WEBVTT - How Atomic Clocks Work

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<v Speaker 1>Get smarter in sixty seconds with brain Stuff from how

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<v Speaker 1>stuffworks dot com Hi Marshall Brain. Atomic clocks are important

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<v Speaker 1>to a variety of scientific endeavors. You can even buy

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<v Speaker 1>wall clocks and wrist watches that will synchronize with an

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<v Speaker 1>atomic clock in Colorado. So what exactly is an atomic clock.

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<v Speaker 1>Let's start with the general notion of a clock. A

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<v Speaker 1>clock's job is to keep track of the passage of time.

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<v Speaker 1>All clocks do this by counting the ticks of some

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<v Speaker 1>kind of resonator. In a pendulum clock, the resonator is

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<v Speaker 1>the pendulum. The gears in the clock keep track of

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<v Speaker 1>the time by counting the resonations, those swingings back and

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<v Speaker 1>forth of the pendulum. The pendulum usually resonates at a

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<v Speaker 1>frequency of one swing per second. A digital clock uses

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<v Speaker 1>either the oscillations of the power line, which is sixty

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<v Speaker 1>cycles per second in the United States, or the oscillations

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<v Speaker 1>of a quartz crystal as the resonator. It counts the

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<v Speaker 1>oscillations using digital counters. The accuracy the clock is determined

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<v Speaker 1>by the accuracy of the resonator. In an atomic clock,

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<v Speaker 1>the clock uses the resonant frequency of atoms as its resonator.

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<v Speaker 1>There are many different ways to get atoms to oscillate,

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<v Speaker 1>and you can then detect and count those oscillations. The

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<v Speaker 1>advantage of this approach is that the atoms resonate at

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<v Speaker 1>extremely consistent frequencies. If you take any atom of caesium

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<v Speaker 1>and ask it to resonate, for example, it will resonate

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<v Speaker 1>at exactly the same frequency as any other atom of caesium.

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<v Speaker 1>Caesium one thirty three oscillates at nine billion, one nine

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<v Speaker 1>two million, six hundred thirty one thousand, seven hundred seventy

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<v Speaker 1>cycles per second period. This sort of accuracy is completely

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<v Speaker 1>different from the accuracy of a Courts clock. In a

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<v Speaker 1>quartz clock, the Courts crystal is manufact extured so that

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<v Speaker 1>it's oscillating frequency is close to some standard frequency. But

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<v Speaker 1>manufacturing tolerances cause every crystal to be slightly different, and

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<v Speaker 1>things like temperature will change the frequency. A caesium atom

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<v Speaker 1>will always resonate at the same known frequency. That is

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<v Speaker 1>what makes atomic clock so precise. Do you have any

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<v Speaker 1>ideas or suggestions for this podcast? If so, please send

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<v Speaker 1>me an email at podcast at how stuff works dot com.

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<v Speaker 1>For more on this and thousands of other topics, go

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<v Speaker 1>to how stuff works dot com,