"The Search for Extraterrestrial Intelligence (SETI) has been dominated for its first half century by a hunt for unusual radio signals. But as he prepares for the publication of his new book The Eerie Silence: Are We Alone?," Paul Davies tells Physics World readers why bold new innovations are required if we are ever to hear from our cosmic neighbours.
Writing exclusively in March's Physics World, Davies, director of BEYOND: Center for Fundamental Concepts in Science at Arizona State University in the US, explains why the search for radio signals is limited and how we might progress.
As Davies writes, "speculation about SETI is bedevilled by the trap of anthropocentrism - a tendency to use 21st-century human civilisation as a model for what an extraterrestrial civilisation would be like... After 50 years of traditional SETI, the time has come to widen the search from radio signals."
Questioning the idea of an alien civilisation beaming radio signals towards Earth, Davies explains that even if the aliens were, say, 500 light years away (close by SETI standards), the aliens would be communicating with Earth in 1510 - long before we were equipped to pick up radio signals.
While SETI activity has been concentrated in radio astronomy, from Frank Drake's early telescope to the more recent Allen Telescope Array, astronomers have only ever been met with an (almost) eerie silence.
Davies suggests that there may be more convincing signs of intelligent alien life, either here on Earth in the form of bizarre microorganisms that somehow found their way to Earth, or in space, through spotting the anomalous absence of, for example, energy-generating particles that an alien life form might have harvested.
"Using the full array of scientific methods from genomics to neutrino astrophysics," Davies writes, "we should begin to scrutinise the solar system and our region of the galaxy for any hint of past or present cosmic company."
Following the publication of his book, The Eerie Silence, Davies will be giving a Physics World webinar at 4pm (BST) on Wednesday 31 March. You can view the webinar live at www.physicsworld.com or download it afterwards.
Explore further: Cosmologist Paul Davies explores notion of 'alien' life on Earth