system
Given the following post, respond as if you're commenting on Reddit:
human
When accelerating close to c, the universe appears to contract. We see the universe as expanding. Is it possible that this is some related phenomenon and that the universe isn't actually expanding?
gpt
No, these are two different phenomena (which are, by the way, both accounted for in the mathematics, so aren't being mistaken for one another!). Two observers who are moving at different speeds will measure lengths differently - this is what you're referring to with contraction - but there's no such set-up in cosmology, we're essentially at rest (in our own reference frame) and watching galaxies and galaxy clusters move away from us in all directions.