In 1,846, astronomer and mathematician Urbain Le Verrier sat down and attempted to locate a planet that had never been seen before by humans. Uranus (grow up) had been moving in unexpected ways, as predicted by the Newtonian theory of gravity.
Though the discrepancies were small, there was a difference between the observed orbit of Uranus and the way Newtonian physics predicted its orbit to be. In July, Le Verrier proposed that the difference could be explained by another planet beyond Uranus, and made predictions as to the orbit of this previously unknown body.
Being a mathematician first and an astronomer second, he wasn’t really interested in finding it with a telescope now that he’d found it in maths, and the task of searching for it was left to German astronomer Johann Gottfried Galle. On September 23, 1846, Galle looked at the spot Le Verrier had predicted the planet would be, and found to be within 1 degree of the spot… the planet Neptune.
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