Every surviving civilization is obliged to become spacefaring — not because of exploratory or romantic zeal, but for the most practical reason imaginable: staying alive.
Karl Sagan, Pale blue dot
In this series, we have looked at the relationship between two claims:
(Existential Risk Pessimism) Per-century existential risk is very high.
(Astronomical Value Thesis) Efforts to mitigate existential risk have astronomically high expected value.
Part 1 introduced a Simple Model of existential risk mitigation and used that model to show that Existential Risk Pessimism, far from supporting the Astronomical Value Thesis, threatens to tell against it.
Part 2 considered some failed strategies for reconciling Pessimism with the Astronomical Value Thesis.
Part 3 introduced a strategy that might work, the Time of Perils Hypothesis that risk is high now, but will soon drop to a lower level. We saw that the Time of Perils Hypothesis would be enough to reconcile Pessimism with the Astronomical Value Thesis provided we assume (a) a short time of perils, and (b) a very sharp drop in existential risk after the time of perils.
But why should we believe the Time of Perils Hypothesis? Here is one reason you might believe it.
2. Settling the stars
You might think that the Time of Perils will end as humanity expands across the stars. So long as humanity remains tied to a single planet, we can be wiped out by a single catastrophe. But if humanity settles many different planets, it may take an unlikely series of independent calamities to wipe us all out.
This thought has been defended at length by the astronomer Martin Cirkovic, who argues that space colonization is the only viable prospect for long-term human survival. It was also voiced by Carl Sagan, who concluded immediately after introducing the concept of the time of perils that “every surviving civilization is obliged to become spacefaring — not because of exploratory or romantic zeal, but for the most practical reason imaginable: staying alive”. And the same thought has been cited by Elon Musk as one of his primary reasons for pursuing Mars colonization. Could the prospects for space settlement ground a time of perils hypothesis of the needed form?
The problem with space settlement is that it’s not fast enough to help the Pessimist. To see the point, distinguish two types of existential risks:
- Anthropogenic risks: Risks posed by human activity, such as greenhouse gas emissions and bioterrorism.
- Natural risks: Risks posed by the environment, such as asteroid impacts and naturally occurring diseases.
It’s quite right that space settlement would quickly drive down natural risk. It’s highly unlikely for three planets in the same solar system to be struck by planet-busting asteroids in the same century. But the problem is that Pessimists weren’t terribly concerned about natural risk. For example, Toby Ord estimates natural risk in the next century at 1/10,000, but overall risk at 1/6. So Pessimists shouldn’t think that a drop in natural risk will do much to bring the Time of Perils to a close.
Could settling the stars drive down anthropogenic risks? Recall that the Pessimist needs a (a) quick and (b) very sharp drop in existential risk to bring the Time of Perils to an end. The problem is that although space settlement will help with some anthropogenic risks, it’s unlikely to drive a quick and very sharp drop in the risks that count.
To see the point, consider Toby Ord’s estimates of the risk posed by various anthropogenic threats (Figure 1). Short-term space settlement would doubtless bring relief for the threats in the green box. After we’re done destroying this planet, we can always find another. And it is much easier to nuke Russia than it is to nuke Mars (but please don’t!). However, the Pessimist thinks that the threats in the green box are inconsequential compared to those in the red box. So we can’t bring the Time of Perils to an end by focusing on the green box.
Figure 1: Ord’s estimates of anthropogenic risk
What about the threats in the red box, such as AI risk and engineered pandemics? Perhaps long-term space settlement will help with these threats. It is not so easy to send a sleeper virus to Alpha Centauri. But we saw in Part 3 that the Pessimist needs a fast end to the Time of Perils, within the next 10-20 centuries at most. Could near-term space settlement reduce the threats in the red box?
Perhaps it would help a bit. But it’s hard to see how we could chop 3−4 orders of magnitude off these threats just by settling Mars. Are we to imagine that a superintelligent machine could come to control all life on earth, but find itself stymied by a few stubborn Martian colonists? That a dastardly group of scientists designs and unleashes a pandemic which kills every human living on earth, but cannot manage to transport the pathogen to other planets within our solar system? Perhaps there is some plausibility to these scenarios. But if you put 99.9% probability or better on such scenarios, then boy do I have a bridge to sell you.
So far, we have seen that banking on space settlement won’t be enough to ground a Time of Perils Hypothesis of the form the Pessimist needs. How else might she argue for the Time of Perils Hypothesis? In the next two parts of this series, I’ll consider other arguments for the Time of Perils Hypothesis.
In the meantime, let me know what you think of the Time of Perils Hypothesis. I certainly hope that humanity will manage to settle the stars. What do you think that this prospect implies for the Time of Perils Hypothesis?