Arecibo message
From Freepedia
The Arecibo message is a radio message that was beamed into space at a ceremony to mark the remodeling of the Arecibo radio telescope in 1974. It was aimed at the globular star cluster M13 some 25,000 light years away and consisted of 1679 binary digits. The number 1679 was chosen because it is the product of two prime numbers and therefore can only be broken down into 23 rows and 73 columns, or 73 rows and 23 columns. This assumes, however, that those who read it will choose to arrange it as a quadrilateral. The information arranged the first way produces jumbled nonsense, but if arranged the second way it forms an image containing information about Earth and the human race. Reading from right to left, it shows the numbers one through ten, the atomic numbers of hydrogen, carbon, nitrogen, oxygen, and phosphorus, the formulas for the sugars and bases in the nucleotides of DNA, the number of nucleotides in DNA, the double helix structure of DNA, a figure of a human being and its height, the population of Earth, our solar system, and an image of the Arecibo telescope with its diameter.
Because it will take 25,000 years for the message to reach its intended destination of stars (and an additional 25,000 for any reply), the Arecibo message was more a demonstration of human technological achievement than a real attempt to enter into a conversation with extraterrestrials.
Dr. Frank Drake, then at Cornell University and creator of the famous Drake equation, wrote the message, with help from the late Carl Sagan, among others.
The effectiveness of this message is very controversial. What can be considered a superb joke about the Arecibo Message was made by "cropcirclers" near Chilbolton's Observatory, depicting a similar message (from a grey-type aliens) that included silicon in their biochemistry and other subtle changes in the data, like the three inhabitated planets of their native system.
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Explanation
Numbers
Read from right to left, the numbers from 1 to 10 appear in binary format (the bottom row marks the beginning of each number).
Even knowing binary, the encoding of the numbers may not be immediately obvious due to the way they have been written. To read the first six digits, ignore the bottom row, and read them as three binary digits from bottom to top. The readings for 8, 9 and 10 are a little different, as they have been given an additional column to the left of the first.
00 00 00 1 1 1 1 0 0 0 01 00 00 1 1 0 0 1 1 0 10 11 10 1 0 1 0 1 0 1 X X X X X X X X X X <-least significant digit marker
DNA elements
The numbers 1, 6, 7, 8 and 15 represent hydrogen (H), carbon (C), nitrogen (N), oxygen (O) and phosphorus (P) respectively. These are the components of DNA.
Nucleotides
Deoxyribose C5OH7, Adenine C5H4N5, Cytosine C5H5N2O2, Deoxyribose C5OH7
Deoxyribose C5OH7, Thymine C5H5N3O, Guanine C5H4N5O, Deoxyribose C5OH7
Double helix
DNA double helix (the vertical bar represents the number of nucleotides)
Humanity
The element in the center represents a man. The element on the left indicated the average height of a man: 1764 mm. This corresponds to the horizontally written binary 14 multiplied with the wavelength of the message (126 mm). The element on the right depicts the size of human population encoded with 32 bits: 4'292'591'583
Planets
The solar system: the Sun, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto.
The Earth is misaligned to show where the message came from.
Telescope
The last part represents the Arecibo radio telescope with its diameter (2430 multiplied with the wavelength gives 306.18 m).
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