Astronomers say that the new way of counting the number of advanced alien cultures suggests that we are not alone, but that we will never be able to meet anyone.
Copernicus' principle is the idea that the Earth is not at the center of the universe and is not special. When Nicolaus Copernicus first stated this in the 16th century, it led to a whole new way of looking at our planet.
Since then, scientists have begun to use the principle more broadly and have suggested that humans have no special privileges in the universe. We are just ordinary observers sitting on an ordinary planet in an ordinary part of an ordinary galaxy.
This form of thinking has had serious consequences. This led Copernicus to the idea that the earth revolves around the sun, and Einstein to the general theory of relativity. And she regularly guides the thinking of physicists, astronomers and cosmologists about the nature of the universe.
Now Tom Westby and Christopher Conselis of the University of Nottingham in the UK have used the Copernican principle to take a fresh look at the existence of extraterrestrial civilizations. They believe that the principle implies the absence of special conditions on Earth that would allow intelligent life to evolve. Therefore, wherever these conditions exist, intelligent life is likely to develop on about the same time scale as here.
The Copernican Astrobiological Principle is of great importance for astronomers to be able to estimate the number of extraterrestrial civilizations that can communicate with us. In fact, Westby and Conselis have reduced the numbers and say that given the strictest limits they can place on numbers, there are probably about 36 civilizations with this capability right now. But the numbers come with a significant caveat that also sheds light on the Fermi paradox, which is famous for the assumption that if intelligent aliens existed, we should surely have seen them already.
A bit of background. Back in 1961, American astrophysicist Frank Drake wrote down an equation that estimates the number of interacting extraterrestrial civilizations in our galaxy.
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Drake's equation
Drake's equation starts by estimating the number of stars in the galaxy and then calculates the proportion of planets in the habitable zone. He then evaluates the fraction at which life develops, and then those at which life becomes intelligent and able to communicate.
Astrophysicist Frank Drake.
The last expression is the length of time during which this civilization transmits signals that we might detect. The result is the number of civilizations with which we could communicate today.
The formula looks like this:
Where:
Over the years, astrophysicists have interpreted these numbers in different ways, revising their estimates as new ideas and observational data emerge. And over the past few years, there has been a lot of new observational data that can confirm some of the numbers.
In particular, astronomers confirmed the existence of exoplanets and began to understand how common they are in habitable zones throughout the galaxy. And that gives some hard numbers to start solving the Drake equation. Westby and Consilis have duly updated the equation with the latest data.
But they also made significant progress using the Copernican astrobiological principle. This is the idea that if a planet is in the habitable zone of a system that is rich in the heavier elements necessary for life, then intelligent life will arise in the interval from 4.5 to 5.5 billion years.
Here is a diagram of the planetary system near the star GJ 357. The planet is orbiting inside the habitable zone and can have liquid water. Scientists now need to confirm that the GJ 357 d has an atmospheric layer.
It is justified by the fact that intelligent life arose on Earth more than 5 billion years ago, and there is nothing special in our corner of the Universe. Thus, the same thing will happen over the same period of time in other similar places.
However, this is a much stricter assumption than the imagination of life, which could emerge any time after the planet is 5 billion years old (many stars are 10 billion years old). This is why researchers call it a strong condition.
When astronomers put these numbers into the Drake equation, the number of civilizations becomes huge. But there is another limiting factor - the length of time these civilizations communicate - centuries, millennia, or even longer. Obviously, the longer they can communicate, the more likely it is that we intersect with them.
However, Westby and Conselis are betting 100 years. “We know that our civilization already had radio communications,” they say. So this is the bottom line on which they base their calculations.
And the results make for a more interesting reading. “In strong conditions, we found that there should be at least 36 civilizations in our galaxy,” Westby and Conselis say, although their number may be as high as 211 or only four.
Galaxy Cluster Abell 1703.
This may sound like a significant number, but there is plenty of room in the galaxy. According to the researchers, if they were evenly spread throughout the galaxy, these civilizations would be at a great distance from each other. “The nearest ones would be at the maximum distance specified in 17,000 light years, which would make it impossible to communicate or even detect these systems with existing technology,” they say.
Fermi paradox
And this negates the Fermi paradox, which is sometimes used to suggest that we should be alone in the universe. The point is not that there are no intelligent civilizations there, but that they are so thinly distributed throughout the galaxy that we cannot detect them.
Enrico Fermi.
As Douglas Adams pointed out, the cosmos is great. And the amount we looked for signs of intelligent life is extremely small. Westby and Conselis point to calculations that the search volume is equivalent to only 7,700 liters of Earth's oceans.
Of course, researchers are well aware of the limitations of their arguments. They recognize the well-known warning against drawing any conclusions from a single sample. But this does not prevent them from speculating.
The researchers also come to other interesting findings. They point out that if they assume that primitive life arises where conditions pass long enough, then the universe must be rife with it. "Such generous assumptions lead to the estimated number of habitats for primitive life in the Milky Way, which reaches tens of billions," they say.
The only question now is how soon we will see the evidence.
