Are we alone in the universe?
Scientists searching the heavens are increasingly convinced that we are not. Not long ago, no one knew if there were planets around the countless stars in the sky. In the past few years, astronomers using new techniques and technology, including NASA’s space telescope, Kepler, have detected evidence of more than 1,500 planets in orbit around other suns. Fifty-four of those “extrasolar’’ planets are located in a “Goldilocks zone”—close enough to a sun that temperatures are not too cold and not too warm, so that water would mostly take liquid form. This finding becomes more eye-opening when you consider that Kepler focused its camera on a tiny portion of space. If it scanned the entire sky, scientists say, it might discover 400,000 planets in our Milky Way galaxy alone. Multiply that by the estimated 100 billion galaxies in the universe, says Seth Shostak, senior astronomer for the Search for Extraterrestrial Intelligence Institute (SETI), and “Earth-like worlds might be as common as ants at a picnic.’’

Would extraterrestrial life be intelligent?
Some might, but much of it probably is not. Life flourished on Earth for billions of years before it developed structures that could be called brains. For 160 million years, dinosaurs were the dominant form of life on Earth, and their brains were roughly the size of a chicken’s. Homo sapiens has existed for only about 200,000 of the 4.6 billion years of this planet’s existence. “In terms of the universe,’’ says Alan Boss, a planetary scientist at the Carnegie Institution, “intelligent life only exists for a fraction of time.’’ Which means that by the time E.T. shows up or sends a signal—say, 10 million years from now—humans could be extinct.

Would E.T. look like us?
Only an egotistical human could ask such a question. Our own planet supports an incredible array of life forms, many of them radically different from our own. Among them are “extremophiles’’—organisms that thrive in conditions once believed to be inhospitable to any form of life, including boiling undersea vents; environments laced with toxic levels of salt, acid, and other chemicals; and even nuclear reactor waste pools. Who’s to say alien life didn’t evolve under conditions unimagin­able to us? Intelligent aliens might look like lizards or fish. Aliens might also have evolved for millions of years longer than we have, and thus “advanced beyond flesh and blood,’’ says former NASA chief historian Steven J. Dick. Such “post-biological’’ beings might have merged with artificial intelligence and look like machines, or might not have anything resembling bodies at all.

Are we hunting for E.T.?
Yes. The search began in 1960, when astronomer Frank Drake began listening for radio signals from space. But his organization, SETI, is not well-funded, and has scrutinized fewer than 1,000 of the Milky Way’s approximately 200 billion stars. It’s the space equivalent of searching for fish by “scooping a single glass of water from the oceans,” says Jill Tarter, director of the Center for SETI Research. SETI recently teamed up with the University of California to build the Allen Telescope Array, a cluster of 350 radio dishes that will scour the sky 1,000 times faster than is possible now.

Are we sending our own signals into space?
Drake beamed a message toward the M13 star cluster in 1974. It should reach its destination in about 25,000 years. Even if we heard from a civilization 1,000 light-years away, it would take 2,000 years for us to respond and to receive their reply. Space travel is even more problematic, because of the almost inconceivable distances between stars and the speed limitations imposed by the laws of physics. At current maximum speeds, a spaceship would take thousands of years to reach nearby star systems. Unless it proves possible to exceed or somehow circumvent the speed of light, perhaps by traveling through time-bending “wormholes’’ in space described in theoretical physics, interstellar travel will remain impossible.

What if aliens do contact us?
Then the world as we know it will be irrevocably changed. It’s highly possible that a more advanced alien civilization could impart knowledge that would herald a new Renaissance, says futurist Clifford Pickover. Science and technology, and perhaps medicine, would take a great leap forward. But there could be downsides, too. Tangible proof that mankind is not the center of the universe would spark an unprecedented philosophical and moral upheaval. Astrophysicist Stephen Hawking has even warned that extraterrestrial explorers would probably want to conquer and colonize our planet. “I think the outcome would be much as when Christopher Columbus first landed in America,” says Hawking, “which didn’t turn out very well for the Native Americans.” Most E.T.-seekers aren’t that pessimistic, but they agree that the discovery would alter the course of human history. Discovering that the universe is teeming with life, says astrobiologist Paul Davies, would force human beings to question “who we are and where we fit into the great cosmic scheme of things. The search for life beyond Earth is really a search for ourselves.”

The impact on religion
If the human race discovers that it is not alone in the universe, how would that affect the world’s religions? For biblical literalists, Islamic fundamentalists, and conservatives of most religions, it would represent a major theological crisis, since most holy scriptures begin with the presumption that mankind is at the center of God’s creation, and that we were made in his image. One leading evangelical, Gary Bates of the Creation Ministries in Atlanta, says extraterrestrial life “would actually make a mockery of the very reason Christ came to die for our sins.’’ But the Catholic Church, which burned Giordano Bruno at the stake in 1600 for suggesting “a plurality of worlds,” is already hedging its bets. The Vatican’s chief astronomer, the Rev. José Gabriel Funes, announced several years ago that belief in aliens does not contradict faith in God. “Why can’t we speak of a ‘brother extraterrestrial’?” asked Funes. “It would still be part of creation.”