[extropy-chat] FTL and Time Machines

[John K Clark]

In looking over the Extropian archives I noticed that the subject of faster
than light signaling and time machines had come up on the list before, about
8 years ago. I didn't have time to enter into the discussion then but I do
now, so I just used my Tachyon modem to send a message to the list back in
time to December 17 1997, and just for the hell of it I decided to cc a copy
to the list for November 25 2005 too.
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Relativity does not forbid anything from moving faster than light, only
stuff that has mass or energy or carries information. Strangely some things
have none of these attributes, although calling them "things" may be
stretching a point. It's been proven experimentally that some quantum
effects propagate much faster than light, probably instantly, and for
unlimited distances. One system can influence another system on the other
side of the universe with little or no delay, but it carries no information
because the receiving system just changes from one apparently random mode to
another, it's only when you compare the two systems (and that can only be
done at light speed or less) does the correspondence between the two systems
become obvious. The 2 random modes have equal energy so energy is not
transferred either.

A less spooky example could be found in the idea of Phase Speed. I'm
standing in the center of a huge hollow sphere 2 light years in diameter,
I've been there for a long time and I'm holding a powerful LASER that makes
a spot of light on the distant wall of the sphere one light year away.
Suddenly, still holding the LASER and in the space of one second I make a
complete 360 degree turn. Exactly one year later an observer standing at the
same place would see the spot move much faster than light, it would travel
the entire circumference of the sphere, 2PI or 6.28 light years in only one
second. No photon moved faster than light however, and no energy or
information between any two points traveled faster than light. A photon of
light moves at light speed and carries energy and information, a spot of
light can move at any speed but carries neither energy nor information.

And then there are Tachyons. Actually relativity does not forbid matter
moving faster than light, it forbids matter moving AT the speed of light.
That's almost the same thing but not quite. Perhaps a particle could somehow
tunnel past the speed of light or maybe Tachyons have always moved faster
than light from the first instant of The Big Bang.

People have looked for Tachyons but have never found the slightest evidence
that they exist in nature, much to the relief of physicists. Tachyons are an
embarrassment, the faster they move less energy they have, one that moved
just a little faster than light would have a lot of energy, one that moved
at an infinite velocity would have zero energy. Much worse, Tachyons move
backward in time, they arrive at their destination before they start. You
could communicate with the past.

Even though they have never been detected and the laws of physics do not
demand that Tachyons exist, they don't seem to forbid them either. Most
think nature is totalitarian, if it's not forbidden then it's mandatory.

What about the logical paradoxes that would result from communicating with
the past, wouldn't that be enough to rule out Tachyons? It would if anybody
saw them, but suppose nature rubbed out any witnesses to her crime and
brought a universe to an end that was about to see a paradox.

Damn, I just knocked my coffee cup off the table, what a mess! I'm really
not in the mood to clean it up, instead I'll use my Gateway 14,400 Tachyon
modem and send myself some E mail 2 minutes ago. I'll just hit the send key
and

.....brought a universe to an end that was about to see a paradox. Pardon
me, I just got some E mail from John, let's see what it says "

Dear John:

Be careful with that coffee cup near your elbow, you're about to knock it
over."

Wow, John is right, that cup is dangerously near the edge! I'll put it in a
safe place. It was nice of John to warn me about it, it's too bad that means
oblivion for him and his entire universe, but that's life, nature just will
not allow anybody to observe a paradox.

I know what you're thinking, how could John be so stupid, he must be
completely out of his mind!  Why else would he deliberately buy an obsolete
14,400 Tachyon modem? Well, call me cheap if you want but I still think the
28,800 model is too expensive, besides I have it on very good authority that
Gateway will drop the price next year.

     John K Clark       jonkc at att.net