OK, I just want to set straight some facts, which I've seen wrong here more than once...

1. The imperial system is defined through the metric system, not the other way around. Although those two might seem interchangeable because they are linked to each other through the definition, this is not the case. Changing the length of a metre for example won't violate the definition, changing the length of a yard will, because the metre is the defining part, not the yard.

2. Yes, the speed of light varies under the influence of gravity, but only to an observer experiencing a different amount of gravitation. All measurements are assumed to be taken on an object (or whatever) in the SAME system of reference, therefore your measurements won't be affected by gravitation.

"1. The imperial system is defined through the metric system, not the other way around. Although those two might seem interchangeable because they are linked to each other through the definition, this is not the case. Changing the length of a metre for example won't violate the definition, changing the length of a yard will, because the metre is the defining part, not the yard."

Yes, we kmow this and it annoys us ()or at least me) greatly. Let us redefine imperial on it's own terms once again

Is this whole thing really only about pride ?

No. The defining of imperial by metric is purely for legislative purposes. For any practical purpose, it could just as easily be the other way around.

The problem arises when people mistake the legislative use of metric for defining imperial units as an indication that imperial cannot exist without metric.

I think the definition of the imperial system through SI is a little bit more than just for "legislative purposes".
Since there is no standard pound stored somewhere or a definition of the yard through physical constants, I think it's it's pretty fair to say that imperial is not an independent system on its own, rather a popular mapping of SI.

Ralf
P.S.: Strangely enough, no-one seems to have opposed the bespoken definition when it was made.

"The problem arises when people mistake the legislative use of metric for defining imperial units as an indication that imperial cannot exist without metric."

This is an arguement I have faced when debating with metricites before- I think it was in the fifties that we became defined against metric in the way we are, but prior to that we had standardised lengths and measures and so on. The redefinition as against metric, did not make our units less "changing" and more constant, especially seeing as the length of the yard is within the milimetre in length of the oldest surviving yardstick. There are *many* metric myths and misunderstandings, including many of "Suzie's"- perhaps we can eventually change this...

"P.S.: Strangely enough, no-one seems to have opposed the bespoken definition when it was made."

The situation was different. For one, it was done (or it was said it was done) in order to have an easier interchangability in the units of metric and imperial- you could "cross" them as it were.




[personal note: Ralf, are you an rpger- your way of speech seems *very* familiar to me]

If you explain to me what a "rpger" is ?

role playing gamer.

Nope, played exactly one game in my life. Didn't like it, never played again.
What part of my way of writing brings you to that conclusion ?

Ralf

Just your general tone and way of adressing a point is similar to someone on a rpg forum. Just a thought...




BACK TO THE TOPIC!!!

>BACK TO THE TOPIC!!!

Good idea.

>The situation was different. For one, it was done (or >it was said it was done) in order to have an easier >interchangability in the units of metric and imperial- you could "cross" them as it were.

Either way, when the definition was made, some original definition of the imperial system must have been abandoned, depriving imperial from its independence and making them "derived" units (like Newton, Joule etc.) of the SI units.

Ralf

Ralf: Firstly, the question of whether imperial or metric units are taken as the basis is what scientists call "arbitrary". It makes no difference. You can do it either way and get exactly the same result. In the product 2*3=6 it makes no difference which is the multiplier and which the multiplicand because 3*2=6 as well. The standard kilogram could just as easily be called a standard 2.2lb.

Secondly, the speed of light in vacuo does not depend upon the gravitational field. Length and time vary separately, but the speed of light is a constant.

It wouldn't have made sense to define metric through imperial, because all scientific work was done in SI and it was therefore perfectly sensible to place imperial on the strong shoulders of SI and not the other way around.

I'm perfectly aware about the "chicken-egg" quality of a definition in general, i.e. that you can interpret it the other way around, HOWEVER, SI units have a proper definition through physical constants, imperial does not.
I don't think you will ever find a document saying "the metre is defined as X yards", you only find "the yard is defined as X metres".

A definition is a "->" relation, not a "<->" relation.

Cheers,
Ralf

Ralf: It is quite false to claim that all scientific work was done in SI. A great deal, laying the core foundation of modern science, was done in imperial. Much of the rest was done in cgs units. Even today, much, if not most, scientific work uses units other than SI units. Astronomy, Cosmology and Relativity, to name but three branches of physics, use SI units to only a very limited extent.

It is also quite false to claim that "SI units have a proper definition through physical constants, imperial does not". The definitions are mathematically and physically equivalent. Conversion factors can with the greatest of ease be cancelled out to remove all mention of SI units. Conversions themselves are definitions. Definitions are logical equivalences that run in both directions. If they do not run in both directions they are not logical definitions but only partial descriptions.

"1 yard=0.9144 meter" means neither more nor less than "1 meter=(1/0.9144) yard".

>Ralf: It is quite false to claim that all scientific
> work was done in SI.A great deal, laying the core
> foundation of modern science, was done in imperial.
> Much of the rest was done in cgs units. Even today,
> much, if not most, scientific work uses units other
> than SI units.

I must say that in my years of studying and work as a scientist I haven't come across a scientific paper that states results in imperial measurements.
When you write a scientific paper, you want to maximize the number of people reading it, putting an obstacle in the way for not-US/UK scientists by stating your results in imperial would be very foolish and is thusly never done.
Stuff like in "Scientific American" often gets converted from metric to imperial for the broad public.

>It is also quite false to claim that "SI units have a >proper definition through physical constants, imperial >does not". The definitions are mathematically and >physically equivalent.

But they're not equal partners in the game, since the official documents state a relation between physical constants and SI measurements.

Let's assume you are right and I ask the question
"How long is 1 metre ?"
If I convert it to imperial by restating the SI<->imperial relation, I end up in a dead-end street since the definition of imperial refers me back to SI.

There is an official "SI->phys.constants" relation and an official "Imp.->SI" relation, however, there is no official (!) "Imp.->phys.constants" relation, you always have to go through the SI system.

Ergo : SI is the real thing, imperial is a popular interpretation of it.

Ralf

Ralf,
You are in an untenable position, and hopelessly, utterly wrong.

QUOTE: "It wouldn't have made sense to define metric through imperial, because all scientific work was done in SI and it was therefore perfectly sensible to place imperial on the strong shoulders of SI and not the other way around."

ANS: Not all work is science. Scientists used metric/SI to define distance because they prefer to work in metric, so it was a convenient arrangement. If GREENGROCERS had been in charge, they would have used imperial, as this is their preferred system for day-to-day use.

QUOTE: "[metric and imperial are] not equal partners in the game, since the official documents state a relation between physical constants and SI measurements."

ANS: Same issue, exactly. The people who drew up the official documents are individuals who chose the system that suited them. Other people might have drawn up the documents in another system. The key point is that the official documents just reflect the politics, culture, whims, etc of those who wrote them; the terms used are a contrivance and not definitive in any way.

Ralf: BWMA is of course entirely correct in pointing out that scientific usage is not the only legitimate basis for choice of units. But even in purely scientific terms you are grossly in error.

It is a historical fact that the foundations of modern science were laid long before modern metric systems were even invented (~1800), let alone SI (1960). Newton did not work in SI!

Even today a large proportion of scientific work is performed and published in units other than SI units. I have before me on my desk the definitive modern text on relativity theory (Misner, C.W., Thorne, K.S & Wheeler, J.A, "Gravitation", W.H.Freeman, San Fransisco, 1973). In all its 1789 action-packed pages there is not a single page that uses purely SI units, and only a few that use SI units at all; many pages use non-metric units like light years and parsecs, and a few even English units like nautical miles and pounds per square inch; mainly MTW uses geometricised (or geometrodynamic) units, or for conventional interpretations cgs.

Scientists use a wide variety of units and systems (many with technically incompatible definitions) as they find convenient. There are SI-fanatics who try to impose SI upon every scientific work, just as the metric fanatics try to impose metric on ordinary people; but they fail; scientists will not be bullied into giving up their favoured units.

One of the fundamental principles of science is its rejection of authority. In science there are no "official" bodies. That means that I am as entitled to define my units or systems of measurement as anyone else. If I choose to use the standards set by some international committee, that is purely for reasons of convenience. I will cease to use them whenever and wherever they become inconvenient.

Finally, the variant of the metric system being imposed upon us now in the name of European unity is not actually SI. The SI unit of volume is the cubic metre, not the litre, which is a secondary derived and "deprecated" unit; because of its incompatibility with the cgs litre (1000.028 cm**3) "it is recommended that the name 'litre' shall no longer be used to express volume measurments of high accuracy".

Hmm, a lot to respond on...

>You are in an untenable position, and hopelessly,
>utterly wrong

Ah, going down, are we ?

>Not all work is science. Scientists used metric/SI to
>define distance because they prefer to work in
>metric, so it was a convenient arrangement. If
>GREENGROCERS had been in charge, they would have used
>imperial, as this is their preferred system for day-
>to-day use.

If you had read the whole discussion you would have noticed that we were talking about WHY SI and imperial were defined the way they are. My point is that SI is the one that has the proper definition, imperial is a popular mapping of it (which is reflected in the definition of imperial).
If greengrocers were in charge of anything (apart from selling food), we would be dead by now.

>The key point is that the official documents just
>reflect the politics, culture, whims, etc of those
>who wrote them; the terms used are a contrivance and
>not definitive in any way

It might look like a national conspiracy to you (no wait, you actually believe it !), but imperial is defined through SI, basta.
I couldn't think of anything more definitive than the sentence "One yard is defined as 0.9144 metres", which CLEARLY states the hierachy.

>The SI unit of volume is the cubic metre, not the
>litre, which is a secondary derived and "deprecated"
>unit; because of its incompatibility with the cgs
>litre (1000.028 cm**3)

As you may have noticed, the cgs system was an intermediate system. NOBODY teaches you in school that a litre is 1000.028 cm^3, everybody knows it's 1 dm^3. Apart from that, "litre" is a derived unit, like the "gallon", only that "litre" has a nicer definition, not "3.78 dm^3".

> If I choose to use the standards set by some
>international committee, that is purely for reasons
>of convenience. I will cease to use them whenever and
>wherever they become inconvenient.

Good for you, but don't wonder if nobody listens to you when you choose to do so.

Let me emphasize once more, this discussion here was about the independence (or lack thereof) of the imperial system to the SI system. By now everyone sane should have noticed that the imperial system is no longer an independent system since its official definition through the SI system.

Ralf

"By now everyone sane should have noticed that the imperial system is no longer an independent system since its official definition through the SI system."

- I don't see how this makes metric a better system, which is, afterall, the whole point of all of these arguments (I would say "debates", but...)

QUOTE: "By now everyone sane should have noticed that the imperial system is no longer an independent system since its OFFICIAL definition through the SI system" [our emphasis].

Precisely; it is the official definition. But who defines "official"? If one individual out of a million rejects the official definition, then it cannot be a universal definition. Metric is used in legislation but that does not make it more valid, more accurate or more definitive. Metric is merely a preference of officialdom, a reflection of their value system.

For metric to be definitive, it must be universal. To be universal, there must be no dissenting voices. One dissenting voice in a million will stop it from being definitive or uniquely "scientific". Perhaps this is why metric is accompanied by compulsion.

Metric and imperial is not just about weights and measures; it is about the struggle between dictatorship and democracy.

Ralf: The cgs systems aren't "intermediate" systems. They have been in use far longer than SI and are still widely in use in scientific circles today. If nobody ever taught you that the cgs litre (the volume of 1000g of water at the temperature of maximum density) is not the same as 1dm**3 then so much the worse for your teachers.

Secondly, it is you who has proved yourself so contemptuous of derived units that you ludicrously imagine that defining imperial units in terms of the definitions used for metric units somehow makes them inferior. The litre is a derived unit. So are the gramme, the tonne, the millimetre, the centimetre, the decimetre, the kilometre, the hectare, etc., etc., all related to the basic SI units through conversion factors - which happen to be factors of ten, but so what? The Celsius scale is not the basic SI scale of temperature either. The km/h is a derived unit that isn't even metric - the SI unit is the m/s (personally I can think quite well in either m/s or mph, but not at all in km/h).

Once again, there are NO official systems in science - only systems that are used by greater or lesser numbers of scientists.

Three more important scientific or technical tomes from my library:
Hoerner, S.F, "Fluid-dynamic Drag", 1965. This is a particularly useful and admired compendium published by the author himself in exactly the form he wanted - and particularly relevant to this debate because the author is a German who did much of his work in Germany. The book uses British units throughout! Not a metre in sight! (The companion volume, "Fluid-dynamic Lift", is similar).
Marchaj, C.A., "Aero-hydrodynamics of Sailing", Granada, 1979. Well, well, well. This is also in British units throughout, with an occasional nod to metric in the Appendix.
Stinton, D., "The Design of the Aeroplane", Granada, 1983. Like to guess which units? Yup. Imperial - even to imperial rather than US gallons.
Personally, I'd probably have found all three easier to use had they used predominantly SI units; but the authors are well-respected scientists and engineers who chose to use imperial for their own good reasons. It is absurd to pretend that the only good scientific work is that done in SI.

PB said

>Ralf: It is quite false to claim that all scientific
> work was done in SI. A great deal, laying the core
> foundation of modern science, was done in imperial.
> Much of the rest was done in cgs units. Even today,
> much, if not most, scientific work uses units other
> than SI units.

Ralf said

>I must say that in my years of studying and work as a
>scientist I haven't come across a scientific paper...

It is news that Ralf is now claiming to be a "scientist"! On another board back in April he claimed
to have a "master's in EE" and to have read "quite a
few" scientific papers. There as well, his statements
concerning matters of fact undermined his pretentions
to authority.

When PB says
> much, if not most, scientific work uses units other
> than SI units.
this is a fact which you can verify for yourself very
quickly with a simple Google search. Just search with
keywords "Gaussian cgs", one of the popular non-SI
systems, and you get examples from Princeton, MIT,
Cornell, Australian National University Canberra, and
the NRL Plasma Formulary ("mini-Bible" of plasma
physics). Or go to Google groups sci.phys and search
Usenet with keywords like "cgs vs SI". Scientists on
Usenet are always squabbling and moaning about the
huge variety of non-SI which they cannot resist using
and often prefer to SI. They are trapped because SI
units really are awkward to use in many circumstances.

Ralf could well be a student at some regional German uni as his email <sl177me@uni-duisburg.de> suggests and possibly not currently enrolled in courses. He may be trying to impose on people because he thinks he's on a pro-metric crusade. He is bright (by my modest standards) but still half-educated. He doesn't know about the big role of non-SI in science, he won't learn, and he won't stop talking as long as you contradict him. The only thing to do is to go away and let him think he has won the exchange and vindicated the Fatherunits. Unless of course you find it fun to argue with him.

BTW PB made an elegant point about reciprocity of exact conversion ratios, but it got obscured in the Ralfian flood of half-baked repetition.

Note that I am not saying MIT, Princeton, Cornell, ANU-Canberra etc are good. I am saying that the Google evidence is that physics classes and research in those
places can use non-SI. Because the minute you look you
see a final exam, a course syllabus, source material for research etc. which is in non-SI units.
Those institutions
just happen to be the ones that come up. It might have been a German institution instead. Non-SI is widespread in science and the fact that Ralf doesn't seem to realize this makes everything else he says of dubious value.

>Ralf could well be a student at some regional German
>uni as his email <sl177me@uni-duisburg.de> suggests
>and possibly not currently enrolled in courses

Oh, I see, you're revealing the "truth" about Ralf...
"Daily Mail", anyone ?

>It is news that Ralf is now claiming to be
>a "scientist"! On another board back in April he claimed
>to have a "master's in EE" and to have read "quite a
>few" scientific papers.

You may not know that, but it is the usual course to first get you master's and then become a scientist...

Ralf

Oh, I forgot:

>The only thing to do is to go away and let him think
>he has won the exchange and vindicated the
>Fatherunits. Unless of course you find it fun to
>argue with him.

>BTW PB made an elegant point about reciprocity of
>exact conversion ratios

Which would mean that your idea about a good discussion board is that there's only one side and you keep padding yourselves on the back...

Taking this explosion of responses, combined with BP's initial response,

>Yes, we kmow this and it annoys us ()or at least me)
>greatly. Let us redefine imperial on it's own terms
>once again

I guess I hit it where it hurts.

Ralf

Some have criticised Ralf on this thread. Frankly compared to some of the metric fanatics on these styles of boards I think his posts are quite restrained.

Totally disagree with the "imperial being based on metric" arguement (ie why a=b is the same as b=a).

I thought they redefined the metre back in the mid 80's. Funny that - none of the roads I travelled on changed length, but the signs still said the same miles/yards!