There may be 36 other intelligent civilizations in the galaxy, but odds of communicating with them are small
Bob McDonald's blog: Researchers calculate the nearest is probably 17,000 light years away
A study by researchers from the University of Nottingham in England suggests that there could be about 36 other intelligent civilizations spread throughout the Milky Way galaxy, but there are two big obstacles that are likely to prevent any communication with them: distance and time.
When you look at the numbers, you'd think the chance that there is intelligent extraterrestrial life in our galaxy seems enormous. The search for planets going around other stars by instruments like the Kepler space telescope and the Transiting Exoplanet Survey Sattellite, or TESS, have turned up more than 4,000 planets just in our cosmic backyard.
It is beginning to look like most stars have at least one planet going around them, and with up to 400 billion stars in the Milky Way, that could mean on the order of a trillion planets in our galaxy alone. And there are hundreds of billions of other galaxies spread across the universe.
However, many of the planets discovered so far are gas giants like Jupiter, as close to their stars as Mercury is to the sun, or far away, making them super cold like Pluto. What we need to find are Earth-sized planets going around sun-type stars at just the right distance so liquid water can exist on the surface.
Another study out of the University of British Columbia looked at the number of sun-like stars in the galaxy and estimated that one in five of them could have an Earth-like planet, which brings the number down to sx billion. So that's a lot of planets that could have someone interesting living on them that we might want to talk to.
The University of Nottingham team took this one step further suggesting that if we want to find something more intelligent than alien bacteria, or the equivalent of plants or simple animals, then you have to wait for intelligent life to evolve. Since it took nearly five billion years for intelligent life to evolve on Earth to the point where it had communications technology, they figured that might be a reasonable average. Then they assumed that these civilizations retained that capacity for about 100 years — again about as long as we've had it.
Taking this into account, they calculated that a mere 36 (plus or minus) intelligent, communicating civilizations might exist right now. That's a very small number to be spread out across a very large galaxy. In fact, they think it's likely these civilizations would be about 17,000 light years away from each other. That is the distance/time problem.
Our current rocket technology cannot cover even a significant fraction of a light year of distance. We are still struggling just to get people to the moon and Mars, let alone another star. Even if we had starships that could travel close to the speed of light, or if we sent a signal that travels at that speed, it would still take 17,000 years to get there, and the same amount of time for an answer to return — if they feel like answering and if they're still there. That is the time problem. Space is simply too big for easy communication as we know it across the galaxy.
The other part of the time problem implicit in this research is that intelligent life might be common over the life of our galaxy, but civilizations are unlikely to appear nearby at the same time. Of course since no one knows how long intelligent civilizations last, (given our current trajectory, some might guess not very long) it is entirely possible that other civilizations have come and gone in our galactic neighbourhood while we were still trying to figure out how to become multicellular. Others have yet to evolve. We are just missing each other in the vastness of cosmic space and time.
Of course these are sterile calculations, and we could be the beneficiaries of a cosmic accident, if it turns out by rare chance an intelligent civilization has arisen nearby and recently.
These calculations can go right into the recycling bin if the folks at the SETI Institute detect a signal from an intelligence in deep space or an alien spaceship lands in Vancouver's Stanley Park.
Then, of course, we will be faced with a communication challenge, if the aliens have no knowledge of Earthly languages (the movie Arrival looked at this problem).
In the meantime, we are faced with the reality that the only life we know for certain that exists in the galaxy is here on Earth. If those 36 other civilizations are out there, they may be essentially out of reach, which leaves us functionally alone.
The rarity of intelligent life means that we are indeed special in that we have figured out our place in the universe. Most other life on this planet is not aware of our cosmic address within the Milky Way. That seems a profound thing to contemplate.
The question now is can we survive, maintain our planet and our technology long enough to better the odds of meeting one of those alien civilizations?