It has been suggested that the next generation of radio telescopes, such as LOFAR, now being built in the Netherlands, could be used to detect radio noise from alien radio and TV. So Marko Horvat, a computer scientist at the University of Zagreb, Croatia, calculated the odds of detecting alien civilisations of different lifespans from their radio signals. If, for example, 10 civilisations, each with a lifespan of 250,000 years, live within radio reach of Earth, the probability that one of them will be detected is about 9 per cent. That sounds good, but it assumes we have near-perfect telescopes scanning the entire sky constantly - an ideal far from being realised. "We need much better telescopes," Horvat says.