More than a thousand miles west, Laurie Emery, a math teacher at South Winneshiek High School in Calmar, Iowa, will teach her junior pre-calculus class how to do intricate calculations without a calculator. And when she covers the history of the computer, she teaches students how to use a tool she remembers watching her father use as he calculated their family's finances. Sister Paula Irving, a nun at the Community of Jesus in Orleans, Mass., teaches a computer programming course to homeschooled high school students. Here and there, teachers like Jim Hus still use them in the classroom. But slide rules can also handle multiplication and division, find square roots, and do other sophisticated calculations.
In its simplest form, the slide rule adds and subtracts lengths in order to calculate a total distance. It was based on John Napier's discovery of logarithms. The first one was built by William Oughtred, a cleric teaching math in England in the 1600s. Each section has scales - numbers and line marks for calculations. They are divided into thirds, the top and bottom are fixed in place, but the middle section slides back and forth.
Slide rules are typically rectangular and about the size of a ruler. "The size of a sewer pipe, the weight-bearing ability of a cardboard box, even rocket ships and cars." The museum just ended a three-year exhibit on slide rules. "The slide rule is an instrument that was used to design virtually everything," says Deborah Douglas, the director of collections and curator of science and technology at the MIT Museum in Cambridge, Mass. It's said that Buzz Aldrin needed his pocket slide rule for last-minute calculations before landing. NASA engineers used slide rules to build the rockets and plan the mission that landed Apollo 11 on the moon. That seemingly simple tool has a serious resume. It's a powerful mechanical computing device, often no larger than a 12-inch ruler, marked with numbers - but part of it slides in an out to to show relationships between different sets of numbers. "Let's do those multiplication problems again."įor the next calculations, Hus's juniors and seniors at Highland High School in Highland, Ind., will use a different tool: A tool that dates back 400 years.īefore the smartphone, the laptop and the graphing calculator, there was the slide rule. "Take your batteries out," Jim Hus says, watching his pre-calculus students remove the AA batteries that power their calculators. We start off with a device that once was essential to higher-level math, in school and in the workplace, but now has all but disappeared:
Slide ruler series#
Today, NPR Ed begins a new series examining these icons of the classroom. These tools of the education trade become part of our lives for a semester or two and then we move on. Drawing arcs and circles with a compass in geometry.