[Paleopsych] Re: Hawking surprises GR 17

Joel Isaacson isaacsonj at hotmail.com
Fri Jul 16 18:47:15 UTC 2004

>From: "Werbos, Dr. Paul J." <paul.werbos at verizon.net>
>Reply-To: The new improved paleopsych list <paleopsych at paleopsych.org>
>To: The new improved paleopsych list <paleopsych at paleopsych.org>,   
>HowlBloom at aol.com
>CC: paleopsych at paleopsych.org
>Subject: Re: [Paleopsych] Re: Hawking surprises GR 17
>Date: Fri, 16 Jul 2004 08:07:24 -0400
>My personal view --
>The world is learning a lot here about the internal logic of a nice 
>mathematical world.
>This is not the first piece of big news. (Forgive me for feeling an analogy 
>to the big news the TV also reports about
>Brittany Spears, who is also good about such things.)
>The second edition of the short history of time repudiated the most 
>interesting insights of the first.
>Huw Price (whose stuff is worth googling) was clearly very disappointed, 
>and I agree with his assessment.
>The best stuff received slight frowns from the establishment and the vested 
>interests, and the eagerness
>with which Hawking accommodated illogic... well, it reminds me of 
>discussions I have had with my wife about
>George Tenet.
>Back to the trenches...
>    Paul

Yeah...  Huw Price's problems with Hawking go back to 1989...  following is 
a delightful
paper by Price  =======>>>>

[Draft of an article published as ‘A Point on the Arrow of Time’, Nature, 20 
July 1989, 181-182.]
Huw Price
One of the outstanding achievements of recent cosmology has been to offer 
prospect of a unified explanation of temporal asymmetry. The explanation is 
in two main
parts, and runs something like this. First, the various asymmetries we 
observe are all
thermodynamic in origin – all products of the fact that we live in an epoch 
in which the
universe is far from thermodynamic equilibrium. Second, this thermodynamic
disequilibrium is associated with the condition of the universe very soon 
after the Big
Bang – the essential point being that in the rapidly expanding universe of 
the time, gravity
is able to create organisation much faster than other processes can destroy 
it. The stars,
galaxies and other forms of organisation we find in the present universe are 
all products of
this early period. Such concentrated energy sources themselves make possible 
the kinds
of asymmetric phenomena with which we are most familiar, such as life 
If this explanation proves to be right it will surely rank as one of the 
impressive achievements in the whole of natural philosophy. Where else do we 
find this
breathtaking scale, this extraordinary conjunction of fundamental physics, 
the first
moments of Creation, the possibility of life and the basic character of 
human experience?
And it is very much a contemporary achievement: even if its roots go back on 
one side to
the investigation of time asymmetry in nineteenth century statistical 
mechanics, and on the
other to Hubble's discovery in the 1920's of the expansion of the universe, 
the body of the
picture has only begun to be filled in in the last twenty or thirty years. 
This fascinating
story has recently been given some well-deserved publicity in Stephen 
Hawking's bestseller,
A Brief History of Time (Bantam, 1988) – well-deserved, not least, because
Hawking himself is responsible for a considerable part of the story as it 
presently stands.
Hawking's book is a clear and exciting guide to the recent search for a
cosmological understanding of temporal asymmetry – a scientific thriller. 
Despite its
merits, however, I think it commits one of the worst sins of that literary 
genre. The last
pages offer us a surprising denoument, but fail to explain its most puzzling 
aspect. It is as
Page 2
if we are assured that the butler did it, without being told how he overcame 
the evident
obstacles (the fact that he was already incarcerated in Wormwood Scrubs at 
the time, for
example). If the omission goes unnoticed by the casual reader, it is simply 
because he or
she has not been told enough of the story to see that the climax is so 
surprising. Such a
reader is doubly deprived, for mystery is the heart of a good detective 
In the case of the story of cosmology and temporal asymmetry, the mystery 
lies in
the fact that the attempt to explain thermodynamic asymmetry in terms of the 
expansion of
the universe from the Big Bang seems to lead to an inevitable and 
unpalatable dilemma. I'll
describe this dilemma in a moment. In effect, it's rather as if the clues 
overwhelmingly to two possible suspects, but one turns out to have a perfect 
alibi and the
other to have no possible motive. We can see perfectly well what the two 
solutions are, but individually they both seem untenable. Hawking's popular 
account of his
own contribution serves to mark this dilemma, in that he describes how he 
was led to
change his mind about which of the possible conclusions is the right one. In 
the process,
however, he appears to gloss over the difficulty that has long plagued the 
conclusion he
finally opts for. So it is not clear whether he has found some way around 
this difficulty, or
whether he has perhaps overlooked it. Either way, some clarification seems 
in order.
The dilemma stems from the fact that the universe may not always expand. If 
density of matter is sufficiently great, gravity will eventually reverse the 
expansion, and the
entire universe will collapse to a black hole. What would then happen to 
entropy? Would
entropy decrease as the universe contracted? Or would it go on increasing, 
to reach its
maximum value in the final singularity? Both answers have seemed 
unsatisfactory, though
for quite different reasons.
The problem with the former answer is that it seems to entail that all the 
time asymmetries would be reversed as the universe begins to contract. The 
would enter an age of miracles. Radiation would converge on stars, apples 
would compose
themselves in decompost heaps and leap into trees, and humanoids would arise 
from their
own ashes, grow younger, and become unborn. These humanoids wouldn't see 
things this
way, of course. Their psychological time sense would also be reversed, so 
that from their
Page 3
point of view their world would look much as ours does to us. The difficulty 
really lies in
managing the transition. They lie in our future, as we lie in theirs. 
Various sorts of
paradoxes seem to arise in the middle. I won't try to describe these 
problems here.
(Interested readers may consult P. C. W. Davies, The Physics of Time 
Surrey University Press, 1974, particularly sections 4.5, 5.6 and 7.4; and 
R. Penrose,
'Singularities and time-asymmetry', in Hawking and Israel, (eds.), General 
Relativity: An
Einstein Centenary Survey, Cambridge University Press, 1979, pp. 581-638, 
12.2.6.) For the moment let me simply note that we can't avoid the problem 
by supposing
(as on present evidence may well be the case) that the universe never 
contracts. Even if the
universe as a whole never re-collapses to a singularity, there is now a very 
strong case that
parts of it do, as certain massive objects collapse to black holes. Does 
entropy decrease in
these cases? If we say that it does, the same sorts of paradoxes seem to 
What then of the alternative answer, namely that entropy does not decrease 
as one
approaches a future singularity (either the collapse of the universe as a 
whole, or the
collapse of some part of it)? The problem with this answer is that it makes 
it mysterious
why entropy does decrease in the other direction, as one approaches the 
singularity at the
beginning of the universe. The difficulty stems from the time-symmetric 
character of the
physical theories involved. If these theories imply that entropy was low in 
the region of
this initial singularity, then in virtue of their time-symmetric character, 
it seems that they
should also imply that entropy will be low towards a final singularity – 
i.e., that entropy
decreases as the universe contracts. So if we reject that option, we seem 
forced to conclude
that physical theory does not explain the low initial entropy of our 
universe. We can't
explain temporal asymmetry, in other words, but simply have to accept it as 
an extratheoretical
'initial condition'.
This then is the dilemma: either we have to admit reversal of the 
arrow of time in the case of local or universal gravitational collapse; or 
asymmetry turns out to be inexplicable after all, since we can't account for 
the low initial
entropy of the universe as a more or less inevitable consequence of our best 
theory of the universe as a whole. The dilemma is particularly acute for 
Hawking, for he
Page 4
has an additional reason to avoid resorting to unexplained boundary 
conditions. For him
their effect is not simply to make time asymmetry inexplicable. They also 
conflict with the
spirit of his 'no boundary proposal', namely that one restrict possible 
histories for the
universe to those that 'are finite in extent but have no boundaries, edges, 
or singularities.'
(BHT, p. 148)
Hawking describes how initially he thought that this proposal favoured the 
horn of the above dilemma: 'I thought at first that the no boundary 
condition did indeed
imply that disorder would decrease in the contracting phase.' (BHT, p. 150) 
He changed
his mind, however, in response to objections from two colleagues: 'I 
realized that I had
made a mistake: the no boundary condition implied that disorder would in 
fact continue to
increase during the contraction. The thermodynamic and psychological arrows 
of time
would not reverse when the universe begins to contract or inside black 
holes.' (BHT, p.
150) In an earlier article in New Scientist (9 July 1987, pp. 46-9) Hawking 
describes his
change of mind in this way: 'I then realised that although it was possible 
for the Universe
to contract back to a smooth and ordered state, it was much more likely to 
contract to a
very disordered state, because there are so many more disordered states. 
Thus the
thermodynamic arrow of time will not reverse. It will continue to point in 
the same
direction.' (p. 49)
This change of mind enables Hawking's proposal to avoid the difficulties
associated with reversing the thermodynamic arrow of time. What is not clear 
is how he
avoids the alternative difficulties associated with not reversing the 
thermodynamic arrow of
time. That is, Hawking does not explain how his proposal can imply that 
entropy is low
near the big bang, without equally implying that it is low near the 'big 
crunch' (or in a
black hole). The problem was to get a temporally asymmetric consequence from 
symmetric physical theory. Hawking suggests that he has done it, but doesn't 
explain how.
Readers are entitled to feel a little dissatisfied. As it stands, Hawking's 
account reads a bit
like a suicide verdict on a man who has been stabbed in the back: not an 
impossible feat,
perhaps, but we'd certainly like to know how it was done.
Page 5
To my admittedly unqualified eye, there seem to be three possible 
resolutions of
this mystery. The first, obviously, is that Hawking has found a way round 
the difficulty,
but hasn't told us what it is. I think that the easiest way to get an idea 
of what he would
have to have established is to think of three classes of possible universes: 
those which are
smooth and ordered at both temporal extremities, those which are ordered at 
one extremity
but disordered at the other, and those which are disordered at both 
extremities. If Hawking
is right, then he has found a way to exclude the last class, without thereby 
excluding the
second class. In other words, he has found a way to exclude disorder at one 
extremity of the universe, without excluding disorder at both extremities. 
Why is this
combination the important one? Because if we can't exclude universes with 
disorder at
both extremities, then we haven't explained why our universe doesn't have 
disorder at both
extremities – we know that it has order at at least one temporal extremity, 
namely the
extremity we think of as at the beginning of time. And if we do exclude 
disorder at both
extremities, we are back to the answer that Hawking gave up, namely that 
order will
increase when the universe contracts.
Has Hawking shown that the second class of universal histories, the 
universes, are overwhelmingly probable? If so, then he hasn't yet explained 
to his lay
readers how the trick was turned. What seems clear is that it can't be 
turned by reflecting
on the consequences of the no boundary principle for the state of one 
temporal extremity
of the universe, considered in isolation. For if that worked for the 
'initial' state it would
also work for the 'final' state; unless of course the argument had illicitly 
appealed to
temporal asymmetry, in applying some constraint to the 'initial' state that 
it didn't apply to
the 'final' state. This is an important point. When we're trying to explain 
asymmetry, we are not allowed for example to put any weight on the idea that 
the Big
Bang occurs at the start of the universe. After all, how could we tell that 
we aren't mistaken,
and that the Big Bang isn't really the finish of the universe? We must 
assume that the truth
of the matter is that it is neither, and that our ordinary inclination to 
treat it as the start is
just one manifestation of the temporal asymmetry we're trying to explain.
Page 6
Hawking thus needs an argument that excludes disorder-disorder universes 
universes with high entropy at both temporal extremities), without also 
excluding orderdisorder
universes (or, what comes to the same thing, disorder-order universes). The 
point suggests that it is impossible to get such an argument from the no 
proposal (or indeed from any other time-symmetric physical theory), simply 
by reflecting
on its consequences for one temporal extremity. In virtue of the underlying 
time symmetry, a consequence for one extremity is also a consequence for the 
other. What
is needed is therefore some more general argument, to the effect that 
universes are impossible (or at least overwhelmingly improbable). It needs 
to be shown
that almost all possible universes have at least one ordered temporal 
extremity – or
equivalently, at most one disordered extremity. (As Hawking points out, it 
will then be
quite legitimate to invoke a weak anthropic argument to explain why we 
regard the ordered
extremity thus guaranteed as an initial extremity. In virtue of its 
consequences for
temporal asymmetry elsewhere in the universe, conscious observers are bound 
to regard
this state of order as lying in their past.)
That's the first possibility: Hawking has such an argument, but hasn't 
explained to
his lay public what it is. As I see it, the other possibilities are that 
Hawking has made one
of two mistakes. Either his no boundary proposal does exclude disorder at 
both temporal
extremities of the universe, in which case his mistake was to change his 
mind about
contraction leading to decreasing entropy; or the proposal doesn't exclude 
disorder at
either temporal extremity of the universe, in which case his mistake is to 
think that the no
boundary proposal does away with the need for initial conditions in 
explaining temporal
The former mistake would be a more pleasing outcome than the latter. For one
thing, it would restore the appealing symmetry in time, which Hawking says 
he originally
saw as one of the attractions of the no boundary proposal – a symmetry which 
is lost if
contraction needn't lead to decreasing entropy. More importantly, it would 
mean that
Hawking's explanation of time asymmetry would still be intact – a much 
Page 7
conclusion than the latter possibility, the discovery that the no boundary 
proposal simply
fails to deliver its promised benefits, at least in this respect.
What is more, the former mistake might itself have a nice explanation, in 
terms of
the temporally asymmetric character of our ordinary view of the world. One 
of the
manifestations of this ordinary asymmetry is that we regard it as 'natural' 
for physical
systems to be governed by initial constraints, but as highly unnatural for 
them to be
governed by final constraints. We expect events to be determined by their 
past, but not by
their future. Accordingly, we find it much easier to make sense of a 
universe evolving
'from' tightly constrained initial conditions, than of it evolving evolving 
'towards' similarly
constrained final conditions. So it would seem odd to say that the universal 
whose discovery led Hawking to change his mind about entropy in the 
universe – those histories that start with order and finish with disorder – 
are excluded
because they violate a final condition stemming from the no boundary 
condition. It seems
miraculous that the course of the universe at a particular time could be 
bound by
conditions many billions of years in the future.
However, this seeming oddity is surely just a manifestation of our ordinary
asymmetric way of looking at time. If we look at things from an atemporal 
perspective, as
we need to if we are to explain temporal asymmetry in a non-circular way, 
then the oddity
vanishes. As I noted earlier, from this perspective it makes no more sense 
to say that the
universe really 'begins' at one temporal extremity and 'evolves' towards the 
other, than vice
versa. So initial and final constraints stand and fall together. If we're 
entitled to one then
we're entitled to the other.
To pay lip service to the need for such an atemporal perspective is one 
however; to be faithful in practice is quite another. This being so, it is 
conceivable that
Hawking's concession to his colleagues does rest on a breach of faith at 
precisely this
point – on a failure to insist that final constraints are as legitimate as 
initial constraints in
narrowing the class of possible world histories. To show that entropy 
decreases in a recontracting
universe, we don't need to show that the initial constraints themselves 
that entropy behaves in this way – that they themselves so restrict the 
class of possible
Page 8
histories of the universe. We only need to show that the initial and final 
constraints jointly
restrict the possible histories in the appropriate way. Given that much, and 
of course a
plausible argument for both the initial and final constraints, there's 
nothing mysterious
going on. Only a lingering attachment to the ordinary asymmetric perspective 
makes this
use of final conditions look in any way suspicious. (It is true that there 
is still the mystery
of what happens 'at the changeover', when entropy changes direction. But 
presumably regards this as a surmountable problem, since he was earlier 
prepared to
advocate this view.)
It may be unfair of me to suggest that Hawking's concession to his 
might rest on this sort of conceptual mistake. If so, I apologise, and can 
only say in my
defence that I'm a philosopher, and philosophers and physicists have a 
tendency to under-estimate one another. (The tendency is illustrated by 
Hawking's own
gentle dig at twentieth century philosophy in the concluding pages of A 
Brief History of
Time). But I don't think that it is unfair to claim that there is a 
tantalizing gap in Hawking's
popular account of his endeavour to explain the asymmetry of time. I'll 
happily accept
Hawking's verdict, and go back to the analysis of language (or whatever we 
do these days), if only he will tell us how the butler pulled it off.
Department of Philosophy
Research School of Social Sciences
Australian National University
Australia 2601

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