If there are so many galaxies, stars and planets, where are all the aliens, and why haven’t we heard from them?
Those simple questions are at the heart of the Fermi paradox. In a new paper, a pair of researchers asked the next obvious question: How long would we have to live to hear from another alien civilization?
His answer? 400,000 years.
400,000 years is a long time for a species that has only been around for a few hundred thousand years and discovered cultivation only 12,000 years ago.
But if we want to hear from an alien civilization, we will need 400,000 years to continue this human experiment. That’s according to some new research in Communicating Extraterrestrial Intelligent Civilizations (CETI).
The paper is “The number of possible CETIs within our Galaxy and the communication probability between these CETIs”. The authors are Wenjie Song and He Gao, both from the Department of Astronomy at Beijing Normal University. is published in the letter The Astrophysical Journal,
“As the only advanced intelligent civilization on Earth, one of the most puzzling questions for humans is whether our existence is unique,” the authors say.
“There have been many studies on extraterrestrial civilization over the past few decades.”
There certainly has been, even if some are difficult to study, we’re not even sure that exists. But that doesn’t stop us.
Studying other civilizations in any way is confusing because we only have one data point: humans on Earth. Nevertheless, many researchers have tackled this question as a kind of thought experiment, using rigorous scientific guidelines. For example, a 2020 study concluded that the Milky Way is likely to have 36 CETIs.
How many CETIs may exist is tied to how long we may have to wait to hear from one.
“We have always wanted to know the answers to the following questions. First, how many CETIs are present in the Milky Way? This is a challenging question. We can only learn from a known data point[of itself],” the authors write.
This is where the Drake equation comes in. Based on our increasing knowledge of the Milky Way, the Drake equation tries to estimate how many CETIs our galaxy might have.
The Drake equation has its flaws, as explained by many critics. For example, some of its variables are slightly higher than estimates, so the number of civilizations it calculates is not reliable. But the Drake equation is more of a thought experiment than an actual calculation. We have to start somewhere, and that starts us.
It also got the authors of this new study started.
“Most studies on this problem are based on the Drake equation,” write the researchers. “The obvious difficulty of this method is that it is uncertain and unpredictable to measure the likelihood that life might appear on a suitable planet and eventually develop into an advanced communication civilization.”
If you are skeptical about any of these, you are not alone. We cannot know scientifically how many other civilizations there are, or if there are any. We are not knowledgeable enough. Studies like these are part of an ongoing conversation we have with ourselves about our plight. Each helps us to think about the context of our civilization.
So how did they come to be with 400,000 years if we didn’t even know how many CETIs there could be?
The pair of researchers are not the first to tackle this question. Their paper outlines some of the previous scientific efforts to understand the events of other civilizations in the Milky Way. For example, they cite a 2020 study estimating that the Milky Way has 36 CETIs.
This number came from calculations involving galactic star formation history, metal distribution, and the likelihood of stars hosting Earth-like planets in their habitable zones.
That letter clarifies that “[T]That the topic of extraterrestrial intelligent and communicative civilizations will remain entirely in the realm of hypothesis until a positive identification is made”.
But they also point out that scientists can still produce valuable models based on logical assumptions “that can at least produce practical estimates of the incidence rates of such civilizations”.
This study takes that idea further. It deals with two parameters, both of which are poorly understood. The first concerns how many terrestrial planets are habitable and how often life develops in CETI on these planets. The second is at what stage of the evolution of the host star CETI will be born.
The researchers assigned each of these parameters a variable in their calculations. The probability that life appears and develops in CETI is (FC), and is the stage of development (F) of the required host star.
Song and Gao ran a series of Monte Carlo simulations using different values for these variables. They arrived at two scenarios: an optimistic view and a pessimistic approach.
The optimistic scenario gave F = 25 percent and . used values of FC = 0.1 percent. So a star must have at least 25 percent of its lifetime before CETI can emerge. And for each terrestrial planet, CETI has only a 0.1 percent chance of appearing.
These optimistic variables make up more than 42,000 CETIs, which sounds like a lot, but is not when spreading across the galaxy at different times. In addition, we would need to live for another 2,000 years to achieve two-way communication. It almost seems within reach.
But it is this optimistic scenario that makes the universe seem friendly and inhabited by other welcoming civilizations. Maybe some of them are already talking to each other, and we need to join in.
Now for the pessimistic scenario.
In the pessimistic scenario, F = 75 percent and FC = 0.001 percent. So a star cannot host CETI until it is very old, and the probability of a single terrestrial planet hosting CETI drops to a modest percentage. Where does this leave us?
This pessimistic calculation yields only 111 CETI in the Milky Way. Even worse, we would need to live for another 400,000 years to have two-way communication with them. (For perspective, star trek Begins in the middle of the 22nd century.)
That’s where the Great Filter comes in. The Great Filter is what prevents matter from becoming life and then proceeds to become an advanced civilization.
The authors discuss the topic as they write:
“However, it has been proposed that the lifespan of civilizations is likely to be self-limiting due to a number of potential disruptions, such as population issues, nuclear annihilation, sudden climate change, rogue comets, ecological changes, etc. If the Doomsday argument is correct, For some pessimistic conditions, humans may receive no signal from other CETIs before extinction.”
In their paper, the scientists write that “the value of FC and f are full of many unknowns.” This is the case with all works of this type. This paper, and others that tackle the same question, are seen more helpfully as thought experiments than concrete results. .
We can’t know any of this stuff for sure, but we can’t help but feel compelled to seek it out. It is part of human nature.
“It is quite uncertain whether the proportion of terrestrial planets that could give rise to life, and the process of life evolving at CETI and capable of sending detectable signals into space, is highly unpredictable.”
Will humanity ever face another civilization? This is one of our most compelling questions, and it is almost certain that no one alive today will ever have the answer.
First, there must be other CETIs, and then we have to exist together with them and communicate somehow. It is possible that another CETI may have already detected life on Earth before they were wiped out by the Great Filter or possibly by a natural disaster such as a supernova explosion. we will never know.
Perhaps humanity will live longer. Perhaps the Earth will become uninhabited, and mankind will flee to Mars or somewhere else. But would a Muscian outpost on a long-dead planet populated by the crippled descendants of the doomed Earth qualify as CETI?
We like to imagine other civilizations that have successfully conquered the problems we are still grappling with. Will it be true? Or will the first CETIs we discover be little more than the descendants of a once proud civilization who were confident until the Great Filter hit?
Who knows? If humanity ever meets another technological species, it may be so distant in the future that our descendants are almost unrecognizable to modern humans.
Or, possibly, we’ll never have an answer, and the Great Filter will prevent us from finding one.
But if humanity in need of a goal, sticking to it can keep some hope alive, then the dream of communicating with another CETI can fulfill it.
This article was originally published by Universe Today. Read the original article.