Do aliens exist somewhere in our vast universe? It is more than likely, writes Sean Naughton
The idea of intelligent extraterrestrial life occupies the human imagination like no other phenomenon. Has any other hypothesis spawned as many generations of stories, folk tales, TV shows, general discussion, scientific discussion, believers, disbelievers and those who just keep a fascinated eye on the evolving discussion? While we delight in watching aliens on our film and television screens as well as reading about them in novels and hearing urban legends, would we be as enthusiastic if there were other life forms in our universe?
Ancient cultures are replete with stories of beings from distant planets. The Dogons of Western Africa, a people well known for their cosmogony, claim that their knowledge of the existence of the faint star Sirius B, of which they had been aware for over a thousand years, a star which was only discovered by western scientists in 1978, was given to them by a race of people from the Sirius system itself.
Present-day claims of extraterrestrial life are often less absolute then those of the Dogons, but how likely is it that intelligent life has evolved more than once in the universe? An enormous number of factors need to come together before life is even theoretically possible. Many of the molecules needed, such as iron, copper and nickel, occur exceedingly rarely in the universe, as does the medium needed to mix them all together, liquid H2O. An equation that worked out fortuitously for humans seems prohibitively improbable for other aspiring life forms.
There is however no shortage of space for life to get going. Our Sun is one star in a galaxy of a hundred thousand million (100,000,000,000). That works out as twenty stars for every person on Earth.
Of course, stars are not the places to look for life. What we want are planets orbiting these stars, just close enough that water won’t freeze but also just far enough away that it won’t boil away. How many are there? A recent study in the journal Science examined 166 sun-sized stars and found nearly one in four had rocky, earth-sized planets in close, Earth-like orbits. The odds suddenly start to look a lot better.
The famous Italian physicist Enrico Fermi articulated this apparent paradox. The universe is very old and very large, so this should mean a high probability that intelligent life exists. The resultant question is often known as Fermi’s question: so where are they? Statistically, it is highly likely that intelligent life exists; yet this belief seems logically inconsistent with our lack of observational evidence to support it. Either the first hypothesis is incorrect and life is rare, or we simply have not been able to detect it yet.
SETI (Search for Extraterrestrial Intelligence) is a collection of investigative projects that use large radio telescopes to search the sky for evidence of artificial radio signals originating from outside our solar system.
Radio signals penetrate our atmosphere quite well and these signals, travelling at the speed of light, spread out from their source and travel through space in an infinite straight line. Indeed, our plant would be readily detectable to an alien species with an attentive radio telescope. The earth emits considerable radio radiation as a by-product of communications such as TV and radio. These signals have been leaving the surface of our plant, drifting off into space for the last 100 years.
In the early days, SETI enjoyed considerable support from governments. In 1924, when Mars was closer to Earth than any time in a century before or since, the United States declared National Radio Silence Day and during a 36-hour period from August 21-23, with all radios quiet for five minutes on the hour, every hour. This was to aid the cryptographers who had been drafted in from the US Army who were attempting to translate any potential Martian message.
Considered frivolous and having returned no results, the US Congress cancelled the NASA SETI program in 1994.
There are those who argue that the discovery of another race may not necessarily be a good thing. Physicist Stephen Hawking, in his book A Brief History of Time, suggests that ‘alerting’ extraterrestrial intelligences of our existence is foolhardy, citing man’s history of treating man in meetings of civilisations with a significant technology gap.
In pop culture, most notably in film, aliens are portrayed as being far more technologically advanced than humanity, but this assumption is flawed. There is simply no way of knowing the technological advances that other societies have made, if they do exist. In reality, the aliens of our universe will not be those of Star Trek, Star Wars and Mars Attacks! We could be disappointed in the life we discover. Perhaps the reason we have not reached our alien counterparts is that they simply do not have the technology to intercept our radio signals. Assuming that all life forms are more technologically advanced than us seems to be unfounded. Perhaps our extra-terrestial friends are living in a medieval-esque society, with little to no technology.
The discovery of intelligent life outside of our own planet would be a profound revelation that would change the way we think about the nature of being human, and our place in the universe. As the American cartoonist Walt Kelly put it: “there’s only two possibilities: There is life out there in the universe which is smarter than we are, or we’re the most intelligent life in the universe. Either way, it’s a mighty sobering thought.”