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  He believed that the Earth was in the center of our solar system. This is important because it gave fuel to the exploration on what was actually true
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  He calculated the Earth's circumference while everyone else believed the Earth was flat. This is important to out history because we would not be this advanced in technology without his discovery.
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  He created our heliocentric model of the solar system. This is important because we now know how our solar system works
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  He created the geocentric model of our solar system, this is important because it inspired scientists to check his work and discover our actual layout of our solar system.
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  He created a book that went into more detail about Copernicus's heliocentric theory, with more detail on orbits, and what else may lie there. This is important because it gives us a better understanding of our solar system.
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  Isaac created the law of gravity. This is important because it helps explain the orbits in our solar system.
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  Albert Einstein created special theory of relativity. Albert's discovery now is the reason for the studies in cosmology to expand