In the beginning, all that Stephan Schlamminger wanted to do was to write down an equation that would help him obtain a more precise value for G, the gravitational constant that determines the strength of the attraction between massive objects. To gauge that attraction, Schlamminger, a physicist at the National Institute of Standards and Technology (NIST) and his colleagues, studied the motion of a so-called torsional pendulum—in this case, a set of masses suspended by a thin wire that periodically twists and untwists instead of periodically swinging back and forth.

The equation that Schlamminger derived provides guidance about how to minimize or quickly dampen the amount by which the wire twists back and forth. If the amount is small, it’s easier to locate and measure the position of the wire, which translates into a more accurate measure of G. Schlamminger was eager to immediately publish the result. But then he got to thinking: The finding would interest only a small number of people, those who measure G using the torsional pendulum method.

Could the equation be applied to other devices?

Turns out he didn’t have to crane very far to find a connection.

In an article posted online Feb. 17 in the American Journal of Physics, he and his colleagues describe a surprising link between their equation for G and the maneuvers required for crane operators at a construction site to safely and quickly transport heavy loads.

Schlamminger, of course, wasn’t initially thinking about construction cranes. But he remembered a conversation he had when he was a postdoc about 15 years ago, while working on a similar project to measure G at the University of Washington in Seattle. Schlamminger’s advisor had asked him if he knew about the tricks of the crane operator.

Operating a crane isn’t for the faint-hearted. Swing a thousand-pound chunk of steel too fast or too far and someone can get killed. But in just two carefully choreographed maneuvers, a skilled crane operator can pick up a heavy load and bring it to a dead stop, without any dangerous swinging, to exactly the right destination. Moreover, a crane’s cable and the load can be modeled as a vertical pendulum that moves to and fro in a manner similar to the way that a torsional pendulum twists and untwists. The time that it takes for the pendulum to complete one cycle of this motion is called the period.

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