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Our future, our universe, and other weighty topics

Thursday, October 9, 2014

The 5 Main Fallacies of Galactic Colonization Arguments

Arguments involving galactic colonization are often made when discussing how much intelligent life exists in our galaxy and our universe. One all-too-common line of reasoning goes like this: if intelligent life had arisen elsewhere in the galaxy, it would have already colonized the entire galaxy, and we would see signs of such intelligent life right now on our planet (or we would never have appeared because Earth would have been colonized first); therefore, man is the only intelligent species in the galaxy. This is a very weak argument that involves multiple fallacies that I will now discuss.

Fallacy #1: The Fallacy of Not Realizing the Implications of Slow Interstellar Travel

According to Einstein's Special Theory of Relativity, nothing can travel faster than the speed of light. So this means travel between stars is going to take a long time. In fact, there are practical engineering reasons for thinking that a spaceship could not travel more than roughly about one fifth of the speed of light. This means that a trip between stars will probably take decades.

This slowness of travel has two main implications. First it means that we should not imagine a galaxy being colonized in less than a period of millions of years. But it also means much more. It means that any unified coherent program of colonization is doubtful. The whole idea of any civilization setting out on a million year project may be entirely dubious. The slowness of interstellar travel also probably means that the galaxy can never really be colonized in the sense of being controlled in a unified way by a single culture.

Imagine if Earth were to create colonies on planets revolving around other stars. The nearest colony would be about 4 light years away. The colonists would know that if they went their own way and declared their independence, it would take 4 years for the news of such an announcement to reach Earth. It would then take at least another 4 years before a spaceship came from Earth to punish them for their disobedience (and probably more like twenty years, because of the near-impossibility of traveling at anything close to the speed of light). Such a colony would therefore not feel that it was under very strong political control by Earth.

Colonies that were farther away from Earth would feel even more free to do whatever they wanted. If an expedition from Earth established a colony on a planet revolving around a star that was fifty light years from Earth, then the inhabitants of that planet would know that they could declare their independence, and it would be at least 100 years before they would suffer any punishment – fifty years for the news to get to Earth, and at least fifty years for a punitive expedition to travel from Earth to the colony (but probably more like hundreds of years).

The farther the colony was from Earth, the more its inhabitants would feel that they could do whatever they wanted without suffering any ill effects. If a colony was established 500 light years from Earth, and then declared its independence, it would have no worries at all about some punishment from Earth that could not arrive in less than 1000 years (500 years for the independence announcement to reach Earth, and more than 500 years – and probably thousands of years – for a punitive expedition to travel from Earth). 

This point is illustrated in the diagram below, in which the yellow dot at the center represents a planet attempting to colonize other stars.  

galactic colonization

It would seem, therefore, that in terms of any type of system whereby one planet controls the galaxy, galactic colonization cannot even occur in a meaningful sense. Because of the slowness of interstellar travel, the zones of control of any planet would be relatively short, extending no more than a few hundred light years at most (only a tiny fraction of the size of the galaxy). Planets would realize that, and this realization would make them less likely to even attempt anything such as a colonization of the entire galaxy.

Fallacy #2: The Fallacy of Ignoring Loss of Colonies and Loss of Interest

The typical argument regarding galactic colonization assumes a scenario like this:
  1. Some planet starts out as the source of galactic colonization, sending a spaceship to colonize a planet around another star.
  2. After that planet has been colonized, and has set up an elaborate technical civilization, the colonized planet then itself sends out a spaceship to colonize another star.
  3. The process continues over and over, until eventually the entire galaxy is colonized.
One great weakness in such an idea is the fallacy of assuming that once each planet was colonized, it would continue to contribute to the overall program of galactic colonization, and also the fallacy of assuming that planets that had been colonized would stay colonized indefinitely. It's kind of like the fallacy of assuming that if you built a house on each continent, that those houses would still be around 1000 years later.

In fact, there are all kinds of reasons why different planets that had been colonized would either “drop out” of a colonization program, or would revert to a non-colonized state because of the failure of colonies or the end of civilizations. One reason might just be an act of political independence. Some planets would just say, “To hell with it, we have no interest in sending out interstellar spaceships.” Then other colonies would simply just simply dissolve for the same reason that civilizations have dissolved or might dissolve – resource issues, wars, runaway technology, and so forth. Some planets might be conquered by neighboring planets. When colonies failed, a few million years of geological activity might be sufficient to remove all traces of them.

The point is that you cannot assume that during the million years or more needed to colonize the entire galaxy, that each previously colonized planet would stay colonized. During that long million years, some fraction of the previously colonized planets would revert to being not colonized as colonies failed, civilizations fell, war took its toll, and so forth. We have no idea of what that fraction would be. It be could 10% or 20% or perhaps 90%. 
Fallacy #3: The Fallacy of Assuming That Colonizers Would Colonize All Colonization Targets

The fallacious argument discussed at the beginning of this blog post assumes that some galactic civilization would go throughout the galaxy and colonize all available colonization targets (all planets like our planet). But why make such an assumption? It is contrary to what we know about how humans act.

In fact, every large country declares a significant fraction of the available land in its country to be “off limits” to development. Such land is put in natural reserves. The natural reserves in the United States include the national park system and the national forests, which together make up a significant fraction of United States territory. China has a similar system. So why should we assume that interstellar colonizers would colonize every available planet in the galaxy without declaring some planets and some parts of the galaxy to be “off limits” to colonizers? We shouldn't. This possibility makes the whole “if they existed, they would have colonized us already” argument fall apart like a house of cards. It is entirely possible that our planet is part of a little section of the galaxy that some superior civilization has preserved as a reserve area not to be colonized.

The fallacy discussed here is kind of a “fallacy of assuming unlimited utilization” similar to the fallacy of assuming that if you give a boy some crayons and one of those books with blank white pages, then necessarily if you return a year later all of the pages will have drawings or scribbles on them.

Fallacy #4: The Fallacy of Assuming That Very Distant Robotic Squatters Would Have Some Great Net Value

One version of the argument made at the beginning of this blog post is based on the idea of self-reproducing robotic colonizers. The argument goes like this: any civilization could send out a spaceship filled with robots to the nearest star, and when that spaceship arrived, those robots could use resources at that star system to create more robots, which could then travel to another star in their own expedition. The same thing could happen over and over again, and eventually these self-reproducing robots would “take over the galaxy.” But this hasn't happened, so therefore, the argument goes, we must be alone in the galaxy.

The problem with this argument is the underlying assumption that such a galaxy-wide proliferation would actually be “taking over the galaxy,” or that it would be something that would actually have much of a net value. Because the effective zones of control of any planet would be relatively short (actually extending no more than 100 light years), sending out robots to inhabit planets across the galaxy would not really be “taking over the galaxy,” but really just “sending out squatters to the distant corners of the galaxy.” Having robots 20,000 light years away wouldn't actually give a planet any control over distant corners of the galaxy, because you don't have any real control when it takes 40,000 years to send a round trip message from a planet to those distant corners.

Such robotic squatters proliferating throughout every planet of the galaxy would actually have a very strong negative value. By proliferating all over the place and taking up every planet, they would prevent the natural evolution of diverse species and civilizations across the galaxy, and would thereby be a kind of massive “crime against diversity.”

Fallacy #5: The Fallacy of Ignoring the Possibility of Counter-Colonizers

According to the naïve calculations of some thinkers, we need merely calculate how long it would take colonizers from one planet to spread throughout the galaxy unimpeded. But such calculations ignore the important consideration that the efforts of any one planet to colonize the galaxy would probably be resisted by other planets. If intelligent life arose roughly the same time on hundreds or thousands of planets in the galaxy, we would not expect any one to take over the galaxy, because of opposition from other civilized planets that arose at roughly the same time.

This is true even if one imagines robotic colonizers. One interesting point is that self-replicating counter-colonizers are just as easy to create as self-replicating colonizers. So imagine one civilization sends out an interstellar spaceship filled with self-reproducing robots instructed to build colonies, make more robots, and build more spaceships for more interstellar expeditions. The same technique can be used by some other planet to destroy the colonization efforts of the first planet. The second planet might launch such a “counter-colonization” interstellar spaceship filled with self-reproducing robots instructed to find resources, make more robots, and build more spaceships for more interstellar expeditions – not for the purpose of colonization, but simply for the purpose of destroying the robotic colonies created by the first planet. A planet might launch such a “counter-colonization” program if it noticed that some other planet was putting its robots all over the galaxy, and the first planet thought that such a program was a cancer that must be wiped out. 

galactic colonization


Typical arguments involving galactic colonization are fallacious, and from such arguments we should not draw any conclusions about how common intelligence is in our galaxy. It is entirely plausible that there exist very large numbers of extraterrestrial civilizations in our galaxy, although it is still too early to assume with confidence that intelligent life is abundant in our galaxy.