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 some 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. The message forms the image shown here when translated into graphics, characters, and spaces.

Description

, then at Cornell University and creator of the Drake equation, wrote the message with help from Carl Sagan and others. 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 that location when the message arrives. However, as the proper motion of M13 is small, the message will still arrive near the center of the cluster.
The message consists of seven parts that encode the following :
The 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 number 1,679 was chosen because it is a semiprime, to be arranged rectangularly as 73 rows by 23 columns. :File:AreciboMessageShifted.svg|The alternative arrangement, 23 rows by 73 columns, produces an unintelligible set of characters.

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.
Even assuming that 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 they have been given an additional column next to the first. This is intended to show that numbers too large to fit in a single column can be written in several contiguous ones, where the additional columns do not have the least-significant-digit 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, carbon, nitrogen, oxygen, and phosphorus, the components of DNA.

Nucleotides

The nucleotides are described as sequences of the five atoms that appear on the preceding line. Each sequence represents the molecular formula of the nucleotide as incorporated into DNA.
For example, deoxyribose, the compound 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
11111111 11110111 11111011 01011110
= 4,294,441,822
DNA double helix; the vertical bar represents the number of nucleotides. The value depicted is around 4.3 billion, which was believed to be the case in 1974 when the message was transmitted. There are approximately 3.2 billion base pairs in the human genome.

Humanity

The element in the center represents a human. The element on the left indicates the average height of an adult male in the US:. This corresponds to the horizontally-written binary 14 multiplied by the wavelength of the message. The element on the right depicts the size of human population in 1974, approximately 4.3 billion. 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.

Planets

 Earth
Sun Mercury Venus Mars Jupiter Saturn Uranus Neptune Pluto

The Solar System, showing the Sun and the planets in the order of their position from the Sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto.
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 provides a general, not-to-scale size reference of each planet and the Sun.

Telescope

bottom two rows:
 100101
<--- 111110X --->
100101 111110 = 2,430

The last part represents the Arecibo radio telescope with its diameter: 2,430 multiplied by the wavelength gives. 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.

Arecibo answer hoax

The "Arecibo answer" is a hoax by people that created an imprint in a crop field in 2001 near the Chilbolton radio telescope in Hampshire, UK, portrayed as a response from an extraterrestrial civilization. The crop circle is a near replica of the Arecibo message. The feature forms the same 23 x 73 grid because these numbers are primes and most of the chemical data remains the same with the exception that in the section detailing important chemical elements, the main focus is altered from carbon to silicon, and the diagram of DNA has been rewritten. At the bottom, the pictogram of a human is replaced with a shorter figure with a large, bulbous head.