Why search for only Earth-like life on other planets? (Beginner)

Our family went to see a program at the Barlow Planetarium in Appleton, Wisconsin last night. The narrator was talking about conditions that would be necessary to support life, including requirements for temperature, atmosphere and elements or compounds. How much imagination can we use to suppose that life may have developed in circumstances far different from ours?

You are of course 100% correct that we really have no way of knowing what conditions are required for life in general; we only know what is required for life like us. Indeed, it takes only a little imagination to think of how life might arise otherwise.

On the other hand, if we go out and start searching for life, we have to narrow our search, or else we'll be searching all of 10 billion stars in our galaxy. So to narrow down the search, most astronomers who look for extraterrestrial life search near single stars like our sun, where planets like Earth might be found. After all, we know for a fact that Earth's conditions are conducive to life, so we should search Earth-like places first to find life in the universe.

This page was last updated June 27, 2015.

About the Author

Dave Kornreich

Dave was the founder of Ask an Astronomer. He got his PhD from Cornell in 2001 and is now an assistant professor in the Department of Physics and Physical Science at Humboldt State University in California. There he runs his own version of Ask the Astronomer. He also helps us out with the odd cosmology question.

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