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Measuring the weakest of forces

Cold atoms detect a 174-yoctonewton force

4:03pm, April 29, 2010

A blob of cold beryllium ions has measured the smallest force yet. The charged atoms registered the minuscule tug of an electric field to be 174 yoctonewtons. That’s about equal to the force of Earth’s gravity on a 70-kilogram human divided by a million, then by a billion, then by a billion again, then by four.

“The forces measured are astonishingly small,” comments quantum physicist Dick Slusher of the Georgia Tech Quantum Institute in Atlanta. Slusher, who was not affiliated with the study, calls the research “wonderful work.”

The measurement technique, developed by researchers at the National Institute of Standards and Technology in Boulder, Colo., may lead to more precise ways of analyzing the fine-grained surface properties of materials.

The NIST scientists first trapped about 60 beryllium ions with electric and magnetic fields. These atoms were then cooled to about half a millikelvin with lasers. At such cold tempera

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