When I, sitting, heard the astronomer, where he lectured with much applause in the lecture-room,

How soon, unaccountable, I became tired and sick;

Till rising and gliding out, I wander’d off by myself,

In the mystical moist night-air, and from time to time,

Look’d up in perfect silence at the stars.

— Walt Whitman

At last, the eve of the astronomy exam rolled around. The midnight oil had near burnt off, the text of “Universe: The Ninth Edition” began to blur, and the PA system in the library crackled to life: “It is now 1:30. Bass Library will be closing in 15 minutes. 15 minutes.” Time for one last review problem.

(13) A Martian lands on the surface of the moon closest to Earth. (A) What does the Martian see? Describe the surface features and geological composition of the moon. (B) The Third Quarter phase occurred a week and a half ago, what phase is the moon in now? (C) What is the luminosity of the moon in this phase?

Let’s see, surface composition… Well, according to the collision-impact theory, the moon was formed millions of years ago when a small planetary body collided with Earth, kicking up rock and rubble that eventually, by gravity, condensed to form a large orbicular mass in a geosynchronous orbit slightly offline with the Earth’s celestial equator. Over time, through bombardment of meteors and asteroids, various craters and Lunar Maria formed over the surface of the moon. Furthermore, we know the moon orbits the earth over a period of about 28 days. Therefore, there are exactly seven days between the first quarter, full, third quarter and new phases of the moon. Since the Martian landed a week and a half after the third quarter, the moon is likely in the waxing crescent phase.

Okay, A and B, done.

Now, part C … Luminosity? How the heck do I calculate Luminosity? Well, we know the moon has a diameter of 3,476 kilometers, an albedo of .11 and a vastly fluctuating surface temperature from -180˚C to 130˚C …

Suddenly the pounding in my head turned into a rapping at the door of my cubicle. The security guard. Dang, out of time. I shut the book, gathered the loose papers and pencils into my backpack and shuffled out of the library.

Then, as I stepped outside, body stiff, mind numb, there it was: the Moon. Thin wisps of clouds drifted across it, moonbeams falling so thick you could catch them in a jar. The faint outlines of craters and plains faded in and out of the crescent, hinting at the dark portion of the circle. The sense of fall in the air seemed a flirtation. Moonlight drenched the rooftops. Numberless stars chimed in. For a moment, my backpack felt weightless. And while staring up at the first edition of the universe, all the data of “Universe: The Ninth Edition” seemed to fall a bit short.

To the newly landed Martian in problem number (13), the moon is a rock, 3,476 kilometers in diameter, 384,400 kilometers from the Earth. The surface holds no pixie dust, nor is it cheese; it doesn’t even glow. In fact, the surface more closely resembles the Mojave desert than a glimmering porcelain ball. It has an escape velocity and a confusing luminosity. Science can even explain the magical mutations the moon undergoes every night, through all the months of the year. All of these, the Martian on the moon might understand. But from the Earth, from the steps of Bass Library at 1:45 a.m., the moon is also Debussy’s “Clair de Lune.” It’s Méliès’s “Le Voyage Dans la Lune.” It’s the white spot peering out of the ocean in Georgia O’Keeffe’s “Wave, Night.” Its light cloaks Gatsby in his reveries of Daisy. And it’s Margaret Wise Brown’s “Comb and brush and bowl full of mush.” Apart from the facts and figures — likely since before those numbers were even discovered — the moon embodies the endearing, incalculable human appreciation for beauty and romance. And every now and again, when the hour is late, and the air clear, and the thin crescent of white light beams down from the sky, through still leaves, and onto the ground in front of you, the moon is simply lovely. I think even our Martian would agree.