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The Arecibo message is an interstellar radio message carrying basic information about humanity and Earth that was sent to the globular cluster Messier 13 (M13) in 1974.

The message was broadcast into space a single time via frequency-modulated radio waves at a ceremony to mark the remodeling of the Arecibo Telescope in Puerto Rico on 16 November 1974. The message was aimed at the current location of M13, about 25,000 light years from Earth, because M13 was a large and relatively close collection of stars that was available in the sky at the time and place of the ceremony. When correctly translated into graphics, characters, and spaces, the 1,679 bits of data contained within the message form the image shown here.

The content of the Arecibo message was designed by a group of Cornell University and Arecibo scientists: Frank Drake, formulator of the Drake equation; James C. The message was meant more as a demonstration of human technological achievement than a serious attempt to enter into a conversation with possible extraterrestrials. 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. The estimated number of DNA nucleotides in the human genome, and a graphic of the double helix structure of DNA (white and blue, respectively) A graphic of the Solar System (including Pluto), 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 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).

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).

The "Hampshire pattern" or "Chilbolton Code formation" or "Arecibo answer" was a crop circle that appeared in 2001 near the Chilbolton radio telescope in Hampshire, UK, which echoed the visual representation and most of the information from the original Arecibo message with some significant differences including location/origin, DNA configuration, and appearance. There is no evidence to suggest an other-than-earthly origin for these graphics." The crop circle is a near replica of the Arecibo message, with the same 23 × 73 grid.

Some researchers have analysed whether the Arecibo signal could be identified as a carrying message by some information theoretic measure that was agnostic in the sense that it does not know the particular shapes of a human or double-helix etc. Mahon (2025) described an information theoretic measure of complexity, the LCC score, that gives a high score to human language and meaningful images (such as photographs or drawings), and to the Arecibo message, while also giving a low score to random noise signals and simple repetitive signals. McCowan et al. (1999) described a measure called entropic slope, which could differentiate between random noise or repetitive signals, and meaningful vocalisations by multiple species including humans, but did not detect a message in the Arecibo signal.

Quick Facts

• The content of the Arecibo message was designed by a group of Cornell University and Arecibo scientists: Frank Drake, formulator of the Drake equation; James C.
• The message was broadcast into space a single time via frequency-modulated radio waves at a ceremony to mark the remodeling of the Arecibo Telescope in Puerto Rico on 16 November 1974.
• When correctly translated into graphics, characters, and spaces, the 1,679 bits of data contained within the message form the image shown here.
• The message was aimed at the current location of M13, about 25,000 light years from Earth, because M13 was a large and relatively close collection of stars that was available in the sky at the time and place of the ceremony.
• 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.

Source material: Wikipedia - "Arecibo message". Adapted and summarized for DiscoverScroll. Original contributors are credited through the linked Wikipedia article. Read original on Wikipedia. CC BY-SA 4.0. Changes were made from the original.