THE PLANETS by Dava Sobel
Fourth Estate £15 pp27lDava Sobel, she of the bestselling Longitude and Galileo’s Daughter, tells in The Planets the true story of her friend Carolyn, who fell in love with an analyst of moon rocks at a university laboratory. The fellow was truly smitten, since he risked his job to give Carolyn a smidgen of moon dust in token of his adoration. Literally, he gave her the moon.
In terms of value, it’s worth remembering that a single carat of moon rock went at auction in 1993 for $500,000. On hearing of this exorbitant gift, Sobel demanded a privileged view of the stuff, whereupon Carolyn answered sheepishly, “I ate it,” adding, “There was so little.” Sobel tells us she then imagined the moon dust caressing Carolyn’s lips like “a lover’s kiss”. Sobel can be a bit like this. “As it entered her mouth, it ignited on contact with her saliva to shoot sparks that lodged in her every cell. Crystalline and alien, it illuminated her body’s dark recessing like pixie powder, thrumming the senseless tune of a wind chime through her veins.”
Why is this moonshine in a book that asks itself to be taken seriously on the solar system? Probably because Sobel has unashamedly gone for a category of readers quantifiable in millions (and I mean readers of, for example, Bill Bryson’s A Short History of Nearly Everything), who like their science served up with plenty of homespun narrative. In the case of the solar system, Sobel is on to a winner, for our imaginative relationship with the planets enjoys multitudinous anecdotal links in a huge circuit of historical, poetical, musical and, yes, love interest.
Fifty years ago, on American prime-time television, Leonard Bernstein denounced scientists for “taking our moon away from us”. The moon, like the rest of the planets, he declared, belongs to poets, and composers: think of Beethoven’s Moonlight Sonata, Mozart’s Jupiter Symphony, Holst’s Planets. Sobel’s book, despite its rich artistic allusions, nevertheless finds its true centre in science and a wealth of impressive facts, which she separates from the non-scientific.
We learn that the sun embodies 99.9% of the mass in our solar system; the planets, moons and comets account for only 0.1%. Earth is, of course, a planet, and currently subject to formidable geological exploration, its crust, above the roiling fluid beneath, accounting for just 0.5% of the planet’s mass. Part of the iron-nickel core at the centre of the earth, moreover, has already cooled to a solid ball. Seismologists can hear it rotating independently inside the molten outer core, turning almost a second a day faster than the rest of our planet. Meanwhile, the solar system orbits the central mass of the Milky Way every 250m years, and light travels outwards only a few miles per year near the sun’s core, where the crush of matter repeatedly absorbs it.
But I was most gripped by the proliferating information on exoplanets — planets orbiting the stars outside the solar system. No exoplanets have been imaged directly, so astronomers are working out their sizes and dynamics by their effect on their parent stars. Scientists have appropriated the name Jupiter as a generic term, meaning a large exoplanet. Thus the mass of an extremely large exoplanet could be estimated as “three jupiters”. The number of them in our Milky Way could far exceed the 100 billion stars within it, a rich source of extraterrestrial life and intelligence.
Sobel’s account proceeds cannily, chapter by chapter, from Mercury and Mythology, to Pluto and UFOs, via Mars and Sci-Fi. Astrology gets its airing in the chapter on Jupiter: there was, after all, a time when astronomy and astrology were inseparable. So, what with planetary music and a veritable anthology of poetry (from Shakespeare, Blake and Wordsworth), as well as histories of planetary observations from the ancients to the latest satellite explorers, Sobel has made every kind of hard scientific and soft cultural allusion grist for her mill. And talking of mills, she tells us that a proper scale model of the solar system, using a bowling ball for the sun, would represent the 8,000-mile-wide earth with a peppercorn placed 78ft distant from the ball. Not a bad teaching aid if you have the space.
The comparison arises in an aside about her attempts to make a shoe-box diorama as a child. I was intrigued by the nonsense mnemonic she was taught to remember the order of the planets outward from the sun. Mine was: “Many virgins eat mango jam sitting under nanny’s piano.” Hers was: “My very educated mother just served us nine pies”: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto. I tried this on my seven-year-old granddaughter last week; she learnt it instantly, and I suspect she won’t forget it.
Sobel’s restless curiosity raises, and settles, a multitude of questions. Did you know, for example, that the reason moonshine bleeds familiar sights of colour is that, at top wattage, the full moon dims in comparison to direct sunlight by a factor of 450,000, falling just below the retina’s threshold for colour vision? Did you know that since Mercury circles the sun in only 88 days, compared to earth’s 365, a year on Mercury passes in just three months? As Sobel comments, with her gravitation to earthbound comparisons, it’s like “dog years”: much the same way that seven years of animal lifetime are packed into a dog owner’s one.
The perspective is decidedly anthropocentric, a criticism that has been frequently levelled even at Richard Dawkins. Literary critics call it the pathetic fallacy: just as there’s no such thing as a lonely mountain, there can be no such thing as a “selfish gene”. Sobel, in a characteristic flourish on lunar gravity, writes: “The parched moon pulls at earth’s seas as though jealous of them.” Dawkins, a professor of public understanding of science, would riposte: it’s better than no science.
Scientifically, Sobel nevertheless tends to be soberly orthodox. She cites a suggestion that the human body, consisting mostly of water, might also be affected by earth-moon rhythms (I once heard Ted Hughes gravely talking astrological twaddle on this basis). But Sobel insists, as well she should, that the “Moonstruck sensation often evoked in the human breast is best explained as an emotional response to beauty, not a tide of bodily fluids”.
The book’s moment of publication is a little unfortunate. Sobel missed confirmation two months back of the discovery of a 10th planet in our system, even more distant than the planetoid Sedna, discovered two years ago. It is 10 billion miles from the sun, over three times more distant from the sun than its next closest planet, Pluto, and it takes more than twice as long to orbit the sun as Pluto. It awaits a name, so our mnemonics are also due for realignment. And in case you were wondering: Carolyn, as Sobel does not disdain to inform us, has broken up with her astronomer and taken up with a vet.
Available at the Books First price of £13.49 on 0870 165 8585
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websites:
http://pds.jpl.nasa.gov/planets/welcome.htm
Nasa’s guide to the planets
