A most elegant solution, good sir. I salute you! -- Ezra
----- Original Message ----- From: "simon meng" <[email protected]> To: "U.S. Metric Association" <[email protected]> Sent: Wednesday, August 12, 2009 9:08:23 AM GMT -08:00 US/Canada Pacific Subject: [USMA:45590] RE: defining the kilogram from the joule Ezra, I would like that too. But what name would we give it? Of course if it does become a derived unit we can name it after a person, possibly someone who has been involved in the research related to the watt balance project. But to be effective and acceptable, the name would have to be simple, and probably one syllable. Wait! I have the perfect name. The meng (symbol: M). It is short and simple and rolls off of your tongue with ease. While we are at it we can get rid of all those dreadful tons, tonnes, etc and replace them with the kilomeng (kM). How many votes can we count for the new name of the kilogram to be the meng? Simon From: [email protected] Sent: Wednesday, 2009-08-12 00:14 To: U.S. Metric Association Cc: U.S. Metric Association Subject: [USMA:45586] RE: defining the kilogram from the joule My fantasy is that, with the kilogram relegated to the status of a derived unit, CGPM might take advantage of the change to provide a new name for "kilogram" that has no prefix. Pleasant dreams, y'all! :-) Ezra ----- Original Message ----- From: "simon meng" < [email protected] > To: "U.S. Metric Association" < [email protected] > Sent: Tuesday, August 11, 2009 8:16:05 PM GMT -08:00 US/Canada Pacific Subject: [USMA:45584] RE: defining the kilogram from the joule Thanks Jim, I wasn't aware this topic was already discussed in a USMA publication. Everything I learned and thus deduced came from reading the associated articles in Wikipedia. It would be logical, even if the CGPM doesn't see it that way, to remove the ampere as a base unit and replace it with the coulomb. The same would hold true for making the kilogram a derived unit. It would be interesting though to see how they would word the new definitions for the ampere and the kilogram if they do indeed keep them as base units. Rearranging some of the units I wouldn't view as a sweeping change. Even you yourself noted that whatever they do to improve the realization of the units will have no effect on the public. As long as ma and pa shopper can ask for 500 g of salami and get 500 g, to them it would make no difference if the kilogram was a base unit or derived unit. I have to say though that keeping the details under wraps is quite intriguing and gives the whole issue the aura of a suspense novel. Waiting for the details to be released will be like a little kid waiting for Christmas day to see what Santa has brought him. I'm wondering though if someone else who was privy to advanced information did let the cat out of the bag, so to speak, by providing some of the information I viewed and brought here from Wikipedia. The one issue about the watt balance method that was missing from the English test was the improvement of the uncertainty in the realization of the kilogram is that it would reduce the uncertainty from 5 x 10**-8 to <1 x 10 **-8. In other words the uncertainty would be reduced from 50 μg to <10 μg. This overlooked fact was mentioned in the German article (watt-waage) unter the heading hintergrund: Die SI-Basiseinheit für die Masse ist das Kilogramm. Das Kilogramm wird seit 1899 über die Masse des Urkilogramms definiert. Dies ist ein, in Paris aufbewahrter, Zylinder aus einer Platin-Iridium-Legierung. Dadurch ist das Kilogramm die einzige Basiseinheit, die nicht mit Hilfe einer definierten Messung in einem Labor bestimmt werden kann. Des Weiteren würden Änderungen der Masse des Urkilogramms, beispielsweise durch falsche Handhabung, bewirken, dass die Masse keine konstante, sondern eine veränderliche Größe wäre. Bei einigen Messungen in der Vergangenheit wurde festgestellt, dass die Massen der Duplikate des Urkilogramms im Vergleich zum Urkilogramm um etwa 50 µg zugenommen haben.[1] Seit Jahren schon bemühen sich Physiker deshalb, eine im Labor reproduzierbare Definition für das Kilogramm aufzustellen. Die dabei angestrebte Genauigkeit liegt bei < 10-8, das heißt besser als 10 µg. It is interesting that the errors discovered between the prototype kilogram and its copies (5 x 10**-8) is the same level of relative uncertainty in the realization of Planck's constant. Hmmm! Simon -------------------------------------------------- From: "James R. Frysinger" <[email protected]> Sent: Tuesday, 2009-08-11 17:37 To: "U.S. Metric Association" <[email protected]> Subject: [USMA:45583] RE: defining the kilogram from the joule > > I think you have the essentials put fairly clearly here, Simon, at least > in concept form. Your description follows the general thread reported in > the Metric Today articles published a year or two ago. But I think it's > too early to say that there will be a change in the selection of the seven > base units. And I doubt that those will change. > > The members of IEEE SCC 14 and I been made privy, in the role of technical > consultants, to a few options on this proposed restructuring that are > being considered. Those proposals differ in many ways. So it's too early > to say how the accepted implementation will be carried out in terms of the > writing of the SI definitions. > > Keep in mind that the CGPM and CIPM are reluctant to make sweeping changes > to the SI, at least on the face of matters. I doubt that they want to > "yank the public around" any more than is deemed necessary. They are more > aggressive in adopting new realizations and so forth since technical users > can keep up with such changes. > > I have heard that some recent work has been done on this SI structure > issue but I cannot provide any of the details to you. It is still a work > in progress and not ready for prime time, I am told. Perhaps we will know > more as early as late this Fall but even that may be optimistic. As soon > as I can, I will publish information via Metric Today on any expected > changes to the SI. > > Personally, I think that -- regardless of whatever proposed change is > accepted -- we will NOT experience any change in the SI as used in normal > marketplace, business, or even applied technical areas. That would be > entirely too disruptive. The play will appear the same to the public, > though the backstage technicalities used by the stagehands may change. I > suspect it will be taken as a sign of success that very few of those 96 % > of the folks in the world who are metricated will realize that any change > has been made. > > Consider the Mendenhall Order of 1893. The non-metric artifacts for U.S. > customary weights and measures were removed from their thrones and metric > definitions were substituted -- but the American public was oblivious to > that. Anticipate that this impending change to the SI, if adopted, > likewise will cause very few ripples in our quotidian lives. > > Jim > > [email protected] wrote: >> Thanks Jim for the heads-up! It seems though that there are going to be >> some major changes to SI come the 24-th CGPM in 2011. The ampere may be >> removed from being a base unit and replaced by the coulomb, where the >> coulomb will be defined as /exactly 6.241 509 629 152 65 × 10^18 >> elementary charges. /The ampere will then be a derived unit from the >> coulomb and the second. Since the coulomb and the second will then be >> accurately defined, so will be the ampere. >> The watt balance method would not define the kilogram directly. It >> would accurately relate mechanical power (watts) to electrical power >> (watts). Electrical the power equals voltage times current. Mechanical >> power equals force times velocity. In other words EI = FV The unit of >> force are the newton, the units of velocity are the meter per second, the >> unit of voltage is the volt and the unit of current is the ampere. >> This relationship allows for the use of the already accurately defined >> units of ampere (via the coulomb and the second), second and metre. The >> newton or the volt would need to be independently defined. The volt can >> be defined via the Josephson junction >> <http://en.wikipedia.org/wiki/Josephson_junction>, or the newton can be >> defined via the inverse of the definition presently used to define the >> ampere. That is Ampère's force law applied in reverse. >> Which ever one becomes the easiest to realize would most likely become >> the base unit. >> The kilogram then would have to lose its status as a base unit and >> become a derived unit. It would be derived from the newton, the meter >> and the second. Since F = ma, it stands to reason that m=F/a and thus 1 >> kg would be defined as 1 N s**2/m**2. The result is that both the ampere >> and the kilogram will not and can not remain as base units. The coulomb >> will replace the ampere and either the volt or the newton will have >> replace the kilogram. >> I find this all very exciting. Simon >> PS. From the Wikipedia article on the ampere: >> http://en.wikipedia.org/wiki/Ampere >> Realisation >> >> The ampere is most accurately realized using a watt balance >> <http://en.wikipedia.org/wiki/Watt_balance>, but is in practice >> maintained via Ohm's Law <http://en.wikipedia.org/wiki/Ohm%27s_Law> from >> the units of electromotive force >> <http://en.wikipedia.org/wiki/Electromotive_force> and resistance >> <http://en.wikipedia.org/wiki/Electrical_resistance>, the volt >> <http://en.wikipedia.org/wiki/Volt> and the ohm >> <http://en.wikipedia.org/wiki/Ohm>, since the latter two can be tied to >> physical phenomena that are relatively easy to reproduce, the Josephson >> junction <http://en.wikipedia.org/wiki/Josephson_junction> and the >> quantum Hall effect <http://en.wikipedia.org/wiki/Quantum_Hall_effect>, >> respectively.^[10] <http://en.wikipedia.org/wiki/Ampere#cite_note-9> >> >> At present, techniques to establish the realization of an ampere have a >> relative uncertainty of approximately a few parts in 10^7 , and involve >> realizations of the watt, the ohm and the volt.^[11] >> <http://en.wikipedia.org/wiki/Ampere#cite_note-SI_brochre-10> >> >> >> [edit >> >> <http://en.wikipedia.org/w/index.php?title=Ampere&action=edit§ion=4>] >> Proposed future definition >> >> Rather than a definition in terms of the force between two >> current-carrying wires, it has been proposed to define the ampere in >> terms of the rate of flow of elementary charges.^[12] >> <http://en.wikipedia.org/wiki/Ampere#cite_note-11> Since a coulomb >> <http://en.wikipedia.org/wiki/Coulomb> is approximately equal to >> 6.24150948×10^18 elementary charges >> <http://en.wikipedia.org/wiki/Elementary_charge>, one ampere is >> approximately equivalent to 6.24150948×10^18 elementary charges, such as >> electrons <http://en.wikipedia.org/wiki/Electron>, moving past a boundary >> in one second. The proposed change would define 1 A as being the current >> in the direction of flow of a particular number of elementary charges per >> second. In 2005, the International Committee for Weights and Measures >> <http://en.wikipedia.org/wiki/International_Committee_for_Weights_and_Measures> >> >> (CIPM) agreed to study the proposed change, and, depending on the outcome >> of experiments over the next few years, to formally propose the change at >> the 24th General Conference on Weights and Measures >> <http://en.wikipedia.org/wiki/General_Conference_on_Weights_and_Measures> >> (CGPM) in 2011.^[13] <http://en.wikipedia.org/wiki/Ampere#cite_note-12> >> >> >> -------------------------------------------------- >> From: "James R. Frysinger" <[email protected]> >> Sent: Tuesday, 2009-08-11 10:23 >> To: "U.S. Metric Association" <[email protected]> >> Subject: [USMA:45581] RE: defining the kilogram from the joule >> >> > >> > Yes, folks have been working on a possible restructuring the >> definitions >> > that the SI's base units are based on. >> > >> > At the annual meeting of the IEEE Standards Coordinating Committee 14 >> we >> > reviewed and commented on one such proposal. The matter is rather >> > complex and I expect to submit an article to Metric Today in the near >> > future on what is being planned. >> > >> > No doubt, the kilogram artifact currently residing in France will be >> > replaced as a standard. Previous issues of Metric Today have discussed >> > two main possible means of doing this -- a definition based on >> > Avogadro's number and a definition based on Planck's constant. >> Possible >> > realizations for those two methods are, respectively, "counting" the >> > atoms in a sphere of Si and weighing a mass on a Watt balance. One of >> > those two likely will be the "winner", once the dust has settled. >> > >> > As soon as I obtain the updates I have requested on this topic, I will >> > submit an article to Metric Today and, if it is accepted, I will alert >> > you via this forum. It would be premature to say much more at this >> time >> > since what I last saw and discussed may have changed considerably. >> > >> > I do urge those who take part in this forum to consider becoming USMA >> > members if they have not already done so. This of course provides you >> > with a subscription to Metric Today. >> > >> > Jim Frysinger >> > Chair, IEEE SCC 14 >> > Vice Chair, IEEE/ASTM Joint Committee for Maintaining SI 10 >> > >> > Bill Potts wrote: >> >> Simon: >> >> >> There is work afoot to dissociate the kilogram from an artifact. I >> have >> >> some information on that, but I'm not sure it's available for public >> >> distribution yet. >> >> >> However, Jim Frysinger can probably tell you what the approach is >> >> without having to look it up. >> >> >> Bill >> >> ------------------------------------------------------------------------ >> >> Bill Potts >> >> WFP Consulting <http://wfpconsulting.com/> >> >> Roseville, CA >> >> http://metric1.org <http://metric1.org/> [SI Navigator] >> >> >> >> ------------------------------------------------------------------------ >> >> *From:* [email protected] >> [mailto:[email protected]] >> >> *On Behalf Of *[email protected] >> >> *Sent:* Monday, August 10, 2009 20:31 >> >> *To:* U.S. Metric Association >> >> *Subject:* [USMA:45578] defining the kilogram from the joule >> >> >> >> Why is the kilogram a base unit in SI instead of the joule? The >> >> kilogram is the only base unit still defined from an artifact. >> >> Since the artifact can change with time and the kilogram has been >> >> know to do so, wouldn't it be better if a different unit were to >> >> replace the kilogram as a base unit? >> >> >> Energy is the most fundamental substance in nature. >> Energy has >> >> always existed, even before the universe was created and will >> exist >> >> long after the universe is gone. Energy is universal. Wouldn't >> it >> >> be simpler to define one joule of energy from basic principles in >> >> physics and define the kilogram from the joule in the >> relationship >> >> that 1 kg = 1 J s**2/m**2? >> >> >> Or, the kilogram can be defined from the newton, the meter >> and the >> >> second, which are already accurately defined. >> >> >> The ampere also should not be a base unit, the coulomb >> should be. >> Since the ampere is defined from the newton and the >> newton is >> >> defined from the kilogram, then the practical realization of the >> >> ampere is affected when the kilogram changes. >> >> >> From the Wikipedia article on the coulomb: >> >> >> /In principle, the coulomb could be defined in terms of >> the charge >> >> of an //electron/ <http://en.wikipedia.org/wiki/Electron>/ or >> >> //elementary charge/ >> >> <http://en.wikipedia.org/wiki/Elementary_charge>/. Since the >> values >> >> of the //Josephson/ >> >> <http://en.wikipedia.org/wiki/Josephson_constant>/ (CIPM (1988) >> >> Recommendation 1, PV 56; 19) and //von Klitzing/ >> >> <http://en.wikipedia.org/wiki/Von_Klitzing_constant>/ (CIPM >> (1988), >> >> Recommendation 2, PV 56; 20) constants have been given >> conventional >> >> values (K_J ≡ 4.835 979 × 10^14 Hz/V and R_K ≡ 2.581 280 7 × 10^4 >> >> Ω), it is possible to combine these values to form an alternative >> >> (not yet official) definition of the coulomb. A coulomb is then >> >> equal to exactly 6.241 509 629 152 65 × 10^18 elementary charges. >> >> Combined with the present definition of the //ampere/ >> >> <http://en.wikipedia.org/wiki/Ampere>/, this proposed definition >> >> would make the //kilogram/ >> <http://en.wikipedia.org/wiki/Kilogram>/ >> >> a derived unit./ >> >> // >> >> >> The ampere can then become a derived unit (1 A = 1 C/s) >> that is very >> >> accurately defined since the coulomb and the second are >> accurately >> >> defined. The newton would be defined as: >> >> 1 N = 1 J/m.s; if the joule is base unit defined from some >> principle >> >> of physics. The kilogram would then be defined from the newton >> as 1 >> >> kg = 1 N s**2/m**2. Otherwise, the newton would have to be a >> base >> >> unit and defined from the same rule that defines the ampere, but >> in >> >> reverse. >> >> >> Either way, this would eliminate the kilogram being tied >> to an artifact. >> >> >> Simon >> >> >> > >> > -- >> > James R. Frysinger >> > 632 Stony Point Mountain Road >> > Doyle, TN 38559-3030 >> > >> > (C) 931.212.0267 >> > (H) 931.657.3107 >> > (F) 931.657.3108 >> > >> > > > -- > James R. Frysinger > 632 Stony Point Mountain Road > Doyle, TN 38559-3030 > > (C) 931.212.0267 > (H) 931.657.3107 > (F) 931.657.3108 > >
