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...Dr Shostak says that artificially intelligent alien life would be likely to migrate to places where both matter and energy - the only things he says would be of interest to the machines - would be in plentiful supply. That means the Seti hunt may need to focus its attentions near hot, young stars or even near the centres of galaxies. "I think we could spend at least a few percent of our time... looking in the directions that are maybe not the most attractive in terms of biological intelligence but maybe where sentient machines are hanging out."