He mapped the heavens without a telescope, and his data rewrote astronomy.

Tycho Brahe died on October 24, 1601, in Prague, aged 54. The Danish nobleman had built Uraniborg, an observatory on the island of Hven, where he and his assistants measured the positions of stars and planets with remarkable accuracy using only the naked eye and large instruments.

In 1572 he showed that a brilliant new star in Cassiopeia lay far beyond the Moon, challenging the idea that the heavens never changed. His records passed to his assistant Johannes Kepler, who used them, especially for Mars, to work out his laws of planetary motion.

Why it still matters: careful measurement is the foundation of modern science.

Who deserves more credit for a discovery: the one who collects the data or the one who explains it?

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