As probably everybody has experienced to his or her dismay, when tea is poured out of a teapot, the jet, more often than not, has a tendency not to flow in a nice ballistic curve, as intended, into the cup, but to follow the underside of the spout, and soil the table cloth. Every physicist from a large number whose opinion I asked on the possible reason for this phenomenon, replied it must be due to surface tension or, in other terminology, capillary action or adhesion. Now, surface tension is one of the most nebulous terms of physics; many textbooks on the subject will tell the student that there is no such thing, and that the proper term is surface energy. We need not go into this question here, suffice it to say that when the physicist is pressed to express himself more clearly, he will say that this teapot effect is obviously due to the adhesion between the liquid (tea) and the solid (spout), and that the “phenomenon” was no problem and not worth another minute's thought.
The teapot effect…a problem
Markus Reiner; The teapot effect…a problem. Physics Today 1 September 1956; 9 (9): 16–20. https://doi.org/10.1063/1.3060089
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