ALIENS! They’ve been in the news. They’ve been in your back yard (potentially). They’ve been in government facilities (allegedly). Are they real?

Let’s talk about some of the basics of whether or not aliens might be real, and why it’s not something to worry about (in my opinion). But first, people have been asking if the government has been in contact with aliens, or picking up alien bodies, or examining pieces of alien ships and I think this blog post perfectly encapsulated my attitude around the general hubbub around aliens in this exact moment.

But what about the hubbub around aliens that has been going on for decades, centuries and potentially even millenia? Let’s talk about this much more important hubbub.

The statistics of Aliens

Here’s the first question we should ask ourselves as we discuss aliens. Is it likely that aliens exist?

The most famous approach to answering this question is called the Drake Equation, named after Frank Drake (not Francis Drake — different guy). The Drake Equation says the number of civilizations that should eventually contact us is a function of:

• How often stars form in our galaxy
• The number of those stars with planets
• The number of those planets that could support life
• The number that actually develop intelligent life
• The number of those life forms that develop technology that we can detect
• How long those life forms utilize that technology in a way we can detect it

We actually have a pretty good idea about those first three bullets, and we can generalize and say it is very likely there are billions of potentially habitable planets in our galaxy, and there could be tens of billions — just in our galaxy. And there are hundreds of billions (potentially trillions) of galaxies in the universe.

On the other hand, we have no idea about the last three bullets, and groups have used the Drake Equation with plausible numbers to argue both that we are alone in the universe, AND that there are millions of civilizations out there — all depending on what numbers they use in those last three bullets.

Statistics are so fun.

So are there millions of civilizations, or none? This leads us to our second cool term.

Why does no one talk to us?

The Fermi Paradox (named after Enrico Fermi) asks the question “If life is so common, why haven’t we heard about it?”

We like to assume that, given enough time, we’ll achieve interstellar travel (travel just between solar systems, not travel between galaxies). It’s taken millions of years for us to progress from using basic tools to mastering flight, but it’s taken mere decades to go from flying under our own power to traveling to the moon. It’s entirely possible that the next step (traveling to another planet in our solar system) will happen within decades as well.

The jump between interplanetary travel to interstellar is huge, but given our current rate of progress how long will it take? Centuries? Millenia?

Even if it takes millenia, that will mean our species went from using our very first tools to traveling between stars in under, let’s say, five million years.

Given that there are millions of stars out there that are billions of years older than our sun, it would seem probable — almost inevitable, given the size of the universe, that someone, somewhere had developed interstellar travel at some time and that we should be able to find evidence of them.

As Fermi may or may not have put it, the question is “Where is everybody?”

There are many different answers to the Fermi paradox. The first is right there in the Drake Equation — if we use pessimistic numbers there is no paradox — no one has talked to us because no one else exists. We are utterly and completely alone in the entire expanse of the cosmos.

Oof.

There are other possible explanations as well. You may remember from my review of the Three Body Problem (and the Dark Forest) that Liu —

Hold on, INTENSE SPOILERS FOR THE THREE BODY PROBLEM AND THE DARK FOREST IN THE NEXT PARAGRAPH. If you don’t want spoilers skip the ver next paragraph.

Liu’s books eventually center around the idea that the universe is a “dark forest” where all species silently stalk, trying to kill each other and avoid being killed by someone bigger. In this logic no one makes noise because anyone who does is immediately killed. This is just … okay, not only is it not to my personal tastes, but I’m going to argue in the next section that it doesn’t make sense. Although I won’t reference this because that would be a spoiler, but you’ll know it when you see it.

END OF SPOILERS FOR THE THREE BODY PROBLEM AND THE DARK FOREST.

So that’s one potential solution to the Fermi Paradox. Another potential solution is that our detectable technology is only a brief phase for most interstellar species and eventually they create technology so advanced that we can’t detect it with our current technology.

There are many other potential solutions, but I’d like to focus on one.

The great filter

The great filter is a term coined by Robin Hanson in a paper originally written in 1995 (and last updated in 1998). Imagine a how-to paper that has 1000 steps required to become an interstellar species. An abbreviated list might look like this:

1. Be on a planet in the habitable zone of a star
2. Develop basic self-replicating biological entities
3. Develop more complicated entities
4. Develop tool using entities
5. Create societies of tool using entities that can cooperate to create more advanced technologies
6. Develop the ability to harness local energy sources
7. Use local energy sources to create powered flight
8. Discover fundamental physics
9. Harness the power of nuclear energy
10. Create powered flight between planets
11. Discover near-light-speed travel using antimatter or something
12. Travel to other solar systems and colonize them

The great filter basically argues that one of these steps is actually really, really hard. He argues that maybe it is the usage of tools, given that millions of species have evolved on earth and only a handful use tools of any kind (and only we have the ability to improve our tools in a meaningful way). Maybe that’s the great filter, and there is other life throughout the universe, but they never got the hang of tools. I mean, Dinosaurs were around WAY longer than us, and they never figured it out.

Or maybe the great filter is something we’re currently grappling with. Harnessing advanced technology is tricky, because the more advanced the technology, the more capable it is of destruction. Maybe the great filter comes right after “harness the power of nuclear energy” and is a step labeled “Don’t blow each other up with it.”

Or maybe the great filter is something yet to come.

One thing that Hanson hints at, but dismisses, is the idea that the great filter explains the solution to the Fermi Paradox in a very positive and encouraging way.

The Zoo Hypothesis

In his paper, Hanson says:

Astronomers Sagan and Newman … claim that either we will destroy ourselves with nuclear weapons, or learn to “live with other groups in mutual respect” by losing “our own predispositions to territoriality and aggression. … This adaptation must apply … with very high precision, to … every individual within the civilization”, so that we become the “least likely to engage in aggressive galactic imperialism” [Sagan & Newman].

Similarly, Papagiannis claims that “those that manage to overcome their innate tendencies toward continuous material growth and replace them with non-material goals will be the only ones to survive this crisis,” implying a galaxy “populated by stable highly ethical and spiritual civilizations” [Papagiannis 84]. And Stephenson claims that “for a truly advanced intelligence the drive for quality rather than redundant quantity would be paramount” [Stephenson 82].

Now of course if a substantial fraction of civilizations followed such scenarios, these theories could explain a small part of the Great Filter. But to explain a substantial part of the Great Filter, such scenarios would have to follow from situations like ours with a very high reliability. While this is logically possible, these authors offer no reasons for expecting such a situation. These theories thus seem more like wishful thinking than serious attempts to explain the phenomena using our best understanding of the social sciences.

This is where I’ll disagree with Hanson, because what he calls “wishful thinking” seems perfectly logical to me.

Interstellar travel will almost certainly require advanced technology (it is extremely unlikely a species would evolve the ability to travel between stars). The nature of technology is such that the more advanced it is, the more it has a capacity for destruction. We currently have the technology to basically render our planet uninhabitable, if we so choose.

What are the odds, in any given year, that we actually do that?

If there is a direct correlation between technological advancement and destructive capability then it makes sense that, ever year, as technology advances, the odds that it could be used to destroy the planet go up. You can see where this goes. Eventually, if things continue linearly, the odds become too great, and the planet (or maybe the whole solar system) is destroyed.

If those are the only variables then, statistically speaking, any slim chance that we will destroy ourselves becomes a certainty. And since the nature of advanced technology requires destructive capability we can extend that and say any other civilization that creates sufficiently advanced technology will eventually destroy themselves.

Unless there are other variables — and that is what Sagan and Newmann were referring to. That along with destructive capability there is another variable, let’s call it “willingness to destroy.” To become a spacefaring people our “willingness to destroy” must decrease as our capability to do so increases until the willingness has completely disappeared.

Using that perspective we can look at the possible great filters and one of the items on our list may very well be “eliminate the willingness to destroy” — at least each other.

Following this logic, interstellar travelers are most likely to be extremely hesitant to employ violence — not the hyper violent invaders often depicted in pop culture. They would also know that other civilizations will naturally come to that same conclusion, if they are to develop the capacity to travel between stars.

By contacting a civilization before they’ve already reached that conclusion they would be upsetting their development, and potentially making them a threat. By allowing other civilizations to develop, knowing that they’ll have to pass through the “great filter” of eliminating the willingness to destroy, they will create good galactic neighbors by doing literally nothing, where doing anything could do exactly the opposite.

And that’s one possible reason why aliens don’t talk to us.