 Let's talk about Bell's spaceship paradox, first put forward by, you guessed it, Deewen and Beren in 1959. So here's Alice, and she has just bought a brand new shiny spaceship. And here's Bob with a brand new spaceship of their own. Now Alice and Bob won't take their spaceships for a spin, so they get together like this while their friend Carl watches jealously from the ground. Alice and Bob stretch a rope between their ships, which Carl measures to have length L in his frame. Carl sees these ships start off stationary, and then they fire up their engines and fly off to the right, accelerating at the same rate. So Carl always sees Alice and Bob have the same velocity as each other, but that velocity is constantly increasing. Now beforehand, Alice and Bob made some predictions about what they thought would happen. So Bob said, let's look at things from my reference frame. So initially at the start, Alice and I start off a distance L apart. Now we always have the same velocity, so even as we accelerate and start moving, we will stay a distance L apart. So obviously the rope will not break. Now Alice had a different idea. She said let's look at things in Carl's reference frame. So Bob and I start off a distance L apart, and we always have the same velocity. So from Carl's point of view, we will stay a distance L apart. However, due to length contraction, the rope should shrink to a size L on gamma. So as we go very fast, the rope should break. So who do you agree with?