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Trumpets on a Train
Plate 089 Physics Poster
Plate 89 speaks for itself: “The note changed as they passed.”
The Physics
Buys Ballot put musicians on a train near Utrecht to test Doppler's prediction. Listeners heard the note sharpen as the train approached and drop once it passed.
f′ = f c / (c − v_s)
- f′: heard frequency, Hz
- f: emitted frequency, Hz
- c: speed of sound, m s⁻¹
- v_s: source speed toward the listener, m s⁻¹
1845: musicians on a train near Utrecht. Sharper as it came, flatter once it passed.
Sources
- C. H. D. Buys Ballot, Ann. Phys. 142, 321 (1845).
On the poster
Plate 089, “Trumpets on a Train”: the pixel-art plate with its slogan “The note changed as they passed.”, the key equation and the facts panel shown above. Pixelated Physics. Physics. Personified.
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