A THOUGHT FOR TODAY:
I believe the greatest gift I can conceive of having from anyone is to be seen, heard, understood, and touched by them. The greatest gift I can give is to see, hear, understand, and touch another person.The content of the Arecibo message was designed by Frank Drake, then at Cornell University and creator of the Drake equation, who wrote the message with help from Carl Sagan and others.[1] The message was meant more as a demonstration of human technological achievement than a serious attempt to enter into a conversation with possible extraterrestrials.[1] As globular cluster M13, at which the message was aimed, is more than 25,000 light-years from Earth, the message, traveling at the speed of light, will take at least 25,000 years to arrive there. By that time, the core of M13 will no longer be in precisely the same location because of the orbit of the star cluster around the galactic center.[1] Even so, the proper motion of M13 is small, so the message will still arrive near the center of the cluster.[5]
The message consists of seven parts that encode the following (from the top down in the image):[4]
The entire message consisted of 1,679 binary digits, approximately 210 bytes, transmitted at a frequency of 2,380 MHz and modulated by shifting the frequency by 10 Hz, with a power of 450 kW. The "ones" and "zeros" were transmitted by frequency shifting at the rate of 10 bits per second. The total broadcast was less than three minutes.[1][6]
The number 1,679 was chosen because it is a semiprime (the product of two prime numbers), to be arranged rectangularly as 73 rows by 23 columns.[7] The alternative arrangement, 23 rows by 73 columns, produces an unintelligible set of characters.
The waterhole, or water hole, is an especially quiet band of the electromagnetic spectrum between 1420 and 1662 megahertz, corresponding to wavelengths of 21 and 18 centimeters, respectively. It is a popular observing frequency used by radio telescopes in radio astronomy.[1]
The strongest hydroxyl radical spectral line radiates at 18 centimeters, and atomic hydrogen at 21 centimeters (the hydrogen line). These two molecules, which combine to form water, are widespread in interstellar gas, which means this gas tends to absorb radio noise at these frequencies. Therefore, the spectrum between these frequencies forms a relatively "quiet" channel in the interstellar radio noise background.
Bernard M. Oliver, who coined the term in 1971, theorized that the waterhole would be an obvious band for communication with extraterrestrial intelligence,[2] hence the name, which is a pun: in English, a watering hole is a vernacular reference to a common place to meet and talk. Several programs involved in the search for extraterrestrial intelligence, including SETI@home, search in the waterhole radio frequencies.
