By putting a shell of material around a host star, aliens would not only trap much of the star's heat, but also create a unique infrared signature that Earth astronomers could detect.Дiagram of a Dyson Sphere.

Suggestions over the past 50 years include extraterrestrial radio traffic that happens to pass by, or a powerful radio or optical beacon that sweeps the Milky Way galaxy like a lighthouse.ДЄ very advanced alien civilization might have built huge astro-engineering projects called Dyson spheres to directly tap the power of stars. To their credit, SETI astronomers have not ignored the possibilities beyond extraterrestrials deliberately beaming a message straight at Earth. And his many years of supporting SETI have not stopped him from describing the needle-in-a-haystack search as 'a search without any clue as to whether there is a needle there at all, or how large the haystack may be.'

Having worked with SETI for three decades, he has written about his ideas in a book, 'The Eerie Silence' (Houghton Mifflin Harcourt, 2010) and articles such as one that appeared in the online August edition of the journal Acta Astronautica.Д«ut Davies does not think such intelligent alien life must necessarily exist. 'Projects like genomic SETI are an attempt to complement radio SETI, not undermine it.'Дavies wants scientists to broaden their thinking about how aliens could have left behind their mark. 'My proposals aim to spread the burden from a small band of heroic radio astronomers to the entire scientific community,' Davies said. Such a CSI-style forensics search could complement, rather than replace, the Search for Extra-Terrestrial Intelligence (SETI) astronomers who continue to look skyward, said Paul Davies, a physicist and cosmologist at Arizona State University in Tempe, Ariz. If aliens did leave their mark on Earth by some wild chance, we could search for the possible 'footprints' of alien technology or even analyze the DNA of terrestrial organisms for signs of intelligent messages or tinkering.

No contact vs radio silence