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240 BCE
Eratosthenes
Eratosthenes is known for his measurement of the Earth's circumference around 240 BC. This event was important because it provided the first accurate measurement of the size of the Earth, which was a major achievement in the field of geography and astronomy. -
101
Claudius Ptolemy
Ptolemy's most significant astronomical discovery was his geocentric theory/model of the universe, which he described in his book, the Almagest. He believed in his theory between 100 AD and 200AD. His work was important because it helped to establish the study of astronomy as a scientific field, and his geocentric model was widely accepted for over a thousand years until it was eventually replaced by the heliocentric theory/model of the solar system proposed by Copernicus. -
1543
Nicholas Copernicus
In 1543, Nicolaus Copernicus detailed his radical theory of the Universe in which the Earth, along with the other planets, rotated around the Sun. This discovery was important because it challenged the geocentric theory that had been accepted for centuries and paved the way for future scientific discoveries and advancements in astronomy. -
Aug 17, 1563
Tycho Brahe
Tycho observed a special event--Jupiter and Saturn passed very close to each other. This event was important because it provided evidence that the universe was constantly in motion. This helped to pave the way for future advancements in astronomy and our understanding of the universe. -
Johannes Kepler
Kepler's most significant discovery was his three laws of planetary motion, which were published between 1609 and 1619. These laws were important because they helped to establish the field of celestial mechanics, which has since become a fundamental part of astronomy and space exploration. -
Sir Isaac Newton
Newton's most significant discovery was his law of universal gravitation, which he published in 1687. Newton's work was important because it helped to establish the field of celestial mechanics, which has since become a fundamental part of astronomy and space exploration. -
Albert Einstein
Einstein's theory of general relativity provided a new framework for understanding gravity and the motion of objects in space. This even was important because it fundamentally changed out understanding of gravity and the structure of the universe. This led to more important discoveries such as the existence of black holes and gravitational waves.