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Ice cream as teaching tool, Postage stamp honors Fuller, Weekend effect

by K. M. REESE
July 26, 2004 | A version of this story appeared in Volume 82, Issue 30


Ice cream as teaching tool

Recent mention of the Réaumur thermometer (C&EN, May 31, page 48) prompted Stephen J. Tauber of Lexington, Mass., to tell of his experiences with that device. It hung inside the window of the bedroom he shared with his older brother and had dual calibration—Celsius on the right and Réaumur on the left. “By age six,” Tauber says, “I could readily convert between [the two scales] in my head.”

In the same bedroom, Tauber recalls, his brother let him help make ice cream in a hand-cranked freezer. Ice cream mix went into the inner metal container; ice and salt went into the surrounding wooden tub. “Why the salt?” Tauber asked his brother. His brother said, “To make the ice colder.” “But ice melts at 0 °C,” Tauber came back. “How does salt make it colder?”

“Pity my poor brother,” Tauber says, “who presumably did not himself understand heat of fusion or triple points. The ice cream did freeze, and it was duly eaten.”

Tauber writes that in 1938, when his family fled from German-occupied Austria to British India, he was introduced to Fahrenheit temperatures. Not until college, however, did he learn that the zero point on the Fahrenheit scale was defined by that ice-salt mixture that let him and his brother crank out ice cream.

Postage stamp honors Fuller

The U.S. Postal Service has issued a commemorative postage stamp to honor R. Buckminster Fuller (1895–1983), the man who devised the geodesic dome. USPS also terms Fuller “the legendary American inventor, architect, engineer, designer, geometrician, cartographer, and philosopher.”

After 1947, the geodesic dome dominated Fuller’s life and career. The USPS announcement says, “Lightweight, cost-effective, and easy to assemble, geodesic domes enclose more space without intrusive supporting columns than any other structure, efficiently distribute stress, and can withstand extremely harsh conditions.” USPS continues, “Based on Fuller’s ‘synergetic geometry,’ his lifelong exploration of nature’s principles of design, the geodesic dome was the result of his revolutionary discoveries about balancing compression and tension forces in building.”

Fuller applied for a patent for the geodesic dome in 1951, and he received it in 1954.

Weekend effect

Scientists in california have been studying the “weekend effect.” Intriguing as that sounds, it has nothing to do with romance or bar hopping.

The phenomenon in question is that weekends in the Golden State are becoming more smoggy. Robert A. Harley, professor of civil and environmental engineering, and colleagues at the University of California, Berkeley, wondered why. They analyzed 20 years of air monitoring data from more than 100 sites throughout the state. They found that smoggy weekends have been spreading from coastal urban areas, such as Los Angeles and San Francisco, to points inland—Sacramento and the northern San Joaquin Valley, for example.

Smog is formed when pollutants such as nitrogen oxides and volatile organic compounds are emitted into the lower atmosphere and react with sunlight to create ozone. “Smog levels always increase in the summer when it’s warmer and there is more sunlight,” Harley explains. “But buried in this annual cycle is variability at other timescales such as the day of the week. … It’s counterintuitive, but reducing emissions from diesel trucks may lead to higher ozone levels on weekends.”

The precise mechanisms are unclear, he says, but one theory holds that nitrogen oxides from diesel engines can help suppress ozone formation under certain conditions. Only a very large reduction in NO2 emissions—say 90%—would actually result in smog reduction, Harley adds.

Another factor for the weekend effect, he says, may be the shift in peak driving hours. That peak moves from morning and evening hours during the week to about noontime on the weekend—precisely when the sun is brightest and conditions are optimal for ozone formation. “On the weekend, even though the number of cars on the road is almost the same, you get a shift in the timing of emissions, which can contribute to more smog.”


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