Colladon's Bell

Plate 88 speaks for itself: “Sound crossed the lake four times faster than in air.”

The Physics

In 1826 Colladon and Sturm struck a bell under Lake Geneva and lit a flash at the same moment. Timing the sound 13.5 km away gave its speed in water.

c = d / Δt = √(K / ρ)

• c: speed of sound, m s⁻¹
• d: distance, m
• Δt: delay, s
• K: bulk modulus, Pa
• ρ: density, kg m⁻³

1826: a bell under Lake Geneva, a flash above it. About four times faster than sound in air.

Sources

• D. Colladon, C. Sturm, Ann. Chim. Phys. 36, 113 (1827).

On the poster

Plate 088, “Colladon's Bell”: the pixel-art plate with its slogan “Sound crossed the lake four times faster than in air.”, the key equation and the facts panel shown above. Pixelated Physics. Physics. Personified.