Feature • Amy Leach
There is an altitude above every planet where a moon can orbit forevermore. In millions of miles of ups and downs, there is one narrow passageway of permanence. If a moon can reach this groove, it will never crash down like masonry nor drift away like a mood; it will be inalienable; it will circle its planet at the exact speed that the planet rotates, always over one site, like the Badlands or Brazzaville or the Great Red Spot, so that the planet neither drags the moon faster nor slows it down. Moons not locked into this synchronous orbit are either being perturbed up or down.
The law is stringent about this; there are no clauses; and all moons are dutiful followers of the law. But, as all good followers of the law discover in the end, unless you happen to roll onto a track precisely 18,254 miles above your planet, the law ejects you or dashes you down. One moon in our solar system has achieved synchronous orbit, being pledged forever to its planet—Pluto’s moon Charon. The other 168 moons have not.
Mars has two small moons whose names mean panic and terror. Phobos looks like a potato that experienced one terrible, and many average, concussions. Phobos hurtles around Mars every eight hours, which is three times faster than Mars rotates, which means Mars pulls it back and slows it down. Slowing down makes a moon lose height; in the end Phobos will smite its planet, or else get wrenched apart by gravity into a dusty ring of aftermath. Mars’s other moon Deimos is a slow and outer moon; an outer and outer moon; someday it will be a scrap moon, rattling around in the outer darkness, where drift superannuated spacecraft and exhausted starlets.
So fast moons slow down and slow moons speed up, and only during excerpts of time do planetary dalliances appear permanent. Our moon through many excerpts—the Moon—is a slow moon. Thus it is speeding up, thus it is falling up, coming off like a wheel, at one and a half inches per year. Let us now reflect upon the distancing Moon; for the Moon has long reflected upon us. To get an idea of the relationship between the Earth and the Moon and the Sun, find two friends and have the self-conscious one with lots of atmosphere be the Earth and the coercive one be the Sun. And you be the Moon, if you are periodically luminous and sometimes unobservable and your inner life has petered out. Then find a large field and take three steps from the Earth, and have the Sun go a quarter-mile away.
For an idea of how long your light takes to reach Earth, sing one line from a song, such as “Sail on, my little honey bee,” and that is how long moonlight takes. The Earth can sing the same line back to you, to represent earthlight. “Sail on, my little honey bee.” As for the Sun, he should sing as lustily as sunlight; have him discharge the song “I Gave Her Cakes and I Gave Her Ale,” which is eight minutes long, which is how long sunlight takes to reach the Earth. Also the Earth may sing to the Sun and the Sun to the Moon and the Moon to the Sun, songs of representative length.
Now keep singing and everybody spin and the smaller two of you orbit the next largest rotundity. Now as you, the Moon, go around the Earth, do not circle perfectly, as if you were a mill horse, or an idea. You are not an idea; you make the Earth’s heavy blue waters heave up and down! Circle asymmetrically, then, like a small co-planet; truly you and the Earth both orbit the center of your combined mass, called the barycenter. Of course, if you and the Earth were equal in bulk, the barycenter would lie exactly between you; you and the Earth would pass your lives in social equilibrium, like the rooster and the pig on the carousel. However, as the Earth is eighty-one times more massive than the Moon, the barycenter is eighty-one times closer to the Earth: thus the barycenter is inside the Earth, though not at its center. This means that the Earth orbits a point inside itself. The Earth is a self-revolver, nodding slightly to the swooping Moon.
Now the Earth does not look eighty-one times as massive as the Moon—in fact it is just four times as wide. To address this perceptual difficulty we will interrupt our lunar reenactment and consult philosophy. Let us refer to our index of philosophies and select one known as Interiorism, which says that truth is to be known by introspection. To discover why the Earth acts so central and the Moon so obsequious, let us not measure yards but consider inward differences. The Earth is not gigantic and the Moon is not slight, but the Earth has a core and the Moon does not. Or rather, if the Moon has a core, it is undetectably small and inert, like a frozen mouse.
How do we know that the Moon has a mousy core? Whoever really has been a Lunar Interiorist? Here we shall invent a philosophy and call it Imaginative Exteriorism: wherein, by looking at the exterior, we imagine the interior; for the face often tattles on the heart, and an empty surface may bespeak an empty center (though this is not true of alligator eggs). The Moon has a stony face, while the Earth’s face is a slaphappy burlesque, screaming flocks of peacocks here, and cloudbursts there, and spriggy merriment everywhere. Such an exhibition is possible only if inside itself the Earth has a core whose nickel density enables the planet not only to sport a moon but also to hold onto tiny flighty molecules. For these bouncing shimmying molecules are Earth’s genius, and they are harder to keep than moons. Cloudland has a core of adamant.
On behalf of those who feel vacant and uninhabited, to whom nothing occurs, who look up day and night from chalky dust into unrefracted blackness, who watch their plush blue-headed neighbors yielding splashy gullies and snow devils and excitable vespiaries and backsliding pinnipeds and heady cauliflowers and turtle centuplets and rosy squirrelfish swarming through Rapture Reefs: on behalf of unprofitable individuals everywhere, is the Moon ordained to ever be a shabby waste of rubbled regolith? Could it never scrabble together a genius like the Earth’s?
What about molecule trustees, like the Sun? The solar wind blasts a plasma of particles throughout the solar system; could not some of these particles accrue upon the Moon? For not all atoms are wiggle-away; xenon, for example, is heavy and slow. It would make a nicely noncombustible atmosphere, of glowing lavender hue, and would make sound possible, albeit slow, so everyone’s voice would drop several octaves and everyone would sound like walruses. And xenon is an anesthetic, so inhabitants would be blithe and amenable to dentistry. But the wind that bringeth the elements taketh them away; the atmosphere on the Moon is thinner than the thinnest vacuum we can contrive.
Haloes cannot be affixed to the head with pins and clips. Marañón forests, hosting spinetail birds and purple-backed sunbeams and gray-bellied comets and velvet-fronted euphonias and long-tailed weasels, cannot be administered from without. Glory cannot be administered from without. Glory will only coalesce on a body wherein throbs a fiery, molten, mad-stallion heart so dreadfully dense, so inescapably attractive, that it matters little the circumference of the frame.
Of course if your heart is too fervent, you will become an attractive incinerator, like the Sun, glorious but no pleasure boat. The glory of the Sun is violent and uninflected; its features are all flames and its sounds are all explosions. The Sun is so loud, like a million bombs all the time, that finespun sounds cannot be heard, like birds wading or figs tumbling or the muttering of mathematicians. On the Sun all private qualities disappear into the main loud yellowness.
Nothing makes a sound on the Moon and nothing ever could: not a harpsichordist, not a shattering tureen of mangel-wurzel stew, not the pebble-sized meteoroids that whang down at seventy-eight thousand miles an hour and heat the ground so hot it glows like a little piece of star; not the huge meteoroids that fracture the bedrock, forming craters two hundred miles across, creating new rings of mountains, making the Moon to tremble on and on—since it doesn’t have a sturdy core the Moon is very convulsible; once atremble, it stays atremble. But it fractures and trembles and glows in absolute silence, for sound is like birds and cannot travel without air.
From looking at its face we had inferred that the Moon’s heart is small and dead; but this is not to say that its face has no properties; not even the most stuporous face has no properties. The moonscape is pleated and rumpled, with rilles and ridges and craters and crevices and darknesses and brightnesses. Except for some meteor-made bruises, though, its features have not changed for three billion years; they are memorials of an ancient vim. Once the Moon was welling up from inside, jutting into volcanoes from the force of its own melting, cracking at the rind from its deep inner shifts. Now it wears the same glassy expression eon after eon, like a taxidermied antelope. The Moon is a never-brimming eye, a never-whistling teakettle; and it shadows the very flower of planets.
There are several kinds of orbits in the orbit catalog. One is an interrupted orbit, which describes the path of a dumpling flung from a window; the ground being the interrupter of the dumpling’s orbit. Another is known as an open orbit, where an unaffiliated traveling object gets pulled to another body, curves around it, and flies away never to return, like a minute. It is just a gravitational encounter and it merely redirects the object. The other kind of orbit is where a rock, after ages of streaking obliviously past acquisitive black holes and great gassy moon-catchers like Jupiter, happens to come close to a small motor-hearted globe, close enough to feel its influence, to be drawn closer, to make a circle around it, and another and another, and never thereafter to stop, not for billions of years. Once it was its own and now it is a foundling. This wrapping of the one around the other is called a closed orbit.
In truth the beginning of the Moon is a secret: maybe a piece of Earth broke off and went into orbit; maybe the Moon was begotten by a terrible collision; or maybe it really was a drifter snatched from its onward way. However the Moon began, here is how the Moon will finish: in a billion years the Earth will have nudged it far enough away that it will look fifteen percent smaller; in three billion years it will look smaller still; in five billion years, the Sun will become a red giant and swallow its children up. The Earth’s involvement with the Moon will not last long enough to end.
The disposition of the universe—that crazy wheelwright—designates that we live on a wheel, with wheels for associates and wheels for luminaries, with days like wheels and years like wheels and shadows that wheel around us night and day; as if by turning and turning things could come round right. For the moment, if you are still in the field of feathery grass where you were playing the Moon, you might look back at your footprints. The Sun spins in place so his path is just a point; and the Earth leaves a long ellipse around the Sun; but your path is a convoluted zigzag, for you loop around a looping planet. Your trajectory is something like the trajectory of sea ducks. Little harlequin sea ducks swim over the oscillating waves of the sea, diving down into the cold gray-green waters to unfasten limpets and blue mussels from their rocks, swinging back up into the rough winter waves, the sea itself rolling up and down under the spell of the sailing Moon.
Amy Leach won a 2008 Rona Jaffe Foundation Writers’ Award in nonfiction. She lives in Chicago.
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