WEBVTT - How do self-winding watches work?

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<v Speaker 1>Welcome to brain Stuff from how stuff works dot com

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<v Speaker 1>where smart Happens. Hi'm Marshall Brain with today's question, how

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<v Speaker 1>does a self winding watch work? You may be able

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<v Speaker 1>to remember when the first electronic courts watches came out,

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<v Speaker 1>they were going to be the end of normal mechanical watches,

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<v Speaker 1>just like videotape was going to be the end of

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<v Speaker 1>movie theaters. Somehow, it hasn't worked out that way, and

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<v Speaker 1>self winding watches are more popular than ever. So how

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<v Speaker 1>does the self winding watch work? The easiest way to

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<v Speaker 1>see it is to go to a store that sells

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<v Speaker 1>watches and look at a skeleton watch with a clear back.

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<v Speaker 1>You will see a semicircular metal piece that's the heart

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<v Speaker 1>of any self winding watch. Relatively speaking, this semi circular

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<v Speaker 1>piece is fairly heavy, and it's therefore affected by gravity.

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<v Speaker 1>As you move the watch, this piece will move so

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<v Speaker 1>it's always pointed towards the ground. As you walk with

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<v Speaker 1>your arms swinging back and forth, this piece moves back

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<v Speaker 1>and forth. Inside the watch, the piece is attached to

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<v Speaker 1>a gear train that gears it way down. Each movement

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<v Speaker 1>of your arm winds the spring. The tiniest bit but

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<v Speaker 1>Since you move your arms so much, it keeps the

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<v Speaker 1>watch wound easily. The spring and the watch stores enough

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<v Speaker 1>energy to keep the watch going for about a day

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<v Speaker 1>and a half if you leave it on the dresser.

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