It’s true that Celsius isn’t any more ‘metric’ than Farenheit, but the rest of the metric-bashing struck me as strange. A system survives becuase:
a- it’s useful, and
b- nobody cares enough to make the effort to change it.
The U.S. can happily keep using “imperial” measurements forever becuase they have such a huge amount invested in it. Besides, most of the obscure measurements that anti-imperial types (rebel forces?) hold up as examples that the whole system should be junked have fallen out of use anyway. If a person is satisfied with inches, feet, yards and miles, why smugly bash them over the head with chains, furlongs and rods, unless they’re into that sort of thing?
I’m Canadian of a certain age, so it turned out my textbooks were imperial up to Grade 3 and then changed over, along with the rest of the country, in the late seventies. As a result, I’m a happy hybrid, using whatever measurement suits the application at hand. I judge large distances and speeds in kilometers and kilometers per hour, becuase I’m usually measuring them on maps and using my car’s speedometer, marked in kilometers. I measure smaller distances, as in the width of a room, in feet and inches, becuase that’s what most of my measuring tapes use. Volume is in litres, because the products I buy are measured as such and I have no patience for ounces, pints and quarts anyway. The food I buy is measured by weight in grams or kilograms, but if I pick up a piece of non-edible equipment, I’m more likely to say “damn, this must weigh 70 pounds!” instead of 30 kilograms. As for the rare times I must consider areas large enough to be uncomfortable in square feet, hectares are just fine, becuase I can never remember what the hell an acre is, anyway.
I think the following is interesting about the metric system. The meter is defined as “The distance travelled by light in vacuum during a time interval of 1/299 792 458 of a second”.
The second is defined as “The duration of 9 192 631 770 periods of radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium-133 atom”.
And the kilogram is defined as “The mass of the international prototype kilogram” (I think this is the platinum-iridium deal they keep in France somewhere).
So:
(A) the kilogram definition seems a lot more arbitrary than the other two. I think a mass standard should be based on something like the mass of Carbon 12 atom.
(B) A lot of the weirdness in the definitions of meter and second are probably because of a desire to keep to the “standard” second that people had been using for a long time (i.e. 1/86400 of a day). But how did they ever know to set the second as 9192631770 perods of radiation, and not, say, 9192631780 periods.
No we don’t. We never used the Imperial system, which differs from the US system in almost every respect.
Arbitrariness is less important than exactness. If we can ever count the atoms in 12 grams of pure carbon-12 more accurately than we can weigh the Standard Kilogram in Paris, we’ll do that, but right now it’s impossible.
The original definition was 1/86400 of a day. Then it was, if I recall correctly, 1/31536000 of the tropical (i.e., not siderial) year 1900. It probably went through some more variations before reaching the current value. Essentially, every time that a measurement is found that is more generally reproducible and more exact than the current standard, the standard is likely to change.
Well, excuse ME, but the reason the word “imperial” was originally in quotes shows that I am aware that various definitions exist, though I didn’t feel compelled to list them. Any system (or language, or religion) that is old enough is going to have local variations.
Besides, if you want to get nitpicky, what do you mean by ‘almost every respect’ ? Are inches, feet, gallons and miles entirely different in England than in the U.S.? Maybe they only sound different because of that snooty accent.
“Imperial” in the sense I used it can casually refer to the system of familiar non-metric units including pounds, feet, and gallons without delving into local variations. If anything, that provides a stronger argument for going metric, since metric units are more rigidly and internationally defined.
As for the investment angle I was going for, it’s merely a restatement of part of a Cecil column (Whatever happened to adoption of the metric system in the U.S.?, 02-Jun-95) which I quote forthwith:
**
The point being that Americans can cling to non-metric measurements for as long as they want, and that there would be a cost to forcing the metric issue on the entire country if there is no compelling need to do so, though individuals who felt an advantage to going metric (i.e. Olympic athletes, auto mechanics) have already done so.
“But she’ll get 40 hectares on a single tank of kerosene.”
-Crazy Vaclaz
Virtually all the US and Imperial units are different. I’m amazed that you, a Canadian, don’t know that an Imperial Gallon is about 120% of a US Gallon.
The US Inch and the Imperial Inch were replaced by the International Inch in 1959, so they’re equal now, but before 1959, they were not.
Don’t say “Imperial” if you don’t mean it. The correct term for “the mess the UK and US used to have in common (but only approximately), which now only the US uses” is “English”.
The limiting factor with counting the atoms in a given mass would be the precision to which we know Avogadro’s number, which we know to about 0.59 parts per million. I would be surprised if anyone can measure the mass of the kilogram standard any more accurately than that. So really, the difficulty would be precisely measuring out 12 grams (or 1 kilo) of Carbon 12, as opposed to determining the number of atoms therein. No matter what the standard is, there is always the practical limitation of how well we can measure mass on a macroscopic scale.
This makes me wonder… what is the standard way to measure the mass of this standard? Considering that Newton’s gravitational constant (“big G”) is only known to 128ppm precision, any method of “weighing” the kilogram standard based on the effect of Earth’s gravity should be limited to this precision, right? Isn’t mass generally inferred from some measurement of a force, or a force balance? It’s not trivial to measure any force, or any acceleration due to a force, to great precision.
Anyway, the reason I think the kilo (or the gram) is inconvenient is because a gram-mole turns out to be 6.022e23 molecules. If we could chose, for example, 1 MU-mole = 10.000^24 molecules, and then our macroscopic mass unit could be the “MU” (roughly 1.66 kilos), it would be easier to do convert from mass to number of molecules in your head. In keeping with the whole factor-of-10 theme of the metric system.
What I was really trying to point out here is that there is a discrepancy in the precision of the measurements. According to the above, the original “second” was known to about 5 significant digits (assuming those zeroes in 1/31536000 aren’t all significant). Then, when the cesium atom standard was chosen, they defined that to 10 significant digits. My question is, how did they know what to define as the last 4 or 5 digits when the original standard that they were trying to match wasn’t known to that precision. I think they could have just as easily chosen 9 192 632 000 periods of radiation (with two of those three zeroes being significant), and matched the previous standard just as well as they do now.
It kind of reminds me of when some of my students submitted a design project and “estimated” the annual profit to be $35,267,891.05, based on 90,000 tons per year and 55 cents per pound of product, minus raw materials and capital.
Sigh. This is the kind of nitpicking that can only strangle discussions, since each participant has to sprinkle asterisks and footnotes throughout their statements. Not having been alive in 1959, I’m cheerfully prepared to ignore the standardization battles of that era, although I do remember reading, of all things, an Encyclopedia Brown mystery story in which the solution hinged on five quarts equalling a gallon in Canada (and presumably the UK and other “imperial” places, as well). I was suitably confused by this at the time and now I happily embrace litres, which at least aren’t subject to local interpretation.
Anyhoo, I’ll continue to use the phrase “imperial” to mean “non-metric” becuase it’s ultimately less confusing. The system that “now only the US uses” is called “English”?
Riiiight. So what do the English use? Consarn it, the next time an empire collapses, we really have to clean up these loose ends better.
The exact quantities involved were never relevant, anyway. I was discussing which system is useful for a given situation and the natural resistance to change it, once selected. If you don’t like it, then don’t buy any gasoline at my chain of “BryCo” filling stations.
Vacuum balance, with transposition from one pan to another and other checks. A balance is not dependent on local G.
The measurement people are very aware that use of a physical prototype is unsatisfactory, and they’d be very happy to replace it, but, so far, it hasn’t been practical.
Yes, and it would be even nicer to use a system based on Planck’s constant, the speed of light, the rest mass of an electron, the electron charge, and Boltzman’s constant. But it ain’t gonna happen.
They were meant to be significant. It’s just 3652460*60.
They obviously couldn’t carry the year 1900 around with them to calibrate with. The real standard was one or more high-precision clocks. Each new standard reproduces, as well as possible, the previous standard, warts and all. (Remember, the higher-precision technology will have been in place for a while, before being adopted as a standard.)
“English” is the correct term for “the whole foot/pound/gallon mess”. “US” is the correct term for the standard form of the English system that is still used in the USA. “Imperial” is the correct term for the now obsolete standard form of the English system that was developed in the Victorian era for use throughout the British Empire.
It is not “less confusing” to call all apes “gorillas”, it is not “less confusing” to call all Jews “Hassidic”, and it is damn well not “less confusing” to call all English measures “Imperial”. The US never used the Imperial system, which did not even exist at the time of the Revolution.
[QUOTE]
*Originally posted by John W. Kennedy *
**
Well, when the National Association for the Advancement of non-Metric Measurements or the Foot-Pound-Gallon Anti-Defamation League shows up at my door to demand an apology, I’ll consider it. For now, I’ll just keep using my generalizations, especially when they have no relevance to the larger subject. Does it really matter if an American and an Englishman disagree about the exact quantity of a “gallon”? The point was how comfortable they are in continuing to use a non-metric measurement, despite the changeover in most of the rest of the world.
If you want to keep using gallons, be my guest. I won’t even bug you on how many mols in each one.
I find that, in fact, finding a new definition for the kilogram is an official ongoing project of the BIPM (International Bureau of Weights and Measures).
Can’t make an obvious error and get past an engineer! Before I Quote the true answer, think about our Northern highways for a minute. Why would salt be of any use on icey roads if it only bought 12 degrees of margin? A lot of work and a lot of salt wasted while still at a balmy 18 degrees - NOT!
I remebered what some of the posts have mentioned - that zero degrees is the lowest ice/salt temperature. But here is a quote from a website called “Numericana.com”:
In 1714, when G.D. Fahrenheit devised the temperature scale now named after him, he meant 100° to be the normal temperature of the human body.
On the other hand, he (first) defined 0° as the lowest temperature he could achieve in the laboratory by using salt to melt ice. (Although it's, in fact, possible to go a few degrees lower by doing the same experiment under ideal conditions.) This same temperature was also then a record low for Danzig (in 1709).
These two points, however, were later judged to be far too imprecise a basis for a temperature scale. Instead, it was decided that the ice point would be exactly 32°F and the steam point 212°F.
In this redefined Fahrenheit scale, the normal temperature of the human body is around 98.6°F (which is exactly 37°C, by the way).
The latest precise definitions of both the Farhenheit and the Celsius scales no longer refer to the ice point and the steam point. Instead, both definitions refer to the Kelvin scale of thermodynamic temperature (itself defined by stating that 273.16 K is the temperature of the triple point of water): The temperature of 273.15 K (just 0.01 K below the triple point of water) is equal, by definition, to both 0°C and 32°F, whereas 373.15 K is equal to both 100°C and 212°F. Of course, the new definitions match the old ones, except when the utmost in precision is called for...
The gram was defined in an era where science was considered to be the best method available to do things – witness how the scientists tried to base the metre on the earth’s circumference.
The gram is defined as the mass of 1 cubic centimetre of water at its maximum density at 4°C.
Of course, the mass of 1 g is too small to be practical, so the base unit for mass was upgraded to the kilogram instead.
Instead of maintaining 1 cubic centimetre (or 1000 cc) of water at 4°C, scientists have now defined (in practice, though not in theory) that 1 kg is the mass of that piece of metal somewhere in France.
Bits of each system, essentially, although there is a great deal of force being applied to require everyone to use SI units for everything. It is, for example, now illegal to sell items measured in the traditional English units, such as pounds and pints. Except that it isn’t, sometimes, in some circumstances. Lots of fun to be had with that law.
In general usage, IME, most English people, along with most other British people, mostly use the traditional British units in most cases. Distances are in inches, feet or miles, weights are in pounds, though larger weights may well in in tonnes. Weights for a person, however, are in stones and pounds, where one stone is 14 pounds. A person’s height is in feet and inches, not just inches. Liquids are measured in (milli)litres, except for drinks such as beer, which are measured in pints. Petrol is often measured in gallons as well as in litres.
Essentially, there is a lot of pressure to bring Britain into line with what will become the United States of Europe. While a country can have their own standards of measurement, a state can’t. Most British people cheerfully ignore it and continue to use British units, but SI units will gradually become the norm, forced along by Europe. Personally, I’m familiar with either system. Younger people are more likely to use SI units, because that is what they will have been taught to use in schools. Anachronisms will no doubt survive for some while, such as beer being sold in pints.
Could someone please explain this sentence to me? The people defining the gram are scientists, who of course think science is the best method for doing things. And there is only one definition of the kilogram, based on the Standard Kilogram in Paris. The gram is not defined in terms of the density of water. It was once, but not currently.
Sorry, Chronos, but to make that make sense, I have to assume I know what he’s talking about and restate the point completely differently. And then I’m only sure that I think I know what I think he might have meant.
He seems to be talking about defining the units of measurement on physical properties. Thus the kilometer was defined based on the circumference of Earth. And therefore the origin of the gram was based on an amount of water at a specified state (temp and pressure). But it was an impractical measure, so they use the physical kilogram mass.
I think he just mangled the use of the word science.
