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Bob Park
Bob Park’s disdain for human spaceflight might explain the lack of evidence of alien civilizations. (credit: J. Foust)

The Park hypothesis

Bob Park will be remembered as a persistent human spaceflight critic, a leader of the anti-human-spaceflight movement. But he could also help solve one of the great space mysteries of all time: Do intelligent aliens exist, and if so, where are they?

First, some background information. The Search for Extraterrestrial Intelligence (SETI) is challenged by an idea called the Fermi Paradox. Enrico Fermi thought that if intelligent alien civilizations existed, they would inevitably colonize the galaxy. Travelling slower than the speed of light, they would still colonize the galaxy in a relatively short time. And if our galaxy was colonized, we would know all about it. Fermi concluded that intelligent aliens do not exist.

The Fermi Paradox drew a wide range of speculative hypotheses. Maybe intelligent aliens did exist, but they became extinct before they reached us. Maybe they have isolated us for observation and study (the zoo hypothesis). Maybe they are waiting until our civilization reaches a certain developmental stage (the sentinel hypothesis). Or could there be another explanation?

The Park hypothesis states that intelligent alien civilizations do exist, but they have not colonized the galaxy because they don’t want to.

Since the only intelligent civilization that we know of is our own, our experiences may provide insights into how intelligent aliens behave. We regularly have a debate over what to send to space. It is known as the humans versus robots debate, or the manned versus unmanned debate, or with a more accurate description it could be called the both-humans-and-robots versus robots-only debate. Now, if an intelligent civilization such as ours is having this debate, then it is possible that intelligent alien civilizations are doing the same thing. Of course, they wouldn’t call it a humans versus robots debate. From their perspective it would be an our-species versus robots debate, and from our perspective it would be an aliens versus robots debate. And like our intellectuals, their intellectuals may conclude that alien spaceflight is obsolete, and a robots-only space policy would be sensible, logical, and right. They would dismiss colonization as a hopeless fantasy.

If this is true, then aliens would be very difficult to detect. A robot probe is much harder to detect than worlds colonized by aliens. The communication between a robot probe and its homeworld would be a much weaker signal than the communication between a homeworld and its colonies. Aliens that resolved to stay on their home planet would leave a very small footprint on the galaxy, one easily overlooked.

The Park hypothesis states that intelligent alien civilizations do exist, but they have not colonized the galaxy because they don’t want to. It neatly resolves both the Drake Equation, which indicates that intelligent aliens are likely to exist, and the Fermi Paradox: no colonization means we don’t see them.

A criticism of the Park hypothesis is that while some alien civilizations act in accordance with Bob Park’s principles, it would be unrealistic to expect all of them to comply. The analogy is that some people support Bob Park, but others disagree with him, sometimes quite strongly. This is a valid criticism, but the counter-argument is that unanimity is not required. If a dominant civilization, or group of civilizations, bans colonization throughout the galaxy, then it will not take place, no matter how much other civilizations protest. Since colonization is difficult to accomplish anyway, the addition of legal and political impediments will make it near impossible.

If we detect signs of a Parkist civilization, unfortunately they may not be around to see us.

If there are Parkist (or Park-like) civilizations in the galaxy, what should we expect of them? One characteristic of one-planet civilizations is their elevated rate of extinction. Every civilized planet in the galaxy is susceptible to planetary disasters, such as collision with other bodies, and large-scale nuclear or biological war. Two-planet civilizations have a reduced rate of extinction, and three-planet civilizations have further reductions. But since Parkist civilizations have decided to put all their eggs in one basket, their rate of extinction is significantly higher. This translates to a low value for L (civilization lifetime) in the Drake Equation. If we detect signs of a Parkist civilization, unfortunately they may not be around to see us.

A galaxy that is predominantly inhabited by Parkist civilizations could be called a Parkist galaxy. Such a galaxy could be identified by its unique appearance: a few scattered single planets of intelligent life, amid vast areas either devoid of life or occupied by simple organisms only. In contrast, a galaxy with Fermi’s alien civilizations would be filled with intelligent life.

I have previously mentioned that we have the humans versus robots debate, and aliens may have its equivalent. Now that we have the Park hypothesis, it could also be possible that aliens have its equivalent too, perhaps named after a famous anti-alien-spaceflight activist of its world. At this very moment, aliens could be thinking about a civilization like ours, wondering whether we exist, where we are in space, and why Parkism is so popular here.