What is The Arecibo Message?
The
Arecibo message is a 1974 interstellar radio message carrying basic information
about humanity and Earth sent to globular star cluster M13. It was meant as a
demonstration of human technological achievement, rather than a real attempt to
enter into a conversation with extraterrestrials. The message was broadcast
into space a single time via frequency modulated radio waves at a ceremony to
mark the remodeling of the Arecibo radio telescope in Puerto Rico on 16
November 1974. The message was aimed at the current location of M13 about
25,000 light years 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.
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| Arecibo Message Image |
Who
wrote Arecibo Message?
Frank
Drake, then at Cornell University and creator of the Drake equation, wrote the
message with help from Carl Sagan and others.
Interesting fact about Arecibo message
The Arecibo message was meant as a demonstration of human technological achievement, rather than a real attempt to enter into a conversation with extraterrestrials.
In fact, the core of M13, to which the message was aimed, will no longer be in precisely the same location when the message finally arrives because of the orbit of the star cluster around the galactic center. However, as the proper motion of M13 is small, the message will still arrive near the center of the cluster.
Explanation
of Arecibo Message
The numbers one (1) to ten (10) (white)
The atomic numbers of the elements hydrogen, carbon,
nitrogen, oxygen, and phosphorus, which make up deoxyribonucleic acid (DNA)
(purple)
The formulas for the sugars and bases in the nucleotides
of DNA (green)
The number of nucleotides in DNA, and a graphic of the
double helix structure of DNA (white and blue, respectively)
A graphic figure of a human, the dimension (physical
height) of an average man, and the human population of Earth (red, blue/white,
and white, respectively)
A graphic of the Solar System indicating which of the
planets the message is coming from (yellow)
A graphic of the Arecibo radio telescope, and the
dimension (the physical diameter) of the transmitting antenna dish (purple,
white, and blue)
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.
The numbers from 1 to 10 appear in binary format, to be
read from the top down. The bottom row contains markers which indicate the
column from which the binary code for each number is intended to begin.
Even assuming that any extraterrestrial recipients would recognize binary, the encoding of the numbers may not be immediately obvious because of 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 their binary code has been distributed across an additional column next to the first (to the right in the image). This is intended to show that numbers too large to fit in a single column can be written in several contiguous ones (a scheme which is used elsewhere in the message). The additional columns are not marked by the least-significant-digit marker.
The numbers 1, 6, 7, 8, and 15 appear, denoting the atomic numbers of hydrogen (H), carbon (C), nitrogen (N), oxygen (O), and phosphorus (P), the elements from which DNA is composed
The chemical groups from which the nucleotides of polymeric DNA sequences are built – the sugar deoxyribose, phosphate, and the four canonical nucleobases used in DNA – are then described as sequences of the five elements that appear on the preceding line. Each sequence represents the molecular formula of the chemical as it exists when incorporated into DNA (as opposed to the free form).
A graphic of the approximate shape of the double helix in which double-stranded DNA polymers naturally exist; the vertical bar in the middle is a binary representation of the number of nucleotide base pairs in the human genome. The value depicted is around 4.3 billion, which was believed to be the case when the message was transmitted in 1974; it is now known that there are only approximately 3.2 billion base pairs in the human genome.
The element on the right of the image indicates the size
of the global human population in 1974, approximately 4.3 billion (which,
coincidentally, is within 0.1% of the number of DNA base pairs suggested for
the size of the human genome earlier in the message). In this case, the number
is oriented in the data horizontally rather than vertically. The
least-significant-digit marker is in the upper left in the image, with bits
going to the right and more significant digits below.
A graphic depicting the Solar System, showing the Sun and nine planets in the order of their distance from the Sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. (Pluto has since been reclassified as a dwarf planet by the International Astronomical Union, but it was considered a planet at the time the message was transmitted.) 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. Additionally, the human figure is shown just above the Earth graphic. In addition to showing position, the graphic also provides a general, not-to-scale size reference of each planet and the Sun.
The last part is a graphic representing the Arecibo radio
telescope and indicating its diameter with a binary representation of the
number 2,430; multiplying by the wavelength of 126 mm gives 306.18 m (1,004 ft
6 in). In this case, the number is oriented horizontally, with the least-significant-digit
marker to the lower right in the image. The part of the image that resembles a
letter "M" is there to demonstrate to the reader of the message that
the curved line is a paraboloid mirror.
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| Arecibo radio telescope |
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