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SomeoneRandom5325 t1_j0fa7th wrote

Reply to comment by alukyane in Does rotation break relativity? by starfyredragon

Yes, and a freefalling/orbiting reference frame is inertial and a reference frame on the planet is not, but general relativity makes things weird

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obog t1_j0fdv6c wrote

Wouldn't an orbital frame not be inertial? I mean in a small scale it would appear so, but an orbital reference frame would be the same as a rotational frame which is non-inertial. That can be proven by the fact that if you stick two object close to each other in orbit, they will drift around from where they were relative to each other. That wouldn't happen in a fully inertial frame of reference.

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mnvoronin t1_j0gbi6c wrote

Technically not and you can perform some tests confirming that (objects on the far wall will be accelerating ever so slightly compared to the objects on the inside wall), but the effect on the typical spacestation scale is very small (in order of nanometers per second squared).

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obog t1_j0gjarp wrote

Well yeah, as I said on small scales it does seem to be inertial but it isn't quite and those effects are noticeable between multiple objects in similar orbits.

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alukyane t1_j0get2c wrote

So if they're indistinguishable, I shouldn't be able to measure different "absolute acceleration" in the two, right?

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ableman t1_j0hd6f8 wrote

Yes, though I feel like there's some confusion here. An orbiting/freefalling reference frame is indistinguishable from a non-accelerating one. The reason they're indistinguishable is because of general relativity. Or phrased another way, them being indistinguishable is really weird and why we need general relativity.

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Game_Minds t1_j0gr3sv wrote

Any hypothetical measurements of acceleration would be skewed by miniscule differences in things like local gravity and additional undetected rotations, so it would be hard to pinpoint why they don't match up

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