What We Know About The Innumerable Planets Outside Of Our Solar System
This is a question that human beings have wondered about for thousands of years. Here’s how the ancient Greek mathematician Metrodorus (400-350 B.C.) put it: A universe where Earth is “the only world,” he said, is about as believable as a “large field containing a single stalk.” About 2,000 years later, in the 16th century, the Italian philosopher Giordano Bruno suggested something similar. “Countless suns and countless earths” existed elsewhere, he said, all rotating “round their suns in exactly the same way as the planets of our system....