Look up at the stars and ask yourself: what scares me more ? To be alone in the Universe, or to know that there is someone else up there? An age-old question, as valid for you and me as it was for Giordano Bruno when he wrote about an “infinity of worlds” before being burnt at the stake in 1600. But fifty years ago to the day, a letter to Nature ended the passive, look-up-and-ponder attitude by proposing a scientific, experimental approach. We don’t have an answer yet (or you and I would know), but in the process we have come up with quite a tale to tell.
Giuseppe Cocconi (1914-2008) and Phil Morrison (1915-2005) were both accomplished physicists when they wrote “Search for Interstellar Communications” (Nature, Sept 19, 1959). Cocconi started his life in science doing experiments with Nobelist Enrico Fermi and later had a brilliant career at the European Particle Physics Laboratory, CERN, in Geneva. Morrison, Institute Professor at MIT, had been a group leader in the Manhattan Project.
Their Nature letter reported the obvious. At the time, they had no evidence on the existence of planets around stars, had no clue on the emergence of life on them, much less on any evolution of technological societies. Anyway, they said, if there really are intelligent beings out there somewhere, they may have established a channel of communication, aimed also at us.
It’s easy to see that such a channel should probably use radio waves, as the most efficient way of transmitting a signal. Cocconi and Morrison suggested frequencies for us to listen in on, using the new antennas of radio-astronomy, just then coming of age. They had no clue as to what to listen for, of course. Prime number sequences ? Digits of pi? No use guessing, just trust them.
The suggestion of the two physicists fired quite some enthusiasm. Almost immediately, Frank Drake, at the newly created National Radio Astronomy Observatory, started Project Ozma, the first radio search for an intelligent signal. Since then, over 100 search programmes have been carried out, culminating in the biggest of them all, SETI (Search for ExtraTerrestrial Intelligence), still going strong.
All to no avail, of course: not an intelligent peep on any antenna. Does this mean that we are alone in the sky? Not at all. Francis Bacon wrote: “they are ill discoverers that think there is no land, when they can see nothing but the sea”. Dr. Jill Tarter, of the SETI Institute, likens their null result to denying the existence of fish in the ocean after picking up a glass of sea water and seeing no fish in it.
SETI itself, and its predecessors, have prompted a small revolution in science, technology and sociology. Over fifty years, our ability to search for radio signals has increased ten thousand times more than the increase in sensitivity enjoyed by all optical astronomy in the 400 years since Galileo. SETI has also been able to survive dramatic funding cuts, notably from NASA, and is now thriving on mostly private support. And it does so through an extraordinary involvement of the public.
The enormous computer power necessary to process all of the radio signals collected from the sky is now enthusiastically supplied by a network of close to a million PCs. Simply download SETI software as your (fascinating) screensaver and you could, one day, be the first to spot an extraterrestrial signal - an irresistible prospect to many.
Meanwhile, astronomy from ground and from space has found extrasolar planets. The first was discovered in 1995 around a non-descript, local star. Nearly 400 more are now catalogued in one of the greatest ever leaps of astronomical discovery. We have today a good insight into the existence of planets: we know they are the norm, not the exception, around stars.
With 100 billion stars in our Galaxy alone, and if many of them have planets, we have ground for optimism about the emergence of life somewhere else. While we are still waiting for definite results from Mars, data are accumulating on organic materials in outer space. Some important building blocks of life, such as amino acids and sugars, are now routinely found in meteorites and in extraterrestrial environments. Recently, NASA brought back some amino acids, straight from a comet’s tail.
Complex organic molecules just randomly present in the stuff our Solar System was made from? Panspermia confirmed? Too early to tell. The only thing we can safely discard is the “directed panspermia” theory of Francis Crick and Leslie Orgel. In 1973, the DNA Nobel discoverer and his co-author theorized that “organisms were deliberately transmitted to earth by intelligent beings on another planet”. That would require living matter travelling to us from another star. An implausible prospect, we now think.
While we are making palpable progress on the emergence of life, we are definitely stuck on assessing the chances of life forms becoming capable of sending radio signals. We still have a sample of just one, our own planet. The visible proof of it, from the outside, is a sphere of radio and TV waves, expanding in all directions at the speed of light. In the century that has elapsed since Guglielmo Marconi started sending radio signals, this sphere must have engulfed the many stars surrounding us within 100 light years. Of course, it has become much stronger in recent decades: in Italy, it is affectionately known as the “Berlusconi Bubble”.
It is debatable if TV commercials represent the right message our civilization wants to convey to our galactic neighbours. What cannot be debated, however, is the final sentence of Cocconi and Morrison, urging us to listen for interstellar messages: “… success is difficult to estimate, but, if we never search, the chance of success is zero”.
Published on International Herald Tribune (October 6, 2009)
