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If extraterrestrial civilizations exist in our galaxy—and there are good reasons to think they do—it's probably a good idea to mind our own business and hope they do the same.

There seems to be plenty of available real estate for extraterrestrials to live on. In the past few years, astronomers have identified over 500 planets circling nearby stars. Extrapolating these findings, it is likely that tens of trillions of planets revolve the hundreds of billions of stars that make up our home galaxy. Trillions of these planets could have Earth-like characteristics, e.g., rocky with liquid water.

In a 2008 article in the journal Astrobiology, University of East Anglia researcher Andrew Watson calculated [PDF] the probability that intelligent life will emerge on Earth-like planets is quite low (less than 0.01 percent over 4 billion years). However, if there are a trillion Earth-like planets in the galaxy that would imply that intelligent life could arise on something like 10 million of them. Or if that is too high, cut the figure down by a factor of 10, to just one million planets inhabited by intelligent aliens.

Americans are open to the existence of extraterrestrial civilizations. A 2008 Scripps Howard News Service poll found that 56 percent of Americans believe that intelligent life exists on other planets, and more than a third think that aliens have already visited Earth. In 1960, Project Ozma used a radio telescope to search for artificial transmissions from nearby stars. In November, astronomers from 12 countries celebrated the 50th anniversary of SETI (Search Extraterrestrial Intelligence) using new instruments, including the Allen Telescope Array, that dramatically increase the rate at which stars can be surveyed for signals produced by technologically advanced civilizations. Since 1999, the SETI@home project has involved hundreds of thousands of volunteers who process radio telescope data on their home computers searching for signals. So far, the sky searches have turned up nothing.

That's a rather provincial point of view, and besides, if ETs are already visiting here -- which they certainly appear to be -- then I'm sure they could care less about that sentiment.  To read the rest of the article, click here.
Category: Science