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Christian Doppler: 2 ideas worth knowing

2 ideas from Christian Doppler, each explained in a minute and credited to the original work. Free on Savvy.

• A physicist proved sound bends pitch by testing trumpeters on a moving train

  Christian Doppler predicted in 1842 that a sound's pitch should rise as its source approaches and fall as it recedes. Three years later, Dutch scientist Christophorus Buys Ballot t…

  — Christian Doppler; tested by Christophorus Buys Ballot, Über das farbige Licht der Doppelsterne (On the Coloured Light of Double Stars)

• A siren sounds higher coming toward you and lower moving away for one reason

  The Doppler effect is the change in a wave's apparent frequency caused by motion between its source and an observer: sound waves bunch up and rise in pitch as a source approaches, …

  — Christian Doppler, Über das farbige Licht der Doppelsterne

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