NavList:

Alan wrote:
"have we forgotten the slide rule, might be another question."

Yes. With minor exceptions, slide rules are forgotten. Those exceptions are generally "slide rule enthusiasts". The number of people using slide rules today in a context that is practical in any sense (as opposed to entertainment for fans) is, I am confident, far less than the number of people navigating with sextants. There are no ocean sailing licenses, engineering licenses, or other licenses that require the use of a generic slide rule. I am sure we could find cases of special-purpose manual calculators that could be shoehorned into the slide rule category to boost the numbers. But even there, in the real world, they have been long since replaced by calculators, spreadsheets, smartphone apps, etc.

Why not? Why aren't people using slide rules? Obviously, basic electronic calculators are dirt cheap. Even for addition, most people today under the age of, perhaps, fifty use calculators and really can't get by without one. Calculators are familiar, cheap, more accurate, faster, and easier to use. If you watch people who need to do regular addition and small multiplication problems (like restaurant servers who want to know what 18% of $45 would be, e.g.), they will do that work in a calculator app which physically and functionally mimics a cheap handheld calcultor on their phones. If anyone should hapen upon a human being who uses a slide rule to figure out a tip, get a net, capture that endangered specimen, and deliver to the nearest zoo with a breeding program for Calculopithecus antiquarius. Said specimen will probably thank you for it!

But there's more to it. Slide rules are non-trivial to use. Any potential slide rule user has to study the device, learn how to use it, experiment, and test out the skill. This is not a replacement for a calculator. It's far more difficult.

Eighty years ago, a little skill with a slide rule could go a long way. There's a delightful story of a billionaire entrepreneur who got his start by pretending that he was a slide rule expert. His name was Sidney Frank. From his obituary in the NY Times in 2006: "[He] was forced to leave Brown University as a freshman when his money ran out, went on to concoct spectacularly successful marketing campaigns for Jägermeister liqueur and Grey Goose vodka, then became so rich he gave Brown its biggest gift ever". I heard about this guy many years ago. Just another ostentatious salesman. Later I learned that he was a "local" who grew up not far from Mystic Seaport Museum, where I have taught many of my celestial navigation classes. More about his donation and legacy at Brown.

From the same obit: "When he ran out of tuition money [and had to drop out of Brown University], he applied for a job at Pratt & Whitney [East Hartford, Connecticut]. There were many applicants, and he was told to come back in a couple of hours to demonstrate that he knew how to use a slide rule, which he did not. He bought one, pored over the directions and got the job."

We can assume that he did not really learn how to use a slide rule properly in a a few hours, but he knew enough to bluff his way through the interview, and he was a natural salesman. No doubt the slide rule became part of his daily routine in the few years that followed while he was employed by PW.

Frank Reed