Writing Messages To Aliens

contributed by Michael Busch

The goal of SETI is to search for intelligence elsewhere in the universe.  METI is concerned with how to communicate with whoever may be out there.

Since it is impossible to send a message faster than the speed of light, METI messages must be self-contained.  It may be a thousand or ten thousand years before any message that we send out is received.  Unless the aliens are very patient and we are still here two or twenty thousand years from now to answer any questions that they have, the message is strictly one way.  You should think of METI messages as being like time capsules, rather than like telephone calls.

We are trying to say something to someone we have never met, and most likely never will meet.  We have no idea how they think or what they look like.  How can we make sure that we will be understood?

All language is based on pattern recognition.  You are reading this by recognizing the patterns of characters on your computer screen as words, and those words as corresponding to concepts that you already know about.  To talk to ET, we need a starting point of patterns and concepts that they will recognize, to establish a common vocabulary.

Fortunately, there will be such a starting point.  Regardless of how the aliens perceive the world, of how they think, and of how they live, if they can receive any messages that we send out, they must know a certain amount of astronomy, physics, and mathematics.  They also inhabit the same universe, and are therefore subject to the same physical laws.  The speed of light is the same here as it is everywhere else.  So are the masses of all of the different types of atoms.  Newton's Laws of Motion are always a good approximation to how objects move, as long as they aren't moving close to the speed of light.

The question becomes: how should we encode these common concepts?  The simplest way to send a message is to use a beam of light, perhaps from a radio transmission, perhaps using a visible laser.  We modulate the beam, changing its frequency (that is, its color) or its amplitude (how bright it is) as a function of time.  The sequence of the modulation gives a series of numbers: the message.

There are infinitely many ways to convey information in a message, ranging from analog recordings of music on AM radio to Morse code to the highly compressed image formats used to make the background of this page.  But to talk to aliens, we will need a simple format.

The Arecibo Message , several later compositions by Alexsandr Zaitsev and others , and the bulk of the Voyager Record used images.  Each number represented a pixel, and the lines were transmitted one after the other.  Pictures are ideal for conveying some times of information - the chemical structure of DNA, maps of planets, human faces.  But the alien watcher has to know to assemble the series of numbers into two-dimensional pictures, and be able to find the line breaks, before they can start to recognize the patterns we've included in them.

Purely pictorial messages are also time consuming for sending simple concepts.  The text of this page takes up 27 kilobytes - 216 thousand zeros and ones in your computer's memory.  But a picture of the text would take several megabytes, depending on the font size, with all of the lines in each letter and the whitespace between them.  So another class of message designs is based on small sets of numbers assembled into words, which in turn are used to construct an artificial language.  As an example:


It may take a little while to become obvious, but here '333' corresponds to '='.  See what happens if I replace '999' with '(' and '888' with ')':


See it now?  From defining equality, other ideas can be developed, from basic math through physics and astronomy.

After we've established the vocabulary, we can work on conveying more complex ideas.  Our goal is to learn how to reliably do that.  And we need your help.

We need testers to try and decrypt our message designs.  One test message is available by clicking the "Testing a Message" tab above.  Or, if you have a good idea for how to talk to aliens, please let us know by filling out the form below!