Why nothing can go faster than the speed of light
I found that the author gave a great setup for an explanation, and then balked at giving the actual answer.<p>> For right now, if you just believe that four-velocities can never stretch or shrink because <i>that's just the way it is</i><p>In other words, nothing can go faster than the speed of light because that's the way it is? The author needs to explain why the magnitude of this four-velocity vector is the speed of light! I was hooked after the first few paragraphs, but then felt like it dead-ended in a circular argument.