ET call Earth
Hoping for a reply from space
By BBC News Online's Science Editor Dr David Whitehouse
In a few weeks' time mankind will send out its first detailed radio message into the cosmos, asking any aliens who may receive it to get in touch.
It is part of a commercial project called Encounter 2001. This company based in Houston, USA, is offering the public the chance to send their own message into space for $30.
Not everyone thinks it is a good idea.
According the scientists involved in listening for intelligent signals from outer space, called Seti (Search for Extraterrestrial Intelligence), sending a message out into space is almost certainly a fruitless exercise.
Dr Frank Stootman of Seti Australia, says that it is not a message to aliens but to us. He adds that a reply is very unlikely and certainly not within our lifetime. And, if an answer does come, it will not be in English.
Before the individual messages are broadcast an encrypted signal, based on logic and maths, will be sent.
Dr Yvan Dutil, a scientist working for the Canadian Government, is helping to design the cosmic message. He points out that the only other signal deliberately sent into space in 1974 was aimed at a group of stars that were unlikely to have planets.
Because this signal is aimed at a handful of stars like our Sun he says that "for
practical purposes this will be our first detailed interstellar transmission."
The message will consist of a series of pages and will be repeated three times over a period of three hours. The signal will be 100,000 times stronger than a TV broadcast.
Don't listen, talk
Listening for radio signals from alien life in space is not new. There have been about 70 attempts over the past 40 years. So far no signals have been detected.
But transmitting a message into space has been tried only once.
In 1974, the Arecibo radio telescope sent a brief three-minute message towards the distant M13 stellar cluster.
It consisted of 1,679 pulses. When arranged into a matrix, they became an image showing atoms, molecules, our solar system and a representation of a human.
But the cosmic message being contemplated this time will be much longer, 400,000 bits.
Starting with basic symbols it will use logic to describe numbers and geometry. It then goes on to introduce concepts such as atoms, planets and even DNA.
It has been constructed to minimize the loss of information due to noise introduced into the signal during its interstellar journey.
"If any aliens ever intercept this message they will have mastered science so much of the first part of the message, the part that deals with numbers and atoms, will be familiar to them", says Dr Dutil.
"They can then go on and deduce a few things about humans such as where we live, how big we are and how many there are of us."
However, he does have some reservations about sending the message. "I'm not comfortable about sending something in space without a social debate."
Aimed at the stars
The message is aimed at stars from 51 to 71 light-years from Earth. They are all similar to our own Sun. They lie in a region of the sky called the Summer Triangle.
As well as the encrypted message there will be a series of greetings written by the general public. Anyone can sign up to send up to 30 words for $30.
According to Chan Tysor, things people have put on their cosmic message include their hopes for a more peaceful future for mankind and other races in space. One person said that we have made a mess of our planet so asked aliens to put off a visit for another 100,000 years.
Mr Tysor said that the signal was a kind of monument, "It is a kind of immortality knowing that something you wrote is beaming its way out of the solar system into the galaxy."
Many scientists do not think that broadcasting messages to the stars is a good idea. Among them are many members of the Setileague, a body that organises amateur searches for intelligent signals from space using small radio dishes.
"Great entertainment, but questionable science," said its executive director Dr H Paul Shuch.
It would be fun to beam personal greetings into space, Mr Shuch concedes, but like a message in a bottle, the prospects for successful contact are rather slim."
Carol Oliver of Seti Australia says that while she has reservations about the message being sent into space she hopes that it will inspire many to take an interest in Seti.
She adds that soon, because of a Seti Australia initiative, hundreds of thousands of Australian schoolchildren will be studying the search for life in space as part of a project to help them find out about the universe and themselves.
But Dr Dutil is worried that the Encounter 2001 message will set a precedent, "After us zillions of people will try to send a message into space."
Just imagine he says, "a weirdo group could send what they want into space and this may put humanity into trouble in the far future."