The Importance of Evidence in Science

The day someone drops an apple and it goes up, we'll have a discussion about gravity. But until that particular piece of evidence comes along, there's nothing to disprove that gravity behaves as we think it should. People are making a guess as to whether a theory is right based on some instinct. And general relativity was quite a simple set of ideas. It comes from Einstein's belief that it's space that produces gravity. If you can neatly explain a whole host of things that you've already observed about the world, that's a good sign that you're on the right track.