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网上找到的,据说仿真度较高,请大家仔细阅读
The Shortt clock had two pendulums. The first, known as the master, swung freely in an evacuated case. Its only job was to synchronize the swing of the second pendulum, called the slave, which was housed in a neighboring cabinet. Every 30 seconds the slave sent an electrical signal to give a nudge to the master. In return, via an elaborate electromechanical link, the master ensured that the slave never got out of step.
Shortt clocks were standard provision in astronomical observatories of the 1920s and 1930s, and are credited with keeping time to better than 2 milliseconds a day. Many were on record as losing or gaining no more than 1 second a year – a stability of one part in 30 million. The first indications of seasonal variations in the Earth’s rotation were gleaned by the use of Shortt clocks.
In 1984 Pierre Boucheron carried out a study of a Shortt clock which had survived in the basement of the US Naval Observatory since 1932. Using the modern optical sensing equipment instead of the electromechanical coupling, he measured its rate against the observatory’s atomic clocks for a month. He found that it was stable to 200 microseconds a day over this period, equivalent to two to three parts in a billion. What is more, the data also reveal that the clock was sensing the distortion of the Earth due to tides from the Moon and the Sun. |
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