In this series, we've traversed the cosmic landscape, exploring many celestial bodies, including some like the oft-featured Saturn multiple times. It's high time we turn our gaze to Earth's closest celestial companion—the Moon. Our only natural satellite. The Moon has been our loyal companion and held our planet as the center of its world orbiting us for billions of years, subtly and profoundly influencing our planet.
Let's begin our lunar exploration with its name. Unlike celestial bodies named after Roman gods, the Moon's moniker seems mundane, especially as it's a term used for all natural satellites. Yet, this wasn't always the case. Ancient Greeks knew it as Selene, and to the Romans, it was Luna, both goddesses driving a silver chariot across the heavens.
Selene, Greek goddess of the moon, in a flying chariot drawn by two white horses. from, "Flora, seu florum...", Ferrari 1646
There's something special about being "The Moon" the archetypal moon which we compare all other moons to. The Moon’s name is derived from Old English mōna which shares roots with Latin metri, meaning to measure. Hence, our language uses the Moon as a fundamental measure of time. A "month" coming from Moon with the suffix -th "moonth", the suffix -th denotes a measurement (i.e. 1/4th cup, 100th place etc.) so one “Moon-th” (month) corresponds roughly to a lunar cycle (phase to phase of the moon or, one measurement of the moon).
Our modern Gregorian calendar, designed by pope Gregory XIII to keep Christian holidays in sync with the seasons, is solar-based and slightly off from lunar measurements. However, lunar calendars persist in other cultures to this day. For example, the Islamic Hijri calendar begins each month with the new moon sighting. The Hebrew, Chinese, Hindu, and Buddhist calendars are lunisolar, reconciling lunar months with the solar year. They all use some mechanism to adjust the months allowing festivals to occur in the expected season while still maintaining lunar based months.
"If you want to get older go to Korea" Korea mostly uses the Gregorian calendar however for cultural events like holidays and birthdays it's not uncommon to use a lunar calendar that starts with babies being considered to be one when they are first born.
Throughout history, many cultures have assigned names to the full Moon of each month, often related to the natural world, seasonal changes, or animal behavior. One of the most well-known sets of full Moon names comes from Native American tribes, particularly the Algonquin tribes of northeastern North America. These names were later adopted and popularized by colonial settlers and have become widely used today.
Here's a brief explanation of some full Moon names and their meanings:
Wolf Moon (January): Named for the time when wolves were heard howling in hunger, due to the scarcity of food during the cold winter months.
Snow Moon (February): Named for the typically heavy snowfall that occurs during this month in many regions.
Worm Moon (March): Named for the appearance of earthworm casts on the ground as the soil begins to thaw, signaling the return of spring.
Pink Moon (April): Named after the pink flowers called wild ground phlox, which bloom in spring and are one of the earliest widespread flowers of the season.
Flower Moon (May): Named for the abundance of blooming flowers that brighten the landscape during this month.
Strawberry Moon (June): Named for the time when strawberries are harvested in North America, particularly by Native American tribes.
Buck Moon (July): Named for the time when new antlers begin to grow on male deer (bucks).
Sturgeon Moon (August): Named for the time when sturgeon, a large fish found in the Great Lakes and other major bodies of water, were abundant and easily caught.
Harvest Moon (September): Named for the time when crops are typically harvested, and farmers work late into the night under the light of the full Moon.
Hunter's Moon (October): Named for the time when game is fattened and hunted in preparation for the winter months.
Beaver Moon (November): Named for the time when beavers build their winter dams, and also the time when trappers set their beaver traps before the swamps froze.
Cold Moon (December): Named for the arrival of cold weather and the beginning of winter.
It's important to note that these names are not universal, and different cultures around the world have their own names and traditions related to the full Moon. While the Native American and colonial names are widely recognized in the United States, other countries and cultures have their own unique sets of names reflecting their local customs, beliefs, and natural phenomena.
One of the Moon's intriguing aspects that we often get asked about is its synchronous rotation. As the Moon orbits Earth, it rotates at the same rate, ensuring one side always faces us. It is thought that this "tidal locking" happened over time as Earth's gravitational pull slowed down the Moon's rotation. In turn, the Moon is slowing Earth's rotation, lengthening our days.
To see how this works, get 3 friends together to do the cosmic dance of the Moon, the Sun, and the Earth. Each friend will play different parts the sun friend will stand in one place the whole time and shine a flashlight on the faces of the other two friends the friend that is playing Earth stands a few feet away from the sun and stays in one place and is free to prewett (spin in place) as much as they please, finally the friend playing the moon must circle the earth passing between the sun and the earth once every rotation but must also be facing the person playing the earth.
Starting with all dancers in alignment; the Moon to the furthest left, the Earth in the middle and the Sun to the right this is the alignment at full moon: the light of the sun illuminates the Moon's full face as seen by Earth.
Now have the Moon orbit 90 degrees in a circle around the person playing the Earth, now the Earth sees half the moon’s face illuminated. This represents one week of rotation of the Moon (the Moon takes about 4 weeks to circle the Earth entirely) this is called “last quarter”.
Now again have the Moon shift another 90 degrees in a circle (180 deg total from where they started) around the Earth while still looking at the Earth. Now you should have a line up of the moon in the middle and the earth furthest left and sun furthest right. This represents the “new moon” (about 2 weeks after full moon) from the Earth’s perspective; the Moon's face is not lit up at all by the sun’s flash light. However, note that the back side of the moon’s head is illuminated by the flashlight. This is why it’s the reverse side of the moon (not the dark side, unless you’re a pink floyd fan) as the other side of the moon is illuminated during the new moon you just can't see it from earth.
Have the Moon continue to move 90 degrees again around the Earth and see the other half of the moon’s face illuminated as seen by Earth this is “first quarter” (about 3 weeks from the last full moon).
Then Finally have the Moon move the last 90 degrees to be back to where they began at the far left with the earth in the middle. This is full moon again and represents one full rotation of the moon.
You can see how from the perspective of the sun the moon has done one full rotation as the sun has shined on each side of the moon. If you lived on the moon you would experience days they would just be about as long as a month as the moon is “tidally locked” to the Earth meaning it’s day is the same length as its rotation around the Earth that is why we always see the same face of the moon.
When the Moon first formed it is thought that it would rotate but because the Earth is so much larger than the moon the Earth slowed it down until it showed us only one side becoming “tidally locked”. Similarly the moon is slowing down the earth turning about 250 million years ago Earth was spinning so fast that our days were only 22 hours long. This can be seen in the fossil record where coral from the Devonian and Pennsylvanian periods can be seen with both daily and yearly growth patterns. Looking at these growth patterns it looks like there were 400 days in the year 250 million years ago, since there hasn’t been much evidence of any difference in the yearly rotation of Earth around the sun. It's thought that 250 million years ago the Earth had 400 twenty two hour days a year
The Moon is a quarter the size of Earth with a diameter of approximately 3,474 kilometers (2159 miles, or about the driving distance from Kansas City MO to Los Angles CA). The moon is easily observable from anywhere on earth due to its proximity and brightness; it can even be observed in some of the most light polluted areas. Because of this it has inspired our humanity since the dawn of culture, every culture has a story about the moon. Many stories are about the rivalry between the Sun and the Moon or how they are different spirits that race across the sky and consume each other.
If the Moon was placed directly over Denver. luckly it's 230,000 miles away as this would mess up the tides really bad.
Though smaller than Earth, the Moon's impact on our planet is immense. Its gravitational pull causes the ebb and flow of the tides, and even land tides by pulling on the earth’s crust it can raise the ground beneath your feet letting us experience tides even in land locked Colorado.
The moon also has many interactions with the natural world as it tidally pulls on water tables having effects on plant life. Full moon nights are also useful for nocturnal animals such as the coyote who hunts at night and because the full Moon provides better visibility they are more active on nights where the moon is brighter (this is what has been the inspiration behind the mythical werewolf, or why coyotes are often depicted howling at the moon). Researchers in Australia are even using the lunar cycles to save the great barrier reef. When propagating coral in a lab to seed rehabilitation of the great barrier reef researchers found it works a lot better if the lights are set up in a complex way to mimic the phases of the moon.
It has even been theorized that the moon is responsible for life as we know it here on earth. The complex tides the moon creates on earth might have been the push life needed to get out of the ocean and start evolving on land. You can witness the Moon's effect on our evolution just by going to a dark area on a full moon night, the full moon is about half a million times dimmer than the sun (even if you filled the sky with full moons it wouldn’t be nearly as bright as the sun) but you can see perfectly fine out on a full moon hike and that is because our eyes are well adapted to life here on Earth and the range of light provided by the Sun and Moon.
The Moon's surface is surprisingly dark when observed up close. The surface of the Moon is illuminated by reflecting the light of the sun. However, the Moon only reflects 3% to 12% of the Sun’s light looking at moon rocks in museums; they appear black to gray, but in contrast to the black night sky the moon appears bright white.
Dark matrix breccia from Van Serg cratering ejecta collected by Apollo 17 (sample 79135)
Very near the new moon you can see “Earth glow” on the Moon. A day or two after the new moon, go outside and look at the moon just after sunset. You will see the sliver of the moon holding a ghostly illuminated side of the moon; this is the “Earth glow”. The bright crescent is illuminated by the Sun of course but the rest of the Moon that you can see ghostly is being illuminated by the reflection of light from the Earth. So that’s light from the sun bouncing off the Earth going to the moon to light up the side in darkness and bouncing back off the Moon back to the Earth so you can see it. If you were on the Moon during Earth glow it would be similar to being on the Earth during a full moon but brighter. You would see the earth light up your night sky like the full moon does on Earth but because the Earth is bigger and more reflective than the moon the Earth would light up the landscape much more.
Moon setting over ESO’s Paranal Observatory in Chile where earth glow is visible
Our understanding of the Moon and the solar system's formation is largely based on the Giant Impact Hypothesis, suggesting a Mars-sized object (called Theia) collided with early Earth, and the resulting debris later coalesced to form the Moon.
The Moon's surface divides into two regions: the cratered highlands and the lava flow lowlands. It's pockmarked with craters, remnants of countless meteor impacts. The largest, the South Pole-Aitken Basin, measures an impressive 2,500 kilometers. The dark "seas" are lower basins filled with lava from when the moon was geologically active.
The majority of the cratering on the moon is thought to have come from the bombardment periods of the solar system's history (a turbulent time in the solar system's history where meteors and collisions were frequent). All the meteors and impacts in the early history of the moon brought lots of heat to the moon. The moon got hot enough to have a molten core that eventually broke the surface of the moon as lava creating the dark seas.
This gives us insight to the history of our solar system that you can see just by looking at the moon. You look at how the dark “seas” on the moon cut up the cratered regions showing that the “seas” are more recent then examining the “seas” with a telescope or binoculars you can see very few impact craters on top of the lava flows. showing there was an early period of lots of meteors followed by a comparatively calm peaceful time of few impacts. The “dark” or far side has remained a mystery to us until the advent of space exploration and examining it we can see more recent impacts on the far side of the moon than on the near side. showing how the Moon has literally taken bullets for us on Earth by intercepting meteors before they hit earth.
Our fascination with the Moon has driven us to explore it more closely than any other celestial body, from the ambitious Apollo program to the upcoming Artemis program it’s currently the only place humans have been outside of Earth. Recent discoveries, like the presence of water ice in the permanently shadowed regions of the Moon's polar craters, have significant implications for future missions and the future of humanity and life itself.
Moon landing sites
The Moon, with its silvery glow, continues to captivate us, reminding us of our incredible journey and the boundless potential that awaits us in the cosmos. So, next time you find yourself gazing at the Moon, consider its profound connection with Earth. If you wish to delve deeper into lunar mysteries, we at AstroTours.org would be happy to take you there with one of our telescopes on one of our tours. Just make sure you book a program some time in between new moon and full moon to see it on a program. My favorite time to observe the moon is a few days after the new moon when Earth glow is present or a day or two after the full moon where the Moon joins the tour at the end and you can watch the Moon rise over Boulder Reservoir through our telescopes.