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The 39th Root of 92

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Re: The 39th Root of 92

#81

Post by engi_nerd »

rm445 wrote: post #58
engi_nerd wrote: post #33

Earlier quoted context omitted.

Okay, I'll play devil's advocate here. There's a huge (but not insurmountable) lock-in effect behind wire gauges. All the wire I can buy is sized in it. All the wire strippers, crimpers, pins, sockets, plugs, jacks, terminal strips, insert/removal tools and clamps I can buy are sized around the AWG standards. Bulkhead passages in ships and aircraft are sized for carrying certain numbers of wires of certain gauges in…

Yes, that's the core of the issue. The US is a big monobloc, an economic superpower with not only the most advanced economy but also a lot of the history tied to developing the world's industries. Other places saw more benefit to adopting SI units either because they were smaller and closer to lots of other places with a need to harmonise, or playing catch-up. My own country, Britain, falls in the first group - thoug…

I agree. The only way things in the US will change with regards to standards like this will be if it becomes excruciatingly painful to continue being different.

Re: The 39th Root of 92

#82

Post by majewsky »

Hondor wrote: post #72
disc wrote: post #62

Earlier quoted context omitted.

Wouldn't a much more natural unit for angular measurements be 1/(2*pi)? That way angular measurements are represented as their fraction of a circle (which is pretty easy to visualize; 180 degrees becomes 1/2.)

You'd lose the definition of angle as arc length / radius, which would make your proposed unit just as arbitrary as degrees - most formulas involving angles would need to contain a conversion factor. You'd also lose the small-angle approximations sin(theta)=tan(theta)=theta which in my field are used extensively to convert nonlinear to linear equations. Nonetheless, your proposed unit already exists and is called tau…

The most relevant point here is that the natural choice of units is very subjective and depends on the task at hand. For example, particle physics uses "natural units" where all units are powers of gigaelectronvolts: https://en.wikipedia.org/wiki/Natural_units#.22Natural_units...

Re: The 39th Root of 92

#83

Post by woliveirajr »

function_seven wrote: post #69
HCIdivision17 wrote: post #20

Earlier quoted context omitted.

That's the trick. In a sense, the units follow the application, and hence English units always feel a bit natural. They have a tendency to have integer multiples and simple fractions. And when I say natural, I don't mean elegant. They often tend to be thoroughly arbitrary. But they match the needs, which is usually reasonably pragmatic. For example, 360 degrees is ideal for simple in-head directional geometry, but ra…

Regarding your PS: The most baffling measurements to me are tires. The diameter is expressed in inches, the width in millimeters, and the sidewall thickness is given as a percentage of tread width. So you get 255/40R17 to describe a 17” tire that's 10” wide with 4” sidewalls. (Or a 430mm tire that's 255mm wide with 100mm sidewalls)

And try to replace your wheel, for example, for one that has 16 or 18 inches, and calculate the size of the tire to have the same final size...

Re: The 39th Root of 92

#84

Post by VLM »

engi_nerd wrote: post #33
jonahx wrote: post #16

Earlier quoted context omitted.

> There must be some sociological phenomenon going on that keeps the US from adopting modern units. Maybe can't admit a shortcoming and fix it? There's a sociological phenomenon at play here all right... a deeply pathological form of envy that Freud called "denial of USA-number-one-ness."

Okay, I'll play devil's advocate here. There's a huge (but not insurmountable) lock-in effect behind wire gauges. All the wire I can buy is sized in it. All the wire strippers, crimpers, pins, sockets, plugs, jacks, terminal strips, insert/removal tools and clamps I can buy are sized around the AWG standards. Bulkhead passages in ships and aircraft are sized for carrying certain numbers of wires of certain gauges in…

A somewhat more interesting problem is we live in a centrally controlled economy with many centers. There's a paperwork storm downstream of thousands of local building codes. Most are minor variations on minor details of the NEC, but it would be a huge job to harmonize and metric-ify them. For example where I live, politicians "had to do something" after someone died in a pool electrocution decades ago, so our local code is NEC plus a microscopic tightening of 1950s NEC swimming pool regs (which ironically are probably looser than 2016 NEC swimming pool regs, negating the politicians intent from decades ago).

Anyway at least for awhile if you want legal electrical work done, you're going to have an incredibly expensive and dangerous cutover. Its likely that cutover to metric related mistakes will cause as much property damage and death as "X" years of not harmonizing under one system. Where "X" is probably many more years (lifetimes?) than you'd expect.

Re: The 39th Root of 92

#85

Post by kevhito »

int_19h wrote: post #60
kevhito wrote: post #18

Earlier quoted context omitted.

If you have never wired a house for electrical, then sure, the units seem arbitrary. But if you do, then the units seem very comfortable. 12ga for most typical 20a circuits, 14ga for light, 10ga or thicker for some heavy-duty circuits. Hey boss, we seem to be all out of 3.31mm^2 romex, all I got left is 2.08mm^2. And why did you mention cross-sectional area? Why not radius? or diameter? Or better yet, circumference?…

The "it's more natural" argument, fielded by both sides, is largely a myth - take it from someone who lived in several countries and struggled with different units. Pretty much the only reason why something feels natural to you is because that's what you are accustomed to using. There's nothing more natural about an inch than a centimeter, and nice, round, easy-to-remember numbers can be had on both scales for "natur…

You may have a point when it comes to mm vs. inches, etc. But my post was about logarithms vs. cross-sectional area vs diameter vs. circumference. Does your point still hold?

Re: The 39th Root of 92

#86

Post by zokier »

kevhito wrote: post #85
int_19h wrote: post #60

Earlier quoted context omitted.

The "it's more natural" argument, fielded by both sides, is largely a myth - take it from someone who lived in several countries and struggled with different units. Pretty much the only reason why something feels natural to you is because that's what you are accustomed to using. There's nothing more natural about an inch than a centimeter, and nice, round, easy-to-remember numbers can be had on both scales for "natur…

You may have a point when it comes to mm vs. inches, etc. But my post was about logarithms vs. cross-sectional area vs diameter vs. circumference. Does your point still hold?

Cross-sectional area is most important metric for wires because it is directly (and linearly) related to resistance which in turn is related to current carrying capability.

Re: The 39th Root of 92

#88

Post by zokier »

einhverfr wrote: post #31
HCIdivision17 wrote: post #29

Earlier quoted context omitted.

I feel like unit debates often result from a misunderstanding between sides of "is perfect the enemy of good?" I thought it suspicious that they would have miscounted the days, but you're right: it's so dang useful that it's worth a little error (with occasional corrections) for such convenience. Of course, at some point it becomes a huge pain and you buckle down and choose something just as arbitrary but easier to h…

How many kiloseconds will you spend working next week? Even in metric-using countries, nobody uses it for time. For actual applications of spherical trig though degree, minute, second makes a lot of sense, primarily because the earth rotates about one arc second every 4 minutes, and if you know this then you can do manual navigation via the stars and many other things. However for many things I do use metric time, ju…

I for one would love to have metric time. Just today I had to add some durations together to get total duration, which would have been simple thing to do with metric time.

Of course for practical use using SI second wouldn't be very good solution. Traditionally second is derived from the length of day, and I think that would make sense for metric time too. 1 milliday would be somewhat close to 1 minute and 50 millidays (or maybe half deciday) would be close to one hour. Of course the name probably should be something else than "day" to reduce confusion.

So I could be working something like 16 decidays next week.

Re: The 39th Root of 92

#89

Post by adrianratnapala »

exDM69 wrote: post #75
adrianratnapala wrote: post #37

Earlier quoted context omitted.

As much as I hate the metric system myself, I don't think it's true that U.S. measuring culture is a self-consistent system that avoids unnecessary conversions. For example the energy content of fossil fuels tends to be measured in BTU per (whatever), while electrical energy is measured in kilowatt hours. On the other hand, automobile engines are often rated in horsepower. I find this sort of thing is ubiquitous in e…

In imperial vs. metric, I don't think the actual units are as big of a difference as the convention of using fractions vs. decimals. When doing manual work, e.g. woodworking or metalwork it's pretty convenient to use fractions. You tend to divide things in half or quarters. With most things not made by hand any more, using fractions and inconsistent units like inches, feet, yards and miles is a nuisance for engineers…

Inches, feet, and yards and miles aren't really inconsistent, becuase they are all related by somewhat reasonsable integer ratios. In this computer age, there isn't even much advantage in replacing all those ratios with powers of ten.

It's when people inflict mixtures of BTUs with h or Joules with eV on us that I get aggravated. Each of those units has its place, but only in particular domains. Worse, the people most likely to use domain-specific units, are the ones most likely to not name the unit they are using.

Engineers are such people.

The SI system helps reduce the risks a little. But only a little, I have seen German engineers measure velocity in degrees.

Re: The 39th Root of 92

#90

Post by Turing_Machine »

int_19h wrote: post #61
Turing_Machine wrote: post #46

Earlier quoted context omitted.

Most people never use units smaller than can be accounted for by fractional inches and ounces in their daily lives, and never did. The only people who ever used grains were pharmacists, jewelers, and the like. The only people who ever had to resort to thous were precision machinists and the like.

Open Amazon, and search for something as mundane as plastic bags or trash cans. Notice that their thickness is specified in "mils". How many people make purchasing decisions on those products, for use in their daily lives?

All you need to know there is that a 3 mil is thicker than a 2 mil. That doesn't require any kind of calculation at all.
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