The Drake equation was formulated in 1961 by Dr. Frank Drake, an astronomer and astrophysicist, for purposes of beginning the process of quantifying the number of civilizations that might exist in the universe.

It’s a very imprecise, back-of-the-envelope equation – I doubt he would disagree – that simply multiplies all the factors he deemed important, that would need to be in place for another civilization to come into existence and survive somewhere else in the universe.

The Drake Equation

While the Drake equation was intended to be a mathematical formula, it is less a string of numeric values than a series of scientific unknowns and vague generalities.

It reads like this: N = (R∗) (fp) (ne) (fl) (fi) (fc) (L)

where:
N = the number of civilizations in our galaxy with which communication might be possible
R∗ = the average rate of star formation in our Galaxy
fp = the fraction of those stars that have planets
ne = the average number of planets that can potentially support life per star that has planets
fl = the fraction of planets that could support life that actually develop life at some point
fi = the fraction of planets with life that actually go on to develop intelligent life (civilizations)
fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
L = the length of time for which such civilizations release detectable signals into space

Each of those variables has their own level of uncertainty and, therefore, a wide range of values. Multiplying ranges of uncertainties results in an even greater range of uncertainty, to the point where Drake’s colleagues plugged in the most widely accepted values known at that time and came up with a range of between 20 and 50,000,000 civilizations in the universe capable of human-like communications. I should note that 20 is just that, not 20 million.

The Scientific Method

As with all good applications of the Scientific Method, Drake put his equation out there so other scientists could tweak it – fine-tuning the numbers, discarding or discounting some variables, and adding others. To his credit, Drake had the courage to try to quantify the unquantifiable – he knew he’d be second-guessed and his primary goal was to get the debate started.

Sure enough, scientists today are still pointing out the fallacies and weaknesses of some of the assumptions within Drake’s equation. Others are zeroing in on the degree of unknowns within many of his variables. They claim this makes the calculation worthless – not only for that reason but the fact that the equation doesn’t help us discover the truth and actually find the hypothetical civilizations.

More simply put, my primary question is whether Drake’s equation is even trying to answer the right question.

Naturally, science has marched on over the past 60 years – an eternity when it comes to the evolution of scientific truths – and while it’s possible to zero in more precisely on some of Drake’s variables, it’s clear today that his version of the equation is simply not meaningful.

Thus, other versions of the equation have been proposed … and I’ve taken a crack at it as well.

Is There Anybody Out There?

These are the factors I would plug into a formula to help us determine the likelihood that our universe has life forms and civilizations similar to ours:
The total number of planets in the universe (use any estimate, because as we’ll see, it really doesn’t matter). Multiply this times:

1. The percentage that are located close to the same distance from the sun as the earth
2. The percentage that have close to the same gravity
3. The percentage that have close to the same atmosphere
4. The percentage that have close to the same air composition – oxygen, nitrogen, etc.
5. The percentage that have close to the same air density
6. The percentage that have close to the same weather patterns
7. The percentage that have close to the same rotation and, therefore, day/night cycles
8. The percentage that have close to the same food sources
9. The percentage that have close to the same proportion of water and oceans
10. The percentage that have close to the same predators
11. The percentage that have close to the same level of technological advancement

I’m sure I’m missing other criteria that could be equally critical to defining the true likelihood of faraway civilizations. It’s a fun exercise, though, and it’s a bit mind-blowing to consider all of the unique conditions on planet Earth that need to stay in alignment to support human life.

But the more variables we come up with, the more we find how unique our planet truly is and the less likely it has been replicated to any degree anywhere else. In fact, I’d dare to say the likelihood of finding another planet with human-like aliens approaches zero very quickly.