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Messages...but not from SETI

For around half a century we've been announcing our presence to the cosmos. Radio, television and radar all 'leak' into space. It's an awful thought, but instead of some carefully worded message constructed by United Nations on behalf of all humanity, any extraterrestrial intelligence may be judging us by episodes of "I Love Lucy".

SETI doesn't send messages for some very good reasons, not least of which is the huge time lapse in getting any result. An interstellar call to even our closest star system travelling at the speed of light, 300,000 km per second, would take 4.3 years to get there, and 4.3 years for the reply to be heard..."excuse me,

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The message from Arecibo

can you say that again?"...not a snappy telephone conversation (and not in perfect English, no matter how hard Star Trek tries to convince us it would be that easy). The chances are our nearest cosmic neighbours might be hundreds of light years away, taking four or more human lifetimes for any chance of success.

Deliberate message sending needs to be done over generations unlike the one sent from the world's largest radio telescope at Arecibo in Puerto Rico, by Dr Frank Drake in 1974. The chances of any message being picked up from a one-off transmission are vanishingly small. But Drake had good reason to signal the stars in this way - it was a celebration of  the upgrade of the telescope rather than any serious effort to make contact with ET.

It was a hot tropical afternoon and 250 dignatories had gathered at the telescope to celebrate the three years of hard work that would allow the 1,000 foot giant to peer further into the universe.

Drake, now President of the SETI Institute in California, had devised a message with the help of some postgraduate students. Over 169 seconds it sang a song of Earth to the stars with a power than outshone the sun on its particular frequency. "That ought to get someone's attention, I thought", said Drake later in his book "Is Anyone Out There?"

For dramatic effect, the sound of the message was broadcast to the assembled audience while it was being transmitted. Drake wrote: "The two pitched tones of the message filled the air, like the trilling of a strange musical theme played on a giant electronic synthesizer. The song, unique and full of yearning, affected us strongly.

"...I saw women in sleeveless dresses rub chills from their arms. I saw the eyes of sober scientists filled with tears. And mine did too."

The message is simple. Reading from the top it gives the numbers one to ten, describes the biochemistry of life (green), the complexity of DNA (blue and buff), a human (red) with the height to one side and the population of Earth to the other, the sun and nine planets (in yellow) shows one planet raised beneath the human's feet to indicate that is the inhabited planet and below that information about the Arecibo telescope where the message orginated. It was transmitted as a string of zeros and ones (binary) and aimed at the Hercules cluster of suns some 25,000 light years away. If anyone is out there we'll know...in 50,000 years.

There have been some other attempts to announce our presence to the universe, but it'll be several hundred thousand years before any of the four spacecraft reach a star system. In

naked sketch.bmp (429878 bytes) 1972 Pioneers 10 and 11 were launched and each carried a copy of the plaque shown left. NASA apparently received many complaints about sending 'pornography' into to space. More seriously comment has been made on the man's upraised arm since several interpretations could be made, with a friendly greeting being only one of them. Also the woman is standing in a subservient way to the man - politically incorrect today. The
spidery diagram to the left of the figures is a map using the distance of known pulsars so that an alien technology could work out where our sun is among the 500 billion suns in our galaxy. As a matter of interest, Pioneer 10 is still transmitting back to Earth - but with just the power of a Christmas tree light over 10 billion kilometres. Nevertheless SETI equipment can pick up that signal and in fact the SETI Institute's Project Phoenix does that as a matter of course as a calibration of their equipment.
Voyager 1 and 2 carry a recording of the sights and sounds of Earth attached to the outside of the spacecraft under a protective cover (right). Notice the same spidery diagram - the same interstellar map as depicted in the Pioneer plaque. The Voyagers left in 1977 and Voyager 2, now at 10.9 billion kilometres is now further away than any other man-made object. However, in 20 years of travelling at almost 17 km per voyager record.bmp (425222 bytes)
second it is still only eight light hours away - compared to 4.3 light YEARS to the nearest star system to the sun. It demonstrates very nicely how vast even our local cosmic neighbourhood is, and why SETI scientists believe that there is only one way we might encounter intelligence elsewhere in the cosmos - and that is on an electromagntic wave travelling at 300,000 km per second.

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