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**Physics, Astronomy & Cosmology / Does Distance Reduction Of Rindler Horizon Follow The Velocity Addition Formula?**

« **on:**06/04/2020 23:41:42 »

I'll start a new topic for this because I don't want to hijack someone else's.

If we look at it from Object A's frame, B is orbitting around us (tidally locked). If we then switch to Object B's frame, we are stationary and A is spinning.

Now you could say that if Object B is orbiting Object A then Object B is under constant acceleration but if Object A is spinning then there is no acceleration.

What if there were only one object, could it spin and/or accelerate? I don't see how. Is acceleration really frame independent or is it just as relative as velocity?

Shouldn't time dilation also be a function of the rate of change of separation?QuoteIf two observers are circling each other without the distance between them changing then of course they would each see the other's watch ticking at the same rate as their own watch but how could following a path that spirals inwards cause a different result than a direct path?Easiest case: From PoV of Earth, the remote clock is getting closer (blueshift) but is moving (redshift). If you adjust the angle just right, the two cancel. The relativistic effect is a function of speed, but the Doppler effect is a function of the rate of reduction of separation. A circular path would be red shifted (all dilation), but a direct path is dominated by Doppler. Somewhere between is a balance. The math isn't too hard to work out.

Again though, if there were only two objects in the universe then wouldn't spin be entirely relative?QuoteImagine they are the only two objects in the universe. Any spiral path is now meaningless because there's no point of reference to create a spiral.Earth is the reference. Remember, rotation is still absolute, not relative.

So no need for a 3rd object for it to be a spiral.

If we look at it from Object A's frame, B is orbitting around us (tidally locked). If we then switch to Object B's frame, we are stationary and A is spinning.

Now you could say that if Object B is orbiting Object A then Object B is under constant acceleration but if Object A is spinning then there is no acceleration.

What if there were only one object, could it spin and/or accelerate? I don't see how. Is acceleration really frame independent or is it just as relative as velocity?