In 1961, Frank Drake formulated an equation that would change the way we see ourselves in the Universe, and inspire in an unprecedented way the search for extraterrestrial intelligence. Now, more than fifty years later, his daughter, science writer Nadia Drake, looks back on the impact of her father's eponymous equation.
Drake the Younger's take on her father's influence appears over at National Geographic. It's well worth the read, as much for its narrative insights on the equation's beginnings as its uniquely personal inside perspective on Frank Drake, himself. An excerpt:
More than 50 years after it was written, the Drake equation still guides ways of thinking about how to find E.T. As the years have passed and instruments sharpened, astronomers have started to refine and fill in numbers for the equation's variables. But the variables themselves have stayed the same. My dad is repeatedly asked whether any factors are missing, he tells me, but "as far I know, they're not." He says that even when suggested missing factors seem "reasonable," they can already be found in one of the seven factors he came up with in 1961.
In the years since, though, the value of R* has changed—from an early, pre-1961 estimate of maybe one or two sunlike stars per year to as many as five or ten stars per year. This is in part because astronomers no longer count only sunlike stars. Smaller, redder, and cooler stars known as M-dwarfs have emerged in the past decade as being potential hosts for life-bearing planets.
"We have to include the M-dwarfs," Drake says. "They do have planets, and they do have them in places where the temperature is suitable for life." They're also the most common type of star in the galaxy.
The value of fp—the fraction of stars with planets—was completely unknown in 1961. "There was no data on that back then. They'd seen no planets at all outside of our solar system," says Steve Dick, astrobiology chair at the U.S. Library of Congress and former chief historian at NASA. "That meeting at Green Bank was the first meeting of its kind. It was a very daring thing to do."
Now, after many thousands of hours spent searching the skies for planets outside the solar system, and only two decades after the first exoplanets were found, we know that basically every star has planets. In other words, the value of fp is close to one. But how many of those planets are suitable for life?
Read the rest of the piece over at National Geographic. While you're at it, check out Nadia Drake's recently launch "No Place Like Home," the newest limb of NatGeo's outstanding science salon, Phenomena.