the revolutionary work of tycho brahe -- 8/21/20

Today's encore selection -- from Tycho & Kepler by Kitty Ferguson. One of the underappreciated keys to launching the scientific age was the work of Tycho Brahe. His contribution was simple but revolutionary: At a point just before the invention of the telescope, he wanted to precisely record the positions of the planets and the stars. However, the instruments used before him to make these measurements produced unreliable results. Brahe was a Danish nobleman, and thus deemed to be above such pursuits as astronomy. But as a nobleman, he had the financial means of only a very few. He cast aside convention to spend a lifetime making better instruments to take these more precise measurements of the stars and planets, and then used those instruments to make measurements far superior to any that had been previously made. It was this revolutionary work that allowed his student Johannes Kepler to come up with his three laws of planetary motion. And it was Kepler's work that was so helpful to Sir Isaac Newton and his laws of thermodynamics.

The first revolutionary instrument Tycho Brahe constructed was in Herrevad Abbey, Denmark, in 1572, which he called the "half-sextant":

"One of Tycho's first undertakings at Herrevad was to construct a new astronomical instrument, a 'half-sextant' with straight walnut legs and a curved brass arc. A little later he added a larger, interchange­able sixty-degree arc. It was this sixty-degree arc that gave a 'sextant' its name -- probably coined by Tycho himself. Sixty de­grees is one-sixth of a circle; a half-sextant has a thirty-degree arc. Sextants and half-sextants resemble slices of pie. By sighting along the two legs or sides (where the pie is 'cut') -- pointing one leg toward one star and the second leg toward another, for example -- it was possible to measure the angular distance between two heavenly bodies. One could similarly measure a body's altitude above the horizon.

Tycho Brahe's sextant, used for measuring the angular distances between stars.

"Tycho was getting more from this effort than a better instrument.

"He was developing expertise and learning lessons that would serve him later. One conclusion Tycho reached was that in order to design and manufacture instruments capable of the precision he wanted, he would need highly skilled, specialist instrument builders working at his own facility, where he could supervise them. For the moment, he had to content himself with getting the best results he could with nonspecialist artisans under his supervision, while ordering more in­tricate or decorative parts, and sometimes whole instruments, from Copenhagen. What began at Herrevad was never completely realized there, but the possibilities Tycho saw unfolding at the beautiful old abbey gave him a much clearer vision of what he hoped to accom­plish and how to go about it."



Kitty Ferguson


Tycho & Kepler: The Unlikely Partnership that Forever Changed Our Understanding of the Heavens


Walker Publishing Company, Inc.


Copyright 2002 by Kitty Ferguson


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