The authors dub their result the "archaelogical form" of the Drake equation. Their equation multiplies the terms "Nast" and "fbt" to get the result. "Nast" refers to the "number of habitable planets in a given volume of the universe," and "fbt" is the "likelihood of a technological species arising on one of these planets."
The researchers say one in 10 billion trillion seems a very low probability that humanity is alone out there. But the vast distances of the universe, coupled with the uncertainty of how long civilizations exist, mean it may never be possible to communicate with anyone out there.
How Many Intelligent Aliens are Out There?
Our civilization is 10,000 years old; unless a typical civilization lasts much longer, over the 13-billion-year lifespan of the universe it's likely the others have gone extinct, the researchers added. But there is a practical application to keep us around longer, the researchers said.
"Our results imply that our evolution has not been unique and has probably happened many times before," Frank said. "The other cases are likely to include many energy-intensive civilizations dealing with their feedback onto their planets as their civilizations grow. That means we can begin exploring the problem using simulations to get a sense of what leads to long lived civilizations and what doesn't."