u/arcfide

I've always admired slide rules. It wasn't until recently that I decided to actually learn to use one, just for the fun of it. I can't deny that they are fun, and they have a certain elegance to them.

However, as I'm learning to work with one, I'm struck by the -- to me -- very harsh limitation in significant digits.

In my mind at least, the whole point of a slide rule was to help you do calculations that would have otherwise been challenging to do quickly and easily with pen and paper. That's how I had always seen them.

Now, it seems that the net effective mantissa size on a slide rule is maybe in the range of 3 significant digits most of the time. Maybe, if you happen to get the right numbers, you can get somewhere in the range of 4 digits, or if you have a big rule, you can eek out 5. But at that point they aren't very portable.

But that effectively limits you to multiplying double digit numbers if you hope to preserve exact precision. And double-digit multiplication and division is darn near mental math territory, to say nothing of pen and paper efficacy. I can scribble out a solution to double and triple-digit math almost effortlessly and very quickly, with very little paper use.

And the moment you start doing tricks to increase the precision level, your operations for a solution start to be very close to the operations you need just to get the answer with pen and paper in the first place, and you have to resort to addition in many cases anyways. The mental load seems surprisingly high.

Now, I'll readily admit that my area of expertise is in Computer Science, and in that field, our normal working numbers are almost always outside of the range of the precision of a slide rule, and anything small is easily mentally calculated or pen and paper will do just fine, but importantly, if we need enough precision to get the precision level that I could get from a slide rule, then I'd definitely want enough precision for an exact answer, which would seem to make a slide rule a strange middle ground in which pen and paper is ironically better and faster at getting a good result for a computer scientist than would be a slide rule (assuming we wanted to avoid using electronics for calculating, for some weirdo reason).

That's surprising to me, and makes me wonder if I'm missing something or I am just really slow at using a slide rule? I mean, what am I missing? What can you possibly do well and precisely with a measly three digits of significance that can't be done just as easily with mental math or pen and paper?

I did some random number generations just to try doing some more complex calculations, such as

24265×95630
43136×77777
...

And so forth, but I couldn't easily get these numbers done with a slide rule in anywhere close to a smaller number of operations than just doing it with pen and paper. So, what am I missing here?

Today we often have a set of more or less defined watch categories, such as dive, sport, GMT, pilot, chrono, and dress watches. The historic origin of certain categories which are defined by their features rather specifically are easy to pin down (GMT, dive, field, chrono, and to a lesser extent, pilot watches).

However, today we often see more nebulous categories used by companies and enthusiasts, namely, sport watches, dress watches, "complicated" watches, "classic", and such. These categories are often associated with, ostensibly, a historical usage based on situation, rather than a specific feature set.

For example, you'll often read about the JLC Reverso being originally a "sport watch" designed for polo, and ladies bracelet watches as early "dress watches" of a sort.

This becomes particularly prominent when you talk about social dress norms and various etiquettes around watches. There's at least a perception around dress watches being appropriate for certain occasions more than others, and sport watches being likewise more appropriate for some situations than others. Obviously, there's always a component of the crowd that argues against such convention, but the convention at least exists to some degree, even if most situations fall somewhere in the grey.

But if I look back historically, I do not see much evidence for these categories in traditional watch advertising or usage. When did the watch community and social convention as a whole begin to separate out various watches into these different segments?

The Reverso and DateJust are two examples of watches which have clear early advertising that promotes these watches in ways that today are associated with the sports watch category (or casual category), but at the same time, are also seen in places that we would associate as "dress watch territory", also. So too the Cartier Tank, and so forth.

Indeed, there are numerous examples throughout the 20th century of watch advertisements that take everything from a submariner to a fairly dressy (by today's standards) watch and put them on everything from tuxedos to suits to the auto mechanic's uniform.

So, when did social fashion begin to shift in how we think of various watch categories? Are some of the historical appeals to convention anachronistic?