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Clock drift refers to several related phenomena where a clock does not run at the exact right speed compared to another clock. That is, after some time the clock "drifts apart" or gradually desynchronize from the other clock. This phenomenon is also used, for instance, in computers to build random number generators. On the negative side, clock drift can be exploited by timing attacks. == In non-atomic clocks == (詳細はwristwatches have finite precision. Eventually they require correction to remain accurate. The rate of drift depends on the clock's quality, sometimes the stability of the power source, the ambient temperature, and other subtle environmental variables. Thus the same clock can have different drift rates at different occasions. Mechanical watches drift much more than quartz ones, but they are designed to drift ahead rather than behind, so that the watch gains time, making it easier to set the time to the second with the hack (stop mechanism) function. More advanced clocks and old mechanical clocks often have some kind of speed trimmer where one can adjust the speed of the clock and thus correct for clock drift. For instance, in pendulum clocks the clock drift can be manipulated by slightly changing the length of the pendulum. A quartz oscillator is less subject to drift due to manufacturing variances than the pendulum in a mechanical clock. Hence most everyday quartz clocks do not have an adjustable drift correction. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Clock drift」の詳細全文を読む スポンサード リンク
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