The most important rule is that this speed limit has to apply to anyone measuring any speed from any point of view. When we say that nothing can be observed to go faster than the speed of light, we mean nothing, no matter what perspective you have on it. So let’s do a simple thought experiment. Suppose you are sitting on your couch and you turn on a flashlight. To you, the light from that flashlight is zooming away from you at the speed of light. But what if we strapped your couch to the top of a rocket and the rocket blasted away and started to move really fast? What happens now if you turn
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