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Exhibition Guide

Phases of the Moon




Purpose of Exhibition

The Moon is the only natural satellite around the Earth. The shape of the moon in night sky has been precious and familiar to us, since it is not only illuminating the night sky, but also we used to as a calendar, based on its the periodic phases.
Because the Moon is lit by the sunlight, half of it is always bright. Since the Moon is rotating around the earth, depending from which angle we look at it we can see various shapes of this lit face. The form of the lit face of the Moon changes on daily basis, starting from the new moon, slowly changing the shape into the first quarter moon, then full moon, last quarter moon, and finally the new moon again. It takes almost a month - "about 29.5 days"- to complete an entire cycle.
This exhibit introduces the different phases of the moon using the models of the moon and the earth, and a syncronized rotating model of the Moon based on data from the lunar orbiter "Kaguya".

Additional Knowledge

[About the Various Names of the Moon]
The Moon has been called by various names in Japanese since early times. Based on the lunar calendar, the Moon on the first day is called "Shingetsu" (new Moon), the third day "Mikazuki" (crescent) and the fifteenth day "Juugoya no Tsuki". The fifteenth day Moon is often the full Moon. The sixteenth day Moon has a special name, which is "Izayoi no Tsuki" (waning gibbous)."Izayoi" means "to hesitate" suggesting that the Moon is hesitating to come, and appears later in the sky than the full Moon.
The seventeenth day's Moon is called "Tachimachi no Tsuki", meaning that if we wait standing for a while, then the Moon appears. The eighteenth day's Moon is called "Imachi no Tsuki", which means that the Moon appears later than "Tachimachi no Tsuki", and we may want to sit down and wait for it. The nineteenth day's Moon is "Nemachi no Tsuki" meaning that the Moon appears while we lie and wait for it since it comes much later. "Fukemachi no Tsuki" is the Moon on the twentieth day. It means that as the night goes on, the Moon finally appears and we can see it. For Moons after the sixteenth night's Moon is the one we see even at the dawn of day and it is called "Ariake no Tsuki".

[How was the Moon born?]
There are several possible origins of the Moon. The "Parent-child theory "is the one in which a broken and torn part of the Earth became the Moon.
The "Co-formation theory" suggests that the Moon was born at the same time as the Earth while the "Captured theory" suggests that the Earth captured the Moon after it was created in another area of the Solar system. These theories explain only a part of the Moon's properties but not all of them.
The "Giant impact theory" is the most widely believed theory now.
According to this theory, at the time that the Earth was born, one of the many Mars-sized objects in the solar system which used to be there collided with the Earth. This collision caused to spread and gravitate a lot of matter around the Earth, after crashing and merging together these blocks of matter cooled down and formed the moon as we know it.


【 References 】

Article by Astronomy Section


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