Science: Master Clock

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Through Copenhagen's ornate Town Hall trooped a steady stream of sightseers last week to look at the workings of the world's most complex astronomical clock. Set in motion shortly before Christmas by Denmark's King Frederik IX, the clock is expected to run steadily for more than 1,000 years, deviating in its measurement of sidereal time by only two-fifths of a second every 300 years. If properly cared for, it will accurately calculate the position of the stars in the universe for the next 25,700 years.

The Copenhagen clock is the product of some 40 years' planning by onetime Locksmith Jens Olsen, who died in 1945. A self-taught astronomer, physicist and engineer, Olsen conceived the idea of his clock after seeing the famed astronomical clock in Strasbourg. He devoted all of his spare time to planning it and calculating its complex mathematical functions. With funds raised by clockmakers' societies, he completed the plans in 1944, lived just long enough to supervise the first months of production of the clock's 15,000 different parts. Since then, a million dollars has gone into the clock. It is housed in an airtight, humidity-and-temperature-controlled glass case.

The clock has ten faces and eleven sets of coordinated work's moved by weights. Its 445 toothed wheels revolve at rates which vary from once every ten seconds to once every 25,000 years. (Olsen once showed a small wheel to a friend with the remark: "This piece will first be used in another thousand years.") Among the things that the clock computes: the days of the week, date, month and year on the Gregorian calendar, the Julian day and year, the movements of the planets, sunrise and sunset by mean solar time and true solar time, central European time, and sidereal time. Inventor Olsen's own favorite chronologic refinement: a calendar of church feasts, which at the beginning of each year records the coming year's feast days after the calendar mechanism has gone through 570,000 different functions in six minutes.