The whole problem with the metric system is that it's an arbitarily imposed set of [albeit interconnectable] useless-sized measurements. The reason that all the various "Imperial" measurements existed was that they had been user-selected over millenia, from an almost infinite range of alternatives, as the perfect measurements for that particular purpose. Imposing a single, unified, system has just proved - yet again - that "one size fits no-one."
Gallons were more appropriate for manually-handled liquid purposes; engineers machined in inches [no; never silly fractions - decimal inches - remember "thou?"] Builders had feet and inches [much faster to order - and easier to remember] and surveyors used yards [not much difference there] and joined farmers in using acres; [another much more usable size than hectares.]
Observation seems to indicate that scales of 0-100 fit any particular purpose best. 0-100 deg Farenheit covers the average air temperature of most of the populated areas of the world. So why does the weather forecaster need to use a clumsy scale that is only relevant to the freezing and boiling points of water? [Do they know something about global warming that they're not telling us....]
The danger of imposed, awkward, units is that, inevitably, they will be corrupted by their users. Can you really imagine a builder asking a supplier for "Two thousand, four hundred millimeters of one hundred millimeter by fifty millimeter deal, please" when "8 foot of four-be-two" sounds much more "professional" and is still being routinely used - even for "metric wood." [It's quite fun to watch how fast the the young lads in the builder's merchants - brought up to be exclusively metric - eagerly cotton-on to these "obsolete" - but very handy - units.] We now have "metric inches" [25mm] and "metric feet" [300mm] in common use - no chance of any misinterpretations and conflicts there then... [Well... if French housewives can buy apples in half-kilo "punds"....]
The history of unpopular, centrally inflicted, systems does not bode well for the metre. The Americans still have a major say in international engineering conventions and seem to be rapidly retreating from their flirtations with "this stoopid Uropeen size." Emergent engineering superpowers in the Far East see the US as their main market and are far from naive at selling what the American public want to buy. Flick-switch re-dimensioning in most digital engineering eqipment means that choice has returned and user convenience will always win in the end. Anyone like to speculate at which bits of the metric system will still be around in a hundred years.
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A measurement is a goddam measurement. Doesn't matter what the numbers are or what it's called.
I am firmly reactionary on this one.
Thumb, forearm, bladder: variety is the spice of life.
Metric system was invented, like Esperanto. And it doesn't really deserve to be any more successful than Esperanto.
(Cue for three obsessive backroomers to reveal that they are closet Esperantists).
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It's unusual for me to disagree with you Screwloose, but I think metric will win out.
Science, even in the US, is now routinely done in metric - anyone presenting a technical paper for an international journal will do so in metric. If you try to do any serious calculation in physics or engineering, you just end up with nonsense if you do it in imperial - having tried to decipher some Boeing calcs, I can only describe them as perverse. So, for any work I have done for an American client, I have first converted from nonsense units into more sensible Newtons, metres, litres, etc, done the calculation, then on the last line converted back.
So, as things spin out from science, they will tend to do so predominantly in metric.
On the other hand, during normal travel, I can't picture a kilometre, and I can't imagine buying a litre of beer.
Number_Cruncher
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Don't think there is anybody more anti EU than me but thus is one thing I do agree with.
Imperial measures are just weird and largely just result from historic legacies. Have a little book from the 1930's that shows stuff like chains and drachms. All very nice and twee but this is the modern world and metric measurement are when alls said and done logical.
I am all for it.
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NC
I actually agree that in fields like academia the metric system will stay - simply because it is so fully integrated and is thus by far the best suited system for that particular purpose. It's use in stand-alone applications is where it will either corrupt or disappear altogether.
If someone had come to an old-fashioned engineer in the fifties and said that they were going to do away with the perfectly-suited inch [0-100" covers 99.9% of all machined components and the "thou" is the perfect unit for that job] and replace it with a millionth of a metre; something around a 25th of an inch and then nothing until you get to a bit longer than a yard, they would have been laughed at and told not to be so stupid - or phrases to that general effect. Metric thread pitches are far inferior to UNC and UNF which nicely covered all but a few "special pitch" applications. [Non-fractional metric bolt-head sizes are perhaps an improvement - although a simple numerical system could have evolved for Imperial if it had been needed.]
It's the unnecessary application of the metre and it's related offshoots that will be it's general undoing. It doen't affect a jeweller weighing diamonds if a greengrocer is selling apples by the pound. If either feel the metric system is better for their application - then let them use it; nobody's getting short-changed, the conversion factors are set in stone, so there can be no Trading Standards implication either way. It's the forced replacement by what is often an inferior unit that is wrong - and, sadly, we can't blame the EU for it either.
[I'm just amazed that we haven't had someone bleating-on about fractions and the decimal system - even the BBC had a airhead that didn't know the difference between metric and decimals.]
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It think metric threads are much easier to specify on an engineering drawing - it is simply M?? x p.pp, with ?? giving the major diameter, and p.pp giving the pitch in mm - perhaps with a tolerance class if you want the thread to be always stiff or always loose - it's a doddle.
In comparison with this simplicity, you have different ways to specify UNC, UNF, BSF, BSW, BA, and that's before you get to the awful aerospace specific stuff!
I think that using the measurement in mm across flats to define spanner and allen key sizes is simple and effective. Although I didn't have much trouble with fractional AF spanner sizes, I could very easily get confused with BSW and BSF spanner sizes - nightmare!
That the metric system is based around powers of ten is wonderful for calculations, you know imediately if you see n in front of a measurement, you are dealing with nano somethings or other, and the scaling is clear, simple and obvious - there's no need to bear in mind that there are 12 inches in a foot, or 8 pints in a gallon.
I think that forces are much clearer in metric, Newtons and kilograms are obviously different units, measuring different quantities. lb, and lbf are much more subtle in their difference, and this does confuse engineers who aren't used to imperial - I've seen frequent errors in calcs from junior staff because of this annoyance.
In terms of practical engineering, I think that micrometers in millimetres are, if anything, slightly easier to read, but there isn't really much difference. We are comparing being able to read down to 1 thou, and 0.1mm (about 4 thou) - there's not much in it really.
Like Thommo, I'm not a huge Europhile, but I wouldn't dream of using anything other than metric in my calcs, and on my drawings.
I think the French applications of metric are a little odd, for example, using da as a prefix, rather than the usual prefixes which are three powers of ten apart - i.e., milli is 10^-3, micro 10^-6, nano 10^-9, etc. This keeps the numbers reasonable, and puts the scaling in the power of ten.
Having said all this, I wouldn't dream of enforcing metric on people. I'm perfectly happy buying a quarter of *sarsaparilla tablets from the corner shop, and I haven't a clue what I would ask for in metric. (If only I could find any in the phillistine midlands!)
Number_Cruncher
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I think you'll find that metric measures have been officially authorized in the USA since the mid-19th century at least.
In fact the official American "Imperial" measures are actually decided in relation to the metric system and it's "arbitrary" metal bars, not as an independent system.
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>>"arbitrary" metal bars...
I take it you are referring to the old definition of the metre, being the distance between two marks on a Platinum Irridium bar held at Sevres.
These old arbitrary definitions are one by one being converted into relationships between fundamental constants, such as the number of wavelengths of light from a particular atomic transition.
Number_Cruncher
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Indeed. American metrication dates back to the mid-nineteenth century. I was having a dig at an earlier poster who used the word "arbitrary" to describe the metric system.
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Baskerville
If your reference was to the phrase "arbitrarily imposed system" then there are three OED-listed meanings for arbitrary and that one clearly was not the "mathematics" definition, relating to the use of unspecified values, it was arbitrary used in it's "autocratic" sense.
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So you're unhappy with autocratically imposed measurement systems, but you're happy for the OED to impose arbitrary definitions of words on you. Hmm.
Baskers.
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I thought the metre was based on a sub division of the circumference of the Earth, which being as it was done in Napoleonic times, turned out o be damn close, but... wrong.
JH
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remember "thou?>>
I can look at a gap and estimate it in thousanths of an inch though not so readily microns, I still use thou feelers and convert as required and I have a couple of micrometers that measure in thou and do the job.
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