Is the concept of spacetime logical?

[TheGuyWhoGoesMoo]

I'm stupid in this area, but I think that it is IMPOSSIBLE to tell whether time speeds up or not. If time speeds up, then everything else would too, our brains would work faster and the signals to atomic clocks would speed up and the planets would move faster and everything. I think this is one of the theories that's just nonsense to debate about. >.<