Now I’m puzzled. The older definition of a meter in terms of so many wavelengths of a particular kind of light seems to require the ability to observe waves, but doesn’t seem to require an accurate clock. However, according to the column http://www.straightdope.com/mailbag/mmetric.html the meter (or metre) is currently defined to be “the length of the path traveled by light in vacuum during a time interval of 1/299 792 458 of a second.” This seems to define only the ratio of the length of a meter to the duration of one second of time, and thus defines the meter only relative to the definition of a second. If I had a slow clock I would get a longer meter, with no one able to tell me I’m off, according to this definition. How do I know if I have an accurate clock (without relying on a length measure)? Perhaps the older standard implicitly presumes an accurate clock too, but if so, it isn’t obvious how. Maybe it’s conceptually impossible to define a meter independently of the definition of time measures. Perhaps the resolution lies in a deeper understanding of relativity or some such thing. Or maybe there is a definition of “one second” that avoids some kind of circularity in the definition of a meter. Can anyone resolve this for someone like me who lives in a Newtonian frame of mind?
That’s it. The second is defined independently of the meter.
Here is the current SI definition of a second.
A small comment – the SI does not precisely replace the Metric System. The Metric System is used by grocers and filling stations and fishermen everywhere but the USA. The SI is used for formal work by scientists everywyere. They have many things in common (like the definition of the meter), but some things are different. For example, the Metric unit of volume is the liter. The SI unit of volume is the cubic meter.
And “meter” is a perfectly good spelling in English, and the normal spelling in US English. “Metre” is the only correct spelling in French, but that’s not the same thing as being the only correct spelling in every language in the world.
Everywhere? I disagree. I’d say it depends on the scientist. While physicians will usually talk in terms of cc’s, the basic biomedical sciences describe liquid volumes in liters, milliliters and microliters. And in chemistry, a one molar solution isn’t defined as one mole of solute per cubic decimeter of solvent. Not to say that cubic meters aren’t used: I think sciences that deal with much larger volumes of matter tend to use the cubic meter exclusively. For example, I think the volume of water in the earth’s oceans is always expressed as cubic meters. I just think that delineating metric vs. SI by saying one is used for formal scientific work is inaccurate.
As long we’re being precise about measurement, we might as well be about spelling, too. 
Is “meter” acceptable? Absolutely.
Is “meter” correct? Technically, no. At least the way I’m interpreting what I’ve resaerched.
Clearly, other spellings are acceptable, but the official documents published by the BIPM that I’ve seen use the “metre” spelling, even after translation into english. If official documents by the people who make the rules refer to the unit as a “metre” I consider that to be the technically correct international spelling. Additionally, Encarta tells me that most English speaking countries spell it “metre”. Any non-yank anglophones care to confirm/dispute?
To add to the spelling debate:
The official German version of meter is meter. No “metre” anywhere.
I know, Prussian linguistic imperialism most probably.
one thing keeps me puzzled. What is the exact origin of the foot?
Aw crap, looking back I see where some of the confusion lies.
My statement “the correct, official, internationally-approved spelling is metre, not meter.” wasn’t meant to suggest that every language spells their word “metre”, rather that the official international English spelling is metre. That was the implication, seeing as how English was the language I wrote the article in. Anyway, it wasn’t completely clear. I’m sure other languages have various spellings.
Anyway, “meter” is like “aluminum”, IMO. Both spellings are acceptable, but internationally (among English speakers) neither spelling is technically correct. And like meter, other languages have spellings for that element that differ quite a bit from the official english spelling.
Anyway, Doc, you foot question was answered by my colleague Dogster here. And here.
[Edited by Alphagene on 03-14-2001 at 12:31 PM]
Not to change the subject, but isn’t anyone else bothered by the fact that conversion between that meters and feet is not trivial? Does a meter really have to be 3.280839895013123 feet? From what I understand, during the Revolution the French wanted to do away with any semblance of the old ways. They also insisted the standard not be arbitrary, and should not be based on an artifact. Well, it does not take a genius to realize that 1/10,000,000 of the distance between the equator and the North Pole is totally arbitrary (it is just a nice, round arbitrary number). Furthermore, accurately measuring that distance is terribly difficult, so you are going to end up relying on an artifact anyway. (In fact, one could argue that the Earth itself is an artifact.) Had they chosen a fairly similar and equally arbitrary standard for length, say 1 meter = 1/10,936,132 of the distance between the equator and the North Pole, 1 meter would be very, very close to 3 feet, and conversions between the two systems would be greatly eased.
Simply put, ease of conversion wasn’t a high priority for the FAS. Why not? Because if you’re trying to create a meter so it is easily convered to feet then you’re not really creating a brand new system. You’re basing it on the old system. The French wanted a new system created from the ground up. The fact that conversion is currently an annoyance for citizens of a country who haven’t embraced metric really doesn’t suggest a flawed system.
I’m not sure what you mean by this. I said in my article that the metric system aimed to be based on constant values that came from nature. But there’s nothing suggesting these values shouldn’t be arbitrary. Ultimately, I would think, the base units would have to be arbitrary. In fact, desginating anything as a base unit is by definition arbitrary, no?
parkerea, guess that depends on what you mean by “based on artifact”. True, any measuring system will depend on the precision and accuracy of your base. That, in it self, is not considered “artifact” from the standpoint of use above. They wanted something that could be independently determined by anyone. Though somehow to me making a titanium rod and calling that the standard seems to violate that principle.
Though the whole system is arbitrary by some standpoint. Look at the second - why did they pick the cesium 133 atom? Why did they pick 9 192 631 770 periods? Simply to match the previous measurements.
As for the 1/10,000,000 of the distance, they wanted a decimal based system and they wanted nice round numbers. That was kinda the point of their new system. Though if they had known then what we know now, wouldn’t it have been better to make a meter 1/300,000,000 of the distance light travels in a year? 
Back to that pesky old spelling thing…
(BTW - I appologize if going back to messages is a faux pas - I’ve never posted here before…)
Anyhow, up here in Canada, where we have embraced the metric system with all the fervour of a drunk urinating in the street, “metre” is most definitely the ONLY spelling that we can get away with when speaking about the unit of measurement.
Just the same as litre and centre. (Although I have no justification for centre.)
Meter is used, as previously mentioned, to refer to things like a parking meter, or an odometer.
However, we in Canada appreciate the loosness with which those south of the border employ the English language, including such charming colloquialisms as “fishes” (the plural of fish, incedentally, is “fish”) if only for the novelty.
Anyhow, back to the programme…
Al. 
Says who? The US has more people than all the other English speaking countries put together. Who has the right to tell us how to spell our words? If people are going to use the French spelling, they should use the French pronunciation, too (meh-tray, not mee-tehr). The correct spelling for “mee-tehr” is “meter”. That’s just common sense.
alice_in_wonderland:
Anyone that is annoyed by you going back to something discussed only a few messages ago deserves to be annoyed. And don’t get me started on “centre” (or “kihl-lahm-eter”, for that matter). (BTW, the plural of “fish”, when used to refer to a species of fish, is “fishes”; e.g. “This lake is home to many fishes, such as carp and trout”.)
Just a note about the German spelling. They spell it meter to match the pronunciation (more or less) of other languages. If they spelled it metre, it would have a distinctly different pronunciation in German.
French words that are adopted into English and that end in “-re” are spelled “-re” in the UK and “-er” in the US. Like “theatre”/“theater”. Naturally, the French, translating into English, would use the UK spelling. But “meter” is the norm in the USA, as witness the NIST website.
The liter is specifically described as a non-SI unit that may be used with the SI by those who insist on it, but which really shouldn’t be.
By the way, both “cc” and “ml” are deprecated in favor of “cm[sup]3[/sup]”.
On another point, the French never bloody used the foot in the first place. That’s an English measurement – which, by the way, was not the same in the US and the UK until 1959, when a compromise value was reached. The closest French measurement was the pied, equal to .3248m, or about 1.066 feet.
Yes, but you can understand why the French would like that number
“…the gram is no longer considered a unit of weight but a unit of mass.”
Anyone who thinks the gram is no longer used as a measurement of weight should try telling that to both my butcher and cocaine dealer.
Ryan, you’re getting wound up over nothing. I’m still not sure why you’re annoyed at alice, exactly…
IUPAC. The people in charge of designating the names of the elements.
Again, the American spelling is accepted but not official. The people who are officially in charge of assigning names to things get to decide what the correct spelling is. If 250 million plus citizens of the USofA decide to spell things a different way, then it will probably become acceptable, but it still won’t be technically correct. Sheesh, it ain’t a value judgement against the Land of the Free, Ryan, it’s just a statement of historical and scientific fact. You personally can decide to pronounce it “aluminum”, “aluminium” or “Abe Vigoda” for all I care. But the official IUPAC name for element #13 is aluminium. Sorry.
So you’re saying that use of the liter as a unit of volume is acceptable, but not technically correct. Fine. Then why is it so hard to believe an identical line of thought with regards to spelling? Namely that use of the “meter” spelling is also acceptable, but not technically correct.
OK, I appreciate the humor, but damnit I might as well say it yet again, just to be consistent. Acceptable use differs from correct use.
Your example, paek, is precisely why this distinction was made in 1901. The general populace frequently uses the gram as a measurement of weight. Scientists, however, need to distinguish between mass and weight. So despite what Sal down at Pathmark tells ya, grams are technically a unit of mass.
Imagine that - only one posting, and already someone is annoyed with me.
Ryan, I was in no way implying that people in the US should spell metre, metre, and more than I think you should spell colour, colour, or humour, humour. Someone asked for the opinion of a non-Yank anglophone, and I fit the bill, so I let fly with how things are done up here.
Anyhow, I’m sure any spelling you choose will be positively delightful to all those reading it, provided they’re from the States. Those from Canada, will automatically (albit in their heads) change the spellings where appropriate, to that which we are more comfortable with.
And incidentally, were I phrasing your final sentence, I would have put it: “This lake is home to many species of fish, including Sevrums and Puffers.” However, that could just be because I like to be a pain in the ass…
Al.
This spelling discussion is getting a bit silly, isn’t it?
I think Alphagene has made his point that the US is technically incorrect, but since when has that stopped them? And why should it? US English is a different language to ‘British’ English, as Microsoft love to call it.
Ryan’s assertion that the US has more English speakers than anyone else is probably bogus. Ignoring the fact that a large number of US citizens don’t have English as a first language, I think if you add the populations of the UK, Ireland, Australia, Canada, South Africa, Zimbabwe, other English speaking African nations, New Zealand, Pacific Island nations (okay, not really significant in sheer number terms…) you might find that we outnumber you guys.
Is it so hard for the US to cope with the fact that there is an international community out here that doesn’t always do things your way?
And another thing - the French pronunciation is not ‘mee-tray’, the ‘e’ does not have an acute accent. And since when has the pronunciation of English had anything to so with it’s spelling? Tough, though, through, threw, throw?
No, it’s Meter.