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IT SITS in your ear, grazing on energy from your brainwaves and, astonishingly, lets you understand anything said to you in any language – terrestrial or otherwise. The Babel fish is the ultimate translator, perfect for conversing with aliens from this or any other galaxy. Unfortunately, though, it exists only in fiction, an essential alien in Douglas Adams’s Hitchhiker’s Guide to the Galaxy.

In real life, communicating with alien civilisations – if indeed there are any – is likely to be more tricky. Where do you start when you have no language or culture in common? The answer could come from a civilisation closer to home: Canada.

Yvan Dutil, an analyst at the Defence Research Establishment Valcartier, near the city of Quebec, has created a message that he hopes can be decoded and understood by aliens with no knowledge of humans. While cryptographers try to hide information within a message, Dutil is an “anti-cryptographer”. “We do exactly the opposite of what a cryptographer would do,” he says. He wants the information in his message to be readable to any intelligent being.

Backed by an American firm, Encounter 2001, Dutil’s four-hour message was transmitted by a powerful Russian radio-telescope on 24 May. By now it is far, far beyond the orbit of Pluto, heading out towards Vega and the star fields beyond.

The radio signal shifts back and forth between two frequencies 48 kilohertz apart. One frequency represents an “off” and the other represents an “on”. When reconstructed in the proper way, the ons and offs draw symbols and pictures.

During its odyssey, it’s likely that this interstellar fax will be weakened and distorted by static, so any aliens at the other end will have a hard time making out the information. The secret to minimising this problem is redundancy. T- pr-v- th-t -ngl-sh -s r-d-nd-nt, j-st r-d th-s s-nt-nc-. Even though there is a lot of missing information, you can still understand the message. This is the essence of redundancy – you can make good guesses about the content of a message even if bits of it are missing.

Dutil’s message has plenty of redundancy because it contains patterns that repeat over and over. For instance, around each “page” of the message, he draws a box. If bits from the message are lost, the box gets distorted. By realigning the sides of the box to match the boxes around other pages, the aliens would automatically correct for the lost bit.

There is redundancy, too, in the symbols that form the meat of the message. Each is a picture 7 bits high and 5 bits wide, and represents a single concept. Some are numbers, while others stand for objects or abstract ideas such as “temperature”. They are picked to be easily distinguishable, and each differs from every other character by at least 7 bits. “Basic signal correction theory tells you that with seven bits difference, you will be able to correct an error of three bits,” says Dutil. Put another way, even if almost a tenth of the message is lost, it should still be possible to reconstruct the whole thing.

Being able to correct errors is worthless, however, if the aliens can’t figure out the pages and what is on them. The regular shape of the boxes on the pages will give the signal a periodic quality: the aliens should see that some patterns are repeated over and over at regular intervals. Picking out such patterns is something humans are good at doing, and Dutil hopes that aliens will spot them too. Some form of sight is another prerequisite for the recipients. But then, just to pick up the message they would have had to build a radio telescope. “It is difficult to imagine how they could do so if they are not able to `see’ in one way or another,” he says.

Assuming that they see the pages with their symbols and diagrams, the aliens still do not know our language. Dutil’s answer is to teach it to them within the body of the message – the message must decipher itself. In the good old days of cryptography before the advent of computer codes, one of the dumbest things to do when sending an encrypted message was to have a predictable beginning. During the Second World War, Allied intelligence cracked the Enigma code in part thanks to the Nazis’ habit of starting messages with the same few characters.

For anti-encryption, then, the beginning of a message should be very predictable. “In the beginning, we shall communicate facts which may be supposed to be known to the receiver,” wrote Hans Freudenthal, a mathematics professor at the University of Utrecht, in 1960. He was describing his universal language, lingua cosmica or Lincos. Lincos isn’t a spoken language, more a mishmash of mathematical symbols. It attempts to remove all the assumptions behind maths and language, and builds them up from scratch. Every symbol must be defined by symbols that come before it. And, because of this, the very first symbols used must be concepts that need no definition. They must be universal in the true sense of the word.

But what knowledge is universal to any advanced civilisation? To Freudenthal it was obvious: mathematics. Civilisations throughout history all learnt to count before they invented written language. The Incas, for example, never set stylus to clay or pen to papyrus, but used a system of knots in strings. Civilisation after civilisation discovered the same numerical properties, derived the same theorems and used the same mathematical tools. Numbers are the closest thing humans have to a cultural universal.

So, in his message, which is based on Lincos, Dutil starts by showing the aliens that he can count. Zero, one, two, three – not much here to surprise an extraterrestrial – four, five, six . . . Dutil transmits each number in three ways – as a series of dots, as a binary number and as a strange looking numeral – hoping that the three representations will reinforce each other and allow him to use them interchangeably. The symbol for an equals sign is also introduced here (see Diagram).FIG-22044901.jpg

Next up are prime numbers: two, three, five, seven, eleven and so on. If the aliens have even a primitive mathematical system, they should know this sequence. Better yet, the sequence of numbers is irregular, not the sort of thing that would come from a natural source such as a pulsar. It’s a sure sign of maths geeks: a form of intelligent life.

From the first page, the aliens should understand how we represent numbers. The second page teaches them how we add up: 1 + 1 = 2, 2 + 2 = 4 and so on. This gives them an idea of the notation we use. This is followed by subtraction, multiplication, division and exponentiation. The section ends with pi and the Pythagorean theorem. “Pi and the Pythagorean theorem are among the oldest mathematical objects created by humans,” he says. “So we estimate they will be easy to understand for an advanced civilisation.”

From maths, the message moves to chemistry and physics. Here, too, there are universals. The speed of light, for example, should be recognisable to an advanced civilisation. But what about units? Should it be 3 x 10⁸ metres a second, a foot per nanosecond or 1.8 x 10¹² furlongs per fortnight? To talk to aliens about physics and chemistry, we must first tell them what our units are. But our units are arbitrary, so how do you tell them what a metre is without sending a metre rule?

For time and distance, Dutil uses the hydrogen spectrum. When excited, hydrogen, like other atoms, only emits light of certain wavelengths. These wavelengths appear as bars of light in the electromagnetic spectrum, which identify the emitting element as surely as fingerprints identify a burglar. Dutil describes the spectrum by giving the wavelength and frequency of several of these bars, in metres and hertz (inverted seconds). If extraterrestrials recognise the hydrogen spectrum, they should be able to figure out what a metre is and what a second is.

For mass and charge, Dutil draws a picture of the components of a hydrogen atom and a helium atom, and gives the relative weights and charges of the protons, neutrons and electrons (see diagram). Then Dutil gives the mass of the proton, neutron and electron in grams, from which the aliens could figure out our unit of mass. Temperature is given by describing the melting and boiling points of water and various elements at atmospheric pressure. This not only gives the extraterrestrials the concept of kelvins, it also reveals the unit of pressure: pascals.FIG-22044902.jpg

If the aliens have deciphered the message thus far, they won’t have learnt anything new about the galaxy – except that someone is trying to communicate with them. This is where they begin to learn. Using the information imparted so far, Dutil gives the mass of the Sun and planets in our Solar System, the lengths of their years and radii of their orbits. He describes the Earth: the land, sea and air, and gives the height of Mount Everest and the depth of the Marianas Trench. He gives the height of human beings, the colours they see and the sounds they hear. Next comes DNA and a schematic representation of how it works in the cell, a description of the radiotelescope’s properties and some cosmological musings. Finally, Dutil requests equivalent information from the aliens.

No guarantees

The message is a fun idea, but would an alien understand it? “There are numerous ways of failing but not that many of succeeding,” admits Dutil. “There are absolutely no guarantees it will work.” Part of the problem is that the diagrams of the hydrogen spectrum, human beings – and even the symbols – are representations. This means that the aliens will have to decipher what those representations mean. A series of stripes may look like the hydrogen spectrum to a human, but will it mean anything to an extraterrestrial?

“So much interpretation goes into reading a picture,” sighs Douglas Vakoch, a psychologist at the SETI Institute in Mountain View, California, and an expert on the problems of communicating with alien civilisations. “If you look at how human beings represent themselves, in New Guinea you might see spiralling shapes that look like abstract art, but if you’re trained to think in those terms, the spirals look like a trunk and arms.” There’s no guarantee that an alien would figure out what a human looks like even if it intercepted an engraving of one, much less received a radio signal that has images encoded deep within it.

Vakoch believes that there might be a better way of getting a message across. “You can encode the concept more directly. For instance, to represent the hydrogen atom, you can transmit at the frequencies that correspond to its emission spectrum,” he says. Vakoch suggests that combining this method with Dutil’s pictures would probably be more understandable than either alone. “I’m an advocate of redundancy,” he says.

But there’s something else that worries Vakoch. He suspects that it is premature to send a message into outer space. “I’d say, let’s hold off for twenty, thirty, forty years, and decide whether we do want to transmit a message at all.” Dutil, too, has concerns about transmitting messages willy-nilly into space. Encounter 2001 now offers to send personal messages into deep space for only $14.95. “Since I have been involved in this project, I have become aware of other groups wanting to do the same thing: publicity companies, ham radio operators, et cetera,” says Dutil. “This issue has the potential to become a serious problem very soon.”

After all, even a tolerant civilisation might try to silence a noisy neighbour. And there’s no guarantee that all alien civilisations will be friendly. So removing the barriers to communication between life forms might not be such a good idea. Douglas Adams blames one troublesome object for “more and bloodier wars than anything else in the history of creation”. That object is the Babel fish.

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Talking to aliens

Earthlings have sent messages to the stars before. The Pioneer 10 and 11 spacecraft, launched in 1972 and 1973, carried metal plaques engraved with pictures. These pictures identified the position of our planet and contained other information, such as two figures intended to represent human beings. The two Voyager spacecraft, launched in 1977, also carried engravings that showed mainly how to listen to a long-playing record (a technology that already seems quaint) stowed on each craft, which bore music, images and sounds.

Despite these gestures, scientists never had any illusions about whether the spacecraft would be intercepted and the messages deciphered. The sheer distance between stars makes it extremely unlikely that the spacecraft will be seen, even by aliens looking out for a message. “It would be a most miraculous chance event if one were intercepted,” says Douglas Vakoch of the SETI Institute.

Serious attempts to communicate with aliens must use light or radio signal. Travelling at 300 000 kilometres a second, a message can reach nearby stars in years rather than millennia. In 1974, astronomer Frank Drake sent a message to celebrate the reopening of the Arecibo radio telescope in Puerto Rico. He used a language similar to Lincos, but because the message was only a few minutes long, he had time only to display our knowledge of prime numbers, represent the structure of DNA and draw a comical picture of a pot-bellied, small-headed human.