Where Are All the Aliens?

Paul Davies is a theoretical physicist, cosmologist, astrobiologist, and bestselling author. He is Director of the Beyond Center for Fundamental Concepts in Science and co-Director of the Cosmology Initiative, both at Arizona State University. Previously he held academic appointments at the Universities of Cambridge, London and Newcastle upon Tyne in the UK, before moving to Australia in 1990, initially as Professor of Mathematical Physics at The University of Adelaide. Later he helped found the Australian Centre for Astrobiology in Sydney.

Davies’s research focuses on the “big questions” of existence, ranging from the origin of the universe to the origin of life, and include the nature of time, the search for life in the universe, and foundational questions in quantum mechanics. He helped create the theory of quantum fields in curved spacetime, with which he provided explanations for how black holes can radiate energy, and what caused the ripples in the cosmic afterglow of the Big Bang. In astrobiology, he was a forerunner of the theory that life on Earth may have come from Mars. He is currently championing the theory that Earth may host a shadow biosphere of alternative life forms.

Davies has lectured on scientific topics at institutions as diverse as The World Economic Forum, the United Nations, the Commission of the European Union, Google, Windsor Castle, The Vatican and Westminster Abbey, as well as mainstream academic establishments such as The Royal Society, The Smithsonian Institution, and the New York Academy of Sciences. Davies devised and presented a series of 45 minute BBC Radio 3 science documentaries and a one-hour television documentary about his work in astrobiology, entitled "The Cradle of Life." Among his bestselling books are "The Mind of God," "How to Build a Time Machine," and "The Goldilocks Enigma." His latest book, "The Eerie Silence," was published by Houghton Mifflin Harcourt in 2010.
  • Transcript


Question: What is the SETI program?

Paul Davies:  SETI is the Search for Extraterrestrial Intelligence and it addresses the question, “Are we alone in the universe?”  This is a question which goes back to the dawn of history, but for most of human history it has been in the province of religion and philosophy.  Fifty years ago, however, it became part of science and the trailblazing work of a young astronomer named Frank Drake set the trend.  Frank decided to start scanning the skies with a large radio telescope in the hope of stumbling across a message from ET.  It seemed a somewhat quixotic enterprise when he began, but over the years it has grown and grown.  It’s now an international effort and I think it is taken seriously by many scientists and so it really consists of using radio telescopes, choosing target stars where it is conceivable there might be some sort of advanced alien civilization and hoping that they might be beaming radio messages our way and so the 50th anniversary of this it seemed to me a good time to take stock because after all, we’ve had nothing but an eerie silence in 50 years, so these astronomers have been patiently pursuing this quest.  I might say Frank Drake himself is still in the game 50 years on.  Now this is heroism of an unusual sort.  Who else do you know who has devised a scientific experiment and has pursued it for 50 years, got a null result and is still smiling and optimistic? So Frank Drake is a great hero of mine and I admire his zeal and positivism, but it is just an eerie silence and so the question is are we doing the wrong thing.  Should we be looking somewhere else or in some other way?  Should we broaden the search?  And my conclusion is really that I think what the SETI people are doing is just great and I hope they go on doing it and doing it better, but meanwhile, we should start thinking outside the proverbial box a bit to see if there are other ways in which we could try to track down ET.

Question: Is this silence more likely due to aliens’ nonexistence or to flaws in our search methods?

Paul Davies:  If you ask the astronomers of the sharp end of SETI why they think there has been an eerie silence they’ll say, “Well we only have been doing it for 50 years. We’ve just started. What more do you expect? It’s a big universe out there.”  And in fact, to put that into context they look carefully.  It’s just a few thousand stars.  There are 400 billion stars within our Milky Way galaxy alone, so it is a needle in a haystack search.  Of course it’s easy to conclude simply that they just haven’t been doing it long enough or hard enough—it’s no surprise they haven’t heard anything, but the alternative is that we are indeed alone in the universe, and it’s impossible to answer that question because there are so many unknown factors.  If we’re looking for intelligence in the universe I think everybody assumes that this has to start with life and so the question is: "How likely is it that there will be life elsewhere in the universe?"

Now when I was a student almost nobody thought there was any life beyond Earth.  Today it’s fashionable to say that there is life all over the place, that the universe is teeming with it, but the scientific facts on the ground haven’t really changed.  We’re still just as ignorant as we were 40 or 50 years ago about how life began.  We’ve got a very good theory of the evolution of life once it gets started, but how does it get going in the first place.  We don’t need a blow by blow account of exactly how it got going on Earth, but we would at least like to know whether it was a very probable event or very improbable event and in our present state of ignorance we can’t even pin that down.  We can’t even bracket the odds.  It could have been a stupendously improbable fluke, a freak chemical accident that occurs just once in the universe or it could be that life emerges automatically and naturally as part of the underlying scheme of things.  Maybe the universe has intrinsically bio-friendly laws that brings life into being all over the place.  We don’t know.   It’s only fashion that has said the pendulum has swung from extreme skepticism about extraterrestrial life to extreme credulity.  The truth is somewhere in between, but to pin it down we’ve really got to address that question, how likely is it that life will arise on an Earth-like planet.  I should say we know that there are many, many other Earths out there.  We’re almost certain that there will be upwards of a billion Earth-like planets in our galaxy alone, so there is no lack of real estate where life might happen, but what we don’t know is how likely it is given the real estate, given a wonderful pristine planet like Earth how likely is it that life will pop up inhabited?  We don’t know the answer to that.

Recorded April 15, 2010
Interviewed by Austin Allen