A picture is worth a thousand words, especially if you're trying to get your point across to someone who doesn't speak your language.

Messages From ET

Click here to read Messages From ET: Part One.

Click here to read Messages From ET: Part Two.

At least that has been the assumption of many proposals for communicating with extraterrestrials.

For example, in a message transmitted from the worlds largest radio telescope in Arecibo, Puerto Rico, images of a human being, the double helix of DNA, our solar system, and the radio dish itself were included.

But would pictures necessarily be understood at interstellar distances?

When we consider the pictures drawn by diverse cultures here on Earth, we can see that pictures don't merely reflect reality as it independently exists.

Instead, any attempt to picture an object is based on certain assumptions about which aspects of an object to emphasize.

What seems obvious in one culture might be incomprehensible in another.

The Abelam artist from Papua, New Guinea, for instance, might represent the human form like this (see below):

To the outsider untrained in the representational conventions of this culture, the picture may be meaningless, seeming to be an example of an interesting geometrical design with no direct connection to the real world. To the initiated, however, a few of the lines in this image represent limbs, while the circles indicate eyes.

The lesson for interstellar communication is humbling. If humans have this much difficulty comprehending individuals of their own species, having direct contact with their works of art, how much more difficult will it be to bridge the gap between worlds separated by vast expanses of interstellar space?

Might there be something even more fundamental than pictures? After all, when pictures have been proposed for interstellar communication, often non-pictorial information has been included. For example, the Arecibo message noted above included numbers representing some of the key elements needed for life on Earth, the chemical structure of DNA, the population of Earth, and even the height of the human being pictured in the message. In fact, some people have proposed entirely non-pictorial methods for interstellar communication.

Consider, for example, a proposal from the Dutch mathematician Hans Freudenthal. In 1960 he advanced his own "cosmic language," appropriately named Lingua Cosmica, or Lincos for short. In Freudenthals scheme, pictures came very late in the message, and in fact, werent essential at all. Rather than rely on pictures, Freudenthal constructed a complex mathematical language that might be transmitted via radio signals. Some of the first lessons in his interstellar primer were basic counting, addition, and subtraction.

To understand how this works, the process of subtraction can be communicated by a string of pulses transmitted at radio frequencies. Pulses of one kind could represent numbers, and a different type of pulse could stand for the concepts of subtraction (the "-" sign) and equality (the "= " sign). With a few examples like "4 1= 3" and "8 2= 6" we could introduce basic arithmetic, simply by transmitting a series of pulses.

By combining pictures and numbers, as was done in the Arecibo message; we might be able to communicate more than by either mathematics or images alone. And with the immense challenges posed by interstellar communication, we might expect extraterrestrials to hedge their bets as well.

If some day we detect an information-rich signal from ET, well no doubt attempt to decode it. When we do, lets keep in mind the variety of ways its senders might tell their story to humankind.