Off-Topic Discussion > General Discussion

I have a physics question!

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Scourge of Ages:
(the following questions are not the question:) Could I just google this? Probably, but I like the interaction. What makes me think there's physicists here? It worked last time, and I just need a general understanding.

My question regards relativity, and it is:

Are two objects traveling in the same direction at the same speed - even if they're separated by a long distance - in the same frame of reference?

Imagine a scenario where two space ships are moving through space at, let's say, 0.5C. They're separated by... 50,000 km. How would radio communication between these two ships work? Would it be roughly normal but with a little extra lag due to the extra distance traveled? Would it be identical to if they were both stationary? Would there be some sort of frequency weirdness like redshift due to them both moving so quickly?

It's been a while since I took my last class relating to special relativity, but here's my take (also without Googling): if they are travelling perfectly parallel, in straight lines, at the exact same speed, they would be in the same frame of reference (for the context of this question). The speed of light always looks like c (in a vacuum) to the observer. I don't think there would be any difference in their communication from being stationary from their points of view.  I bet things would get weird if you tried to analyse the situation from a stationary observer's point of view...

Redshift/Blueshift only relates to travelling away from or towards the source of light, because of a perceived change in frequency (but not speed).

Once again - it's been a while so I might be misremembering. Special relativity is weird  :lol:

Scourge of Ages:

--- Quote from: ShadowsOfLight on October 20, 2022, 05:11:35 pm ---Special relativity is weird  :lol:

--- End quote ---

I don't know much, but I do know that :)

Mongoose:
Yeah, vaguely-remembered classes from 15 years ago (God I'm old) make me think ShadowsOfLight is correct. If both ships are traveling at the same constant velocity, they'd be in the same inertial reference frame, and there would be no discernible difference compared to if they were viewed as stationary.

Colonol Dekker:
Now if two trains are travelling on parallel tracks 20 meters apart, at a full speed of say 125mph, and you try to throw a ball between them, will it make it?