One of the most beautiful and iconic events which occur in the night sky is the phases of the moon. The phase of the moon is the sunlit portion of the Moon, which is directly observed from Earth.
These lunar phases gradually change over a synodic month – around 29.53 days. This happens as the orbital positions of the Moon around Earth and that of Earth around the Sun shift.
Today, we are going to answers some of the questions regarding the Moon’s phases, such as:
- What are the phases of the Moon?
- What is a synodic month?
- Why does the Moon have Phases?
- When is the Harvest Moon?
- What is a Blue Moon?
- Why do we see only one face of the Moon?
- When does the young Moon become visible in the evening sky?
- What is a Wolf Moon?
What are the phases of the Moon?
When it comes to western culture, there are only four main phases of the Moon:
- New Moon
- First Quarter
- Full Moon
- Third Quarter
These phases are instances when the Moon’s ecliptic longitude and the Sun’s ecliptic longitude differ by 0, 90, 180, or 270 degrees. All of these phases occur at slightly different times when viewed from different parts of the world [1].
Between the intervals of the principal phases, the Moon’s shape is either crescent or gibbous. These shapes and their periods are called the intermediate phases and last one-quarter of a synodic month, or 7.38 days.
Their durations can, however, slightly vary due to the Moon’s orbit. It is elliptical, and as such the orbital speed is not constant. The term waxing is used for an intermediate phase when the Moon’s apparent shape is thickening, from new to a full moon, and waning when the shape is thinning [2].
The eight principal and intermediate phases in sequential order are:
- New Moon
- Waxing Crescent
- First Quarter
- Waxing Gibbous
- Full Moon
- Waning Gibbous
- Last Quarter
- Waning Crescent
When it comes to different cultures around the world, for example, the traditional Hawaiian culture, this differs. The Hawaiians have 30 phases of the Moon, with one occurring per day.
What is a synodic month?
A synodic month or lunar month is a period measured from a moon’s phase until the return of that same phase. The long-term average duration is estimated to be at around 29.5 days.
Why does the Moon have Phases?
This happens because the Moon orbits Earth, and this causes a portion that is illuminated on its surface to change. The Moon completes one orbit around the Earth once every 27.3 days, though the lunar phase cycle or synodic month is 29.5 days [3].
This happens because the Moon is “catching up” to us in around 2.2 days since our planet is moving faster. In the New Moon phase, the Moon is located between the Earth and the Sun.
At the first quarter phase, the Moon is half-lit, and it is the highest in the sky at sunset, then it sets about six hours later. During the full moon phase, the Moon is behind Earth in space concerning the sun. When the sun sets, the Moon rises with the side that faces Earth fully exposed to sunlight.
When is the Harvest Moon?
When the full moon occurs closest to the autumnal equinox (An equinox is when night and day are equal), it is often referred to as the Harvest Moon [4]. This is because of its bright presence in the night sky would allow farmers to work longer into the fall night, reaping the rewards of their spring and, respectively summer labors.
Since the equinox falls in late September, it is generally a full Moon in September which is given this name though this can sometimes vary and October takes the designation. Each full moon of the year has its own name.
These names of moon are associated with weather, agriculture or ancient deities. The commonly used names in North America are:
- Moon after Yule – January
- Snow Moon – February
- Sap Moon – March
- Grass Moon – April
- Planting Moon – May
- Honey Moon – June
- Thunder Moon – July
- Grain Moon – August
- Fruit or Harvest Moon – September
- Harvest or Hunter’s Moon – October
- Frosty Moon – November
- Moon before Yule – December
What is a Blue Moon?
The time between two full Moons doesn’t equal a whole month. Around three years there are two full Moons in one calendar month [5]. In recent decades the second full Moon has been termed the Blue Moon.
A blue moon occurs once every 33 months and as such, they are rare. The origin of the name remains unknown; some believe it is attributed to the fact that an unusual blue coloring of the Moon does indeed happen which may be caused by high-altitude dust particles.
Others believed that the sources come from the phrase “once in a blue moon.”
Why do we see only one face of the Moon?
Gravitational interactions between the Earth and the Moon have gradually slowed down the Moon’s rotational speed and as such, it completes one rotation on its axis at the same time that it completes one orbit around Earth.
This gravitational drain is a mutual effect; it also slows down Earth’s rotational speed. These effects can be witnessed in ocean tides. It’s possible that in the far future, both celestial objects will have only one side facing each other eternally.
When does the young Moon become visible in the evening sky?
Many factors determine the visibility of the young Moon, such as:
- The angle of the ecliptic concerning the horizon
- The clarity of the sky
- The keenness of the observer’s eyesight
When the ecliptic is perpendicular to the horizon, the young Moon becomes visible to the unaided eye much earlier.
What is a Wolf Moon?
Many ancients reffered to the full Moon which occurred in January as the wolf moon. It is unclear why, but some speculate that wolves would howl more actively in this time of the year perhaps due to a lack of food. The wolf moon is also commonly reffered to as the Moon after Yule.
Did you know?
– The Moon is believed to be around 4.5 billion years old. Many scientists speculate that the Moon is actually a chunk of Earth, which was torn off during a collision.
– If someone would be above Earth and would look down from the North Pole, the Moon would appear to be moving counterclockwise around Earth.
– The most potent tidal activities occur during a full moon. This also has some effect on a person’s overall weight because of stronger gravitational interactions.
– The Moon actually experiences quakes due to gravitational interactions with Earth.
– Though the Apollo mission is famous for being the first to land the moon, the actual first spacecraft to do so, though unmanned, was the Luna 1 spacecraft conducted by the soviets. This happened in 1959, while the Apollo mission occurred ten years later.
– In comparison with all the other natural satellites present in the solar system, the Moon is the fifth largest, though much smaller than the moons of Jupiter and Saturn.
– During the height of the cold war, the USA considered detonating a nuclear bomb on the Moon.
– The average distance between the Earth and the Moon is at around 238,900 mi / 384,000 km.
– The average speed of which the Moon orbits the Earth has been estimated to be at approximately 2,300 mi / 3,700 km per hour.
