Anti-eureka

In the middle of the night I suddenly realised that I don't understand gravity. It blew my mind! I had always thought that I did. I do see that if I drop a pen it will accelerate at 32 metres per second per second, etc. What I do not get is why. Supposing I had a pen on a table, with a piece of string on it, and I tugged on the string. The pen would move, and that's OK. Those forces, which we used to resolve mathematically in Mechanics at school, would act through the string, because its molecules stick together, and I can't claim to understand the forces that hold molecules together, but at least it's a small-scale local action, so I don't feel so bad about not getting it. But, say, the moon, all that way up in space, where we are lead to believe there really isn't much stuff about -- how on earth is gravity acting on that? Or the tides that feel the moon's gravity; what is happening to those water molecules to make them move? It's not a wave or a particle, is it? How does it travel through a vacuum?

I feel pretty good about this. I don't know why, but sometimes its quite pleasant to realise that you don't have a clue what is going on around you, however much you kid yourself that you do. Probably the answer is that I don't understand what's going on with the string either, I just think that I do.

Anyhoo, not understanding gravity is probably one of those things I learnt at school and then forgot. I have been rereading some excellent novels, and it's because of those I was thinking about gravity at all. This is Neal Stephenson's Baroque Trilogy. I strongly recommend them; no one else can convey the excitement of scientific discovery so well. They are set in the second half of the seventeenth century and the start of the eighteenth, and are about the things Newton and Leibniz etc were coming up with, political changes in England, and slavery. But they are more readable than that sounds, especially the bits about Half-Cocked Jack, king of the Vagabonds. These books would be famous and win big awards except that they are labelled 'Science Fiction'. This isn't the case at all, except that they do have science in. The closest thing I can think of is Pynchon's Mason and Dixon; and far stranger things happen in the latter, like the passionate mechanical duck.