The science of calibration dates to 1949, when the U.S. Air Force was figuring out how many G's a human being could endure. That is, they wanted to know how to calculate gravitational force, G-force, which feels like weight to the test subject but actually results from acceleration. By definition, it is the effect of force on an object per unit of mass.

The USAF experiment was known as MX981: Human Deceleration Tests. At the time, most experts believed that 18 G's was the absolute maximum that anyone could survive. Captain John Paul Stapp, who headed the MX981 project, thought otherwise.

At Muroc Army Air Field in California, the MX981 team strapped test subjects (including Stapp) to a rocket sled nicknamed “Gee Whiz,” propelled them at 200 miles per hour along a half mile track, and then brought the subjects to a stop in less than a second. Then, they monitored the results.

Often, the results were not good. Captain Edward A. Murphy, Jr., an engineer on the experiment, arrived at the idea to plant strain gauges in the sled harness to quantify the force of gravity inflicted on Gee Whiz’s riders.

After the first test run that made use of these gauges, Murphy noticed that they had failed to record anything. After examining the gauges, he discovered that one of his two assistants had installed them backward. According to the story, Murphy said, “If there’s any way they can do it wrong, they will.”

A few weeks later, when the press questioned Stapp about safety concerns at MX981, he reportedly answered, “We do all of our work in consideration of Murphy’s Law.” Pressed to explain, Stapp gave some iteration of the idea, “if something can happen, it will happen.” Today, thanks to Murphy and Stapp, and MX981, we have the indispensible axiom, “Anything that can go wrong will go wrong.”