History
Babylonian astronomers in the first millennium B.C.E. observed that the Sun's motion along the ecliptic was not uniform, though they were unaware of why this was; it is today known that this is due to the Earth moving in an elliptic orbit around the Sun, with the Earth moving faster when it is nearer to the Sun at perihelion and moving slower when it is farther away at aphelion.
In the 17th century, Johannes Kepler discovered that the orbits along which the planets travel around the Sun are ellipses with the Sun at one focus, in his first law of planetary motion. Later, Isaac Newton explained this as a corollary of his law of universal gravitation.
Read more about this topic: Elliptic Orbit
Famous quotes containing the word history:
“It takes a great deal of history to produce a little literature.”
—Henry James (1843–1916)
“We are told that men protect us; that they are generous, even chivalric in their protection. Gentlemen, if your protectors were women, and they took all your property and your children, and paid you half as much for your work, though as well or better done than your own, would you think much of the chivalry which permitted you to sit in street-cars and picked up your pocket- handkerchief?”
—Mary B. Clay, U.S. suffragist. As quoted in History of Woman Suffrage, vol. 4, ch. 3, by Susan B. Anthony and Ida Husted Harper (1902)
“History has neither the venerableness of antiquity, nor the freshness of the modern. It does as if it would go to the beginning of things, which natural history might with reason assume to do; but consider the Universal History, and then tell us,—when did burdock and plantain sprout first?”
—Henry David Thoreau (1817–1862)