Today in 1546 (in Skane, then in Denmark, now in Sweden) Tycho Brahe was born. He travelled and studied extensively in Eurpoe, which aroused his interest in alchemy and astronomy. In 1572 Tycho observed the new star in Cassiopeia and published a brief tract about it the following year. He was convinced that the improvement of astronomy hinged on accurate observations. Tycho accepted an offer of a large amount of gold and an island from the King Frederick II to establish an observatory. He called it Uraniburg, a combination of Greek and German measning "City of Heaven". It was a very professional setup, but it did not possess any telescopes, which had yet to be invented. It was a NE observatory, using quadrants to measure the positions of stars and planets to better predict the future planetary positions and times of eclipses. Earlier astronomers had been content to observe the positions of planets and the Moon at certain important points of their orbits (e.g., opposition, quadrature, station), Tycho and his cast of assistants observed these bodies throughout their orbits. As a result, a number of orbital anomalies never before noticed were made explicit by Tycho. Without these complete series of observations of unprecedented accuracy, Kepler could not have discovered that planets move in elliptical orbits. Tycho was also the first astronomer to make corrections for atmospheric refraction. In general, whereas previous astronomers made observations accurate to perhaps 15 arc minutes, those of Tycho were accurate to perhaps 2 arc minutes, and it has been shown that his best observations were accurate to about half an arc minute.
Whilst Tycho firmly believed that the Sun revolved arounds the Earth, he was the first to systematically measure the sky, and he set the groundwork for the scientific revolution to come. When complete, no longer would people look to ancient and holy texts for their answers about the Universe, but rather they would look to their observations of natural phenomena to deduce the nature of the Universe. Philosophy became Natural Philospohy, which became science, which has provided all the substantial benefits that we enjoy from our material culture. In our scientific history, Tycho's contribution was substantial.
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