universe? These are deep questions involving advanced research in

biology, chemistry, physics, astronomy, cosmology, and many related

areas. But is it really so hard to answer? In fact, it can be boiled

down to a single equation created by a prominent astronomer in the

1960s, known as the Drake Equation, which will answer all our

questions in one line.

So, what is this magical-sounding equation? It gives us a way to

calculate N, the number of intelligent life forms in our galaxy that

we might possibly communicate with. Here it is, in all its glory:

N = R-star Fp Ne Fl Fi Fc L

Now you know the answers to all the questions of extraterrestrial

life, and we can end the podcast early for today. Right? Well, not

exactly. Perhaps we should figure out what all those terms we are

multiplying together mean first.

R-star is the average rate of star formation in the galaxy.

Fp is the fraction of those stars with planets.

Ne is the average number of planets for each of

those star systems that could theoretically support life.

Fl is the fraction of those planets that actually develop life.

Fi is the fraction of those that develop intelligent life.

Fc is the fraction of intelligent life forms that actually develop

technology for deep-space communication.

And finally, L is the average lifetime of this high-tech phase of

those civilizations.

So, you can see that it's just a common-sense listing of the

things we would have to know in order to calculate the number of alien

life forms.

It is fun to try to fill in plausible-sounding values and figure

out, based on various assumptions, the number of alien life forms we

can communicate with. Naturally, optimists like advocates of SETI

(the Search for Extraterrestrial Intelligence), who believe we should

pour millions of dollars into searching for potentially alien signals

from space, find sets of numbers that give a solution like 5000,

meaning there is an alien lurking around every interstellar corner.

Skeptics, like apparently the author of the Wikipedia article on this

topic, plug in numbers that get an answer closer to 2, which means

that maybe, somewhere out there, there is just one alien civilization

that we might hear from someday. And perhaps we should save our SETI

money to spend on math podcasts.

If you are now somewhat underwhelmed by the power of this

equation, join the club. While it is a neat, concise expression, it

is essentially just listing all the probabilities, for some of which

we just have wild guesses, that we would have to string together to

answer the question of alien life. In a sense, it just begs the

question. But begs it in an authoritative-sounding way. It has been

pointed out that we do have one data point: whatever values one

substitutes in, we would expect N to be at least 1, since we are

pretty sure that *we* exist. But beyond that, I think the biggest

lesson out of this is that just because you can put something in an

equation, doesn't mean you actually know anything useful. On the

other hand, equations do sound very convincing, regardless of how

little information they contain. Perhaps one day an alien life form

will land here and tell us what the real values are.

And this has been your Math Mutation for today.

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