If Time were running in reverse would we know it?

by D wiltshire 48 Replies latest watchtower beliefs

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  D wiltshire

  If "time" is running backwards I dont see how that we would ever know, perhaps some clever physicist could devise an experiment to find out for sure.

  Some theoreticians have suggested the reason the arrow of time runs from past to future is tied intimately to the expansion of space. Since Einstein special theory of relativity we have come to see that "time", space and speed are all relative. We now more correctly speak of "space-time" instead of just space.

  So as the universe continues to expand time runs from past to present. Some have suggested that as the expansion slowly comes to a halt and if there is enough matter in the universe that it would reverse and we would be headed towards the "Big Crunch". At this time some speculate that the arrow of time would be reversed and "time" would go from future to past.

  This reversal would mean that light would be going into stars instead of going out, and that thermal dynamics would be reverse as well as every thing else.

  Our thoughts would also be reversed which would lead me to conclude that we would not know a reversal of time was in progress. I think that in our minds it would still seem that stars were "giving off light" instead of sucking it in, and that the laws of thermodynamics followed the same order.

  Any thoughts?
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  peacefulpete

  The observance that the universe's expansion is accelerating not slowing has lead to the discovery of antigravity. Much like dark matter it is only recognised indirectly but it has quickly gained wide acceptance by merits of it's explanitory power. Therefore theories about cycling universes and their innate characteristics have been revised. Time is in fact relative and this blows our minds considering the possible implications. But it appears that noone will ever experience the scenario you have described. Too bad it would be cool.
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  Elsewhere

  You're over complicating this with too much Star Trek mentality... time is just an abstract idea assigned to the passage of events, nothing more.

  The "arrow" of time is entropy. Without entropy there would be no passage of time because we would not observe change without it.

  Whatever direction entropy moves, is the direction of the flow of time.

  The universe expanding does not have anything to do with the forward flow of time... all it does is cause the material within to cool. If or when the universe contracts, we will still see events progressing as usual, only the material in the universe will be heating up.
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  Realist

  in his "brief history of time" hawking talked about the possibility of time going in reverse once the universe starts to shrink (if it ever does). he dismissed that idea however. time will not run in reverse.
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  OUTLAW

  WALTUO...?tnereffid gnihtyna eciton ew dluow,esrever ni erew emit fI
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  onacruse

  Elsewhere catches the essential point. Steven Weinberg touches on this connection between time-direction, entropy, and the "Standard Model" of the universe (Gravitation and Cosmology, Principles and Applications of the General Theory of Relativity, p. 597)(italics added):

  Could this oscillation be periodic? That is, can we restore a steady state picture of the universe, by viewing cosnic history on a sufficiently grand time scale? One obvious objection is that entropy is presumably created, not destroyed, in each cycle. It has been suggested that entropy might be destroyed during contracting phases, because it is the expansion of the universe that, by providing a heat sink, sets the direction of time's arrow in thermodynamic processes. However, there is no detailed model that describes how this can come about. In particular, it is hard to see how time's arrow could be reversed just at the moment when R(t) reaches its maximum value, at which time the background radiation temperature becomes so low, of order 1 degree K, that it can hardly affect terrestrial processes.

  This leads to another point:

  All current relativistic and quantum-mechanical models derive their mathematical validation from differential calculus. One of the fundamental premises of calculus is that all functions describing a phenomenon must be "continuous." Like "black holes," the origination of the universe from a singularity (as in "big bang") is, by mathematical definition, undefined; similar to dividing by zero. Perhaps someday a mathematics will be developed that will define such "critical points," but for now we're stuck with simply knowing that we don't know.

  Also, "time" as such is rather like Coriolis and centrifugal forces: a fictitious perceptual anomaly of the Riemannian tensor manifold that best describes the geometric nature of our universe, as best we can determine for now.

  Craig
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  expatbrit

  a fictitious perceptual anomaly of the Riemannian tensor manifold that best describes the geometric nature of our universe, as best we can determine for now.

  More to the point: will physicists ever be able to speak intelligibly before the end of time?

  Expatbrit
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  Robdar

  WALTUO...?tnereffid gnihtyna eciton ew dluow,esrever ni erew emit fI

  Outlaw, again you have entertained me with another hilarious post. Dude,you are too funny.

  Love ya,

  Robyn

  Also, "time" as such is rather like Coriolis and centrifugal forces: a fictitious perceptual anomaly of the Riemannian tensor manifold that best describes the geometric nature of our universe, as best we can determine for now.

  Dang, Ona,

  I love it when you talk all intelligent like.

  Love ya,

  Robyn

  Edited by - robdar on 8 February 2003 17:16:36
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  bikerchic

  Robdar:

  Dang, Ona,

  I love it when you talk all intelligent like.

  LOL Pitty poor me I have to listen to this kind of BS all the time!

  Expatbrit:

  The purpose of physicists is to baffle everybody with their jargon thinking that it will make them sound intelligent.

  Katie (of the has her dictionary out all the time class)
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  Robdar

  LOL Pitty poor me I have to listen to this kind of BS all the time!

  Bikerchic,

  You have my deepest sympathies.

  Love ya,

  Robyn