Sydney - The scientist leading Australia's efforts to find signals from intelligent life on other planets warned on Tuesday we should think twice before replying.
Professor Matthew Bailes of Swinburne University in Melbourne told dpa of his excitement at learning that he was in charge of part of the Breakthrough Prize Foundation's $100m search for alien life, financed by Russian billionaire Yuri Milner.
But when asked what he would do if he actually found a signal sent by aliens, Bailes paused.
"I think we should think very carefully before we reply to a signal received from outer space," he said.
Bailes said aliens who could transmit such a powerful signal that it could reach Earth over tens of thousands of light years would have to be far more advanced than us.
"The history of weak civilisations contacting more advanced civilisations is not a happy one," he said.
Bailes is in charge of the multi-million dollar contract Australia has signed with the Breakthrough Prize Foundation project using the radio telescope at Parkes, 356km west of Sydney.
The initiative has been described as the biggest ever scientific research projects looking for signs of intelligent life, and will cover 10 times more area of sky than previous programmes.
Milner described it on Monday as bringing a "Silicon Valley approach to the search for intelligent life" in an initiative backed by British scientist Stephen Hawking.
His project has bought a quarter of the time that the Parkes radio telescope scans the universe.
Bailes said sophisticated computers will have to be installed at Parkes that can detect patterns or likely signals. Unlike the movies, there will be no one watching screens for alien signals from space.
"These computers will have to sort through a billion samples a second trying to find a pattern or what could be a signal."
The Parkes radio telescope, one of the largest on Earth, has a proud history of space exploration. It was first in the world to receive transmissions in 1969 from Apollo 11 showing Neil Armstrong setting foot on the Moon.
However, it will take a year to build the computers to be able to sort through the massive variety of noise coming from deep space to pick out a possible signal. Five years has been set aside for the search.
"The difficulty is to know what sort of signal we are looking for. There is no manual on how to find aliens. We'll have to imagine the sort of transmissions an alien race might send, and a variety of strategies will have to be deployed ranging from looking for single bursts to signals that might be more encoded in other transmissions."
"The signal is likely to be quite feeble after coming vast distances. We'll need to be looking for advanced civilisations that have significantly more transmission grunt than we are capable of on Earth.
"Hopefully they send a transmission pattern we can recognise such as prime numbers, or a mathematical construct at a frequency that might have some significance to us."
If the team does detect a pattern or likely signal it will have to be thoroughly checked and double checked by many scientists before they tell the world they have found a signal from an alien race.
"There is a protocol for what we do if we confirm we have found a signal, but I don't know what it is. I have a year before we start so there is time."
Bailes thinks the news would have a huge impact on people around the world.
"I suspect some people would go around with placards saying the world was about to end.
"We could be really lucky and find something coming from tens of light years away, but it is far more likely to come from thousands of light years away.
"Even if we discovered one tomorrow we'd all be long dead and buried before we could reply and the aliens would get an answer."