Book excerpt: Please note: This is a companion version & not the original book. Sample Book Insights: #1 The concept of relative motion is a key part of Special Relativity. It is a very straightforward idea, and most readers will already understand it intuitively. All motion is relative, and there is no such thing as absolute motion. #2 The speed of a car, boat, or train is usually measured relative to the surface of Earth. But if you were traveling in a spaceship deep in interstellar space, there would be no obvious point of reference and thus no way of measuring your speed. #3 The laws of physics do not change over time, and they are the same at every location in the universe. The laws of physics are independent of orientation relative to the universe. #4 The laws of physics are all the established scientific laws that govern the behavior of energy and matter. The laws of physics do not change with time, location, orientation, or speed.