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The universe must either be teeming with life or host almost no life at all, according to a new study that revises the Drake equation using probabilistic logic.
A common axiom The search for extraterrestrial intelligence If we (SETI) detect technologically advanced aliens, there will likely be numerous examples. Alien Life instead of there being only two cases (us and the new discovery).
In a new paper, astronomers David Kipping of Columbia University in New York and Geraint Lewis of the University of Sydney explain how this logic works, based on a probability distribution first proposed by biologist and mathematician JBS Haldane in 1932. Let’s imagine a group Earth-like exoplanetsall have similar characteristics. Given their small differences, we would expect them to occur in all or none of life; there is no obvious reason why half of these nearly identical ones would occur planets For example, some of them support life, while others do not.
We can then plot the various outcomes on a U-shaped graph, with probability on the y-axis and the fraction of planets with life on the x-axis. The two ends of the U-shape correspond to no or very few planets with life and many planets with life. The valley of the U-shape, corresponding to a low probability, represents half of the planets with life.
Relating to: Drake Equation: Estimating the probability of finding ET
Now Kipping and Lewis famously repeated Haldane’s logic Drake equationDeveloped by Astronomer Frank Drake before the first SETI conference, Green Bank Observatory In 1961, as a way to provide an agenda for the workshop, the Drake equation later took on a life of its own and was used to estimate the number of technological life forms on Earth. Milky Way Galaxy.
The Drake equation is written as N = R* x fp x ne x fl x fi x fc x L, where N is the number of civilizations, R* is the star formation rate, fp is the fraction of stars with planets, ne is the number of potentially habitable planets, fl is the fraction of potentially habitable planets that develop life, fi is the fraction of “intelligent” life, fc is the fraction of life that can communicate, and L is the average lifespan of civilizations.
Astronomers know the rate of star formation (less than 10 percent). Solar masses (per year in our galaxy) and the rate of stars with planets (nearly every star has a planet) is very good. The number of potentially habitable planets is less well known, but astronomers are learning more about them every day as they conduct research extraplanetary atmospheres with James Webb Space Telescope and characterizes these worlds. The values of the other four terms remain a complete mystery, making any attempt to use the Drake equation unsatisfactory because most of it is guesswork.
But Kipping and Lewis note that the first six terms in the Drake equation describe the “birth” of what they call extraterrestrial technological instantiations, or ETIs. They refer to technological alien life in this way, and they cleverly skip over terms like “civilizations,” “species,” and “intelligence,” terms that are not only problematic (for example, how do we define intelligence?) but can also be inaccurate in describing alien life. Meanwhile, the final term, L, relates to the “death” or otherwise disappearance of the ETI.
Separating the terms of the Drake equation in this way allowed Kipping and Lewis to simplify the formula: the time-averaged number of ETIs in the galaxy is equal to the birth rate of ETIs multiplied by the death rate.
“The beauty of our approach is that it’s completely general,” Kipping told Space.com, meaning we don’t have to worry about terms of the Drake equation that we don’t know.
“We are not assuming any particular mechanism or route of birth,” Kipping added. “Births can occur through spontaneous generation or panspermia “Seeding, empire-building, whatever you want — there’s simply a birth rate.”
Kipping and Lewis assume something they call the Drake equation, a steady-state equilibrium in which birth and death rates are roughly equal, and which is inevitably reached after enough time has passed. The two astronomers then connect this back to Haldane’s prior (a “prior” is the name for a type of probability distribution, such as a U-shaped curve) via a property called the occupancy fraction, F. In the exoplanet example mentioned earlier in this article, a high F value—close to 1—means that every planet has life, and a low value—close to or equal to 0—means that none of the planets have life.
The problem SETI scientists face is that, based on observations so far, F is probably not close to 1; otherwise, assuming intelligent aliens are capable of spreading throughout the galaxy and building massive structures, we would have realized by now that we are not alone. Dyson swarm and by sending out radio signals. This means that if we are not truly alone in the universe, the invasion rate must be closer to 0.5, which puts it in that unlikely valley of the U-shaped curve. Based on this U-shape, it is likely that we are relatively alone – technological life is rare elsewhere in the universe.
“These are examples of life that became apparent primarily through the signals they produced and then through their colonization, which could be seen through megastructures,” Lewis told Space.com. “If such an ETI had emerged in the lifetime of the Milky Way, then in 10 million to 100 million years they could have colonized the entire galaxy, and even after they fell, their remnants would have been around for a long time. The fact that we don’t see anything there means that if they did exist, they disappeared long ago and their signatures have decayed, and we’re back to our original premise — ETIs appear to be rare in time and space.”
Relating to: The search for alien life
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Still, Kipping and Lewis are not advocating giving up on SETI. Ignoring the lack of evidence for a moment, the steady-state Drake equation is a crowded field universe is as likely as a universe where we are alone. For a crowded universe, the invasion rate should be close to 1, and perhaps this is still possible under certain conditions. Perhaps the ETI stays in its own region and ours solar system It’s just that it’s in a region where no one has yet spread. That means the aliens are quite far away, and our strategy of looking for them around nearby stars is flawed. These settlements may be more clearly detectable in other galaxies. “I would definitely advocate extragalactic SETI,” Kipping said.
Or maybe Interstellar travel and megastructures are too difficult to build, or perhaps are undesirable by a more frugal, less colonial ETI. And in the absence of a radio or optical signal detection, SETI has not had the resources to be particularly comprehensive in its search so far, and we I could easily have missed a signal.
It is also possible that complex life is abundant, but that the development of technological life is rare.
There is also the possibility that the birth and death rates of the ETI have not ultimately reached a steady state, meaning there will still be time for new ETIs to emerge on the scene and increase their invasion rate. However, given the age of the universe and the limited lifespan of an ETI, this seems unlikely.
The research is currently available as: preprintand submitted to the International Journal of Astrobiology for peer-reviewed publication.