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 teaming 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 go 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 is said the pendulum is 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 of 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.
In Their Own Words is recorded in Big Think's studio.
Image courtesy of Shutterstock