Sometimes it seems as if the expansion of the social networking phenomenon knows no bounds. And now scientists say even aliens might not be immune to Twitter. They could have been using cosmic 'tweets' to contact us for decades, researchers claim - but we have been missing them. While any 'lost in space' messages wouldn't exactly be restricted to 140 characters, as on the website, a study suggests ET is more likely to send out short, directed messages than continuous signals beamed in all directions. The reason? Because alien civilisations are likely to strive to limit waste and make their signalling technology efficient. 'This approach is more like Twitter and less like War and Peace,' said Dr James Benford, a physicist and president of Microwave Sciences. His twin brother Gregory, an astrophysicist at the University of California, added: 'Whatever the life form, evolution selects for economy of resources. Check this out ...