Humans may have to wait 400,000 years to make contact with alien civilizations, scientists say

In a new study published in the Astrophysical Journal, researchers at Beijing Normal University offer a bold answer: Even if there were tens of thousands of civilizations out there, they would still need to survive for thousands of years before they had a chance to talk to anyone. Optimistically, this process will take about 2,000 years. On the pessimistic side, aliens may not make contact with humans for another 400,000 years. For that matter, this rules out a Star Trek-like scenario happening anywhere in our lifetimes, even to our grandchildren.

In fact, in recent years some astronomers have been actively sending messages to nearby star systems in the hope that alien life might exist on one of these planets. These methods are dependent on the assumption that the star system not only harbours alien life, but is civilized enough to communicate with the outside world. Another question worth exploring is how many such civilisations are possible.

There could be 36 communicating alien civilizations in the galaxy?

The modern era in the search for extraterrestrial intelligence (SETI) began in 1960, when astronomer Frank Drake began the first SETI program in the radio band, Project Ozma, in 1961. In addition, Drake later came up with a formula to compute the number of communicating civilizations in the galaxy, named the Drake Equation. Nevertheless, since radio astronomy was located in its infancy at the time, naturally, the Drake equation has been criticized for its limitations to this day.

Nonetheless, the truth is that the Drake equation provides a starting point for the study of the number of communicative alien civilizations. Later scientists used this equation to estimate the likelihood of aliens, taking into account various factors over time, such as the history of star formation in a galaxy, the distribution of metal abundance, and the likelihood of planets in a star's habitable zone.

In 2020, two researchers from the University of Nottingham's School of Physics and Astronomy will estimate the number of communicating alien intelligence (CETI) civilizations within our galaxy, using the assumption that alien life develops on experience in a similar way to that on Earth.

They hypothesized that life on a planet must have formed between 4.5 billion and 5.5 billion years after the formation of its system's star, as it is done on Earth. Another assumption is that technological civilization will last at least 100 years, as we have so far. After all, it took 4.5 billion years of evolution for a technological civilization to emerge on Earth and be in a position to disclose. Finally, they calculated that there could be 36 active extraterrestrial civilizations in the Milky Way. The closest of these, a red dwarf star system at 17,000 light-years away, is too far away for detection and communication at present.

So when will we hear from the aliens?

Though the Drake equation is more of a thought experiment than an actual calculation. Nevertheless, Wenjie song and Gao He from Beijing Normal University have taken this thought experiment a step further. Their paper, "The Number of Possible CETIs in the Galaxy and the Probability of Communication Between These CETIs," explores first how many planets could host alien intelligent life in our galaxy, The second is how long would it take for life on these planets to evolve to be able to communicate? By treating these parameters as variables, they calculated the optimistic and pessimistic outlook of the scenario.

In the optimistic scenario, alien civilizations could emerge as early as 25% of a star's lifetime, and each planet has only a 0.1% chance of developing life forms into alien civilizations. In this scenario, there would be greater than 42,000 alien civilizations scattered throughout the galaxy at various stages of their evolution. In theory, only 2000 years of waiting time would be needed for two-way communication with them.

In the pessimistic scenario, where the star is older and perhaps 75% past its lifetime, there is only a 0.001% chance that an alien civilization will emerge. This would narrow the probability of extraterrestrial civilizations in the galaxy to just 111, and two-way communication with one of them would occur within the next 400,000 years.

That's twice as long as human civilization has existed on Earth, which could lead to major disruptions from climate change, undiscovered comet impacts and even nuclear annihilation. Humanoid civilization will most likely be gone long before we make contact and announce the existence of aliens. In other words, if we humans really hope to be able to make contact with aliens one day, we should be as committed to maintaining Earth's marketability for future generations as we are to find other inhabited worlds in the galaxy.

The fact that probabilistic approaches to the Fermi Paradox have been proposed in the past few years suggests that our search for extraterrestrial intelligence is still very limited and will likely remain so for a long time to come. After all, if anyone was looking for us, they'd have to be in a very small region of the galaxy to actually find some Earth signal. So the study authors acknowledge in the paper that there's a huge amount of uncertainty about their chances, and there may be a chance to communicate with aliens sooner rather than later.

However, on the other hand, huge uncertainties also have an impact, namely that there may be very rare alien civilizations. Nevertheless, who knows if they want to speak to us? Maybe the Dark Forest theory is true.