Where Are All the Aliens?

Question: What is the SETI program?

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Paul\r\nDavies:  SETI is the Search\r\nfor Extraterrestrial Intelligence and it addresses the question, “Are we\r\n alone\r\nin the universe?”  This is a\r\nquestion which goes back to the dawn of history, but for most of human \r\nhistory\r\nit has been in the province of religion and philosophy.  Fifty\r\n years ago, however, it became\r\npart of science and the trailblazing work of a young astronomer named \r\nFrank\r\nDrake set the trend.  Frank decided\r\nto start scanning the skies with a large radio telescope in the hope of\r\nstumbling across a message from ET. \r\nIt seemed a somewhat quixotic enterprise when he began, but over \r\nthe\r\nyears it has grown and grown.  It’s\r\nnow an international effort and I think it is taken seriously by many\r\nscientists and so it really consists of using radio telescopes, choosing\r\n target\r\nstars where it is conceivable there might be some sort of advanced alien\r\ncivilization and hoping that they might be beaming radio messages our \r\nway and\r\nso the 50th anniversary of this it seemed to me a good time to take \r\nstock\r\nbecause after all, we’ve had nothing but an eerie silence in 50 years, \r\nso these\r\nastronomers have been patiently pursuing this quest.  I\r\n might say Frank Drake himself is still in the game 50\r\nyears on.  Now this is heroism of\r\nan unusual sort.  Who else do you\r\nknow who has devised a scientific experiment and has pursued it for 50 \r\nyears,\r\ngot a null result and is still smiling and optimistic? So Frank Drake is\r\n a\r\ngreat hero of mine and I admire his zeal and positivism, but it is just \r\nan\r\neerie silence and so the question is are we doing the wrong thing.  Should we be looking somewhere else or\r\nin some other way?  Should we\r\nbroaden the search?  And my\r\nconclusion is really that I think what the SETI people are doing is just\r\n great\r\nand I hope they go on doing it and doing it better, but meanwhile, we \r\nshould\r\nstart thinking outside the proverbial box a bit to see if there are \r\nother ways\r\nin which we could try to track down ET.

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Question: Is this silence more likely due\r\n to aliens’\r\nnonexistence or to flaws in our search methods?

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Paul\r\nDavies:  If you ask the\r\nastronomers of the sharp end of SETI why they think there has been an \r\neerie\r\nsilence they’ll say, “Well we only have been doing it for 50 years. \r\nWe’ve just\r\nstarted. What more do you expect? It’s a big universe out there.”  And in fact, to put that into context\r\nthey look carefully.  It’s just a\r\nfew thousand stars.  There are 400\r\nbillion stars within our Milky Way galaxy alone, so it is a needle in a\r\nhaystack search.  Of course it’s\r\neasy to conclude simply that they just haven’t been doing it long enough\r\n or\r\nhard enough—it’s no surprise they haven’t heard anything, but the \r\nalternative\r\nis that we are indeed alone in the universe, and it’s impossible to \r\nanswer that\r\nquestion because there are so many unknown factors.  If\r\n we’re looking for intelligence in the universe I think\r\neverybody assumes that this has to start with life and so the question \r\nis: "How\r\nlikely is it that there will be life elsewhere in the universe?"

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Now when I was a student almost nobody thought \r\nthere was any\r\nlife beyond Earth.  Today it’s\r\nfashionable to say that there is life all over the place, that the \r\nuniverse is\r\nteeming with it, but the scientific facts on the ground haven’t really\r\nchanged.  We’re still just as\r\nignorant as we were 40 or 50 years ago about how life began.  We’ve got a very good theory of the\r\nevolution of life once it gets started, but how does it get going in the\r\n first\r\nplace.  We don’t need a blow by\r\nblow account of exactly how it got going on Earth, but we would at least\r\n like to\r\nknow whether it was a very probable event or very improbable event and \r\nin our\r\npresent state of ignorance we can’t even pin that down.  We\r\n can’t even bracket the odds.  It could have been a\r\n stupendously\r\nimprobable fluke, a freak chemical accident that occurs just once in the\r\nuniverse or it could be that life emerges automatically and naturally as\r\n part\r\nof the underlying scheme of things. \r\nMaybe the universe has intrinsically bio-friendly laws that \r\nbrings life\r\ninto being all over the place.  We\r\ndon’t know.   It’s only\r\nfashion that has said the pendulum has swung from extreme skepticism \r\nabout\r\nextraterrestrial life to extreme credulity.  The \r\ntruth is somewhere in between, but to pin it down we’ve\r\nreally got to address that question, how likely is it that life will \r\narise on\r\nan Earth-like planet.  I should say\r\nwe know that there are many, many other Earths out there. \r\n We’re almost certain that there will be\r\nupwards of a billion Earth-like planets in our galaxy alone, so there is\r\n no lack\r\nof real estate where life might happen, but what we don’t know is how \r\nlikely it\r\nis given the real estate, given a wonderful pristine planet like Earth \r\nhow\r\nlikely is it that life will pop up inhabited?  We \r\ndon’t know the answer to that.

Recorded April 15, 2010
\r\nInterviewed by Austin Allen

"There’s no lack of real estate" where life might spring up in the universe. So why has our search for ET turned up nothing?

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