Hi. I will make this question small and simple, in fact, I will just give an analogy. According to the first postulate of Special Relativity, if I was traveling at 100 MPH, and my mass was 100 KG. I was traveling past a friend named David, who's mass is 100 KG too. Then my Kinetic Energy is 99904.5. But, according to the first postulate of Special Relativity, in my own frame of reference, my KE is 0, and David's KE is 99904.5. Thanks in advance, :tongue2: There are 3 types of knowledge in the world, knowledge, understanding, and imagination.