On September 23, 1877, the French mathematician and astronomer Leviere died. Leviere (Urbain Jean Joseph Le Verrier, March 11, 1811 ¨C September 23, 1877) was a French mathematician and astronomer who calculated the orbit of Neptune and calculated by the German astronomer Galileo Galilei at the Berlin Observatory to observe Neptune. Leviere speculated that it was because of the existence of an unknown planet's gravitational action that interfered with Neptune's orbital movement, which astronomically is called the "gravity" effect. He calculated the orbit, position, size of the planet, and then asked Galileo from the Berlin Observatory to look for the unknown planet. On September 23, 1846, Galileo, according to the prophecy of Neptune, spent