January 1, 2019 | David F. Coppedge

Time to Ditch the Drake Equation

Frank Drake’s equation for the probability of space aliens is chopped-up ignorance mushed into pseudo-scientific sausage.

Paul Sutter has a way with words. In a Space.com article entitled “Alien Hunters, Stop Using the Drake Equation,” he says, “The Drake equation is simply a way of chopping up our ignorance, stuffing it into a mathematical meat grinder and making a sausage-guess.” What is the Drake equation, you ask?

For the precocious hunter of off-Earth life, the Drake equation is the ever-ready, go-to toolkit for estimating just how (not) lonely humans are in the Milky Way galaxy. The equation was developed by astronomer Frank Drake in 1961 in a slight hurry so that attendees of an upcoming conference would have something to confer about, and it breaks down the daunting question “Are we alone?” into more manageable, bite-size chunks.

What Is the Drake Equation?

The SETI Institute portrays the Drake Equation with vivid colors and graphics, followed by a definition of its seven factors:

Drake Equation (SETI Institute)

  • N = The number of civilizations in the Milky Way Galaxy whose electromagnetic emissions are detectable.
  • R* = The rate of formation of stars suitable for the development of intelligent life.
  • fp = The fraction of those stars with planetary systems.
  • ne = The number of planets, per solar system, with an environment suitable for life.
  • fl = The fraction of suitable planets on which life actually appears.
  • fi = The fraction of life bearing planets on which intelligent life emerges.
  • fc = The fraction of civilizations that develop a technology that releases detectable signs of their existence into space.
  • L = The length of time such civilizations release detectable signals into space.

“The Drake equation is simply a way of chopping up our ignorance, stuffing it into a mathematical meat grinder and making a sausage-guess.” —Paul Sutter, astrophysicist

No Scientific Value

An equation needs certainty, Sutter argues. Without some grasp on precision with the factors in the equation, it becomes useless, no better than a wild guess. The equations of physics deal with measurable factors that can be ascertained often to many decimal points of precision. How do you specify the uncertainty in some of Drake’s factors?

The equation starts with some straightforward concepts, such as the rate of star formation and the fraction of stars hosting planets. But it quickly moves into tricky terrain, asking for numbers like what fraction of those planets that could host life actually end up evolving intelligent species and what fraction of those planets blast out friendly signals into the cosmos, inviting us Earthlings to a nice little chat.

Frank Drake with his famous equation (SETI Institute)

Because the right side of the equation is a series of factors multiplied together, any one factor that is unknown with at least some empirical range of error renders the entire calculation of N (number of alien civilizations) worthless. It becomes the weak link that breaks the chain.

You may think you’re making good progress on nailing down this prediction, but as long as a single parameter still has unknown uncertainty, you haven’t made any progress.

That single unknown can undo the hard work poured into the entirety of the rest of the equation. Until you know all of it, you know none of it.

Beyond those issues, there are other reasons the Drake Equation fails as a guide to knowledge:

The Drake equation is simply a way of chopping up our ignorance, stuffing it into a mathematical meat grinder and making a sausage-guess. It doesn’t have any predictive power greater than randomly pulling a number out of a hat. What if you didn’t accurately estimate one of your uncertainties? The answer isn’t reliable. What if you missed a parameter, some crucial element in the steps from stars to sentience? The answer isn’t reliable. What if you had too many parameters, introducing an element that turned out not to matter? The answer isn’t reliable.

No Philosophical Value

The Drake Equation fails as a scientific tool for making predictions, Sutter argues. But maybe it offers something for philosophers. Maybe it’s a conversation starter that can direct the attention of scientists and the public toward useful scientific discussions. Maybe it has value for chopping up a big problem (the number of alien civilizations) into smaller chunks. Nope, he says; it fails on that count, too. It actually makes our discussions harmful, by misdirecting our attention to a pseudo-scientific equation offering an assumption of knowledge it cannot provide.

There’s a risk we will spend more time unhelpfully discussing the parameters of the model and less time gainfully trying to go out there and actually search for life. Debating over the particular value of, say, the number of life-bearing planets that will give rise to intelligence (a number which must be 100 percent made up) will not give us a clearer picture of the chances of chatting with another intelligent species — instead, we just end up clouding our perspective through an intrinsically warped formulation.

Sutter finds more value in actually going out and looking for evidence than in engaging in armchair analyses of our ignorance. Because the Drake Equation creates a false sense of knowledge and precision, it’s an obstacle. “Prediction is what makes an idea useful,” he ends. “And if an idea isn’t useful, why keep it around?”

Talk about fake science and pseudo-science! Many of the world’s astronomers who are SETI enthusiasts have used this gimmicky tool, with its false image of mathematical rigor, without critical thinking. For 57 years, this visualization ploy, proudly displayed by Drake’s friend Carl Sagan and still promoted on the SETI Institute website, has buffaloed the public into perceiving SETI as a scientific research project. In effect, the Drake Equation is very useful – as propaganda.

Exercise: Search the internet for “Drake Equation” and look at all the images of it. Ponder how many students and adults are being fooled by this visual propaganda tool.






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  • Buho says:

    I find the Drake Equation to be very precise! For parameter fl, the fraction of planets that develop life, the probability for abiogenesis has been calculated to be less than 1 in 10^100. Even granting the most generous estimates for the other parameters, because they all multiply together, the result N is 0: zero civilizations in our galaxy that we can communicate with. Easy! 🙂

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