The effort known as the search for extraterrestrial intelligence (SETI) has long relied on radio telescopes to listen for transmissions from possible calling aliens. However, in an expansive galaxy like ours, how can we be sure we have tuned to the correct station?
A model simulating contact through the Milky Way suggests, perhaps unsurprisingly , that unless our galaxy is dense with long-lived intelligent species, the chances of stumbling upon a signal are low. However, the findings, which were published in 2020 in the International Journal of Astrobiology, also suggest that the likelihood of interaction might be higher the moment a new communication technology first goes online.
As well as providing fodder for imaginative scenarios, flip the switch on some new listening device and voilà, receive a transmission from E.T., the results could spur aspiring alien hunters to innovate. Research efforts dedicated to discovering and developing new methods to communicate across cosmic distances may ultimately offer greater chances of establishing contact than long programs using a single technology.
For Marcelo Lares , the investigation began with a challenge. An astronomer at the National University of Córdoba in Argentina, Lares typically works on data-rich statistical analyzes involving stellar populations, the large-scale structure of the universe, and gravitational wave events.
Thinking about aliens offers no such abundance of information. “We only have one observation, and that is that Earth is the only known planet with life,” says Lares.
Scientific speculation about life, intelligence, and otherworldly technology is often based on Drake’s equation. This mathematical framework was first drafted by astronomer Frank Drake in 1961. He estimates the number of communicating species by looking at the fraction of stars in the galaxy with planets, the percentage of those planets that develop life, and the probabilities that such living creatures do. become curious and able to make interstellar contact with other beings.
Lares and his collaborators wanted something simpler. Rather than venture guesses about the unknowns involved in the genesis of life and the development of intelligence and technology, they created a model that had essentially three parameters: the time when communicating species “wake up” and begin transmitting evidence of their presence, the range of such signals, and the lifetime of any given transmission.
The resulting arrangement places a group of nodes, or intelligent message creators, randomly throughout the Milky Way, where sometimes they transmit and other times they don’t. “It’s like a Christmas tree,” says astronomer José Funes of the Catholic University of Córdoba, one of Lares’s co-authors. “You have lights going on and off.”
The team ran more than 150,000 simulations, each with a different set of assumptions about these basic parameters, to see which scenarios favored interstellar contact. A galaxy full of self-advertising technological aliens produces many more interactions than one in which species are separated by vast distances or vast amounts of time.
These conclusions may not necessarily be shocking . “It’s just a statistical way of saying, ‘If you want to increase your chances of contact, you need a larger number [of communicators] or make them last a long time,'” says planetary scientist Ravi Kopparapu of NASA’s Goddard Space Flight Center. . , who was not involved in the work.
But Lares counters that quantifying our intuitive conceptions with mathematical models can be valuable, if only to serve as a reality check of our basic understanding. The findings set a sort of upper bound on the probability of contact under different circumstances, he adds.
In each case, the simulations showed that the probabilities of interstellar interaction are by far the greatest at just the moment in which a species “wakes up” and discovers the correct way to communicate. That result occurs because other nodes will have already connected and presumably found each other, essentially creating a large branch of “lit” Christmas tree lights and increasing the chances of stumbling upon this transmission network. But if the lights blink out of sync with each other or at vastly different times, a situation that is analogous to using the wrong contact technology or being apart for long periods of time, the intelligent species may never find each other.
After SETI’s historically preferred contact technology, radio waves, became available in the early 20th century, some discoveries were even initially thought to be extraterrestrial transmissions. And in the 1960s, British astronomers Jocelyn Bell Burnell and Antony Hewish originally named the first detection of a pulsar, a rapidly spinning stellar corpse, LGM-1 “little green men” because the source’s pulses seemed too regular. to be natural.However, humanity has been slowly emitting less radio emissions over the decades as we have upgraded our technology to wired cables and fiber optics, which has lessened the chances that aliens could stumble upon our transmissions with leaks.
The study The authors see their findings as a possible answer to the Fermi paradox, which asks why we have not found evidence of intelligent extraterrestrials, given that in the long history of our galaxy, some species Technological technologies could have emerged and sent messages of their existence through space by now. The work suggests that this absence is not very significant, perhaps E.T. is it too far from us in space and time or is it just using a calling card we don’t know about.
At the heart of the research is also an attempt to move away from some of the self-focused aspects human. biases that tend to plague speculation about other strangers. “It is very difficult to imagine extraterrestrial communication without our anthropomorphic way of thinking,” says Funes. “We need to make an effort to get out of ourselves.”
Kopparapu agrees with this assessment. “Unexpected discoveries come from unexpected sources,” he says. “In our common knowledge thinking, we are in a box. It’s hard for us to accept that there could be something else outside of it.”
SETI’s focus on radio waves developed under unique circumstances during a small portion of human history. Although the company has at times tried other means of discovering intelligent aliens, such as looking for high-powered laser beams or evidence of massive artificial structures surrounding stars called Dyson spheres, any search apparently remains as limited by human imagination as it is. by fundamental physics.
However, seeking something as potentially fantastic as another cosmic culture requires the convergence of many disciplines, including physics, biology and even philosophy, Lares says. The effort to consider more creative messages, such as those emitted by neutrinos, gravitational waves or phenomena that science has not yet discovered, can help to break down our parochial conceptions and give us a more complete understanding of ourselves.
Despite the low chance of contact, Lares is hopeful that one day the problem will be worth attacking in many ways. “I think a SETI search is a high-stakes gamble,” he says. “The probability of success is really very low. But the prize is really too high.”
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