Seti aff •seti neg •Asteroids Aff

Article: Aliens Don’t Exist

After decades of employing radio telescopes in vain bids to hear E.T. phoning home, and after studying patterns of evolution on Earth, they believe that complex, brainy extraterrestrials must be rare, if not non-existent.

Life may be ubiquitous, they admit, but only on our planet did it evolve into beings capable of rational thought, sophisticated behaviour and powerful civilisations. On other worlds, it has remained rooted at the level of amoebas, microbes, and primitive pond life.

All aliens are scum, in other words - an observation with crucial implications. As UK astronomer Ian Crawford points out in the latest issue of Scientific American , we may be 'the most advanced life-forms in the galaxy'.

'We used to think that once life emerged on a planet, intelligent beings would inevitably appear,' added Dr Ian Morison, director of Seti research at Britain's Jodrell Bank radio telescope. 'Now, it seems we only evolved thanks to an extraordinary series of fortuitous events.'

The first and most important of these lucky breaks concerns location, as astronomers Peter Ward and Donald Brownlee recently revealed in Rare Earth: Why Complex Life is Uncommon in the Universe (Copernicus). Earth - far from being an average world in an unimportant part of the cosmos - turns out to be prime galactic real estate.

First, our sun is a highly stable star and is unaffected by wild fluctuations in output of its radiation. Such afflictions emanate from many other stars and would destroy evolving advanced life-forms, allowing only bacteria-like entities to flourish.

In addition, ours is a safe suburban part of the galaxy, the astronomical equivalent of Cheltenham. By contrast, in more crowded, 'down-town' galactic neighbourhoods, in stellar Sauchiehall Streets of the universe, jostling stars are likely to have continually dislodged the swathes of comets believed to hover at the edges of most solar systems. These comets would then have crashed into each star's family of planets - with devastating consequences for their evolving life-forms.

In addition, Earth has a planetary big brother, Jupiter, which sweeps up those few dangerous comets that do make it through to the solar system's inner regions, while our world is further blessed in having a relatively large moon which helped stabilise Earth's rotation, preventing wild swings in our seasons and climate.

All these improbable conditions, in combination, provided the stability that allowed four-billion-year-old primitive slime to evolve - about 250,000 years ago - into the only intelligent creatures known to science, ourselves. Humanity may therefore be viewed as the outcome of the biggest accumulator bet in the universe. As Professor Brownlee, of Washington University, Seattle, puts it: 'Earth is a charmed place. We know of no other body that is even remotely like it.'

The idea that Earth is special runs counter to the entrenched astronomical assumption that our planet is not even mildly important. It also reverses a trend that was begun in the Sixties by astronomers, including Carl Sagan, who argued that ET civilisations must be two-a-penny, and that there should be thousands, possibly millions, in our galaxy.

For the past 30 years, astronomers have tried to pick up radio signals from these alien worlds - either from their TV broadcasts, or from radio beacons deliberately sent into space. But scientists have detected nothing but hiss and static.

The Astronomer Royal, Sir Martin Rees, believes the jury is still out on ETs. 'We still have only searched a relatively small part of our galaxy. There is still plenty of time and space to find extraterrestrial intelligences. In any case, intelligent beings may simply not want to talk to us, or have any way of knowing about us. For example, they could be dolphin-like beings having a calm time, thinking deep thoughts on an aquatic world.'

Or as the Open University astronomer Professor Colin Pillinger - designer of the British Beagle 2 probe scheduled to land and seek life on Mars in 2003 - points out: 'We may simply not realise that aliens are trying to contact us now. When astronomers first detected regular pulses that were emanating from rotating neutron stars, they thought they were listening to little green men. For all we know, we could be listening to alien messages, thinking they are bursts of radiation being produced by stars or galaxies.'

Nevertheless, the sceptics insist we should have seen some sign of alien life by now. Even if only a few extraterrestrials achieved complex, intelligent status, their existence should have become apparent, they argue. Armed with only relatively crude interstellar rocket drives, aliens should have been able to 'colonise the entire galaxy on a cosmically short timescale,' states Crawford in Scientific American .

One answer, according to evolutionist Stephen Jay Gould, has chilling implications. 'Perhaps any society that could build a technology for such interplanetary travel must first pass through a period of potential destruction where technological capacity outstrips social or moral restraint. Perhaps, no, or very few, societies can ever emerge intact from such a crucial episode.'