Mulling the Mystery of the Moon
Awash in sunlight six months ago, I wrote a column on the source of the summer solstice--the sun. Now that Sol seems to have abandoned us for the winter, it seems fitting to focus on a more faithful celestial body, the moon.
Orbiting the earth in an egg-shaped path, the moon is 221,461 miles away when it's closest to us. Theoretically then, if 1) there was a road to the moon, and 2) you had a cream puff of a new car, you could drive there on one engine.
The moon, a natural satellite that orbits the earth, has a diameter of 2,159 miles. If you were to take a lunar rover for an around-the-moon drive in a straight line, the odometer would click off 6,790 miles before you met your tracks again. Although its mass is only 1/81 the that of the earth, the moon exerts quite a pull on our planet, as is evidenced in the tidal swelling of Earth's oceans.
Although the moon rotates, we always see the same face of the moon. Like a couple who clasp hands and spin about the dance floor while never losing eye contact, the earth and the moon are in a "captured rotation," because the moon always rotates in exactly the same amount of time that it takes to revolve around the earth.
This time, called the lunar cycle, is 29 days, 12 hours and 44 minutes. The lunar cycle begins with the new moon. The new moon occurs when the moon sits between the sun and the earth. Because it reflects no sunlight toward the earth, we can't see a new moon---which rises and sets with the sun---except during an eclipse.
A fingernail-clipping crescent moon materializes a few days after new moon, appearing to tag closely behind the sun as it progresses along the sky.
Like a string dipped into hot wax, the moon grows larger (waxes) following the new moon, rising about 50 minutes later each day. By the first quarter of the lunar cycle, this lag in rising makes the moon appear directly overhead when the sun is setting. At first quarter we see the moon half illuminated, with a straight-line boundary between dark and light.
From the half moon of first quarter, the moon continues waxing into a pregnant, gibbous moon (from the Latin word for "bulging), as it nears the midpoint of the lunar cycle, full moon.
The impossible-to-ignore full moon, stationed on the opposite side of the earth from the sun, reflects light off its entire visible surface. The full moon rises in the east as the sun sets to the west, traveling all night across the sky until the sun rises the next day.
After the full moon lights up the night, it appears to shrink during the waning half of the lunar cycle. By the last quarter, a half moon appears overhead at sunrise and is chased over the western horizon by the sun at about midday. From there, the visible moon reduces to a crescent, which is quickly followed by a new moon as the 29-day cycle begins anew.
Because the lunar cycle is a bit shorter than most of our calendar months, we're occasionally treated to two full moons in a single month. The next "blue moon," or second full moon in a month, will occur on July 30, 1996. Because July isn't the best moon viewing time in Alaska, we'll need to wait until early 1999, when full moons will appear on January 2 and 31. Also in 1999, February will be robbed of its full moon, as it was in 1866, 1893, 1915 and 1980.
But maybe a month without a full moon won't be so bad, especially if you believe what scribes such as William Shakespeare have expressed for centuries. From Othello: "It is the very error of the moon; She comes more near the earth than she was wont; And makes men mad."
