Tycho Brahe

Brahe lost part of his nose in a duel over a mathematical dispute at twenty and wore a prosthesis for the rest of his life. Given the island of Hven by the Danish king, he built there an observatory and a research institute — with a printing press, a paper mill and workshops — and spent twenty years measuring the positions of stars and planets with instruments so large and so carefully calibrated that his accuracy was not bettered until telescopes arrived. He observed a new star in 1572 and a comet in 1577, and showed both were far beyond the Moon, which broke the ancient doctrine that the heavens do not change.

He quarrelled with a new king, left Denmark, and ended as imperial mathematician in Prague, where he hired a young assistant named Johannes Kepler and guarded his data from him jealously. He died suddenly at fifty-four, eleven days after a banquet; the long-told story of a burst bladder from politeness is doubtful, and modern examination of his remains has ruled out the mercury poisoning that was suspected instead. Kepler obtained the observations and used them to find that orbits are ellipses. Brahe lies in the Týn church on the Old Town Square.