Astronomy

Biography Tycho Brahe



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Tycho Brahe, noted astronomer and alchemist, made his contribution to science in a time of conflict. During his life, there were two competing versions of how the solar system and the universe organized. In one model, the heliocentric, the sun was the center of the solar system, with the planets moving around it.

In the other, the geocentric, earth was the center of all creation. In 1616, 15 years after Tycho's death, the Catholic Church ended this controversy, by declaring that the heliocentric model could only be discussed as a computational convenience. Both scriptural truth and logic, according to the church, proved that the cosmos centered on the earth.

Scientifically, the church was slightly behind the times. Politically, it was the power of the day. Giordano Bruno, a freethinking philosopher, burned at the stake in 1600. Across Europe, he had lectured on a heliocentric model, and proposed heretical alternatives to monotheism. In the hands of the inquisition, he had refused to recant.

Galileo famously suffered house arrest for hewing to the heliocentric model. Copernicus, the Polish genius whose model improved on the insights of astronomers before him, saw his work published with a preface declaring that it was only an aid to predicting the positions of the planets. It worked very well for that, too.

The heliocentric model prevailed eventually. It has been improved since with added knowledge. Thanks to Johannes Kepler, we now know that the planets move in elliptical orbits, and what drives their motion. Schoolchildren know, now, that the sun is not the center of the universe, any more than the earth is. While the controversy was raging, though, Tycho Brahe contributed a compromise model.

The Tychonic version of the solar system explained some of the anomalies that observers had noticed in the motion of the planets, though of course it could not explain them all. He placed the earth at the center of creation with the sun revolving around it, as doctrine required. Then he placed the other known planets in revolution about the sun, as if they were sol's moons. He disparaged the idea of planetary spheres. Outside the solar system, though, the stars were fixed upon a sphere of their own, hung upon the outer wall of the universe.

It was a stopgap, but it was popular in its day. It accounted for some of the glaring inconsistencies that supporters of the heliocentric model built their case upon, yet it did not undermine the basis of current science. Nor did it offend the church.

Tyge Brahe was born into the Danish nobility in 1546. Raised by his childless aunt and uncle, he became his uncle's heir. Though his family wished him to make his career in law, he chose science.

He studied at many of the universities of Europe, and published his first paper, about a supernova, in 1573. His was the first use of the term nova in astronomy. Many had thought this stellar explosion had to be nearer than Mars, because the stars were considered fixed ornaments on the celestial sphere that could not change.

Brahe used the concept of parallax to explain to his readers how far away the nova must be. If an object is set between an observer and a mural, and moved so slowly that its motion itself is undetectable, the way an observer will know of its motion is that its position against the mural will be seen to change. As it moves, it will appear against different parts of the picture. The alteration in the background proves that the object in the foreground has moved. That is parallax. It also occurs when the observer moves. Brahe used the lack of parallax motion to prove that the supernova he observed was not moving in front of a distant tapestry of stars. It was part of the tapestry, not in front of it.

Tycho, as he named himself in print, had formed the idea that astronomy depended on accurate observations. When he returned to his own land, Frederick II supported his research. The king granted him funding and land, on an island called Hven.

He built a fantastic facility there, Uraniborg. Over one hundred students and artisans worked and studied there. Among them was his sister Sophia, who was also dedicated to science. At Uraniborg, workers studied astrology and alchemy as well as astronomy. Tycho commissioned instruments manufactured to new standards of accuracy. The movement of celestial objects was measured with new precision, because he took refraction, the apparent displacement of distant objects due to atmospheric distortion, into account. He did this without ever using a telescope; he was the last major astronomer who did not use one.

Besides his scientific endeavors, he also produced horoscopes, which he actually appears to have believed in, at least to a degree. He was active in politics. He engaged in alchemical research. He also did extensive research in medicine. In his personal life, he had a life-long morganatic union with a commoner, Kirsten Jorgensdatter. They had eight children, six of whom lived to adulthood.

He spent his days in exploration and research. Each day, regular, accurate observations were made of the movements of celestial objects. This focused and useful life continued until the death of his patron. King Frederick's youthful heir and Tycho quarreled, partly over the scientist's neglect of a royal chapel in his care. Tycho finally left Denmark, at the age of 51.

He settled near Prague in 1599, with the patronage of Rudolph II, Holy Roman Emperor. There he continued his research. One of his assistants was Johannes Kepler. Tycho worked for two more years, until he died in 1601, after a very brief illness. Some say he died of uremia, and some say of mercury poisoning, so there is mystery in his last days.

In any case, Johannes Kepler carried astronomy and physics forward. He used Tycho's tables to work out and publish The Planetary Laws of Motion. His use of his employer's work was controversial at the time, but his insights remain unquestionably brilliant. Using the fruit of Tycho Brahe's years of patient careful observation, Kepler was able to explain how the very planets, including the earth, move.

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