The most important question facing all of science is finding evidence for intelligent alien life. Before someone who’s chanced upon this webpage dismisses me as a fruitcake (rather than a Cambridge-educated mathematical physicist and currently Science Publisher at Oxford Unversity Press), let me add that the very first conference organized by the Royal Society for its 350th anniversary year was on this very question – and I was there.
The whole of science is founded on what we call the Copernican Principle, after Polish astronomer Nicolaus Copernicus who first proposed that Earth orbited the Sun, rather than the other way around. In doing so, Copernicus was the first person to say humanity has no privileged position in nature when, until this point, Earth had always been the centre of the Universe. Recognizing Earth as simply one of many planets orbiting the Sun, which in turn we came to understand orbits the Milky Way (in turn a part of the Virgo Supercluster and so on), allowed us to talk about the laws of nature as applying equally everywhere, rather than differently on Earth compared with in the heavens.
The Sun is one of a few hundred billion stars in the Milky and, partly through the Kepler Space Telescope, we now understand that most of those stars are accompanied by planets. Then the Milky Way is one of many hundreds of billions of galaxies in the visible Universe.The numbers are so vast as to be almost unimaginable. If intelligent life can come into being here on Earth, it seems inconceivable that it hasn’t happened elsewhere, myriad times across the Galaxy let alone the wider Universe. There’s even a mathematical expression known as the Drake equation that is intended to give the number of intelligent civilizations in the Milky Way:
According to Frank Drake, the number N of detectable civilizations in the galaxy is the product of:
R* (the rate of star formation)
fp (the fraction of stars that have planets)
ne (the average number of earth-like planets per star – ie planets capable of supporting life)
fl (the fraction of those Earth-like planets on which life develops)
fi (the fraction of those planets that have life on which intelligent life develops)
fc (the fraction of those planets with intelligent life that create communications technology)
L (the average lifetime of an advanced civilization)
Let’s make up (and in most cases I do mean invent) some numbers. Say there are 10 new stars in the Galaxy each year (that’s roughly what scientists think); that three-quarters of the stars formed have planets; taking our own solar system as average there’s 1 Earth-like planet per solar system; recognizing life developed very soon on Earth after the planet formed we’ll go with this fraction as 0.8; equally, it took many billions of years for life here to go from single-celled organisms to complex, so let’s call the fraction on which intelligent life develops as 0.001, or one in a thousand; there are various “intelligent” species on Earth, but dolphins are never going to build radio telescopes, so let’s say one in four eventually develop communications technology; finally, once a civilization is able to communicate (perhaps with radio telescopes such as at Jodrell Bank here), I’ll suppose that they remain capable/willing to do this for 100,000 years. Plug those together and we get:
10 x 0.75 x 1 x 0.8 x 0.001 x 0.25 x 100000 = 150
That would suggess there are 150 species spread across the Milky Way who could communicate with us right now (but remember most of my numbers are pure guesswork). Apparently the average of estimates comes out at around 10,000, so I’m possibly being cautious, and one of my estimates that could be considered low is my number here for L. If even a few civilizations find ways not to destroy themselves so they can transcend their original home and spread out into the wider galaxy, that would seriously increase the number for L.
Considering the age of the Milky Way, the Sun is a comparatively young star meaning Earth is a new kid on the block when we think about galactic planet formation. We would expect plenty of civilizations to have formed before ours. If L is large they might still be around, but in this case we would surely see evidence of large-scale engineering projects happening in the galaxy. Yet, when we turn our ever more powerful telescopes skyward, we completely fail to find any evidence of and reorganization of the Galaxy by advanced races.
Some people argue that even if L is small it doesn’t matter. The mathematical physicist John Von Neumann developed the idea of self-replicating machines and this has been applied to autonomous space probes that an advanced alien race could send out into the galaxy to explore/conquer/assist other civilizations. Using this method, the entire Milky Way could be explored within only a few million (yes million, not billion) years, even if the originating civilization had long since died out. But again there is no evidence of such probes anywhere.
If science cannot find evidence for aliens, then the premise of the Copernican revolution is called into question, and we have to recognize ourselves and our homeworld as special after all, which goes on to call into question our entire view of the Universe and basis for understanding it.
One of the most interesting people investigating this area is the brilliant Serbian astronomer Milan Cirkovic, so check him out if you want to know more. This post is called “Where is everybody?” because that is supposedly a question posed by phyisicist Enrico Fermi over lunch with colleagues at Los Alamos National Laboratory. The conversation had turned to the apparent likelihood of intelligent alien life, yet the total absence of evidence for this. This is nowadays known as the “Fermi paradox”.
I have two very different and equally interesting solutions to the problem, both of which I intend to turn into novels or film scripts, so I shall say no more about them for the time being.