Is Earth special or one of a billion similar worlds?

Earth is one special planet.

It has liquid water, plate tectonics, and an atmosphere that shelters it from the worst of the sun's rays. But many scientists agree our planet's most special feature might just be us.

"It's the only planet we know of that has life," said Alan Boss, a planet formation theorist at the Carnegie Institution of Washington in Washington, D.C.- from Space.com

clipped from www.space.com clipped from www.space.com Not-so-special Earth As our planet-hunting technology improves, many planet hunters expect to find Earth's twin. The search has led scientists to debate whether Earth is really as special as we think it is. "In the past 10 years, everything has been pointing in the direction of, 'Hey, the solar system, which we thought was unique, is not unique at all,'" said Alan Boss. Boss and many other scientists think it's likely that some form of life exists on some of those countless other planets out there. "Certainly there will be other planets that support life," he said. "I think life is actually quite common. I think we're going to find there are literally billions of them in the galaxy."