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1700 BCE
Johannes Kepler
Kepler solved the Laws of Planetary Motion: All planets travel in an elliptical orbit, the speed of a planet's orbit around the sun is inversely proportional to its distance from the sun, and squaring the time it takes for a planet to orbit the sun is equal to the cube of the distance from the sun. -
350 BCE
Aristotle
Aristotle taught his students in the Lyceum about the Sun and Moon and the distance from the Earth to the Moon and from the Earth to the Sun and studied the motion of the planets. He said the Earth was at the center of the Universe and was surrounded by the Sun, stars and planets in fixed spheres. He also discovered that the Earth was a sphere. -
240 BCE
Eratosthenes
Eratosthenes calculated the circumference of the Earth. He was a Geek Librarian in Alexandria. Eratosthenes also calculated the number of days in a year, 365, and 366 every fourth year. -
140
Claudius Ptolemy
Ptolemy traced the path of the planets and developed the planetary hypothesis, which states that the universe is a system of fixed spheres surrounding Earth. He also attempted to determine the radius of the Sun. -
1543
Nicolaus Copernicus
Copernicus discovered that the Earth is in a Heliocentric universe and that the Sun is at the Center of the Universe, not the Earth and that the time it takes for a planet to circle the sun depends on how far away the planet is away from the Sun. -
Galileo Galilei
Galileo used a telescope and built a telescope 32 times more powerful than any telescope built before. He is called the "Father of Modern Astronomy". He discovered the law of the pendulum. -
Tycho Brahe
Brahe made many measurements of the five known planets in his time that would help Johannes Kepler discover his laws of planetary motion. -
Sir Isaac Newton
Newton discovers the inverse square of distance formula for the Law of Gravitation. He also used a prism to separate the colors of light. -
Albert Einstein
Einstein discovered that Gravity is a result of the interactons of space with time called spacetime.
