Thursday, 20 September 2012

Hurray, it works, albeit slowly.

If dark energy is causing expansion of the universe, and one day it runs out and the universe starts collapsing back to a singularity.  Will time run backwards too?


  1. "Albeit slowly" was son doing a giant download at the same time. Time went slowly but not backwards.

  2. Is it possible that "backwards" is an artificial construct created by those of us living in a universe where time appears to run "forwards". I have tried to envisage a situation where we know whats going to happen but not what has already happened - which is presumably the norm for people living in a contracting universe. Understandably I can't get my head around how simple things like making a cup of tea would work..... "I know I have drunk it but I'm not sure when I'm going to make it?" Would there also be a period where time stands still as the universe transitions from forward time to backward time? Somehow I don't think this blog is big enough to answer the question!

  3. Why should time run backwards in a collapsing universe - what's the link between the SIZE of the universe and time? The expansion we detect at present is a physical phenomenon, not caused by time (as far as we know).

    1. It's a long time since I thought about this, but D&K have invited me to "do" Cosmology in an hour in February, so it's come back into my mind.

      Einstein tells us that space and time are conjoined as spacetime so since space has expanded since the singularity that brought it in to being, then maybe time has increased in parallel with it.

      Alas, I know nothing!

    2. When I think about your question I find I'm not sure what "time has increased " means. Is time today a bigger number than time yesterday? - yes in relation to our perception of the start of time. However time is different for different parts of the galaxy - for people nearer the edge of the galaxy and going much faster than us, time is slowed down so do they perceive less of an increase? Do we all thing the universe is 14bn years old? Also I can't get my head around the fact that if galactic time zones are different from one another is there a single point that they are all related to? i.e. standard universe time - (I'm not expecting an answer! ) I look forward to your talk but don't envy you having to condense this sort of stuff into something everyone can understand


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