by Dava Sobel
LUNACY
During the glory days of the Apollo project, a young astronomer who analyzed Moon rocks at a university laboratory fell in love with my friend Carolyn, and risked his job and the national security to give her a quantum of Moon dust.
“Where is it? Let me see!” I demanded at this news. But she answered quietly, “I ate it.” After a pause she added, “There was so little.” As though that explained everything.
I was furious. In an instant I had dropped from the giddy height of discovering the Moon right there in Carolyn’s apartment to realizing she had eaten it all without leaving a crumb for me.
In a reverie I saw the Moon dust caress Carolyn’s lips like a lover’s kiss. 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 recesses like pixie powder, thrumming the senseless tune of a wind chime through her veins. By its sacred presence it changed her very nature: Carolyn, the Moon Goddess. She had mated herself to the Moon somehow via this act of incorporation, and that was what made me so jealous.
Of course I had heard the old wives’ tales advising women to open their bedroom curtains and sleep in the Moonlight for heightened fertility or a more regular menstrual cycle, but no folklore described powers to be won from the Moon by eating its dust. Carolyn’s deed conjured Space Age magic, undreamed of when her mother and mine were new wives.
I still envy Carolyn her taste of the Moon. In reality I know she is married now to a veterinarian in upstate New York and has three grown children. She doesn’t glow in the dark or walk on air. She has long since lost all traces of that Moon morsel, which no doubt passed through her body in the usual way. What could it have contained, anyway, to preoccupy me all these years?
A few grains of titanium and aluminum?
Some helium atoms borne from the Sun on the solar wind?
The shining essence of all that is unattainable?
All of the above, probably, all rendered the more extraordinary for having traveled to her across 240,000 miles of interplanetary space, in the belly of a rocket ship, and hand-delivered as the love token of a handsome man. Lucky, lucky Carolyn.
The Apollo astronauts themselves did not intentionally swallow any Moon dust, though it clung to them, covered their white boots and space suits with grime, and so climbed with them back into their lunar modules. The moment they removed their bubble helmets, a smell of spent gunpowder, or of wet ashes in a fireplace assailed them. It was the Moon dust, tamely burning in the oxygen atmosphere the men had carried from home. Outside on the airless lunar surface, did the trodden dust give off any odor of its own? Does a tree falling in a forest make a sound if no one hears?
The astronauts judged the dusty surface of the Moon a shade of tan, like beach sand, when they looked at it facing Sunward, but said it turned gray when they turned the other way—and black when they scooped dust samples into plastic bags. The unearthly glare of unfiltered Sunlight bedeviled their color and depth perception, and that of their photographic film as well. Similarly attuned to the light of Earth’s atmosphere, the film formed its own interpretation of the new landscape’s subtle hues and stark relief, so that in the end the men’s pictures betrayed their color memories of walking on the Moon.
The view of the Moon from Earth is no less fooled by tricks of light. How else could the Moon derive its silvery gleam from dust and rocks dark as soot? The dusky markings that draw the face of the Man in the Moon reflect only 5 to 10 percent of the Sunlight that falls on them, and the brighter lunar highlands no more than 12 to 18 percent, making the Moon overall about as shiny as an asphalt roadway. But the rough-hewn lunar surface, sprinkled with ragged particles of Moon dust, multiplies the myriad planes where light may strike and ricochet. Thus the tan, gray, black dust clothes the Moon in white radiance. And seen against the somber backdrop of the night sky, the Moon appears whiter still.
Whiteness defines our image of the Moon, except for those occasions when it hangs golden on the horizon, burnished by added thicknesses of air, or dips into Earth’s shadow and glows red in total lunar eclipse. No one ever seriously believed the Moon looked green in color, only that it resembled a green cheese—a whitish, splotchy wheel of new-made curds, not yet ripe for eating. True, the Moon may turn blue after a volcano sullies Earth’s atmosphere, or be called blue when it becomes full more than once per calendar month, but the reliable whiteness of the ordinary Moon is what grants the idiomatic Blue Moon its air of rarity.
While white light bouncing off the Moon contains every color, Moonshine perceived on Earth mischievously bleeds familiar sights of any color. The full wattage of the full Moon dims in comparison to direct Sunlight, by a factor of 450,000, and so falls just below the retina’s threshold for color vision. Even the brightest Moonlight induces pallor in each face it illuminates, and creates shadows like oubliettes, where all who enter disappear.
The wan colors of Moonbeams bloom in Moon gardens planted with lilies, angel’s trumpet, sweet rocket, and the like, all of them white or nearly so, or prized for their nocturnal habits. The giant Moon flower, evening’s answer to the morning glory, opens its white petals at day’s end, as do its companions the four-o’clocks, the vesper iris, and the night gladiolus. Evening primrose also finds welcome in Moon gardens, despite pink blossoms, because the primrose wafts its perfume after dark.
The Moon itself refuses to be confined to the night. It spends half its time in the daylight sky, where many people take no notice of it at all, or mistake it for a cloud. Only for a few days each month does the Moon truly vanish, rendered invisible in the vicinity of the Sun. The rest of the time the inescapable Moon changes shape by the hour, waxing and waning and whining for attention.
The first sight of the young Moon arrives as a smile at twilight. Though only the slimmest sliver of silver crescent shines on us this early in the Moon’s monthly cycle, the rest of the Moon reveals itself in just-discernible form, as though the old Moon were lying in the young Moon’s arms. Leonardo da Vinci, sketching the Moon at such a time, recognized the faint light cupped inside the bright crescent as Earthshine. The phantom Moon, Leonardo explained in the crabbed, left-handed mirror writing of his notebooks, catches the Earth’s reflection of the Sun, and beams back an attenuated echo.
By the time the Moon moves one quarter of its way around the Earth, the Sun’s light covers half the Moon’s face, like the icing on a cookie with precise hemispheres of chocolate and vanilla. Soon the terminator—the day-night line—arches like a bow, and still more of the lunar surface lights up as the Moon gains its gibbous phase. These stages of lunar expansion, unfolding from the dark of the Moon through crescent, quarter, gibbous, and full, promise growth. Herbals and farmers’ almanacs commend the waxing phases as proper times for sowing peas, harvesting root crops, and pruning trees to assure abundant fruit. Timber, however, by the same token, must never be taken in a waxing Moon, because wood wet with rising sap will resist the saw, requiring harder work, and after cutting it will warp.
The full Moon rising at Sunset raises an illusion of grandeur that doubles or triples its apparent size. The splendor of this sight derives from the mind’s own sense of the horizon as a faraway place where anything that looms large must be huge indeed. Later on in the night, once the Moon has ascended the sky, where a different distance scale applies, the Moon resumes its normal dimensions, though the world below be mad. Dogs bay, coyotes howl, lycanthropic men morph into werewolves, and vampires prowl under a full Moon. More crimes are committed, more babies are born, more lunatics run amok. Or so some claim, since the full Moon’s startling light, almost bright enough to read by, sustains a prevailing expectation of mayhem.
Every full Moon of the year has earned at least one name tying it to lost seasons of tradition—Wolf Moon, Snow Moon, Sap Moon, Crow Moon, Flower Moon, Rose Moon, Thunder Moon, Sturgeon Moon, Harvest Moon, Hunter’s Moon, Beaver Moon, Cold Moon—though no such tributes apply
to any of the Moon’s other phases.
The state of technical fullness, when the Moon stands opposite the Sun in Earth’s sky, lasts only a minute in the monthly life of the Moon. A moment later, as the Moon yields to decline, darkness encroaches from the right, retracing the path of the previous light. One by one the features drop from the face of the Man in the Moon—or the rabbit in the Moon, or the toad—in the same order they showed themselves before. First to come or go is high, round Mare Crisium (the Sea of Crises), followed, as in some fantastic Latin incantation, by Lacus Timoris (the Lake of Fear), Mare Tranquillitatis (the Sea of Calm), Sinus Iridum (the Bay of Rainbows), Oceanus Procellarum (the Ocean of Storms), Palus Somni (the Marsh of Sleep).
Nothing could summon water from those dark seas of the Moon because they are, all of them, dry. Nor have the Moon’s so-called seas ever known the presence of water. Though the lunar maria hinted of a fluid interconnectedness to the first astronomers who eyed them and named them through telescopes, the first Moonwalkers to tread them retrieved the driest imaginable materials from their shores.
“Bone-dry,” the lunar samples were described, though they are much drier than bones, which form inside the Earth’s wet living systems, and retain the memory of water long after death.
Dry as dust, then? No, drier still. On Earth, even dust holds water.
Moon rocks set a new standard of dryness, distinguished by the total absence of water. Not a drop of water, not a bubble of water vapor lurks in the crystal lattice of any Moon rock among the lunar samples, and no ice ever so much as touched them. Comets, however, have probably tucked odd caches of imported water ice—perhaps ten million tons’ worth—in the shadows of unexplored craters near the lunar poles.
Lacking water as a potential ingredient limited the Moon’s creativity to a mere one hundred minerals, while the moist Earth has fabricated several thousand mineral varieties. The gems romantically or religiously associated with the Moon—pearl, quartz, opal, moonstone—could never have formed there, for each requires water in one way or another, and the Moon has none to offer.*
The primal lunar scenario currently favored by planetary scientists explains the Moon’s formation and dryness in a single blow: Early in the history of the Solar System, a rogue planet on a collision course struck the infant Earth. The impact, thought to have occurred 4.5 billion years ago, melted impactor and impact site alike, and shot hot debris into space. Swarms of dust and rock fragments, lofted into orbit around the stunned Earth, eventually reunited, 4.4 billion years ago, as the Moon. Having been ejected from one common cauldron, Moon rocks chemically resemble Earth rocks, except that they have lost all their water and any other compounds capable of escape as vapors.
The furious pace of lunar assembly generated enough heat to melt the top layers of the new satellite into a global magma ocean, one hundred miles deep. Over time that ocean gradually cooled and hardened to stone. The errant rubble of the Solar System’s violent youth, still at large then, bombarded the Moon’s smooth new crust, blasting out vast impact basins and craters. Meanwhile radioactive heat trapped inside the young Moon drove more molten rock to the surface, to fill broad basins with black basalt—and paint the Moon’s facial features.
The all-encompassing ocean of magma attending the Moon’s birth was the first fluid to flow there. The rivers and pools of extruded lava were the last, and those froze up three billion years ago. At that time, the rate of cratering tapered off throughout the Solar System, and the Moon, having expended all its internal heat, solidified through and through, turning into a dry fossil generally considered “dead” by geological standards.
The parched Moon pulls at Earth’s seas as though jealous of them. Twice each day the ocean tides rise and fall to the call of lunar gravity. The waters rise once when they pass beneath the Moon, which makes intuitive sense, but then they rise again after they have been twirled round to the other side of the world, where they face away from the Moon. There you might say they only appear to rise, when really the Earth is being pulled out from under them by the tug of the Moon. Looking at the whole world’s waters at once, the ocean directly under the Moon rises in response to the stronger tug of gravity there, while the ocean on Earth’s opposite side simultaneously rises as though relieved to feel so little force pulling it in the opposite direction.
Earthly tides answer to solar gravity as well as lunar, but not as much so, for the Sun’s greater distance, and its tendency to pull more equitably on all parts of the Earth at once, diminishes its effect on the tides. When the Sun and Moon align with the Earth in a straight line across the heavens, however, as they do at new and at full Moon, then the three bodies conspire to make tides rise higher. Such “spring tides,” which occur in every season, take their name from the rush of waters that may leap as much as twenty feet, twice in one day. Should the spring-tide lineup, or syzygy, occur with the Moon close to Earth, at perigee, then so much the higher for the tides.
Some swear that the same strong tides of lunar attraction can hoist a person’s inner parts skyward, too. Why shouldn’t the human body, consisting mostly of water, heave in synch with Earth-Moon rhythms? Probably because it’s too small. Just as the small bodies of water in lakes and ponds fail to respond to the Moon in tides, so, too, do small living bodies of water bow out of interplanetary interactions. Therefore the Moonstruck sensation often evoked in the human breast is best explained as an emotional response to beauty, not a tide of bodily fluids. Likewise the match of the female menses with the lapse of the lunar month must be either a coincidence or a mystery.
Even as the Moon draws the oceans to and fro, the Earth drags down the Moon with the superior force of its greater mass. The uneasy power struggle between the bodies has slowed the rotation of the Moon to about ten miles per hour. Spinning this slowly, the Moon takes as long to turn once on its axis as it takes to complete its monthly 1.5-million-mile orbit. The Earth has thus coerced the Moon into a lock-step pattern of rotation and revolution, called “Earth-lock,” that keeps the Moon’s same awestruck face trained Earthward at all times. No wonder the man in the Moon looks so familiar.
Compared to the Moon, the Earth spins like fury, rotating one hundred times faster. Yet the Earth, too, is decelerating, by a few millionths of a second annually, under the strain of tidal friction. For the Moon’s noticeable effect on ocean tides is accompanied by an insidious stretching of the Earth’s solid ground. The Moon pulls hardest on whatever part of Earth is nearest, actually raising a bulge. But no sooner has some expanse of Earth’s surface risen in response than the Earth’s rotation wrenches that region out from under the Moon, and rolls a neighboring area there instead. With some section of the planet always bulging and then subsiding, the constant friction stays the pace of rotation.
As the Earth slows, the Moon drifts an inch or so farther away each year, since the cascade of tidal effects gives a slight boost to the satellite. Eventually the Earth’s slowing down and the Moon’s slipping away will end in a standoff that stabilizes the Earth’s rotation and halts the Moon’s retreat. At that point the rotation of both bodies will be synchronized: Earth will eye the Moon with the same wary, one-sided gaze the Moon now fixes on the Earth. Moon worshipers in that distant future will no doubt dwell on the half of Earth where the Moon hovers overhead all the time, while any remaining inhabitants of Earth’s other hemisphere, “the far side,” will need to journey as much as halfway around the world to get even a glimpse of the Moon.
For now, the almost imperceptible decrease in the Earth’s rotation amounts to a mere millisecond every fifty years. But this and other inconstancies have convinced official timekeepers to improve on the Sun, Moon, and stars as reliable standards, and occasionally to stitch an extra “leap second” into the worldwide calendar year. Unlike a leap year, which lasts a day longer than a typical year, a leap second measures the same fraction of time as any other second. But just like the leap year, the leap second sings the frustration of all recorded efforts to base
a calendar of human affairs on the motions of the heavenly spheres.*
The Earth’s daily turning on its axis and annual revolution around the Sun refuse to mesh easily with the Moon’s monthly orbit. Combining solar and lunar time cues has ever demanded elaborate formulae for alternating between twelve-month and thirteen-month years (which long ago made the number thirteen unlucky), or for legislating the duration of the months themselves. The mnemonic doggerel of “Thirty days hath September” quickly loses its rhyme and meter in the struggle to fit a requisite number of days into months that will tally with seasons through years to come.
Even though an atomic clock keeps better time than the dance of the planets, nevertheless it is the clock that must be readjusted accordingly, and yield to the authority of the imprecise orbs. For what good is the smug ability to judge the Earth a second short in her timing if spring comes when it will?
On the Moon, a single time span—our lunar month—serves for day and year alike. Over the course of this daily year, as the Moon turns on its axis and around the Earth, Sunlight and warmth spread first over one lunar hemisphere and then the other, granting each about two weeks of continuous daylight, to be followed by the frigid two-week night.
Many think of the far side of the Moon as the dark side, on account of its being perpetually hidden from Earth, but it, too, goes through phases, which complement the fully or partially lit phases we observe on the near side. Just as the Sun’s light bathes half the Earth all the time, so, too, does it illuminate the sphere of the Moon.
Apollo astronauts who walked on the Moon landed on the near side in the early lunar morning, before the temperature rose to its noon high of 225 degrees Fahrenheit. Even the last two Apollo crews, who sojourned on the surface for an elapsed mission time of three days, came and went within half a morning on the Moon.
