1 1. James S. A. Corey, Leviathan Wakes (London: Orbit, 2011), 19.

      2 2. Estimates based on the amount of carbon, water, phosphorus, and nitrogen on carbonaceous asteroids suggest that the solar system could theoretically support a human population 100,000 times that of the present Earth population. See Michael N. Mautner, “Life‐centered Ethics, and the Human Future in Space,” Bioethics 23 (2009), 433–440.

      3 3. John Leslie, “The Risk that Humans Will Soon Be Extinct,” Philosophy 85 (2010), 447–463.

      4 4. Derek Parfit, Reasons and Persons (Oxford: Clarendon Press, 1984), 452.

      5 5. A recent study confirms that most people do not at first sight seem to think that human extinction would be much worse than near‐extinction, which allows for recovery, but the reason might be that they focus too much on the immediate death and suffering. When prompted to think about long‐term consequences, they tend to agree that extinction is worse. However, the quality of the alternative future is relevant—people consider extinction much worse if the alternative future would be very good. See Stefan Schubert, Lucius Caviola, and Nadira S. Faber, “The Psychology of Existential Risk: Moral Judgments About Human Extinction,” Scientific Reports 9 (2019), 1–8.

      6 6. Parfit, Reasons and Persons, 453.

      7 7. Samuel Scheffler, Death and the Afterlife (Oxford: Oxford University Press, 2013); Samuel Scheffler, Why Worry About Future Generations? (Oxford: Oxford University Press, 2018).

      8 8. For example, David Benatar, Better Never to Have Been: The Harm of Coming into Existence (Oxford: Oxford University Press, 2008).

      9 9. Leviathan Wakes, 465.

      10 10. James Lenman, “On Becoming Extinct,” Pacific Philosophical Quarterly 83 (2002), 254.

      11 11. A recent estimate is that there might be around 36 civilizations in our galaxy and that it might take over 6,000 years of SETI efforts to achieve communication. Tom Westby and Christopher J. Conselice, “The Astrobiological Copernican Weak and Strong Limits for Intelligent Life,” The Astrophysical Journal 896 (2020), 58.

      12 12. Derek Parfit, On What Matters, volume 2 (Oxford: Oxford University Press, 2011), 620.

      13 13. Lenman, “On Becoming Extinct,” 257.

      14 14. James S. A. Corey, Cibola Burn (London: Orbit, 2014), 44.

      15 15. Alan R. Johnson, “Biodiversity Requirements for Self‐sustaining Space Colonies,” Futures 110 (2019), 24–27.

      16 16. For an interesting discussion of this topic, see the talk by philosopher Gwen Bradford, “Is There a Moral Obligation to Go to Mars?”, especially the Q&A, in which colonization is discussed. Lone Star College‐Kingwood (Nov. 1, 2019). “Curious Minds: Is There a Moral Obligation to Go to Mars?” Presented by Gwen Bradford [Video]. YouTube. https://www.youtube.com/watch?v=w4iaAONU7u4.

      17 17. P. A. Carpenter and P. C. Bishop, “A Review of Previous Mass Extinctions and Historic Catastrophic Events,” Futures 41 (2009), 676–682.

      18 18. Dennis Ray Morgan, “World on Fire: Two Scenarios of the Destruction of Human Civilization and Possible Extinction of the Human Race,” Futures 41 (2009), 683–693.

      19 19. Leslie, “The Risk.”

      20 20. Milan M. Ćirković, “Space Colonization Remains the Only Long‐term Option for Humanity: A Reply to Torres,” Futures 105 (2019), 166–173, 169.

      21 21. Joseph Gottlieb, “Space Colonization and Existential Risk,” Journal of the American Philosophical Association 5 (2019), 306–320.

      22 22. Leviathan Wakes, 512.

      23 23. That is a specious argument—like begrudging money spent in biodiversity protection “when there are people dying of hunger.” We cannot wait until there are no immediate needs before starting to tackle other long‐term problems.

      24 24. Charles S. Cockell, Space on Earth: Saving Our World by Seeking Others (New York: Palgrave Macmillan, 2006).

      25 25. James S. A. Corey, Caliban’s War (London: Orbit, 2012), 578.

      26 26. Leviathan Wakes, 62.

      27 27. Clive Finlayson, The Humans Who Went Extinct: Why Neanderthals Died Out and We Survived (Oxford: Oxford University Press, 2009), 44.

      28 28. See, for example, the following books, all of which consider other Homo species as human: G. Philip Rightmire, The Evolution of Homo Erectus: Comparative Anatomical Studies of an Extinct Human Species (Cambridge: Cambridge University Press, 1993); Finlayson, The Humans Who Went Extinct; Chris Stringer, Lone Survivors: How We Came to Be the Only Humans on Earth (New York: Henry Holt and Company/Times Books, 2012).

      29 29. Finlayson, The Humans Who Went Extinct.

      30 30. Phil Torres, “Space Colonization and Suffering Risks: Reassessing the ‘Maxipok Rule,’” Futures 100 (2018), 74–85.

      31 31. James S. A. Corey, Nemesis Games (London: Orbit, 2015), 410.

      32 32. Ćirković, “Space Colonization,” 171.

      33 33. As shown in James S. A. Corey, Persepolis Rising (London: Orbit, 2018) and Tiamat’s Wrath (London: Orbit, 2020).

      34 34. Caliban’s