Astronomy and Space

Can You Decode The Message Designed to Tell Aliens All About Humanity?

arecibo message

Assuming you are a person of reasonable intelligence, (actually, since you are a reader of Commonplace Fun Facts, we assume you are a person of extraordinary intelligence), what would you make of this audio message? Admittedly, it is a bit lacking in terms of catchy musical melodies or toe-tapping rhythm. Then again, it wasn’t designed to be a musical masterpiece. Its purpose is to tell alien species everything they need to know about humans. Still having trouble making sense of it? Keep reading, and learn about the origin and meaning of the Arecibo Message — humanity’s publicity piece for visiting extraterrestrials.

Binary and image side-by-side comparison of the Arecibo Message. Click on image to expand.

The Arecibo Message is an attempt to communicate basic information about humanity and Earth through a single, digital message. It was the brainchild of Frank Drake, who conceived the Drake Equation to calculate the number of communicative alien civilizations in the Milky Way.

The message was transmitted on November 16, 1974, from the Arecibo radio telescope in Puerto Rico. It was aimed in the direction of galaxy M13, located about 25,000 light-years from Earth.

The Arecibo Message consists of frequency modulated radio waves that can be converted into a binary string of 1,679 bits of ones and zeroes. This is a key point in deciphering the message. 1,679 is a semi-prime number. It is divisible only by one, itself, and the prime numbers 73 and 23. Knowing this should lead you to the obvious conclusion that the data should be mapped out in 73 rows and 23 columns. When you do this and substitute the ones and zeroes with full and blank squares, you get an image, as you can see demonstrated to the right.

When it arrives at M13, some 25,000 years from now, the message should tell any recipient the essentials about the species that transmitted it. That brings us back to the question we asked at the beginning of this post: what do you make of it?

We are confident all of this was immediately evident to you, but on the off chance that you missed one or two nuances of the message, we offer the following explanation of each of the elements.

Ordinal Numbers

The numbers from 1 to 10 appear in binary format, to be read from the top down. The bottom row contains markers that indicate the column from which the binary code for each number is intended to begin. 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.

Of course, you’re probably saying, “This is laughingly obvious! Why are you taking the time to explain something as self-evident as this?” At least, this was the response of the staff of the Mathematics For Alien Dummies Department of Commonplace Fun Facts. Then again, they tend to look down on non-mathematical types, anyway. Either that or their abysmal social skills preclude them from making eye contact with anyone to start with.

In any event, the above explanation is offered, because understanding the numbering system is essential to decoding the rest of the message.

DNA Elements

Once you understand the numbering system, the next section presents you with five numbers: 1, 6, 7, 8, and 15. What do those numbers represent? Well, they could stand for U.S. Presidents George Washington, John Quincy Adams, Andrew Jackson, Martin Van Buren, and James Buchannan. That doesn’t seem to produce much meaningful information, however.

Another possibility is to ascribe those numbers to the first of the Roman emperors: Augustus, Galba, Otho, Vitellius, and Antonius Pius. The first letters of these names can be used to spell VOGAPA. Unless that is a word in the language of the people of galaxy M13, however, that doesn’t seem to help us much.

Of course, there is the laughingly-obvious possibility that 1, 6, 7, 8, and 15 represent the atomic numbers for hydrogen, carbon, nitrogen, oxygen, and phosphorous. That would be almost too easy, however, because then, if you create a grid consisting of 6 columns, one for each of the aforementioned elements, and use the numbering system described in the first section, it would be stupidly obvious that the next section describes chemical groups from which the nucleotides of polymeric DNA sequences are built.

In fact, that is exactly what is going on. Deoxyribose, for example, is clearly evident in the upper left sequence of that section, illustrated in a grid that shows 7 hydrogen atoms, 5 carbon atoms, 0 nitrogen atoms, 1 oxygen atom, and 0 phosphate atoms. When rearranged to its more recognizable C5H7O, it becomes the chemical formula for deoxyribose, as it appears in DNA. If you were looking for C5H10O4, the formula for deoxyribose in its free form, you would be out of luck. The other images in this section describe the other chemical groups from which nucleotides of polymeric DNA sequences are built: adenine, thymine, phosphate, cytosine, and guanine.

DNA Structure

The next part appears to us to be a crude drawing of an alien’s head, complete with two antennae, and a huge spike thrust into the extraterrestrial’s skull. We assume that is a warning to any would-be alien overlords that we will not give up this planet without a fight.

Sadly, the intended message is not nearly as provocative. We say “sadly,” not because we necessarily favor rattling the saber at interstellar civilizations, but because of how poorly it manages to depict its intended message. The portion depicted in blue in the image to the left is supposed to show the double-helix form of a DNA molecule. This should be self-evident since the prior section addressed the composition of DNA.

Unfortunately, rather than show the graceful beauty of a true DNA double-helix, the Arecibo Message version suggests that human DNA is much like the human body: subject to sagging and loss of tone with age. We’d like to think that any 6-year-old who has played with a Lite Brite might have succeeded in generating a slightly less crude representation of the molecule, but we were taught not to publicly criticize other people’s art projects.

The spike-like structure down the middle of the double-helix is a binary representation of the number of nucleotide base pairs in the human genome. Unfortunately, the actual number of base pairs is around 3.2 billion, but the number represented in the Message is 4,294,441,882. Don’t be too hard on Dr. Drake, though; in 1974, everyone thought it was the larger number. Since it will be at least 25,000 years before the Message is received, perhaps human DNA will have mutated to something more closely resembling that of the Message. Either that or visiting aliens will conclude the dominant species on our planet is something like the Japanese flower Paris japonica, which, at 149 billion nucleotides, holds the record for having the largest genome of any species on Earth.

Human Bodies

The next section is supposed to tell extraterrestrials all about human bodies. If you worked through the prior section about DNA, that brings you down to a little representation of a person, who appears to be headless. We leave it up to you whether it is better to let aliens think we do not have heads or run the risk that they did not work through the DNA section properly, and have come to the conclusion that the human body has a huge, football-shaped head like Stewie Griffin on Family Guy.

To the left of the little digital human is a graphic designed to show the average height of an adult male (in the United States, anyway). It does this by a binary representation of “14” with a line moving upward to show that this refers to height. Assuming the readers of this part of the message successfully make the leap to the fact that we are now showing numbers horizontally instead of vertically and they decide to ascribe the number 14 to the height of humanoids, what unit of measurement should go with the number? The answer, naturally, is the wavelength of the message: 126 mm. Hence, 14 × 126 = 1,764 millimeters (5.79 feet).

To the right of the image is a binary representation of the number 4.3 billion. You could conclude that this is a reinforcement of the previously reported number of DNA base pairs in the human genome. You would be mistaken, but since the senders of the message were mistaken about the number of DNA base pairs, it all balances out. In reality, the 4.3 billion refers to the approximate size of the human population on Earth in 1974. This will be helpful if the aliens need to know how many warships to build to totally obliterate humanity.

Invasion Route Map of the Solar System

As a helpful navigational device for the genocidal alien overlords who undoubtedly will want to eradicate us benevolent extraterrestrial beings who unquestionably will want to share their technological advancements with us, the next section represents our solar system. The Sun and nine planets in the order of their distance from the are shown, with Jupiter and Saturn being shown three times larger than the smaller planets and Uranus and Neptune coming in at twice the size. Earth is shifted upward from the others to highlight our location. Additionally, the human figure is shown directly above it.

In the unfortunate event that the aliens do have evil designs against us, their invasion will no doubt be thwarted by the fact that our solar system is no longer considered to have nine planets. Pluto’s reclassification as a dwarf planet will certainly throw off the navigational charts of whatever Death Star they send our way.


The final part of the Message appears to be the letter “M” with an umbrella over it. It is intended to be a graphic representing the Arecibo radio telescope, as well as the number 2,430. When multiplied by the wavelength of the message (126 mm), it shows the diameter of the telescope at 306.18 m (1,004 ft 6 in). The letter “M” is designed to convey the fact that the curved line is a concave curved mirror because, as we all know, “M” is the intergalactic symbol for “concave curved mirror.”

Aliens as imagined by the creators of Space Invaders.

We just assume the folks at Galaxy M13 understand this last part to be a description of the telescope that transmitted the message. Based on the way humanity is described a couple of sections prior to this, one might just as easily conclude that the dominant species on Earth looks a lot like what the creators of the video game Space Invaders thought aliens looked like. Since the Arecibo Telescope collapsed on December 1, 2020, all of this is moot, anyway, and we hope the aliens don’t spend a lot of time trying to look for the source of the transmission.

That, in a nutshell, is the Arecibo Message and how to decipher it. You, of course, readily figured it all out on your own. If it were at all difficult to decipher the message, we never would have expected aliens to do anything useful with it, would we?

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