When you’re a kid, you look forward to your birthdays. When you’re on the wrong side of 40, not so much. But here we are again. As the Stoic philosopher Marcus Aurelius said, our lives are circumscribed in space, and that never bothers us. Why should we get all bent out of shape if they’re also circumscribed in time?
That big gadget in the photo is called a slide rule. Slide rules are non-electronic calculators that were used until the 1970s. NASA even used them to do calculations for the moon landings in the Apollo missions. You can multiply, divide, take square roots, calculate trigonometric functions, and all kinds of other things. There were also specialized slide rules for engineering, electronics, and other fields.
I collect slide rules, though it’s been a while since I found a new one. I looked far and wide for a large demonstration slide rule like the one shown in the photo, but I could never find one outside of a museum. I think they used to be pretty common in college classrooms, since STEM majors needed to learn how to use slide rules. Here’s part of my collection:
About 15 years ago, I was taking a pharmacology class — just for entertainment — and the professor gave us a pop quiz. I didn’t have a calculator with me, but by chance, I had a pocket slide rule in my shirt pocket. So I pulled it out and started doing calculations. After a minute, it dawned on me that the room had become very quiet. I looked up, and all the other students were watching me. They had no idea of what I held in my hands. The professor just laughed, since he had used slide rules when he was a student. After class, I showed the other students how it worked.
In the 1970s, of course, easier-to-use electronic calculators replaced slide rules. Today, increasingly powerful phone apps are replacing electronic calculators. Who knows what will come next: brain implants? We’ll see, I guess.
Here’s an incredibly good movie about something we did with slide rules. If you miss it in the theatre, be sure to get the Blu-Ray or watch it online. It’s amazing:
The Thousand-Year View 
My grandfather was a mechanical engineer who worked in some capacity on the space program. My grandmother, who inflated his accomplishments, says that he was on the team that designed the landing gear for the moon unit for Apollo 11.
I have his slide rule.
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Awesome! Then you really need to see “Apollo 11.” It’s an amazing movie. Maybe you can even catch a glimpse of your grandfather in one of the group shots.
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