A just-right satellite

THE other night, while on a walk, I stopped to admire the reflection of the moon in a roadside puddle. It lay pale and hazy, staring up through reflected leaves. When I compared it to the moon shining down directly, offering a different kind of beauty, the obvious fact occurred to me that we are remarkably blessed in having just the kind of moon we do. We didn't have to have one, neatly balancing our one sun. We could have 17, like Jupiter, cluttering the sky with an array of night lights -- or none, like the inner planets, Mercury and Venus, leaving us in mere starlight at night. Or we could have bands of rings, like Saturn, shadowing portions of the earth and so cooling those areas that life as we know it would be rendered difficult or impossible. We could even have two ungainly moons, like Deimos and Phobos, which circle Mars. Small and low to the planet, they are probably captured asteroids, and exhibit none of the spherical beauty with which our moon graces the sky.

Somehow it seems right that our planet, which we now know moves in space like a lovely blue ball, marbled by continents and shaded by endlessly changing cloud patterns, should have such a reasonably sized and orbitted satellite.

With the possible exception of the anomalous Pluto, no other planet in the solar system has a moon as large, relatively, as ours, which has a diameter of 2,160 miles and a volume just 2 percent of that of the Earth. While small, it is big enough to raise our moderate tides and cause Earth to wobble in its orbit the way a parent has to lean back to swing a child around by the arms.

Were it much larger, the moon would lift tides that would scour the shores of our seas twice a day. Being the size it is, and because of its comparative closeness, an average of 238,866 miles away, it is clearly not a spot of light but a visible globe, and is generally agreed to have aroused much of man's early interest in the nature of his heavens. Today even field glasses reveal its craters, maria, and mountains. In 1609 Galileo first saw these features through his telescope, and realized that the moon was indeed a world with a surface like that of Earth.

The presence of a moon so easily viewed, with its starkness, its brilliant coldness, makes our own planet, rich with water, atmosphere, life, moderate temperatures, and reasonable seasons, that much more astonishingly marvelous in our eyes.

Edgar Allan Poe, in his ``Sonnet -- To Science,'' objected to contemporary scientific study by asking, ``Hast thou not dragged Diana from her car?'' One hardly thinks so. The fact that people have now been to the moon, and printed human tracks on its bleak surface, and that those voyagers have returned to live quite ordinary lives among us, is cause for a wonder Poe never could have experienced.

Nor are the moon's varied phases, and the changing beauty of moonlight, diminished to us by a greater knowledge of our satellite. Apparently growing from a wisp of eyelash to a full disk, with its vague, slightly astonished image of a face, which vanishes before a harder look, the moon pours its pearly light onto houses, fields, and water; sifts it through the clouds, dreamy and restful, glorifying the faces of our friends, coloring our night-freed thought, giving us a vision of beauty wholly different from that of sunlight. It illuminates thousands of poems and has taught us of loneliness and of independent reserve. Its reliable orbits help us subdivide the year and instruct us in obedience to law.

Surely one need not claim that our one moon, so nicely sized, so precisely placed, is there solely for the contemplations of mankind. But it is there and, being there, has remarkably enriched us. One can imagine other kinds of interesting satellites, but we certainly have been conspicuously provided for with just the one we have.

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