The Planets

Dava Sobel organizes her tour of the solar system as a series of thematic essays, each pairing a celestial body with a distinct angle of human experience: mythology, beauty, geography, music, astrology, science fiction, and personal memoir. The result blends scientific explanation with cultural history and autobiographical reflection to argue that the planets are as much emotional and imaginative landmarks as they are physical worlds.

Sobel opens with "Model Worlds," recalling her childhood planet fascination in 1955, when she built a shoe-box diorama for a science fair and played "Lonely Star" (the Sun) in a class play. A trip to the Hayden Planetarium shattered her vision of a clockwork solar system. She connects the 1957 launch of Sputnik to Cold War anxieties, traces planetary exploration from the Apollo era through the 1980s, and notes the 1995 discovery of the first exoplanet orbiting the star 51 Pegasi. Even as planets multiply across the universe, Sobel argues, they retain the emotional weight of their ancient roles as gods, sources of light, and markers of home.

In "Genesis," Sobel parallels the biblical Creation with the scientific account of the solar system's formation. Approximately 13 billion years ago, the Big Bang produced hydrogen and helium, which stars fused into heavier elements over successive generations. About 5 billion years ago, a cloud of hydrogen and stardust collapsed into a spinning disk, at whose center the Sun ignited. Leftover material assembled into planetesimals, the seeds of planets, each body's composition shaped by its distance from the Sun. The chapter traces the Sun's life cycle and covers the photosphere (its visible surface), sunspots, the solar wind, and total solar eclipses.

"Mythology" examines Mercury through its namesake, the Roman messenger god. Sobel surveys the astronomical lineage from early Greek thinkers Thales and Plato through astronomer Nicolaus Copernicus, who in 1543 placed Mercury closest to the Sun, and Johannes Kepler, who determined its orbit in 1609. Mathematician Urbain Leverrier's 1859 detection of an orbital anomaly led him to hypothesize a planet called Vulcan. Decades of failed searches ended when Albert Einstein's 1915 general relativity explained the anomaly through the warping of space near the Sun. The chapter also covers the Mariner 10 spacecraft's 1974-75 flybys, which revealed a crater-riddled landscape.

"Beauty" pairs Venus with poetry and art. Sobel explains that Venus's brightness derives from reflective clouds, proximity to Earth, and its phases, first observed by astronomer Galileo Galilei. She contrasts Venus and Earth as near twins whose fates diverged: Solar heating evaporated Venus's seas, producing a runaway greenhouse effect with surface temperatures above 800 degrees Fahrenheit. The Russian Venera and Vega spacecraft that landed between 1970 and 1984 each survived only about an hour. Radar mapping by the Magellan spacecraft revealed millions of volcanoes, prompting an all-female naming scheme from the International Astronomical Union (IAU), the body that names planetary features.

"Geography" traces the history of mapping Earth, from geographer Claudius Ptolemy's second-century project in Alexandria, through the mappa mundi (medieval religious world maps centered on Jerusalem), to Christopher Columbus's voyages beginning in 1492. Sobel marks Copernicus's 1543 De Revolutionibus as the moment Earth moved from the center of the universe to an orbit around the Sun. She covers astronomer Edmond Halley's expeditions to chart magnetic variation, Captain James Cook's transit-of-Venus observations from Tahiti, naturalist Charles Darwin's voyage aboard HMS Beagle, and geophysicist Alfred Wegener's 1912 theory of continental drift.

"Lunacy" opens with Sobel's friend Carolyn eating Apollo-era Moon dust given to her by an astronomer boyfriend. The chapter examines the Moon's paradoxical brightness (its surface is as dark as soot, yet rough particles scatter light into radiance), its extreme dryness, and its violent formation when a Mars-sized object struck Earth 4.5 billion years ago. Sobel explains how lunar gravity raises ocean tides, how tidal friction slows Earth's rotation, and how lunar and solar calendars have never aligned. She describes the far side's cratered desolation and a world where a plastic-wrapped photograph left by an astronaut could last a million years.

"Sci-Fi" is narrated by Allan Hills 84001, a 4.5-billion-year-old Martian meteorite found in Antarctica. The meteorite describes its ejection from Mars 16 million years ago and its drift to Earth. Carbonate minerals deposited by ancient Martian water line its cracks, containing possible signs of primitive life. Through the meteorite's voice, Sobel describes Olympus Mons, the solar system's tallest volcano, and the vast Valles Marineris canyon system. She surveys Mars's cultural history, from astronomer Percival Lowell's insistence that a dying civilization built irrigation canals to the Viking landings of 1976, noting that organisms could persist underground despite the hostile surface.

"Astrology" examines Jupiter through Galileo's January 1610 telescopic discovery of its four largest moons, which he named the Medicean stars to secure patronage from Cosimo de' Medici. The moons also bolstered the Copernican heliocentric model by showing that satellites could orbit a planet other than Earth. Sobel analyzes Galileo's natal chart to show how astrology shaped Renaissance thought. She describes Jupiter's enormousness, its cloud stripes and persistent Great Red Spot, and its interior of liquid metallic hydrogen. The chapter recounts the 1994 impact of Comet Shoemaker-Levy 9 and the Galileo spacecraft's 1995-2003 exploration of the Galilean moons, including volcanic Io and ice-capped Europa with its possible subsurface ocean. The spacecraft was deliberately destroyed to prevent contamination of Europa.

"Music of the Spheres" connects Saturn to the affinity between music and astronomy, tracing the relationship from Greek philosopher Pythagoras's insight that mathematical ratios govern both musical tones and planetary spacings, through Kepler's 1619 Harmonice Mundi, to composer Gustav Holst's orchestral suite The Planets (1914-1916). Sobel describes Saturn's ring system, 180,000 miles wide but barely the height of a thirty-story building in depth, and traces the rings' observational history from Galileo through astronomer Christiaan Huygens's 1656 identification to James Clerk Maxwell's proof that they consist of particles obeying resonances analogous to musical harmonics.

"Night Air" presents Uranus and Neptune through a fictional letter from Caroline Herschel, astronomer William Herschel's sister and observing partner, to American astronomer Maria Mitchell. Through Caroline's voice, Sobel recounts William's 1781 discovery of Uranus, which doubled the known width of the solar system. Persistent orbital anomalies led mathematicians Urbain Leverrier and John Couch Adams to independently predict Neptune's position, and astronomer Johann Galle found the planet at the Berlin Observatory on September 23, 1846. A postscript covers the 1977 discovery of Uranus's rings and the classification of both planets as "ice giants."

"UFO" frames Pluto through themes of immigration and contested identity, opening with Sobel's grandfather's arrival at Ellis Island. She introduces Lowell's pursuit of "Planet X" and the 1930 discovery of Pluto by Clyde Tombaugh, a young amateur astronomer from Kansas. Pluto's estimated size shrank dramatically over the decades, and its rationale collapsed after Voyager 2 proved Neptune alone accounted for Uranus's orbital anomalies. Beginning in 1992, hundreds of small bodies beyond Neptune formed the Kuiper Belt, a region predicted by astronomer Gerard Kuiper in 1950, prompting debate about whether Pluto should retain planet status.

The concluding "Planeteers" recounts the Cassini spacecraft's arrival at Saturn and the Huygens probe's landing on Titan, Saturn's largest moon, on January 14, 2005. Scientists had speculated that Titan's thick nitrogen atmosphere might conceal methane seas, but Huygens landed on solid ground and broadcast for several hours. Sobel closes by confessing her enduring view of the planets as "an assortment of magic beans or precious gems in a little private cabinet of wonder, portable, evocative, and swirled in beauty" (236).