On November 16, 1974, a group of scientists gathered in the middle of Puerto Rico to send the most ambitious “hello” in history. From the Arecibo Radio Telescope, a radio beam came out that still travels through space today, a sequence of zeros and ones carrying information about the Earth and its inhabitants. It was the Arecibo Message, a 1,679-bit cosmic capsule destined for the M13 star cluster, about 25,000 light-years away.
The experiment, led by astronomer Frank Drake, creator of the famous Drake Equation, which calculates the probability of the existence of civilizations, and by the also renowned Carl Sagan, marked one of the most symbolic moments in modern astronomy.
The sending of the message coincided with the reopening of the , which had been renovated to become one of the most powerful observation instruments on the planet. Arecibo was also a philosophical gesture: a nod to the cosmos in the name of human curiosity.
A portrait in binary code
The message sent did not have words, but numbers. Composed of 1,679 bits, a number purposely chosen because it is the product of two prime numbers (23 and 73), it can only be organized in a specific way to reveal a visual pattern, as if it were a mosaic of spatial pixels.
When decoded correctly, the image shows seven main sections. The first three present basic information and chemistry: the numbers from 1 to 10, the fundamental elements of life (carbon, nitrogen, oxygen and phosphorus) and the chemical formulas of the components of . Then, the representation of the double helix of DNA appears, accompanied by the figure of a human being, with its average height (1.76 m) and the population of the Earth at the time (4.29 billion people).
At the bottom, the message shows a diagram, highlighting Earth as the point of origin, and, finally, the drawing of the Arecibo radio telescope, with a diameter of 305 meters. In other words, it was a business card for humanity: simple, mathematical and universal.
A message that no one will hear, for now
The chosen destination, the M13 cluster, brings together around 300,000 in the Hercules constellation. Even if intelligent life exists there, the signal will only reach its destination in the year 27,974. And if there is an answer, it will return another 25 thousand years later. In practical terms, the Arecibo Message was never intended to open a dialogue, but rather to show that humanity was capable of speaking the language of the universe, mathematics and physics.
Still, the experiment sparked imaginations around the world. Decades later, in 2001, a crop circle appeared in a field near the Chilbolton observatory, in England, reproducing a kind of “response” to the original message. The drawing featured similar figures, but with small changes, suggesting another form of life. The supposed answer, however, was quickly attributed to human artists. Still, the episode reinforced the collective fascination around Arecibo.
The end of the giant and the legacy that remains
For nearly five decades, the Radio Telescope was one of the most iconic scientific structures on the planet. He has helped discover extrasolar planets, monitored near-Earth asteroids, and supported searches for extraterrestrial signals (SETI). But in December 2020, the observatory collapsed after structural failures, ending an era of discoveries.
Even so, the beam sent in 1974 continues its silent journey through interstellar space and is expected to continue traveling for millennia.
