Short answer: No. We are not alone.
Long answer: It is so ridiculously unlikely that we are the only sapient species in the universe that the only force you could invoke to explain it would literally be God. In which case, He’s made an awful lot of wasted space.
Right now, we are aware of over 4,100 exoplanets. The biggest problem studying them is that we can’t. There’s simply too many. And for each confirmed planet, there are a few maybes. A few we-aren’t-sures. Scientists are having to pick and choose which maybes to confirm. (AI may solve this problem eventually). Oh, and it can take up to a year to confirm a planet.
And we’re discovering more maybes every day.
The fact is that there are a lot of planets out ther.
What if None of them are Habitable?
Those who like to say humanity is special argue that, well, Earth is unique. In all the vastness of the universe, this planet is the only one ever to evolve complex life.
Now, it’s true that evolving complex life requires quite a few things. For our kind of life at least, it requires liquid water to naturally occur on the surface of the planet. You need a magnetic field. This places a lower limit on the mass of your planet of somewhere between Earth (which has one) and Mars (which had one and lost it). It also places an upper limit on the length of the day. Venus revolves too slowly to generate a magnetic field. This also means that, sorry science fiction writers, life is not going to evolve in the twilight zone of a tidally-locked planet. (That doesn’t necessarily mean we can’t colonize them, it’s now believed that there are tidally-locked planets that may have a pleasant climate. We’d just need shielding).
Oh, and the system also needs to have at least one large gas giant. Why? Because Jupiter does us the wonderful service of catching a lot of the debris in the system, significantly reducing asteroid hits on the inner planets, including Earth. Think about what happened to the dinosaurs…
However, even with these parameters, the idea that out of thousands of planets (and we have only discovered a fraction. We’re still biased towards gas giants in our catalogue) only one hits all of them? That’s just mathematically ridiculous.
What if there’s Life, but not Intelligence?
This is perhaps a bit more feasible. Maybe there are lots of life bearing planets, but most of them don’t evolve intelligent dominant species. At this point, you are adding a few more parameters.
For one, you have to have a good amount of land on your planet. While it’s very likely that an aquatic species could be intelligent (dolphins are pretty smart), it’s unlikely that they could be technological. Same goes for anything living in the atmosphere of a gas giant, which is not impossible.
You also need to have selection pressures that drive intelligence. Our big, complex brains use a lot of energy to grow and maintain. It’s arguable that some “superhabitable” planets may literally be too nice for intelligent life. Our intelligence allows us to evolve faster than natural processes. Need speed? We domesticate horses, then later build cars. Too cold? Clothing. Tool use is essentially using the environment to compensate for physical disadvantages.
Now, one major argument against this is that we have intelligent animals from multiple lineages on Earth. Humans may be top of the tree, but if there’s a second tier it’s occupied not only by other apes, but by corvids, parrots, elephants, and some cetaceans. Elephants bury their dead. One experiment demonstrated that a raven was able to grasp water displacement. Parrots order stuff from Alexa. (Maybe that’s not a sign of intelligence…)
But that doesn’t disprove the “nice planet” hypothesis. That the very nicest planets will be empty (and ready for colonization. And possibly fought over, if you’re looking for ideas for military sci fi).
Even if a minority of planets has life and a minority of that minority has intelligence, though? Based off of those surveys which are finding too many planets, we’re guessing there are at least 100 billion planets…in our galaxy alone. And there are how many galaxies?
Again, it’s ridiculous to say we’re alone.
So, why no Alien Contact?
Fermi’s paradox is used to imply that there are no aliens, because if they are they would have come here.
There’s a few reasons why they might not have:
- Long distance space travel is simply infeasible. If you can’t break the light speed barrier, and all indications right now are that you can’t, it takes centuries to travel between stars. It’s possible that no alien civilization has developed the resources to do so.
- They aren’t interested in us. I mean, maybe they took one look at us and went somewhere else. Or maybe they’re only interested in making contact with species which are closer to their level and with whom trade is more feasible.
- They have a prime directive. Similar argument, but it says that the local civilizations have laws or etiquette that forbids contacting developing species out of fear of interfering with our natural culture. Maybe they need is to grow up some first.
- They’re hiding. The dark forest theory has become more popular of late. This argues that they simply don’t trust us, or anyone, and that aliens keep their heads down. It’s ably covered in The Dark Forest by Liu Cixin (this is part of the Remembrance of Earth’s Past series, which I highly recommend).
- The “we are the elders” theory argues that we are, by some chance or fortune, the most advanced civilization within the feasible range of space exploration. If everyone else is still working on steam engines… It seems unlikely unless you combine it with 1.
- My personal theory, which is this: Resources for space exploration are limited. A civilization would start by remote exploration, then send probes to promising civilization. Let’s say, to over simplify, this civilization has one starship. They discover three systems. System one contains a beautiful superhabitable planet nobody has claimed yet. System two contains a civilization that’s already expanding to the stars. System three is us. Where would you send your one starship? Yeah. Not to us.
But there may be another explanation.
Go back to the top of this article.
Maybe they haven’t found us yet because there are too many planets to look at.
Maybe the simple explanation as to why aliens haven’t made contact with us yet is that they, like us, are so overwhelmed with data that they have to pick and choose which systems to look at. If that’s the case, then the math says it’s more likely that we’re not one of the systems they chose…
Which means that the only way we’re going to be contacted is if we set up a nice big “We are here.” Which has been discussed, but what if it is a dark forest out there…
So, in short. Yes, there are aliens.
They simply may not have found us yet.