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.”

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