The Fermi Paradox
Are we the only living things in the entire universe? The observable universe is about 90 billion light-years in diameter. There are at least one hundred billion galaxies, each containing about a thousand billion stars. Recently, we’ve figured that planets are very common, too. And, there are probably trillions and trillions of habitable planets. This means, there should be opportunities for life to develop, right? But… where is it? Shouldn’t the universe be teeming with spaceships? Okay, let’s take a step back.
Even if there are alien civilizations in other galaxies, there’s no way we’ll ever know about them. Basically, everything outside our galactic neighborhood will remain a mystery forever. This is because of the expansion of the universe. Even if we had fast spaceships, it would literally take billions of years to reach these places, traveling through the emptiest areas of the universe. So, let’s focus on the Milky Way.
The Milky Way is our home galaxy. It consists of about four hundred billion stars. That’s a lot of stars, roughly ten thousand for every grain of sand on earth. There are about twenty billion sunlike stars in the Milky Way. An estimate suggests that a fifth of them have Earth-like planets in their habitable zone. If only 0.1% of them contained life, there would be a million planets with life in only the Milky Way.
The Milky Way is 13 billion years old. In the beginning, it would not have been a good place to live in. Things exploded a lot. But after one to two billion years, the first habitable planets were born. Earth is about four billion years old. Considering the numbers, there have probably been trillions of chances for life to develop on other planets. If only one of them had developed into a space-traveling super-civilization, we would’ve noticed by now. What would such a civilization look like? There are three categories.
A type one civilization would be able to access the whole energy available on its planet. In case you’re wondering, we are currently at 0.73 on the scale. We should reach type one sometime in the next couple of centuries. Type two would be a civilization that is able to harness the whole energy of its star. This would require some serious science fiction, but it’s doable in principle. Type three would be a civilization that controls its whole galaxy. An alien race this advanced would probably be godlike to us. But why should we be able to see such a civilization in the first place?
If we were to build generation spaceships that could sustain a population for about one thousand years, we could colonize the whole galaxy in two million years. Sounds like a long time but, remember, the Milky Way is huge. So, if it takes a couple of million years to colonize a galaxy, and if there are habitable planets containing beings who’ve had more time to develop, where are the aliens? This is the Fermi Paradox and no one has an answer to it. But we do have some ideas. Let’s talk about filters. A filter, in this context, means a barrier that is hard for life to overcome. They come in various degrees of scary.
One: there are filters, and we’ve passed them. Maybe it’s way harder for complex life to develop than we think. The process, allowing life to begin, hasn’t been completely figured out, and the conditions might be complex. Maybe, in the past, the universe was way more hostile and, only recently have things cooled down to make life possible. This may also mean that we’re unique and one of the first civilizations in the universe.
Two: there are filters, and they’re ahead of us. This one would be really, really bad. Maybe life exists everywhere in the universe, but is destroyed when it reaches a certain point. A point which is ahead of us. For example, imagine that awesome future technology exists but, once activated, it destroys the planet. The last words of every advanced civilization would be: “This new device will solve all of our problems. Let me just press this button.” If this is true, we are closer to the end of human civilization than the beginning. Or, maybe there’s a type three civilization which monitors the universe and, once a civilization is advanced enough, eliminates it. Maybe there’s something out there that is better not to be discovered. There is no way for us to know.
Another thought: Maybe we’re alone. So far, we don’t have any proof that extraterrestrial life exists. The universe appears to be empty and dead. No one sends us messages; no one answers our calls. We may be completely alone. Trapped in a tiny little mud ball in an eternal universe. Does that thought scare you? If it does, you’re having the correct reaction. If we let life on Earth die, perhaps the universe would be lifeless forever. If this is true, we just have to venture beyond and become the first Type Three civilization. The universe is just too beautiful to not be observed by anyone.