SAN JOSE, United States - For decades, US astrophysicists seeking to make contact with extraterrestrials have basically just been listening for signals from space.
But now they want to turn the tables and start sending signals of their own - powerful ones - to see if any intelligent life is out there in the cosmos.
Researchers at the SETI Institute in California - SETI stands for Search for Extraterrestrial Intelligence - hope to get the project, called Active SETI, underway soon.
On Thursday, they rejected fears by scientific icons, including Stephen Hawking, who say such behaviour could encourage aliens to invade earth.
"For fifty years astronomers have been pointing radio telescopes at stars looking for signals from other civilizations," said Douglas Vakoch, director of interstellar message composition at the SETI Institute.
"With Active SETI, we reverse that process and are taking an active role in transmitting intentional, powerful, information-rich signals to other civilizations in the hope of getting a response," he told the American Society for the Advancement of Science's (AAAS) annual meeting in San Jose, California.
Signals would be sent to star systems that are relatively close and made up of planets that could potentially be inhabitable.
These researchers say this approach is more promising than previous attempts to establish contact with extraterrestrials, such as a phonograph record placed aboard two Voyager spacecraft in 1977 containing sounds and selected images chosen to try to depict life on Earth.
Radio signals have, in fact, already been sent out into space. In 1999, Russian scientists sent messages with a telescope based in Crimea.
'Across the Universe'
And in 2008 NASA beamed the Beatles song "Across the Universe" at the North Star, 430 light years away.
By using today's more powerful radio telescopes, researchers say they should ping the stars with the entire content of the Internet. That would allow any civilization that gets the message to decipher the history of humanity and its culture, said Seth Shostak, senior astronomer at the SETI Institute.
The team acknowledges that their project is controversial. Scientific luminaries have expressed reservations at the idea, including the British astrophysicist Hawking, who has said such transmissions would be "irresponsible." Hawking pointed out that history is full of tragic clashes for less advanced civilizations, such as the Incas as they dealt with the Spanish conquistadors.
But the proponents of Active SETI adamantly dismiss such arguments as paranoia.
Shostak said it is too late to "worry about provoking aliens with deliberate transmissions." He added: "Any alien society that is advanced enough to launch an attack and vaporise Earth can easily pick up the broadcasts we've been sending into space since the Second World War." He argued that if sending signals out into space were banned, so should the use of military and airport radar systems, and, for that matter, street lights in towns and cities.
"Such paranoid actions would cripple the activities and progress of every succeeding generation of humanity," Shostak said.
Rejecting claims of paranoia, David Brin, an astrophysicist and science fiction writer, called for a delay in sending ET-seeking out messages.
"We propose a consensus call for international and public consultations before humanity takes a brash and irreversible step - shouting our presence into the cosmos," Brin told the conference.