Chapter 1: A Day with Two Dawns and Midnight at Noon
9 Ancient Chinese eclipse accounts: E. C. Krupp, Beyond the Blue Horizon: Myths and Legends of the Sun, Moon, Stars, and Planets (New York: Oxford University Press, 1991), 158–162.
10 The French astronomer and historian: J.-P. Verdet, The Sky: Mystery, Magic, and Myth, trans. Anthony Zielonka (New York: Harry N. Abrams, 1992), 73.
10 In India, the people banged pots: M. Littman, F. Espenak, and K. Wilcox, Totality: Eclipses of the Sun (New York: Oxford University Press, 2009), 40.
10 “common folk raised a cry . . . ”: Krupp, Beyond the Blue Horizon, 162.
11 paths slowly spiral: J. Meeus, Mathematical Astronomical Morsels (Richmond: Willmann-Bell, 1997), 88–92.
12 one of three solar eclipses: W. B. Masse and R. Soklow, “Black Suns and Dark Times: Cultural Responses to Solar Eclipses in the Ancient Puebloan Southwest,” in Current Studies in Archaeoastronomy: Conversations Across Space and Time, eds. J. W. Fountain and R. M. Sinclair (Durham, NC: Carolina Academic Press, 2005), 57.
12 To the upper left: J. M. Vaquero and J. M. Malville, “On the Solar Petroglyph in the Chaco Canyon,” Mediterranean Archaeology and Archaeometry 14, no. 3 (2014): 189–196.
13 monumental “Great Houses”: Ibid., 196.
13 “The air became very still . . . ”: W. Keeler, “Sharp Rays: Javanese Responses to a Solar Eclipse,” Indonesia 46 (1998): 46, 91.
14 dared not even look: Ibid., 91.
15 “[If the king] does not share . . . ”: P. K. Wang and G. L. Siscoe, “Ancient Chinese Observations of Physical Phenomena Attending Solar Eclipses,” Solar Physics 66 (1980): 190–191.
16 adding an eclipse: D. Henige, “Day Was of Sudden Turned into Night: On the Use of Eclipses for Dating Oral History,” Comparative Studies in Society and History 18, no. 4 (1976): 489–491.
17 “the doctor could predict . . . ”: D. C. Poole, Among the Sioux of Dakota (New York: D. Van Ostrand, 1881), 76–77.
21 “cognitive fluidity”: L. H. Robbins, “Astronomy and Prehistory,” in Astronomy Across Cultures: The History of Non-Western Astronomy, ed. H. Selin (Great Britain: Kluwer Academic, 2000), 37.
21 Evidence for this fluidity: Ibid., 37.
21 Less than a mile from the Nile River: Ibid., 38–39.
Chapter 2: Two Worlds One Sun
34 Moon’s 29.5-day lunation: M. Littman, F. Espenak, and K. Willcox, Totality: Eclipses of the Sun (New York: Oxford University Press, 2009), 29–33.
34 alignment of the Great Houses: J. M. Malville and C. Putnam, Prehistoric Astronomy in the Southwest (Boulder: Johnson Books, 1993), 27–38.
36 eclipse season: F. Espenak, “NASA Eclipse Web Site,” Goddard Space Flight Center, http://eclipse.gsfc.nasa.gov/SEsaros/SEperiodicity.html.
36 great fight in the sky: Littman et al., Totality, 268–269.
37 With little more than these measures: F. Hoyle, On Stonehenge (London: Heineman, 1977), 43–52.
37 Dresden Codex: E. C. Krupp, Beyond the Blue Horizon: Myths and Legends of the Sun, Moon, Stars, and Planets (New York: Oxford University Press, 1991), 162.
39 35 more before it is done: Littman et al., Totality, 268–269.
39–40 Their observations were so precise: M. Ossendrijver, “Ancient Babylonian Astronomers Calculated Jupiter’s Position from the Area Under a Time-Velocity Graph,” Science 351, no. 6272 (2016): 482–484.
40 As far back as the seventh century: F. Rochberg-Halton, “Review Articles: The Babylonian Astronomical Diaries,” Journal of the American Oriental Society 111, no. 2 (1991): 324–326.
40 perfect agreement: A. Aaboe, J. P. Britton, J. A. Henderson, O. Neugebauer, and A. J. Sachs, “Saros Cycle Dates and Related Babylonian Astronomical Texts,” Transactions of the American Philosophical Society, new ser. 81, no. 6 (1991): 1–31.
41 “In this war they brought . . . ”: Herodotus, The Histories, trans. Thomas Worthen, Department of Classics, University of Arizona, 1997, https://scholar.lib.vt.edu/ejournals/ElAnt/V3N7/worthen.html.
41 “day turned to night”: F. Baily, “On the Solar Eclipse Which Is Said to Have Been Predicted by Thales,” Philosophical Transactions of the Royal Society of London 1 (1811): 400–401.
42 World Astronomical Heritage Site: M. E. Ozel, “A Unique Astronomical Heritage Place: The 28 May 585 BCE Solar Eclipse,” in The Role of Astronomy in Society and Culture, Proceedings of IAU Symposium No. 260, eds. D. Valls-Gabaud and A. Boksenberg, International Astronomical Union, 2009.
42 whether Thales actually predicted: D. Panchenko, “Thale’s Prediction of a Solar Eclipse,” Journal for the History of Astronomy 25 (1994): 275–277.
42 Like their colleagues in Babylon: D. Henige, “Day Was of Sudden Turned into Night: On the Use of Eclipses for Dating Oral History,” Comparative Studies in Society and History 18, no. 4 (1976): 484.
45 It works, but: National Science Foundation, “Correct Answers to Science Literacy Questions, Science and Engineering Indicators,” 2006, www.nsf.gov/statistics/seind06/append/c7/at07–10.pdf.
47 “The seeker after the truth . . . ”: A. I. Sabra, “Ibn al-Haytham: Brief Life of an Arab Mathematician: Died Circa 1040,” Harvard Magazine, 2003, based on Ibn al-Haytham’s Book of Optics and Aporias Against Ptolemy, trans. A. I. Sabra.
49 refuted the prevailing claim: M. A. Smith, “What Is the History of Medieval Optics Really About,” Proceedings of the American Physical Society 148, no. 2 (2004): 182.
49 We use this technique today: A. I. Sabra, Ibn al-Haytham, Dictionary of Scientific Biography, vol. 6, eds. Jean Hachette and Joseph Hyrtl (New York: Charles Scribner’s and Sons, 1972), 190.
50 “The undoubted truth . . . ”: A. I. Sabra, “Configuring the Universe: Aporetic, Problem Solving, and Kinematic Modeling as Themes of Arabic Astronomy,” Perspectives on Science 6, no. 3 (1998): 288.
Chapter 3: Shadows Across a Sea of Stars
59 The locations of all those: D. W. Graham and E. Hintz, “Anaxagoras and the Solar Eclipse of 478 BC,” Apeiron: A Journal for Ancient Philosophy and Science 40, no. 4 (2007): 321–335.
59 “Anaxagoras [says that the Moon] is . . . ”: Plutarch, De fac orb lun, 932a.
59 “the sun exceeds . . . ”: Hippolytus, Refutation of All Heresies, I.8.8.
60 bematists: I. Fischer, “Another Look at Eratosthenes’ and Posidonius’ Determinations of the Earth’s Circumference,” Quarterly Journal of the Royal Astronomical Society 16 (1975): 152–153.
62 by as little as 2 percent: Ibid., 153–160.
63 Antikythera Device: C. C. Carman and J. Evans, “On the Epoch of the Antikythera Mechanism and Its Eclipse Predictor,” Archive for History of Exact Sciences 68 (2014): 697–700.
64 1,500 years before metal gears: Ibid., 763.
64 it wasn’t Columbus’s beliefs: Fischer, “Another Look,” 164.
65 The actual distance: V. F. Rickey, “How Columbus Encountered America,” Mathematics Magazine 65 (1992): 223–224.
65 Columbus thought: Ibid., 223–224.
65 In reality, Columbus was only: D. W. Olson, “Columbus and an Eclipse of the Moon,” Sky & Telescope, October 1992, 437–438.
65 a lucky combination: Ibid., 437–440.
66 Meriwether Lewis and William Clark: R. S. Preston, “The Accuracy of the Astronomical Observations of Lewis and Clark,” Proceedings of the American Philosophical Society 144, no. 2 (2000): 176.
66 “Observed an Eclips . . . ”: M. Lewis, W. Clark, and Members of the Corps of Discovery, “The Journals of the Lewis and Clark Expedition: January 14, 1805,” ed. G. Moulton (Lincoln: University of Nebraska Press, 2002), http://lewisandclarkjournals.unl.edu/read/?_xmlsrc=1805–01–14.xml&_xslsrc=LCstyles.xsl.
66 astronomical almanacs: A. J. Large, “How Far West Am I? The Almanac as an Explorer’s Yardstick,” Great Plains Quarterly 13, no. 2 (1993): 119.
67 “Major & brother . . . ”: M. P. Ghiglieri, First Through Grand Canyon: The Secret Journals and Letters of the 1869 Crew Who Explored the Green and Colorado Rivers (Flagstaff, AZ: Puma Press, 2010), 195.
68 “complained that he was losing . . . ”: D. Sobel, Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time (New York: Walker and Company, 2007), 27.
68 location along the Pacific Coast: Large, “How Far West Am I?,” 121.
68 position of the Rocky Mountains: Ibid., 122.
69 Aristarchus measured: J. L. Berggren and N. Sidoli, “Aristarchus’s On the Sizes and Distances of the Sun and Moon: Greek and Arabic Texts,” Archive for History of Exact Sciences 61, no. 3 (2007): 213–254.
73 “I would have several . . . ”: E. Halley, “Methodus singularis quâ Solis Parallaxis sive distantia à Terra, ope Veneris intra Solem conspiciendae, tuto determinare poterit,” Philosophical Transactions of the Royal Society 29 (1716): 454. English translation: “A New Method of Determining the Parallax of the Sun, or His Distance from the Earth,” Abridged Transactions of the Royal Society 6 (1809): 246.
74 “Saturday, 3rd [June 1769] . . . ”: J. Cook, First Voyage Round the World: Captain Cook’s Journal During His First Voyage Round the World Made in H.M. Bark (Barsinghausen, Germany: Unikum Verlag, 2011), 139.
76 “is probably the longest . . . ”: H. S. Hogg, “Out of Old Books: Le Gentil and the Transits of Venus 1761 and 1769,” Journal of the Royal Astronomical Society of Canada 45 (1951): 37.
76 transit expeditions: S. J. Dick, Sky and Ocean Joined: The U.S. Naval Observatory 1830–2000 (Cambridge, UK: Cambridge University Press, 2000), 243.
76 92,885,000 miles: Ibid., 241.
77 two places at once: M. Romer and I. B. Cohen, “Roemer and the First Determination of the Velocity of Light (1676),” Isis 31, no. 2 (1940): 329.
77 thing was impossible: Ibid., 334–335.
78 11 minutes per AU: O. Rømer, “A Demonstration Concerning Motion of Light, Communicated from Paris, in the Journal des Scavans, and Here Made in English,” Philosophical Transactions of the Royal Society 12 (1677): 893–894.
78–79 658,000 AU away: F. W. Bessel, “On the Parallax of 61 Cygni,” Monthly Notices of the Royal Astronomical Society 4 (1838): 160.
80 “Earth 2.0”: J. M. Jenkins et al., “Discovery and Validation of Kepler-452b: A 1.6-R 
Super Earth Exoplanet in the Habitable Zone of a G2 Star,” Astronomical Journal 150, no. 2 (2015): 56.
81 sniffing alien air: D. Charbonneau, T. M. Brown, R. W. Noyes, and R. L. Gilliland, “Detection of an Extrasolar Planet Atmosphere,” Astrophysical Journal 568 (2001): 377.
81 chemical signature: L. Arnold et al., “The Earth as an Extrasolar Transiting Planet. II. HARPS and UVES Detection of Water Vapour, Biogenic O2, and O3,” Astronomy and Astrophysics 564 (2014): 58.
Chapter 4: As Below, So Above
86 wasn’t solid at all: S. Y. Edgerton, “Galileo, Florentine ‘Disegno,’ and the ‘Strange Spottedness’ of the Moon,” Art Journal: Art and Science: Part II, Physical Sciences 44, no. 3 (1984): 226.
87 Galileo, raised in the heart: Edgerton, “Galileo, Florentine,” 225–227.
87 “[I] have been led . . . ”: G. Galilei, Sidereus Nuncius; or the Sidereal Messenger, trans. A. Van Helden (Chicago: University of Chicago Press, 1989), 40.
87 Galileo does not say: Ibid., 38.
87 most exciting moment: T. E. Nordgren et al., “Calibration of the Barnes-Evans Relation Using Interferometric Observations of Cepheids,” Astronomical Journal 123, no. 6 (2002): 3380–3386.
89 Chinese records: G. Galilei and C. Scheiner, On Sunspots, trans. E. Reeves and A. Van Helden (Chicago: University of Chicago Press, 2010), 9.
89 Indian Kashi Khanda text: J. M. Malville and R. P. B. Singh, “Visual Astronomy in the Mythology and Ritual of India: The Sun Temples of Varanasi,” Vistas in Astronomy 39, no. 4 (1995): 443.
90 His letters from this time: F. Baily, Journal of a Tour in Unsettled Parts of North America in 1796 & 1797 (London: Baily Brothers, 1856), 75–320.
90 accepted a position: Ibid., 70–71.
90 calculated the date: F. Baily, “On the Solar Eclipse Which Is Said to Have Been Predicted by Thales,” Philosophical Transactions of the Royal Society of London 1 (1811): 234.
90 Twenty-five years later: F. Baily, “On a Remarkable Phenomenon That Occurs in Total and Annular Eclipses of the Sun,” Memoirs of the Royal Astronomical Society 10 (1838): 31.
91 bright “beads”: Ibid., 5.
91 He got close enough: J. Williamson, “Total Solar Eclipse of October 1780,” Bangor Historical Magazine 6 (1891): 63–65.
91 bright points of light: D. Steel, Eclipse: The Celestial Phenomenon That Changed the Course of History (Washington, DC: Joseph Henry Press, 2001), 177–179.
92 “I was astounded . . . ”: F. Baily, “Some Remarks on the Total Eclipse of the Sun, on July 8th 1842,” Monthly Notices of the Royal Astronomical Society 15 (1846): 4. Unless otherwise noted, italics are reproduced from the original quotations.
93 measured the corona’s extent: J. J. de Ferrer, “Observations of the Eclipse of the Sun, June 16th, 1806, Made at Kinderhook, in the State of New York,” Transactions of the American Philosophical Society 6 (1806): 274.
93 three large red “protuberances”: Baily, “Some Remarks on the Total Eclipse,” 6.
95 The entire expedition equipment list: W. De la Rue, “The Bakerian Lecture: On the Total Solar Eclipse of July 18th, 1860, Observed at Rivabellosa, Near Miranda de Ebro, in Spain,” Philosophical Transactions of the Royal Society of London 152 (1862): 337.
96 “In many cases . . . ”: H. Rothermel, “Images of the Sun: Warren De la Rue, George Biddell Airy and Celestial Photograph,” British Society for the History of Science 26, no. 2 (1993): 137.
97 “We can imagine . . . ”: A. Comte, The Positive Philosophy of Auguste Comte, vol. 2, ed. J. Chapman (London: Chapman, 1853), 9.
100 another twenty-four years: E. B. Frost, “Helium, Astronomically Considered,” Publications of the Astronomical Society of the Pacific 7, no. 45 (1895): 317.
101 agreed well with his calculation: C. Darwin, On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life (London, 1859), 282–287.
102 Fusion was what fueled the Sun: A. S. Eddington, “The Internal Constitution of the Stars,” Observatory 43 (1920): 353–355.
104 “coronium”: C. Young, “The Wave-Length of the Corona Line,” Astrophysical Journal 10 (1899): 306.
107 “If, indeed, the sub-atomic . . . ”: Eddington, “Internal Constitution,” 355.
Chapter 5: The Eclipse That Changed the World
112 found precisely where Le Verrier said it would be: N. W. Hanson, “Leverrier: The Zenith and Nadir of Newtonian Mechanics,” Isis 53, no. 3 (1962): 363.
112 “forces that set nature in motion . . . ”: P. S. Laplace, A Philosophical Essay on Probabilities (New York: J. Wiley, 1902).
114 “His telescope was a small one . . . ”: “Vulcan,” New York Times, May 27, 1873.
115 “searched that region thoroughly . . . ”: “Was It the Intra-Mercurial Planet?” Astronomical Register 7 (1869): 227–228.
116 “with sneering astronomic smiles . . . ”: “Vulcan,” New York Times, September 26, 1876.
116 “I had committed to memory . . . ”: J. Rodgers, “Letters Relating to the Discovery of Intra-Mercurial Planets,” Astronomiche Nachrichten 93 (1878): 162.
116 “about one minute after totality . . . ”: Ibid., 164–165.
117 “one brilliant discovery . . . ”: C. A. Young, “Vulcan and the Corona,” New York Times, August 16, 1878.
117 calculated Vulcan’s size: Ibid.
117 locations didn’t match: Rodgers, “Letters Relating to the Discovery of Intra-Mercurial Planets,” 163–164.
117 “Prof. Swift arrived . . . ”: “The Recent Solar Eclipse,” New York Times, August 4, 1878.
118 “The great eclipse of 1886 . . . ”: L. Swift, “The Intra-Mercurial Planet Question Not Settled,” Sidereal Messenger 2 (1883): 242–243.
118 belt of debris: S. Newcomb, “Note on Accounting for the Secular Variations of the Orbits of Venus and Mercury,” Astronomical Journal 14 (1894): 117–118.
118 simple ring of dust: C. D. Perrine, “The Search for an Intra-Mercurial Planet at the Total Solar Eclipse of 1901, May 18,” Publications of the Astronomical Society of the Pacific 14 (1902): 160–163.
118 unsettling possibility: A. Hall, “A Suggestion in the Theory of Mercury,” Astronomical Journal 14 (1894): 49.
121 “The more important . . . ”: A. A. Michelson, Light Waves and Their Uses (Chicago: University of Chicago Press, 1903).
125 Einstein was influenced: A. I. Miller, Einstein, Picasso: Space, Time, and the Beauty That Causes Havoc (New York: Basic Books, 2001), 2.
130 instruments confiscated: J. Earman and C. Glymour, “Relativity and Eclipses: The British Eclipse Expeditions of 1919 and Their Predecessors,” Historical Studies in the Physical Sciences 11, no. 1 (1980): 62.
130 impounded their instruments: Ibid., 62–63.
130 “No quotations from German . . . ”: Lord Walsingham, “German Naturalists and Nomenclature,” Nature 102, no. 2549 (1918): 4.
130 “for bold initiative . . . ”: M. G. Boccardi, “German Science, and Latin Science,” Observatory 39 (1916): 384–385.
132 “When the Einstein theory . . . ”: Earman and Glymour, “Relativity and Eclipses,” 66.
132 devout Quaker: Ibid., 71.
133 “Eddington was deferred . . . ”: S. Chandrasekhar, “Verifying the Theory of Relativity,” Bulletin of Atomic Scientists 31 (1975): 18.
133 England alone: Earman and Glymour, “Relativity and Eclipses,” 70–71.
135 To prepare the public: A. Sponsel, “Constructing a ‘Revolution in Science’: The Campaign to Promote a Favourable Reception for the 1919 Solar Eclipse Experiments,” British Journal for the History of Science 35, no. 4 (2002): 443–444.
135 “further telegrams . . . ”: Ibid., 444–445.
136 “The result was contrary . . . ”: D. Kennefick, “Testing Relativity from the 1919 Eclipse: A Question of Bias,” Physics Today 62 (2009): 40–41.
136 presented the findings: Sponsel, “Constructing a ‘Revolution in Science,’” 455–459.
136 Dyson and Eddington announced: Ibid., 460–461.
137 “If the results obtained . . . ”: J. J. Thompson, “Joint Eclipse Meeting of the Royal Society and Royal Astronomical Society,” Observatory 42 (1919): 394.
137 “REVOLUTION IN SCIENCE . . . ”: London Times, November 7, 1919.
137 “LIGHTS ALL ASKEW . . . ”: New York Times, November 10, 1919.
138 “decisive” experiment: Earman and Glymour, “Relativity and Eclipses,” 84.
139 Greenwich Observatory confirmed: G. M. Harvey, “Gravitational Deflection of Light,” Observatory 99 (1979): 195–198.
139 But the testing and retesting: Ibid., 42.
139 Precision far greater: Ibid., 41.
139 Astronomers continue to subject the details: B. P. Abbott et al., “Observation of Gravitational Waves from a Binary Black Hole Merger,” Physical Review Letters 116 (2016): 061102.
Chapter 6: Saros Siblings
148 traveled to London: E. Halley, “Observations of the Late Total Eclipse of the Sun on the 22d of April Last Past, Made Before the Royal Society at Their House in the Crane-Court in Fleet-Street, London. By Dr. Edmund Halley, Reg. Soc. Secr. with an Account of What Has Been Communicated from Abroad Concerning the Same,” Philosophical Transactions (1715): 251.
152 “THAT ‘DIAMOND RING’ . . . ”: “That ‘Diamond’ Ring in the Sun’s Eclipse,” New York Times, January 28, 1925, 18.
153 largest formation of airplanes: “35 Airplanes to Take a Big Scientific Party,” New York Times, January 24, 1925, 2.
153 “As the machines winged . . . ”: “View the Eclipse from 25 Airplanes,” New York Times, January 25, 1925, 2.
154 theaters on Broadway: “New Haven Buzzes with Eclipse Talk,” New York Times, January 24, 1925, 2.
155 The Concorde traveled: B. Mulkin, “In Flight: The Story of Los Alamos Eclipse Expeditions,” Los Alamos Science (Winter/Spring 1981), 72.
158 “before an eclipse . . . ”: A. Soojung-Kim Pang, Empire and the Sun: Victorian Solar Eclipse Expeditions (Stanford, CA: Stanford University Press, 2002), 80.
159 “the smoke . . . ”: Ibid., 79–80.
159 The same railroads and steamships: Ibid., 57–60.
159 “It is not at all probable . . . ”: Ibid., 68.
161 citizen-science project: G. Sims and K. Russo, “Citizen Science on the Faroe Islands in Advance of an Eclipse,” Journal of the Royal Astronomical Society of Canada 108, no. 6 (2014): 228.
Chapter 7: The Great American Eclipse and Beyond
172 Australia is currently in the midst: J. Tilley, personal communication, 2015.
175 9.4 million visitors: National Park Service, “Park Statistics,” Great Smokey Mountains National Park website, www.nps.gov/grsm/learn/management/statistics.htm.
Chapter 8: The Last Total Eclipse
193 “all attempts at imposition . . . ”: F. Baily, “On the Solar Eclipse Which Is Said to Have Been Predicted by Thales,” Philosophical Transactions of the Royal Society of London 1 (1811): 236.
193 determine the exact positions: E. Halley, “Some Account of the Ancient State of the City of Palmyra, with Short Remarks upon the Inscriptions Found There,” Philosophical Transactions (1683–1775) 19 (1695–1697): 175.
194 “The real test of progress . . . ”: M. Stanley, “Predicting the Past: Ancient Eclipses and Airy, Newcomb, and Huxley on the Authority of Science,” Isis 103, no. 2 (2012): 263–270.
194 “there are tens of thousands . . . ”: S. Newcomb, Reminiscences of an Astronomer (New York: Houghton Mifflin, 1903), 64.
195 unflinchingly dedicated: Stanley, “Predicting the Past,” 263.
195 During the mania: S. Newcomb, “Note on Accounting for the Secular Variations of the Orbits of Venus and Mercury,” Astronomical Journal 14 (1894): 117–118.
195 “Halley, notwithstanding his scientific merits . . . ”: S. Newcomb, “Researches on the Motion of the Moon” (Washington, DC: Government Printing Office, 1878), 257.
195 new calculations derived: Stanley, “Predicting the Past,” 267.
196 Halley had discovered: F. R. Stephenson, L. V. Morrison, and G. J. Whitrow, “Long-Term Changes in the Rotation of the Earth: 700 B.C. to A.D. 1980,” Philosophical Transactions of the Royal Society of London, series A, Mathematical and Physical Sciences 313, no. 1524 (1984): 48–53.
197 60 million years ago: G. H. Darwin, “On the Precession of a Viscous Spheroid, and on the Remote History of the Earth,” Proceedings of the Royal Society of London 28 (1878): 193–194.
197 The Pacific Ocean: G. H. Darwin, “Problems Connected with the Tides of a Viscous Spheroid,” Proceedings of the Royal Society of London 28 (1878): 196.
197 no plausible mechanism: J. A. O’Keefe and H. C. Urey, “The Deficiency of Siderophile Elements in the Moon,” Philosophical Transactions 285, no. 1327 (1977): 569–575.
198 how rare they might be: H. C. Urey, “Chemical Evidence Relative to the Origin of the Solar System,” Monthly Notices of the Royal Astronomical Society 131 (1964): 218–219.
198 Both of these conclusions: S. G. Brush, “Nickel for Your Thoughts: Urey and the Origin of the Moon,” Science 217 (1982): 894–895.
198 Since oxygen isotope ratios: Ibid., 895.
199 written extensively: J. W. Truran and A. G. W. Cameron, “Evolutionary Models of Nucleosynthesis in the Galaxy,” Astrophysics and Space Science 14, no. 1 (1971): 179–222.
199 He and Ward proposed: A. G. W. Cameron and W. R. Ward, “The Origin of the Moon,” Abstracts of the Lunar and Planetary Science Conference 7 (1976): 120.
200 new planet that was created: R. M. Canup, “Forming a Moon with an Earth-Like Composition via a Giant Impact,” Science 338 (2012): 1052–1054.
201 same hot molten mix: Ibid., 1054.
201 recent computer models: K. Pahlevan and A. Morbidelli, “Collisionless Encounters and the Origin of the Lunar Inclination,” Nature 527 (2015): 492–493.
201 “Had such a population . . . ”: R. Canup, “The Moon’s Tilt for Gold,” Nature 527 (2015): 456.
202 as the bodies cooled and tidal friction grew: B. A. Kagan and N. B. Maslova, “A Stochastic Model of the Earth-Moon Tidal Evolution Accounting for Cyclic Variations of Resonant Properties of the Ocean: An Asymptotic Solution,” Earth, Moon, and Planets 66, no. 2 (1994): 173–175.
203 over its lifespan: G. E. Williams, “Geological Constraints on the Precambrian History of Earth’s Rotation and the Moon’s Orbit,” Reviews of Geophysics 38, no. 1 (2000): 50.
203 At its current, precisely known rate: K. Lambeck, The Earth’s Variable Rotation: Geophysical Causes and Consequences (New York: Cambridge University Press, 1980), 449.
203 ancient seafloor sediments: B. G. Bills and R. D. Ray, “Lunar Orbital Evolution: A Synthesis of Recent Results,” Geophysical Research Letters 26, no. 19 (1999): 3045–3048.
203 “whenever the subject becomes . . . ”: S. Newcomb, “The Course of Nature,” paper presented at the American Association for the Advancement of Science, St. Louis, Missouri, 1878, 23.
204 “primordial soup”: S. L. Miller and H. C. Urey, “Organic Compound Synthesis on the Primitive Earth,” Science 130, no. 3370 (1959).
205 Mars’s obliquity: J. Laskar et al., “Long Term Evolution and Chaotic Diffusion of the Insolation Quantities of Mars,” Icarus 170, no. 2 (2004): 343–364.
205 Moon’s tidal embrace: J. Laskar, F. Joutel, and P. Robutel, “Stabilization of the Earth’s Obliquity by the Moon,” Nature 361, no. 6413 (1993): 615–617.
205 10,000 years ago: J. D. Hays, J. Imbrie, and N. J. Shackleton, “Variations in the Earth’s Orbit: Pacemaker of the Ice Ages,” Science 194, no. 4270 (1976): 1130.
205 Intelligent life on Earth: P. Ward and D. Brownlee, Rare Earth: Why Complex Life Is Uncommon in the Universe (New York: Copernicus Books, 2000).