The Moon was in the news a lot lately. Earlier this week, half of the world was treated to a total lunar eclipse. People on that side of the world, which did not include the Philippines, saw the Moon get darkened by the Earth’s shadow.
Weeks ago, we also got news that China successfully landed a spacecraft on the far side of the Moon. The far side of the Moon is the side of the Moon we never see from Earth.
Because of its familiarity, we often take the Moon for granted. Which is why it might be nice to go through some fascinating things about the Moon some of you might not know.
One of the most common misconceptions about the Moon is that it is a nighttime object. The drawing of a crescent moon in the sky is often a shorthand indicating the scene being depicted is at night. (In this essay, I will be capitalizing ‘Moon’ when referring to the celestial object and not capitalizing when referring to a ‘moon’ phase.)
The Moon is actually just as present during the daytime as during the nighttime. In cultures where the calendars are based on the phases Moon, this fact is more commonly known.
The location of the Moon relative to the Sun depends on the phase of the Moon. During a full moon, the Moon is in the opposite side of the sky as the Sun. It rises at sunset and sets at sunrise. This means that the full moon is a completely nighttime object.
However, during a first quarter moon (half-moon), the Moon is perpendicular to the Sun in the sky. This means that it rises during noontime and is visible in the sky throughout the afternoon. By sunset, the first quarter moon will be high above the sky. It will set at around midnight.
During the last quarter moon (the other half-moon), the Moon rises at midnight. By sunrise, the Moon is high in the sky. It will set at around noon.
Speaking of the phases of the Moon, many of the world’s calendars are based on them. The months, especially, are based on the Moon’s phases.
One example of a lunar calendar is the ecclesiastical calendar on which Christian feast days and celebrations are determined. When Holy Week will fall, for instance, is computed using the phases of the Moon. According to church tradition, Easter is the Sunday after the ecclesiastical full moon that falls after March 21. (March 21 is the approximate date of the equinox.)
The Chinese calendar is also based on the phases of the Moon. In most years, Chinese New Year falls on the new moon closest to the traditional start of spring.
The phases of the Moon are a result of the relative positions of the Earth, Moon, and Sun. At any given time, half of the Moon is lit by the Sun. But because the Moon moves around the Earth, we see the light side from different angles.
During a full moon, we see the light side of the Moon full on, with the opposite side of the Moon completely dark. During a crescent moon, we see the light side of the Moon at an angle. During half moon, we see half of the light side of the Moon. Meanwhile, during a new moon, the light side of the Moon is on the other side.
Speaking of sides of the Moon, there is no such thing as “the dark side of the Moon” (aside from the Pink Floyd album, of course). There is, instead, the half of the Moon that is dark and light changes throughout the month.
Even though there is no permanently dark side of the Moon, the Moon has a permanent far side. The far side of the Moon is the side of the Moon we never get to see from Earth. Only a handful of astronauts during NASA’s Apollo missions got to see that side of the Moon that always points away from Earth.
The Moon has a permanent far side and near side because it moves in a very peculiar way: it rotates (spins) as fast as it moves around the Earth (revolves). The result of this is that the Moon shows the same side to the Earth all of the time (although it wobbles a little bit). In the language of astronomy, we say that the Moon is “tidally locked” to the Earth.
And this brings us back to the relationship between the Moon and Earth. Aside from raising the ocean tides, scientists think the Moon has a stabilizing effect on the Earth, so much so that life as we know it would probably be not possible if the Earth did not have a Moon.
The next time you see the Moon, think about how our skies, and our lives, would be so different without it.
