Shock waves in stellar atmospheres and breaking waves on an ocean beach.

The phenomenon of ocean waves breaking on a beach is analogous to shock waves in the atmosphere of a pulsating star. In both cases a velocity discontinuity is clearly present. In stars the upper, expanding layer halts and falls back so as to interact with the rising gas at a shock. Similarly, a bore on a beach reaches its maximum extension before sliding back onto the next incoming wave. Analogous quantities such as the surface gravity of the star and the beach gradient in the ocean have similar effects on the flows and the nature of the discontinuity between them. Phenomena that are not analogous include the thermodynamic properties of the two media. Ocean observations may help solve some problems in shock phenomena associated with stellar pulsation.