If there are other lives being led in the galaxy, how will we get to know about them?

Radio telescopes

Radio telescopes are instruments for detecting radio waves from the Universe. They usually consist of a parabolic metal bowl which collects and focuses radio waves at the focus of the parabola. Radio telescopes do tend to be much larger than their optical counterparts, as the wavelengths that they are detecting are much longer than the wavelength of light.

Unfortunately they also don't "see" as well for the size. To remedy this problem, they are often arranged in arrays. Radio astronomers study the radio waves emitted from the hot gases within stars and electrons that spiral within magnetic fields.

It all began in 1932 when Karl Jansky detected the first radio wave from the centre of our galaxy. Following the Second World War, astronomers began to map the spiral structure of the galaxy and to detect individual radio sources within our Galaxy and beyond.

It was decided to use radio astronomy for SETI as this is the most likely source of "intelligent" communication. Unfortunately, you cannot "hear" messages form the stars with headphones, as the astronomer in the film Contact attempted to do!

Alien Intelligence

How do we define what we mean by intelligence? And how do we communicate with a race or species that we have never seen, heard or probably even imagined? These are some of the problems that scientists working on the Search for Extraterrestrial Intelligence face.

It's possible that we have been unintentionally communicating with other civilisations since the invention of radio. Hundreds and thousands of radio and TV signals are pumped out of transmitters every single day and they don't just arrive at the receivers for which they were intended. What on earth must our little green friends think of us!

Any practical search for distant intelligent life must involve looking for evidence of distant technology. Searching for radio signals from these civilisations has long been considered the most promising approach to this project. The SETI Institute applies high quality research to the problem of looking for these civilisations and, more importantly, how it’s possible to know when they have been found.

How do you know if you've detected an intelligent, extraterrestrial signal? One of the ways is to look at the bandwidth - the range of radio frequencies that they take up. If it is less than a few Hertz it is probably produced artificially. Such narrow-band signals are what all SETI experiments look for. Other tell-tale characteristics include the existence of coded information on the signal.

Many have believed that they have detected signs of intelligent alien life before. In 1877 Italian astronomer Giovanni Schiaparelli was the first to see what we now know to be the optical illusions of dark channels stretching across the Martian landscape.

From his private observatory in Arizona Percival Lowell mapped more than 500 of these canals. Despite objections from other astronomers that they could see nothing, Lowell depicted, in books such as Mars as the Abode of Life, an advanced but dying Martian civilisation, combating the drying out of their world with global irrigation.

Is it Science?

Since the search for extraterrestrial intelligence began, there have been those that have argued that it is not truly scientific. That observation of phenomena that have never been seen is not the same as looking at a real effect and trying to decide how it came about.

But what is science anyway? It’s the systematic study of a subject through experimentation, observation and deduction, to produce reliable explanation of phenomena. One area of debate is whether the study of alien life forms of whose existence we have no proof, can really be a science. Can we predict anything about extraterrestrials?

One of the ways in which SETI has countered this charge is by using the Drake equation to show that it might be possible to predict something about the likelihood of other intelligent life being out there. SETI uses observations to sweep the heavens for signals in a systematic and scientific way, but how do they perform experiments?

The nearest that they come to experimentation is the sending of signals into outer space via radio transmitters and space craft.

In 1978, the American government decided to remove much of the financial backing that it had given to SETI and the project nearly floundered for a while. The well known American astronomer, Carl Sagan, helped to give SETI back some of its funding through a series of television debates and petitions. Then, about four years ago, NASA had its funding removed. However, SETI is still flourishing.

The debate over whether SETI is science will carry on. But one thing is certain, if they do detect a signal from the stars, scientists will be the first on the scene.

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