SETI Institute

Home News About us SETI Carl Sagan Center Education and Public Outreach Publications Support us teamseti

Computer Code: An Interstellar Language?

Jan. 16, 2003

by Douglas Vakoch - Social Scientist / Principal Investigator

If some day we decide to transmit intentional messages to the stars, rather than solely listen as current SETI programs do, what would we say? What sort of first impression would we want to give our celestial correspondents?

As an attempt to put our best foot forward, we might want to convey the idea that humans are familiar with the rules of fair play. And what better way than by showing the rules in action? But how would we format such an interstellar message?

Artificial intelligence expert Marvin Minsky suggested one natural possibility thirty years ago. At a major US-Soviet conference, he proposed that instead of sending detailed descriptions of complex systems, bit by tedious bit, there was an obvious alternative: send computer programs that mimic these systems instead. The key is to be clear about the individual steps that go into an accurate account.

For example, to generate the Fibonnacci seriesa mathematical sequence related to many natural phenomena and also to human aesthetic judgmentswe start by adding "1 + 1." We then take the result of this addition, "2," and add it to the last number that was used to get this sum (that is, the second "1"). We then repeat this process over and over: "1 + 1 = 2," "1 + 2 = 3," "2 + 3 = 5," "3 + 5 = 8," "5 + 8 = 13," and so on. We can specify these simple rules of addition very clearly in a computer program, and we will always get the same series: 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, and so on. In an interstellar message that attempts to communicate the Fibonnacci series, we could provide the recipients with a run of the program that they could use to check their understanding of the program.

But where would we start in teaching the basics of programming? Much of the foundation has already been laid in the most comprehensive interstellar message constructed to date. In this 1960 book called Lincos, short for Lingua Cosmica, Dutch mathematician Hans Freudenthal showed how we might introduce extraterrestrials to even very complex notions of logic and mathematics. His strategy was to construct an interstellar tutorial that went slowly, step by step. For example, after illustrating addition by numerous examples, multiplication can be introduced as an extension, adding the same number to itself some specified number of times. Similarly, multiplication serves as a steppingstone to the concept of squaring or cubing a numberof multiplying it by itself two or three times.

As we will see in our next column, we might take a similar approach to describe notions of human reciprocity. Though notions of sharing and promise keeping may seem beyond calculation, computer programs provide a good start for modeling the basics of these human social interactions. And if the intelligent beings who operate radio telescopes on other worlds are as reliant on computers as we are, such interstellar computer code might well provide extraterrestrials with a meaningful introduction to some of the essentials of human behavior.