For centuries, humans have looked to the stars and asked, “Are we alone?” We might be now, but astrophysicist Adam Frank says that wasn’t always the case.
In an op-ed for the New York Times, the professor at the University of Rochester said a trillion extraterrestrial civilizations have potentially existed over the course of cosmic history — and that’s a pessimistic estimate.
His theory derives from an equation by Frank Drake in 1961. The Drake equation was meant to determine how many potential civilizations existed on other planets, but back then there was not enough information to solve it. Now, we have access to some of the necessary data.
The equation looks like this: N = R* ᐧ fp ᐧ ne ᐧ fl ᐧ fi ᐧ fc ᐧ L
And here’s what all those letters mean:
- N is the number of extraterrestrial civilizations in our galaxy that we might be able to communicate with
- R* is the average rate at which stars are born in our galaxy
- fp is the fraction of those stars that have planets
- ne is the number of those planets that can support life
- fl is the fraction of those planets where life appears
- fi is the fraction of life-bearing planets where intelligent life appears
- fc is the fraction of intelligent civilizations that emit signals of their existence into space
- L is the length of time that these civilizations send out signals.
After the Kepler spacecraft discovered an extraordinary 1,284 new planets last month, the number of confirmed exoplanets rose to over 3,000. Twenty-one of them have the potential ability to sustain life, according to NASA.
Frank, along with astronomer Woodruff Sullivan, were able to fill in parts of the equation using this new knowledge about stars and planets that exist outside of our solar system. They published their findings in a report for the journal Astrobiology in May.
Astrophysicist Adam Frank. (Photo: Brandon Vick/University of Rochester)
“What our calculation revealed is that even if this probability is assumed to be extremely low, the odds that we are not the first technological civilization are actually high,” Frank wrote in the New York Times.
“Specifically, unless the probability for evolving a civilization on a habitable-zone planet is less than one in 10 billion trillion, then we are not the first.”
Frank explained that even knowing just three out of the seven factors in the equation is enough to prove their theory.
“Given what we now know about the number and orbital positions of the galaxy’s planets, the degree of pessimism required to doubt the existence, at some point in time, of an advanced extraterrestrial civilization borers on the irrational,” he said.
Don’t get too worried about an alien encounter, though — Frank said that it will be a long time before we have the relevant data necessary to confirm whether or not extraterrestrial life currently exists.
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