Hello, I'm new to the forums here but I just wanted to ask a couple of questions. Is the theory of Relativity unique in its proposal that space and time are interwoven? Basically, was it the first theory to make such a claim that there exists not only space and not only time but spacetime? Also, is this spacetime believed to be present in all levels, even in the subatomic level? Does Quantum Mechanics mention anything about space and time or is spacetime something unique to Relativity? Sorry about the long series of questions and sorry if they seem a little trivial. Thanks.