The moon is a celestial body that is familiar to people from all over the world, past and present.
All I remember about the moon is that I think I learned a little about it in science class when I was in elementary school.
This month has had a deep connection with the lives of Japanese people since ancient times.
Among these, the calendar continued to be an essential part of daily life.
Calendars were created to derive patterns in the passage of time and predict the future.
The first regular change to be noticed was the phases of the moon.
What is commonly known as the old calendar (≒ lunisolar calendar: the moon is called the moon in contrast to the sun) was born from observations of the moon.
It is believed that people around the world discovered early on that one year consists of about 12 phases of the moon.
The average period of the moon's phases (roughly speaking, the shape of the moon changes gradually, from new moon to crescent moon to half moon to full moon to half moon to crescent moon to new moon) is about 29.53 days. Multiplying this by 12 gives you about 354 days.
This calendar was called the lunar calendar, but people noticed that the calendar and the seasons gradually became out of sync when using the lunar calendar, because there was an 11-day difference from the 365-day year we are familiar with.
People then began to want to precisely define the calendar and seasons.
The reason why people wanted to measure the length of a year accurately in the first place was to be able to farm and hunt efficiently while responding to the changing climate and to live their lives. The length of a year is the "length of one cycle of the seasons." Therefore, the 24 solar terms, which were introduced from China, are used to measure the length of a year more accurately.
The 24 solar terms are used to relate calendar months to seasons. The movement of the sun (which is actually the Earth's 360 degree revolution around the sun) is divided into 24 equal parts of 15 degrees each, and each point is given a name (such as the beginning of spring, autumnal equinox, winter solstice, etc.).
Seasonal changes are mainly caused by the movement of the sun. In the past, people would steadily observe the altitude of the sun to discover the summer solstice (the longest day of the year) and winter solstice (the shortest day of the year). For example, the interval between the first observed summer solstice and the next was roughly 365 days, so this was considered to be "the length of one season's cycle." Then, as mentioned above, the movement of the sun was divided into 24 equal parts of 15 degrees each, and the seasons were further subdivided into the vernal equinox, autumnal equinox, the beginning of spring, and the beginning of summer.
On top of that, to make up the difference of 11 days between 354 and 365 days, which is derived from the phases of the moon, an extra month called an intercalary month is added approximately once every three years, eliminating the discrepancy.
It is called the lunisolar calendar because it combines the 24 solar terms based on the movement of the sun with the lunar calendar based on the movement of the moon.
The lunisolar calendar was used in Japan until 1872. Unfortunately, no country, including Japan, officially uses it today.
In Japan, the new calendar (≒Roman/Gregorian calendar) was introduced on January 1, 1873. The background to this was the opening up of Japan to the West, after which the Japanese lifestyle began to lean significantly towards Westernization.
The creation of a lunisolar calendar requires astronomical and mathematical observations and is extremely complex, but at the same time, it gives us a glimpse into the lives of the Japanese people, who meticulously observed the changes in the moon, sun, and seasons.
And for the Japanese, for whom farming played an important role in life, it is likely that knowing the passage of time and the regularities of the seasons was extremely important.
At its farthest distance from the Earth, the Moon is approximately 400,000 km.
Nevertheless, the moon has been illuminating the night world brightly and beautifully since time immemorial.
There is a beautiful passage in Yukio Mishima's novel "Kinkakuji" that describes the wind and the moon in the temple grounds.
"The wind suddenly calms down, then gets stronger again. The forest listens attentively, becoming quiet then becoming noisy. The moonlight on the pond darkens and lightens with each movement, sometimes twitching its diffused light as the wind swiftly sweeps across the pond's surface."
The moon is scheduled to rise at 12:53 tonight.
