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240 BCE
Eratosthenes calculates the circumference of the Earth
Many people tried to calculate the circumference of the Earth, but nobody could accurately do it until Eratosthenes did it. This was very important because we had no idea how large the Earth was until he figured it out. -
140
Claudius Ptolemy improved the star catalog
Claudius Ptolemy did a fantastic job of improving the star catalog. This star catalog was important because it helped astronomy advance because they knew where many of the stars were positioned and other information about them. -
1543
Nicolaus Copernicus theorizes that planets revolve around the Sun
This was an important discovery because before this discover, it was believed that the universe revolved around the Earth. However, after this discover, we learned that this was not the case and it allowed us to discover the importance of the Sun. -
1572
Tycho Brahe discovers a "new star"
This discovery was very important to astronomy because before it, people believed that stars were unchanging and fixed. However, after Brahe discovered a "new star" that was further than the moon, this theory was put to bed. -
Johannes Kepler discovers the three laws of planetary motion
The discovery of these laws was very important because it helped people understand planetary motion better. These laws allowed us to calculate things such as planets' orbits, orbital periods, orbits' axis, and more. -
Sir Isaac Newton discovers the theory of gravity
This discovery by Isaac Newton is one of the most important discoveries in history. It was important because it gave an explanation as to why things fell to the ground and it allowed people to learn more about our planet. -
Albert Einstein discovers the theory of relativity
This discovery was important because it redefined gravity as we know it. Einstein said that instead of gravity being an invisible force, it was the warping of space, which increases with the size of the object.