If two clocks are moving in space relative to each other, which one runs more slowly?

Question

Relativity states that time runs more slowly for an object in motion. Howevere, isn't it impossible to know if an object is in motion except by comparison to another object? If so, who's to say which object is moving? If the two objects are simply in motion relative to each other, then which would experience a slowing of time?

Seems that the consensus is that any observer will say that a clock moving relative to that observer is runnng slower than the observer's own clock. So if the clocks are accelerated such that they are still relative to each other, will they sync up? How does this relate to the story of twins where one goes on a speedy trip and returns less aged than the twin who stayed put? It seems to me that there is a difference, and that it's not just a case of each observer thinking the other clock is running slower. The crux of the issue seems to be that while we all agree that a clock in motion runs slower than one that is stationary, and we agree that movement is relative, still when the clocks are brought together one is behind the other. What's different if the movement is only relative to each other? It's go to have something to do with acceleration.

Answer 1

whichever one is moving more quickly would have time run more slowly for it than the slower one, but not by much.

Answer 2

You are quite right, and most of the answers you get here will be rubbish.

The answer is that both clocks will run more slowly, but relative to the other observer. The key term here is relativity, and the principle is very much that inertial frames are indistinguishable. So if B is moving with respect to A and hence its clocks are running slower relative to A's, then the reverse is also true.

Answer 3

Suppose there are A and B alone; there is nothing other than them to compare their speed.

For A, B is moving and for B, A is moving.

Both will measure the speed of light as the same.

A will say that B’s time is dilated, the time is slow.

B will say that a’s time is dilated, the time is slow.

IF TWO OBSERVERS ARE IN DIFFERENT INERTIAL SYSTEMS, EACH WILL ASSERT THAT THE CLOCK OF THE OTHER OBSERVER IS SLOW.

Answer 4

They both would. The faster they are moving, the slower time runs for them, however, within their time/space continuum, so whichever is moving fastest, will get further ahead in time/space than the other object.

Answer 5

The one on the left

Answer 6

The one that moves fastest.

The closer you get to the speed of light, the slower time travels.

Answer 7

You answered the question yourself. You are correct, time and motion are only relevant to the reference system you decide, there is no absolute coordinate system. Typically your are interested in comparing yourself to some other object and comparing the difference.

Answer 8

A normal clock will not work in space.