Two
researchers have revised the Drake equation, a mathematical formula for the
probability of finding life or advanced civilizations in the universe. Credit: University of Rochester.
Are humans
unique and alone in the vast universe? This question--summed up in the famous
Drake equation--has for a half-century been one of the most intractable and
uncertain in science.
But a new paper
shows that the recent discoveries of exoplanets combined with a broader
approach to the question makes it possible to assign a new empirically valid
probability to whether any other advanced technological civilizations have ever
existed.
And it shows
that unless the odds of advanced life evolving on a habitable planet are
astonishingly low, then human kind is not the universe’s first technological,
or advanced, civilization.
The paper, published in Astrobiology, also shows for the first time just what “pessimism” or “optimism” mean
when it comes to estimating the likelihood of advanced extraterrestrial life.
“The question of
whether advanced civilizations exist elsewhere in the universe has always been
vexed with three large uncertainties in the Drake equation,” said Adam Frank,
professor of physics and astronomy at the University of Rochester and co-author
of the paper. “We’ve known for a long time approximately how many stars exist.
We didn’t know how many of those stars had planets that could potentially
harbor life, how often life might evolve and lead to intelligent beings, and
how long any civilizations might last before becoming extinct.”
“Of course, we
have no idea how likely it is that an intelligent technological species will
evolve on a given habitable planet,” says Frank. But using our method we can
tell exactly how low that probability would have to be for us to be the ONLY
civilization the Universe has produced. We call that the pessimism line. If the
actual probability is greater than the pessimism line, then a technological
species and civilization has likely happened before.”
Using this
approach, Frank and Sullivan calculate how unlikely advanced life must be if
there has never been another example among the universe’s ten billion trillion
stars, or even among our own Milky Way galaxy’s hundred billion.
source for further reading: https://exoplanets.nasa.gov/news/1350/are-we-alone-in-the-universe-revisiting-the-drake-equation/
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