Pour yourself a glass of beer and look closely at the rising bubbles. Careful examination shows that they are seldom distributed uniformly throughout the liquid. Instead, streams of bubbles appear to rise from certain spots on the surface of the glass. Closer inspection reveals that the bubbles rapidly grow in size as they ascend, the volume of each bubble often doubling or more by the time it reaches the top of the glass. In addition, the speed of the bubbles increases as they travel upward.

1.
C. F. Gohren, Clouds in a Glass of Beer: Simple Experiments in Atmospheric Physics, Wiley, New York (1987).
2.
D. A. Glaser, in Les Prix Nobel en 1960, Imprimerie Royal, Stockholm (1961), p. 77.
3.
F. S.
Crawford
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(
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4.
J. Walker, Sci. Am., December 1981, p. 172.
5.
See R. Clift, J. Grace, M. Weber, Bubbles, Drops and Particles, Academic, New York (1978).
6.
See A. M. Gaudin, Flotation, 2nd ed., McGraw‐Hill, New York (1957).
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