Orbiting a vast 240,000 miles away and moving 1 inch further each year, earth’s only natural satellite, the moon, lights up our night sky. Though it is not the only moon in our solar system (at least 190 moons have been discovered), we refer to it as “The Moon” because until 1610, when Galileo Galilei discovered four moons orbiting Jupiter, people had though it was the only moon.
The formation of the moon was thought to have occurred 4.5 billion years ago when a Mars sized body collided with Earth. After impact, the lingering debris began to accumulate forming a molten mass. Within about 100 million years most of the magma crystallized and the less dense rocks floated up forming the lunar crust. The gravity on the moon is one-sixth earth’s, this is why astronauts seem to bounce across the surface. Since the atmosphere of the moon is thin and weak it cannot impede impacts, which results in a steady rain of meteoroids, asteroids and comets. The result of these impacts is a cratered surface, some of which are as large as 52 miles wide. Scientists discovered that during micrometeoroid impacts, the moon releases its water. This water was actually thought to have been non-existent up until the detection of ice in 2008. The thin atmosphere of the moon also results in extreme temperature fluctuations, ranging from 260 degrees Fahrenheit in the full sun to -280 degrees Fahrenheit in darkness. As for the so called “dark side of the moon”- it’s not really dark. From earth, we only see one side of the moon since its orbit is synced with ours in a phenomena called tidal locking.
The moon does not produce its own light; therefore the silvery glow we see is sunlight’s reflection off the moon’s surface. The moon makes a full orbit around earth about every 29.5 days and during this orbit we see different illuminations. We have separated these illuminations into eight main lunar phases. First is the “new moon,” when the moon is nearly invisible in the sky, set between the earth and the sun. During this phase we would only be able to see the moon during a solar eclipse. As the illuminated surface increases, “waxing crescent” occurs when the moon is less than half full. When the moon is half full we call the phase “first quarter” and more than half full is “waxing gibbous”- gibbous being the Latin word for “hump.” The “full moon” occurs next and this is a time when we can sometimes see a lunar eclipse. If there are two full moons in a month, the second full moon is referred to as the “blue moon”. After the full moon, the illuminated surface begins to decrease, leading to the next phase named “waning gibbous”. Following is “last quarter” meaning half the surface is illuminated, and last is “waning crescent” when less than half the surface is illuminated. The cycle then begins again with another “new moon.” Since the moon’s orbit is not a perfect circle, the distance to our planet changes during the course of an orbital cycle. When the full moon coincides with a particularly close approach, also known as a perigee, we call the moon a “super moon.”
Our moon is vital to the earth and its inhabitants. The moon helps regulate earth’s climate, tides, axis wobble and orbit. The lunar cycle has helped to keep track of the passing year and set a schedule for hunting, planting and harvesting. In North America, our full moons were named from North American indigenous tribes, who usually used the behavior of plants, animals or the weather for the naming.
By Renee Squires