Space colonization: what can we definitely do and how do we know that?

Looking back at our paper, I think the weakest points are (1) we handwave the accelerator a bit too much (I now think laser launching is the way to go), and (2) we also handwave the retro-rockets (it is hard to scale down nuclear rockets; I think a detachable laser retro-rocket is better now). I am less concerned about planetary disassembly and building destination infrastructure: this is standard extrapolation of automation, robotics and APM.

However, our paper mostly deals with sending a civilization's seeds everywhere, it does not deal with near term space settlement. That requires a slightly different intellectual approach.

What I am doing in my book is trying to look at a "minimum viable product" - not a nice project worth doing (a la O'Neill/Bezos) but the crudest approach that can show a lower bound. Basically, we know humans can survive for years on something like the ISS. If we can show that an ISS-like system can (1) produce food and other necessities for life, (2) allow crew to mine space resources, (3) turn them into more habitat and life support material, (4) crew can thrive well enough to reproduce, and (5) this system can build more copies of itself with new crew at a faster rate than the system fails - then we have a pretty firm proof of space settlement feasibility. I suspect (1) is close to demonstration, (2) and (3) needs more work, (4) is likely a long term question that must be tested empirically, and (5) will be hard to strictly prove at present but can be made fairly plausible.

If the above minimal system is doable (and I am pretty firmly convinced it is - the hairy engineering problems are just messy engineering, rather than pushing against any limits of physics) then we can settle the solar system. Interstellar settlement requires either self-sufficient habitats that can last very long (and perhaps spread by hopping from Oort-object to Oort-object), AI-run mini-probes as in our paper, or extremely large amounts of energy for fast transport (I suspect having a Dyson sphere is a good start).

I wrote a post which targets the "and how do we know that?" part of this question.

Full post here [LW · GW] which has elaboration and examples for each of the types. Headings for the argument/evidence types:

1. Our understanding of the laws of physics says it should be possible. (Argument from Physics/Basic Science)
2. Nature has done this, so reasonably we as intelligent beings in nature should eventually be able to too. (Argument from Nature)
3. We have a proof of concept. (Argument from POC)
4. We've done it already. (Argument from Accomplishment)

The post also includes a couple of paragraphs on where these arguments fall short and how they're stronger in the case of long-term space colonization.

Hi Ruby, since I've actually given this topic some thought I'm gonna delurk for once. The issue I have with FHI's space papers is that they basically pay no attention to questions of governance. Being able to reach things and being able to coordinate/control things are two very different things. Space is way too big for central control. Even in the Milky Way you'd probably need something in the ballpark of 100'000c for a central government to make sense. Consequently, we probably overestimate the degree to which space settlement is controllable and the constant usage of the term "colonization" is confusing, if not plainly wrong. I wrote a more comprehensive version (ca 45 minutes reading time) of this argument here: https://medium.com/@KevinKohlerFM/cosmic-anarchy-and-its-consequences-b1a557b1a2e3

The answer to this question likely depends heavily on what we consider to be adequate colonization:

1) Running computation in others star systems, i.e. Running digital minds on computers or other computational processes. (this is what Eternity in Six Hours assumes)

or

2) Having actual, ordinary biological humans colonize the stars.

There are challenges common and separate to each.

Lasting the Journey

In either case, you must be able to create a probe (to use the language of Eternity in Six Hours) which can last the duration for a trip which lasts thousands to millions of years. Is it at all feasible to have humans last long in some form? (Perhaps only as embryos which can be "grown" upon arrival, but even then, can we safely preserve biological material for millenia?) Could cryonics somehow be a solution? Even if you were only sending computers/robots, can we build electrical and mechanical devices which won't break down after such extremely long time periods?

Challenges for Humans

Nick Beckstead's prelimenary notes mention microgravity, cosmic radiation, health and reproduction in space, and genetic diversity as considerations which come into play when sending live humans through space.

Challenges for Computers

Can we build machines (assume non-AGI) we can solve all the problems they will encounter in different systems?

An attempt from Nick Beckstead on almost this question:

Will we eventually be able to colonize other stars? Notes from a preliminary review (June 2014)

Summary

I investigated this question because of its potential relevance to existential risk and the long-term future more generally. There are a limited number of books and scientific papers on the topic and the core questions are generally not regarded as resolved, but the people who seem most informed about the issue generally believe that space colonization will eventually be possible. I found no books or scientific papers arguing for in-principle infeasibility, and believe I would have found important ones if they existed. The blog posts and journalistic pieces arguing for the infeasibility of space colonization are largely unconvincing due to lack of depth and failure to engage with relevant counterarguments.

The potential obstacles to space colonization include: very large energy requirements, health and reproductive challenges from microgravity and cosmic radiation, short human lifespans in comparison with great distances for interstellar travel, maintaining a minimal level of genetic diversity, finding a hospitable target, substantial scale requirements for building another civilization, economic challenges due to large costs and delayed returns, and potential political resistance. Each of these obstacles has various proposed solutions and/or arguments that the problem is not insurmountable. Many of these obstacles would be easier to overcome given potential advances in AI, robotics, manufacturing, and propulsion technology.

Deeper investigation of this topic could address the feasibility of the relevant advances in AI, robotics, manufacturing, and propulsion technology. My intuition is that such investigation would lend further support to the conclusion that interstellar colonization will eventually be possible.

Note: This investigation relied significantly on interviews and Wikipedia articles because I’m unfamiliar with the area, there are not many very authoritative sources, and I was trying to review this question quickly.