For 4.6 billion years our living planet has been alone in a vast and silent universe. But soon, Earth's isolation could come to an end. Over the past two decades, astronomers have discovered thousands of planets orbiting other stars. Some of these exoplanets may be mirror images of our own world. And more are being found all the time.
Yet as the pace of discovery quickens, an answer to the universe's greatest riddle still remains just out of reach: Is the great silence and emptiness of the cosmos a sign that we and our world are somehow singular, special, and profoundly alone, or does it just mean that we