In yet another Olympian feat of measurement, researchers at the National Institute of Standards and Technology (NIST) recently calibrated a tape that will be used to measure out the distance of this summer’s Olympic marathon—a distance of 26 miles and 385 yards—to 1 part in 1,000.

Measurement is a vital aspect of the Olympic Games. Officials measure the height of jumps, the speed of races, and the mass of weights to determine who wins a medal and who goes home. The marathon is no different. Because of the difficulties in measuring out the distance, the International Association of Athletic Federations (IAAF) only recognized best times and didn’t begin awarding world records for marathons until 2004, when a method using a device called a Jones Counter was officially recognized as sufficiently accurate.

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NIST technician Christopher Blackburn uses a microscope to precisely align a retroreflector
over the center of a hash mark on a measuring tape. Photo credit: Bruce Borchardt

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