
Einstein's 3rd Postulate by M. R. Gale I know, I know. The hallways of physics are littered with failed attempts to dethrone Einstein and here we go again apparently. But hear me out. The road to Special Relativity starts with two fundamental postulates: Invariant laws of physics Invariant (and finite) light speed The 2 nd one is a hard pill to swallow because it flies in the face of common sense. How can everyone measure the same speed of light if we’re all mulling about in different directions at different speeds? It’s absurd. But Einstein compels us to keep an open mind and follow the math. The experimentalists will sort us out if we run afoul of Mother Nature. He starts by clarifying the concept of simultaneity because it’s not so easy if light speed is invariant. Think laser range finder. You send some light towards a reflector and measure how long it takes to come back. Split the difference to establish the time of the reflection event and multiply by light speed to establis...