Is anyone up there listening? We risk waiting for 400,000 years

If there are so many galaxies, stars and planets, where are all the aliens, other intelligent life forms, and why have we never heard of them?

These are the simple questions at the heart of the Fermi Paradox, that is precisely the question why, despite all this life , we have never been able to find it in space. In a new article, a couple of researchers ask the next obvious question: How long will we have to survive to hear the voice or data of another alien civilization?

Their answer? A little long, 400,000 years. 400,000 years is a long time for a species that has only existed for two hundred thousand years and that only discovered agriculture about 12,000 years ago. But 400,000 years is the time we will need to continue this human experiment if we want to have news of alien civilizations. This is the result of the latest study on Communications with Extra Terrestrial Intelligences, CETI.

The document is “ The number of possible CETIs within our galaxy and the probability of communication between these CETIs “. The authors are Wenjie Song and He Gao, both from Beijing Normal University's Department of Astronomy. The article is published in The Astrophysical Journal.

"As the only advanced intelligent civilization on Earth, one of the most perplexing questions for humans is whether our existence is unique," say the authors.

"There have been many studies on extraterrestrial civilization in the last few decades."

Certainly there have been, even if it is difficult to study something that we are not even sure 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. However, many researchers have approached the issue as a kind of thought experiment, using strict scientific guidelines. A 2020 study, for example, concluded that there are likely 36 CETIs in the Milky Way.

How many CETIs might exist is related to how long we might have to wait to hear one. “We have always wanted to know the answers to the following questions. First, how many CETIs exist in the Milky Way? This is a challenging question. We can only learn from a single known data point (ourselves), ”the authors write.

This is where Drake's equation comes into play. This is the theoretical equation that calculates how many extra-terrestrial civilizations exist at the same time as ours. Based on our growing knowledge of the Milky Way, the Drake equation tries to estimate how many ETCs there might be in our galaxy.

The Drake equation has its flaws, as many critics have explained. For example, some of its variables are little more than guesswork, so the number of civilizations it calculates is not reliable. But Drake's equation is more of a thought experiment than a real calculation. We have to start somewhere, and that gets us started.

"Most of the studies on this problem are based on the Drake equation," the researchers write. "The obvious difficulty with this method is that it is uncertain and unpredictable to quantify the likelihood that life will appear on a suitable planet and eventually develop into an advanced communicating civilization." If you are skeptical of all of this, you are not alone. We cannot scientifically know how many other civilizations there are, or even if any exist. We are not informed enough. Studies like this are part of an ongoing conversation we have with ourselves about our plight. Each helps us think about the context of our civilization.

So how did they get to 400,000 years if we don't even know how many CETIs there might be?

The research duo are not the first to address this question. Their article outlines some of the previous scientific efforts to understand the incidence of other civilizations in the Milky Way. For example, they refer to the 2020 study which estimates there are 36 CETIs in the Milky Way.

That number came from calculations involving galactic star formation histories, metallicity distributions, and the likelihood that stars will host Earth-like planets in their habitable zones.

That document clarifies that "[The] subject of intelligent and communicative extraterrestrial civilizations will remain entirely in the domain of hypothesis until a positive detection is made."

But they also point out that scientists can still produce valuable models based on logical assumptions "which can at least produce plausible estimates of the occurrence rate of such civilizations."

This study carries on some of the same thinking. These are two parameters, both of which are little known. The first concerns how many terrestrial planets are habitable and how often life on these planets evolves into a CETI. The second is at what stage in the evolution of a host star a CETI could be born.

The researchers assigned each of these parameters a variable in their calculations. The probability of life appearing and evolving in a CETI is (fc) and the required host star evolution stage is (F).

Song and Gao ran a series of Monte Carlo simulations using different values ​​for these variables. They came up with two scenarios: an optimistic perspective and a pessimistic perspective.

The optimistic scenario used the values ​​F = 25 percent and fc = 0.1 percent. So a star must spend at least 25% of its life before a CETI can emerge. And for each terrestrial planet, there is only a 0.1% chance that a CETI will appear.

These optimistic variables create over 42,000 CETIs, which sounds like a lot, but isn't spread across the galaxy at different times. Furthermore, we would need to survive another 2,000 years to achieve two-way communication. It seems almost within reach.

But this is the 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 just need to get together.

Now for the pessimistic scenario.

In the pessimistic scenario, F = 75 percent and fc = 0.001 percent. So a star cannot host a CETI until it is much older and the probability of a single terrestrial planet hosting a CETI drops to a minuscule percentage. Where does this leave us?

This pessimistic calculation produces only about 111 CETIs in the Milky Way. Even worse, we would need to survive another 400,000 years to have two-way communication with them.

This is where the Great Filter comes into play. The Great Filter is anything that prevents matter from becoming life and then progressing to become an advanced civilization. The authors address this topic when they write:

“However, it has been proposed that the life of civilizations is most likely self-limiting, due to many potential disruptions, such as demographic problems, nuclear annihilation, sudden climate change, rogue comets, ecological changes, etc. If the Doomsday argument is correct, for some pessimistic situations, humans may not receive any signals from other CETIs prior to extinction. "

In their article, the scientists write that "the values ​​of fc and F are full of many unknowns". This is the case in all of this type of work. This article, and others addressing the same question, are seen more useful as thought experiments than solid results.

We can't know any of these things for sure, but we can't help but be forced to explore them. It is part of human nature.

"It is quite uncertain what proportion of terrestrial planets can give life to life, and the process of evolving life in a CETI and being able to send detectable signals into space is highly unpredictable," they write.

Will humanity ever meet another civilization? It is one of our most compelling questions, and it is almost certain that no one alive today will ever have an answer.

First, there must be other CETIs, so we must exist simultaneously with them and communicate in some way. It is possible that another CETI had already detected life on Earth before they were wiped out by the Great Filter or perhaps by a natural disaster such as a supernova explosion. We will never know.

Perhaps humanity will survive for a long time. Perhaps the Earth will be rendered uninhabitable and humanity will flee to Mars or elsewhere. But would a Mossian outpost on a long-dead planet populated by the muddy descendants of a ruined Earth qualify as CETI?

We like to imagine that other civilizations have successfully overcome problems we still struggle with. Could it be true? Or will the first CETI we discover be little more than the descendants of a once proud civilization that radiated confidence until the Great Filter struck?

Who knows? Should humanity ever encounter another technological species, it could be so far in the future that our descendants will be nearly unrecognizable to modern humans.

Or perhaps we will never have an answer and the Great Filter will prevent us from finding one.

But if humanity needs a goal, something to hold on to that can keep hope alive, then the dream of communicating with another CETI could.

---

---

The article Is there anyone listening up there? We risk waiting for 400 thousand years comes from ScenariEconomici.it .

---

This is a machine translation of a post published on Scenari Economici at the URL https://scenarieconomici.it/lassu-ce-qualcuno-in-ascolto-rischiamo-di-restare-in-attesa-per-400-mila-anni/ on Thu, 05 May 2022 20:52:25 +0000.