Our galaxy likely contains more planets than stars, so what are the odds of finding distant Earth-like worlds that teem with life? Is it possible inhabitants of another planet are trying to contact us—and would we be able to recognize extraterrestrial life if it exists? To answer these questions, Kelly Beatty, senior editor of Sky & Telescope magazine, traces a scientific quest that reaches back in time and across the vastness of space.

He explores how life arose on Earth and the essential roles played by water, chemicals, and energy. Our planet hosts a dizzying array of lifeforms, some of which exist in extreme conditions not unlike those we might expect to find elsewhere. And we might not have to look far: A handful of worlds in our own solar system—especially the planet Mars and the icy outer-planet moons Europa, Enceladus, and Titan—all have characteristics that might be conducive to life.

Beatty follows the efforts of astronomers to find Earth-like worlds orbiting other stars and to determine whether they have the right mix of temperature, water-rich chemistry, and long-term stability to sustain life. He also recaps the search for extraterrestrial intelligence, also known as SETI, which seeks to intercept transmissions from distant technologically advanced civilizations.

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