In one analysis, the researchers arranged the sequence of bits into images ranging from 0 to 200 pixels across, a subset of possible configurations. The team tested the method on a version of the Arecibo message that had been expanded to six times its size, so the width was now 138 pixels. But a mathematical approach could still reveal the message. Arranging the string of Arecibo bits into an image 73 pixels wide by 23 pixels tall would scramble the intended visuals (color added). By combining the local and global scores, the researchers have a sense of how likely each configuration is to be the correct one. The researchers also measure each possible configuration’s global order by seeing how much an image compression algorithm can shrink it without losing information - mathematically, randomness is less compressible than regular patterns. The patch scores are averaged to get an overall local order score for the entire configuration. (The programs’ outputs were precomputed and saved, making searches fast.) The more programs that create an identical patch, the higher the patch’s score for local order. For each patch, it searches a catalog of trillions of tiny computer programs the researchers had previously created to explore algorithmic space, and counts how many programs generate an identical patch. To get a measure of local order, it breaks the message into patches. It then looks at each possible configuration’s orderliness in two ways. 100 bits, for example, might be 1×100 or 10×10 (two dimensions) or 4x5x5 (three dimensions) or 2x2x5x5 (four dimensions) and so on. The new decoding method, developed by Hector Zenil, a computer scientist at the University of Cambridge and the founder of Oxford Immune Algorithmics, and colleagues, takes a string of bits - an incoming message - and looks at every possible combination of dimension number and size. A message in the form of a physics simulation could include a series of measures for each point in spacetime. A message might be a database in which each element is not just a value but a list of values, or a list of lists. But alien messages could come in many forms and have many dimensions, says Brian McConnell, a computer scientist at Notion Labs in San Francisco, and author of The Alien Communication Handbook. ![]() The Arecibo scientists built a clue into the transmission: 23 and 73 are prime numbers - a scheme other intelligent life might recognize, if they too find primes to be interesting. How would we know the number and size of its dimensions? ![]() We’d face a similar challenge if aliens sent us a message. If you line the bits up differently - placing more or fewer than 23 pixels per row - the image looks like a random mess. Johannes Rössel/Wikimedia Commons ( CC BY-SA 3.0)Īs it sent the signal, the radio antenna encoded the 1,679 bits by flipping between two different frequencies, representing one and zero respectively. The Arecibo message, beamed from Earth in 1974, was sent as 1,679 bits that created an image 23 pixels wide and 73 pixels tall (color added here to show the parts of the message).
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