Sometimes, if you’re not getting an answer to a question that you’re asking, perhaps it can help to change the question itself? This turns out to be a new approach to the Drake equation being made by two astronomers at the University of Rochester and University of Washington, to address a shortcoming in astronomy’s famous equation that has made it impossible to draw any firm conclusions from it.
Created in 1961 by astrophysicist Dr. Frank Drake as an exercise to stimulate discussion at a SETI meeting, the Drake equation has become a useful scientific and philosophical tool to speculate on the possible number of extraterrestrial civilizations in the universe that might be using radio communications technology. While the equation makes use of known variables, such as the average rate of star formation and the number of stars that could support potentially habitable planets, one of the variables is a complete unknown: how long might these hypothetical civilizations last.
This is where astronomy professor Adam Frank and astronomer Woodruff Sullivan have changed the equation, simply by broadening the question: by leaving out the length of time these civilizations might last, one could potentially calculate the number of technological civilizations that have existed over the lifespan of the observable universe.
“Rather than asking how many civilizations may exist now, we ask ‘Are we the only technological species that has ever arisen?” says Sullivan. “This shifted focus eliminates the uncertainty of the civilization lifetime question and allows us to address what we call the ‘cosmic archaeological question’–how often in the history of the universe has life evolved to an advanced state?
“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 new approach, and also factoring in new data being gathered by astronomers researching exoplanets, Frank and Sullivan calculate that the odds of a civilization developing on a given planet would have to be as low as one in 10 billion trillion for ours to be unique in the universe. “One in 10 billion trillion is incredibly small,” explains Frank. “To me, this implies that other intelligent, technology producing species very likely have evolved before us."