The question here that I posed, why Kepler? I don't mean, this question to be taken two ways. One is, what was it about Kepler personally that enabled him to do this. I leave that question to other people, I'm not, in spite of knowing two or three whom I've actually been willing to apply the name to in my life.

Just two or three people in my life have I known that I'll apply the word genius to. I'm still very dubious about the word, one of them, Ken Wilson, was the hardest working person I think I've ever known, physicists. And he's legendary for doing calculations, week long calculations that no other physicist would even think of doing.

Okay, so you know, why the personality enabled Kepler to stay with this for four whole years doing six-digit calculations, I don't, that's beside the point, okay? I'll let others try and figure that out. I have the same problem with Newton even though I can say a lot more about Newton's personality than I can Kepler's in this regard.

It's still mysterious to me, but there's another version of that question. Why Kepler rather than somebody before him? What put Kepler in a position where he could do what he did? And by far, these are in choice of order, really, in proper order. Without Tycho's observations it just doesn't happen.

Without Tycho's commitment to the idea that the goal of astronomy is agreement at all times on longitude and latitude, something that nobody had ever really pushed in the history of astronomy before. And that's Tycho pushing it. He literally couldn't understand why not. Okay. And that's why he started doing the observations and said astronomy has to be reconstructed from the ground up.

So those two were very much Tycho. Kepler's demonstrations on the limitation of depending so heavily on observations near opposition. That's a comment about his hunch, and his hunch that things ought to be tied to the actual sun, not to the mean sun and then taking the trouble to see that the way that shows up is a away from opposition.

Triangulations, it's hard to credit him with because they're sitting there in Copernicus. As there's much more question begging in Copernicus. But there they were and when he didn't really understand them he wrote to Maskelyne get some instructions on what Copernicus was doing and that taught him how to use triangulations.

Maskelyne and his teacher did that, and of course that is in the, that's in appendix in the first Kepler book, Mysterium Cosmographicum, which I didn't bring in from my office. I may get it at break. Then, having a very, very good theory of the Sun. Better than anybody ever had before, to start with.

That's important. Because he had it to cross check, when he started Mickey Mousing with that orbit. When he did bisection. He had a constraint to make sure it agreed with what Tycho already had. If that had been sloppy the ability argue, and there had been substantial deviations when you do the bisection, you wouldn't have known what to do.

And then the last thing, and you'll see this later tonight. According to him, it was a coincidence that he did Mars. The coincidence was that when he arrived and was given permission to work with him, he was essentially made an assistant to Longomontanus. And Longomontanus was doing Mars, so he jumped into Mars.

Now there's another line on it. Anybody who knew astronomy would have guessed Mars was the best one to do. Why? Because it was comparatively high in eccentricity. It went around a little over every two year period, so you have much more data for it. So you've got the, and it doesn't cross the sun, it doesn't disappear from you crossing the sun the way Venus and Mercury do.

So, it would appear the best fighting shot at it. So, I've always wondered the extent to which Kepler's thanking God for the fortune of putting him onto Mars was Kepler showing his being devout on the one hand, and the extent to which he really meant it that he would not have chosen Mars, left to his own devices.