On this day, 395 years ago, on November 15, 1630 (the twelfth lunar month), the German astronomer Kepler passed away.

Kepler (1571~ 1630.11.15), a German astronomer. He entered the University of Tübingen in 1587 and began to study Copernican astronomy. His main achievement was to lay the foundation for celestial mechanics. He analyzed Tycho Brahe's observations accumulated over the years and proposed three laws of planetary motion (Kepler's laws): the first law is the law of elliptical orbits - the orbit of the planet is elliptical and the sun is at one focus; the second law is the law of equal area - in equal time, the area swept by the connection between the planet and the sun is equal; the third law is the law of harmony - the square of the orbital period of any two planets is proportional to the cube of the half-length diameter of the orbit. This laid the foundation for Newton's discovery of the law of gravity.