“it’s just a question of what you say is sitting still”
“It was the space doctor who figured out the answer. He said that if our ideas about light were right, then our ideas about distance and seconds must be wrong. He said that time doesn’t pass the same for everyone. When you go fast, he said, the world around you changes shape, and time outside starts moving slower.”
“The doctor’s idea was that weight slows down time, and it explained how light could bend.”
“When people checked the space doctor’s numbers about how weight changes the shape of space, they found that they explained the small world’s strange path in a way that no other idea did. The numbers also explained how much the sun’s weight bends the light going past it, showing that the bending was twice as much as other people thought it would be. When everyone learned how good the space doctor’s big idea was at explaining things like this, they got very excited. They started putting his face on the cover of the papers, and everyone learned his name.”
“To make the ideas easier to explain, people will often tell you to imagine something more familiar, like a big flat sheet with weights on it. These pictures are good, but sometimes they make you think of new questions, and when you try to use the picture to answer the new questions, you get answers that don’t fit with each other. When you get answers that don’t fit together, it can make you feel like you’re not very good at thinking. Or, if you’re the kind of person who feels like you’re good at thinking, it can make you think that the space doctor’s numbers must be wrong. But a lot of the time it’s not you or the numbers—instead, it’s the picture that’s wrong in some small way.”
“We need people to keep asking questions, because there are problems with the space doctor’s big idea. The numbers in the idea give us the right answers for almost every problem we use them on, but when we use it to talk about things that are very small and very heavy, like the middles of dying stars that fall in on themselves, it gives answers that don’t fit together with other things that we know. We’re still looking for a better idea that can fit everything together, and someday, the right question might help us find it.”