I'm not a scientist man!
- Thread starter Ziggy Stardust
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Yes, the Big Bang is seen as the beginning of spacetime. There is no "before" because before is meaningless beyond the Big Bang.
kochman
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Is it?
What about those that claim the big bang is also a repeating cycle of explosion and retraction?
Farm Boy
I hope you dance
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Or that even if the observable universe goes cold and dead expanding into the void, there is more on a scale we cannot observe that bits may crash into or <insert speculations>.
Even those accept the singularity between these "universes".
The point is basically that if you imagine that while time goes by, universes emerge from big bangs and then collapse into a new big bang that starts a new universe and so on, you're in disagreement with current mainstream cosmologies, because time is not a thing that exists "outside" of the universe.
I've heard it referred to as surfing the entropy gradient. Not sure if that's at all accurate, though.
kochman
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The point being, time is only differentiated by overall change in entropy.
I'm hoping Uppi or Leoreth jump in here....
I'm hoping Uppi or Leoreth jump in here....
Yeah, there're a host of 'multiverse' ideas. The big thing to realise is that even though other multiverses might have an analogue to 'time', they don't require actual 'time'.
Imagine a cube. The top of the cube has a definite beginning and an end. If you ran your finger along a cube, the top would very much end, but you could continue running your finger along the side. Like the top of the cube, the side of the cube has a beginning, an end, and it very much has a surface. But it's not identical to the top of the cube, because the orientation of the planes aren't the same, and one plane transitions into another. This continuous transition certainly doesn't imply that the top face has no 'true' beginning. It does.
Previous/parallel universes can easily have a directionality that is analogous to time in many different ways, but it needn't be time.
Borachio
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I think you may be right.
On another aspect of this: there was one chap I heard about was considered an expert in symmetry of all things. And everyone thought he was a genius, until a couple of people "caught up" with his ideas. They found out he was no cleverer than anyone else. He'd just got ahead a bit.
On another aspect of this: there was one chap I heard about was considered an expert in symmetry of all things. And everyone thought he was a genius, until a couple of people "caught up" with his ideas. They found out he was no cleverer than anyone else. He'd just got ahead a bit.
Ziggy Stardust
Absolutely Sane
The point being, time is only differentiated by overall change in entropy.
I'm hoping Uppi or Leoreth jump in here....
That is a widely held view, but it has been shown to be wrong because of a few special cases where this does not hold.
Almost all fundamental processes on the quantum level are reversible, so they do not care about the direction of time. If time was going backwards, nobody would notice anything odd with these processes. But the entropy of a system increases, the process becomes irreversible. In principle i is still reversible, but the probability of that happening becomes extremely small due to statistics. So in these cases the entropy gradient gives you the direction of time.
However, there are a few fundamental processes which are not reversible, although the entropy does not change (Recent and only direct confirmation thus far: http://physics.aps.org/articles/v5/129#c1). Although the asymmetry is very small, these cases point towards there being more to time than just the entropy gradient.
Anyway, in Relativity time is closely tied to space. Giving just a time is meaningless without also giving the location is space of any event. But as space is tied to our universe, time has also to be tied to our universe. So if there was a multiverse*, every universe must have its own time (times?) with no relation to ours. Thus if there was an event in our universe and one in another, it would be impossible to say which one was before or after the other, because those events are disconnected in time and space.
*not to be confused with the many worlds of the Many-Worlds-Interpretation of quantum mechanics, which do share time and space (at least in part)
Thanks for the clarification!
I understand that time and space are really bound up with each other when we look at mass, motion, and gravity. I also seem to recall that the Planck Length defines a level of granularity, or discontinuity to space. Below the Planck length it is nonsensical to speak of size... I think.
Is the Planck length also defining the minimum ice of time? Or is that meaningless owing to what you mentioned earlier?
The Planck length divided by the speed of light is the Planck time, which has the same meaning. So it is just the standard conversion between space and time that also applies to Planck length and time.
What exactly happens at that scale is unknown, as we are quite far away from reaching that scale and our current theories are conflicting on the effects there.
