The Arecibo Message: Communicating With Alien Civilizations

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arecebo message in colourIn 1974, the Arecibo Radio Telescope beamed a powerful broadcast targeting the globular star cluster M13. Containing roughly 330,000 stars, and at a distance of 21,000 light years from Earth, the blast would be strong enough to be detected by an alien M13 civilization’s own version of SETI.

Dubbed “The Arecibo Message”, it was sent pictorially as a set of 1,679 bits, arranged into 73 rows with 23 characters per row, which are both deliberately prime numbers (the intent being that aliens could use these prime numbers to help decode the message). The bits were transmitted by frequency-shifting at the rate of 10 bits per second, and the total broadcast was just under 3 minutes.

The message contained:

  • The numbers one through ten;
  • The atomic numbers of the elements hydrogen, carbon, nitrogen, oxygen, and phosphorus (which collectively make up DNA)
  • The formulas for the sugars and bases in the nucleotides of DNA
  • The number of nucleotides in DNA, and graphic of the double helix structure of DNA
  • A graphic figure of a human, along with the average height, and the population of Earth
  • A graphic of the Solar System
  • A graphic of the Arecibo radio telescope, along with its dimensions

The message will take approximately 21,000 years to be received, and then 21,000 years to be returned back to Earth – so the probability of “contact” or “communication” is extremely low. However, as a thought experiment, it is interesting to think how an alien civilization may attempt to decode Earth’s message. On the Arecibo Wikipedia article, an explanation is given for each section in the pictorial.

arecibo message explained

For the message to be decoded, a number of assumptions must be made:

  • The alien civilization will need to understand binary format of counting, or Base-2.
  • “Chemistry”, as a whole, will be the same across the Universe. However, the building blocks of life might not. In the message, we assume 1) that the aliens will be able to decode the elements and formulae for the makings of DNA and its nucleotides, and 2) that life elsewhere in the Universe is made from the same organic building blocks
  • The depiction of Humanity, while immediately obvious to humans, may be completely foreign to an alien civilization. What if it’s normal for them to have 8 arms and 4 legs?
  • Without the use of language, it is incredibly difficult to assume that our solar system could be interpreted as a “solar system”. Especially now, with the declassification of Pluto as a planet – who knows how others might define celestial bodies?
  • The orientation of the message is critical for its understanding… if an attempt is made to interpret it as 23 rows by 73 columns, then the intended meaning is lost…

There’s no easy way to send a message into space that guarantees a high probability that it will be decoded correctly. Of course, having Wikipedia explain each row and column helps, but the aliens will certainly not have that luxury. Any form of media sent into space will degrade over time, and the aliens will probably not have VCRs, CD drives, DVD, BluRay, or Flash drives…

So, a radio message makes the most sense… however, I fear that, even if the Arecibo Message is received, it will remain encoded, hiding its mystery, must like many of the ancient texts from civilizations that are no longer here on Earth.


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