Have you ever stood at the foot of a waterfall, and marked the bubbles rising to the surface and gathering into foam? Some are quite small, and break as soon as they are born. Others last longer; new ones come to join them, and they swell up to a great size: yet in the end they burst, as surely as the rest; it cannot be otherwise. There you have human life. All men are bubbles, great or small, inflated with the breath of life. Some are destined to last for a brief space, others perish in the very moment of birth: but all must inevitably burst.
The text is one of the more elaborate early sources for the classical commonplace that would become a mainstay of European art and literature: homo bulla—“man is a bubble.” As this austere apothegm drifted out of the stern world of the Stoics and into the fervorous sentimentalism of Christiandom, it became the tear-jerking translucency at the center of human vanity: we are beautiful, delicate, and we die too soon.
As with any metaphor, though, everything depends on the vehicle. We are bubbles? Really? But of what sort, exactly? Charon envisioned the froth on the Styx. Okay, but there are more bubbles under those waters than were dreamed of in his ferryman’s philosophy. Let us consider two of them, in the hopes that contemporary fluid dynamics and marine biology can breathe new life into this hollow allegory.