On Earth, civilizations are short-lived. The Roman Empire lasted less than a thousand years, and the Mayan civilization – about two millennia. And the more developed a civilization is, the less it exists. How much is ours left? With such irresponsibility and the rate of consumption, one must think, not for long.
The same can happen on other planets. And, most likely, this is what happens. Their short life may explain why we still haven’t detected a single signal from alien intelligence.
It is estimated that several dozen worlds with civilizations advanced enough to send messages into space should exist in the Milky Way galaxy. But these worlds are probably so remote that the signals of their inhabitants do not reach the Earth or fly through space for thousands of years.
By the time the signal is received, that distant planet will no longer be the civilization that sent it. Or there will be no us. “We can imagine a galaxy with intelligent life, but communication is unlikely,” say Tom Westby and Christopher Conselis.
The analysis by Westby and Konselice of the University of Nottingham in England is based on a slightly modified Drake equation, proposed almost 60 years ago. Frank Drake identified factors that, in principle, allow us to estimate how many intelligent civilizations can exist in the galaxy.
Westby and Conselis began with the assumption that intelligent and technologically advanced life would take 5 billion years on the planet, just like on Earth. Then it remains to figure out how many stars are old enough and how many planets are in their Goldilocks zones.
Thus, in their new CETI equation, Westby and Conselis showed that the number of intelligent civilizations depends on how many stars are in the galaxy and how many of them are more than 5 billion years old.
It turned out that some factors do not limit the prospects for detecting alien life. For example, almost all stars in our galaxy are older than 5 billion years, and their average age is almost 10 billion years.
Some stars should be excluded due to lack of essential elements. Of the remaining stars, probably only 20 percent have planets in the Goldilocks zone.
Since there are more than 200 billion stars in the galaxy, therefore, there must be billions of potentially populated worlds. But before claiming this, there is one more important exception to be made.
It is safe to say that a civilization capable of sending signals can survive for 100 years. On earth, radio waves were discovered in 1865 by the Scottish physicist James Clerk Maxwell. They learned to use them in 1895, when the Russian physicist Alexander Popov created the first radio transmitter.
With this set of assumptions, taking into account that the average lifespan of a developed civilization is 100 years, today there should be only 36 sufficiently developed civilizations in our galaxy.
Our nearest neighbor is likely to be about 17,000 light-years away, “making it impossible for today’s technology to communicate or even detect these solar systems,” Westby and Conselis write. In the most optimistic case, the nearest civilization should be within 300 light years from us.
“The lifespan of civilizations in our galaxy is unknown, and this is by far the most important factor in the CETI equation,” Westby and Conselis note.