If you think about a future first contact with aliens, you probably imagine a very pessimistic scenario in which aliens are a much more intelligent species than humans, with much more advanced technology. So much so that they have managed to pay us a visit aboard several of their advanced spacecraft. You probably also imagine that their only goal would be to destroy or subjugate us. I can’t say much about what their goals would be. However, given the distances that separate stars within a galaxy and galaxies from each other, it is most likely that this first contact will not take place face to face, in person, but through messages exchanged at the speed of the light.
Humanity has wanted to take a certain initiative in this aspect and not simply dedicate itself to waiting for the arrival of one of these interstellar messages, but we have been proactive and have tried to initiate this communication. In recent decades, we have launched several messages directed at nearby stars and even distant star clusters, in the naive hope that someone will detect them on the other side. Also, and just in case, we have included some messages in probes launched to the far reaches of the solar system.
In 1974, for example, what is known as the Arecibo Message was issued. This message concentrated in its scant 1679 bits basic information about the Earth and human beings. This message was actually more of a display of our ability to send it than an actual contact attempt, as it was addressed to the star cluster M13, which contains several hundred thousand stars, but is located about 23,000 light-years from our planet. However, the message sent is so elegant that it is worth commenting on it.
The message can be seen in this image, where the different colors have been used to make it easier to see, since each little square would be nothing more than a 1 or 0 in its message: signal or no signal. The message starts by displaying the numbers 1 to 10 in binary base. This would help them decipher the rest of the message. Shown below in purple are the atomic numbers for the elements hydrogen, carbon, nitrogen, oxygen, and phosphorous , the elements that make up our DNA molecules. If their biology is minimally similar to ours, these elements will also be familiar to them, even if they do not combine to form identical structures.
The green block shows the chemical composition of the nucleotides that make up the DNA molecules . Using the same order as before, the amount of each of these elements in each molecule is shown. The white string represents the number of nucleotides present in a typical DNA molecule. This number, which is almost 4.3 billion nucleotide pairs, is the best estimate we had in 1974, we now know the real number is closer to 3.2 billion nucleotide pairs. Blue shows the structure of the DNA molecule, in the form of a double helix. The next block shows the approximate shape of a human body and our height on the left (14 times the wavelength of light used in the message) and the world population at the time the message was launched, which was about 4.3 billion humans. Today that figure is very close to 8 billion people.
The next line, painted in yellow, shows the main bodies of the solar system (Pluto was still considered a planet) and highlights the third planet from the Sun , indicating that this is the planet we inhabit. Finally , the shape and scale of the telescope used to launch this message is shown : the Arecibo radio telescope, 305 meters in diameter and which was active from 1963 to 2020.
Since 1974 our ability to send messages into space has grown and improved. Proof of this is the message “A Message from Earth” (A message from Earth), issued in 2008 in the direction of the star Gliese 581, located just 20 light years away. During the transmission, 501 selected messages were included among the half million entries of the contest that was created to decide what to send. Gliese 581 is a red dwarf, around which at least 3 planets have been discovered (with 2 more possible planets yet to be confirmed). The system will receive the human message in early 2029 . If there were a civilization with the ability to receive the message and send a response, it would not reach us until the year 2049.
In addition to 10 other similar messages sent to nearby stars or even to the North Star (located 433 light-years away), messages inscribed on metal disks were also included in the probes launched during the 1970s and ultimately directed at the interstellar medium. The Pioneer probes both included a plaque with a schematic of a man and a woman, the position of the Sun relative to nearby pulsars, and a sketch of the solar system and the path of the probes as they left it. The Voyager probes’ golden disc contained more information (in addition to including the pulsar map). These probes also included recordings of images and sounds. They include greetings in 55 languages, sounds of whale songs, sounds of rain, musical pieces such as songs from African or Amazon tribes, Australian aborigines, traditional Chinese, Mexican, Bulgarian music and even classical music. The first movement of Beethoven’s V Symphony is included. Also Johnny B. Good, by Chuck Berry.
These probes are unlikely to end up in the hands (or appendages) of any aliens. And if they do it will be in a long time. Voyager 1 will pass within 1.6 light-years of the star Gliese 445 in about 40,000 years. However, building them and selecting what to include in them can be a good exercise in deciding what is important to humans, as a species. What do we want to show the rest of the universe, in case of making contact.
References of interest:
Arecibo message: https://www.seti.org/seti-institute/project/details/arecibo-messageA message from Earth: https://amessagefrom.earth/Voyager Golden Record: https://voyager.jpl.nasa.gov/golden-record/
