SETI. Wow! What a big ear you have.

Or used to have, we should say, because the Big Ear radio telescope is no longer. However, on 15 August, 1977, it received and recorded what became known as the 'Wow!' signal - a signal that remains both an enigma and the most credible candidate for an actual transmission from extra-terrestrial intelligence. It should be noted that on the very next day Elvis left the planet having earlier said: 'This is gonna be my best tour ever.' Elvis remains an enigma too, but perhaps for different reasons.

Some Background

Searching for life, but not as we know it, presents the same problem for us as for the drunk who has lost his keys late at night. He is found looking for them under the street lamp because, of course, he wouldn't be able to see them anywhere else. So it is with the Search for Extra Terrestrial Intelligence that some choices have to be made. What to search for is the first one of those choices. In this case, the search is for radio signals that are both incoming and intentional.

The Waterhole

Early on, interest focused on the region of the radio spectrum between 21cm (the wavelength of the radio signal emitted by the hydrogen atom) and 18cm (that emitted by the OH molecule, also known as the hydroxyl radical). In this configuration, the two don't actually combine to form water, but for aesthetic reasons the region has been called 'the waterhole'. Given that we have to start somewhere, a waterhole seems a logical place to look for life.

It is a practical place to look, too. Due to the importance of the hydrogen line band to radio astronomy (21.4cm-21.0cm), for example, no licences are given for its use - so presumably signals received in this range should only originate from the sky. While at Harvard in 1955, renowned radio astronomer Frank Drake was measuring the radio spectrum of the Pleiades cluster in Taurus when he found a strong signal in this band that seemed entirely too regular. His initial thought was that it must be intelligent and the shock of it started turning his hair prematurely white. To his disappointment, however, the signal persisted as he turned the telescope from the Pleiades which indicated that it did not in fact emanate from the sky after all. Alas, his hair colour continued to fade, but it was an event that nonetheless galvanised his resolve to continue the search. Many radio astronomers have since joined him at the waterhole.

The Big Ear

The idea for the Big Ear radio telescope was conceived by the late Dr John D Kraus and appeared in the March, 1955 issue of Scientific American. Construction began on the grounds of the Ohio Wesleyan University in autumn, 1956 and reached completion in 1963.

The Big Ear actually was big. Incoming radio signals were bounced off a 340-feet-long by 100-feet-high flat rectangular tiltable reflector over to a 360-feet-long by 70-feet-high curved reflector shaped as a paraboloid that focused the incoming radio beam. These reflectors were separated by a 360-feet-wide by 500-feet-long ground plane (picture an aluminium carpet). In all, the Big Ear covered a somewhat greater area than eight Olympic-sized swimming pools would.

Just as our ears are attached to our head and can only passively scan a party for interesting conversations when we turn our head, so the Big Ear was affixed to the Earth and scanned the sky due to the Earth's rotation. The tiltable reflector did, however, allow it to also 'look' higher or lower in the sky. The focused beam was directed to two horns. Consequently, just as words from the mouth of a particular party-goer would first reach our left ear, say, and then our right as we turned round, so a radio signal from a patch of sky would first enter one horn and then the other. This is actually pretty important because it is then possible to discern interesting signals that originate from a point ('What's your sign?') from those that are just part of the general hubbub ('Chugalug! Chugalug! Chugalug!') since general hubbub pretty much reaches both ears at once.

The Big Ear fell victim to funding cuts followed by unsympathetic developers who dismantled it in 1998 to extend a golf course, which was perhaps the unkindest cut of all. Still, its place in history was assured by the arrival of the 'Wow!' signal.

Wow! Then

The Wow! signal is so-called because that is what its discoverer, Dr Jerry R Ehman, wrote on the computer printout that immortalised it. Here is what happened:

1. The Big Ear was tuned to the waterhole at about 1420MHz (21.1cm).

2. The signal arrived at about 11.16pm Eastern Daylight Savings Time on 15 August, 1977, and was dutifully logged with the characters '6EQUJ5'.

3. A few days later, Ehman laid astonished eyes on this string of characters while reviewing the pages of printout and made this annotation in red ink.

4. Wow!

There's plenty of fiddly technical bits that occupied the computer before it printed out each character, but very basically, each character represents the ratio of the intensity of a signal versus the level of background noise (hubbub). A particular channel (there were 50 in total) is observed over a 10 second interval and if there is no signal, the printout shows a blank. If the signal is the same as the noise, a 1 is printed. If it is twice the noise, a 2 is printed and so on up to 9. Then 10 is represented by 'A', 11 by 'B' and so on up to 'Z'. Thus levels from 0 up to 35 times the background noise are logged. So, the string '6EQUJ5' translates to levels of 6, 15, 27, 31, 20, and five times the background noise measured 12 seconds apart (ten seconds being spent observing and an additional two seconds needed to perform calculations each time).

What this indicates is that a narrow incoming beam first glanced the Big Ear registering six times the background noise, and quickly increased to 31 times as it faced the antenna square-on. This is just what one would expect from a point source, and a source of unprecedented strength and clarity at that. The problem was that, since there were two horns, this string should have repeated after about two minutes as the second horn swung round, so to speak - but that never happened.

Imagine hearing O Sole Miiiiioooooo, then turning your head round only to hear nothing more. If you were never to hear it again then some equally likely reasons could be that: firstly, the galactic Pavarotti was singing himself hoarse for quite some time and gave up just when you finally heard him; that it was a one-time outburst that you just happened to catch; thirdly, that it is a refrain but you were only briefly in sync; or, finally, like a rotating beam from a lighthouse, a megaphone was pointed your way for a moment and now it isn't. The conundrum can really only be resolved if the signal is heard again. For the next 30 days the antenna was kept in the same configuration, but without results. A few years later the same strip of sky was scanned, also without results. There have been subsequent searches for periodic signals emanating from the Wow! locale by others, but again without success. Alas, it appears that we are faced with something akin to the 'Rendezvous Problem'.

Wow! Now what?

So, what to do? Give up? Not on your life. First of all, now that the Big Ear is no more, a number of 'mainstream' antennas have spent at least some of their time in the search, including the Very Large Array near Socorro, New Mexico, USA. Even though 30 years of listening has not necessarily produced a more credible candidate than the Wow! signal, it would be incorrect to assume then that not much has been happening. Computers have improved tremendously, for one thing. Whereas it took two full seconds for the Big Ear's computer to analyse ten seconds of data on 50 channels within a narrow band, we are approaching the point where we can sample and analyse the full radio spectrum in real-time. How? Get everyone involved all over the world! The advent of the Internet has made this possible. A look at what has happened up to now is enough to make anyone say 'Wow!'

In 1999, the SETI team at Berkeley launched SETI@home Classic and provided specialised software for people all over the globe to download onto their personal computers. They also then began truncating streams of radio data into packets and made these available to everyone. Computers the world round 'crunched' these units, effectively creating the world's largest supercomputer. Once completed, these units were sent back to Berkeley via logging onto their servers. The people who joined up were united by one cause: the small but captivating possibility that their computer might be the one to first detect a confirmed message transmitted from an alien civilisation. Dedicated fans bombarded the Berkeley website with graphics for desktop wallpaper and even song lyrics. Teams were set up, like the h2g2 Researchers, but individuals could crunch merrily away alone, grouped only by their 'country' statistics. Scientists at McMurdo Station, Antarctica signed up, thus making every continent on the planet represented by at least one team. SETI@home Classic was indeed the first project the human race committed to as one people, regardless of race, skin colour or creed. The beauty of it was, everyone had the same chance of winning the prize - a global lottery with the winner guaranteed their place in history.

The Classic was discontinued on 15 December, 2005 having been upgraded to the SETI@home/BOINC (Berkeley Open Infrastructure for Network Computing). It took about a year to convert all the participants to the new programme. BOINC is quite diverse, there are many programmes you can join, such as climate prediction (global warming), Einstein@home and Rosetta@home, and you can choose to run the programme split between projects if you wish. Many classic SETI@home users were reluctant to shift to the beta version as they lost the beloved screen-saver. Then there were the teething problems with the new software to contend with, and the many outrages as Berkeley's servers struggled to cope with the demand. Now there is a scheduled shutdown once a week for regular maintenance. Project participants can make a profile for public display, allowing themselves to be trumpeted as 'Seti User of the Day' on the main website. Other goodies are certificates of computation, which you can print off in a variety of styles and display on your bedroom wall; and message boards so you can chat to other users.

In November 2006, in order to satisfy those feeling compelled to understand the fiddly technical bits, Dr Eric Korpela was interviewed by Graeme Knight (a Post Graduate Astronomy student with Swinburne University, Victoria, Australia). In the interview Eric explains how SETI@home works, how the data is processed, dechirping data and the possibilities of finding voluble ETI.

Among noted fans of SETI@home is Sir Patrick Moore. Although not a cruncher himself, as he doesn't own a computer, he has promoted the project on his monthly The Sky at Night TV programme. Other subjects he has covered since 1957 are: The Drake Equation, Extrasolar Planet Hunting, The Valkyrie Spacecraft, Travelling to the Stars and Obstacles to Manned Space Exploration: Propulsion. Since the Space Age began in 1957 with the launch of Sputnik 1, technology has advanced in leaps and bounds, and new discoveries, such as the astonishing fact that whale oil doesn't freeze in outer space, are being made all the time. Should we eventually make contact with an alien civilisation, while we may not know what to say, we at least know which lubricant to stock up on for the oil changes for our first visit, so that's a step in the right direction.