Science There Could Be 42,777 Intelligent Alien Civilizations In Our Galaxy Say Scientists Jamie Carter Senior Contributor Opinions expressed by Forbes Contributors are their own. I inspire people to go stargazing, watch the Moon, enjoy the night sky May 30, 2022, 08:00pm EDT | Share to Facebook Share to Twitter Share to Linkedin The artists concept depicts Kepler-186f, the first validated Earth-size planet to orbit a distant . . . [+] star in the habitable zone. The size of Kepler-186f is known to be less than ten percent larger than Earth, but its mass, composition and density are not known. Kepler-186f orbits its star once every 130 days and receives one-third the energy that Earth does from the sun, placing it near the outer edge of the habitable zone. Kepler-186f resides in the Kepler-186 system about 500 light-years from Earth in the constellation Cygnus. The system is also home to four inner planets, seen lined up in orbit around a host star that is half the size and mass of the sun. The discovery of Kepler-186f confirms that Earth-size planets exist in the habitable zones of other stars and signals a significant step closer to finding a world similar to Earth. getty How many extraterrestrial intelligent civilizations are out there and when will one of them send us a message? The answers, according to a paper published in The Astrophysical Journal are 42,777 and sometime in the next 2,000 years. It’s a decent explanation for the Fermi Paradox , which asks why we still haven’t received any messages from other civilizations despite there being a high probability of them existing. It estimates the number of possible CETIs—communicating extraterrestrial intelligent civilizations—within our Milky Way galaxy. It also looks at how probable it is that one of them could contact us and when. There are, of course, some huge unknowns behind these seemingly very precise estimates that if known would make a massive difference to the results: The probability of life appearing on rocky planets and eventually evolving into a civilization advanced enough to contact another. At what stage of their host star’s evolution such advanced civilizations would be born. So the figure of 42,777—which has an error rate of a few hundred each side—is on the optimistic side. It’s based on an estimate that only 0. 1% of civilizations could become advanced enough to contact another. This is where the Great Filter comes in. MORE FOR YOU New Research Finds A Connection Between Domestic Violence And These Two Personality Disorders This Scientist Helps Andean Forests And Ecuador’s Women In STEM Exceptional Fossil Preservation Suggests That Discovering Dinosaur DNA May Not Be Impossible MORE FROM FORBES In Photos: The 'Alien Door' On Mars Is Just One Of Some Spectacular New Images From The Red Planet By Jamie Carter It also takes into account the idea that any civilization would need to survive for about three million years, give or take, to reach that point. Even if a message is ever sent to us from an advanced civilization elsewhere in the Milky Way the question remains as to whether humans can survive long enough to receive it. The authors suggest that we will need to wait as little as 2,000 years to receive one alien signal. That’s the optimistic calculations. The authors’ pessimistic estimates are for just 0. 001% of civilizations–about 111—to become advanced enough to contact another. The upshot of that would be that humans would need to wait for 400,000 years to receive a message. “The minimum value (0. 001%) we take may also be overestimated,” write the authors, Wenjie Song and He Gao at Beijing Normal University’s Department of Astronomy. “If so, the number of CETIs would become even lower, and the opportunities for communication between CETIs would become extremely small. ” The only message ever received on Earth that could have come from an extraterrestrial intelligence is the Wow! Signal, which was received in 1977 at the Big Ear radio telescope, Ohio. It was heard for 72 seconds—the maximum possible at the time—and was never repeated. MORE FROM FORBES Humans Are More Likely To Attack An Extraterrestrial Civilization Than The Other Way Around Says Scientist By Jamie Carter The source of that signal remains unknown though a recent paper found only one Sun-like star (called 2MASS 19281982- 2640123) in a sample of 66 in the region of the night sky that Wow! came from. It’s 18,000 light-years away. In 2012 a paper estimated that the closest civilization to the solar system could be 1,933 light years away. So let’s send a reply? Sure—and why not, considering the chances of an advanced alien civilization being malicious are really low —though there is one problem. Any radio or laser transmission will travel at the speed of light, so would take 1,800 years to get there. The authors note that astronomers did send the “Arecibo message” to the Great Hercules Globular Cluster (M13) in 1974 using the now collapse Arecibo radio telescope. However, it wasn’t much good. “If there are indeed CETIs in M13, their detection ability needs to be 21 orders of magnitude higher than ours to detect our signal,” write the authors. “Conversely, if they transmit a similar signal, we need to improve the detection ability by 21 orders of magnitude to detect it. ” Space is big—really big—and even in-galaxy messaging is completely impractical. Even if we’re not alone it’s doubtful we’ll ever find out. But that doesn’t stop us looking for Earth-like exoplanets around 2MASS 19281982- 2640123. Wishing you clear skies and wide eyes. Follow me on Twitter or LinkedIn . Check out my website or some of my other work here . Jamie Carter Editorial Standards Print Reprints & Permissions.