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I live in Canada. Before that I grew up in a metric country. Though Canada is metric, I use imperial measures here and there.

I use miles for the sport of running. This is because 1609 meters is close to 1600. Four laps around a standard 400 meter track is about a mile and everything follows from that. All my training is based on miles. I think of paces per mile. If I'm traveling abroad and some hotel treadmill is in kilometers and km/h, it annoys the heck out of me.

However, paradoxically, road signs and car speedometers in miles and miles/hour also annoy the heck out of me; though at least since I use miles for running, at least I'm no stranger to the damn things.

For laying out circuit boards, I use mils, which are thousandths of an inch: they are a subdivision which gives a metric air to an imperial measure. This is not just personal choice: they are a standard in the electronics industry. The pins of a DIP (the old-school large one) are spaced exactly 100 mils (0.1") apart, and the rows are 300 mils apart. So you generally want a grid in mil divisions. (The finer-grained DIPs are 0.05" -- 50 mils.).

There is something nice about a mil in that when you're working with small things on that scale, it's just about right. A millimeter is huge. The metric system has no nice unit which corresponds to one mil. A micron is quite small: it's 25.4 mils. (How about ten of them and calling it a decamicron? Ha.)

Inches themselves are also a nice size, so I tend to use them for measuring household things: widths of cabinets and shelves and the like. Last time I designed a closet shelf, I used Sketchup and everything in inches.

Centimeters are too small. Common objects that have two-digit inch measurements blow up to three digits in centimeters.

Centimeters don't have a good, concise way to express the precision of a measurement (other than the ridiculous formality of adding a +/- tolerance). In inches, I can quote something as being 8 1/16 inch long. This tells us not only the absolute length, but also the granularity: the fact that I didn't say 8 2/32 or 8 4/64 tells you something: that I care only about sixteeth precision. The 8 1/16 measurement is probably an approximation of something that lies between 8 1/32 and 8 3/32, expressed concisely.

In centimeters, a measurement like 29 cm may be somewhat crude. But 29.3 cm might be ridiculously precise. It makes 29.4 look wrong, even though it may the case that anything in the 29.1-29.5 range is acceptable. The 10X jump in scale between centimeters and millimeters is just too darn large. The binary divisions in the imperial system give you 3.3 geometric steps inside one order of magnitude, which is useful. For a particular project, you can chose that it's going to be snapped to a 1/4" grid, or 1/8" or 1/16" based on the required precision.

So for these reasons, I have gravitated toward inches, even though I was raised metric, and came to a country that turned metric before I got here. (And of course, the easy availability of rulers and tape measures marked in inches, plus support in software applications, and the enduring use of these measures in trade: e.g. you can go to a hardware store in Canada and find 3/4" wood.)




Some things are traditionally measured in inches even worldwide, like screen diagonals or pipe diameters or, as you have noticed, mil grids. But in any other cases, seeing those feet, yards, miles and pounds in some internet resources presumably made for _international_ audience annoys the heck out of me. In our country (tip: Ukraine), not any ruler or tape measure even has inch marks, yet they are optional here when centimetres are a must. But as soon as I see a video about something "that's 36.5 feet tall", I have to run a conversion to find out what is it in metres. Pretty much the same as the case with some foreign and non-universal character encoding (when everything I see is just garbled letters and/or squares).

P.S. And yes, my ruler is made from aluminium, not aluminum.


Aluminium is an English word used in the UK.

Both the words "aluminium" and "aluminum" are British inventions. Both derive from "alumina", a name given in the 1700's to aluminum oxide. That word comes from the Latin "alumen", from which the word "alum" is also derived.

"Aluminum" was coined first, by English chemist Sir Humphry Davy, in 1808. He first called it "alumium", simply by adding "-ium" to "alum" (as in, the elemental base of alum, just like "sodium" is the elemental base of soda), and then added "n" to make "aluminum". In 1812, British editors replaced Davy's new word with "aluminium", keeping Davy's "n", but restoring the "-ium" suffix which coordinated with the other elements like potassium.

North Americans stuck with Davy's original "aluminum".

In Slovakia, we have a nice word for it: hliník, derived from hlina (clay).




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