i understand that time slows down as compared to a stationary perspective when an object is travelling at a certain velocity, but by how much does time slows down for that object? whats the formula behind this time difference? also, i understand that Einstein has derived this idea when he was comparing the different perspective of an observer with how he observed the speed of light approaching him ie. the result is that the observer will measure the same speed of light from whatever perspective he was measuring. so is it right for me to say that when one is travelling at the speed of light (just an analogy although i know it is impossible), his time should stop as compared to our perspective??