Memory Lane: The Slide Rule

My wife and I last night were reminiscing about slide rules. I wonder how many of you are old enough to have learned how to use a slide rule. I wonder how many of you have ever seen one.

The slide rule was invented in the 17th century, modified and improved throughout its history, and taught in schools during the 1950s and early 60s. I had one, although I don’t know what happened to it. Wernher von Braun had two slide rules which he acquired in the 1930s and continued to use for the rest of his life, including for his work leading the U.S. space program in the 1960s. It would not be an exaggeration to say that this bit of 17th-century technology helped put a man on the moon in 1969.

Slide rules came as straight rulers with sliding sticks and a cursor, with later models done up as disks or cylinders. Electronic computers made them obsolete by 1974. You can still get them, you can still learn how to use them, and they will still give you the right answers to multiplication, division, square roots, and trigonometry problems. But they are obsolete.

Slide rules have two advantages over computers. Electrical power failures, hiccups, and glitches don’t affect them, and they never need those blasted updates. The down side is that they’re harder to learn than computers: a chowderhead will not be able to use one.

Let’s hope there will always be a few people around who own slide rules and know how to use them. They may be needed again, someday.