Neptune was the first planet discovered not with a telescope, but rather with pen and paper. After the discovery of Uranus in 1781, astronomers noticed that the planet’s orbit was slightly off. Based on this aberration, John Couch Adams and Urbain Jean Joseph Leverrier used math to hypthosize that the gravity from another planet was affecting Uranus’ orbit. With pen and paper, they figured out not only where Neptune should be, but also how large it must be. It was not until 1846, however, that Neptune's existence was verified when Johann Gottfried Galle saw the planet for the first time.