Temporal thermodynamics

[jackle]

Not sure where to post this. You can move it if you like.

There is no right answer to this but I hope it makes you think as
much as it made me think.

A long time in the future, man-kind can travel backwards in time by
breaking the light barrier. The research team calculate that according
to Einstien's equations, they will trace a smooth path through
space-time as they are travelling backwards through time. The same
set of events can be viewed form inside and outside the ship. They are
however, curious as to what happens if they drop one of the glasses
of champaign aboad.

According to the 2nd law of thermodynamics, the glass drops then
smashes as time goes forward. This gives rise to a simple paradox.
Which way is forwards?

If the second law is obeyed in the reference frame of the space ship,
the on-board team experience nothing unusual, but the rest of the team
on the ground will see the same events, but to them, the glass is
smashing, then rising from the floor! Events aboard seem to go
backwards from the reference frame of the GROUND team.

To correct the paradox, the ground team argue that the second law must
be obeyed in the reference frame of the ground team, now they would
see it the right way round. BUT the on-board team complain
that they would experience the glass smashing, then rising from the
floor as they travel backwards through time! Events aboard seem to go
backwards from the reference frame of the ON-BOARD team.

Only one can be correct. The two teams place a bet. Who wins and why?

[chroot]

Simple. Nothing can go faster than light, and thus time-travel to the past is impossible.

- Warren

[jackle]

I quite agree, but did you think it through?

[chroot]

Originally posted by jackle
I quite agree, but did you think it through?
Yes. And I answered:
Simple. Nothing can go faster than light, and thus time-travel to the past is impossible.

- Warren

[jackle]

Imagine...

[chroot]

Originally posted by jackle
Imagine...
Imagine what? Shall I also imagine that 1 = 2? And left = right?

- Warren

[jackle]

Yes! Anything to expand the mind! Please!

[chroot]

Originally posted by jackle
Yes! Anything to expand the mind! Please!
The real world is much more fascinating than any imagined.

- Warren

[Mentat]

Well, jackle, if it's not enough for you that we can never end up in a situation where this problem would become relevant, then perhaps the fact that reality is different depending on your inertial reference frame will help. Basically, the people on the ship are only going backward in time in some reference frames, and not in others.

Also, if I were to drop a glass before having begun traveling backward, then I could logically expect to see the cup "pick itself up" so to speak. However, if I drop it while traveling backward in time, then it will indeed fall, and shatter. Traveling "forward" or "backward" is only relevant when you have to change it.

[Ivan Seeking]

...despite the fact that the essay by Stephen Hawking in this volume explains that time machines, in all likelihood, are physically impossible. There are two reasons for my ignoring Hawking's prediction. First, in 1895, another outstanding physicist, Lord Kelvin, then president of the Royal Society, claimed that "heavier-than-air flying machines are impossible." The second reason is one that Kip Thorne has pointed out many times: even if the laws of physics forbid time machines, the effort to understand them may teach us much by helping to sharpen our understanding of causality.

Igor Novikov: an essay printed [p57] in The Future of Spacetime; Cal Tech, 2002


If the press picked up that the government was funding research into time travel, there would either be an outcry at the waste of public money, or a demand the research be classified for military purposes.... We disguise what we are doing by using technical terms like "closed timelike curves", which is just code for time travel... Wormholes, if they exist, would be ideal for rapid space travel. You might go through a wormhole to the other side of the galaxy and be back in time for dinner.

Stephen Hawking: p87 The future of Spacetime

[jackle]

Originally posted by Mentat
...if I were to drop a glass before having begun traveling backward, then I could logically expect to see the cup "pick itself up" so to speak. However, if I drop it while traveling backward in time, then it will indeed fall, and shatter.

But either way, will not the same chain of events be viewed in reverse from the ground team? Wouldn't this mean that the second law has to be violated from at least one observer's perspective?