What Are We Looking For?
Since SETI first became a subject for serious scientific research, scientists have come up with many possible ways to detect the presence of other civilizations by searching our part of the Galaxy for signs of artificially created signals. Using many different kinds of detection equipment and novel concepts, investigators laboured away in their electronics laboratories and observatories dreaming, that one day, the signs they had been searching for would be found.
It was once thought that the planet Mars was inhabited by a race of beings that had constructed canals all over the surface to channel water from the poles to the more arid equatorial regions. Telescopic observations proved this fact and the early nineteenth century was awash with tales of the Martians achievements and great technological feats of civil engineering. The planet Mars was so close and these beings were so intelligent that they must also have telescopes to view other worlds and maybe they were trying to contact us. How should we search for these possible signals? Radio was in its infancy and was not even a candidate at this time of the early 20 th Century. Surely these "Martians" could look at the night side of the Earth and see the lights of our cities shining brightly? .
Although some radio enthusiast announced that they had received signals that were thought to be coming from mars, these claims were later found to be false. Marconi, an early radio engineer who is credited with many first's in the field of radio communication left behind notes that indicated that he had heard strange signals on his very
primitive radio receivers. He thought that they were coming from space, from other civilizations, E.T.! What a time that must have been, no radio frequency interference, no Satellites, no other radio stations at all to drown out those weak signals from space. Will these radio quiet times ever return, what a thought!.
Warning The Mars MPEG File to right is a large file and may take some time to download
Even all those years ago, several SETI projects were suggested and plans were even drawn up for a huge circle and other geometric designs to be created by digging gigantic trenches in the dessert regions close to the Earth's equator. These trenches were to be filled with kerosene or oil and set ablaze at night. This dazzling spectacle seen from
Mars at night, it was thought, would be an indication that the Earth was populated by intelligent beings and that the
Martian's would surely send us a
signal as a return message. Others thought that carving out huge geometrical shapes in the forests of Siberia that contrasted with the snow cover in winter would attract the attention of the
Martian's and prompt them to reply.
Funding for these projects was not forth coming, as is usually the case for SETI research. However
Saddam Hussein did manage to get the fires in the desert going, but to our knowledge, no message from space was ever received in response to his actions apart from some cruise missiles that were sent by the U.S.A.
The prospect of
signalling another civilization is not such a daunting task when one thinks of it in terms of our solar system distances. However, when you multiply the distances out to a cosmic scale the problems really become overwhelming. Take for instance the time it takes a radio signal to reach our nearest stellar neighbour located in the
Alpha-Centauri system, which is 4.3 light years away. As radio signals travel at the speed of light it would take 4.3 years just for the signals to reach their destination. Multiply that by two for a reply to come back and that's 8.6 years for a signal to get there and for us to get an answer. This is a massive problem to overcome as the distances between the stars is so large, that the signal could have been travelling to us for hundreds or even thousands of years before we detected it. This makes it practically impossible for us to establish a two-way dialog with another civilization unless the distance between us is very short indeed, say out to a distance of 10-20 light years. Luckily there are many solar type stars in our region of the Galaxy, so it seems possible that we maybe lucky enough to detect the presence of a nearby Technological Civilization and be able to establish a two-way communication, of sorts, with them.
But who says that we should look at "Solar Type" stars?. We have no idea about the sort of planetary system that could evolve a life form that we could communicate with. We only know about one place in the whole universe where life exists for sure. Good old planet Earth. This is why the race is on to find Earth like planets orbiting nearby stars.
So what type of Solar System are we looking for? We don't know for sure so we will target stars that are close enough for the signals to get here before they are to weak.
Out to about 250 light years is our guess. We could possibly image a planet out to this distance using new telescopes that are just coming on line now like the
Keck Interferometer and the E.S.O's V.L.T. array.
The fastest means of communications we have yet developed uses both laser and radio transmissions. Both systems travel at the speed of light and can transfer large amounts of information to the recipient of the message. Radio has been used here on earth for most of this century and
powerful transmitters have been used by radio and television stations now, for about 60 years.
Powerful Radar transmitters were developed and used during the Second World War to track aircraft and shipping. They need ed to use powerful transmitters as the receivers of the time were not very efficient.
This means that another technological civilization out to about 60 light years from the earth, could have already detected us and sent a reply. Our signals would be buried in the cosmic static, so E.T. would need very advanced equipment to detect our radio pollution. Only our most powerful transmitters would be heard. The most powerful transmitters we have could be at detectable at interstellar distances out to about 200 light years depending upon the size of the transmitting antenna and it's beam width. An Arecibo size antenna transmitting a
million watt radio signal, could be detected out to about
10,000 light years from it's source, the Earth. That means that there are probably billions of planets that could be reached with this sort of powerful transmitter. Alas, we are not actively transmitting a signal for our Galactic neighbours to hear, we prefer to listen instead. (reminds me of a theme from a Peter Sellers movie)
The laser was first developed and used in the laboratory during the late 1950's using a rod of
natural ruby crystal. These crude pulsed lasers were mainly laboratory curios and at that time scientist's wondered what they could be used for other than melting holes in metals and making art on pieces of wood!!!.
During the past 42 years lasers have come to dominate us in many ways that we probably don't realize. Nearly every home computer and audio system uses lasers to load computer programs and play music.
Fibre optics send billions of telephone conversations all around the world every second. Dazzling laser beams are used to transmit the messages along glass fibres thinner than a human hair and soon lasers will be used to create a new generation of computers that will use laser beams to transfer information within the chips. This will give us a tremendous increase in computer power and speed.
State of the art, 3 dimensional memory blocks based on holographic principles will be used to create enormous amounts of memory storage that will make the 100 gigabyte hard drive as small as a floppy. These advances will further increase the capabilities of our computers. All of these developments would not have been possible without the development of laser technology.
In the future, spacecraft may use laser based communication systems to keep in contact with the earth. These light beams will carry thousands of times more data than current radio system used today and who knows, maybe one of these beams of light may be intercepted by accident at a
nearby solar system by another civilization who may have also developed laser communication systems. What a surprise they will get when they make their first detection of an
There are lots of
natural radio sources for Radio Astronomers to detect and study using their giant antennas. Using optical telescopes fitted with special detectors we expect to find interesting natural phenomena that may not yet have been observed, maybe even an E.T. laser signal will trip our photon counter and signal the first ever detection of a
non-natural photon of laser energy?
Traditional Astronomical observing techniques tend to use
long integration times when viewing objects across the depths of space. This allows the recording equipment (cameras, Photographic Plates, CCD's etc) to collect as many photons as possible so as to produce high contrast images. These techniques tend to "smear" out any transient signals that may contain other forms of information. Should a laser beam from an alien transmitter be captured it would probably look like a dim background star that probably wouldn't get much attention. On the other hand should this same source be detected by a high speed photon counter array we would immediately become interested as the information contained in this source would be noticed and analysed.
Our Celestron C-14 optical telescope will be looking for such an event. Connected to the telescope will be a very sensitive detector array that will scan the light entering the telescopes optics for signs of something abnormal in the photons being received. We should have the telescope building completed soon and start our observing runs towards the end of 2002.
More to come later, so keep tuned in.