|MadSci Network: Astronomy|
Wow. That is a very thought provoking question. There are many explanations for why so many of the laws of physics and astronomy appear so simple. For one thing, realize that most of the Laws like Newtons's Law of Gravity are actually approximations. Einstein's General Theory of Relativity, which involves much more complex math, is a more accurate description of Gravity and space-time and physicists are STILL trying to understand it better. Quantum mechanics involves the study of the interactions of matter at the sub-atomic level which is a much more precise description of other simple concepts like how a prism disperses light into a rainbow. So when trying to understand a physical process, scientists will usually consider the simple explanation (Occam's Razor) and then build it up in complexity the better explain all the observations. Most physics and astronomy is really complex but either you don't get to hear about those details or we have not quite figured them out yet. The Universe is a vast, mysterious place.
Try the links in the MadSci Library for more information on Astronomy.