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Kilo Commentary Light on Math and Science

June 08, 2003

Crispin Sartwell's "Kilo Crisis Could Bring Down the Universe" (Commentary, June 3) was a funny spot in a day's load of grim reality. However, the ultimate demise of the universe will come 100 times sooner than his prediction based on his wife's multiplication work. At a loss of 50 micrograms per century, the kilogram cylinder will shrink to zero in 2 billion, not 200 billion, years.

This doesn't really make me any gloomier about the state of the universe, but perhaps the professor may want to look over his wife's checking account occasionally.

Wesley G. Banbury

Woodland Hills

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Sartwell needs a physics course. His "kilo crisis" commentary is based on a fundamental confusion. The kilogram is defined to be the mass of the standard cylinder, not the weight. The weight of an object is the gravitational force on the Earth pulling on the object; the mass of the object, on the other hand, is the amount of matter in that object. So the cylinder can quite easily lose weight -- move the cylinder from Paris to Mont Blanc, the highest point in France, and the cylinder will lose approximately 0.15% of its weight, simply because the gravitational pull is slightly less on Mont Blanc.

The International Committee on Weights and Measures is in an epic tizzy because the standard cylinder is losing atoms. Lost matter means lost mass. So there is no contradiction in stating that the kilogram cylinder has less mass now. The problem lies in that the standard cylinder is not much of a standard if it is changing. Definitions that shift with time are of interest to linguists and philosophers, but they drive scientists nuts.

Vann Priest

Physics Department

Rio Hondo College

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