The Drake Equation originated in 1961 as an exercise to consider how many possible intelligent societies exist with the ability to communicate with us. It’s not so much an exact formula as a thought experiment — as we shall see many of the parameters are wild guesses, so just about any value is possible. Here’s Drake’s equation:
N = R* ∙ fp ∙ ne ∙ fl ∙ fi ∙ fc ∙ L
- R* — The average rate of star formation.
- fp — Fraction of those stars which have planets.
- ne — Average number of planets which can support life (per star).
- fl — Fraction of ne which actually develop life.
- fi — Fraction of fl which actually develop intelligent life.
- fc — Fraction fi which communicate outside their planet into space.
- L — Length of time signals estimate from planet (or the time a society lives).
Current Values
According to the SETI League, Drake’s current estimates provide N=10,000 — a very large number which accounts for SETI’s ambitious attempts to find other life near us. But it’s obvious the actual number is a huge approximation — so much so the actual number N is meaningless (In fact, how you perceive N can reveal bias in critical thinking, but that’s a topic for another time).
Problems
Most of the parameters are wild guesses, so let’s simplify a bit with the star and planet parameters to get the following simplified version:
N = L/1000
Where “L” is the length of time a civilization exists. Let’s assume all the other parameters are known (and agreed upon) entities — what parameter do we put in for L? If you’re optimistic, a civilization could last a long time. But if you’re pessimistic, civilizations destroy themselves rather quickly. Since we have no concrete data on L, it’s a wild guess (and thus, so is N by extension).
But it’s not so much the value for N which is interesting, but Drake’s current estimate of 10,000. The question becomes why can’t we find any evidence for life anywhere else but earth? Forget communicating with any of the existing 10,000 other societies, why can’t we find any evidence of life, anywhere, anytime?
Why have we found nothing? We’ve stumbled into the Fermi Paradox which will be the subject of a future article, as well as how all this relates to the Bible, Christians and Evolution. The Drake equation itself isn’t very interesting (other than as a thought experiment) due to it’s huge approximation, but the problems and areas it leads to are — it’s an important concept leading to scientific and theological issues which we’ll discuss next time.
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