Harmony of the world

Charles, when I listed the open domains you said harmonyoftheworld might have to happen too, and you bought it before I finished the sentence. Here is the man you bought it from.

In 1619, in Linz, with the Thirty Years War kicking off around him and his mother on trial for witchcraft back home, Johannes Kepler finished the book he had wanted to write since he was twenty five. Harmonices Mundi. The harmony of the world. In Book Five he announced that the square of the time a planet takes to orbit the Sun is proportional to the cube of its distance. Physicists call it Kepler's third law and it is as true tonight as it was that afternoon. He mentioned it almost in passing. The point of the book was the music.

What he was actually hunting

He had already found that the planets move in ellipses with the Sun at one focus, and that they speed up when close and slow down when far. Those are his first two laws, published ten years earlier, and they demolished two thousand years of perfect circles. He did not celebrate. An ellipse was ugly to him, an admission that the cosmos was less perfect than Plato promised. So he went looking for the perfection somewhere else, and he found it, or convinced himself he did, in the speeds.

Every planet has a fastest speed at its closest point to the Sun and a slowest at its farthest. Kepler worked out the ratio of the two for each planet, and then the ratios between neighboring planets, and he found musical intervals. Saturn's extremes make a major third. Jupiter's make a minor third. Earth's make a semitone, which he noted bitterly is the interval of misery, and he wrote the Earth's song as mi, fa, mi: misery, famine, misery. Together the planets sang a six voice polyphony that never repeats, composed by God to be heard by the mind.

That is Pythagoras's music of the spheres and Plato's tuned world soul rebuilt out of the best data in Europe. Kepler had Tycho Brahe's observations, the most precise ever taken by the naked eye, and he spent years making the music fit the numbers rather than bending the numbers to the music. He was not a mystic ignoring the data. He was a mathematician who could not stand for the data to mean nothing.

He cast charts for a living

Kepler was a working astrologer. As imperial mathematician to Rudolf II in Prague and later as a district mathematician in Linz, part of the job was yearly almanacs with weather and politics in them, and private horoscopes for anyone who paid. He cast two for the general Wallenstein and chose his words carefully. He cast his own over and over, and his family's. He kept a notebook reading his own temperament as if it were a chart, and he is brutal about himself in it.

He also had contempt for most of what passed for astrology. He thought the twelve signs were an arbitrary grid dropped on the sky and the houses were made up. What he believed in were the aspects, the angles between planets, because angles are geometry and geometry is how God thinks. A soul, he argued, takes the imprint of the angles in the sky at the moment of birth the way wax takes a seal, and hums to those angles for the rest of its life. That is a proposed mechanism, which is more than Ptolemy managed. The aspect lines drawn across your wheel next door are the part Kepler would have signed off on.

His line on the whole business is the most quoted thing he ever wrote. Astrology is the foolish daughter of astronomy, but the mother would starve without her, because princes pay for the daughter. He wrote it in 1610 in a pamphlet whose full title warns theologians, physicians and philosophers not to throw the baby out with the bath, and the baby he meant was the harmony.

Why the chart site wears his name

Harmony of the World computes your chart from the real positions of the planets and the real geometry of your horizon, and then tells you what the tradition says about it. That is Kepler's exact position: get the astronomy right first, no excuses, and then ask what the geometry means. He is the last great mind that held both halves of the Pythagorean inheritance in one head, the measurement and the meaning, and the reason this site is named after his book is that his book is the hinge where they start to come apart.

Sixty eight years later Newton explained why the third law is true. His explanation had no music in it at all, and he was translating the Emerald Tablet on the side.