The Many Flavors of the Moon

The dominant body of our solar system is, of course, the life-giving sun. And, though we can observe other stars and planets in the night sky, the second-most prominent entity is easily the moon.

Today, we denote a year by the time it takes to orbit our star, but the moon has traditionally been just as important when it comes to marking the passage of time. The English words “month” and “moon” are cognates, as the original definition for 1/12 of a year is derived from the time it takes to go from one new moon to the next. To ancient humans, the sun dominated the daytime sky and the moon the nighttime. Since the sun always appears as a disc, it makes sense that early humans tracked a period by the changing appearance of the moon.

All spheres in the solar system (or any solar system) are constantly half-illuminated by the star around which they orbit. This fact is easy to visualize with the Earth because we experience a portion of lightness and a portion of darkness as we spin. Despite the fact that we usually don’t see half of the moon lighted, it is also constantly 50% light and 50% dark. Somewhat counterintuitively, this constant duality leads to the phases of the moon, in which we don’t continually see the moon half lighted.

All orbs are always half illuminated, half in darkness - graphic by Crash Course

The amount of light we see reflected from the moon depends on the relative positioning of our satellite as it orbits us.

There are four principal phases of the moon: the new moon, first quarter, full moon, and last quarter.

The two easiest points to visualize are the most famous. When the moon rests between us and the sun, the side we cannot see is illuminated. The result for us is called the new moon, where we cannot view it at all. The opposite occurs when the Earth sits fully between the sun and the moon. In this situation, we can see the entire half of the moon that is lighted. This syzygy produces the full moon.

Halfway between new and full is the first quarter, where half of the circle we see in the night sky is illumed. The midpoint between full and new is the third quarter, which produces the same visual as the first quarter. These terminologies are slightly confusing, as the first and third quarters refer to the point in the entire cycle, not the amount of the moon’s face we can see. Moon is at a quarter phase = you can see half its face.

In between the principal phases are the intermediate or minor phases, which combine two attributes to create four different moon states. When the moon is “thickening” in the sky – moving from new to full – we call it a waxing moon. Conversely, when the moon is “thinning” – moving from full to new – we dub it a waning moon. Further, we can divide the amount of moon we can see. If less than half the face is visible, we get a crescent moon. More than half? We call it gibbous, from the Latin gibbus, meaning “humped” or “hunched.” Combining the four, we can have waxing crescent, waxing gibbous, waning gibbous, and waning crescent.

The following graphic and video can help you envision how the moon appears to us, based on where it is relative to the Earth and the sun.

This graphic shows the position of the Moon and the Sun during each of the Moon’s phases and the Moon as it appears from Earth during each phase - graphic by NASA/JPL-Caltech

The first months were a measure of one new moon to the next one.

The synodic month, also known as lunation, is the time it takes the moon to complete one cycle of phases. This period lasts approximately 29.5 days. Early calendars used these lunar cycles to delineate time. Twelve periods of 29.5 days also happen to be fairly close to the time it takes the Earth to orbit the sun (354.36 days versus 365.24 days). However, 11 days on each orbit are enough to throw things easily out of whack, so, when we adopted a solar calendar, the precise lunar month needed to be altered, though we kept the spirit of the past.

In most years, however, the cycles are close enough in length for each year to contain 12 full moons, which means one transpires each month. The 11 days add up over time, though. Every two or three years (seven out of 19, technically), a year is blessed with 13 full moons. When this happens, one calendar month gets two full moons. We call this second monthly occurrence a blue moon.

Blue moon of August 31, 2012 - photo by Cezar Popescu

When people had greater connections to the planet and the cosmos, they pondered the moon more than we tend to today. Indigenous Americans named months and moons based on the events that happened on Earth in conjunction. When Europeans arrived, they adopted many of these names. The various farmers’ almanacs that served as early compendia for humans preserved these nomenclatures.

According to the Old Farmer’s Almanac, each month has a unique moon name:

January: Wolf Moon
February: Snow Moon
March: Worm Moon
April: Pink Moon
May: Flower Moon
June: Strawberry Moon
July: Buck Moon
August: Sturgeon Moon
September: Harvest Moon/Corn Moon
October: Hunter’s Moon
November: Beaver Moon
December: Cold Moon

Some of the connections are obvious; some are less apparent to a modern person. January’s wolf moon comes from the tendency of hungry wolves to howl during the season’s food scarcity. In March, the soil starts to warm, allowing for the return of worms. The pink moon stems from a species of wildflower that tended to bloom earlier than others. Strawberries often arrived in June in North America. Buck antlers typically begin to regrow in July. Waterways in August were often rife with sturgeon. Crops come in during September. Stocking up on game for the coming winter led October to be the hunter’s month. In November, beavers finish their dams for the winter.

Traditional names of each full Moon - graphic by Colleen Quinnell/The Old Farmer’s Almanac

Of course, variations exist for all the months, including some for other continents.

Indigenous populations didn’t just refer to the full moon by these names, but the entire months. So, adding it all up, we can get quite precise about naming our moon states.

For today’s publication date – May 2023 – we’ve gone past the full moon, so the next time we gaze upon Luna we’ll see a waning gibbous flower moon. Earlier this year, you could have viewed a waxing crescent wolf moon. The first quarter worm moon happened on March 30.

The next blue moon will grace the skies on 30 August 2023. Put this date on your calendar, as the blue moon will also be a supermoon. A supermoon appears when the full moon corresponds with the moon’s closest orbit to Earth, called the perigee. This moon will appear larger than others. We could call it the Super Blue Full Corn Moon.

A waxing crescent beaver moon over Kingman, Arizona - photo by Beth Woodrum

BONUS FACT #1: Pink Floyd were wrong. There is no “dark” side of the moon. Instead, we call it the far side. It gets just as much sun as the near side. However, because the moon is tidally locked to Earth it rotates on its axis in the time it takes to orbit Earth once. The result is, standing on our planet, you’ll only ever see one face of the moon. If the moon weren’t tidally locked, we’d see a rotating smorgasbord of facets as the moon cycled through its phases.

BONUS FACT #2: If the new moon places our satellite between us and the sun, and the full moon means we’re between the sun and the moon, and an eclipse happens in those same conditions, why isn’t there a solar and lunar eclipse each month? Eclipses do only occur during new and full moons. They don’t happen on every new and full moon, however, because the moon’s orbit around the Earth is tilted about 5 degrees with respect to the Earth’s orbit around the sun, called the ecliptic. Every so often, the two orbits line up at places we call nodes. When the moon hits a node, somewhere on Earth receives an eclipse, though most of them are partial.

Nodal precession of the lunar nodes as the Earth revolves around the Sun causes an eclipse season approximately every six months - graphic by Nela

Further Reading and Exploration

Moon in Motion/Moon Phases – NASA

Moon Phases: Crash Course Astronomy #4 – CrashCourse

Etymology of “month” – Eytmonline

Full Moon Names – Old Farmer’s Almanac

Blue Moons: When Is the Next Blue Moon? – Old Farmer’s Almanac

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