Before colonization and calendars, Indigenous people used celestial bodies to track the flow of time throughout the year. Here in southwest Virginia, Cherokee tribes of the eastern band of the Cherokee Indians called this place home. The phases of the moon were used to show the passage of time over an approximate month. Each “year” there are approximately 12 full moons. Every tribe had different names for their moons. Take a look at the names they gave our moons- they’re based on seasonal phenomena!
January: Windy Moon
February: Hungry Moon
March: Strawberry/First leaves Moon
April: Duck/Bird Moon
May: Planting Moon
June: Sprouting Moon
July: Corn in Tassel Moon
August: End of Fruit Moon
September: Nut Moon
October: Harvest Moon
November: Hunter Moon
December: Snow Moon
To understand the moon and its cycle, we need to understand our solar system! Our Sun contains 99% of the available matter in our solar system. Having that much mass means that it has a large gravitational pull. When the sun first formed, leftover matter was trapped traveling around it. Some of that matter collided repeatedly, growing in size. At a certain point, it got its own gravity. Having gravity smoothed out its shape, and we got the planets! While the planets were forming, scientists hypothesize that a large asteroid slammed into Earth and knocked off a large chunk of material that later consolidated into our moon.
Lunar Orbit vs the Line of the Ecliptic
Because of the Sun’s gravitational pull, all the planets orbit around it in a single plane. Essentially, our solar system is flat! From Earth, all other planets, the Moon, the zodiac constellations, and the Sun, appear to rise in the east at night and set in the west. This is called the line of the ecliptic. The Moon isn’t perfectly matched up with the line of the ecliptic- it’s about 5 degrees off.
Just like the planets rotate on an axis and orbit around the sun, the moon rotates on its axis and orbits around the Earth. One popular moon myth is that there’s a “dark” side of the moon that humans never see. And to be fair, it’s partially true! Because the moon is tidally locked with the earth, it rotates once with each orbit it completes. So from where you are on Earth, you will see only one side of the moon. If you went somewhere else, you’d see a different “side”.
It takes the Moon 27.3 earth days to complete one revolution, or orbit, around the Earth. This consistent cycle is what makes it such a good calendar! The cycle can even be broken down into smaller units, based on the eight major moon phases. These phases occur because the Moon cannot generate its own light, it reflects light from the sun. So its position relative to Earth and the Sun determines how much of the Moon’s surface is visible to us. As the moon orbits in a counter-clockwise direction around Earth, it will appear to grow for two weeks, and then appear to shrink for two weeks. These periods are called waxing and waning.
A new moon occurs when the moon is between the earth and the sun. That means that the moon and sun appear in the same place in the sky- during the day! We don’t get a solar eclipse every time this happens because of the tilt in the lunar orbit. As the moon grows, it reaches its first official phase, the waxing crescent. Next comes the waxing first quarter moon. It rises around noon and sets at midnight. First quarter may be accurate based on the moon’s cycle, but it feels wrong to call it that because it looks like half a moon! Lastly, we have the waxing gibbous. And then we’ve got a full moon, which rises in the east at sunset and sets in the west at dawn. It is opposite to the sun. It takes around 13.65 days for the moon to get through half its cycle. After the full moon, the moon shrinks to a waning gibbous, waning third quarter, waning crescent, and finally back to the new moon! The waning third quarter moon rises around midnight and sets at noon (opposite of the first quarter).
