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Period: 100 to 160
Ptolemy
Ptolemy was an astronomer and mathematician. He believed that the Earth was the center of the Universe. The word for earth in Greek is geo, so we call this idea a "geocentric" theory. -
Period: 1501 to 1503
Nicolaus Copermicus
Nicolaus Copernicus formulated a model of the universe that placed the Sun rather than the Earth at the center of the universe. -
Period: 1581 to
Galileo Galilei
his discovery of the four most massive moons of Jupiter, now known as the Galilean moons. -
Period: 1582 to
Edmond Halley
He was the second Astronomer Royal in Britain, succeeding John Flamsteed in 1720. From an observatory he constructed on Saint Helena, Halley recorded a transit of Mercury across the Sun. -
Period: to
Johannes Kepler
Johannes Kepler discove Kepler's three laws of planetary motion -
Period: to
William Herschel
William Herschel Discovered Uranus -
Period: to
Discovery of the first four asteroids
Piazzi named it after Ceres, the Roman goddess of agriculture. Three other asteroids (2 Pallas, 3 Juno, and 4 Vesta) were discovered over the next few years, with Vesta found in 1807. -
Period: to
Urban Le Verrier
Urbain Le Verrier discovered Neptune -
Period: to
Clyde Tombaugh
discovered Pluto -
Period: to
Voyager 1
Voyager 1 is a space probe launched by NASA on September 5, 1977. Part of the Voyager program to study the outer Solar System, Voyager 1 launched 16 days after its twin, Voyager 2.