For decades, humanity has been listening to space for messages from extraterrestrial civilizations. Any unusual signals are carefully checked. But what happens if we actually receive a message from other worlds?
Almost 40 years ago, in August 1977, American radio astronomer Jerry Eiman scanned a section of the sky with a radio telescope, hoping to find a message from an extraterrestrial civilization.
Suddenly, he detected a very short but intense signal, the characteristics of which indicated that its source may be outside the solar system.
On the printout, Eiman circled the group of symbols corresponding to the signal with a red pen and added the word "Wow!" ("Wow!").
No one has been able to give an unambiguous explanation to the signal "Wow!", As it has been called since then, and nothing like it has ever been detected.
But an organization called the Search for Extraterrestrial Intelligence (SETI) Institute continues to listen to the airwaves in hopes of detecting signals sent by intelligent life forms in our galaxy and beyond.
What happens if SETI can detect such a signal? How can scientists make sure that it is indeed sent by an alien civilization?
In a recent Science Channel documentary, Apollo 10 astronauts heard strange "space music" on their headphones while flying over the far side of the moon.
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Many scientists believe that ordinary radio interference was the cause. However, that incident raised an important question: how to distinguish cosmic noise from intentional radio transmission?
“Detecting unusual signals is common, but usually rationalized,” says Dr. John Eliot of Leeds Beckett University in Britain. "It is rare that such material is handed over for closer study to the analysis group."
The Analysis Group is a small scientific council dedicated to studying particularly interesting signals recorded by radio telescopes around the world.
Eliot, who is part of the group, spent a lot of time thinking about what would happen if we ever received a message from extraterrestrial intelligence.
Eliot has been involved with the SETI project since 1999, and he says the analysis team receives, on average, one signal to study every two years.
Unusual signals are recorded almost every day, but they are quickly screened out as natural or artificial electromagnetic interference.
A sensible signal can come from anywhere. There is even the so-called SETI League - a group of volunteer radio amateurs who monitor the broadcast with their own equipment.
“If the received signal has periodically repeating elements, it will generate increased interest,” explains Eliot.
"In this case, the question will have to be asked: does this repeating scheme correspond to the level of complexity of the signal, which may contain a language message, mathematical formulas or any other meaningful information."
It is unlikely that we will immediately be able to decipher the alien message, but we can at least determine that they are trying to tell us something.
SETI has a growing list of candidate signals. To assess the potential likelihood that a signal comes from extraterrestrial intelligence, the ten-point Rio scale is used: signal parameters such as its technical characteristics, detection method and distance to the source are taken into account.
The Apollo 10 crew members were silent for many years about the "space music" they heard.
This became known only in 2008, when NASA published the recordings of the astronauts' talks during the expedition (the crew decided not to inform the Mission Control Center about the observed phenomenon).
Any really interesting signals found by the SETI project will eventually go public, but first they must go through a rigorous verification process.
For this, SETI has developed a special contact protocol, which implies an independent analysis of the received signal.
Dan Vertimer of the University of California, Berkeley, who is also a member of the analysis team, notes that team members have to be very careful in their assessments.
“It could be a bug in our software or a prank by a student, so we need to get confirmation from independent sources,” he says.
The public interest in a possible alien signal would undoubtedly be quite high.
In 2004, astronomers had to cool the hype caused by erroneous reports on the Internet about a supposedly registered extraterrestrial signal.
And last year, the SETI project discovered a series of so-called fast radio pulses, which for some time puzzled scientists.
There was no reasonable explanation for these impulses, which led many to speculate that they were of an alien origin.
So is it possible in principle to reliably establish the origin of an unusual signal?
One of the deciding factors here is the distance traveled. If the recorded signal simply bounced off a satellite or space debris in near-earth orbit, it can hardly be considered an attempt by extraterrestrial intelligence to establish contact with us.
“With two radio telescopes receiving the same signal from different points, you can triangulate the source by calculating the distance traveled by the signal - then it becomes clear how far the source is from the Earth,” says Vertimer.
However, the need for such a technique has not yet arisen, he adds: "Until now, we have not come across a signal so unusual that we would have to call the director of an observatory and ask him to urgently provide us with access to an additional radio telescope."
Another question that Eliot and many other scientists are asking is how exactly to respond to a signal, the extraterrestrial origin of which is beyond doubt. Is it worth answering at all?
The SETI Protocol states: "Any response to a signal or other evidence of the existence of extraterrestrial intelligence should be refrained from until appropriate international consultations are held."
“There is still no consensus on what to do in this case. There are two main schools of thought - yes, you definitely need to answer, and no, you can’t answer in any case,”says Eliot.
In his personal opinion, not trying to answer would be to miss an extremely rare chance.
However, if you try to answer, a new problem will arise - how exactly to communicate with an alien mind without speaking the same language with it?
Eliot says that in order to establish initial contact, one could try to agree on a naming convention for phenomena familiar to both civilizations.
“At the beginning of the dialogue, we can mention several phenomena that, as we know for sure, should be known to our interlocutors, and offer them as a key to subsequent communication,” he explains.
In other words, one could start by agreeing on common terms for concepts such as a star or a galaxy - or, for example, the number of astronomical bodies in a particular star system.
However, we would have to take into account the delay in the exchange of messages, since the closest star system with the planet is 10.5 light years away.
That is, at least 21 years will pass on Earth in the time it takes to send one message and receive an answer to it.
According to Vertimer, all of the most curious signals recorded so far either have not received a rational explanation (for example, fast radio pulses and the signal "Wow!"), Or were caused by natural physical phenomena, such as supernova explosions.
“Still, I'm not losing my optimism,” he says. - I think that the universe is most likely full of different life forms. It's just that earthlings are just entering the game and learning to communicate with other worlds."
"In my opinion, it will be some time before we can find out if we are alone in the universe."
One way or another, the SETI project has no shortage of work - there are more than enough space signals to be verified.
Perhaps someone is trying to contact us right now.