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View Full Version : Expansion in different frames of reference

malaidas
2015-Jun-19, 07:22 AM
There are a couple of other similar threads at the moment, but I thought this question different enough to warrant it's own. I think I probably can see the answer, but I'm not 100%

My question is simple what happens to the rate of expansion we measure as we travel faster and faster?

The context of this question is that whilst locally expansion is low, over distance this becomes greater than the speed of light. However if you approach c, distance contracts. Now we don't know what happens at c, so let's keep this away from such a singularity, instead looking at something within the known physics, but at the edge so to speak.

If the rate of expansion is not also the same in all frames of reference does this not also imply that the observable universe should become bigger in effect and that this super fast object can in fact reach these locations that to our frame are accelerating away to fast to reach.

Eta: I know that time would be equally messed up such that at this speed relatively speaking to our frame of reference the object would not have enough time to get there. The question is from the perspective of the travelling object only. However if we are saying that objects are moving away from us such that light fro. Then can never get here, this raises the question of what happens to an object in such a frame as described?

Cougar
2015-Jun-19, 11:15 AM
what happens to the rate of expansion we measure as we travel faster and faster?

We imply expansion via the measured redshift of distant objects. Expansion would appear to be slower in our direction of travel, and faster in the opposite direction.

mkline55
2015-Jun-19, 02:26 PM
Is the question related to the discussion where a ship traveling at a high velocity could cross the 4.37 light year distance we measure between Sol and Alpha Centauri in months instead of years according to their on-board clock? If so, I don't have an answer. I'm just trying to clarify the question.

malaidas
2015-Jun-19, 02:39 PM
Is the question related to the discussion where a ship traveling at a high velocity could cross the 4.37 light year distance we measure between Sol and Alpha Centauri in months instead of years according to their on-board clock? If so, I don't have an answer. I'm just trying to clarify the question.

Yes its matter of what a person on board the ship for instance would theoretically see. At its extremes such a traveller could travel the distance of the observable universe in theory within their life time.