Q: What role does Dark Matter play in the behavior of things inside the solar system?
The big difference between dark matter and ordinary matter is that dark matter is “aloof” and doesn’t interact with other stuff. In fact, if it weren’t for the gravitational influence of dark matter, we would have no reason to suspect its existence at all. Because dark matter doesn’t clump it stays really spread out and forms one big, roughly spherical, cloud around the galaxy. In the above picture the dark matter is spread out uniformly. But dark matter (whatever it is) is light-proof and poke-proof, and that’s deeply frustrating.