Purpose of the conversation: I contacted Stross to learn about the feasibility of space colonization (especially interstellar colonization).
Why this person: Stross was recommended by others I spoke to as one of the most informed people that is pessimistic about the feasibility of space colonization, and this fit my experience in a brief literature search.
Stross is highly skeptical of the feasibility of space colonization without radical advances in AI or mind uploading, though he believes space colonization—including interstellar colonization—would be feasible given such advances. Obstacles we discussed included cosmic radiation, finding a hospitable location, sociological adaptation, lack of motivation for space colonization, and propulsion systems. Stross was not aware of other, more developed critiques of the feasibility of space colonization.
These notes reflect the main points made by Stross during our conversation.
For this question, we should distinguish between the feasibility of space colonization using biological humans and space colonization with uploads/advanced AI. The former looks extremely challenging, but the latter looks feasible.
High-energy cosmic radiation: Cosmic radiation would cause cancer. This problem could potentially be addressed with mass shielding (e.g. with a hollowed-out asteroid), magnetic shielding, or better cancer protection techniques (e.g. Vernor Vinge has imagined a prosthetic immune system which might alleviate the problem). There is no clear reason that mass shielding wouldn’t work for a static colony, but for interstellar travel there would be a trade-off between resistance to radiation and ease of propulsion. In Stross’s recollection, magnetic shielding would require extreme amounts of current (e.g. millions of amps running through superconducting magnets), making him skeptical of the feasibility of this solution.
Finding a hospitable location: If you consider all the past and future locations on Earth over time, only a very small fraction of them (probably less than 0.1%) would be habitable for humans. Why? 80% of the Earth’s surface is covered by water, much of the Earth is too cold, there has only been enough oxygen for humans during the last 600 million years, a billion years from now the Earth will no longer be habitable for humans, and so on.
Note: Stross also mentioned some challenges involving off-earth reproduction, getting micronutrients that stomach bacteria need, and damage to human retinae from being in space too long. However, due to a recording malfunction, some of these details were missed in my notes.
If the goal of space colonization is to create another civilization that is viable independently of the continued success of Earth-based civilization, there will be enormous challenges putting in place the large infrastructure necessary for an industrial civilization. Our current industrial civilization—including systems for manufacturing, science, education, entertainment, support systems for people who aren’t working, etc.—probably requires at least a billion people. It is extremely hard to see how to create a space colony capable of replacing our current industrial civilization without at least hundreds of thousands of people.
This objection has received relatively little attention from people optimistic about space colonization. An exception to this is the science fiction novel Learning about the World by Ken McCloud, which focuses on a “generation ship” which has been travelling for thousands of years.
Creating a civilization of this size outside of the Earth would require a very large economic investment, and one that could (at best) have only a very long-term payoff. We currently do not have institutions which function well for highly unprecedented ventures which would require decades—or perhaps even centuries—to pay off. This issue is further explored in Stross’s novel Neptune’s Brood.
People could have various non-economic, ideological reasons for trying to colonize space, and this diversity of motivations could yield attempts despite economic challenges. This is how Stross sees most motivations for colonizing space. Some argue that sufficient diversity of perspectives would make it very likely that people would eventually attempt space colonization if it is feasible at all. However, other ideological perspectives—such as perspectives emphasizing the sacredness of nature—might oppose space colonization. Opposition from these perspectives could prevent an optimistic minority from colonizing space even if it were feasible.
When travelling at a few percent of the speed of light, collisions with interstellar matter could cause significant damage to a vessel. Like radiation, this is something that might be overcome with appropriate shielding, though there are trade-offs between mass from shielding and the amount of energy necessary for propulsion.
Within our solar system, we may want to colonize Mars or the outer part of Venus’s atmosphere. Propulsion technology would be unlikely to be an insurmountable roadblock in this context.
For interstellar colonization, significant advances in propulsion would be necessary. Given the scale necessary for space colonization that might serve as a back-up for our current civilization, this would likely require a propulsion system adequate to accelerate a nation-sized vessel.
Given the existence of mind uploading or advanced AI, Stross sees no insurmountable obstacle to interstellar colonization. In this scenario, it seems that a near-light-speed colonization wave could occur roughly along the lines envisioned by Robert Bradbury.
In Stross’s view, it is not settled whether mind uploading or advanced AI are feasible in principle. If the mind is inherently analog or quantum, digital uploads may be impossible.
Stross has kept his eye on this literature over the years. He was disappointed to know that I didn’t find any critiques of the feasibility of space colonization that were superior to his, though he wasn’t aware of any more developed critiques.
1. What obstacles would prevent us from colonizing space (especially interstellar colonization) now? (For this question, I’ll quickly run through a list I’m aware of and you could add/remove obstacles.)
2. Which of these obstacles do you think can/cannot be overcome?
3. If we overcame all of these obstacles, could we be confident that we would that space colonization (especially interstellar colonization) was feasible? I.e., how plausible is it that space colonization would be impossible for reasons we can’t appreciate right now?
4. Who are the most informed people on these issues? What is your sense of the range of opinion among them?