The Discovery of Neptune

Gravity not only creates orbits, it perturbs them as well.

In 1781 William Herschel discovered the first planet not known to the ancients: Uranus.

By 1790 the orbit of Uranus had been calculated, and scientists soon recognized perturbations in the orbit.  Perturbations are disturbances or irregularities in the orbit, created by the pull of gravity on an orbiting body.

Adams in England and Leverrier in France both independently calculated the position of a planet beyond the orbit of Uranus, based on Newton's law of gravity.  Adams tried unsuccessfully to convince English astronomers to look for the undiscovered planet, using his calculations.

In 1846, Leverrier convinced the German astronomer, Johann Galle, to search a region of space suggested by his calculations.  Galle soon observed a new planet, Neptune, based on the work of Leverrier.

Today, Adams and Leverrier are both given credit for the discovery of Neptune, along with Galle.