- Arecibo message
The Arecibo message was beamed via frequency modulated
radio waves into space at a ceremony to mark the remodeling of the Arecibo radio telescope on16 November 1974 .cite web|url=http://www.news.cornell.edu/releases/Nov99/Arecibo.message.ws.html |title=Cornell News: It's the 25th anniversary of Earth's first (and only) attempt to phone E.T., FOR RELEASE: Nov. 12, 1999|accessdate=2008-03-29] It was aimed at the globular star cluster M13 some 25,000light year s away because M13 was a large and close collection of stars that was available in the sky at the time and place of the ceremony. [cite web|url=http://www.zwire.com/site/news.cfm?newsid=15663534|title=Larry Klaes. Ithaca Times - Making Contact|accessdate=2007-07-27] The message consisted of 1679 binary digits, approximately 210byte s, transmitted at a frequency of 2380 MHz and modulated by shifting the frequency by 10 Hz, with a power of 1000kW. Thecardinality was chosen because it is asemiprime cite web|url=http://www.physics.utah.edu/~cassiday/p1080/lec06.html|title=The Arecibo Message|last=Cassiday|first=George|accessdate=2007-07-27] (the product of twoprime number s), to be arranged rectangularly as 73 rows by 23 columns. The alternate arrangement, 23 rows by 73 columns, produces jumbled nonsense. The message forms the image shown on the right, or its inverse, when translated into graphics characters and spaces. The entire transmission lasted 1679 seconds and was not repeated. [cite web|author=Jay M. Pasachoff|title=Chapter 20: Life in the Universe|work= [http://www.williams.edu/Astronomy/jay/ETU5/updates.html Astronomy: From the Earth to the Universe, Updates by Chapter, 5th Ed.] |url=http://www.williams.edu/Astronomy/jay/ETU5/chapter20_5th.html| accessdate=2007-05-05]Dr.
Frank Drake , then atCornell University and creator of the famousDrake equation , wrote the message, with help fromCarl Sagan , among others. The message consists of 7 parts that encode the following:
#the numbers one (1) through ten (10)
#theatomic numbers of the elementshydrogen ,carbon ,nitrogen ,oxygen , andphosphorus , which make updeoxyribonucleic acid (DNA)
#theformula s for thesugar s and bases in thenucleotides of DNA
#the number of nucleotides in DNA, and a graphic of the double helix structure of DNA
#a graphic figure of a man, the dimension (physical height) of an average man, and the human population of Earth
#a graphic of Earth'ssolar system
#a graphic of the Arecibo radio telescope and the dimension (the physical diameter) of the transmitting antenna dishBecause it will take 25,000 years for the message to reach its intended destination of stars (and an additional 25,000 years 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. In fact, the stars that the message was aimed at will no longer be there when it arrives. According to the Cornell News press release of Nov. 12, 1999, the real purpose of the message was not to make contact, but to demonstrate the capabilities of newly installed equipment.
Explanation
Numbers
1 2 3 4 5 6 7 8 9 10 ---------------------- 0 0 0 1 1 1 1 00 00 00 0 1 1 0 0 1 1 00 00 10 1 0 1 0 1 0 1 01 11 01 X X X X X X X X X X <-least-significant-digit marker
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 seven digits, ignore the bottom row, and read them as three binary digits from top to bottom, with the top digit being the most significant.
The readings for 8, 9 and 10 are a little different, as they have been given an additional column next to the first (to the right in the image). This is probably intended to show that numbers too large to fit in a column can be written in several contiguous ones, where the contiguous columns do not have the base marker.
DNA elements
H C N O P 1 6 7 8 15 ---------- 0 0 0 1 1 0 1 1 0 1 0 1 1 0 1 1 0 1 0 1 X X X X X
The numbers 1, 6, 7, 8 and 15 appear. These are the atomic numbers of
hydrogen (H),carbon (C),nitrogen (N),oxygen (O), andphosphorus (P), the components of DNA.The numbers 8 and 15 are written in a logical extension of binary encoding, rather than with the contiguous-columns method shown in the message's number figures at the top:
Nucleotides
Deoxyribose Adenine Thymine Deoxyribose (C5OH7) (C5H4N5) (C5H5N2O2) (C5OH7)Phosphate Phosphate (PO4) (PO4)Deoxyribose
Cytosine Guanine Deoxyribose (C5OH7) (C4H4N3O) (C5H4N5O) (C5OH7)Phosphate Phosphate (PO4) (PO4)
The
nucleotides are described as sequences of the five atoms that appear on the preceding line. Each sequence represents themolecular formula of the nucleotide as incorporated into DNA (as opposed to the free form of the nucleotide).For example, deoxyribose (C5OH7 in DNA, C5O4H10 when free), the nucleotide in the top left in the image, is read as:
11000 10000 11010 XXXXX ----- 75010
i.e. 7 atoms of hydrogen, 5 atoms of carbon, 0 atoms of nitrogen, 1 atom of oxygen, and 0 atoms of phosphorus.
Double helix
11 11 11 11 11 01 11 11 01 11 01 11 10 11 11 01 X
1111111111110111 1111101101011110 (binary) = 4,294,441,822 (decimal)
DNA double
helix (the vertical bar represents the number of nucleotides, but the value depicted is around 4.3 billion when in fact there are about 3.2 billion base pairs in the human genome).Humanity
X011011 111111 X0111 110111 111011 111111 110000
1110 (binary) = 14 (decimal)
000011 111111 110111 111011 111111 110110 (binary) = 4,292,853,750 (decimal)
The element in the center represents a human. The element on the left (in the image) indicates the average height of a person: 1764 mm. This corresponds to the horizontally written binary 14 multiplied by the
wavelength of the message (126 mm). The element on the right depicts the size of human population in 1974, around 4.3 billion. In this case, the number is oriented horizontally rather than vertically, with the least-significant-digit marker to the upper left in the image.Planets
Earth Sun Mercury Venus Mars Jupiter Saturn Uranus Neptune Pluto
The
solar system , showing theSun and the planets in the order of their position from theSun : Mercury, Venus,Earth , Mars, Jupiter, Saturn, Uranus, Neptune, andPluto . (Pluto is now classified as adwarf planet , but was still considered a planet at the time the message was written.)The Earth is the third planet from the
Sun - its graphic is shifted up to identify it as the planet from which the signal was sent. The human figure is shown "standing on" the Earth graphic.In addition to showing position, the graphic provides a general, not-to-scale size reference of each planet and the Sun.
Telescope
bottom two rows: 100101 <--- 111110X --->
100101 111110 (binary) = 2,430 (decimal)
The last part represents the
Arecibo radio telescope with itsdiameter (2430 multiplied by the wavelength gives 306.18 m). In this case, the number is oriented horizontally, with the least-significant-digit marker to the lower right in the image.
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