Arecibo Radio Telescope, Puerto Rico, used in SETI Experiments
It's always nice to know of things marginally older than oneself.... and in this case its the Search for Extraterrestrial Intelligence (SETI). It is 50 years since the great Dr Frank Drake did the first SETI experiment of the modern era at the National Radio Astronomy Observatory at Greenbank, West Virginia launching science's attempt to ascertain whether, assuming homo sapiens can be defined as 'intelligent', there is any other such intelligent life in the Cosmos.
Frank, who is currently involved in "The Carl Sagan Center for the Study of life in the universe" at the SETI Institute in California, defined the famous Drake Equation, in an attempt to at least approximate the number of intelligent civilisations in the Milky Way galaxy:
N = the number of civilizations in our galaxy with which communication might be possible;
R* = the average rate of star formation per year in our galaxy
fp = the fraction of those stars that have planets
ne = the average number of planets that can potentially support life per star that has planets
fℓ = the fraction of the above that actually go on to develop life at some point
fi = the fraction of the above that actually go on to develop intelligent life
fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
L = the length of time such civilizations release detectable signals into space.
Over the years some of the terms have been refined... we know the rate of star formation in the Milky Way each year (equivalent to three solar masses)... we're starting to get a handle on the number of stars with planets (at least 10-15%).... perhaps even Earth mass planets in the habitable zones of stars. The rest of the terms we don't know... we still only know of one genesis of life here on Earth, and hence can only make educated guesses for the remaining terms. It's staggering to think though that the Earth is 4,500,000,000 million (4.5 billion) years old, and yet we have only possessed radio technology for a century (0.000006% of the Earth's age!)
It's really a case of quantifying and plugging in either your optimism or pessimism to get N to equal any number from one to, in the case of Carl Sagan, a million. Many scientists are of the opinion that life may be common in the Cosmos, but intellegent life may be comparatively rare. Perhaps, like us, it is the norm that intelligent life develops the atom bomb at the same time as radio astronomy. Perhaps its passions and beliefs cannot co-exist with its technologies, and intelligent aliens self destructs soon after they develop nuclear fission.
Over the last 50 years there have been some enigmatic alerts from the SETI programmes, most famous of which has been the 'wow' signal, detected by the Ohio Stae University team in 1977. Goose bumps they may cause, but without independent acquisition and verification of the signals, they're not worth the pixels on the computer screens.
SETI goes from strength to strength, and since NASA funding was withdrawn by the US Congress in 1992 (apparently politicians aren't interested in the greatest question of all), the SETI Institute has gained private funds, even from Microsoft co-founder, Paul Allen who is helping to fund the Allen Telescope Array, 290 kilometres north east of San Francisco. Where once a couple of channels could be analysed in Project Osma... millions and then billions of channels will be checked simultaneously. Why restrict yourself to the frequency of the emission of neutral hydrogen... we certainly transmit narrow band signals all over the spectrum? And then of course there's Optical SETI.... does ET use laser communications. Whether it's the ATA or Arecibo, you can even take part in SETI@Home.... let your computer analyse radio telescope data in this UC Berkeley distributive computing programme.
And what do I think? I'm 100% behind SETI - it costs so little and either way the answer will be profound. It's the greatest question of all: are we alone? Of course, there are some people who think we've already been visited and the aliens are already amongst us. But without any evidence, not one thruster or spacesuit or alien burger carton, I'll stick with famous scientists past and present such as Frank Drake, Gill Tarter, Seth Shostak and Carl Sagan who take the difficult route... and endeavour to answer this greatest of questions scientifically.