't even like. Gifts for relatives like Aunt Tilda, in
return for the hideous vase she gave you last year, and those you swap with
bosses, co-workers or business acquaintances, for whom you feel little kinship at
best, and a touch of resentment at worst. Unfortunately, you tend not to get away
with giving out lumps of coal-not even to naughty nephews. So how can you ignore
the Christmas spirit without anyone noticing?
What you need are gifts that carry a secret Scroogian undertone, like an
uncharitable thought concealed behind a socially acceptable smile. Fortunately,
today's technology provides the answer: an array of sleek gifts that radiate
glossy desirability, yet also give you the means to express that hidden message.
In fact many gadgets make fine Trojan horses-the perfect present to give when
your heart isn't really in it.
To choose the right, slightly malevolent, tech-based gift, do as you would for
any gift: consider the recipient. Is he or she a cutting-edge type who can't live
without owning the latest and the fastest gadget? Then your path is clear. Give
him or her a piece of gear that is just slightly out of date: last month's
computer with a processor that runs at only 700-megahertz rather than the
1-gigahertz chip of this month's machine, an obsolete personal organiser too
bulky to slip into a pocket, or a movie on videotape rather than DVD. Then watch
the recipient gnash teeth at the realisation that the gift confers no bragging
rights whatsoever.
Alternatively, your giftee might be someone who can barely manage to set the
correct time on a digital watch. For the technophobe, choose something overly
complex, a cellphone so packed with features that its buttons have multiple
functions, say. This makes it nearly impossible to select the right option,
especially when in a hurry. And if the keys are tiny as well, the frustration
level can reach fever pitch. Similar amusing effects can be attained with some
home stereos and car radios, such as the one in a certain top of the range sedan,
where operating the radio is akin to piloting a jumbo jet.
There are other possibilities for every type of person. Take someone with a
simple, frugal lifestyle, perhaps out of concern for the Earth's resources and
the environment. Nothing galls such an idealist more than a device that uses
ridiculously sophisticated technology to complicate what was once straightforward
or fills a need generated only by other technology, such as a waterproof case for
when you take your cellphone boating. Even better, how about a device that works
exceedingly well but does something really trivial, such as an analogue
wristwatch with a built-in laser light show?
Under the general heading of "Things nobody really needs", a good stocking-filler
is a digital pressure gauge for car tyres. Instead of an old-fashioned, simple,
reliable mechanical gauge, clearly marked in pressure units and needing no power
source, the "improved" version is battery-driven, must be calibrated before each
use, and presents tyre pressure on a tiny, barely readable LCD display.
Another pointless gift is a motorised tie-rack that holds up to 80 ties and
slowly rotates them into view, as if it took incredible energy and determination
to riffle through one's ties by hand. Even when business wear was comparatively
formal, how many men owned this many ties? This gadget has the weird distinction
of being simultaneously over-teched, under-useful, and outdated-a nice violation
of the principles of simple living that is sure to raise hackles.
Possibly the champion cool-but-not-that-useful gift, however, is a hand-held
global positioning system (GPS) sensor to tell you where you are on the Earth's
surface to within a few metres. Unless you are a sailor blown off course or are
in a mountain rescue team, knowing your exact latitude and longitude is of
limited use.
To fill this vacuum, GPS addicts have even invented their own sport: geocaching.
It consists of placing something of low value-like a can of beans-in the middle
of nowhere; recording its exact coordinates via GPS and posting these on the
Internet so other intrepid GPS-bearing explorers can hike for hours to find the
treasure. A GPS sensor is well suited to a tech-oriented business rival, where
time spent on this pointless exercise might well flatten his or her career
trajectory.
Time is also a major issue for any recipient who-like many of us-juggles a
multitude of personal and career responsibilities. Why not get him or her a
radio-controlled clock that uses radio signals from a centralised atomic
timekeeper to constantly update the display with an accuracy of nanoseconds. Such
a clock allows absolutely no leeway for lateness and can only add to the stress
of a busy life. (If you're feeling mischievous, buy an analogue version and just
before you wrap it, loosen the nut that locks the hands in place. Then move the
minute hand back by five minutes and retighten the nut. Now the clock will
faithfully keep the wrong time, no matter how often the infuriated owner resets
the hands.)
If you don't know your recipient that well, you can always rely on food and
drink. These offer fruitful possibilities for gifts that deliver a subtle not-so
festive greeting, from digital toasters and fuzzy-logic rice cookers to intricate
designs for fool-proof wine-cork pullers that pinch your fingers every time you
use them.
There are, heaven help us, even items just right for the child unlucky enough to
qualify for the traditional lump of coal. Your annoying nieces and nephews will
be delighted to play the latest computer games machine. With incredibly realistic
displays and hand-held controllers that rival the cockpit of a jet fighter, you
enjoy the peace and quiet, safe in the knowledge that only the sturdiest child
will avoid full visual and muscular lock-up.
Of course, this all goes to show how far we have come since Scrooge. A lump of
coal is mostly carbon, and carbon is chemically similar to the silicon used to
make electronic chips. Nowadays, instead of giving a dirty chunk of coal to make
a point, we can achieve the same effect with a tiny, ultra-clean but sneakily
subversive piece of silicon.
Review : Dickens of a book
* 29 June 1996
In Scrooge's Cryptic Carol: Three Visions of Energy, Time and Quantum Reality by
Robert Gilmore (Sigma Press, £9.95, ISBN 1 85058 531 8), Scrooge is visited by
spirits who take him, willy-nilly, through past, present and weird physics
(future not being available). He is a changed and better educated man at the end
of it. So should you, the reader be, as long as you can swallow the Christmas
Carol conceit. The spirits are relentlessly didactic, carrying on as if they have
a phantom script. The light-hearted drawings help.
Europe's last wild reindeer herds in peril
* 11:04 19 December 2003
* Andy Coghlan
Europe's last remaining population of wild reindeer is in peril. Its survival is
being threatened by the building of dams, mountain cabins and hydroelectric
schemes across their natural habitat in southern Norway.
Conservationists warn that human activity in wilderness areas is growing so
rapidly that both wild and farmed reindeer, or caribou, may one day suffer a
similar fate in their strongholds across the Arctic tundra and taiga.
Christian Nellemann of the United Nations Environment Programme in Arendal,
Norway, and colleagues have documented the steep decline of the Norwegian
reindeer. To flee human construction projects, animals crowd into ever smaller
areas, with ever scarcer supplies of the lichen on which they feed (Biological
Conservation, vol 113, p 307).
"The situation in Norway is quite critical," says Nellemann. "They've lost 50 per
cent of their habitat in 50 years."
Monitoring the reindeer before, during and after a decade of major infrastructure
projects between 1977 and 1987, Nellemann's team found that reindeer retreat
dramatically from anywhere that lies within four kilometres of new roads, power
lines, dams or cabins.
Plummeting density
Summer population densities in these zones now fall to 36 per cent of what they
were before the building projects. Instead, herds crowd into remoter areas, where
densities have increased by 217 per cent.
In winter the effect is even more extreme - reindeer move away from developed
areas in such numbers that herd density there falls to just eight per cent of its
natural level.
Nellemann says that human-built obstacles such as roads, power lines, reservoirs
and dams serve as frontiers that reindeer herds are reluctant to cross.
So many exist that the 30,000 remaining animals - down from 60,000 in the 1960s -
are fragmented into 24 isolated groups. At this rate of decline, Nellemann says
there will be room for just 15,000 animals by 2020.
Breeding collapse
Overcrowding and fragmentation have led directly to overgrazing and a collapse in
breeding rates. "In some of the worst-hit areas, only one in three reindeer
females is having a live calf," he says. This compares with the expected calving
rate of between 80 and 90 per cent.
And the problem is likely to spread. "By 2050, the UNEP expects 70 to 80 per cent
of the Arctic to be developed with infrastructure, so Greenland, Canadian,
American and Russian reindeer will all be threatened," says Nellemann. "It's the
last true wilderness, and food and resources are concentrated in very small
areas, so unbridled development can have a huge impact on reindeer survival."
One solution in Norway is to extend national parks to reopen vital migration
routes severed by infrastructure projects. But first the Norwegian government
needs to stymie further development, such as the unregulated building of cabins,
says Nellemann.
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Weblinks
* UNEP, Arendal
* http://www.grida.no/
* Reindeer, Arctic Studies Center
* http://www.mnh.si.edu/arctic/html/caribou_reindeer.html
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In search of Schrodinger's reindeer
* 23 December 1989
* MATTHEW DAVIES and MARTIN SLAUGHTER
WITH the festive season upon us, many scientific minds will yet again be
attempting to solve that perennial chestnut, the Travelling Santa Problem (or
TSP). This problem was first brought to our attention by the child prodigy,
Vernon P. Templeman, in his seminal paper 'Please may I have a bike for
Christmas, Daddy' (J. Appl. Window Shopping, December 1988, vol 7, p 1-122). In
simple terms, the problem boils down to one of speed. How can Father Christmas
visit the homes of all the children in the world in a single night, albeit 24
hourslong? Templeman demonstrated that theclassical (sequential) explanation
forces usto invoke faster-than-light travel, which issomewhat at odds with
current thinking. Thus, he argued, we should infer thatthe Father Christmas
effect does not reallyexist. This contentious hypothesis wasthe subject of much
debate at a recent symposium held at the Santa Fe Institute forPresent Research.
Our initial thoughts were that Templeman had over-estimated the size of the
problem, forgetting that Santa only visits good children. This would reduce the
number of visits by a factor of order 10**9. However, a simple
back-of-the-lab-coat calculation shows that this renders the problem no more
tractable. This threw suspicion on the use of classical physics.
At this stage, the teachings of our old mentor, Erwin Schrodinger, came back to
us ('Famous people what we claim to have known, honest', by Matthew Davies and
Martin Slaughter, Annals of Physics, 1983, vol 12, pp 379-381). From a detailed
study of reported phenomena, it became apparent that Santa shared many of the
characteristics of elementary particles, suggesting a quantum mechanical
interpretation of his behaviour. We have since developed this theory, and are
confident that a quantum mechanical model of Santa Claus allows many of his
observed properties to be explained, and several interesting predictions to be
made.
Clearly, viewing Santa as a waveform removes the apparent paradox of his
'presence' being measured in several locations within a short interval of time.
As the waveform collapses down in a specific location (attracted, we suggest, by
the Goodness Quantum number of the recumbent child) it becomes perfectly valid to
state that a 'visitation' has occurred. However, our calculations suggest thatthe
process of measurement (for example,turning on the bedroom light) will
almostcertainly lead to a localised, space-timeinstability which, in turn, will
cause thewaveform to relax and render detectionalmost impossible.
Once again, this ties in with the experimental evidence that Father Christmas is
rarely caught delivering. Indeed, on those few occasions when a sighting has been
claimed in the literature ('Mummy, mummy, there's a strange man in my bedroom',
by S. T. U. Peedo, Journal of Sleepless Nights, 1979, vol 5, p 35), closer
scrutiny has often revealed it to be an imposter wearing a red cloak and beard.
Moreover, the quantum mechanical model predicts that the energies involved in a
waveform collapse will result in the emission of a jet of sub-atomic particles.
Studies of bedroom carpets in the vicinity of alleged sightings, using an X-mass
spectrometer, have often revealed evidence of mince pion activity; though these
have usually been Hoovered up.
One of the most appealing aspects of our theory is the manner in which it allows
the most likely sites for visitation to be estimated. These may be identified
from the first derivative of the expectation value as:
d (Spot) ] -------------] d (Fireplace)]night
It turns out that the distribution of household chimneys is exactly that required
to act as a diffraction grating for objects of Santa's predicted wavelengths,
focusing the zeroth order onto the bedroom floor below ('Chimchimmeny,
chimchinny, chimchin cheroo', by Bert, Mar. Popp. 1969).
Yet another predication which agrees with commonly reported observations concerns
the Christmas Stocking effect. Within the general theory, the stocking would be
expected to act as an infinite potential well, momentarily capturing the Santa
waveform. The resonance within the stocking is predicted to transfer energy from
any batteries within the well (causing them to run out by Boxing Day) before
collapsing back down to a new ground state characterised by a tangerine in the
toe.
Apart from the successes reported above, the theory makes a number of predictions
about rather low probability events; that is, events expected to occur in fewer
than one hundred homes in the world each year (for example, a full night's sleep
for parents of under-8s; no clothes given as presents; fairylights still working
from last year). In order to collect the huge volume of data needed to assess
these rare events, we have decided to appeal to the scientific community for
help.
Well as the few observations available fit the theory, a detailed experiment to
provide quantitative support is now necessary. This will require a vast amount of
data to be collected with observations from as many global locations as possible.
New Scientist's readers are, therefore, asked to maintain a Yule log of the
events in their domestic laboratories and to send their results to the authors
via the magazine. Participants are requested to make a note of the following:
(1) Their children's Goodness Quantum number; (2) The approximate dimensions of
their bedroom; (3) Whether Santa visits and, if so, at what time; (4) Their
address and galactic 4-space coordinates (or postcode); (5) Any evidence of Charm
or Strangeness; (6) Whether Santa is seen to be spinning (needed to check the 'No
L' theory); (7) The number of presents left; (8) The colour of his reindeer's
nose (often quoted as red when seen moving away at speed, but unknown in its rest
frame).
On a note of caution, participants are urged not to try to localise Santa as
theDp. D x - h relationship suggests that the energies involved could demolish a
timber frame building.
At a time when Europe is leading the world in fundamental physics research we
hope that this knotty problem can be resolved with this experiment. The Americans
are not far behind, with Senate approval for the $12 trillion Turkey/Anti-Turkey
Synchronous Santatron. Let us make sure we cook their goose before they foil our
efforts.
Matthew Davies and Martin Slaughter are physicists working in the computer
industry.
Wormholes in Wonderland
* 24 December 1994
* Ian Stewart
THE NORTH POLE, A DECEMBER SOMEWHERE NEAR YOU: "My customer base has gone up
fivefold in less than a century," Father Christmas explained to his assembled
subordinates. "If it wasn't for the new X/MAS ultra-paragigaprocessor, I'd never
be able to maintain my extremely tight delivery schedule. But now, at last, all
my problems have been solved."
A loud explosion echoed around the underground ice caves. A dishevelled
Vice-Gnome for Computing rushed in. "Major hardware failure in the X/MAS
ultrawhatsit, Santa," he said, panting.
"What happened?"
"Algorithmic gridlock. We were running the travelling salesman program to
optimise the delivery route, and the flash memory flashed. The computing
requirements are growing exponentially with the number of PASCUs we have to
visit."
"PASCUs?" asked Santa.
"Personal Activity System Consumer Units," the Vice-Gnome for Marketing answered.
"Previously known as, um, let me see, children."
Santa shook his head sadly. "I should never have sent you gnomes to business
school. Why do we need to optimise deliveries, anyway?"
"The sleigh is running perilously close to the speed of light as it is. Unless we
choose the shortest route, we'll never be able to visit every PASCU on Christmas
Eve." Computing flopped into a chair.
"That's not the only problem," the Vice-Gnome for Distribution added. "The sleigh
is travelling so fast that the reindeers' energy requirements are skyrocketing,
and Rudolph's nose has turned blue with cold because his metabolism can't keep
up. I really do urge you to consider my memo proposing that we stagger deliveries
over several weeks. Our business is ridiculously seasonal."
"I agree that something must be done," said Santa. "But I refuse to abandon my
traditional role."
"Well, there's always Finance's plan to change our corporate structure to a chain
of subsidiaries owned by Claus Holdings plc, based in the Cayman Islands. That
way the group as a whole can avoid taking responsibility for late deliveries."
"No," said Santa, with a nasty glint in his eye.
Marketing backtracked rapidly. "Right, I can go with that. Preservation of
corporate image, yes, yes, very important, yes, of course."
"Desperate times," said Santa, "demand desperate measures. "We must leapfrog to
an entirely new level of technology, one with the capacity to solve all of our
problems for the indefinite future."
The Vice-Gnomes for Production, Marketing, and Finance nodded. "I like the idea,"
said Marketing. "But what exactly do you have in mind?"
"I'm dreaming of a relativistic Christmas," said Santa. "I've been keeping an eye
on the physics journals, and over the past few years a lot of potentially useful
new concepts have appeared."
"We're a product-oriented corporation," said Finance, worriedly. "We're geared up
for manufacture of Personal Activity Systems, not for R&D."
"On this occasion, as an exceptional measure," said Santa, "I am willing to bring
in outside consultants. I shall secure the services of Hawkthorne Wheelstein,
Chartered Relativists." Santa dismissed his Vice-Gnomes and pulled a cellphone
from his beard.
THE NORTH POLE, SOME DAYS LATER: Amanda Banda-Gander, Hawkthorne Wheelstein's
salesperson, stabbed at the brochure with a beautifully manicured fingernail. "l
recommend a boundary across which no matter or energy can return. It's called a
black hole."
"Because it's black and things fall into it?" Marketing hazarded.
"More or less. Things do fall into it, and can't then escape, but it actually
gives off radiation, and looks red to someone on the outside."
"And a white hole?"
"Like a black hole but reversed. Matter comes out, but it can't get back in."
"Ah, I see. And when you join the two together, you get a one-way tube?"
"Known as a wormhole, yes. What's more, it is a tube that goes outside the normal
Universe altogether - a cosmic short cut, connecting two regions of space like
the handle on a briefcase. So Mr Claus can carry the black end, as we call it, on
his vehicle, and arrange for the white end to materialise inside each dwelling
that he visits. No more sooty chimneys, and no trouble at all getting stuck
inside central heating systems."
"Fantastic," said Santa. "But how do I get out again?"
Amanda smiled. "By using a second wormhole, of course. And if you buy the black
and white holes separately, together with a special linking module, then you can
make a substantial efficiency gain. Just as black holes constantly suck matter
in, so white holes constantly spew matter out. We can customise your white holes
so that they emit an endless stream of toys."
"Personal Activity Systems," said Advertising.
"Sorry. And wrapping paper and ribbons, thereby solving all your manufacturing
problems at a stroke."
"I like the sound of that," said Finance. Production was less sure - it looked
like she might be out of a job.
"Conversely, black holes can solve forever the problem of disposing of unwanted
wrapping paper and ribbons."
"And unwanted Personal Activity Systems," said Marketing sagely. "They all end up
in the dustbin eventually."
"True. You could recycle almost everything if you wanted to."
"This is all very well," said Santa, "but our most urgent problem is one of time.
The faster-than-light sleigh has not yet been invented."
"No, but the warp-drive sleigh has. Our Enterprise model has proved to be
especially popular."
"Warp drive?"
"According to relativity theory, matter can't move through space faster than the
speed of light. But, and this is the neat bit, there's no limit on the speed with
which space itself can move. So here's what I suggest - the sleigh can sit at
rest in a small bubble of space, and we will arrange for the bubble to flow at
superluminal velocities through normal space. I know it sounds like science
fiction, but Miguel Alcubierre at the University of Wales College of Cardiff has
recently shown that it is entirely consistent with modern physics. Admittedly, it
does violate the 'weak energy condition' that requires all energies to be
positive. But that's a purely technical difficulty that can be overcome using the
Casimir effect, which creates negative energies between two parallel plates in a
vacuum." She waved her hands dismissively.
"Supersonic flight produces sonic booms," said a gnome from the Legal Department,
wary of possible third-party lawsuits. "Does a warp drive produce gravitic
booms?"
"No, it's guaranteed free of gravity-shock-wave emissions," said Amanda, rather
too glibly.
"I don't like it," muttered Legal's gnome to Santa worriedly. "Even if Hawkthorne
Wheelstein indemnified us, we could be held responsible if they go out of
business."
"That's a good point," said Santa. "Do you have any alternative solutions to our
scheduling difficulties?"
Amanda pursed her lips. "Well ... there's our latest range of products. Time
machines." She waited as the idea soaked in. "That way, you can stagger
deliveries throughout the year, while making sure that every single item is
delivered on Christmas Eve."
"How does this time machine work?"
"We have several models. The simplest is the moving wormhole, invented by Michael
Morris, Kip Thorne and Ulvi Yurtsever in 1988, and based on the twin paradox of
relativity theory. If an object travels very close to the speed of light, then
time, as experienced by an observer moving with the object, slows to a crawl
relative to that experienced elsewhere. Imagine two identical reindeer, Donner
and Blitzen. Donner remains on Earth, and Blitzen heads off into space at nearly
lightspeed, returning forty years later as measured by an Earthbound observer.
Donner has aged forty years, but because of this time dilation Blitzen has aged
only five, say.
"Morris, Thorne and Yurtsever realised that by combining a wormhole with the twin
paradox, they could get a time machine. The idea is to leave the white end of the
wormhole fixed, and to zigzag the black end to and fro at just below the speed of
light. Seen from inside the wormhole, both ends age at the same rate. But from
outside, the black end ages more slowly because of its speed. This time
differential means that the passage of time is different if you go from one end
to the other through the normal Universe, or through the wormhole itself. In
fact, if you travel through normal space to the black end and then dive through
the wormhole, you end up in your own past. You can read all about it in New
Scientist, 28 April 1990, if you don't believe me.
"There's another approach that we're working on at the moment, which should be
operational very soon. It was invented by Richard Gott in 1991, and it involves
using two cosmic strings - thin massive objects whose existence was first
predicted by some grand unified theories - that pass very close to each other at
near lightspeed," said Amanda. "And we've got some new methods coming along that
don't need any singularities at all."
"Brilliant," said Santa. "We'll take ten of everything."
THE NORTH POLE, DECEMBER 2994: Santa sat at his computer monitor, studying the
time travel schedules, frowning. A thousand years had passed, and still
deliveries for 1994 had not been completed. There had been teething troubles. The
wormholes were always being coned off for repairs, and the contraflows were a
nightmare. The sleigh was getting totally clapped out and spent most of its time
in the garage; sleigh rides were constantly being cancelled because reindeer were
getting time-travel sick. Leaves kept blowing into the wormholes - the wrong kind
of leaves, apparently.
But what the heck. Santa relaxed and cracked a smile. There was literally all the
time in the world to get the system working. He sipped at a glass of sherry and
nibbled a biscuit. Suddenly his peace was shattered.
"Emergency! Santa, quick, do something!"
"What's happened?"
"I know we've only a few time machines here and now, but because all of our
deliveries happen on the same Christmas Eve there are billions of white holes,
accumulating all the time, on Earth in 1994. The topology of spacetime is
becoming so entangled that baby universes keep budding off, and I'm worried that
one of them may take the Earth with it."
Santa suddenly realised that he had never seen this particular gnome before.
"Where's your superior?"
"Um, gone on a course about intellectual property rights."
"Don't lie to me. Bad little gnomes don't get their Christmas presents,
remember?"
"Oh, all right. Er, he's gone to see the birth of Christ."
"WHAT?"
"It's become a very popular tourist attraction since the invention of the time
machine, Santa. All the major historical events have. The Sacking of Rome, the
Battle of Hastings, the signing of the Declaration of Independence."
"You're telling me that my gnomes are using my time machines to bunk off work and
go see the historical sights?" yelled Santa.
"Um, yes." The gnome looked embarrassed. "They do take Him presents."
"Idiots! The inn at Bethlehem will start to resemble a football match with all
those gawping gnomes piling up! Do you recall any reports in the Bible about
thousands of gnomes paying their respects to the infant Jesus? Bringing gifts of
gold, frankincense, and My Little Pony?"
The gnome hung her head in shame as Santa raged. "You mindless incompetents have
created a cumulative audience paradox!"
He paused, reflected, simmered down. "Except that in the real Universe, you don't
get paradoxes. Hmmm." Santa chewed on the problem for a while. "Of course! The
many worlds interpretation of quantum mechanics must be valid. Each time shift
carries us into a new version of the Universe, coexisting with the original but
separated from it along some totally new kind of dimension."
"Oh. So that's alright, then."
"Well, I don't see why it should cause us any serious difficulties. But until
science has fully mastered the intricacies of parallel universes, well, jaunts to
see the Nativity are out. Do you understand?"
The gnome hurried off, relieved. Santa returned to his schedules with a vague
feeling that he was missing something.
A BILLION PARALLEL NORTH POLES, A BILLION PARALLEL DECEMBERS: "My customer base
has gone up fivefold in less than a century," a billion parallel Father
Christmases explained to their assembled subordinates. "If it wasn't for the new
X/MAS ultraparagiga processor, I'd never be able to maintain my extremely tight
delivery schedule. But now, at last, all my problems have been solved ..."
Grottoes new
* 25 December 1999
* Justin Mullins
IT isn't easy being Santa Claus. In his grotto at the North Pole he faces
freezing temperatures, howling snow storms and recalcitrant reindeer. But if
things seem bad now, just wait until we colonise the Solar System. When Santa
looks for a new base among the planets, the conditions are going to be much, much
worse. Still, if he chooses wisely, he could be in line for some of the most
spectacular views in the Solar System. So Santa, if you're reading, here is a
quick guide to the poles on offer.
The north pole of any planet is defined by a trick known as the right-hand screw
rule. Make your right hand into a "thumbs up" shape. If the planet's direction of
rotation matches the way your fingers curl, your thumb points towards the north
pole. Try it with the way the Earth rotates (the Earth's rotation is from West to
East, which is why the Sun appears to move from East to West).
The north pole on Venus is underneath the planet as seen from Santa's home on
Earth, because Venus spins in the opposite direction from every other planet in
the Solar System. Not that Santa or anybody else standing there would know the
difference. Venus has a dense atmosphere of carbon dioxide filled with
lemon-yellow clouds of highly concentrated sulphuric acid. The atmosphere would
allow only a murky yellow light to penetrate to the pole and Santa would never
see the Sun move across the sky. He would be able to see for several kilometres
at the surface, though, and pictures of Venus show a very flat rocky terrain.
"It's a bit like the bottom of the ocean," says Andrew Ingersoll, professor of
planetary science at Caltech in Pasadena.
There'd be no need for a heavy beard or thick red woollen clothing to keep warm.
At more than 450°C, the temperature at the surface is hot enough to melt lead and
the pressure is almost 100 times that on Earth's surface. The weather patterns on
Venus are likely to be very consistent throughout the Venusian year, which lasts
for roughly 224 Earth days. This is mainly because the atmosphere is so thick and
moves so fast that any heating or cooling gets mixed around very quickly. "You'd
hardly know whether it was summer or winter," says Ingersoll.
A more spectacular place to set up base might be the north pole of Mercury.
Mercury is a small, barren planet pockmarked with craters and no atmosphere worth
mentioning. Conditions there are particularly harsh: because it is so close to
the Sun, the maximum temperature is around 400°C. But the planet has no
atmosphere to retain the heat so the temperature is less than - 150°C in the
shade. Most of the planet experiences both extremes of temperature during each
long `day', which lasts 176 Earth days. And yet the poles might be to Santa's
liking.
Because of the way the Earth's orbit is inclined relative to Mercury, astronomers
can sometimes see Mercury's poles. "We've had a pretty clear look," says
Ingersoll. By bouncing radio waves off this part of the planet, they have spotted
signs of ice. Astronomers suggest that ice could only survive the fierce daytime
sunlight at the bottom of craters that are permanently in shadowa situation that
can only exist because Mercury spins with its axis almost perpendicular to its
orbital plane.
These craters would be extraordinary places, says Ingersoll. Deep inside them,
the sky would appear black but the landscape would not be entirely in the dark.
While the Sun's body would be hidden from view, its outermost atmospherethe
coronawould still show above the mountain tops at the crater's edge. The
shimmering corona would cast an eerie blue light across the crater floor, and
every now and then a huge arc of plasma known as a coronal mass ejection would
burst into view above the horizon.
The pale blue light would reveal a strange landscape. Nobody knows what form the
ice on Mercury takes but it is almost certainly left over from comets that have
collided with the surface. Ingersoll guesses that it could be in the form of
dirty boulders of frozen water, carbon dioxide and even noble gases such as
argon. The ice would not only provide a spectacular setting but would be a useful
resource for anybody setting up on the planet. A supply of water, for example,
would mean that Santa would not have to take his own.
The north pole of Mars is in some ways similar to Earth's. It is currently
pointing away from the Sun and so is in the middle of a harsh winter, much of it
spent in total darkness. It also has a polar cap consisting mainly of water ice.
If Santa wanted to reward his elves with a relaxing beach holiday at the end of
the season, Mars would have a distinct advantage. "The permanent ice cap is
surrounded by sand dune fields like those in North Africa," says Ronald Greely, a
planetary geologist at Arizona State University in Tempe. The dunes range in size
from just a few metres across to 100 metres. In winter they become lightly dusted
by a bright frost of dry ice. And since dry ice turns directly from solid to gas,
this frost would disappear magically under the eyes of the elves when they
embarked on their summer break.
Possibly the most interesting place to set up a base would be Titan, Saturn's
largest moon. Titan's atmosphere is so thick with methane and ammonia that
astronomers have difficulty seeing the surface. Methane exists as a liquid, gas
and a solid on Titan, just as water exists in all these forms on Earth. The few
tantalising glimpses astronomers have had of the surface indicate that it may
have oceans of liquid methane as well as solid land masses. Nobody is quite sure
what exists at the poles but it cannot be a floating mass of ice as it is around
Earth's North Polemethane ice does not float on liquid methane. Astronomers hope
to get a better idea of what exists beneath the atmosphere on Titan in 2004, when
the Cassini spacecraft, now en route to Saturn, will drop a probe onto this
wintry moon.
If it's seriously cold conditions that Santa is after, the outer Solar System is
by far the most promising destination. The north poles of Saturn, Neptune and
Pluto are all pointing away from the Sun and so these places are in the throes of
winter. "The Solar System is a very wintry place at the moment," says Ingersoll.
Hear that, Santa? You'll be spoiled for choice.
Track Santa's progress online
* 25 December 1999
* Barry Fox
`TWAS the night before Christmas deep inside Cheyenne Mountain in Colorado, the
Combat Operations Center of the North American Aerospace Defense Command.
Protected from nuclear attack by blast-proof doors and the tonnes of rock around
them, a thousand NORAD personnel were winding down, looking forward to the
holidays. Suddenly, something stirred.
On a giant map in the operations room, a red light began to flash ominously over
the Arctic. NORAD's job is to scour the skies for signs of air attacks against
the US and Canada. To this end, the cavernous operations centre is connected by
blast-hardened cables and antennas to a worldwide network of radar dishes and
satellites. The red light signalled that something potentially threatening had
taken to the sky. Far to the north, fighters scrambled to intercept it.
As the jets approached the target, the tension rose inside Cheyenne Mountain.
Then, came relief. "It's OK," squawked a pilot over the loudspeaker, "It's Santa.
He's heading south."
Don't laugh. According to NORAD experts, every year, Santa wakes on Christmas
Eve, clambers into his reindeer-powered sleigh and sets off from the North Pole
to New Zealand before working his way westwards to the Americas. Once he's
finished with Canada and Alaska, he crawls
back into bed for a year's well-earned rest. If you don't believe the experts,
you can see for yourself. With help from IBM, NORAD will post Santa's progress on
the Web (www.noradsanta.org).
Even if you are one of those sceptics who does not believe in Father Christmas,
the NORAD Santa website is worth a visit, because it gives an insight into the
future of e-commerce. The technology IBM is putting at NORAD's disposal is the
same that companies will need to sell goods and information successfully on the
Internet.
NORAD is anxious to point out that all communication into and out of Cheyenne
Mountain is securely encrypted. This ensures that there is no chance of a
schoolboy hacking in and starting World War Three-contrary to what you may have
seen in the movie War Games. It is, then, a complete coincidence that NORAD's
Santa-tracking tradition began with an accident on an insecure telephone line.
Phone fluke
In 1955, NORAD's predecessor CONAD (for Continental Air Defense System) started
receiving calls from Colorado children on Christmas Eve. A local store had placed
a newspaper advert for a telephone hotline to Santa Claus, but the paper
misprinted the phone number, by chance hitting on the unlisted number for CONAD's
Commander-in-Chief.
The officer on duty, Colonel Harry Shoup, thought on his feet and joked with the
children, telling them he could see Santa on the radar screen. Later, seeing the
public relations value of the fantasy, NORAD turned the hotline into an annual
tradition. So every Christmas since, staff at Cheyenne Mountain have given
children updates on Santa's progress.
Two years ago, NORAD switched to a website. Millions of people logged on and
overloaded the system. So last year, NORAD teamed up for the first time with IBM,
and between them, they handled 28 million hits in 24 hours. This year, NORAD is
expecting still more visitors to its site, which will exploit the latest Net
sound and vision technology.
The serious side to all this is that NORAD's experiences mirror those of
countless consumer-orientated companies. The days of telephone hotlines and
telesales are numbered. Phone lines get swamped too easily. Witness the shrill
tones of opera buffs who failed to get through to buy tickets for performances at
the revamped Royal Opera House in London. The cacophony died down only a couple
of months ago when a Web-based booking service opened.
Logjam
Although Net selling is the way of the future, websites can also overload. If the
system runs so slowly that it infuriates customers, all the company is going to
earn is a bad name. Research by chipmaker Intel found that the throughput of
calls to sites tends to drop as soon as they handle anything more than simple
text, low-resolution pictures and insecure transactions. If visitors are buying
goods using an encryption system-to protect their credit card details-or are
downloading moving pictures with sound, then the rate at which their calls are
handled can decrease by 95 per cent. The solution, then, is to increase the
number and speed of processors that serve a site, so they can simultaneously
handle thousands of different requests.
The amount of extra speed and capacity should not be underestimated. In October,
The NetAid website was supposed to feed live video of pop concerts via 1500
servers at 90 locations round the world. They were advertised as being capable of
handling 125 000 simultaneous "hits". But even a top-range PC and digital
connection to the Net could display only postage-stamp-sized moving pictures
which frequently collapsed into blurred still images.
Only a few of the biggest high-tech companies have overcome this problem, by
throwing together mammoth amounts of server power. Intel has one of these "server
farms" near Santa Clara in California and is planning replica sites in Europe.
The Santa Clara site has a thousand or more servers, each powered by a gang of
four-and sometimes eight-Pentium Zeon microprocessors running at 550 megahertz.
Each server can handle at least 10 000 access calls.
IBM has three farms in the US, which it used to provide online coverage of last
year's Nagano Winter Olympics, and this year's Grammy entertainment awards and
Wimbledon tennis tournament. The main farm, on the outskirts of Washington DC, is
linked to the others by high-speed fibre-optic cables and can pass on requests
virtually instantaneously. Like Intel, IBM uses its farms to host its own website
but has massive capacity to spare. It is this spare capacity that NORAD will use
this Christmas.
The first year NORAD tried to put Santa on the Net, it was swamped by 20 million
hits in 24 hours, sometimes running at 30 000 a minute. This is chicken feed for
the IBM farms, each of which can comfortably handle 300 000 hits a minute. Peak
demand at this year's Wimbledon site exceeded 400 000 hits a minute, and
delivered live video coverage from the courts.
All this technology is fine for relaying Santa's position to the world, but
how-you ask-does NORAD know where the jolly old fat man is in the first place?
Fortunately, his sleigh can be seen by radar-once it is in range of NORAD's
dishes, of course. At other times, NORAD relies on satellite-based infrared
detectors.
Normally, these detect and track the heat thrown out by rockets or missiles.
Cleverly, NORAD has adapted this detection system to register the heat from
Rudolph's nose. "Our scientists have not yet been able to calculate the amount of
heat," admits a NORAD duty officer. "But the bottom line is that we see Santa
because of Rudolph's nose."
Before any tinpot dictator or terrorist decides to lob an ICBM onto North
America, hoping it will be mistaken for Santa, there is a second line of defence
to get past-those scrambled jets. "Because Santa tends not to file a flight
plan," explains the officer, "and we have to identify all unknown flying objects,
jets are scrambled in the far north of the company to check that the incoming
target really is Santa's sleigh."
Last Christmas, the website carried images taken by cameras on board the
interceptors to relay "actual digitised images of Santa and his reindeer".
Weather permitting, there should be more pictures this year, and a few extra
surprises.
Blue Christmas
* 22 December 2001
* Catherine Zandonella
* Gail Vines
IS THE gloomy weather wearing you down? Does every cheesy, Christmassy jingle
send your festive spirit plummeting? Is that health kick abandoned in favour of
comfort food and a meaningful relationship with your duvet? Don't worry-you're in
good company. It's winter. Perhaps your body's trying to hibernate.
Some people get the winter blues on a monumental scale. Sufferers of seasonal
affective disorder would rather cosy up to a television set than another human
being. They shun sex for some quality time with a pizza, snooze for maybe 16
hours a day, and are often irritable and moody-the holiday atmosphere just passes
them by.
Small wonder that SAD sufferers compare their condition to hibernation. When
animals prepare to overwinter, they slow their metabolism, retract their gonads,
and hunker down in cosy dens, surviving till spring on a comforting layer of fat.
The theory that seasonal depression is an atavistic form of hibernation has been
doing the rounds for years. Most hibernation researchers and psychologists agreed
it was rubbish. But recent research has reawakened interest in the theory.
It's true there are big differences between seasonal blues and other forms of
depression. Clinically depressed people usually lose interest in food, finding it
tasteless or even unpleasant. They often shed weight and have great trouble
sleeping. Sufferers of seasonal depression are just the opposite, eating and
sleeping with gusto. While SAD affects just a few per cent of the population,
many researchers believe that most of us are susceptible to seasonal overeating,
oversleeping, and a general bodily go-slow. Some even say it's the extreme end of
a spectrum of adaptive responses to winter weather. "We want to establish whether
SAD is part of our genetic background," says George Wilson of the University of
Tasmania in Hobart. "It could be a programmed reaction to shorter daylight hours
in winter."
Two recent studies have uncovered hibernation-like physiology in people with SAD.
Margaret Austen, one of Wilson's colleagues in Hobart, where winter nights
average 15 hours long, looked at SAD-related changes in the autonomic nervous
system. These nerves regulate the functions we don't think about, like breathing
and heart rate, and are deeply involved in hibernation. And it turns out that
they could be just as prominent in seasonal depression.
There are two parts to the autonomic nervous system, which work in opposition to
control bodily functions. The "sympathetic" system boosts metabolism, while the
"parasympathetic" system damps down bodily functions. Just before animals
hibernate, they experience a spike in the activity of their parasympathetic
nervous system, which slows their heart rate and decreases their body temperature
and metabolic rate.
Austen found a similar parasympathetic response in people with SAD. As a result,
her patients had slower heart rates and low energy levels. "Animals prepare for
winter by fattening up and then sleeping through it," says Austen. "In humans
that is not practical, so instead we eat more and gain weight through the winter,
and we lack energy and sleep more."
Another study by Arcady Putilov, a researcher at the Russian Academy of Sciences
in Novosibirsk, Siberia, also found hibernation-like activity in his SAD
patients. They consumed less oxygen and had lower resting metabolic rates than
people who weren't depressed-very similar to the slowed physiology of hibernating
animals during the winter.
Putilov says there is no doubt that the symptoms of SAD are our way of coping
with winter. The binge eating, the fat deposits that form on your thighs, the
feeling you could sleep for 24 hours-all are signs of an adaptive mechanism aimed
at conservation of energy.
A fizzling winter sex drive is an adaptation to the winter chill too, says Thomas
Wehr of the National Institute of Mental Health near Washington DC. Historical
and experimental evidence shows that human responses to seasonal changes may have
been more pronounced before electric lighting was common. Low sex drive in winter
could have served both to conserve energy through the winter and ensure that your
offspring are born at a time when food is available. Babies conceived in winter
would be born in autumn, when food is starting to become scarce. Babies conceived
in summer would be born in spring, when food is starting to be plentiful. "There
are definite parallels between SAD and seasonal influences on human
reproduction," says Wehr.
An exploration of the genes involved in hibernation indicates that humans
certainly possess all the necessary machinery to hibernate. Matthew Andrews at
the University of Minnesota at Duluth discovered two genes responsible for
shifting metabolism to burn fats from reserves rather than carbohydrates, a vital
process for kick-starting hibernation. A host of other genes are involved too.
"Almost every gene we've looked at so far [in animals] is found in humans," says
Andrews. It seems that these genes are common in mammals but that hibernators
have found particular ways of harnessing them to ensure their survival under
extreme conditions.
Although each animal follows slightly different cues that tell when it is time to
hibernate, day length is always a key factor. The shortening period of light
tells the body's circadian clock that winter is approaching. Even ground
squirrels, which seem to have an inbuilt annual clock and go into hibernation
regardless of day length, use it as a way calibrating their annual timekeeper.
Shorter days also trigger SAD. Treatment of SAD usually includes sessions in
front of a strong light source each morning. This phototherapy works by tricking
the circadian pacemaker in the brain, and it works well at improving mood and
reducing lethargy and food cravings.
But do these many hibernation-like adaptations mean our ancestors actually
hibernated? Is SAD an evolutionary leftover? Andrews says that the existence of
the genes alone is no proof that humans once hibernated. Still, he says, "If
there were any vestige of hibernation in humans, it makes sense that it would be
something like SAD."
But if humans had hibernating ancestors, shouldn't we all get SAD in the winter?
Wehr believes that all humans have the potential to succumb to seasonal affects,
but that most of us can ignore changes in day length because we live in a world
of artificial lights. People with SAD don't seem to be able to use artificial
light to set their circadian pacemaker, according to recent work by Wehr. "I
suspect what we call winter depression has its origins in evolutionary biology,"
he says. "The symptoms of winter depression might well have been normal behaviour
but now we view them as extreme."
Despite the many biological similarities between hibernation and seasonality in
humans, many researchers are far from convinced. Hibernators gorge themselves
before they retreat into their dens, not during winter as we do. Hibernating
squirrels can drop their body temperatures to just above freezing for weeks at a
time, something we couldn't dream of. Even bears, much closer to us in size, are
capable of surviving up to five months on their own body fat, something few of us
could muster.
But lots of non-hibernating animals make it through winter in a somnolent torpor,
reducing their body temperatures and whittling their metabolisms down to a
minimum. Madagascan lemurs retire to a tree-hole during the winter, where they
sit like zombies for days on end. It's lack of food, rather than cold, that
drives the lemurs to hibernate. Since humans evolved in the equatorial climes of
Africa, perhaps our hunter-gatherer ancestors may have evolved a similar ability
to survive long periods without food.
Nowadays we just have to survive long nights. Luckily we can load up on holiday
sweets and spirits to help us make it through the winter. Crawl under the covers,
get the candles lit and the fire roaring, hit the remote control, and let those
holiday party invitations pile up. Don't feel guilty. After all, you are just
doing what comes naturally.
* * *
Let there be light
THAT we are creatures of light is never more obvious than at Christmas. The first
people to colonise the inhospitable north got through the long winter nights by
inventing festivals of light and of fire. Bonfires, torch-lit processions,
roaring hearths and burning candles all lightened the gloom of midwinter.
So it's not by accident that our biggest national festival comes slap bang in the
middle of the northern winter. For millennia, it has been the perfect occasion to
brighten and warm away the seasonal gloom with one helluva party-ever since
humans first made it to the temperate zones, anyway.
The timing of the Christian festival of Christmas gives the game away. The
shortest day of the year, the winter solstice, falls tellingly close, on 21
December. In the old days, anyone keeping an eye on the solar calendar must have
thought-hallelujah, lighter days are on the way, homebrew all round!
Besides the booze, bonfires were the Big Event for midwinter's day from
prehistoric times, according to the pioneering folklorist James George Frazer,
who in the 1920s penned a two-volume study of ancient fire festivals. Apparently,
bones were tossed into the flames to create foul odours that would ward off evil
spirits. The word "bonfire" comes from bone fire. Nowadays we have office parties
instead.
When Christianity took hold, traces of these ancient practices lived on. In
Britain, the 11th-century Danish rule over England introduced the colloquial
Scandinavian term for Christmas, "Yule". In medieval times, the Yule log-the
largest possible that could be communally dragged into the hearth-was
ceremoniously lit on Christmas Eve. Today, the mighty Yule log is remembered by
the chocolate Swiss roll cake. It seems to have lost something in the
translation.
All the same, today's urbanites still yearn for light, greenery, warmth and joy
in midwinter, says Ronald Hutton, professor of history at the University of
Bristol and a leading scholar of modern festivals. We will happily flash our
credit cards to procure the means to create domestic versions of our ancestors'
unruly bonfires. Functional fireplaces and wood-burning stoves are fashion
statements these days.
Even the humble candle is big business. John Terrell Fry of Little Rock,
Arkansas, the author of The Candlelit Home, now works as a "candle consultant"
all over the world. Meanwhile, in Sydney, Australia, Amanda Hammond, author of
Illuminate Living with Candles, reminds us that these small incendiary devices
may no longer be a practical necessity but remain a "powerful symbol of inner
enlightenment".
The electric light bulb, invented in 1879, soon drove candles to near extinction.
But as the 20th century drew to a close, candles miraculously revived, undergoing
what Hammond calls an "unprecedented renaissance". Today, she opines, candles are
widely appreciated as "a symbol of relaxation, celebration, romance and
ceremony".
Such talk is calculated to irritate fire ecologist Stephen Pyne of Arizona State
University. This is "sheer symbolism", he says. Our dependence on fire has become
hidden in machines and delivered along electricity wires. In Europe, burning
candles once bedecked Christmas trees-to furnish light, it was said, for the
woodland spirits sheltering in evergreens after deciduous trees have lost their
leaves. But the elves and pixies were in for a shock. Electric tree lights first
appeared in 1882 in New York, only three years after Edison's invention of the
light bulb. By the 1930s, electric fairy lights-with the bulbs hand-blown in
Germany in the shape of snowmen, Santas and fairies-were the norm. Now you can
buy fibre-optic Chinese-made Christmas lights, or "multi-function" tree lights
that operate in eight modes: "combination, in waves, sequential, slo-glo,
chasing/flash, slow fade, twinkle/flash and steady on".
It's tempting to mock our enthusiasm for such decorations, but might some ancient
spirit of midwinter celebration endure all the same? Reassuringly, Hutton thinks
it does. "When all is said, a vigorous seasonal festive culture survives and
continues to develop among the British," he argues.
Yet what's most noticeable about our celebrations these days is their
privatisation, says Hutton. A century or two ago, the great annual celebrations
revolved round community groupings-the clan, say, or the great household, the
manor, the parish and the church. But today's festivals centre on the family or
the couple, and are typically celebrated at home or at private parties.
We still do notice changing day lengths, but that natural fact no longer acts as
the prime signal for communal celebration. Our lives revolve around our closest
associates-our families, lovers, friends and workmates. "Humanity has come to
replace the natural world at the centre of the wheel of the year," says Hutton.
This state of affairs has its advantages: now we can party whatever the season.
All the same, we still find ourselves staring at the light from open fires and
naked flames-in recognition, perhaps, of what we have lost.
Fire rites evolved out of fire's practical biology, Pyne says-its capacity both
"to purge and to promote" in the living landscape. But in the industrial city of
the 21st century, fire rites have shrunk to votive candles and eternal flames
over memorials. "What has been lost is the daily interplay between people and
flame," he laments. For as we've hidden fire's ecology in machines, we've
gradually lost the knowledge that our livelihoods ultimately depend on the energy
of combustion. Once, he argues, humans knew that what made our species unique was
our ability to control fire. Now, we risk the very future of the world's
biosphere in a profligate orgy of hidden fire. And to think it all started with
those blasted prehistoric bonfires-happy Christmas, everyone!
Skipping Christmas
* 21 December 1996
* Kurt Kleiner
DAVID LEE's job is to make seconds. By international consensus, a second is
defined as 9 192 631 770 cycles of a caesium atom vibrating at its natural
frequency. Every 60 days, Lee measures this frequency, and his colleagues use it
to recalibrate the atomic clocks by which all others in the US set their time.
The process takes about ten days, and this year one of those days is Christmas.
So while the rest of us are tucking into turkey and Christmas pudding, Lee will
be hard at work. And he is only one of many scientists who must shepherd
laboratory work or research that simply won't take a holiday.
Lee works at the US National Institute of Standards and Technology in Boulder,
Colorado. To measure 1 second, he passes a beam of caesium atoms through a
cavity, and shines a beam of microwaves onto them. He adjusts the frequency of
this radiation until a maximum amount is absorbed by the caesium atoms, at which
point the frequency of the microwaves is the same as the natural resonance of
caesium.
Because he must be accurate, Lee has to take a large number of measurements over
10 days, and average them. The atomic clocks at NIST can wander just like any
other clocks, so Lee's colleagues use his frequency to adjust their atomic clocks
to make sure that they are all ticking in perfect time.
The clocks Lee's colleagues are calibrating are accurate to within half a
nanosecond per day. At the end of two months, they might be out by all of 30
nanoseconds. So why not skip it just this Christmas? Why not live dangerously and
let the atomic clocks get out of whack by 60 nanoseconds one way or the other
before resetting them?
Lee says that his colleagues wouldn't be happy. They have to transmit the time
and frequency signals from radio station WWV at Fort Collins, Colorado. These are
picked up by navigation systems which prevent ships sailing off course and planes
missing the runway, and by the latest VCRs which can reset themselves. Besides,
the US has to regularly transmit its definition of a second by satellite to
Europe for averaging with seconds from other countries, to set the Coordinated
Universal Time-the global time standard.
Lee is not the only one who will work over Christmas. Carol Polanskey's team at
the Jet Propulsion Laboratory in Pasadena, California, may have to spend the
holidays downloading data from the Galileo space probe which might otherwise be
erased. Galileo will fly by Europa, one of the moons of Jupiter, before
Christmas. During the closest approach on 19 December, the probe's magnetometer
will record any magnetic field it detects from Europa. "This will be a really big
discovery if it comes through," says Polanskey.
Because of competition with Galileo's other instruments for transmission time,
the first chance Polanskey will have to download data from the magnetometer will
be 22 December. If it doesn't all come through, which is highly possible, the
next chance will be 25 December. Thanks to the Internet, the data can be
downloaded from home, Polanskey says. But if she cannot download all the data on
Christmas Day, instructions will have to be sent to Galileo to prevent it from
overwriting the data. That will mean a trip to the office for one of the
team-Polanskey herself hopes to be with her family in Pennsylvania.
Michele Arduengo, who recently finished her doctoral research at Emory University
in Atlanta, also hopes to spend Christmas at home this year. "The graduate
students are the ones you need to talk to," she says. "We're the ones who show up
for the holidays." In the past, Arduengo has had to check her research several
times over Christmas.
The research subjects that couldn't wait were sexually maturing nematodes,
microscopic worms Arduengo was using to study a gene that helps control sperm
differentiation. She tried to time the breeding so she didn't have to work on
holidays. "But a lot of times the worms didn't celebrate Christmas," she says.
The nematodes take about three days to develop from egg to adult, and Arduengo
had to catch them after their sex became apparent, but before they reached
maturity. Because hatching and maturing rates naturally vary, Arduengo had to go
in over Christmas armed with her platinum worm scoop to prise apart any amorous
nematodes trying to mate at random and ruin her experiment.
Whether artificial life celebrates Christmas or not, Andy Pargellis, a computer
scientist at Bell Laboratories in Murray Hill, New Jersey, plans to take his
research home with him over the holidays. Pargellis uses a computer to produce
sequences of computer code, analogous to the nucleic acids thought to have
existed millions of years ago on Earth before the start of life as we know it. He
installs a program which mimics evolution by altering bits of code at random, in
the same way that mutations occur in nature. He then lets the program to run
until some codes begin to replicate. The resulting codes are like artificial life
forms, and by analysing them Pargellis thinks he can gain insights into how
evolution works and how life began on Earth.
Pargellis doesn't have to work over Christmas, but is so attached to his evolving
"organisms" that he brings them home to breed while he tucks into his festive
fare. It doesn't matter if the program runs in his lab or on his home computer.
"The great thing is I can have a lot of fun with the family, and still get
something done," he says.
While Pargellis is having fun at home, Nancy Love will probably be baby-sitting
her bioreactors on Christmas Day. Love's research, at Virginia Polytechnic
Institute and State University in Blacksburg, is looking at new treatments for
industrial waste water. Her bioreactors use bacteria to break down some of the
organic chemicals found in industrial effluent. To prevent the bacteria dying
from lack of nutrients, Love must run her machines 24 hours a day for months at a
time.
Usually her students look after the reactors. "But I often get pulled in to take
care of things around Christmas," she says. "Anyone who runs continuous flow
bioreactors understands. They are like babies-they are very dependent and must be
tended to."
Bioreactors are not alone in requiring constant attention. Although seismologists
from the University of California at Santa Barbara will be able to check their
instruments via their home computers, they will spend Christmas Day on alert for
signs of an earthquake. The team from the university's Institute for Crustal
Studies looks after a dozen automatic monitoring stations near Palm Springs, and
if all is calm and quiet there, they can start unwrapping their presents.
But if a big earthquake hits at Christmas, the researchers will have to leave the
socks and aftershave and rush into the field. "We really don't want to miss a
large earthquake. We might only get one chance," says Ralph Archuleta, associate
director of the Institute. "If it's magnitude six or bigger, all of us know we
have the responsibility to get instruments into the field. We know that the big
aftershocks occur almost immediately after the big shock, and it can be over
quickly."
By contrast, subjects for research can be almost guaranteed on Christmas Day at
the Savannah River Ecology Laboratory near Aiken, South Carolina, run by the US
Department of Energy. Whit Gibbons is in charge of a project that monitors the
health of wetlands in the area, a study that includes monitoring the animals that
migrate in and out during the year. Gibbons uses pitfall traps to capture animals
such as salamanders, frogs and mice that pass through the area. Every morning a
researcher has to count the animals and release them.
Some Christmases, Gibbons himself checks the traps. He takes along his kids and
makes it a family outing. "Somebody has to get out into the field Christmas and
every other day," he says. The team doesn't decide until quite near the time
who'll be emptying the traps on Christmas Day, but according to Gibbons a
volunteer normally emerges. "It's usually whoever has the most in-laws visiting."
Be happy
* 20 December 2003
* Penny Lewis
WHAT do the Christmas holidays mean to you? Maybe it's happy memories of long,
lazy walks in the snow, excited children, crackling fires and the comforting
smell of home cooking. Or maybe you're the misery-guts in the corner grumbling
about all the rubbish on telly, the naff music, inflated prices and packed shops.
Why do some people have such a rosy picture of the festivities, while others
share Ebenezer Scrooge's view on life, even when their experiences might be
near-identical? One word. Mood.
We all know that our mood affects how we see life. But did you realise that your
mood affects far more than just the experiences of the moment? In fact, your mood
during Christmas present will alter what you remember of Christmases past and
could even distort your feelings and thoughts about Christmases in the future.
"Mood is an internal state which filters external information," explains Klaus
Fiedler, a psychologist from the University of Heidelberg in Germany.
Importantly, it can even influence the way you learn, and how you think about
things long after your state of mind has changed.
We are all familiar with the way places, smells or music we used to know well can
bring memories flooding back. Mood can do the same. Edmund Rolls from the
University of Oxford calls this context-dependent memory. When you form a new
memory, he says, information about the context is also stored. It is linked to
the main memory in a kind of network. When you try to remember, activity in any
part of this network makes it easier to pull the target information off the
memory shelf. Your mood is part of the context, says Rolls, so being in a good
mood means you'll recall memories stored during previous good moods more easily.
According to Fiedler, not only do you remember things you learned in the same
state of mind more easily, you also recall more generally positive things when in
a good mood, and more gloomy things when you're feeling down. This selective
memory has been demonstrated many times: psychologists use music, hypnosis or
other techniques to alter someone's mood, then ask them to recall events from the
past. People who are feeling happy tend to remember more positive episodes and
those who are feeling miserable tend to remember more negative ones. For the
Scrooge-like among us, just being in a dejected state of mind means you'll
remember unhappy times from your past, and the worst bits even from more joyful
occasions.
But there's even worse news for the non-festive. New findings suggest that
feeling unseasonably wretched over the holidays not only dredges up past
Christmas misery, it could also permanently sour future thoughts of the
festivities. On the bright side, however, just one really fantastic Christmas
might ensure that the sight of tinsel and fairy lights gives you a warm, cosy
feeling forever.
Michael Rugg and his team from University College London looked at how the
emotional context in which we learn something affects brain activity when we
remember what was learned. In one study, for example, he asked people to read a
series of emotionally laden sentences such as "the farmer was shredded when he
fell into the corn grinder". The volunteers were later shown emotionally neutral
words such as "corn", and asked to indicate whether or not they remembered seeing
them in the sentences.
Surprisingly, correct recognition of the neutral words led to activity in core
emotional regions of the brain. Other experiments along these lines have pointed
to the same thing: if you learn neutral information in an emotionally charged
context, remembering it triggers an emotional response. Rugg thinks this effect
may be akin to the network idea - recalled words act as clues or contexts
prompting people to dredge up their memories of the emotional sentences from
storage, whether they want to or not.
The association between the emotional and the non-emotional could influence our
everyday memories, suggests Rugg. It could also be part of the problem for people
suffering from post-traumatic stress disorder who can't help continually reliving
emotionally distressing memories. "Emotionally neutral cues in the environment
somehow serve as reminders and cause these distressing memories to be retrieved,"
he explains.
There are other signs, too, that our mood or emotional state affects how we
learn. In a recent study, Susanne Erk and Henrik Walter of the University of Ulm
in Germany used a task similar to Rugg's, in which people were asked to learn
words presented just after they had viewed emotionally charged images. The
researchers found that when people learned words in a negative context, activity
in a certain brain region that plays a vital role in emotions was a good
predictor of how well they would later remember that information.
That brain region is called the amygdala - and Rugg found activity in exactly the
same structure when people retrieved information learned in an emotional context.
The fact that this emotion-related brain activity was so similar during learning
and remembering strengthens the idea that recalling neutral information can evoke
emotions very similar to those felt when it was learned.
Even more interestingly, Walter found that people remember neutral information
better if they are in a good mood when they learn it. A sound lesson for anyone
revising for exams - getting grumpy won't help. The intriguing conclusion Walter
draws is that state of mind really does alter the way information is coded into
your memory. Any new information will be permanently stamped with your good or
foul temper.
The whole picture looks very bleak for people who are chronically unhappy, like
Scrooge. Erk and Walter's work suggests they may learn less efficiently. Even
worse, what they do learn and recall can add to the general gloom. This is a real
problem for people suffering from depression. Not only do they have a selective
memory for sad events, says Rebecca Elliott, from the University of Manchester,
UK. They also dwell on negative thoughts and interpret things in a more than
usually gloomy way. Once you become depressed, says Elliott, you can get locked
into a cycle of concentrating on the negative, getting worse and worse in a
downward spiral.
But is this really relevant to the rest of us? What of those who get just a
little grinch-like at Christmas - should they be worried?
Well, maybe, cautions Elliott. Even mild forms of depression can lead to problems
with memory and attention. "There have been studies with seasonal affective
disorder, which tends to be milder than major depression," she says, "and people
have identified cognitive deficits even in those groups."
Is it more than just memory and learning that follow the tune of our mood? The
answer seems to be yes. Mood also affects how well we can pay attention, the way
we take in information, and even how we think. In fact, Fielder goes so far as to
suggest that our brain processes information in completely different ways when we
are in good or bad moods.
Walter agrees: "Mood is associated with a certain cognitive style," he says, "and
this cognitive style makes evolutionary sense." A negative mood, he suggests
makes you more realistic and more focused on the outside world. You need to deal
with information in a direct, rapid and straightforward way. A positive mood, on
the other hand, usually means you are not in danger, that you have time to
introspect, to be creative, to play around with information - what Fiedler calls
a "loosened" cognitive style.
So what should you do to ensure a happy mood? The answer is simple enough: get
yourself feeling good to start with, and that should reinforce itself. There are
plenty of ways to manipulate how you feel. These range from more serious options
like antidepressant drugs to the everyday strategies most of us use without
thinking: listening to happy music is a reliable one. Exercising, doing something
you enjoy, or just smiling are also tried and tested methods. So there's really
no excuse for stewing in a miserable funk. After all, even the original Ebenezer
Scrooge managed to cheer up when he finally made the effort.
Designer snowflakes
* 23 December 2000
* Stephen Battersby
IT'S SUMMER in southern California, and among the palms and lemon trees a man is
making snow. Inside the physics department at Caltech in Pasadena, Kenneth
Libbrecht grows tiny, frozen crystals that would melt in a millisecond if they
landed on the ground outside. His goal is to find out why no two snowflakes are
ever the same shape, and why they form myriad patterns of plates and needles and
ferns and elaborate baroque stars.
And he seems to have found the answer, or at least a big part of it. Along the
way, he's learned how to make designer snowflakes, developed the art of growing
ice by electricity, and discovered what happens to snow when you get it drunk.
It started in 1997 as an aesthetic quest. "I just thought, I really would love to
make the perfect snowflake," says Libbrecht. Over the past few years he has
polished his art, perfecting a snowflake incubation chambera steel cylinder about
half a metre across with a few tubes attached. Look through a window in the side,
and you can see an embryonic snowflake growing on the end of an ice needle. This
needle is one of his discoveries, grown at express speed by applying a strong
electric field.
"Snow crystals are so beautiful because they are both complex and symmetricaljust
like sunflowers and seashells," says Libbrecht. By changing the temperature and
the amount of water vapour in his chamber, Libbrecht can make any of the
fantastic natural shapes that fall on Norway or New Zealand. If he wants a plain,
flat plate or a many-fingered dendrite, he just presses a few buttons, waits a
few minutes, and there it is.
The symmetry of a snowflake, he says, begins at the bottom. In ice, molecules
cluster together in hexagonal patterns. That means any surface other than a
hexagonal facet will be rough. But water molecules like to wedge themselves into
crevices, where they can form plenty of bonds with their neighbours, so these
rough surfaces quickly flatten out into smooth facets. The smallest snow
crystals, and most of those that grow slowly in the very cold air of Antarctica
or the stratosphere, are simple hexagonal plates or columns.
But if a crystal grows quickly, it will soon turn from a hexagon into a star. If
it sucks up a lot of water from the air, water molecules become scarce near the
surface of the ice. Then any bump in the surface will reach out into a relatively
rich water supply. With more water available it grows faster than the surfaces
below, so it sticks out more, so it grows even faster . . . Before you know it,
an arm has formed, stretching out from the original bump. A hexagonal crystal has
six corners that act just like ready-made bumps, so it will sprout six arms.
But why are there so many different shapes? Why are no two snowflakes the same?
Part of the answer came back in 1936 from the Japanese scientist Ukichiro Nakaya,
who grew snow crystals in his lab at Hokkaido University. Nakaya discovered that
if he changed the temperature of the air just a little, he changed the shape of
the snow crystals that grew in it. Columns, thin plates, thick plates, sectored
plates, hollow needles, dendrites . . . they all form within a few degrees of one
another. "Snow crystal growth is real touchyreal sensitive to external
conditions," says Libbrecht.
Most importantly, the rate at which ice crystals grow zooms up and down by
factors of a hundred or more when you tweak the temperature by just a few
degrees. And changing the growth rate changes the shape too remember that fast
growth means sprouting arms, slow growth means hexagons.
This is the key to snow's kaleidoscopic variations. As a snowflake flutters about
in a cloud, it encounters patches of warmer and cooler air. Each arm of the
snowflake experiences an identical sequence of changes, so while the flake
becomes ever more complicated, the sixfold symmetry is preserved. And each
snowflake will have a unique temperature history, so it ends up with a unique
structure.
This explanation gets us further forward, but in a way it only replaces one
mystery with another. Why is snow-crystal growth so exquisitely sensitive?
To try to answer that, Libbrecht built a snow cloud in a can. A big copper
cylinder lagged with polystyrene, it looks rather like a cheap boiler. At the
bottom is a heated pan of water, which evaporates and mixes with cooler air
above, producing a mixture that is supersaturated with water.
Like the air in a cloud, this mixture is eager to shed its burden of water
molecules. But to do that, it needs a triggera nucleation site that can
kick-start the growth of snow crystals. When Libbrecht drops a flake of dry ice
in at the top, it seeds a cascade of snowflakes which fall freely though the air,
growing as they go. Finally, they land on a glass plate where a camera records
their size and shape. With this equipment, Libbrecht hoped to test an old idea
about how snowflakes get their diversity.
In 1982, two physicists came up with a model for why the growth rate of a
snowflake changes so dramatically with changing temperature. Toshio Kuroda of
Hokkaido University, and Rolf Lacmann of the Technical University in
Braunschweig, Germany, suggested that tweaking the temperature switches the
growth from one mechanism to an entirely different one.
For snowflakes in a cloud, the theory goes, the critical change happens at around
-15 °C. A little way below this temperature, the molecules have enough energy to
compete with the forces binding them to the crystal below, so the surface
scrunches up into a slightly jagged, disordered state. Then incoming molecules
find a welcoming crevice wherever they land, and growth is fast (see Diagram).
Warm the ice a little, though, and the top few nanometres of the crystal melt
into a disordered, liquid-like layer. No one knows quite why it happens, but the
existence of this "quasiliquid" layer is well established. Without it, ice
crystals wouldn't stick together so easily, and you wouldn't be able to make
snowballs.
Now there are no jagged peaks and troughs, just a smooth ice surface topped with
a quasiliquid layer. Water molecules from the quasiliquid layer may stick briefly
to the ice layer beneath, but because they can form relatively few bonds with
this flat surface, they have enough energy to pop off again and rejoin the
quasiliquid.
The crystal doesn't quite stop growing, though. Every now and then, a molecule
will linger on the surface long enough to be joined by one or two more. United,
the group is a little less likely to leave, and more likely to stay. Once a patch
of molecules has reached a certain size, it becomes stable. New arrivals can
nestle into the edge of the patch, which therefore spreads across the surface of
the crystal. So the crystal grows slowly, in skins.
If the flake teeters back and forth between these two temperatures, it will grow
fast then slow, as the arm-growing mechanism turns on and off. The resulting
complicated, unpredictable series of branchings eventually becomes a beautiful,
classical snowflake.
To make matters more complicated, these two processes occur at different
temperatures on the different crystal faces. At -5 °C, for example, the top and
bottom of the crystal grow fast and the side facets slowly, so you get columns.
At -15 °C, where the opposite happens, you get plates.
At least, that's the theory. But it is almost untested. Scientists disagree about
the temperature at which the quasiliquid layer appears, how thick it is, and how
it affects the growing ice. "Crystal growth in the presence of surface melting is
hard to work out, and very few experiments have been done," Libbrecht says.
Now, he has found a strong hint that Kuroda and Lacmann were right. In a paper
submitted to the Journal of Crystal Growth, he and his colleague Haitao Yu looked
at another of the model's predictions. They describe how growth rates changed as
they held the air in their convection chamber at a steady -5.5°C, and dragged
down its moisture content. Without a quasiliquid layer, growth should slow down
early on as the moisture supply to the surface is reduced. But this doesn't
happen, they found. The crystal continues to grow until the air is very dry
indeedas should happen if the ice surface is sheathed in a water-like layer.
So quasiliquid theory seems to be on the right track. But there are still plenty
of puzzles in the intricate world of the snowflake. Why, for example, are most
plates "sectored", with ridges running out from the centre? And what causes some
of the rarer shapes such as triangles and pyramids?
Libbrecht still has plenty of work to do, if work is the word. Next he wants to
investigate the effect of putting different gases into the air. He reckons that
some gases, such as carbon dioxide, dissolve in the quasiliquid layer and
radically alter crystal growth. Another powerful contaminant is alcohol. "With
just a part in a million of alcohol, growth changes in wild and crazy ways. If
you can smell it, that's enough." So keep your mulled wine covered this
Christmas, or you might be corrupting a million young snowflakes.
Libbrecht is amused by the ways people from different parts of the world react to
his work. "I show this stuff to people from tropical countries, and they say
`OK'. Europeans and Americans think it's pretty good. Canadians say `Oh Wow!'."
And what about Libbrecht himself? Snow studies are only a sideline. His day job
is developing sensitive detectors for LIGO, the huge US experiment designed to
catch gravitational waves from far across the cosmos. So why did he decide to
grow snowflakes in Pasadena? "I have to admit," he says, "the reason it caught my
eye was my background." Ken Libbrecht, it turns out, is not a native of southern
California. He comes from Fargo.
Which kind of snow?
Freezer teaser
* 20 December 2003
* Valerie Jamieson
TIRED of mini umbrellas and sick of olives on sticks? If the cocktails at your
Christmas party are in danger of looking a little passé ths year, Ken Libbrecht
has just the thing for you. Why not try adorning your guests' drinks with "ice
spikes", gravity-defying icicles that sometimes grow out of ice-cube trays.
"They're bizarre things," he says. "People are amazed by them."
Libbrecht, a physicist at the California Institute of Technology in Pasadena, has
recently become something of an expert in the art of growing ice spikes. Last
summer he and his student Kevin Lui spent their days making ice cubes by the
thousand. Their goal was to find out why ice spikes only occasionally rise out of
freezing water.
They seem to have found the answer, or at least a big part of it, and along the
way they have learned how to grow the perfect ice spike. The good news is that
anyone with a freezer can do it.
It all started earlier this year when, out of the blue, someone sent Libbrecht
photographs of frozen needles over a centimetre long protruding from a tray of
ice cubes. For the past six years, Libbrecht had been growing designer snowflakes
in his laboratory in an effort to find out why they form such complex and
delicate patterns. Though he had heard about people waking up on cold winter
mornings to find the odd ice spike sticking out of their bird baths, he hadn't
given the phenomenon much thought. But when he received the photos of tiny ice
towers made in a household freezer, he was intrigued, and tried growing them
himself at home.
At first he had mixed success. Most of the time his ice cubes turned out cubic,
as expected. But now and then, a tall spike emerged from his ice tray. After some
experimenting, Libbrecht hit upon the secret for making as many as four spiky ice
cubes per tray. The trick, he has found, is to use purified water rather than
water straight from the tap. But leaving it at that wasn't good enough for
Libbrecht. "It bothered me why it worked with distilled water and not tap water,"
he says. So he and Lui set out to find out exactly what affects the growth of ice
spikes.
Pop an ice-cube tray filled with water in the freezer and, after about an
hour-and-a-half, the surface begins to freeze. This freezing starts at the sides
of each compartment of a plastic ice tray because they are covered with
microscopic nicks and scratches. Water molecules wedge themselves in these tiny
hollows, where they can form plenty of bonds with their neighbours as the
temperature falls. And because ice crystals are less dense than water, they float
to the surface. The freezing ice then creeps towards the middle until only a
small hole remains unfrozen at the centre of the ice cap (see Graphic).
At the same time, more ice starts forming around the sides of the cube. And since
ice expands as it freezes, the ice below the surface pushes water up through the
hole. If the conditions are just right, the meniscus of water forced out of the
hole freezes around its rim, forming the base of the spike. As this process
continues, the ice spike grows taller until all the water has frozen or, more
commonly, the tip of the tube freezes over. Using a video camera shut inside a
lit freezer compartment, Libbrecht and Lui found that ice spikes grow to their
full height surprisingly quickly, within 3 to 10 minutes.
Libbrecht has used experiments like these to work out why spikes won't form
readily in ordinary tap water. It is all down to impurities. As water freezes
around the top of a growing ice tube, its saltiness increases because the
dissolved minerals and metals do not fit snugly into the ice crystal lattice.
Libbrecht reckons these impurities quickly build up to such high levels at the
tip of the spike that the water there can no longer freeze. Any spikes that begin
to form in tap water will just stall.
To test just how pure the water has to be for ice spikes to form, Lui compared
ice cubes made from distilled water with those made from increasingly salty
solutions of sodium chloride. With as little as 0.2 milligrams of salt added per
litre of water, the chance of an ice cube producing a spike plummeted from 1 in 5
with distilled water to less than 1 in 20.
And since tap water typically contains 100 times this concentration of various
salts, it is hardly surprising that ice spikes are so rare. So if you want to
grow your own ice spikes, you'll need distilled water like the kind sold in
supermarkets for pouring into your steam iron or topping up your car battery.
What else do you need to watch out for? Though Lui managed to grow ice spikes in
dozens of different kinds of freezers, from those found in labs to those found in
student dormitories, he found that temperature does make a difference. At -7 °C,
half the ice cubes turned spiky. If the temperature plunges, however, so does the
likelihood of finding an ice spike. Only 1 in 10 cubes will grow a spike at -15
°C. Libbrecht isn't certain why, but he suspects that in such cold conditions the
tip of the embryonic spike freezes shut before it has had a chance to grow. So if
your ice cream is really hard, your freezer is too cold to make many ice spikes.
Having a modern, frost-free freezer helps too. They hardly ever need defrosting
because a fan circulates cold, dry air. The moving air chills the edges of the
water droplet perched on top of the growing ice spike faster than in calm
conditions. This faster freezing rate at the tip promotes the growth of longer
ice spikes. "It also works better if the freezer is empty," says Libbrecht.
That's because all those pizzas and bags of frozen peas stop the air from
circulating freely.
But the good advice doesn't stop there. If you want prizewinning spikes, use a
plastic ice cube tray rather than an old-fashioned metal one. When Libbrecht
spotted aluminium ice cube trays for sale on eBay, he knew he had to try growing
ice spikes from them, but hardly any formed. Metal is such a good conductor of
heat that the surface of the water freezes over quickly, completely sealing the
hole from which the spike would normally grow. Plastic has just the right amount
of insulation for ice spike formation.
Soon after they published their findings in October
(www.arxiv.org/abs/cond-mat/0310267), Libbrecht and Lui realised they had started
a craze. Reports that their tallest ice spike was 5.6 centimetres long were like
a challenge for people who had become hooked on ice spikes. Soon Libbrecht
received an email from an enthusiast who distilled his water a second time to
purify if further. "Using a cereal bowl filled with double-distilled water, he
grew an ice spike measuring 10 centimetres long and 1 centimetre across,"
Libbrecht says.
It may sound like a lot of trouble to go to for your Christmas party, but it's
time well spent. After all, spikes are the perfect ice-breaker.
The sinister side of the holly and the ivy
* 25 December 1999
* Lynn Dicks
DECK the halls with boughs of holly. Drape the mantelpiece with tendrils of ivy.
And hang out a sprig of mistletoe for festive harmony.
Bringing some of the outdoors inside is all part of the Christmas tradition. In
Western society the leaves of holly, ivy and mistletoe are hugely symbolic. But
take a closer look at these traditional festive plants. Were the ivy's jagged
heart-shaped leaves really designed to curl so delightfully around your banister
rail, and the holly's prickles put there just to pretty up your porch? And are
mistletoe's fleshy green lobes nature's invitation to make free with whoever you
please? For the real story behind this seasonal foliage, you must look to the
harsh outdoors. It is all a question of survival-leaf shape can make the
difference between life and death.
Leaves are probably the world's most attractive factories. Here the complicated
business of photosynthesis occurs, with energy from sunlight harnessed to turn
carbon dioxide from the air into sugars. Being thin and flat allows leaves to
expose the maximum number of cells to air and light. But they must also be held
erect if they are to harvest sunlight effectively, and that's where shape comes
in.
A leaf is like a sheet of fabric held up to the Sun on a skeleton of mechanical
struts: the veins. To make this system efficient, the plant needs to minimise the
amount of structural support per unit area of leaf tissue. The simplest solution
is to have one main strut-the midrib-running down the middle of the leaf, with
secondary struts going out to the edge. Each section of midrib supports the
tissue on either side of it. But the further away you go from the midrib's
attachment point, the longer the "lever", and so the greater the effective
weight. Try holding a heavy book at arm's length, and you'll see the principle.
By tapering towards the tip, the leaf can counteract this effect, allowing the
entire length to be held erect by a single central strut. Tom Givnish from the
University of Wisconsin, Madison, has examined the structural mechanics of
leaves. "If mechanical efficiency were the only consideration," he says, "plants
would all have triangular leaves."
Of course, mechanics is not the only consideration. There are other things a
plant has to think about, like how to arrange its leaves so they don't block each
other's light. "Triangular leaves can't be held efficiently along twigs to
harvest sunlight," says Givnish, "because triangles don't pack. But if the base
of the leaf is tapered as well, to a sort of kite-shape, then they can be held
close together in a circle, or spiral, without overlapping." What Givnish
describes is the basic shape of many leaves. Mistletoe for instance, is a
variation on it. So too is holly, if you ignore the spines.
So why aren't all leaves this shape? And how do you account for the subtle
differences between the shapes of leaves that do fit the model? It all depends on
exactly what conditions a plant finds itself in-the climate, the exact location,
the life cycle and the risk of being eaten can all heavily influence leaf shape.
Take holly, for example. "The holly bears a prickle, as sharp as any thorn," goes
the carol. The prickles are certainly a prominent feature of most holly leaves,
but have a closer look at those high up at the top of a holly tree. Often they
are not spiny. This is a clue that the holly's prickles have evolved to protect
it against plant-eating animals such as deer. Only those leaves within reach of
browsing muzzles are spiked to give large herbivores a meal they won't forget.
But prickles are expensive to produce. To understand why it is worth it for
holly, you need to look at the tree's life cycle. Holly is an evergreen, but it
lives among deciduous trees that lose their leaves in winter. So for half the
year one of the few sources of food for browsing animals is holly leaves. It is
also a fairly short tree and easily accessible, so it needs extra protection to
prevent itself from being totally stripped of its leaves. "All hollies that live
as evergreens in deciduous forests are spiny," says Peter Grubb from the
University of Cambridge. "There are deciduous hollies in North America and Asia
that are not spiny at all." And if that doesn't convince you, consider the
species of oak that are evergreen. Deciduous oaks tend to have soft, lobed
leaves, but most evergreen ones have spiny leaves just like holly.
Other plants grow sharp thorns on their stems to keep predators at bay, but
prickly leaves are a much more direct deterrent. Evergreens have what it takes to
develop this defence strategy because their leaves must be tough and thick enough
to survive frosts, and heavily waxed to prevent water loss at times when
groundwater is frozen. "These stiff leaves form a solid backing for the spears,
so they can really inflict some damage inside the mouth," says Givnish.
Ivy, on the other hand, makes itself unpalatable with toxins, but its leaf shape
is more of a conundrum. With three or five large lobes, it is strikingly
different from the basic kite-shaped leaf. "A great number of climbing plants
have leaves something like this, with a heart-shaped base," says Grubb. Think of
bindweed or grapevines. The crucial thing is the way the plant grows. These are
plants that do not provide their own support, but cling to other plants.
"A climber needs its leaves to be facing out sideways, to catch light," says
Grubb, since the supporting tree will take most of the light from above. So the
leaf is held at a right angle to its stem, instead of in the same plane. The most
efficient way to do this is for the midrib to originate near the middle of the
leaf, with veins going out to the edges like spokes. Small forest floor plants,
such as violets, also have this kind of leaf shape, because their leaf stems grow
directly out of the ground.
The amazing thing about ivy is that when the plant starts to flower, the leaves
revert to the standard shape. "As it pushes the flowers out into space to attract
insects, the shoots become self-supporting and the leaves are spirally arranged
and shaped the same as many other trees," says Givnish. They are held in the same
plane as the leaf stem, and often have full light from above.
But there is another dimension to this, which may also explain the different leaf
shape on the flowering shoots of ivy. The normal ivy shape is only good in shady
conditions, where the temperature tends to be low and water loss is not a
problem. Plants cannot avoid wasting water because it evaporates from the leaves
through the holes that allow air to enter for photosynthesis. "If you look around
in a forest," says Grubb, "you'll notice that the climbing part of ivy never
grows right to the top of the crown. It always stops short before it is exposed
to full sunlit conditions. In fact, no plants in hot, dry places have this broad,
heart-shaped leaf form."
Givnish believes the explanation lies in the film of stagnant air that clings to
any leaf surface. This boundary layer, as it is called, is thicker in a broader
leaf. "The boundary layer directly blocks heat loss," Givnish explains, "so in
sunny conditions, a broader leaf will get warmer, and more water will evaporate
per unit area than from a narrower leaf." Grubb has a different theory. He
suspects it is something to do with the difficulty of getting water from the
midrib to the leaf's edge, if this is a long way away from the middle.
Either way, the pattern is clear. Plants in dry sunny places usually have small,
narrow leaves. Under the shady canopy of woodland, plants such as ivy are free to
have a shape that is easier to support. The only truly round leaf is the water
lily, which holds its leaf perpendicular to the stem, but also never has a
problem with water supply because it is bathed in it all the time.
Mistletoe is another plant that doesn't bother with water conservation. There are
more than a thousand species around the world and all are hemiparasitic-they grow
directly on other plants, tapping into the plumbing of their host to extract
water and nutrients, but use photosynthesis to produce their own sugars. "Because
they are water parasites, mistletoes have to be water spenders," says Peter
Bannister from the University of Otago in New Zealand. "They have to produce a
water deficit, so that water flows from the tree into them." This explains why
mistletoe doesn't have a thick waterproof coating on the top of its leaves, like
holly. "Many of them are also more succulent, or fleshy, than their hosts," adds
Bannister. Because they keep drawing water even when they do not need it.
The shape of mistletoe leaves varies considerably. About half of mistletoe
species in Australia and New Zealand have leaves that look like those of their
host tree. One, for example, has a eucalyptus-like leaf, while another, living on
a tree with needle-like leaves, has very reduced leaves too. A possible
explanation is that chemicals such as plant hormones pass from the host to the
mistletoe and affect leaf shape. But there is little direct evidence for this,
and the weight of opinion is with an alternative idea-mimicry. These mistletoes
have to contend with tree-dwelling herbivores such as possums, sloths and
monkeys. The animals are implicated in one of the most bizarre effects in plant
biology. The mistletoes, it seems, are disguised as the tree to avoid being
eaten.
At first Bannister was sceptical of this idea. "I thought it was more likely to
be to do with the plants experiencing the same physical environment," he says.
But his investigations and those of Jim Ehleringer from the University of Utah,
Salt Lake City, have shown that the mimicking mistletoes have a special reason to
avoid being spotted. They contain higher levels of nitrogen than their hosts.
Nitrogen is a very important resource for herbivores, and some animals actively
select nitrogen-rich plants. So nitrogen-rich mistletoes would have been under
greater pressure to avoid detection.
In the northern hemisphere, mistletoe does not mimic the host's leaves. But then
look at the trees they choose to parasitise. The Australasian trees are mostly
evergreen, whereas in temperate climates the host trees are usually deciduous.
There is little point in cunningly disguising yourself as the leaves of your host
if in the winter your tree loses its leaves and you are left standing out a mile.
So when you're hanging your holly wreath, or kissing under the mistletoe this
Christmas, consider the leaves with new respect. To a plant, a leaf is no mere
adornment: it is a vital piece of anatomy. And be thankful for the variety of
strategies and situations in the plant world. Imagine how dull your wreaths and
arrangements would be if all leaves were triangular.
Festive decorations drive the plundering of moss
* 25 December 2004
* Gail Vines
BOUGHT a classy Christmas wreath this year? Then chances are that tucked away
amidst the boughs and the berries you will find the desiccated remains of a moss
- harvested, perhaps, on the other sideof the planet.
"Once you start noticing, you see wild-harvested moss everywhere," says Patricia
Muir from Oregon State University in Corvallis. Even that green carpeting under
the nativity scene could be "sheet moss", sold by the yard and rolled up like
bolts of cloth. The moss's feathery fronds have been glued to a fabric backing,
dyed a lurid green and sprayed with fire retardant. And this stuff doesn't just
turn up in Christmas decorations; it can be found everywhere from funeral
parlours to airports, motor shows and the lobbies of elegant hotels.
In the past decade, consumers with an eye for the "natural" have unwittingly
fuelled a fast-growing trade in mosses. As moss is not yet grown commercially,
this demand can only be met by plundering nature's store. And no one really knows
how big the industry is. "That's part of the problem," says Muir. Her latest
study shows that it must be worth at least $5.5 million a year in the US, and
could be as much as 30 times that amount, given that harvesting carried out under
permit is just the tip of the iceberg. Mosses have always been put to good use
(see "Not just for Christmas"), but a recent boom in demand threatens woodlands
and moorlands worldwide.
New Zealand was one of the first countries to cash in. The decorative moss
industry took off almost by chance in the 1980s, when a Kiwi promoting his native
goods in Tokyo covered his stand with dried sphagnum moss. To his surprise, he
soon received a NZ$400,000 (about US$230,000) order - for 12 container loads of
moss for the Japanese floral trade, particularly for orchid growers. Overnight,
sphagnum became a major export. By 1990 some 700 tonnes of dried sphagnum, worth
NZ$10 million, was being shipped abroad every year. In recent years the export
trade has been valued at NZ$18 million annually. And some New Zealanders have
recently teamed up with Chilean entrepreneurs to begin sphagnum harvesting at
Puerto Varas in southern Chile.
It takes 15 wet tonnes to produce 1 tonne of dry moss, so harvesting it is a
major operation. Helicopters have even been drafted in to lift sphagnum from
swamps in the southern and western parts of the South Island. The moss is
harvested from private land or from swamps leased by the Department of
Conservation and deemed to be of low conservation value. However, the ecological
importance of moss is a moot point. A recent report by the Ministry of
Agriculture and Forestry concluded that "the level of harvest of sphagnum moss
determined to be sustainable is unknown".
Home-grown bounty
Today dried moss from New Zealand is imported to the UK preformed into liners for
hanging baskets. But the UK home-grown trade is expanding quickly, according to
Alison Dyke of the non-governmental organisation Reforesting Scotland. What was
once a cottage industry is becoming commercialised. Wild moss is proving to be a
lucrative forest product which, along with pheasant shooting, rivals the value of
the timber itself. On a good site a "mosser" can fill 400 bags in a day, with
bags selling at £1 each. One Welsh firm shifts around 50 truckloads of moss and
foliage each year. In the UK, most of the legal collecting tends to be restricted
to the parts of conifer plantations earmarked for clear-felling. Much harvesting
is on a modest scale and supplements the livelihoods of local farmers and
forestry workers, says Helen Sanderson from the Royal Botanic Gardens at Kew,
London. "But illicit collecting on moorland and in mixed semi-natural woodlands
is worrying," she says.
In the US, alarm bells are already ringing. Here, the burgeoning trade in wild
moss is concentrated in the deciduous woodlands of the Appalachian mountains in
the east and the temperate rainforests of the Pacific north-west. The moss in the
rainforests is epiphytic, meaning it grows on trees, and the area boasts
luxuriant mats of moss and liverworts dripping from the branches of huge old
trees. Twenty years ago this bryological bounty was exploited modestly, mostly by
self-employed locals who collected moss as a stopgap between logging or fisheries
work. Since the early 1990s, however, the locals have been sidelined by labour
contractors who bring in crews of poorly paid immigrant workers to strip whole
sections of forest. Up to 40,000 tonnes of moss are now being removed from US
forests every year, Muir says.
"Markets are driving what is happening on the ground," says Rebecca McLain, a
policy analyst at the Institute for Culture and Ecology in Portland, Oregon. A
few controlling companies buy up most of the harvesting leases then sublease to
labour contractors. "You can't blame any individual, they are all trying to make
a living," says McLain. "The problem lies in the way the system is structured."
Big, short-term leases encourage over-exploitation, and the supply chain
exacerbates the situation. The gang-harvested moss is sold on to garden centres
and florists, which tend not to ask where it came from or how it was collected.
"Until the floral industry starts to worry about its green credentials and
consumers become more discerning, things are not going to change," Dyke says.
Collectors do target common mosses, but they can't help gathering up rarer
species too, says Susan Studler of the West Virginia University in Morgantown. In
one typical 100-kilogram load, along with the two or three common species of
feather moss that were the collector's quarry, she found 75 different species of
moss and lichen as well as several rare ferns. Hundreds of invertebrate species
and even young salamanders are also scooped up. "This high 'incidental take' of
species is what particularly concerns me," Studler says.
In an attempt to control the trade, forest managers have banned collecting in
some places, but government authorities don't have the manpower to enforce their
own rules. Besides, tighter regulations on public land seem to have intensified
harvesting in the remaining forests, worsening the ecological impact, according
to JeriLynn Peck of the University of Minnesota, St Paul, a pioneering researcher
on the US moss trade. She believes that not all moss harvesting is unsustainable,
but that exploitation at present rates could destroy natural ecosystems that have
taken years to evolve. "Experimentally harvested plots suggest that some mosses
need at least 10 years and probably as many as 30 years to regrow," she says.
Worse, epiphytic mosses may only be able to colonise the rough young twigs of
saplings, not the smooth branches of veteran trees. If that is true, these moss
mats are as old as the trees themselves - hundreds of years old in many cases.
"By definition this is an unsustainable harvest," says Robin Hall Kimmerer from
the State University of New York at Syracuse, "and the loss will have
consequences we cannot foresee."
Mosses can hold 10 times their weight of water. In the forest they act as
slow-release sponges, buffering the flow of water and nutrients. They are the
forest's seedbeds, form insulating and antiseptic nest liners for birds and
mammals, and provide sources of food and shelter for thousands of creatures.
Salamanders breed and feed in moss mats, for example, and in turn become food for
animals higher up the food chain. Remove the moss - a major link in a web of
interactions - and the whole ecosystem could be disrupted.
No one knows whether it will prove possible to regulate moss harvesting. One
telling case study reveals that even small-scale removal may cause damage.
Researchers accompanied an extended family of 10 people living in the mountains
of Mexico as they gathered moss destined for Christmas nativity scenes. In the
1996 season the collectors removed 50 tonnes wet weight of moss from the forest
floor. They harvested the moss patchily, only taking about 2 per cent of the
total surface area. That may be sustainable, but with the moss they inadvertently
gathered the seedlings of fir trees (Bryologist, vol 104, p 517). As a result,
the researchers conclude, the harvest could threaten the long-term regeneration
of the forest. Worse still, it jeopardises a flagship protected species, because
these are the very trees that provide the winter resting place for monarch
butterflies after their famous annual transcontinental migration.
Green-nosed reindeer
With enough ecological knowledge and plenty of determination on the part of
governments and conservationists, it may be possible to control the excesses of
big industrial harvesters and balance forest conservation with local livelihoods.
But that will inevitably take time. In the meantime, we the consumers should
consider our responsibilities. Mosses may look good in Christmas decorations, but
is it worth it? Kimmerer is certain it is not. This is like witnessing "an
antique tapestry ripped to shreds and stuffed in a bag", she says. "All this
destruction - and for what?" Kimmerer is horrified to find that in upstate New
York you can buy green teddy bears and life-sized reindeer made of wire frames
stuffed with Oregon moss. "The time to be a bystander has passed," she says.
Not just for Christmas
The commercial trade in mosses is new, but our resourceful forebears have relied
on the little green fronds for millennia
For restful slumbers
Sleeping on a pillow stuffed with hypnum moss was said to bring sweet dreams.
Linnaeus, the father of modern plant taxonomy, spoke highly of the bedroll of
polytrichum moss he enjoyed while travelling with the Sami people of Lapland.
Foot salve
The 5200-year-old body of the Ice Man discovered in a melting Tyrolean glacier in
1991 was wearing boots packed with mosses, including species found only in
lowland valleys 100 kilometres away. Today, odour-eating liners for walking boots
sometimes contain a layer of sphagnum moss.
Weapon of war
Legend has it that Spanish Christians used moss to hide from the Moors outside
the western town of Béjar. After covering themselves with the plant, they crept
to the foot of the Moorish fortress and lay disguised as rocks. When the gates
were opened, the moss men sprang up and defeated the unsuspecting guards.
Natural bubble wrap
Resistant to rot and mould, moss is an ideal packing material. The cemetery lawns
of New York state have been liberally colonised by one European moss species that
probably arrived in the late 1800s packed round imported nursery plants.
In the bathroom
Able to soak up many times its own weight in water, moss has long been put to
good use as nappies (diapers), toilet paper and sanitary protection.
Wound dressing
Moss extracts are antiseptic and can fight fungal skin infections. In both world
wars, when conflict disrupted supplies of cotton from Egypt, sphagnum moss was
collected for the Red Cross and sent to the front to pack soldiers' wounds.
Meltdown
* 19 December 1998
* Gail Vines
EACH year millions of people send greeting cards bearing images of what is, let's
face it, just a couple of balls of snow. Not that manufacturers are complaining:
snowmen are good for business. Increasingly standardised, depictions of these
smiley chaps with their carrot noses, bright scarves and bedraggled hats can
shift not only cards but a wide assortment of Christmas decorations, not to
mention confectionery, books, videos and soft toys. Today, the snowman is up
alongside Santa as a secular icon of Christmas, at least throughout northern
Europe and North America. But what is he doing there?
As a figure of jollity and fun, the snowman undoubtedly contributes to the
carnival air of the Christmas festival, argues Tricia Cusack, who lectures in
history of art, architecture and design at the University of Birmingham. The
snowman's intrinsic good humour is captured by his French appellation: he is
"bonhomme de neige". His rotund body conveys an air of bacchanalia, of
celebratory overindulgence. But snowmen do a lot more symbolic work besides,
Cusack contends.
For a start, by simply standing out there alone in the cold, the snowman provides
the perfect contrast to the putative seasonal warmth of the family within.
Fantasies about perfect families are central to Christmas iconography these days,
and here images of snowmen can do double duty. "As one of the minor household
gods at Christmas," says Cusack, "the snowman both enhances the element of
fantasy and magic for children and reminds adults of childhood."
If so much seems benign, there is more that is less so, says Cusack. Snowmen may
look innocent, but nowadays, even they cannot escape connotations of class,
gender, and even "race". Social commentators have noted that the Christmas
festival can seem a rather "white" affair, exacerbated, perhaps, by the very
whiteness of the snowman himself.
Gender, however, is undoubtedly at the heart of the snowman phenomenon. Snowmen
look androgynous but are presumed to be male, says Bernard Mergen. A historian at
George Washington University, Mergen is one of a select band of scholars who have
made the cultural significance of snow their specialist subject. "Woody Allen
cleared up the ambiguity in his movie Radio Days, when he had two boys decorate
their snowman with a carrot penis," says Mergen. "Reports of anatomically correct
nude snowmen regularly appear in the press." Occasional images of snow-women are
seen as funny, precisely because they overturn gender expectations.
So what sort of a man is this? The combination of the snowman's masculinity and
his "ritual location in the semi-public space of garden or field" is telling,
Cusack contends. It's no accident that the Victorian promotion of Christmas as a
family-centred celebration went hand in hand with the ideology that a woman's
place is in the home. Traditional celebrations of Christmas underline women's
supposed role in the domestic sphere, while the snowman presents an image of
masculine control of public space. "The snowman's presence is a reminder of
masculine dominance and predominance outside the home," argues Cusack. It becomes
"a household god keeping nature in orderit represents masculine ordering and
surveillance."
Despite this, the snowman remains essentially an outsider, excluded from the
family circle. Traditional Christmas scenes show a solitary snowman viewed
through a window from the warmth of a roaring hearth. Cusack argues that as well
as being a symbol of male dominance, the snowman can also represent a potential
object of charity. No wonder he has so few accessories and a Dickensian hat. She
suspects that the Victorians enjoyed the snowman as a symbolic outcast, available
to be the recipient of a new red scarf. "The snowman, cared for, smiles back, and
the family within gain satisfaction both from their cosiness and their charity."
But if Cusack sees England's Victorian underclass in today's snowmen, Mergen
points to a more subversive role for the snowmen built on the streets of American
cities in the 19th century. Kitted out with a tall stovepipe hat or a derbyboth
of which bespoke wealth and social pretentionsthe traditional American snowman
was, on the whole, "a symbol of authority to be attacked", Mergen concludes.
Unwittingly, perhaps, Daniel Carter Beard, one of the founders of the Boy Scouts
of America in the 1880s, promoted the building of snowmen as a wholesome activity
for young boys, who were supposed to confine snowballs to those harmless targets.
Intent on more subversive activity, the youths made snow effigies of male
authority figures and then destroyed them.
Carrots and sticks
The sociology of snowman-building today remains shockingly under-researched,
despite an exhaustive catalogue of the materials used in the construction of
snowmen by two American scholars, Avon Neal and Ann Parker, in the late 1960s.
According to their investigations, eyes can be fashioned out of chunks of coal,
shrivelled apples, stones, bolts, electrical fuses, bottle caps, champagne corks,
batteries, buttons and nutshells. Additional accoutrements for mouths include
twigs, pebbles, rusty horseshoes, false teeth and possibly a pipe. Carrots tend
to be favoured for noses, but corncobs, sticks and clothes pegs have also served
that purpose, while in Raymond Briggs's celebrated children's story and animated
film, The Snowman, a clementine (or similar citrus fruit) serves as nasal
equipment. Hints of nakedness are offset by the provision of a row of "buttons".
The finishing touches are provided by a scarf and, most famously, a hat, or at a
pinch a hat substitute such as an old pot.
Tradition, tradition
A straw poll of half a dozen embassies in London suggests that snowmen thrive in
countries as diverse as Sweden, Germany, Russia and Japan. "It is traditional to
use coal for the eyes," says the spokeswoman at the Swiss Embassy, "but these
days it can be difficult for children to find." The Russian press officer said
that buckets made good substitutes for hats, which are presumably all in use on
human heads. Carrots for noses are universally favoured. Indeed, one enterprising
British company in West Sussex has marketed "Grow Your Own Snowman" packets,
which on closer inspection turn out to contain carrot seeds. "We had planned to
offer you the opportunity to grow your own Frozen Friend with our amazing
patented whizzo F111 hybrid Sno-seeds, the result of crossing a snowdrop with a
mangel wurzle in sub-zero conditions," the packaging explains. "Unfortunately,
all the seeds melted on the way to the toy factory. So instead we have
substituted carrot seeds."
Yet, jokey vegetables aside, there's a hint of menace about snowmen. In Frosty
the Snowman, a hit song of the 1950s, children run to follow Frosty to the town
square, where he evades a policeman and then disappears. His anarchic behaviour
befits someone made of snow, says Mergen, which is "paradoxically hard and soft,
substantial yet ephemeral".
Briggs's snowman also becomes a touch frightening when he subverts his accepted
status as an outsider and comes inside the house. As the parents sleep, he makes
mischief with their property, even trying on a set of false teeth soaking by the
bedside, and then flies away with their underaged son.
Perhaps our ambivalence to snow is showing. Could it be that we make snowmen look
so friendly to compensate for our intrinsic fear of all that white stuff falling
from the sky? Humans may have sought to assert their dominance over snow by
shaping it in their own image, argues Mergen.
But if the snowman is in some way a suggestion that nature can be enjoyed but
also tamed and controlled, his demise as winter gives way to spring reasserts the
natural cycles of death and rebirth. Even The Snowman ends with the main
protagonist reduced to a hat in a puddleno wonder the haunting theme music is in
a minor key.
Poets have written of the snowman's plight, seeing him as Everyman, doomed to
transience, who, according to the Canadian poet P. K. Page, eventually melts away
into a "landscape without love". As his snowmen melted, they "greyed a little
too, growing sinister and disreputable in their sooty fur", he wrote in The
Snowman. And in Wallace Stevens's bleak poem of 1921, also called The Snow Man,
he evokes "the listener, who listens in the snow, and nothing himself, beholds
nothing that is not there and the nothing that is". In Mergen's view, Wallace's
snowman is a quintessential 20th-century American.
American novelty shops sell plastic snow domes, filled with bits of plastic snow,
lumps of coal, a hat and a carrot, entitled "California snowmen". In an age of
global warming, will we come to see the snowman's destiny as a potent symbol of
our collective future?
Perhaps the human genius for self-destruction is best symbolised by one card on
sale in Britain this Christmas: it shows three gleeful snowmen gathered round a
roaring brazier, warming themselves by the fire.
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