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255 BCE
Eratosthenes' Armillary Sphere
Eratosthenes invented the armillary sphere, which was a tool used by astronomers to figure out where the stars were in the sky how they appeared to move. The tool is very helpful and was used to solve various astronomical problems to a crude degree of accuracy. -
150
Claudius Ptolemy' geocentric theory of the universe
Ptolemy thought that the universe was a set of nested spheres surrounding the Earth and believed the Earth was the center of the universe. This theory was very contraversal and led to the discovery that the Sun is the center. -
1514
Nicolaus Copernicus's view on the Universe
Copernicus gave his friends a book about his view of the universe. In it, he proposed that the Earth is not the center of the universe. His views helped pioneer a scientific revolution. -
Nov 11, 1572
Tycho Brahe discovers "new star"
In 1572, Brahe discovered a "new star" in the constellation Cassiopeia. This new star was later revealed to most likely have been a supernova. -
Johannes Kepler's elliptical orbits
In 1605, Kepler discovered that the Earth and planets travel about the sun in elliptical orbits. His discovery turned Copernicus' theory into a dynamic universe. -
Sir Isaac Newton's Law of Universal Gravitation
Sir Issac Newton established the Law of Universal Gravitation and debuted it in his book, Mathematical Principles of Natural Philosophy. This law explained the motion of the planets around the Sun and it explains rainfall, snowfall, and the flow of water. -
Albert Einstein's Theory of General Relativity
In 1916, Einstein publishes his theory of general relativity. The theory says that that the observed gravitational effect between masses results from their warping of spacetime. The theory has become an essential tool in astrophysics.