The Physics of Skyscrapers, Nova Story Is Urban Legend?, More Uses for Dhmo, Ice Cream Upgraded

The following tale appears in the spring 2004 issue of Philatelia Chimica et Physica. The story, sent in to that publication by Russell Harvey of Surrey, England, concerns a problem posed in the past on a physics degree paper at Copenhagen University. The problem: Describe how to determine the height of a skyscraper with a barometer. One student wrote the following: Tie a string to the neck of the barometer and lower the instrument from the roof of the skyscraper to the ground. The length of string paid out, plus the length of the barometer, will equal the height of the building.

The faculty failed the student at once because his answer, although clearly correct, showed no noticeable knowledge of physics. The student appealed and was given an opportunity to answer verbally to an arbitrator in a manner that displayed a grasp of the principles of physics.

The student told the arbitrator that he had several neat answers but couldn't decide which one to use. For example, you drop the barometer from the roof of the building and time its fall to the ground. You then figure the height of the building by the equation h = 1/2gt², "but this is hard on the barometer." The student reeled off several other solutions to the problem, all correct but all displaying unhappy characteristics.

The student concluded, "Because we are constantly being exhorted to exercise independence of mind and apply scientific methods, undoubtedly the best way would be to knock on the janitor's door and say to him, 'If you would like a nice new barometer, I will give you this one if you will tell me the height of the building.' "

Legend has it that the student was Niels Bohr.

Nova story is urban legend?

Almost all ice cream is made by an industrial version of a hand-cranked device invented by Nancy Johnson, an American, in the 1840s. That's what Robert Kunzig says in the June issue of Discover.

It's big business, Kunzig reports. Sales of frozen desserts, mostly ice cream, total about $20 billion and 1.5 billion gal per year in the U.S. Americans eat more than 20 quarts annually, second only to New Zealanders. Lurking in the wings is Asia, especially China, whose billion-plus people get by on some 2 quarts a year apiece.

Makers of ice cream, however, have long been fighting a problem called heat shock, which produces unsuitably big ice crystals in the ice cream. A solution to the problem has been found by Erich Windhab, who teaches at the Swiss Federal Institute of Technology, Zurich.