Sonara

Sonara traps a single bubble in sound, and on every squeeze it flashes.

The Physics

A gas bubble held in water by a strong sound wave swells and then collapses violently, giving off a flash of light lasting 60–250 picoseconds, once per sound cycle. The bubble's radius follows the Rayleigh–Plesset equation.

R R̈ + (3/2) Ṙ² = (1/ρ) [p_g − P₀ − P(t) − 4μṘ/R − 2σ/R]

• ρ: liquid density (kg/m³)
• R: bubble radius (m)
• Ṙ, R̈: wall speed (m/s) and acceleration (m/s²)
• p_g: gas pressure in the bubble (Pa)
• P₀: ambient pressure (Pa)
• P(t): acoustic drive pressure (Pa)
• σ: surface tension (N/m)
• μ: liquid viscosity (Pa·s)

Gaitan et al. first trapped a single sonoluminescing bubble in 1992; Gompf et al. (1997) measured flash widths from about 60 ps to over 250 ps.

Honest caveat: How the light is made is still debated, and the bubble does not have a single agreed temperature.

On the shirt

Front: Sonara, the pixel-art character, with the title. Back: the Rayleigh–Plesset equation, the flash duration, one flash per cycle and the 1992 and 1997 sources. Printed on a unisex tee.