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Made the first heliocentric model of the solar system (meaning the earth revolves around the sun) -
Measured the sun's rays at the summer solstice at two different places to find the circumference of the earth. -
He published his heliocentric theory of the universe and proposed that Earth rotates on its axis. -
Builds first reflective telescope known as the Newtonian telescope. -
Published the "principia mathematica".