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Calculated the Earth's size and this was important because it showed that Earth was a sphere. -
Known for his Theory of Epicycles which was important because it explained retrograde motion. -
Observed the Great Comet and concluded that the comet was farther away than the Moon. -
Proposed that planets orbit around the Sun and this was important because it laid the foundation for understanding the motion of heavenly bodies. -
He defined the Laws of Planetary Motion and this was important because it gave the first connection between planets. -
Came up with the 3 Laws of Motion which was important because it's the basis of our modern Physics. -
Came up with the Theory of Relativity which showed that time is not constant and neither are mass and weight.