In 1961 just a few days before a meeting of scientists interested in the search for ET, pioneering astronomer Frank Drake came up with a powerful provocation: an equation to estimate the number of worlds likely to harbor extraterrestrial civilizations; over at National Geographic, his science writer daughter Nadia looks at her dad's impact.
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.