Thursday, March 17, 2005

How To Talk To Aliens

By Dr. John Nunn


There are currently various efforts going on around the world to receive signals from alien intelligences. These go by the general name of SETI (Search for Extraterrestrial Intelligence). The basic idea is that sensitive radio telescopes are pointed at likely sources and record any radio signals they receive. These signals are then analysed to see if there is any indication that they might be artificially generated.

Unfortunately, there are many natural sources of radio waves in space, so it may be hard to pick out a message from the background noise. One of the main problems in SETI is the amount of computing power required to analyse the vast amount of data recorded by the radio telescopes. One ingenious solution is the SETI@home project. This involves installing a small program which runs in the background on your computer. When your computer has some idle time, it downloads some data from the Internet and starts analysing it, uploading the results when it has finished. By distributing the work amongst many computers (over five million people have joined the SETI@home project) everything proceeds a lot faster.

Let’s suppose we do at some stage detect a clearly artificial alien signal. I am sure there would be a huge debate about whether or not to respond, but assuming that we did reply, the possibility of striking up an interstellar conversation arises. What kind of messages would be sent? Without any common language or background, how could we send messages that aliens would understand?

These subjects have been discussed at great length and the favoured scenario is to send pictures based on a rectangular array of dots where, for example, a ‘1’ means a dot and a ‘0’ represents no dot. Then we would send a signal which repeats, for example, every 10609 dots; the aliens should realise that as 10609 can only be factored in one way (it is the square of the prime number 103) the idea is that the dots should be arranged in a square array, forming a picture. By sending a series of pictures, eventually some sort of vocabulary could be built up and allow a significant exchange of information to take place.

I suspect that this method involves a lot more anthropocentrism than one might expect. Of course, one would ‘naturally’ send the dots from left to right and top to bottom. Why? Because that’s the way we write. But wait a moment ... not all human languages are read from left to right and top to bottom, so even amongst different human peoples it would be easy to get the picture reflected or upside down. With aliens the problems are going to be immeasurably worse. They might not see in pictures at all, or they may think in vector graphics rather than bitmap graphics, and so on.

Another important point is the motivation behind communicating in the first place. Why have the aliens sent us a signal? The assumption usually seems to be that an alien civilisation would ‘naturally’ send us lots of information about their science, technology and culture. However, this seems to me an unrealistic expectation.

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