A beginner’s guide to the Fermi Paradox

Disclaimer: This is in no way intended to be a comprehensive or all-encompassing post. This is designed to inspire thought and encourage discussion. We’ll also be focusing primarily on our home galaxy, the Milky Way.

So what is the Fermi Paradox? It is deceptively simple, yet excruciatingly complex. The basics are thus:

  • There are hundreds of billions of stars in our Galaxy. Many of which are billions of years older than our own sun.
  • There are bound to be Earthlike planets orbiting other stars.
  • Intelligent life could have developed on those planets.
  • Some of those intelligent species could have developed interstellar travel.
  • So why haven’t we found proof of extraterrestrial intelligence yet?

This is a question with no clear cut answer. There are many ideas. But at the end of the day, they are purely opinion.

The first thing we need to look at is called the “Great Filter”. This is the idea that there is some existential factor that is preventing interstellar travel. There must be an uninterrupted line of progression for a civilization to form and become capable of interstellar travel, and something happens along the way that blocks progress.

Think about where we stand on Earth. Man made dangers aside, we’re one gamma ray burst or meteor impact away from being back in the stone age. If we survive it.   One burp (coronal mass ejection) from our sun and it is goodbye power grid, internet, satellites, GPS… dogs and cats living together, mass hysteria. It isn’t a matter of “if” something will wipe us out. It is a matter of “when”.

It isn’t unreasonable to think that other civilizations have faced these same hazards and fallen victim to them. And that is only one facet of the Great Filter. That doesn’t look at the self-imposed risk we, as a society, seem hell bent on creating for ourselves.  Climate change, overpopulation, nuclear war, rogue AI.

But enough doom and gloom. Let’s move on to the fun part. Let’s assume that aliens DO exist and have managed dodge the existential bullets of the Great Filter. Heck, let’s assume they are right next door (on a galactic scale). We’ll say the exoplanet the little green dudes live on orbits Proxima Centauri. Only 4.2ish lightyears away.

Even that “close” is still indescribably far away. Think about it like this: The light from the sun takes an average of 8 minutes to reach Earth. And the sun is 93 million miles away from us. Proxima Centauri is about 264,600 times farther away. When we point our telescopes towards PC, we are seeing electromagnetic emissions that happened 4 years ago.

To the best of our knowledge, faster than light travel is impossible. We can’t even hit a respectable fraction of that with our fastest probes. It took Voyager 1 35 years just to leave to solar system. At the time of this writing, Voyager 1 is 20 light HOURS away from the sun and has been hurtling through space for 41 years.

Now that we’ve beat the “space is really big” thing to death, we can get to the fun part. Let’s pretend there is an advanced civilization out there somewhere that has survived past the Great Filter.

Perhaps they haven’t perfected interstellar travel yet. But what about radio (and other electromagnetic) transmissions? It isn’t likely alien planets 50 lightyears away can watch I Love Lucy reruns. By the time the waves travel that far, they are scattered and weak. So unless the signal was specifically aimed at Earth, and sent with a fairly beefy transmitter, there is a good chance we’d never notice it. Or we may not have sensitive enough receivers. Or the signals could have been sent and hit Earth during our Bronze age.

Or maybe, just maybe, we’ve already heard them. On August 15th, 1977, SETI received what is referred to as the “Wow!” signal. Beaming in from somewhere in the region of Sagittarius, the “Big Ear” radio telescope heard the signal for 72 seconds. Repeated attempts to find the signal again have been fruitless. Many hypotheses have been put forth as to the origin of the signal, most of them being completely mundane. But it is fun to think it might have been aliens.  

One last thing to consider. From the alien’s perspective, we’re just as far away and undetectable to them as they are to us. The aforementioned Voyager probes have only just recently entered interstellar space.

Aboard each probe is a 12-inch record, made from copper and plated in gold. Each record contains sounds from Earth and pictograms. An interstellar message in a bottle. Maybe some day an alien ship will notice a miniscule blip on its sensors. Maybe they’ll reach out and capture the blip and figure out how to play the record. And maybe it will inspire them to swing by our little mudball and say hello. Personally, I like that idea.

I think my bias is clear. Obviously, I think the idea we are alone in the universe is preposterously improbable. I’ve only really discussed the hundreds of billions of stars in our galaxy. And mostly our closest neighbors. That isn’t taking the billions of other galaxies into consideration. Each of those has hundreds of billions of stars.

That’s where we’re going to leave it for this installment. There will be more to come. For now, I would love to hear your thoughts on the points I’ve hit so far.

No, I’m not quite done. Before I leave you to think about looking up and out, I’d like to challenge you to spend a few minutes thinking inward.


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