Abstract
Imagine you are about to create a universe. How would you do it? As soon as you say "let there be the laws of physics" you would immediately face a problem. Do the same laws hold for everyone in your universe regardless of where they are? Or do the laws change as you move about or face in different directions? Clearly the most equitable and fair way to proceed would be to make the laws of physics the same for all observers. To a physicist such equality and fairness of physical laws is called a symmetry, and the symmetry that requires the laws of physics to be the same for all observers is known as Lorentz symmetry.