Scientists have claimed that if we ever find a sign of an advanced alien civilization, it is likely that these aliens are already dead. There are believed to be 20 to 40 billion terrestrial worlds in the Milky Way with habitable conditions.
However, we cannot yet estimate how many of these could have generated life, nor whether they were long enough to retain liquid water and evolve.
Humanity has only covered 0.001% of the Milky Way with signs in 80 years. Even at the upper limit of life for our civilization, we will not have covered the entire galaxy.
But if any civilization sent a signal and lasted less than 100,000 years - the width of the galaxy in light years - then the chances of finding a living civilization are incredibly small.
"If the emitting civilization on the other side of the galaxy, when its signal reaches here, civilization has probably ended," said Claudio Grimaldi of the Federal Polytechnic School of Lausanne in Switzerland.
They note that when a civilization stops emitting, its signals will continue to travel through space, in a kind of echo of dead civilization. And it may be possible to detect these signs, but the odds are not necessarily good to find someone alive.
"The transmissions that reach Earth may come from distant, extinct civilizations, while civilizations are still alive are sending signals to arrive," they write.
Still, the big factor here is that we just don't know how likely life is to reach the planet. There are plenty of potentially habitable worlds within 80 light years of Earth, close enough to have received a signal from our planet
Is intelligent life on our planet a fluke, or is it widespread? Until we answer that question, it is still difficult to draw conclusions. [ IFLS ]