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.
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September 1956
September 01 1956
The teapot effect…a problem
Markus Reiner teaches applied mechanics at the Israel Institute of Technology in Haifa, or the “Technion” as it is also known. By profession a civil engineer, he has worked as such for a whole lifetime—“doing science,” he explains, “as a hobby.” When Prof. Bingham of Lafayette College, Easton, Pa., learned about his work, he invited him to do research there, and Prof. Reiner spent two years (1931–1933) at Lafayette as research professor, cooperating with Bingham in the establishment of rheology as a new branch of physics. He is now head of Technion's rheological laboratory, where he treats concrete as a liquid and air as a solid. He has recently designed and built a centripetal airpump based on the fact that, as foreseen by Maxwell, air can be considered as a viscoelastic solid with a time of relaxation of about 10−10 seconds.
Physics Today 9 (9), 16–20 (1956);