Where are all the alien civilizations?

In fact, the lack of signals from other advanced civilizations
is bad news for humanity and modern civilization. On Earth,
civilizations are short-lived. The Roman Empire lasted less
than a thousand years, and the Mayan civilization for about
two millennia. And the more developed a civilization is, the
less it exists. The same can happen on other planets. And this
is most likely what happens. Their short lives may explain
why we still haven't detected a single signal from alien
intelligence. According to experts in the Milky Way galaxy,
there should be several dozen worlds with civilizations
advanced enough to send messages into space. But these
worlds are probably so distant that the signals of their
inhabitants do not reach the Earth. By the time a signal can
be received, the distant planet ceases to be the civilization
that sent it.
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 nearly 60 years ago. Westby and Conselis began with
the assumption that intelligent and technologically advanced life
on a planet like Earth would take 5 billion years. 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 SETI 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 older than 5 billion years.
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 required
elements. Of the remaining stars, only 20% have planets in the
habitable zone. Since there are more than 200 billion stars in the
galaxy, there must therefore be billions of potentially inhabited
worlds. But before stating this, there is another important
exception to be made. It is safe to say that a civilization capable
of sending signals can live for 100 years. On Earth, radio waves
were discovered in 1865. They learned to use radio only in 1895.
With this set of assumptions, taking into account that the average
lifespan of an advanced civilization is 100 years, today there
should be only 36 advanced civilizations in our galaxy.
Our closest intelligent 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. In the most
optimistic case, the nearest civilization should be within 300 light
years of us. The lifespan of civilizations in our galaxy is unknown
and this is by far the most important factor in the equation
scientists noted.