Don’t let the formula above scare you. The Drake Equation is one of the most fun equations you’ll ever meet because it deals with a cool idea and serves as a starter gun to get people thinking.
Astrobiology is the study of life on other planets. Alien life! Maybe friendly little green dudes, maybe hostile xenomorphs that will tear your face off. But it’s all conjecture until you put something down on paper. That’s what the Drake Equation does--it’s a way of estimating the number of intelligent civilizations in our Milky Way galaxy (assuming you want to count us, of course.)
Dr. Frank Drake first shared his formula back in 1961, and lately it’s been getting renewed notice. But that long list of letters can be daunting, so let’s break it down into bite-sized pieces.
N is for Number. How many civilizations send out electromagnetic signals (like radio waves)? This is the number we want to arrive at.
R* is for Rate. Life needs heat from a nearby star, so how fast do star nurseries make new suns?
fp is Fraction with Planets. How many stars have planets? This number has grown a lot since the 1960s because new planets are being found every month now. For many years, we had no way of knowing if a star had any planets around it.
ne is for Number with Environment. In a given solar system with planets, how many of the planets have an environment that could sustain life? This is where you hear about the Goldilocks Zone of not too hot or too cold, but just right. In our solar system, Earth and Mars are in the Zone.
fl is Fraction and Life. How many of our Goldilocks planets actually have life on them? Remember, “life” includes stuff like bacteria.
fi is Fraction and Intelligence. Here’s where Drake culls out the bacteria and focuses on intelligent creatures. Although I’m not sure where the cut off is. Would dolphins and cats count as intelligent? Or those chimps that can do sign language?
fc is Fraction of Civilizations. Do the intelligent aliens do some activity that puts out signals we can see? Radio programs? Rocket ships? TV shows? It has to be something we can detect.
L is for Length of Time. (Maybe it should be Lt?) This factor is kind of gloomy to consider because it takes into account the idea that an otherwise intelligent civilization may destroy itself. Like if the US and USSR had a nuclear war in the 1980s. Such a catastrophic war might have driven humanity back into the Dark Ages, and we would have stopped sending up satellites or going to the Moon or sending probes into the far corners of our solar system.
Fresh science is updating these factors all the time. There is also a fair amount of room for debate within each factor. That’s a good thing. The point of Dr. Drake’s equation isn’t absolute accuracy. Rather it encourages us to think about intelligent life on other planets, and how we might go about finding it.
Check out the SETI site for a concise explanation of the formula. Also, the July 2014 National Geographic has a good article titled “The Hunt for Life Beyond Earth” by Michael D. Lemonick and Mark Thiessen. The pic of the formula is from Technology Review.