We're about to move into the modern age of physics. In the early 1800's, scientists began examining the basis of matter, space, and time. Sometimes it gets very confusing, but the big idea is that Newton's physics describe about 90% of the way things work in the universe (mechanics). His ideas start to break down when you talk about ideas such as objects moving at the speed of light, the inside of atoms, extreme temperatures, and when the objects are huge (like galaxies interacting with each other).