Cycling through phases of moon in month’s time


By Tom Burns - Stargazing



I have never much liked our New Year’s Eve celebrations. The new year is supposed to be a time of renewal and rebirth, but the middle of winter seems a poor time to do it.

Earth’s orbit around the sun roughly determines the length of the year. However, there is no magic tick mark on Earth’s orbit to indicate when the new year begins. Our choice of Jan. 1 is purely arbitrary.

On the other hand, the phases of the moon clearly — albeit roughly — articulate the passage of a “moonth.” (Hey, where do you think the word “month” comes from?) That’s why our first human ancestors measured the long-term passage of time in months, not years.

As long as we have walked on the planet and stared upward at the sky, humans have noticed that the moon follows a predictable path across the sky. And we noticed that the moon has phases over about a 29-day cycle.

The moon’s orbit around our planet causes that cycle. The moon does not shine with its own light; it reflects the light of the sun. We see different moon phases because we view its illuminated face from different angles as it orbits Earth.

The cycle begins with the new moon, which most people have never greeted with much enthusiasm. On that night, we see only the moon’s non-illuminated face. Luna rises around sunrise and sets with the sun, so we don’t see it at night. In effect, “new moon” means “no moon.”

Crusty old curmudgeons like me love those nights when the moon does not shine in the sky. I have spent decades of my life as a proud “deep-sky observer.”

As such, I attend carefully to the phases of the moon. Luna’s harsh brightness washes out the subtle light of emission nebulae, where stars are born and die, and distant galaxies of stars.

I recall a backpacking acquaintance of mine who preferred the nights when the moonlight illuminated his nocturnal activities outside his tent.

However, the new moon is one phase that amateur astronomers treasure dearly. The light from distant suns shines unimpeded by the big streetlight in the sky.

During the week after the new moon, Luna is up in the early evening sky and sets a bit later each night. The first few days after the new moon are golden times. A quick look at the setting crescent moon can be followed by a long, glorious night of telescopic observing.

At the end of the week, we see a half moon. That phase is more correctly called the first-quarter moon because it occurs one quarter of the way through the lunar cycle. Looking like a half-eaten pepperoni pizza. It doesn’t set until the night is half over.

Deep-sky observers must wait impatiently until the moon sets, and that makes for bleary-eyed activities the next day.

The next phase is miserable indeed. The moon is up in the early evening and stays in the night sky, growing fatter and fatter. During this “waxing gibbous” phase, most stargazers stay home and polish their telescopes.

At the end of the week, the moon reaches its full, or “second-quarter,” phase.

The night of the full moon is great for courtship and nighttime hiking but lousy for stargazing. The moon rises around sunset and sets around sunrise.

By about a week later, the moon has shrunk again to half its size. The “third-quarter” moon doesn’t rise until the night is half over, so telescopists can get in a little early evening observing and be home early enough to get a few hours sleep.

Over the next week, the moon continues to shrink to a smaller and smaller crescent and rises later and later. On the night of the “new moon,” Luna again disappears from the night.

Of course, the moon’s light is useful for other nighttime activities besides night hiking.

In the days before streetlights, many a poet has waxed poetic about the full moon. Many a lover’s liaison was lit by “the light of the silvery moon,” as the old song goes.

The new-moon night means that such activities must wait. Who wants to go stumbling out in the dark? As the 9th century Japanese poet Ono no Komachi writes,

“The night of no moon,

There is no way to meet him

I rise in longing

My breast pounds, a leaping flame,

My heart is consumed by fire.”

Many people have stared at the full moon with fervent awe. Witness our media-induced fascination with the so-called Supermoon. It differs little from any other full moon, but we rush out to see it in a PR-induced frenzy.

Naturally enough, we look at the full moon’s radiance and see things in its dark markings, called maria, the Latin word for “seas”.

In the United States, we mostly have been trained to see the man in the moon, and I’ll trace his origin next week.

However, most cultures around the world have identified the moon with a woman and not a man.

Our ancient forebears saw the moon as a goddess whose light brought fertility to the world. She made the crops grow, and her light brought beauty to the faces of our loved ones when they bathed in her brilliance.

It’s far easier to hunt at night if the light from the moon illuminates the ground below. Thus, the Greeks and Romans identified the moon as Diana, the huntress. The technical name for our moon is Luna, which hearkens back to her Roman name.

The earlier Greek equivalent was Selene. Since the crescent moon resembles the yoke of a chariot, Selene is often depicted as driving her lunar chariot across the sky,

Selene represents youth and fecundity. Her union with the mortal shepherd Endymion produces 50 daughters. Her light —and not the light from the sun — makes the crops grow.

The belief in lunar light’s fecund power is not limited to western culture. When I was in India many years ago, I heard of it from a woman who was giving us a tour of a local Hindu temple.

She said that Hindu women sometimes lay a bowl of milk under the light of the full moon. They believe that bathing in that milk will keep them eternally beautiful. Drinking the light-infused milk will make them capable of bearing many children.

South Seas islanders also see a woman in the moon. Sometimes, she forms the clouds out of her brilliance.

Her husband, the sun, forever pursues her. They feel each other’s caresses only on the rare occasions when they are brought together during what we ignorant modern folks call a solar eclipse.

As the moon blocks the sun, the activities of the two celestial bodies are shrouded in darkness. Suffice it to say that the sun’s corona becomes briefly visible, and there is no greater glory visible to human eyes.

Often, a few stars appear during the relative darkness of an eclipse. And thus it is that the mother moon gives birth to the stars.

Some of those same island people believed that the moon’s phases reflect the cycle of pregnancy and birth. As the moon grows larger, her child grows within her. At the full moon, she is ready to give birth.

She then enters into a protracted 14-day labor, at the end of which she always dies. For a day, no moon lights the sky, and people mourn her death. But the next day or the day after, her child appeared in the sky as a thin crescent, and the cycle begins anew.

If cosmic ardor burns in your heart, I hope you’ll go out and observe that baby moon two days after the new moon.

This month, the new moon — the night when the moon lies hidden — is tomorrow, Jan. 13. Two days later, during the evening twilight of Jan. 15, you can observe the beautiful, shard-like sliver of the two-day-old moon.

Look low in the western sky near the place where the sun has just set. As twilight darkens into night, you might be able to glimpse the newly born child.

She will look, as Chet Raymo writes in The Soul of the Night, “crooked like Cupid’s bow, its arrow aimed at the sun.”

So go out and look if the sky is clear. After all, a lovely, ancient goddess has destroyed herself to give birth to that newborn splendor. Let us not fail to note her passing and revel in the new life.

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By Tom Burns

Stargazing

Tom Burns is the former director of the Perkins Observatory in Delaware.

Tom Burns is the former director of the Perkins Observatory in Delaware.