If the universe stopped expanding, would everything stop moving? Would planets stop orbiting stars, for instance? Would light stop moving through space? If not, there would still be a way to measure time.
. . . . . if so, "Time" to start preparing for the "Big Crunch"! I expect that gravity would become dominant . . . . and collapse would insue, but that would still take some 'time'.
I wonder if time would then play out in reverse as it retreated into the big crunch and would it start off retreating faster then slower as it disappeared back into a singularity?
why do you think time might reverse? if the universe did start to collapse it would still be in a timeline that was moving towards the future. otherwise it is a bit like assuming that your return journey to somewhere reverses time.
I just pictured it as a movie playing in reverse. So what your saying is the arrow of time always moves forward even if its going in reverse. I love this stuff.
The arrow of time advances; and, having advanced, Moves on: nor all thy Piety nor Wit, Shall lure it back to cancel half a Line, Nor all thy Tears wash out a Word of it. so it goes forward and a collapsing universe wont alter that. ;-)
The arrow of time corresponds to the observed increase in entropy for the universe. As long as entropy keeps increasing, time probably would continue marching on even if the universe stopped expanding.
What if we were actually in a cosmic sea? Like the ocean here on Earth, we would see a ship leave the shore and go out of sight seeming like it was actually going away but it actually is only going to go in a circle and come back to where it started. Same with the galaxies, they seem to be "traveling away" from us but are they only going to go in a full circle and collapse back in upon themselves?:shrug:
The same thing that would happen if explosions turned into atomic bombs, or heat turned into fuel, or crap turned into apple pie.
Prom: . . . . so, physics never 'speculates'?? . . IMPO (speculating here, of course), speculation is oft-times a source of new and innovative ideas that advance the sciences.
Hmmm. If time is going forward - by convention. And if time went in reverse during the big crunch. It would follow that the instant that we went from expansion to contraction time would stop. If time stopped there would be no movement which would mean the big crunch could not occur. Seems like if there was a big crunch, (which is highly unlikely) time will still go forward.:shrug:
Name one, just one idea in one of the hard sciences that has come speculation of the type you advocate.
Just one? . . . Alfred Wegner . . . a metorologist . . who speculated that, due to their matching coastlines, Africa and South America were at one time together, then 'drifted' apart . . . His speculation lead to the grounding of modern Plate Tectoncs . . . I can probably come-up with others . . .why don't you 'name one' next . . ? BTW: I'd bet that Einstein did a lot of 'speculating' before solidifying his theories . . . and probably did a lot more speculating afterward. Do you think that in the initial stages of BB theory development there was no speculating? . . . that's what the human brain is good at . . . . speculating . . . then trying to prove those speculations are correct via the scientific method.
I believe Hawking had a theory that the arrow of time would run backward if the universe began to contract, but eventually thought his idea was wrong.
