RACHEL MARTIN, HOST:
Have you ever gazed out your window on a clear, star-filled night and wondered are we really alone?
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MARTIN: Well, there is new science research out there that suggests we may not be after all. The study is based on findings from NASA's Kepler Spacecraft, and it found that there could be as many as 40 billion habitable Earth-sized planets in the galaxy. To help us digest the enormity of this news, we've called up Mike Brown. He is a professor of planetary astronomy at the California Institute of Technology. Thanks so much for being with us.
MIKE BROWN: Oh, thanks for having me.
MARTIN: So, what did you think when you first heard the result of this study this past week? I mean, you deal in this kind of stuff all the time, but was this different?
BROWN: I think even I was a little surprised at just the tremendous number, the incredible likelihood that if you find a star like the Sun that there will be some sort of planet of the size of the Earth around it. That just astounded me.
MARTIN: Even someone like you. You've got maybe a little tingling feeling?
BROWN: I think I did. I think I really did do that thing you say. I went and looked up at the sky and just thought, you know, these things we see up there, there really are other worlds up there.
MARTIN: So, over the last two decades, there have been multiple studies showing similar results that there is likely to be life resembling life on Earth elsewhere in the universe. What does that tell us about our galaxy?
BROWN: I would say that so far we haven't found any evidence that life is likely. I'll keep using the science weasel word, which is life is possible in many places. The problem with life is that the one thing we don't know about life is it easy to start it or is it really hard to start it? And all we know is that it started on Earth. So, there could be 40 billion planets exactly like the Earth in the galaxy and not a single one had life on it, or there could be 40 billion planets like the Earth in the galaxy and every single one of them has life on it.
MARTIN: I mean, unfortunately, there's so much ambiguous language here that's frustrating, I imagine for you too. What does your gut tell you, Mike? The big question: do you think we're alone in the universe?
BROWN: If you have to guess whether life is easy to start or hard to start, I am biased towards easy to start. And I think most people are biased towards easy to start because we live on a planet with life. But you have to realize how biased we are. So, maybe it's not as easy as I think to start that life in the first place.
MARTIN: I think we can still believe.
BROWN: I think that's OK.
MARTIN: Mike Brown is a professor of planetary astronomy at Cal Tech. He's also the author of the book "How I Killed Pluto and Why It Had It Coming." He joined us from member station KPCC in Los Angeles. Thanks so much for being with us.
BROWN: Thank you. It was my pleasure.
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