The problem was light. A few dozen years before the space doctor’s time, someone explained with numbers how waves of light and radio move through space. Everyone checked those numbers every way they could, and they seemed to be right. But there was trouble. The numbers said that the wave moved through space a certain distance every second. (The distance is about seven times around Earth.) They didn’t say what was sitting still. They just said a certain distance every second.
It took people a while to realize what a huge problem this was. The numbers said that everyone will see light going that same distance every second, but what happens if you go really fast in the same direction as the light? If someone drove next to a light wave in a really fast car, wouldn’t they see the light going past them slowly? The numbers said no—they would see the light going past them just as fast as if they were standing still.
.. 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 space doctor figured out that to explain how weight pulls things like light, we have to play around with time again. He showed that if time itself goes slower near heavy things, then the side of the light near the heavy thing won’t go as far every second.
.. But the space doctor figured out that heavy things change the shape of space as well as time. This changes how circles work. If you draw a circle around something heavy, he said, the distance around the edge will be a little shorter than the usual three times the distance across it.
.. To know exactly what time it is on a space boat, they have to change the watches a little to make up for both of these problems. If the space doctor’s ideas were wrong, your phone wouldn’t be able to tell where it was.