19. A certain nostalgia for the Paleolithic appears from time to time in which we lament the change from forager to conqueror. It is, in fact, an interesting question: were we actually better off before we discovered agriculture and started the slide toward modernity? Yuval Noah Harari is eloquent on this question in the book Sapiens: A Brief History of Humankind (Harper, 2015). In some ways we may have been happier, though less safe and secure, when we were all hunter-gatherers. Perhaps, but this doesn’t really help us now, does it?
20. For a thoughtful introduction to this subject, see Peter G. Brown and Peter Timmeran, eds., Ecological Economics for the Anthropocene (New York: Columbia University Press, 2015).
21. Around the time Our Final Hour came out, Rees also placed a bet on the Long Bets website, soliciting others to bet against his proposition that “By 2020, bioterror or bioerror will lead to one million casualties in a single event.” Sir Martin wrote his book in 2003, and by now, at the time of this writing, we have already survived 16 percent of the twenty-first century. There are only a few years to go until Rees loses his bet. Does that change the math? I am always wary of such sanguine arguments. People sometimes imply that since we survived the Cold War, it may not have been such an existential threat. Yet of course in all those possible histories where the unthinkable did happen, we would not have been here to have the conversation. So there is a strange selection effect, hard to factor, that might lead one to unwarranted optimism.
22. Caveat emptor: it’s not a perfect system. This history is still being worked out and will, at some level, always be in revision. So if the boundaries are assigned to specific events, then the dates will have to shift. Alternatively, if we leave the dates set in (ahem) stone, the boundaries will soon no longer match the actual physical transitions they were meant to mark. So there is some tension between constancy and accuracy. It’s like discussing a party that was supposed to start at 8:00 but for which people showed up at 8:35. When you later refer to the start time of the party, do you mean 8:00 p.m. or when the people actually showed up? The hour 8:00 p.m. is easier but less accurate. Who cares? Nobody—unless suddenly it becomes important to reconstruct events. Say you were visited by police investigating a crime that occurred at 8:15 and in which one of your party guests was a suspect? All of a sudden the actual, rather than the idealized, start time would be very important. So it is when we investigate the mysteries of Earth history—we need a common timescale.Science has not made up its mind, so there is minor confusion and debate about all these boundaries—but that’s okay. They work well enough, and when you talk to geologists about the transition from the Archean to the Proterozoic, they generally know what you mean.
23. Zahnle et al., “Emergence of a Habitable Planet,” Space Science Reviews 129 (2007): 35–78.
Chapter 6: Intelligent Worlds in the Universe
1. What we know about life elsewhere: it makes copies of itself. That’s it, really. Must they be carbon copies? Or is there another chemical system that would do the trick? We don’t know. So we search for what we know, sometimes forgetting to retain the humility appropriate for our level of ignorance.
2. C. H. Lineweaver, “Paleontological Tests: Human-Like Intelligence Is Not a Convergent Feature of Evolution,” in J. Seckbach and M. Walsh, eds., From Fossils to Astrobiology (Netherlands: Springer, 2008).
3. After presenting his challenge to its conceptual basis, Charley wraps up his paper by stating his strong support for SETI. This would be a strange position to take if he fully embraced his own argument and was thoroughly convinced that the field was based on a wrongheaded (so to speak) assumption. This increases my suspicion that he is largely just arguing for the sheer joy of it. In this he differentiates himself from his predecessors Mayr and Simpson, who argued that it was foolish and wasteful to expend any resources on searching for extraterrestrial life or intelligence. Charley concludes: “We do not need to misinterpret the fossil record to justify this inspiring research.” Quite true—and we do not need to overinterpret the fossil record to realize that the odds of success are not to be determined here on Earth but out among the numberless stars.
4. Phil cowrote and narrated (in his distinctive, soothing, raspy voice) the classic, somewhat psychedelic 1977 film Powers of Ten, which brilliantly synthesizes modern scientific understanding of where we stand within the scales and structures of the universe. It takes viewers on a cosmic journey beginning with a scene of a happy heterosexual couple picnicking on the Chicago lakeside, receding outward to a view of the whole Earth, past the orbit of the Moon, the planets, the other stars, on out to the farthest reaches of the known universe. Then it reverses and plunges inward, back again to the lakeside, only to keep going, zooming into the man’s hand and his cells, molecules, atoms, down to the subatomic particles. At the end, a single proton fills the field, full of fuzzy, quivering quarks. Phil’s final statement that “we have reached the edge of present understanding” carries a promise that in the future we would see farther, and continue the trip.
5. Shapley’s estimates of the specific quantities involved are quite different from the numbers we would use today. Admitting that astronomers of 1952 knew little about how planets form, he said, “Let us be skeptical and suppose that, in whatever way they come, only one star out of a million is blessed with a family of planets.” His estimate for the fraction with planets in the habitable zone was similarly cautious: “Suppose we skeptically guess that only one star family out of a thousand has a planet with the happy requirements of a suitable distance from the star, near-circular orbit, proper mass, salubrious atmosphere, and reasonable rotation period—all of which are necessary for life as we know it on the Earth.” This is pretty good astrobiology from about forty-five years before the birth of astrobiology.
6. A brouhaha about possible “alien megastructures” around the star KIC 8462852, or Tabby’s Star, arose because the enigmatic changes in light from this star seem to reveal some strange configuration of orbiting material. Conceivably, this could be something like a Dyson swarm. Almost surely there will be a more prosaic explanation, but at the time of this writing, it is still a mystery. I wrote about this here: http://www.skyandtelescope.com/astronomy-blogs/cosmic-relief-david-grinspoon/could-it-be-possible-signs-of-e-t-intelligence/.
7. This dependence of the density of civilizations on L is very well illustrated with a visual analogy in Timothy Ferris’s television film Life Beyond Earth. Ferris showed a Christmas tree with lights flashing on and off, and demonstrated that if you vary the length of time the lights stay on, then the appearance of the tree, at any instant in time, changes noticeably. If each light comes on for only a fraction of a second, then at any given time a snapshot shows only a few lights on an otherwise dark tree. If the lights all stay on for several seconds before blinking off, then the tree is always full of glowing lights. The longer the average “lifetime,” the shorter the distance from one lit bulb to the next. The dark tree, with just a few lights, is analogous to the situation in the galaxy if civilizations generally don’t last long. There may be others, somewhere out in the vast Milky Way, but the average distance between them would likely render two-way communication impossible. If the average civilization has a long lifetime, then the tree, or the galaxy, is densely lit up. Then the distance to our nearest communicating neighbor may be quite short.
8. Small world department: McNeill was invited by Sagan to broaden the generalized discussion of “civilizations” with a historian’s perspective. He is the father of and occasional collaborator with environmental historian and Georgetown University history professor John McNeill, who today is a leading scholar of the Anthropocene. I had no idea of this connection when I met the younger McNeill, and we both became founding members of our informal Washington Anthropocene Group.
9. Recently some scholars analyzing the detailed history of the escalations, and miscommunications of that episode, have concluded that it was a very close call. The commanders on the ground in Cuba were given the
authority to launch nuclear missiles if the Americans attacked. The Americans were poised to attack with conventional weapons, assuming, wrongly, that this would not provoke a nuclear counterattack. Some analyses suggest there was perhaps a fifty-fifty chance that it could have led to the start of a nuclear war, a favorable coin toss allowing the rest of history after 1963.
10. It is also said that he didn’t actually say this. If so, then he should have.
11. Note that for the purposes of this discussion I may use the term intelligent life or intelligence as shorthand for technological intelligence. Quite clearly there are other species, such as dolphins and perhaps elephants, some primates, and others possessing quite a bit of intelligence but no global technological civilization. I don’t mean to assert any claim of superiority over such mindful, less manipulative creatures. There is a reasonable argument for the opposite claim. Here, however, I am discussing the possibility of planets where intelligence, for better or worse, has produced some kind of global technological civilization.
12. If there is a bifurcation in civilizational lifetimes, with one branch being quasi-immortal, it implies that the number of civilizations is not in steady state, as implicitly assumed in the Drake equation, but increasing as the universe ages. A further implication is that our own prospects for long-term survival and developing a sustainable civilization may be completely decoupled from the number of technical civilizations in the universe. We often conflate the two in our discussions of L. Given that ET civilizations, if they exist and we are able to find them, are assumed to represent some imagined, hoped-for, future state of our own evolution, we often identify L with ideas about our own future prospects with statements such as “If we are likely to destroy ourselves in a nuclear war, then it implies that L is short and there is nobody out there.” This is wrong because L is not our own longevity but the average of all civilizations in the galaxy, and there is always the chance that we are highly atypical, lucky or unlucky. If there is a bifurcation of lifetimes, then our fate, our future prospect, may have even less correspondence with the number of advanced civilizations out there. The universe could be populated with an increasing number of aged civilizations that have made it through the bottleneck, even if most civilizations at our stage typically don’t survive for long. To see how both could be true, consider the reproductive strategy of dandelions or mice: organisms that make huge numbers of offspring so that just a few can survive to adulthood (what biologists call r-strategy, or r-selected, species, as opposed to k-strategy, or k-selected, species, which produce far fewer young and carefully nurture each individual toward adulthood). For creatures with this life history, the typical fate of any newborns is not to survive to maturity, but those few who do may have a very long life, even while there is not much hope for any young individual. Most acorns do not become tall trees, but the forest is dominated by trees. Our civilization may just be an acorn. In which case, we may have little chance of making it to maturity. Yet even if that is the case, there may still be plenty of mature civilizations, tall trees growing in the galactic forest. Even if it is highly unusual for a baby civilization like ours to achieve adulthood, the galaxy could still be full of adults. Although it matters very much to us how long we survive, it is quite possible that our longevity has very little connection to the overall chance that intelligence can thrive for very long timescales. Of course this picture is all wrong if the formation of an immortal is so improbable as never to happen within the age of the universe. The weakest link here is the assumption that any civilization ever makes it through the technological bottleneck to a state where they have the ability to use their technology for long-term survival. This will depend on how “the race between education and catastrophe” is won on other worlds. If catastrophe always wins, there will be no immortals.
13. The quote is from the beautiful first paragraph of H. G. Wells’s War of the Worlds.
14. The use of this phrase has been criticized by some who point out that the Fermi paradox, strictly speaking, is neither Fermi’s nor necessarily a paradox, since it’s only a paradox if you accept the arguable premises, and others before and after Fermi have contributed to the idea. But it rolls off the tongue better than the “Fermi-Tsiolkovsky-Fontenelle-Lem-Bracewell-Hart question.”
15. Philip Morrison, who worked with Fermi designing bombs at Los Alamos, before essentially founding SETI, described Fermi questions as follows: “the estimation of rough but quantitative answers to unexpected questions about many aspects of the natural world. The method was the common and frequently amusing practice of Enrico Fermi, perhaps the most widely creative physicist of our times. Fermi delighted to think up and at once to discuss and to answer questions which drew upon deep understanding of the world, upon everyday experience, and upon the ability to make rough approximations, inspired guesses, and statistical estimates from very little data.” An example of a Fermi question is: how many piano tuners are there in the city of Chicago? You can make a decent estimate by starting with a rough idea of the population of Chicago, estimating what percentage of households has a piano, roughly how often those pianos need to get tuned, how long that takes, and how many people that could employ. The final answer you get, provided you’ve set it up correctly and made reasonable guestimates, is often surprisingly close to the actual number you would find if you solved the problem more carefully. Other Fermi questions described by Morrison include: What is the photon flux at the eye from a faint visible star? How far can a crow fly? How many atoms could be reasonably claimed to belong to the jurisdiction of the United States? What is the output power of a firefly, a French horn, an earthquake?
16. Start with David Brin’s classic paper “The Great Silence—the Controversy Concerning Extraterrestrial Intelligent Life,” Quarterly Journal of the Royal Astronomical Society 24, no. 3 (1983): 283–309. Then read If the Universe Is Teeming with Aliens… WHERE IS EVERYBODY?: Fifty Solutions to the Fermi Paradox and the Problem of Extraterrestrial Life, by Stephen Webb (New York: Copernicus Books, 2002). I also discuss many possible answers in my book Lonely Planets: The Natural Philosophy of Alien Life (New York: HarperCollins, 2003).
17. Fermi’s paradox was discussed in 1933 by Tsiolkovsky (and even alluded to by French natural philosopher Bernard le Bovier de Fontenelle in his 1686 book, Conversations on the Plurality of Worlds). Tsiolkovsky’s answer was that the advanced ETs were aware of us but were leaving us alone because we are not ready for contact. Just as today we are motivated to protect biodiversity in part to see what nifty unknown chemicals we can derive from wild, unknown species, Tsiolkovsky also proposed that by allowing us to flourish, as long as we remained harmless to galactic civilization, advanced aliens could see what intellectual innovations we would develop on our own that might ultimately add to cosmic culture.
18. J. D. Haqq-Misra and S. D. Baum, “The Sustainability Solution to the Fermi Paradox,” Journal of the British Interplanetary Society 62 (2009): 47–51.
Chapter 7: Finding Our Voice
1. In fact—now it can be told—the day Lewis introduced us at a Space Resources workshop at the Scripps Research Institute in the summer of 1984, the three of us went to see the then-new film Revenge of the Nerds in a San Diego multiplex.
2. The possibility of machine sentience also raises some moral questions. Asimov’s laws, if enacted, would create robots whose only purpose was to do our bidding. Yet if these were truly sentient creatures, wouldn’t they have rights? And wouldn’t it be wrong, then, to design them to remain our slaves forever?
3. Referenced above. NRC Climate Intervention reports 2015.
4. This kind of planetary radar observation is how Sasha Zaitsev made a name for himself in astronomy long before he decided to send his controversial targeted messages.
5. The question of best practices seems tricky. With biotechnology and planetary protection, expert opinion was marshaled into a list of guidelines for how to proceed safely. Honestly, it’s hard for me to think of a comparable set of gu
idelines for active SETI. I’ve tried to imagine what practicing “safe METI” would look like. Is there really any way to broadcast more safely? If we limit power or length of a broadcast, we are limiting our chances of success. I suppose we could insist that stars must be over a certain distance to be “contacted,” thus ensuring that our descendants have plenty of time to think about how they would react to any response, but that is just kicking the can down the time line. The real question seems to be binary. We decide that it’s either too risky or not. The discussion that needs to happen is “go or no-go.” If we consider the very far future, there is a possible scenario for broadcasting with safety. An advanced species could send beacons from somewhere far out in space, distant enough from their own world that they could avoid giving away their address. Someday, once we are a confident deep-spacefaring species, we might be able to accomplish this. To do so, we would need to be operating from beyond our own solar system. We are so far off from being able to do this that it doesn’t seem a very helpful solution to consider.
6. See, for example, http://www.dearet.org/, https://www.newhorizonsmessage.com/, and http://breakthroughinitiatives.org/Initiative/2.
Chapter 8: Embracing the Human Planet
1. This comes from a letter Jefferson wrote to Madison from Paris in September 1789.
2. Video online at http://www.loc.gov/loc/kluge/webcasts/grinspoon-julynov2013-feature.html.
3. J. F. Mouhot, “Thomas Jefferson and I,” Solutions 5, no. 6 (March 2015): 74–78, http://www.thesolutionsjournal.org/node/237268.
4. Ibid.
5. Since moved on to the University of California, Davis.
6. The Longevity of Human Civilization: Will We Survive Our World-Changing Technologies? symposium held at the Library of Congress, September 12, 2013. Video and transcript at http://www.loc.gov/loc/kluge/news/nasa-program-2013.html.
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