Universal time

[asprung]

It is said that the universe is expanding at an accelerating rate and that galaxies will reach and exceed the speed of light. At such speed relative time should slowdown to zero and thus motion should cease.

 

To avoid this paradox I would suggest that the expansion proceeds at a universal time.

[Klaynos]

Expansion of space is not limited by relativity, it is not a speed of something in space, it is a speed of space itself expanding, there is no requirement for anything new to explain superluminal expansion.

[Sisyphus]

The expansion of space is not movement, it's just an increase of distances. Other galaxies are not moving through space away from us. Rather, "more space" is being added between us. And some are already receding at a rate of more than 1 light year per year. This does not mean that "time stops," however, because:

 

1) Once again, it's not movement.

2) There is no such thing as absolute velocity, just velocity with respect to something else.

 

I feel like we've had this conversation before.

[ajb]

I'll second that motion!

 

No contradiction with relativity.

[asprung]

When two bodies move apart the space between is expanded. How do we detect or measure any diffrence between moving though space and moving with its expansion.

[phyti]

The expansion of space is not movement, it's just an increase of distances. Other galaxies are not moving through space away from us. Rather, "more space" is being added between us. And some are already receding at a rate of more than 1 light year per year. This does not mean that "time stops," however, because:

 

1) Once again, it's not movement.

2) There is no such thing as absolute velocity, just velocity with respect to something else.

 

I feel like we've had this conversation before.

 

If no movement, how do you get all that red shift?

[swansont]

If no movement, how do you get all that red shift?

 

As Sisyphus noted, space is added between the objects. This is independent of any local motion.

[Physman]

This is actaully quite interesting. A while ago I posted a thread about how the universe could have an accelerating expansion although this expansion was merely more space being added at arbitrary points. I would argue that asprrung's case would still hold applicable even if the universe expanded as swansont implies.

[ponderer]

As Sisyphus noted, space is added between the objects. This is independent of any local motion.

 

The photon has a wavelength, the space that it occupies at any given time is also expanding, stretching out the wavelength.