Say you woke up one day and your bed was gone. Your room, too. Gone. It's all gone. You wake up in an inky void. Not even a star. Okay, yes, it's a dumb idea, but just go with it. Now say you want to know if you move or not. Are you held fast in one spot? Or do you, say, list off to the left some? What I want to ask you is: Can you find out? Hell no. You can see that, sure. You don't need me to tell you. To move, you have to move to or away from ... well, from what? You'd have to say that you don't even get to use a word like "move" when you are the only body in that void. Sure. Okay. Now, let's add the bed back. Your bed is with you in the void. But not for long -- it goes away from you. You don't have any way to get it back, so you just let it go. But so now we have a body in the void with you. So does the bed move, or do you move? Or both? Well, you can see as well as I that it can go any way you like. Flip a coin. Who's to say? It's best to just say that you move away from the bed, and that the bed goes away from you. No one can say who's held fast and who isn't. [More]

Labels: fun, physics