How can we calculate the likelihood of technological civilizations having existed on other planets? That’s a question Adam Frank, a professor of astronomy, considers in an essay, “Yes, There Have Been Aliens,” published in the New York Times. The author of three books and a national commentator on matters of astronomy and science, Frank outlines research that he and colleague Woodruff Sullivan published in the journal Astrobiology indicating that the overwhelming probability is that many other civilizations have existed during the 13-plus billion years of the universe’s existence.
Franks explains that scientists discuss the probability of life on other planets in term of the Drake equation, developed in the early 1960s by astronomer Frank Drake. The odds of extraterrestrial life, according to Drake, are based on several factors, including how many stars are born each year and how many of those stars have planets orbiting them.
Frank thinks NASA’s Kepler mission has given scientists the confidence to address a key factor in Drake’s equation.
Last month astronomers from the Kepler spacecraft team announced the discovery of 1,284 new planets, all orbiting stars outside our solar system. The total number of such “exoplanets” confirmed via Kepler and other methods now stands at more than 3,000.
As Frank points out, Drake’s equation is not a case of universal law, but, instead, “a mechanism for fostering organized discussion.”
That’s why discussions of extraterrestrial civilizations, no matter how learned, have historically boiled down to mere expressions of hope or pessimism.
With the knowledge provided by Kepler, Frank argues that the odds are high that there have been technological civilizations in the universe before ours.
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.
But Frank expects there to be a long wait before anyone can conclude whether any other civilizations currently exist.
Astrophysicist Adam Frank
A self-described “evangelist of science,” Frank regularly writes and speaks about subjects like intelligent life forms in the universe, high-energy-density physics, space exploration and missions, climate change, and more.
