Archive for March, 2008

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X-rays Cure Snow Globe of “Static Cling”

March 16, 2008

Snow globe and x-ray machineClick here to watch the demo (1:40, AVI format, 4 MB). The forced-air snow globe has become a popular piece of holiday decor in recent years. But, as the Wikipedia article mentions, this toy is menaced by static cling: “snow” adheres to the inside of the plastic globe and refuses to fall. (Presumably, the globe and the snow become triboelectrically charged during operation.) So how do you instantly exorcise this static cling from your snow globe? Simple. You expose your snow globe to a powerful beam of ionizing radiation.

The video available here depicts a snow globe suffering from extreme static cling being treated with an 80 kVp / 3 mA portable x-ray machine that produces about 300 R / hr near the midpoint of the globe. The x-rays create ions in the air that rapidly discharge the plastic “snow” and globe, eliminating the electrostatic forces trapping the snow against the globe. This is a variant on the radiation-discharging-electroscope demo commonly practiced in physics lectures in the early part of the 20th century. A good example can be found in Sutton RM, ed., Demonstration Experiments in Physics, New York: McGraw-Hill (1938.):

“Three rubber balloons filled with hydrogen or illuminating gas and attached to a common point on the table by silk threads make an effective large-scale electroscope. When charged, they will stand far apart but will come together promptly when an x-ray beam is turned on them.” (p. 497-498.)

This genre of demonstration is rarely performed today for safety and liability reasons. In 1938, folks were aware that radiation had its hazards but were pretty casual about controlling exposure. Sutton’s words of caution prefacing the above excerpt embody this attitude perfectly:

Caution: Prolonged exposure to x-rays may produce bad burns. Do not expose any part of the body for more than a few minutes.”
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Hot Rocks and Haute Couture

March 16, 2008

Uranium FashionHere’s a little flashback to 1955, when the uranium boom on the Colorado Plateau was in full swing. The AEC was offering stratospheric premiums on new domestic uranium discoveries as the arms race with the Soviets accelerated. An impoverished Charlie Steen had discovered the Mi Vida Mine three years prior and become a multimillionaire, and his rags-to-riches story, along with many others, caught the country’s imagination. Toting around a Geiger counter looking for hot rock became popular—and even fashionable, according to this fanciful illustration from the May 23, 1955 issue of Life Magazine.

“Sears, Roebuck and Montgomery Ward now list Geiger and scintillation counters in their catalogs and report sales are skyrocketing. Clothing makers, responding to the amateur boom, have created dudish prospecting costumes, wearing which will harm no one.”

Reads the caption to the photo:

“Prospecting duds are girl’s ‘Diggerette Jr.’ suit, mother’s ‘U-235’ suit, father’s ‘smock.'”

Al Look scoffed at this scene in his wonderful contemporary account, U-Boom: Uranium on the Colorado Plateau (1956), writing

“In front of moth eaten scenery on a black canvas ground the Life teenager in braids wore a bright red ‘Diggerette Jr.’ suit and cowboy boots that were made only for riding horses. It was a good outfit for digging clams at Coney Island. This little lady carried a quart canteen, evidently the family water for a day’s work. The marcelled wife lugged a shovel heavy enough to drag a pack mule, and a geologist’s pick, which was all right, except that horsehide gloves, which she didn’t have, are recommended to handle rock picked out of the cliff. Her form-fitting suit, called the ‘U-235’ model, had patch pockets as big as saddle bags, to flop on the back of each leg and be torn off by the first sage bush. She had clodhopper shoes to make heel blisters, shoes loose enough to catch all the migrating gravel on the mountain. The male wore earphones and used both hands to carry a scintillator and probe, leaving nothing but feet for climbing. He was posed like an African big game hunter with a red shoe lifted on a papier-mache rock. They all wore headgear that would shed water like a sponge.”
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