Q14.The moon phase mechanism of watches was indispensable for people in a certain profession. who are they? | Watch LIFE NEWS | Watch comprehensive news site to enjoy watch life

A. People involved in the sea, such as sailors

This year's Mid-Autumn Moon will also be tomorrow (September 21, 2021), so this time we will take up the "moon phase (age display)" as a theme related to the moon.

　Moon phase mechanism that expresses the phases of the moon in a small window on the dial. Its history is much older than the history of wristwatches, and it has already appeared in table clocks in the 16th century, and it began to be equipped in pocket watches after the 18th century. Even if you know the role of this moon phase, there may be few people who know why it was necessary. One of the reasons for this is the phenomenon of tides, which are caused by the relationship between the moon and the earth.　The tidal force caused by the difference between the gravitational pull exerted by the moon on the center of the earth and the gravitational pull exerted on the earth's surface. The surface of the earth that is most affected by this is the surface of the sea. The phenomenon in which the tidal force increases and the sea surface rises is called "high tide", and the opposite is called "low tide". When the tide level difference between high tide and low tide increases in a day, it is called "spring tide", and vice versa is called "neap tide".

In other words, understanding spring and neap tides was very important for people in the past who were involved in the sea. Especially for large ships, this could lead to serious accidents such as running aground. It is also said that these spring and neap tides affect fish and change their habitat, so it was very important for people involved in the fishing industry to know this in order to make a living. And these spring and neap tides are closely related to the phases of the moon. The full moon and new moon are spring tides, and the half moon is neap tides. However, the moon is not always visible. This is because it depends on weather conditions such as rain. That's where a watch's moon phase, which you can always check, comes in handy.

In the past, it was common for faces to be drawn on moon phase moon patterns like in the photo, but now they are rarely drawn because their design role is more important than their practical function. A dead-stock watch ◎ An outline moon phase chronograph 7768 equipped with a dead-stock Valjoux manual-winding movement, cal.7768. Limited to 17 pieces. 242,000 yen / Seeds Factory (TEL.03-5562-0841)

Sentence ◎ Yuki Matsumoto (editorial department) / Photo ◎ Osamu Kasai

References: Keiji Kasagi and Koichi Namiki, Watch Trivia Note (Diamond Publishing, 2000) p153-158

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