I had this discussion with some friends on Facebook recently, and it was pretty interesting. I’m a lifelong science fiction fan. As such, I’ll admit that I kind of want there to be aliens. Parts of me likes believing the various conspiracies about ancient alien visitors building the pyramids or the various stories about what really happened at Roswell. It’s cool to think that the government has alien spacecraft, and maybe even some aliens bodies, stashed away at Area 51.

But wanting something to be true doesn’t mean that it is true. So let’s try to look at this logically.

First, let’s be clear, when we’re talking about the possibility of aliens, what we mean are alien civilizations. Intelligent beings whom we could theoretically communicate with. We’re not talking about microbes or bacteria on some other planet. I’d say that stuff like that is a given. We know there are planets, including some right here in our solar system, which have vast bodies of water. Therefore I’d say it’s likely there’s some kind of life in them, even if it’s just little alien fish. Likewise, some other planets may have plant-life, which could also mean there’s some kind of alien insects. But that’s not what I’m theorizing about here.

So if there are aliens, where are they? Here are some possibilities regarding alien life, and why we haven’t definitively contacted any yet:

Let’s take these step by step. Starting with Rare Earth.

It seems unlikely that in the vastness of the universe (which itself is estimated to be over 13 billion years old) with all of the other planets and galaxies out there, that ours is the one and only planet where intelligent life as developed.  But unlikely is not the same as impossible. Maybe the conditions that cause (or allow) life to develop are so dang rare that this is the only time it’s happened? Until such a time as we get definitive proof of other intelligent life somewhere else, then this theory is as good as any.

Great Filter.

I have to say that this one makes a lot of sense to me. For a civilization to not only develop but to become advanced enough that they would have the means to travel the vast  distance of space to our planet from wherever they are, would likely take a long time. It took about 6 million years for humanity to get to our current state, and we’ve only barely made it to our moon. So going to other solar systems is still far in our future. And there’s no guarantee that we will survive long enough to become that advanced, Shoot, just the fact that we’ve made it this long can be considered lucky. We almost had a nuclear war in 1962. And that was a real potential deliberate action. There have been many times where we almost had a nuclear war started by accident.  And those are just the times that we know about. Who knows how many other “close calls” there actually were which the world government just haven’t told us about? Not to mention other natural disasters and rampant diseases that almost wiped us out at various times throughout history.

So maybe there have been other civilizations that just didn’t survive their equivalent of the Cuban Missle Crises, or their version of the Bubonic plague, or denied their planet’s devestating climate change until it was too late, and just never got to the point that they would be able to contact us? That seems like a stronger possibility to me than Rare Earth, at least.

Great Silence.

Basically, this proposes that perhaps we’re just not worth aliens’ time. This theory has been used in science fiction, most notably (that I’m aware of) in Star Trek, where the Vulcans (and possibly some other alien races) were aware of humans but didn’t deem us advanced enough to make contact with until we developed warp-drive (in the year 2063, according to the film Star Trek: First Contact). And that’s become the standard yardstick by which subsequent civilizations are judged to be ready for contact and invitation to join the United Federation of Planets. If a civilization is “pre-warp”, then they’re just left alone. Could something like that be real? Could some advanced alien civilization be out their observing us from afar, keeping out of our way until they see if we reach some specifical technological (or cultural) advancement that makes us “ready” for them, in their opinion?

This also fits another long-held theory called The Zoo Hypothesis, which suggests that advanced civilizations could be observing us like we observe animals in the zoo, or fish in a fishbowl. We’re a curiosity to them, but just not considered worthy of direct interaction. This seem more possible to me than Rare Earth, as well, but slightly less probable than Great Filter.

Early Bird.

Maybe we’re the most advanced civilization in the Universe right now? Or least the most advanced in our Galaxy? Perhaps the closest alien civilization to us right now are still in their pre-Industrial phase, or even earlier, still living in caves? Shoot, even if they were just a about a century behind us in terms of technological development, that would mean they haven’t even launched their first satellites into their orbit, so that would make them far from having any ability to contact us or even detect us in any way. So we both have some advancing to do before contact would be possible (presuming we survive the Great Filter theory and don’t destroy ourselves before we have the chance to make contact).

Different Kind of Life.

This is also as possible as any other theory, and like Rare Earth there is no way to ever prove it. But I feel that this falls into the category of what I said I was dismissing in the beginning of this post, as when I speculate of aliens I mean a civilization that we could theoretically communicate with. So some higher life form that we can’t comprehend is no more useful to speculate about that the aforemention alien bacteria (although, I guess, in this scenario, we may be the “alien bacteria”).

In A Far Away Galaxy.

Now this probably makes the most sense to me, and seems most probable. The idea is that yes there is other life out there in the Universe, but it’s really really really really far away.

I mean, taking a quote from one of my all-time favorite books:

This is true, we are just one planet in our solar system, which is one of possibly millions of solar systems in the Milky Way Galaxy, which itself is one of possibly billions of galaxies in the Universe.

It’s this vastness which, as I said, makes the Rare Earth theory seem improbable.There is so much space out there that there must be some other life, but none of them have reached the level of technological advancement necessary to traverse the great distances to find other civilization. Perhaps such technology just can’t be created? Despite being a staple of science fiction, it has been speculated that faster-than-light travel is simply impossible, and thus the means of intersteller contact will never happen. And, tying back to the Great Filter theory, maybe no civilization survives long enough to even get to that level of advancement.

And, in conclusion, I’ll add that perhaps this is a good thing? Again, despite my sci-fi love and concurring desire to meet aliens, I think the Late Stephen Hawking was probably right when he said it may not be worth the risk of letting aliens know that we exist, if they’re out there. Because while we can’t know whether an alien civilization’s intentions toward us would be benign or not, the fact is that any alien intelligence that is advanced enough to travel the vast distances of space that it would likely need to in order to reach us, would be so much more advanced than we currently are that if they did have bad intentions we’d be completely at their mercy. Forget all the books, movies, and TV shows where humanity unites and valiantly fights off the alien invaders, we’d have no hope. No computer viruses, or tap water, or simple germs, or anything else. This would be using a napkin to fight someone armed with a nuclear missle.

So it’s just not worth the risk. Better to just stick to our own solar system and hope to be left alone. Let’s focus on trying to unite our species on this planet and not worry about other possible species’ elsewhere in the universe.