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I was reading about Hubbles Law on wikipedia and came across this paragraph:
I don't really understand what about SR makes it confined to "small regions", and what exactly defines a small region. If someone could explain that in as simple a way as possible please.
Thank you.
My assumption is this is because we are not directly measuring the velocities, just the redshifts, SR was formed using rigid measuring devices and we have none in this case. But we could measure them could we not? We have methods of measuring distances that far, could we not find the change in distance over time?As the formula implies, in very distant objects, v can be larger than c. This is not a violation of special relativity, because the rules of special relativity only apply precisely within a small region: a special-relativistic description of two widely-separated galaxies would in general be incorrect. (Thus special relativity strictly says, not that no speed can be faster than light, but that nothing can move past another object at a speed faster than light).
I don't really understand what about SR makes it confined to "small regions", and what exactly defines a small region. If someone could explain that in as simple a way as possible please.
Thank you.