# Relativistic Effects Observed with Time Travel

Disclaimer: My domain knowledge on these topics is pretty minimal. I'm a "physics fan".

From what I understand about relativity, if there are two identical objects, A and B, and A is stationary and B is not, then A will observe that B's time is elapsing more slowly than its own. It will also notice that B is shorter in the direction of travel than A is.

Now let's assume that A and B could somehow see through time as well as space (this is potentially where the question breaks down). I suppose they would see something like a series of cubes, representing each instance in time, with all the objects in different positions.

If both A and B were now stationary in space, but B was traveling twice as fast through time than A was: Would there be any relativistic effects A would see as it is observing B?

• Is A in some enormous gravity well? Otherwise it cannot travel slower through time than B when they are both stationary – Jim Jul 8 '14 at 17:57
• @jim If I was in space and stationary. What would be causing me to travel through time at the "speed" that I am? – Griffin Jul 8 '14 at 18:01
• This is the fastest possible speed you can experience for time passing. Only strong gravity or high speeds can slow it down – Jim Jul 8 '14 at 18:08
• @Jim which is fine, since only the relative rate of time elapsing is stated for A and B. – Kyle Oman Jul 8 '14 at 18:10

Then A will observe that B's time is elapsing more slowly than its own. It will also notice that B is shorter in the direction of travel than A is.

But, it is also true that B will observe that A's time is elapsing more slowly than its own and B will also notice that A is shorter in the direction of travel than B is.

This is because motion is relative. We can't really say that A is stationary since, according to B, it is A that is moving.

What we can say is that there are two identical objects in relative motion with respect to each other.

If both A and B were now stationary in space, but B was traveling twice as fast through time than A was. Would there be any relativistic effects A would see as it is observing B?

In special relativity, if both A and B are inertial and at rest with respect to each other, their clocks run at the same rate so that's that.

Now, if A and B are Rindler observers, both A and B agree that their spatial separation is constant but each experiences a different constant proper acceleration. Thus, their clocks will run at different rates.

However, in an inertial frame of reference, the spatial distance between A & B is changing so not everyone agrees that A & B are relatively at rest.

This is all to point out that there is no simple setup with a straightforward answer to your question.