This will probably be the most depressing moment of zen.
The Universe is huge, and based on the last decade or so, we’ve learned that the galaxy around us is loaded with planets. We also know that humans are very late bloomers in the grand scheme of things – there were multiple epochs where life grew, evolved, and eventually ended on our planet. At this time, we can observe five massive global extinction events, and 99% of all species that have ever lived on Earth have completely died off. If humans came from the first round of life on Earth, instead of the 6th, it’s possible our calendars would put us around the year 500,000,000 instead of the year 2000. Of course, we also wouldn’t have had any oil or fossil fuels, and thus wouldn’t have been able to mass produce plastics so early on, and we probably would be much larger since oxygen was much more prominent in the air back then.
But this zen isn’t about that.
What about life on other planets? What about a planet like Earth that didn’t waste a bunch of perfectly good dinosaurs for the first half a billion years? On top of that, at only about 4 billion years old, Earth is a relatively young planet. Other star systems in our galaxy could have started forming habitable planets almost 10 billion years before Earth came along.
We don’t really know for sure what a civilization can look like that has hundreds of millions of years behind it, let alone billions of years, but it’s likely that they would be pretty amazing and seem extremely advanced to us. A civilization that’s a billion years old could have easily spread itself across large swathes of the galaxy. In fact, with enough elbow grease, humankind could colonize the entire galaxy in just a couple million years if we put our mind to it. It wouldn’t be pretty, go back to my moment of zen about colonizing Mars.
Our current estimate is that our galaxy alone has 20 billion sun-like stars and about a fifth of them have an Earth-like planet in the habitable zone. If only 0.1% of those planets actually harbored life, there would be a million planets with life in the Milky Way galaxy alone. A million planets, many of them billions of years older than ours, with more time to cultivate civilization, and more time for that civilization to branch out and spread among the stars. On top of all of that, there are at least 100 billion galaxies in the Universe… so where is everybody?
That’s the Fermi Paradox. The Universe’s scariest horror story.
There absolutely SHOULD be other civilizations out there… but we don’t see them or hear them. We don’t see any signs of them, and for decades, we have been looking HARD.
The idea of the Fermi Paradox is that there are great filters that prevent a civilization from getting very far. One idea is that maybe it’s not as easy for complex life (fish, animals, Muppets, etc.) to develop as we thought. Maybe most worlds just don’t have enough combustible resources to allow a species to invent rockets. Maybe every civilization invents the atomic bomb and annihilates itself and we just managed to scrape past that. Maybe every civilization eventually invents some new scientific device to advance their knowledge of physics and it ends up evaporating their atmosphere the moment they turn it on.
Another theory is that a billion-year advanced civilization is simply waiting for any other civilization to get too big for their britches, and swoops in to knock them down a peg the moment they reach a certain level of technical prowess.
Here’s a perfectly reasonable example:
An advanced civilization could get to the point where they decide to install their consciousnesses into massive computers, living happily in a virtual utopia. These computers could span billions and billions of miles long, surrounding stars, soaking up all that delicious solar radiation, and spitting excess heat out into space. It comes to their attention that they could live even better lives if they simply go on standby and wait for the Universe to cool down over the next hundred million years or so – then they could overclock their processors and expand their virtual paradise and thus live even better lives, never aging, never dying, just playing virtual Elden Ring forever.
So they take a long nap, and leave an automated system to protect themselves while they wait for space to get a couple degrees cooler.
That automated system listens for radio broadcasts coming from every star in the galaxy, and as soon as they detect something that might be an artificial signal, they simply fire a thousand-ton chunk of lead at the planet at light speed and instantly annihilate it. In their minds, this is simple, clean, and absolutely effective. It’s no different than setting a mouse trap for us.
Either way, if the great filter is indeed ahead of us, the odds of humanity surpassing it is pretty slim. If the great filter is behind us and we just managed to survive, the odds of finding another civilization is also pretty slim. It’s bad news either way, and if this sounds sad and scary to you, you can be assured that you are a healthy, normal person.