direction of time (Has it changed) & will it lead to a Big crunch

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Hi

While reading a Stephen Hawkins book it stated that time is like an arrow, it has a direction, it also stated that the direction of the time arrow was the same as the expanding universe. When & if the universe expands so much that it must retract,

1/would the time arrow also change?

2/Has this already happened & we call it dezavou (meeting people all over again)?

3/Will it cause a BIG CRUNCH (Opposite to Big Bang)?

Thanks
Rob
 
Per your reading of Stephen Hawking, in turn:

1. - Why would it?

2. - Who knows. Maybe, but I seriously doubt it. This is more in the realm of the metaphysical than the physical.

3. - Very probably. But "it" won't be caused by "reversing time's arrow", just the natural laws of physics collapsing the universe again as a result of gravity (if the universe has enough mass which is still open to question).
 
Re:Re:direction of time (Has it changed) & will it lead to a Big crunch

Isn't it said that electon neutirnos (virtual particles) that alegedly have no mass come in and out of existence in the vacuum of space (dark/exotic matter) and provide Einstein's Cosmological Constant that provide lots of energy to fight against the in-pull of gravity and continues to push the universe out to expand?

Maybe this is what cause the universe to continually expand. Personally, I cannnot see the Big Crunch scenario.
 
Re:Re:Re:direction of time (Has it changed) & will it lead to a Big crunch

Who knows?

I remember Dr Hawking theorising about a 'great attractor' which is actually 'pulling' at the outer edge of the expanding universe. I don't recall the details though. Maybe someone can fill us in?
 
Re:Re:Re:direction of time (Has it changed) & will it lead to a Big crunch

Good point, good question. This is an area where Cosmologists AND Quantum Theorists get to come together and scratch each others' heads over this one.

Correct me if I'm wrong, but I believe several years after it was first published, Einstein recanted his "Cosmological Constant" as the "...biggest mistake of my (his) life" however.

My understanding of the "dark matter" problem is that it is being sought as a contributor to the solution for the expansion problem, not a causal factor of it. But, It sounds like you're more well read on this topic than I am.

I think many of us "hope" for a big crunch, as it implies a 'steady state' universe itself where it is constantly renewing itself thru this "Big Bang/Big Crunch" cycle. It may be just wishful thinking on the part of us optimists however. The other 'steady state' theory being the one that the universe renews itself AS it expands by providing local phenomenae like 'quasars' to spew forth new matter. (This being the universe "without beginning or end" theory.)

This leaves the only other possibility to be that the universe had a beginning, (Big Bang), and will now continue to expand and 'run down' until it runs out of steam and dies. (Entropy). The very concept of this implies a 'space/time' out of our concept. i.e. - What was BEFORE the big bang, and how far can it expand even after all the matter has burned out.

This is the stuff Hawking contemplates to come up with theories that require a God, and theories that negate the necessity for one.

You and I could probably discuss/debate it ad infinitum. Hawking certainly is.
 
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