| 释义 |
ˈtime-ball
A ball moving on a vertical rod or pole, placed in some prominent elevated position, for the purpose of indicating mean time, which it does by dropping at a certain moment each day from the top to the bottom of the rod, usually by the closing of an electric circuit.
The time thus indicated is usually 1 p.m., in U.S. noon.
1858Simmonds Dict. Trade, Time-ball, a ball, moved by electricity, which is dropped from the summit of a pole to indicate the true meridional or mid-day time. 1878Lockyer Stargazing 279 This [wire] is used for dropping the time⁓ball at Deal. 1884Britten Watch & Clockm. 263 The time ball at Greenwich Observatory is of very thin copper. |