Humans should start sending messages to planets in habitable zones in the hope that alien life-forms might hear us, scientists have said.
Space experts at the Search for Extra Terrestrial Life (SETI) project said the time has come to stop passively listening for signs of intelligence in other worlds and actively start seeking contact.
Kepler Space Telescope captured tens of thousands of stars in the constellation of Cygnus and Lyra
SETI was founded 20 years ago to monitor the cosmos for signals of alien life and involves astrophysicists from institutions like Harvard University and the University of California. However as early 1960 scientists were scanning space for clues to other civilizations.
Douglas Vakoch, the Director of Interstellar Message Composition at the SETI Institute, said we should now start devising a message to send to planets which have recently been discovered in the "goldilocks zone" – areas of space where it is neither too hot nor too cold for life to exist.
Kepler-186f, the first validated Earth-size planet to orbit a distant star in the habitable zone
"For over a half century, scientists engaged in the search for extraterrestrial intelligence have sought evidence of the existence of other civilizations by searching for intentional radio signals," he said
"As we move into the next half century we should expand our strategies, so we are not only passively listening, but also transmitting intentional, information-rich signals.
"With recent detections of Earth-like planets in the habitable zones of other stars, we have natural targets for such transmission projects.
"We should repeatedly target a set of nearby stars over the course of several months or years.”
The Kepler Telescope
NASA’s Kepler Telescope has so far found more than 3,800 planets in habitable zones which could hold liquid water, and life. Experts say targeting them with a signal is the best hope of making contact with new worlds.
However the content of a message has been hotly debated. To find out what humans would like to say to aliens, SETI founded a site called Earth Speaks and asked people to devise an interstellar message.
The smallest-ever planet outside our solar system has been spotted by NASA's Kepler space telescope - a rocky planet similar in size to the Earth
While women tended to offer friendship, and even coffee and biscuits in their missives, men were more likely to talk about science and inquire about their civilisation. Overall the main theme was asking for help from aliens rather than seeking to impart the wisdom of Earth.
Mr Vakoch said humans have a "cosmic inferiority complex" and automatically assume that extra-terrestrials will be more technologically advanced than us and so have nothing to learn.
But he added: "Humankind has a range of experiences and insights that cannot be imagined by any other civilization.
"Though extraterrestrials may be more technologically advanced we are, they will never be more human. It’s the breadth of our human experience that we should be conveying in our interstellar messages."
The experts at SETI say that governments must start working together to devise the message. The equipment to send basic messages already exists and scientists say that reluctance ‘more political than technical.’
Seth Shostak, Senior Astronomer and Director, Center for SETI research, said some people resisted the approach, fearing it could alert our presence to dangerous extra-terrestrial races.
"It’s very controversial,” he said, “There are some people who think this might be dangerous.
"The idea that you are somehow endangering Earth I don’t think holds any water because we have been broadcasting into space willy nilly since the Second World War – televisions, FM radio and radar.
"These signals have been going into space for 70-somethng years so they are quite far out and any society that could come to Earth and incinerate Belgium, if they think they deserve it, is fully capable of picking up these broadcasts.”
But he admits that it is a gamble whether visiting aliens will come in peace.
“Nobody knows if they are friendly or not,” he added.
“You could be optimistic and think they are all friendly or figure they are like ones in the movies and hellbent on destruction. I suspect there is a whole range.
“Earth has been sitting around for 4 billion years with life on it and nobody’s thought to destroy it.
“It may be they want to proseltyse. The other thing is that they are just interested in the culture – that’s what’s special about us. Maybe they are interested in rock ‘n’ roll. Maybe they want Cliff Richard.”
However American scientist and futurist David Brin believes it is a mistake to try and contact alien worlds.
"We are the youngest of all technological races in the cosmos, like an orphan child who suddenly finds herself wandering a strange jungle that’s quiet, too quiet,” he said.
"Perhaps you have the kind of personality that says: "What the heck! I might as well shout and see what happens!"
"That’s all very well if the only one you are putting at risk is yourself. But when that risk is also imposed upon our children -- all of humanity and our planet – is it too much to ask that we discuss it first?"
The scientists were speaking at the annual Association for the Advancement of Science AAAS annual conference in San Jose.
