Terence Tao

Okay.

Yeah.

So I've always had an amateur interest in astronomy.

And so I've loved stories of how the early astronomers worked out the nature of the universe.

So Kepler was building on the work of Copernicus, who was himself building on the work of Aristarchus.

So Copernicus very famously proposed the heliocentric model that instead of the planets and the sun going around the earth, that the sun was at the center of the solar system and the other planets were going around the sun.

And Copernicus proposed that the orbits of the planets were perfect circles.

And his theory kind of fit the observations that the Greeks and the Arabs and the Indians had worked out over centuries.

I think Kepler got interested.

He learned about these theories in his studies, and he made this observation that the ratios of the size of the orbits that Kurenko predicted seemed to have some geometric meaning.

I think he started proposing that if you take, say, the orbit of, say, the Earth, and you enclose it in, I think, maybe a cube, the outer sphere that encloses the cube almost matched perfectly the orbit of Mars and so forth.

And there were six planets known at the time, five gaps between them.

And there were five perfect platonic solids, the cube, the tetrahedron, isocletron, octahedron, and dodecahedron.

And so he had this theory, which he thought was absolutely beautiful, that he could inscribe these platonic solids between the spheres of the planets.

And it seemed to fit.

And it seemed to be to him like, you know, God's design of the planets was matching this mathematical perfection of the platonic solids.

So he needed data to confirm this theory.

And at the time, there was only one really high-quality data set almost in existence, which was the... So Tycho Brahe, this Danish astronomer, very wealthy, eccentric astronomer, had managed to convince the Danish government to fund this extremely expensive observatory, this, in fact, an entire island, where he had taken decades of observations of all the planets, Mars, Jupiter, every night, at least every night for which the weather was clear.

with the naked eye, actually.

He was the last of the naked eye astronomers.