richard feynman - in astronomy the sizes and numbers and the best thing to do is to relax and enjoy the tininess of us and the enormity of the rest of the universe Of course if you're feeling depressed by that you can always look at it the other way and think of how big you are compared to the atoms and the parts of atoms and then you're an enormous universe through those atoms so you can sort of stand in the middle and enjoy everything both ways But the great part of astronomy is the imagination that's been necessary guess what kinds of structures what kinds of things can be happening to produce the light and the effects of the light of the stars that we do see And I could take an example a historical example See at many times in science by using imagination you've imagined something which could be according to all the known knowledge of the laws And you don't know whether it is yet or not And that's very interesting There's a creative imagination you like to call it not just imagining things that are relatively easy but something different And to take an example of a star as we understand it the ordinary star like the sun is a great big ball of gas of hydrogen it's burning up the hydrogen and so forth and it's an enormous mass of gas and it's held together by gravity You don't have to always understand gravity as curved space It's good enough for this purpose that force inversely square the distance When things are closer together the force is stronger And it pulls everything together By the way that's why the world is round because the globe of Earth is pulled together as much as possible And if it had a great mountain and an irregularity of a bump so it would be pulled in by gravity and it all gets smooth Rocks aren't strong enough to hold a bump much bigger than a few miles and Mount Everest is our biggest bump But on the moon where the gravity is less the bumps are higher The mountains are bigger on the moon Anyway to get back to the star It's all held together by gravity and it's got a nuclear fuel which we haven't been talking about that's burning up the hydrogen and generating energy which keeps things and after a while I would use the fuel up

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