For example, it takes eight minutes for the light of the sun to reach us. Thus effectively when we look at the sun we are seeing it as it was eight minutes ago. Astronomy is unique amongst the scientific fields in that it actively witnesses the past. (
Just right orbit. Not only is the just right part of the galaxy a requirement but so is the orbital path the sun follows. Our sun orbits the galaxy in a manner that keeps the earth away from black holes and other catastrophic areas of the galaxy.