Man-nen Dokei

ten thousand year clock



from press releases by Toshiba and JCN News

Japan's National Science Museum and Toshiba Corporation today announced that they have solved a long standing mystery by reconstructing the "man-nen dokei," literally a clock that works for tens of thousands of years. The ornate, incredibly complex six-faced chronometer was created by Hisashige Tanaka, the founder of Toshiba, in 1851. A team of researchers, engineers and specialists drawn from diverse fields painstakingly disassembled the original chronometer, studied its intricate mechanisms, and crafted a working replica that will go on display at Expo 2005 in Aichi, Japan. The delicate structure of the original "man-nen dokei" has long made it an object of fascination, an interest stimulated by the silence of the original. The clock has been investigated before, but not in enough depth to unravel the secrets of its clockwork mechanism and how Tanaka integrated such complexity—or if it really could run for a year on a single winding.

Just 24 inches tall, and weighing 83 and 3/4 pounds, the chronometer has six faces, each of which presented the passage of time in a different way: a standard western clock; the phases of the moon; the oriental zodiac; Japan's ancient 24-phase division of the lunar year; the days of the week; and the passage of the day in the old Japanese way, dividing the hours of dark and light into six equal parts. The chronometer also chimed to mark the passing of each part of the day. Despite the extraordinary complexity of this design, the clock was reputedly designed to operate for a whole year on only a single winding.

Toshiba, the owner of the "man-nen dokei" agreed to work with the National Science Museum to investigate this mystery, and the project also won support from a Ministry of Education, Culture, Sports, Science and Technology national program to investigate inventions of the Edo age. In the course of a yearlong investigation, the research team carefully dismantled the chronometer, investigated its mechanisms, and successfully reproduced them. The study confirmed that the chronometer actually worked, and could do so for a year on one winding. The replica of the clock was reactivated, when Mr. Tadashi Okamura, President and CEO of Toshiba, and Mr. Masamine Sasaki, Director General of National Science Museum together wound up the clockwork mechanism and ended 154 years of silence.


The intricacy of Tanaka's masterpiece was complemented by its exquisite exterior: features that included a carved wooden base, cloisonne enameling, fine metal reliefs and delicate filigree work transformed a scientific marvel into a work of art, finished with the crowning glory of a representation of the orbits of the sun and the moon within a glass dome. All of these features have been recreated by modern craftsmen of Japanese traditional art, who confirmed the excellence of the original work.

I found a small piece on this clock in the March 19-25 issue of New Scientist magazine and it fascinated me immediately not only for the mechanical sophistication it must require but also because i know that there is a group in this country called the Long Now Foundation working on a ten thousand year clock. i heard of the Long Now foundation several years ago because Stewart Brand, editor of the Whole Earth Catalog from 1968 to 1971, is involved and i try to keep up with his endeavors.