G'day team,

Today I figured I'd stretch a bit (read: a lot) outside my area of expertise, to chat about a topic that I've absolutely no passion for, that has been approached in a way that I have an amazing passion for. For anyone who's ever wondered about the existence of aliens and intelligent civilizations, it's probably worth sticking around!

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Image from Pixabay

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Preamble

Have you ever stared at the night sky and wondered if out there somewhere, an intelligent lifeform was staring back?

Because I haven't.

To be honest the whole 'aliens' thing never really caught my attention. Don't get me wrong! I love the idea of space exploration. I think the next thousand years will be some of the most exciting in the ongoing history of the human race, as we finally venture permanently off our home planet. But I don't waste a minute of time thinking about aliens and if they exist, or if they're watching us because, honestly, we'll never know. No use stressing over something like that when there are real things to stress about down here in the real world (like bloody anti-vaxxers). But quite a while ago (when I was 12 to be precise) I was reading Bill Bryson's Short History of Nearly Everything (best book ever written) and was introduced to the Drake Equation. One of the most straightforward and open-minded approaches to a seemingly impossible problem that I've ever seen, and one that gives us startling insight into the universe around us.

The Drake Equation

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Frank Drake - Wiki

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In April of 1959, while searching for signs of intelligent civilizations around two distant suns, Frank Drake began pondering just how we should go about looking for other intelligent civilizations. Specifically, Drake wanted to find intelligent civilizations (in our solar system) that were trying to find us (or other intelligent civilizations). As the cogs got turning, over the next few months, he would put together a simple equation which allows us to predict the number of alien civilizations currently trying to reach us. So here's the equation...

N = (R*) x (f_p) x (n_e) x (f_l) x (f_i) x (f_c) x (L)

...where

N = the number of intelligent civilizations in the Milky Way that are trying to reach out

R* = the number of stars suitable for sustaining life in the Milky Way

f_p = the fraction of those stars with planets

n_e = the number of planets per solar system with environments suitable for life

f_l = the fraction of suitable planets on which life actually occurs

f_i = the fraction of life forms which evolve to intelligence

f_c = the fraction of intelligent life that forms a civilization advanced enough to reach out

L = the length of time this civilization will reach out for

In essence, the equation breaks down the major factors that play a role in the development of any advanced civilization. In practice, things get a little more complicated. In 1961 when Drake first ran the numbers he came to the conclusion that there were between 1000 and 1,000,000 civilization that matched his criteria in our galaxy. Though he allowed for a massive margin of error, with his lowest and highest estimates for each number calculating out to N = 20 and N = 50,000,000 respectively.

The problem with this equation lies in the individual components... f_l, f_i, f_c and L are incredibly hard to estimate. We don't even know exactly how life arose on earth, so it's unlikely we can predict the likelihood of it arising on an alien planet. Is the fact that humans are the only real intelligent species on earth normal for planets like ours? Is it usually dozens of intelligent species, or none at all? Do intelligent beings pursue science, or even have a need to? If they do, would they be likely to reach out? And at the end of all this, how long does a civilization last? Human civilization is only 6,000 years old and we'd only count as advanced for about 100 of those. Yet we've already been to the brink of wiping ourselves out several times! Would other civilizations face these issues, or would violence be an unheard of concept?

The problem with making predictions about aliens is that they are, well, alien. We don't have a base around which to understand our parameters. There's no reference point. And so we tend to be really conservative with the Drake equation.

Recent estimates are actually less certain than the ones Drake first put forward with ranges from 9.1*10^-11 to over 15,000,000.... with the conservative middle-ground being about ~4000 (with a standard deviation of about a quazillion).

I loved this equation when I first read about it because it's such an elegantly simple way to answer a question that we'd otherwise have no idea about. By breaking down the question into a set of assumptions or estimations we can narrow down our understanding by focusing on the problem part by part. Over the next several decades I'm sure we'll begin to have a better understanding of some of these components.

Fermi's Paradox

Even following conservative estimates, if we extrapolate Drake's equation out to the entire universe (200 billion to 2 trillion galaxies) then we arrive at... a problem. There should be a huge number of intelligent civilizations! So where are they all?

This is what's at the heart of Fermi's Paradox.. the topic of Part 2 of Intelligent Aliens.

Thanks

As usual thanks for reading, team! I hope everyone had fun and learned something fun!

Thanks

-tfc

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Resources
space.com
wiki
SETI Institute
Astrodigital
BBC
Universe Today

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