Write-up for Metric System (the Coolest of all Cool Tools)?
I'd love to see the Metric System written up on Cool Tools. No other tool/system comes close to its ubiquitous usefulness, dead easy common sense and universal consistency. But I lack the professorial credentials to do the topic justice.
The more Feynman-esque, I think, the better. Please rise to this challenge, someone wonderful!0
It does make sense, hence not anywhere to be found in the USA! How you guys became a super power is beyond me.
I spent my first 30 years in the US, but have now lived almost as long in a metric country. Metric is useful and easy. Perhaps it might be better a group effort, with different authors writing about how they use metric for different applications.
For example, I do a lot of my own home repair and the usual DIY stuff, and now do all of my measuring in metric, even to the point of converting English measurements into metric when measuring wood, installations, and similar. I think it would be good if the authors could tell how they deal or dealt with two systems, transitions, and how the change was worth it.
Sorry, I disagree. The metric system doesn't work properly on a human scale.
I'm not going to try to dissuade you from employing it for science or engineering, in those spheres its consistency, universality and (relative) ease of calculation are strong advantages but for everyday use by people doing things that most people do it is unwieldy and contrived.
In the US you mostly use cup measurements for cooking. Simple and quick halving and doubling starting from amounts that produce the right quantity for a family of four. Try that with with metric- 37.5g of butter anyone? How long is that pencil 7' (7 x the width of my thumb knuckle) or 18cm? A foot, most of us have a way of measuring that and a yard too. Buying timber? a 6ft piece of 2 x 1 or two is just what I need for this project. How many 1.8m lengths of 5 x 2.5 I'd need is harder to visualise and worse, harder to split into usable fractions/pieces.
Here in the UK we've been using both for decades but ask any child how tall they are and they'll tell you in feet and inches. Mothers know that their baby weighed just a little less than 8lbs at birth. Human scale things are easiest measured with human scale things, like the size of parts of our bodies because we have them with us all the time.
When my daughter was 9 she knew that inches were smaller than feet, that feet were smaller than yards and that yards were smaller than miles. She'd been taught the metric system since starting school but was as likely to label a aeroplane wing in kilometres or millimetres as metres or centimetres.
The metric system makes a fetish of the decimal point and don't get me started on the European standard that removes commas for separating 1000s.
Metric isn't awful, it's useful and indispensable in technical areas but it plain sucks for everyday, informal use. In fact it sucks as much as Fahrenheit does for everyday use.
Maybe you have a head for fractions. For me, the last thing I want to do is some mental math when measuring for a project. It's like an all day third grade math lesson in fractions.
It's funny, I always assumed that the comfort that we feel with our particular measurement system is due to being raised with that system. In the 70's in the US, there was a big push towards the Metric system in schools, and consequently every kid I knew picked it up almost instantaneously. Unfortunately, I believe it was the jingoistic 1980's that squashed that movement, along with almost anything that smacked of foreignness, or worst of all, french-ness.
As for the UK, I've never seen such a hodgepodge of measurement systems: roads are marked in MPH, weights can be pounds, kilos, or stone, bolts can be imperial, metric, or Whitworth. Whitworth?!? Don't even get me started on Imperial gallons vs US gallons. Where did the word "gallon" come from anyway?
The problem with using metric for cooking mostly stems from using mass (metric) vs, volume (cups, tsp, tbsp, etc) not necessarily the system of measurement. Although I don't think measuring flour in centiliters would be much better.
By S. Marshall Priddy via Quora's "Why did the U.S. halt plans to convert to the metric system?":
It's really like having all numbers retained in Roman Numerals because the majority never does anything more complicated than read a clock, thus requiring any accountant or engineer to translate anything they do in decimal numbers into Xs, Vs, and Is before sharing with the public. It's absolutely ridiculous.
I will say this with absolutely no equivocation: if you think that continuing to resist the metric system is a good idea, you might simply be irascible and stubborn, but the odds are vastly higher that you are simply too ignorant to recognize how absolutely awful SAE units really are because you've never actually needed to use them in ways that matter. You must have a perspective rooted solely in consumption, because pretty much every single innovator, scientist, or engineer who has ever had to use them both will know with absolute certainty that the metric system is 100% superior to SAE in every single way.
SAE is like Roman Numerals, or the abacus/slide ruler (compared to a digital calculator), or non-alphabetic written languages. If you actually understand the comparison, it's a no-brainer, and if you think SAE/Imperial units are just fine, you are ignorant of the actual nature of the comparison. All you're doing is condemning the next generation to learn the same ridiculous and backward crap that you learned, delaying integration and making everything unnecessarily more difficult.
I'll follow up with a Reagan quote (since he seems largely responsible for having nixed the switch; it looks like he took it from George Romney): "If not us, who? If not now, when?" He applied this to issues of greater importance, sure, but the sentiment itself remains the same. Every year we don't make the transition is just another added weight to how difficult the change will be when we finally make the switch.
Edit: This entry has received a great deal of attention (both positive and negative), and overall it has vindicate my point fairly well about people criticizing what they do not understand. Allow me to clarify to help explain to the unconvinced what the advantage actually is.
First, the use of the metric system has essentially nothing to do with “multiples of 10.” Technically it does, sure, and technically there are those deci- and deca- and centi- prefixes. However with the exception of a handful of things like the centimeter, the centipoise, and the decibel, these are used very infrequently, and the vast majority of steps a person takes are going to me the thousand-fold steps made familiar largely by computing: kilo, mega, giga, tera, peta, milli, micro, nano, femto, pica, etc.  95 times in 100, I would rather talk about 50 mm than 5 centimeters due to the clarity in making calculations.
However, I make this point emphatically that I do NOT favor the metric system owing to the ease of using numbers like 1,000 or 1,000,000 rather than numbers like 12, 3, 5,280, or 16; all of those are at least whole numbers, and with the lone exception of 5,280, they are all pretty easy to remember.
The number that I don’t like in Imperial or SAE is 1.057. What’s that number? That’s the number of kilojoules in a BTU (approximately). Or there’s the number 0.293071, which is the number of watt hours in a BTU. Or there’s 252 "little calories" in a BTU, or 0.25 kilocalories, or 25,046 foot-poundals, or 780 foot-pounds-force, or 5.40395 (lbf/in²)·ft³ in a single BTU.
And that’s just the BTU. The problem is that Imperial units aggregated a countless number of these different random ways to measure things, like pressure being in pounds per square inch or atmospheres or Torr, and mass might be in pound-mass or slugs or blobs (I’m not making those up) in addition to the ounce—which might be an ounce, a fluid ounce (which is not a measure of mass at all), an imperial ounce, or a troy ounce.
But even this is not the whole problem; it’s just the start of it. Let’s take a step back.
In all the known universe, there are a total of seven primary dimensions into which all measurable values can be broken down. These are length, mass, time, temperature, luminosity, electric current, and amount of substance (number of particles). Everything else can be derived as some factor of this. For instance, force is (as Newton established) mass times acceleration, and acceleration is distance per time per time. Energy is just force times distance, and so forth.
The advantage this leads to in SI is in trying to convert between different ways of looking at a derived unit like the joule for energy.
How many kilogram meters squared per second squared are in a joule? Exactly 1.
How many newton meters are in a joule? Exactly 1.
How many pascal cubic meters are in a joule? Exactly 1.
How many watt seconds in a joule? Exactly 1.
How many coulomb volts in a joule? Exactly 1.
No matter what field you’re working in, no matter how you’re trying to see energy created or energy used, you have a single set of systems. A person might want to calculate how much natural gas it might take to generate the electricity for a television to operate for an hour. Rather than the language of combustion having one set of units, of electricity generation having another, and of personal electronics using a third, there is a single language that speaks to all three. If you want to calculate how much ice a volcano can melt (something I think I actually did on the day I wrote this original answer in looking at the situation in Iceland at the time), or the blood plasma concentration of a drug 3 hours after administration, or the viscosity of a fluid as it begins to freeze, or the temperature dependence on rates of adsorption of a vaccine to an adjuvant, there’s a single language that can speak to all of these problems. When you have an interdisciplinary application in bioengineering or geology, both sides speak the same language, and you can do the entire set of calculations without using any conversion factors whatsoever. If you understand the base units of every metric—that the units for viscosity are mass per length per time, or that the units for electric potential are mass area per current per time cubed—then you can infer what the base units would be, and hence you can determine how the one would dissipate energy or the other would create energy directly. If you’re trying to determine the strength a motor would need to have to be able to shift a plate of a given mass, with the mass moving along with the plate (something I recently encountered) the task is amazingly straight-forward.
I can appreciate that this seems trifling to anyone that doesn't actually have to do it. It’s always easy to just presume that whoever is responsible for making things happen will make it happen, and if that’s a little bit harder they should just shut up and buckle down and do whatever they need to do behind the scenes to make my life feel seamless and prosperous without any hassle. I call that expectation unreasonable, and whenever there’s a cost you don’t know about that doesn't mean it isn't passed on to you.
Every one of us is paying daily in those prices increased for a decline in efficiency or an increase in errors. That the effects are singularly subtle does not preclude them being both real and significant in the aggregate.
 Technically the computer science scales refer to 1,024, or 2¹º rather than 10³. This is somewhat beside the point here, but I point out this fact just to note that I am aware of the differences. The fact that computer science uses 1,024 rather than 1,000 is largely beside the point here because I don’t really care about the 1,000-fold aspect of the metric system that much.
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