Suppose you could speed up Earth’s rotation so that a day was only half as long? What would happen? Well, for starters we’d have to make new clocks that only have hours 1 to 6 for am and pm. If you had tickets to an 8 o’clock concert, you’d be out of luck: 8 o’clock no longer exists.
But maybe a more germane question is, why do physicists ask nutty questions like this? It’s never going to happen—just move on, right? Well, here’s the deal. Thinking about counterfactual scenarios gives us insight into how things work here in reality. Plus, it’s fun! Need I say more? OK, it might even