Under the Microscope: Popular belief that the earth is regularly visited by intelligent alien life is widespread. This belief persists despite the fact that the evidence to support it is flimsy in the extreme. The reason we are so willing to believe in alien visitations is probably deep-rooted in human psychology - we don't want to be alone in an unimaginably immense universe, writes Prof William Reville.
Science has no problem with the concept of alien intelligent life. Quite the opposite in fact. Most scientists would accept that it is highly probable that we are not alone in the universe. The reason for thinking this is straightforward. Science believes that life arose on earth almost four billion years ago from lifeless chemicals and understands how it evolved from that original simple single form into the myriad forms of life, including human life, that presently populate the earth. There is no reason in principle therefore to think that equivalent events have not happened on earth-like planets elsewhere in the universe.
For the last 70 odd years, human civilisation has been broadcasting evidence of its existence to the universe at large in the form of radiowaves. These waves, emanating from our radio/television newscasts and entertainment programmes, shoot off into outer space at the speed of light. We have also deliberately sent radio messages into space, giving basic information about life on earth, hoping to contact alien civilisations. And, since we are doing this, we expect that alien civilisations elsewhere in the universe who are at least as technologically capable as ourselves, will be doing likewise. A widely known scientific enterprise has been established, called the Search for Extraterrestrial Intelligence (Seti), that actively scans the skies for incoming radio messages from alien civilisations. No messages have been detected to date.
In 1977, Voyager 1 and 2 space probes were launched. They carry special golden records that bear recordings of life on Earth - pictures of people, scenery, plants, the song of a whale and greetings from Earth in 55 languages. They also locate Earth in our solar system, and our solar system in the galaxy. The records bear instructions for how they should be played.
The physicist Dr Frank Drake has estimated the likely number of alien civilisations in our own Milky Way galaxy that may be attempting to contact other civilisations and he has expressed his calculations in an equation called the Drake Equation. This takes into account the rate of formation of stars like our sun, the proportion that have orbiting earth-like planets, the proportion of these on which life arose, and so on. Drake estimates that our Milky Way contains 10,000 civilisations interested in making communications with others.
Scientists believe that by far the most likely way an alien civilisation on another planet might learn of our existence would be by detecting and deciphering our radio signals. Having detected our signals they might then be moved either to signal back to us or to physically come to visit us, or both. We have detected no intelligent radio signals yet and it also seems extremely unlikely that physical visitations could have occurred. Intelligent radio signals have emanated from earth only for the past 70 years. Even if aliens made a beeline for earth, travelling at the speed of light, immediately on receipt of our signals, only aliens from the few nearest star systems to earth could be involved and the probability that these star systems harbour intelligent life is remote.
The best known "alien visitation" incident occurred in the desert near Roswell, New Mexico in 1947, where members of the public witnessed something crashing to earth. Witnesses also saw "alien bodies" being removed from the wreckage. The US airforce was quickly on the scene and took away the debris. An army press officer first described the object as a flying saucer, but this was quickly denied and it was claimed that the object was an army weather balloon.
This confusion was seized on by unidentified flying object (UFO) supporters who claimed that the whole thing was a huge cover-up. The US airforce conducted a comprehensive investigation of the incidence in 1994 and confirmed that the object that crashed was a weather balloon and the "alien bodies" were test dummies on board the balloon.
UFO enthusiasts continue to believe that an alien craft crashed at Roswell in 1947 and that the US government covered the whole thing up. The Roswell incident inflamed interest in UFOs around the world and this interest persists. Belief in alien visits to earth is now widespread. A US National Science Foundation poll in 2001 found that 30 per cent of people believe that some of the many UFOs "sighted" every year come from alien civilisations. Sixty one per cent of British teenagers believe that aliens visit earth.
Why are people so willing to believe that aliens are visiting earth? It's not that the evidence amounts to much. Despite the hundreds of thousands of UFOs that have been sighted over the years I don't think there is even one clear photograph of a craft that cannot be clearly identified as an earthly creation. The weight of evidence that exists doesn't seem to weigh more than the evidence for the existence of Big Foot, Nessie or The Abominable Snowman.
The reason so many are willing to believe in current visitations by aliens is probably psychological. We are social animals and fear solitude. Deep down we fear the idea that we may be alone in the universe and we would wish it otherwise. We don't want to be alone. William Reville is Associate Professor of
Biochemistry and Public Awareness of Science Officer at UCC, http://understandingscience.ucc.ie