Where are all the Aliens? Four Unsettling Explanations to Fermi's Paradox
"Two possibilities exist: Either we are alone in the Universe or we are not. Both are equally terrifying." Arthur C. Clarke
The Fermi Paradox, named after Italian physicist Enrico Fermi, asks the fundamental question, "Where are they?" In a universe that is billions of years old with trillions of stars and planets, shouldn't we see abundant evidence of intelligent life, either from direct visits to our world or proof of massive engineering projects like Dyson spheres visible to astronomers on Earth?
Fermi speculated that at least a few space-faring species should have spread throughout the galaxy by now, even if they were limited to sub-light travel. However, when we look up, the heavens appear devoid of life. Why? Many hypotheses are out there on why this is. I want to look at a few I find the most compelling.
We're Looking in the Wrong Way
Imagine standing alone on a remote mountain with nothing but a powerful two-way radio at your disposal. You decide to use it to see if there's anyone else out there. After trying and trying, you hear nothing. You shouldn't be surprised. For successful contact, you'd need someone else within range who was also using a two-way radio simultaneously and on the same frequency. In other words, you'd need a lucky coincidence of time, space, and circumstance to make contact.
Of course, we know in the real world, far from this mountain, people communicate all the time via satellites, mobile phones, and the internet. Not so much with two-way radios anymore. It turns out that is not the best means of communicating over long distances.
This, I think, could be what it is like in our remote spiral arm of the Milky Way.
We live on remote Earth and see no signs of life anywhere else with our relatively primitive technology. Nevertheless, we try, but if we're using the galactic equivalent of powerful walkie-talkies to do so. Meanwhile, the rest of the universe could be abuzz with chatter we can't detect because we don't have the right technologies.
Then again, if the universe were filled with advanced technological lifeforms, some of them would presumably still be using radio signals and other electromagnetic methods. In other words, some of them might be using the SETI equivalent of two-way radios as well. If they are, we are not picking them up.
The silence is disconcerting.
Interstellar Travel is Not Possible
Our current understanding of physics strongly hints that faster-than-light travel is not theoretically possible. Of course, that may turn out to be wrong, but let's imagine for a minute this is the case. What would it mean for our dreams of interstellar colonization? At a minimum, it would either destroy such ambitions or slow them down dramatically.
The first step in understanding the challenges involved in visiting other star systems is to have some idea of the distances involved. For example, the New Horizons probe that flew past Pluto a few years ago traveled at about 60,000 km/h. At such a speed, it still took nine years to reach Pluto.
Now extend this out to the closest star to our Sun, Proxima Centauri, which is about 4.24 light-years away, or 40,208,000,000,000 kilometers, or 268,770 AU from Earth. (Note one Astronomical Unit (AU) equals the distance from the Sun to the Earth.)
To make this journey, New Horizons would need another 78,000 years to reach Proxima Centauri. To put this on a human scale, that's about 3,100 generations, which would only get us to the nearest star. Remember, we're only about 80 generations removed from the time of Christ, so...yeah.
Another way to understand the scale of distances involved is to imagine the distance between the Earth and Sun as equaling one meter. Alpha Centauri A (a companion star to Proxima Centauri) would still be another 271 kilometers away.
So with some sense of the distances involved in space travel, here's a sobering thought. Perhaps the laws of physics and the finite nature of our biology make deep space travel impossible, or at least so impractical it might as well be impossible.
Travel to other star systems could take hundreds or thousands of generations unless our propulsion technologies significantly improve in the coming decades. Nevertheless, we're limited to the laws of physics, which state that faster-than-light travel is impossible.
I know what you're thinking; someday, we'll discover some technology that will get us around the apparent limitations of physics. I share your faith in scientific progress. Yet, I wonder if our faith is misguided. Many of us take for granted (me included) that technological progress will forever continue on a linear progression upward.
But forever? Really?
We've all been raised on seeing Star Trek warp drives and Star Wars hyperspace travel. That's the inevitable future many of us imagine. Our pop culture science fiction has bred into us a near-religious faith in technology which may, in the end, not be warranted.
This could explain why, when we look up at the night sky, we don't see evidence of space-faring civilizations. If quick interstellar travel was within the realm of the possible, then there should be some evidence by now from others who have gone before us. Yet we see and hear nothing.
However, suppose the universe is teeming with intelligent life, but none of it can escape from its home solar system. These civilizations may thrive for thousands or even millions of years, but they do so within the confines of their own resource-finite solar systems. Maybe space travel to other stars, never mind other galaxies, isn't going to be an option for anyone anywhere. Ever. Full stop. Roll the credits.
If true, what a depressing thought!
Lightning Bugs in a Field
Zoom out. A lot. I want you to imagine extraterrestrial civilizations as lightning bugs in a forest at night. Each flash represents the rise, expansion, plateau, decline, and disappearance of a sophisticated technological civilization somewhere in the galaxy. On a cosmic scale, this entire cycle happens in the blink of an eye.
Or the flash of a lightning bug.
And while we can see all the lightning bugs blinking in real-time in our forest, out in space, the vast distances mean we see those flickers only long after the fact. Perhaps no civilization lasts long enough to communicate with others. And even if two civilizations co-exist simultaneously, the odds are very high that they are hundreds, thousands, or even millions of light-years apart. That blink of light will only be seen long after it has extinguished, and then only by another light shining for a brief cosmic moment.
How rarely do two advanced species exist close enough in time and space to notice each other and establish a dialogue? I suspect this happens only very, very infrequently. By the time the evidence of our existence reaches the nearest galactic neighbor who happens to be listening, we may already be long gone. And vice versa. Thus, each precious iteration of intelligence in the universe sees nothing but emptiness in the sky before eventually returning to the darkness from whence it came.
We're Alone in the Universe
Yes, this is a possibility, though not one I believe to be true. The universe is too big and old to be devoid of other intelligent life. Claiming we're the only intelligent life form out there feels too much like the old Christian anthropocentrism that governed human thought for so long.
If science has shown us anything, it is that we are not so unique after all. Our planet is not the center of the universe. Our Sun is an average star in an ordinary galaxy, one among billions. We are also just one life among the billions that have existed on this planet. That's the humbling narrative science has taught us.
But yet...I feel this pendulum has swung too far in the direction of our insignificance. We are special. Consider this another kind of paradox: we are special because we understand the universe enough to understand we are not special.
We have used our intelligence and reason to reveal the wonders of the cosmos and give us an idea of how small we are in the big scheme of things. We alone ponder. The enigmatic octopus, the loyal canine, the noble elephant, and even our clever cousin, the chimpanzee, do not. Only we do. That's something precious.
Fermi's Paradox, likewise, hints at the rarity of intelligent life in the cosmos. Out of all the species that have lived and died on Earth over the last 3.5 billion years, we are the only ones to have evolved intelligent enough to create an advanced technological civilization.
Still, I'm amazed. What a profound wonder! The universe produced sentient beings with the ability to reflect upon the nature of the cosmos which created them!
Here are enough mysteries and wonder to last a lifetime.
At this point, it's quite clear nothing remotely earth-like exists elsewhere in our solar system. We've found thousands of exoplanets in neighboring star systems, but we may never be able to reach them and almost certainly not in our lifetimes. If we do, they'll most likely be hostile to life as we know it.
Maybe other intelligent species exist somewhere, but we'll never know because we are too remote in space and time. This means, in effect, we are alone. That's the provisional answer to Fermi's Paradox.
We're as if alone and should act like it.
I admit this is unsettling. A deep sense of our cosmic loneliness, combined with an awareness of our existential fragility, should motivate us to care better for the only place we may ever call home, our true goddess and life-giver, our Pale Blue Dot. Earth. We'll live and die on this world, and none other, and that is the truth.
All that said, I, for one, hope we someday discover worlds out there with beings like us gazing in wide wonder at the universe that created them.
And I hope they won't want to eat us.