“How does a voice travel over a wire?”

Mary wondered.

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It reminded her of something much simpler—a tin can tied to a string.

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When you speak into one can, your voice makes the bottom vibrate. Those vibrations travel along the string to the other can, where they turn back into sound.

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The telephone works in a similar way—but instead of a string, it uses electricity.

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Mary imagined her voice becoming tiny electrical signals, racing through the wire… then changing back into sound on the other end.

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From string…to wire…

From vibrations…to electricity…

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It made her wonder how many invisible things were moving all around her, unnoticed.