There have been many game changing revelations in the history of astronomy which have each, in their own way, irrevocably challenged human's place in the world around us. Ferdinand Magellan's trip around the world confirmed the spherical nature of the earth, a theory that had existed since at least the Third Century, B.C. The Copernican revolution shattered the geo-centric model of the universe, which said the stars and the sun orbited around the earth. Something that's been harder to argue is the astronomical uniqueness of the planet we call home. To this day, the common assumption is that the planet earth fits an exceptional number of random criteria that make it suitable for sustaining life. It's size, density, makeup and distance from the sun are extremely unique. Harvard University astronomer Dimitar Sasselov is challenging that assumption. Using the Kepler space observatory, which he helped to design with a team of scientists, Sasselov has found over 700 planets that meet earth-like criteria and could even sustain human life. He explains his findings.

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