Purpose of the call: I contacted Dr. Landis to learn about the feasibility of space colonization (especially interstellar colonization) and who the most informed people on that issue are.
Why this person: Anders Sandberg recommended that I speak with him. According to Wikipedia, Dr. Landis works for NASA on planetary exploration, interstellar propulsion, solar power and photovoltaics.
We discussed Dr. Landis’s views about the feasibility of interstellar colonization, the main potential show-stoppers that might make interstellar colonization impossible, and other informed people on these issues. We discussed making machines that continue to function for long interstellar voyages, building ships that humans could survive on for a long time, developing advanced power sources, finding habitable targets, interstellar matter, radiation, and the will to do it. In Dr. Landis’s view, interstellar travel will be extremely difficult, but it’s definitely possible in principle.
These notes were compiled by Nick Beckstead and represent the major points made by Dr. Landis in our conversation.
Dr. Landis believes that interstellar colonization will eventually be doable.
Some aspects of interstellar flight will be technically extremely difficult, but it is definitely possible in principle. The basic physics is straightforward.
We are just beginning to get a statistical sense of what other planets in other solar systems are like. We don’t currently have a good sense of how many of many of these solar systems are habitable or could be made habitable.
There are many unknowns. Some potential challenges include:
1. Long-lasting machines: Interstellar colonization may require making machines that will work for hundreds, thousands, or tens of thousands of years. Few machines can do this now, but perhaps appropriate repair systems would solve the problem. This is something that has not been done, and it’s not clear that it could be done.
2. Human survival on a space colony: It hasn’t been demonstrated that people can live on a space colony, and someone might be skeptical for this reason.
3. Energy source: Enormous amounts of energy will be required, and it might require fusion power. (Some other methods have been proposed as well, including systems using lasers and particle beams.) But fusion power isn’t something we’ve achieved yet. It’s plausible that we will, but perhaps we won’t.
4. Finding a potentially habitable target: Perhaps we won’t be able to find appropriate targets. A random planet probably wouldn’t work. It isn’t at all clear yet that there will be suitable targets. Terraforming might be a solution, but its feasibility hasn’t been demonstrated. Alternatively, there could already be life on other planets. New pathogens could be a major obstacle for people who attempt to colonize other planets.
5. Interstellar matter: There are good theoretical reasons to think there isn’t much millimeter-sized gravel in interstellar space. But if there are sand-sized particles, that would be a challenge for interstellar travel at relativistic or near/relativistic speeds. Shielding may be a solution to this. Alternatively, if interstellar travel must proceed more slowly, some possible solutions would include (i) a generation ship, (ii) freezing people and re-animating them upon arrival, and (iii) travelling with machines or uploads, possibly creating biological humans upon arrival.
6. Radiation: This looks like a problem that could be addressed through shielding. Dr. Landis believes this problem can be solved by creating a strong enough magnetic field.
7. Will to do it: Given the large costs and long time involved with space travel, would people be willing to contribute the money and effort?
a. There is a lot of diversity in the world, and Landis’s intuition is that enough people would want to do it. A possible issue is that because it might require so much energy to do interstellar colonization, anything that could produce that much energy could probably be weaponized. Conceivably, there could be opposition from a larger group of people uninterested in space colonization to creating something that could be used to create a dangerous weapon. Alternatively, people might develop the energy source in order to make a dangerous weapon, and that might be co-opted for interstellar travel.
b. In 1968, Freeman Dyson looked at the economics of interstellar colonization, and it was prohibitively expensive. But he pointed out that there has been a long history of exponential growth in economic productivity and energy production. If these trends continue long enough, interstellar colonization will become much more affordable. On the other hand, exponential trends will not last forever.
Dr. Landis said he could probably think of more potential obstacles if he thought about it.
There’s a burden of proof issue that comes up with many of these issues. When it’s physically possible to do something but we can’t currently do it, does the burden of proof lie with those who would argue that we’ll eventually develop the capability to do it, or the people who think that we never will? There are people on both sides of the issue, but Dr. Landis takes an intermediate stance in many of these cases. It might be feasible, but we haven’t yet proven that it is.
I asked about lack of nitrogen as a possible obstacle, but Dr. Landis assured me that nitrogen is abundant enough that this wouldn’t be an issue.
It’s possible that there are unknown obstacles. Most of the obstacles we’ve discussed seem like they could be overcome. If they can and these are the only obstacles, that makes the Fermi Paradox more puzzling. Someone could argue that this suggests that interstellar colonization is impossible for some unknown reason.
In no particular order,
1. The Icarus Institute
2. The 100 Year Starship
3. Starship Century
4. Les Johnson and his Tennessee Valley Interstellar Workshop
The main classic is The Starflight Handbook: A Pioneer's Guide to Interstellar Travel by Eugene Mallove and Gregorty Matloff. It was written in 1989 but has held up well.
The people in the above groups would probably have opinions that are generally along the same lines as Dr. Landis. Some would be more optimistic, and some would be less optimistic. They would generally agree that space colonization is possible in principle, and most of the disagreement would be about how hard it is.
Most people at NASA generally haven’t thought deeply about this question.
It’s hard to think of notable pessimists. Charlie Stross wrote a good essay arguing for pessimism about space colonies, and he might be a good person to talk to. (Nick raised Stross as the most credible pessimist he was aware of.)
Dr. Landis would consider all of the following:
1. Flesh-and-blood humans who make it all the way within their own lifetime (this is more feasible travelling at high speeds and/or slowing down human metabolism)
2. A generation ship
3. Freezing people and re-animating them upon arrival
4. Travelling with machines or uploads, possibly creating biological humans upon arrival
5. Other “exotic propulsion” possibilities
1. Do you believe that, eventually, interstellar colonization will be possible?
2. Who are the most informed people on the question of the in-principle feasibility of space colonization (especially interstellar colonization)?
3. What is the range of opinion among these people? Who are the most credible people arguing for in-principle feasibility? Who are the most credible skeptics?
4. Why might space colonization (especially interstellar colonization) be impossible? (Alternate framing: Imagine you learned that space colonization wasn’t technologically possible for us, even in principle. In your mind, what are the most plausible reasons that could be true?)
When thinking about interstellar colonization in the very long run, do you imagine humans travelling long distances in spaceships, or something more like von Neumann probes?