DOCID: 3052333
FOR ORICIAL USE ONLY
Cornell University and the National Science Foundation. Messier 13 is a cluster of 300,000 stars on the edge of the Milky Way, 24,000 light years away, so if the message is received and answered promptly, unless we happen to hit them on one of their three-day holidays we should have their answer in 48,000 years, give or take a day or two. Actually, the main purpose of the experiment was to dramatize the capabilities of the world's largest antenna at the Arecibo Observatory.
If another civilization were trying to establish communication with us, it would first embark on attention-getting signals of such a nature that we could distinguish them from random cosmic noise; once we receive a recognizable signal, we have a good chance of u'nderstanding the message. For example" they could start with trains of signals corresponding to the natural number 1, 2, 3. . . , followed perhaps by prime numbers. They might continue with equal-length extended signals consisting of start and stop impulses, with occasional pulses in between; when these signals are aligned flush over one another, they would show a circle, the
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Pythagorean Theorem, or similar geometric design. These attention-getting signals would be followed by what amounts to early "language lessons," interspersed with items of technical information to help bring us up to the level of our superiors, "them."
It may be assumed that the sense of sight, or an equivalent, is possessed by all higher' forms of life; the problems of communication could thus be greatly simplified through the medium of a "raster" representation such as that of a television screen. After a conference held at Green Bank in 1961 to discuss the possibility of communication with other planets, one of the participants, Bernard M. Oliver, made up a hypothetical message on the raster principle. The message, consisting of 1271 binary digits or "bits," is shown in Figure 1. Since 1271 has but two prime factors, 31 and 41, we would naturally be lead to write out the message in raster form, in 41 lines of 31 bits each, or in 31 lines of 41 bits each; the latter case reveals a greater nonni.ndomness in the patterns disclosed, indicating that these are the correct dimensions.

The above is from [link to www.nsa.gov]

Look at the picture they put together on page 3.