Observation is not limited to direct observation. You can take what you're seeing with instruments, and extrapolate based on known laws, and you're still doing science. In fact, this is even more important to science than direct observation, which is extremely limited. By direct observation, I can't even tell if the earth was here yesterday, or at least a thousand years ago, even less so if it will still be here tomorrow.

By the same token, when you look at certain characteristics of what you can observe of the universe, and you take the known laws of physics, you can find out a lot about the unobserved, and the un observable, universe.