X-Message-Number: 8113
Date: Sun, 20 Apr 1997 09:40:57 -0700 (PDT)
From: John K Clark <>
Subject: CRYONICS Faster than light and time travel
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In #8108 Keith Lynch <> On Sat, 19 Apr 1997 Wrote:
>what you would need to time-reverse consists of infrared photons
>racing away from Earth in all directions at the speed of light. Even
>if we were able to detect and analyze all photons over an area of
>many square light-years, first we would have to travel faster than
>light to get ahead of them. Forget it.
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
instantly and for unlimited distances. One system can influence another
system on the other side of the universe without the slightest 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 2 years 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, I think I'll use my Gateway 14,400 Tachyon modem
and send myself some E mail 5 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
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