|How certain can I be that modern physics applies to distant places? Shouldn't I wait until reputable scientists have performed experiments way off in outer space? — JS
Fortunately, you don't have to wait that long. From astronomical observations, we are fairly certain that the laws of physics as we know them apply throughout the visible universe. It wouldn't take large changes in the physical laws to radically change the structures of atoms, molecules, stars, and galaxies. So the fact that the light and other particles we see coming from distant places is so similar to what we see coming from nearby sources is pretty strong evidence that the laws of physics don't change with distance. Also, the fact that the light we see from distant sources has been traveling for a long time means that the laws of physics don't seem to have changed much (if at all) with time, either. While there are theories that predict subtle but orderly changes in the laws of physics with time and location, effectively making those laws more complicated, no one seriously thinks that the laws of physics change radically and randomly from place to place in the Universe.