This is an existential question that humanity has been asking for thousands of years. In our incredible universe, could other forms of life exist? Between mystery and fascination, scientists worldwide are studying the subject. Many research programs have been put in place, and technological progress pushes us every day to want to learn more about this possibility. Let's discover together the origins of the extraterrestrial theory and the possible signals that have been given to us.
Extraterrestrial life: an idea that dates back to Antiquity
Extraterrestrial life refers to any form of life present elsewhere than on planet Earth. The first time the subject of extraterrestrials was discussed dates back to Antiquity. Indeed, many Greek philosophers speculated in their writings that there might potentially be other civilizations than humans in the Universe. These beings from elsewhere would live on exoplanets: this is how the theory of "cosmic plurality" was born. At that time, it was impossible to state that extraterrestrials existed. Scientific prowess was not yet powerful enough to find life anywhere other than on Earth. However, this theory has traversed the centuries with defiance, thus pushing scientists year after year, and even today, to never let up on research and never forget this possibility.
To better understand this phenomenon, a new science was created starting in the 1920s: exobiology, dedicated to the search for factors and processes that led to the appearance of life and its evolution. Exobiology is thus considered the first official discipline that seeks traces of extraterrestrial life.
Mars, the most considered planet for extraterrestrial life
Unlike other planets in the Solar System, it is possible that Mars was in the past quite close to the conditions prevailing on Earth, which would then have allowed the appearance of life, although this has not been demonstrated. Following the invention of the telescope, a lot of information could be found concerning Mars: it is a terrestrial planet, which is capable of changing color on its surface (thus suggesting vegetation that would evolve according to the seasons).
From 1975, research into extraterrestrial life intensified: a first attempt was made by NASA to gather clues using the Viking program's space probes. Thus, these two probes were sent to the surface of the planet Mars. Since the late 90s, NASA has also been pursuing a space exploration program aimed at finding traces of extraterrestrial life, present or fossil, on Mars: soils are analyzed with the creation of the Curiosity rover, and methane sources as well as environments favorable to life forms are identified on what is called the Red Planet.
Despite this theory, Mars is not the only planet considered to harbor extraterrestrial life: the underground oceans present in Europa, Jupiter or Saturn's moon, or even the planet Titan constitute other avenues to explore.
Attempts at radio communication
In the 19th century, the idea of being able to communicate with extraterrestrials emerged. Carl Friedrich Gauss, a German mathematician, physicist, and astronomer, imagined planting a field of pine trees within a wheat field, thus creating a contrast that should be visible from Mars and would encourage extraterrestrials to come to Earth. Later, Charles Cros, a French poet and inventor, set about creating an electric lamp that he would position in front of a star and which would send periodic signals. Furthermore, Nikola Tesla, for example, was convinced that he had picked up signals from Mars. He then began to study the feasibility of communication by Hertzian waves from the 1930s onwards: this was the creation of radio astronomy.
Thus, all of humanity began listening to various radio wave emission sources, hoping to find a message! It was from this era that science fiction took on its full meaning and extraterrestrials became a recurring theme in literary and artistic works.
The SETI research program... and the WOW! signal
The SETI (Search for Extra-Terrestrial Intelligence) program is a set of American research initiatives whose objective is to detect the presence of extraterrestrial civilizations. The first project was launched in 1960 at the beginning of the space age by astronomer Frank Drake. SETI program members try to detect electromagnetic waves emitted by civilizations that have entered the industrial, technological, and scientific stage. Thus, this program serves to determine whether non-terrestrial intelligence could emit signals from its home planet, voluntarily, targeting us or not. This then implies the theory that extraterrestrials would be very technologically advanced and would possess knowledge that could surpass that of humans.
On August 15, 1977, an unexpected phenomenon occurred as part of a SETI project. Named the "WOW signal", this major event has still not been elucidated. Indeed, the "WOW signal", which owes its name to the sensation felt by the scientist who discovered it, is a powerful radio signal picked up by the radio telescope of Ohio State University, also nicknamed The Big Ear. Detected for 72 seconds and never re-detected since, it held the world in suspense for several years. Neither the origin nor the nature of this signal is known, but the theory indicates that the signal was narrowband (approximately 10 kHz), whereas no natural phenomenon emits from a narrow spectrum. Furthermore, the signal was emitted from the 21 cm line, which corresponds precisely to the frequency at which we expect to receive possible signals from extraterrestrial civilizations! A mystery that therefore remains complete to this day because no logical explanation has been demonstrated...
FERMI's paradox
FERMI's paradox is a paradox stated in the 1950s by the physicist Enrico Fermi. His hypothesis is based on the fact that until then, no extraterrestrial civilizations had contacted us, even though the age of our galaxy, estimated at 10 billion years, should have allowed some of them to access interstellar travel and leave visible traces of passages in our solar system.
Thus, Enrico Fermi put forward several hypotheses concerning this paradox:
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At least one extraterrestrial civilization within the Milky Way would have succeeded in developing interstellar travel thanks to vessels traveling at a speed much lower than the speed of light,
- This civilization, for an unknown reason, explores and colonizes our galaxy,
- It would progress in leaps and bounds, colonizing a planet for a few hundred or thousand years, before sending dozens of vessels towards new conquests.
Therefore, according to Enrico Fermi's calculations, the entire galaxy should have been visited or colonized by an extraterrestrial civilization after only a few hundred million years, since the low speed of the ships would be largely compensated by the significant increase in the number of colonization ships. Fermi then expressed what would become the paradox that bears his name: "if extraterrestrials exist, then where are they?" Indeed, a million years is not much on the scale of the galaxy, so extraterrestrials should be omnipresent and it should be impossible not to see them. However, since this theory, other hypotheses have been put forward to explain this paradox:
- The tendency to colonize is an anthropocentric concept, meaning it is more specific to humans and it is difficult to demonstrate it in other civilizations: just because humans colonize does not mean that extraterrestrials would necessarily do so.
- Humanity is not necessarily aware of all the forms of life that surround it. As proof, many discoveries are made over centuries and not acquired in an instant. Furthermore, an advanced extraterrestrial civilization could potentially hide and avoid contact with humans: therefore, just because we don't see them doesn't mean they aren't there.
- Finally, the late appearance of heavy elements in the Universe and necessary for the development of life in its known form may have delayed the appearance of other extraterrestrial civilizations.
The ancient astronaut theory... and the places on Earth said to be built by extraterrestrials!
The ancient astronaut theory is a theory according to which ancient civilizations such as the Mayans, Incas, and Egyptians would have been in contact with extraterrestrials in the past. These extraterrestrials would then have offered their knowledge in disciplines such as mathematics and science, but also in agriculture, architecture, and medicine. Thus, these beings from elsewhere would have been considered gods by ancient civilizations, as they are found in the mythologies and archaeology of these ancient cultures.
According to the theory, several hypotheses have been formulated:
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Ancient civilizations would not have possessed the necessary knowledge to construct certain colossal buildings.
- Several elements seem to indicate that extraterrestrial presences would have been in contact with ancient civilizations: numerous frescoes found depict characters that would represent astronauts, UFOs, or even landing strips.
- Extraterrestrials would have had a considerable influence on the evolution of mankind by teaching them various sciences, or even by altering DNA to promote a more intelligent evolution.
Thus, many speculations suggest that the pyramids of Egypt, Easter Island, or the Stonehenge stone circle were built by extraterrestrials. Unfortunately, this theory has never been proven, and archaeologists agree that the techniques used on these imposing constructions would indeed reflect the means and working methods of the time, although a part of the mystery still remains…
Ufology enthusiasts, we hope you enjoyed this article! If you wish to continue enriching your knowledge, we also recommend reading our article on the 8 planets of the Solar System.
