Letter: Little hope for hunt in cosmic haystack

Sir: The report ('Is there anybody alien there?', 28 September) on the Search for Extra-terrestial Intelligence (Seti) omits mention of the enormous odds against

success.

Mankind has existed for only about 100,000 years of the roughly 15,000 million years of the life of the universe. Use of radio has been possible for less than 100 years. If we accept the statistical argument (and I remain sceptical) that the universe has produced not only many planets teeming with life but also numerous other intelligent communities, we must also accept that they will be dispersed throughout the vast age and distances of the universe. We also have no scientific reason, only hope, for assuming that a technological community like ours would survive and continue transmitting for thousands or even hundreds of years.

Thus other communities might have matured to our level (or beyond) and died at any time in, say, the last 10,000 million years. The finite speed of radio waves and their ephemeral existence prevent us from 'hearing' signals from planets that are not separated from us by the exactly right combination of space and time. Thus a community 50,000 light years away (in our own galaxy) would have to have sent its signals very close to 50,000 years ago. A community that has matured at the same time as us can only contact us if it is very close - statistically unlikely.

One wonders if those who approved the budget for Seti appreciated the minimal opportunities for finding something in the cosmic haystack - or were they, as so many seem to be, desperately seeking a reassurance that 'we are not alone'?

Yours faithfully,

KEN MANLEY

Maidenhead, Berkshire