Transcript: Rather than simply theorize or speculate, astronomers have been conducting modest experiments in interstellar communication. One of the first and most famous was done in 1974 using the Arecibo Radio Telescope, a thousand-foot radio dish in Puerto Rico. A pulsed set of messages was sent out sequentially to the M13 globular cluster. The sequence of signals consisted of one thousand six hundred and seventy-nine bits of information, that is on-off radio pulses. An intelligent civilization receiving such a message would presumably realize that sixteen seventy-nine has only two factors, seventy-three and twenty-three, suggesting hopefully two ways to arrange the information in a grid. One way produces a meaningless picture but the other way clearly indicates graphics if you also understand that you are to turn the bright or on signals into dark and the light into off, thus converting on-off signals into light and dark, or a picture. When shown this way, the Arecibo signal consists of a graphic of the solar system, of the Arecibo Radio Telescope, a little stick man, a schematic of the DNA molecule, and eight of the primary amino acids involved in life, but it’s just a schematic. There is no language involved and a civilization would have to understand what it means. It’s all very hypothetical anyway because M13 is twenty-five thousand lightyears away, so we will have to wait nearly fifty thousand years for a response if any is coming.