flowerpot metronomic: The search for ET is a detective story without a body

Nigel Henbest, contributor

(Image: Plainpicture)

Paul Murdin investigates the possibilities of nearby alien life in Are We Being Watched?, but neglects to cover more thrilling aspects of the quest

OVER lunch at Los Alamos National Laboratory in 1950, a group of leading physicists turned their minds to flying saucers, and the possibility of interstellar travel. "Where is everybody?" Enrico Fermi exclaimed. As his colleagues laughed, Fermi performed a legendary back-of-an-envelope calculation showing that aliens - if they exist - should have visited Earth many times over.

If they've been here, then perhaps they are watching us - hence the provocative title of Paul Murdin's new book. As one of the team that discovered the first black hole in our galaxy, Murdin is an astrophysicist of impeccable credentials. But in weighing up the evidence for alien life, Murdin has to confront one insuperable obstacle: there is no evidence for even microbial life beyond Earth. So the Herculean task of writing a book on alien life is the ultimate detective story without a body.

Murdin seems to draw his inspiration from the poet Alexander Pope's famous quote that the "proper study of mankind is man". His discussions centre mainly on Earth's indigenous life, with the premise that alien life follows much the same pattern: evolution and survival of disasters to culminate - after much the same lapse of time - in intelligent creatures pretty similar to us.

He also investigates the possibility of microbial life on our neighbouring worlds, including the frozen deserts of Mars and the icy depths of Saturn's moon Enceladus, along with its peer Titan, which is coated with a sorbet of chemicals with the potential for creating life. There is even a chance that alien fish swim in the deep oceans of Europa, the icy moon circling Jupiter.

If that is what you are looking for, then Murdin is an excellent and thoughtful guide. But when it comes to a deeper discussion of the search for life beyond our solar system - and especially intelligent aliens - we are frustratingly short-changed. There is only a cursory discussion of the fascinating zoo of planets now being discovered around other stars. Many of these new worlds are so hot or cold, water-covered or parched, that our best clues to life there come from Earth's most hardy life forms. Yet these amazing extremophiles are dismissed in a single page.

Alien life is a subject that sparks off-the-wall ideas and excitement that are largely lacking here. Take the physical appearance of aliens. Admittedly, this is a pretty nebulous subject, but some evolutionary biologists such as Jack Cohen have taken a hard look at what might be possible. And communications researchers like Laurance Doyle have derived algorithms that can tease out meaning from apparently random patterns of sound, providing hints about how aliens might communicate.

The global Search for Extraterrestrial Intelligence project (SETI) is the key to finding intelligent life out there. Murdin gives a full account of SETI up to 1977, but squeezes its subsequent history into a page. There is nothing on the searches that have targeted individual stars, including those with newly discovered planets, nor on the world's most sensitive eavesdropping radio ear on the cosmos, the Allen Telescope Array. Murdin is silent on recent searches for laser signals from alien intelligence, and on attempts to track down tell-tale infrared emissions from advanced civilisations. And we also learn nothing of efforts to detect alien artefacts in the solar system. That's not as daft as it may sound: if Fermi was right, and aliens have visited, then where's the rubbish they left behind?

For the science of the solidly known - with references and footnotes - Murdin has written a thorough survey. But he stops short of providing the thrill that would come from answering the provocative question in the title.