A senior astronomer has said that the hunt for alien life should take into account alien "sentient machines".

Seti, the Search for Extraterrestrial Intelligence, has until now sought radio signals from worlds like Earth.

But Seti astronomer Seth Shostak argues that the time between aliens developing radio technology and artificial intelligence (AI) would be short.

Writing in Acta Astronautica, he says that the odds favour detecting such alien AI rather than "biological" life.

Many involved in Seti have long argued that nature may have solved the problem of life using different designs or chemicals, suggesting extraterrestrials would not only not look like us, but that they would not at a biological level even work like us.

However, Seti searchers have mostly still worked under the assumption - as a starting point for a search of the entire cosmos - that ETs would be "alive" in the sense that we know.

That has led to a hunt for life that is bound to follow at least some rules of biochemistry, live for a finite period of time, procreate, and above all be subject to the processes of evolution.

But Dr Shostak makes the point that while evolution can take a large amount of time to develop beings capable of communicating beyond their own planet, technology would already be advancing fast enough to eclipse the species that wrought it.

"If you look at the timescales for the development of technology, at some point you invent radio and then you go on the air and then we have a chance of finding you," he told BBC News.

"But within a few hundred years of inventing radio - at least if we're any example - you invent thinking machines; we're probably going to do that in this century.

"So you've invented your successors and only for a few hundred years are you... a 'biological' intelligence."

Full article/source - http://www.bbc.co.uk/news/science-environment-11041449