Light Travel After Big Bang: Baseball Universe Impact

[Pjpic]

If the universe had stayed the size of a baseball, would it have taken light 13.5 billion years to travel across it?

 

[student07]

What is your thought about it?

 

[phinds]

If the universe had stayed the size of a baseball, would it have taken light 13.5 billion years to travel across it?

The universe has never been "the size of a baseball" so I'm not clear why you are asking what would have happened if it has "stayed" that size.

 

[Pjpic]

What is your thought about it?

I don't know, maybe something about how the density(?) of spacetime effects light.

 

[phinds]

I don't know, maybe something about how the density(?) of spacetime effects light.

This posits an incorrect assumption that spacetime is an "ether". It is not.

 

[PeterDonis]

If the universe had stayed the size of a baseball

The universe, as best we can tell, is spatially infinite, so, as phinds said, it has never been "the size of a baseball".

something about how the density(?) of spacetime effects light.

Spacetime doesn't have a density. The matter and energy present in spacetime does, but spacetime itself doesn't.

 

[Pjpic]

The universe, as best we can tell, is spatially infinite, so, as phinds said, it has never been "the size of a baseball".



Spacetime doesn't have a density. The matter and energy present in spacetime does, but spacetime itself doesn't.

Maybe the question s/h/b stated as: If the currently visible universe had stopped expanding at an earlier time, would the greater energy density cause light to take the same 13.5 b.l.y. to traverse the radius?

 

[PeterDonis]

If the currently visible universe had stopped expanding at an earlier time

The only way this could have happened would be if the universe were closed and that earlier time was the moment of maximum expansion. So the universe would currently be contracting.

would the greater energy density cause light to take the same 13.5 b.l.y. to traverse the radius?

First of all, it's years, not light-years, since you're talking about time.

The time it takes light to cover a given distance in the universe is not affected by the energy density, except in so far as the energy density determines how the expansion proceeds. All you need to know to figure out light paths is the expansion profile.