Talk:Conversion of units/Archive 2009

Converters as an external link

I have created a collection of freely available, javascript implemented tools, including several converters, based on the data presented in this page. Would anybody have an objection if I added it as an external link? The link in question is: http://www.tangent.gr/tools_for_wiki/tools_en.php

Revipm (talk) February 13, 2009 —Preceding undated comment was added at 12:35, 13 February 2009 (UTC).

I object because it doesn't work. --Jc3s5h (talk) 23:13, 11 May 2009 (UTC)

Table ordering

Some tables seem to be ordered alphabetically, while others seem to be by size. Should this be standardized? BW95 (talk) 15:24, 17 August 2009 (UTC)

I would like to see them ordered alphabetically, for two reasons. First, the person looking up a unit is more likely to know how it is spelled than how big it is. Second, similar units with slighly different definitions (the various versions of BTU or calorie, for instance) will be grouped together without being interrupted by some unit with a different history that just happens to be about the same size. --Jc3s5h (talk) 16:01, 17 August 2009 (UTC)

Alphabetizing is done through the Mass section. BW95 (talk) 18:34, 17 August 2009 (UTC)

Agree, let's alphabetize as standard. It's NPOV as well as being obvious to the user. Physchim62 (talk) 18:48, 18 August 2009 (UTC)

Year, decade, century, millennium

I'm going to remove the "calendar year" entry since its length really depends on which calendar is used, and the Julian and Gregorian year lengths are specified in the table. Also going to simplify the decade, century, and millennium entries since repeating the Julian/Gregorian distinctions just clutters up the table. It may be nice from a definition standpoint to refer each of these back to the SI unit, but on a practical level, I really doubt anyone has a need to convert millennia to seconds. BW95 (talk) 05:37, 24 August 2009 (UTC)

Full and hollow months

I believe the terms full and hollow month are specialized terms used by those working with lunar calendars. The context for the definitions should be mentioned, and citations provided. --Jc3s5h (talk) 15:03, 24 August 2009 (UTC)

Other than Wikipedia's own month article, the best source I know of is from Mapping Time (E.G. Richards, Oxford University Press, 1998), p. 94:

Our knowledge of Greek calendars is all too fragmentary and often we must rely on classical authors, some writing much later. The following account must be viewed as being schematic and not necessarily historically accurate. An early Greek calendar attributed to Solon of Athens...specified a year of 12 months containing alternately 30 days (full months) and 29 days (deficient months) to give a total of 354 days.

I don't know if this would be considered sufficiently reliable as a source for definitions. Context-wise, the 30/29 pattern makes for an average month length that comes close to the ≈29.531 day synodic period and were used in successive refinements in fitting lunar cycles to solar years by ancient Greek astronomers, specifically the Metonic, Callippic, and Hipparchic cycles. BW95 (talk) 18:57, 24 August 2009 (UTC)

I have cited the proceedings of the Vatican conference held to commemorate the 400th anniversary of the Gregorian calendar. --Jc3s5h (talk) 19:45, 24 August 2009 (UTC)

Removing Olympiad (under Time)

It's currently defined as an interval of 4 years at 365 days each, which is incorrect. The ancient Olympic games

were held around the time of the first full moon following the summer solstice....as the games were tied to the lunar phase...they were spaced alternately by forty-nine or fifty months (because there were ninety-nine months in each octaeteris).

Duncan Steel, Marking Time, John Wiley & Sons, 2000, p. 46

The math doesn't work out to be a neat multiple of 365 days. A glance at recent schedules makes it clear that the modern games don't adhere to a strict 365-day multiple either. BW95 (talk) 23:31, 24 August 2009 (UTC)

Angular momentum

I'm going to rename this section to "action" and remove the lines for SI and CGS units, leaving only the atomic unit of action, for three reasons: 1. There is no SI unit for angular momentum in the SI brochure. 2. I can't find a standardized unit for it in my (admittedly old) physics and dynamics textbooks. 3. It would make sense for a unit-conversion article that contains angular momentum to include linear momentum as well, but this article doesn't. Given the lack of SI units, I think we should leave them both out of this article. BW95 (talk) 18:42, 25 August 2009 (UTC)

Just to be clear, you mean there is no special SI unit name for angular momentum, right? --Jc3s5h (talk) 18:46, 25 August 2009 (UTC)

What I mean is that the SI brochure doesn't even list momentum (angular or linear) as a category. J-s or kg-m/s would make sense for angular and linear momentum (respectively), but they're just not shown. The "relationship to SI units" column can still make sense for the atomic unit of action, though, since both Joules and seconds are SI units. BW95 (talk) 19:13, 25 August 2009 (UTC)

I agree with getting rid of J•s, because we have to be selective about providing conversion factors for compound units; the number of compound units is limitless. However, can you provide a citation for "atomic unit of action". The Atomic units article does not contain the word "action". --Jc3s5h (talk) 20:45, 25 August 2009 (UTC)

The value currently in the article agrees with the NIST's number from 1998 (http://physics.nist.gov/cuu/Document/nonsi_in_1998.pdf) but differs slightly from the (presumably more up-to-date) numbers in the SI brochure as well as from the NIST itself. Might be a good idea to update it. —Preceding unsigned comment added by BW95 (talk • contribs) 21:11, 25 August 2009 (UTC)

Done. --Jc3s5h (talk) 21:25, 25 August 2009 (UTC)

Magnetic field, amps/meter, Oersted

I'm going to rename this section to Magnetic Flux Density and remove the entry for amps/meter, leaving tesla (SI) and gauss (CGM) in the table. The CGPM Resolution 12 lists magnetic field strength (A/m) and magnetic flux density (tesla) as separate entities. Also, the SI brochure (section 4.1, table 9) notes the Oersted (not currently in the article), a unit of magnetic field dimensioned in A/m, as being unrationalized. I have no idea what this means, but if somebody does, then he or she can add a section to this article for Magnetic Field Strength to include A/m and/or Oersted. —Preceding unsigned comment added by BW95 (talk • contribs) 19:26, 26 August 2009 (UTC)

External links

I don't know who made the rule that "undiscussed links will be removed," but I think this'll be helpful: http://physics.nist.gov/Pubs/SP811/appenB9.html BW95 (talk) 19:41, 25 August 2009 (UTC)

Doesn't look anyone is objecting, so I'm adding it. BW95 (talk) 13:41, 29 August 2009 (UTC)

US legal (or FDA) cup

Should the US measure used for food labeling (called, at least unofficially, as either the food cup or FDA cup) be included under the Volume section? I believe it's defined as 240 mL. BW95 (talk) 15:26, 17 August 2009 (UTC)

Found a cite, so it's added. BW95 (talk) 16:32, 29 August 2009 (UTC)

Time section needs cleaning up?

Two entries under "Time" seem to be of dubious quality.

• Generation = 26 years. I don't see any support for that. A casual web search shows no consensus. Is there an official definition?
• Dog year. Um, really? I know it's used colloquially at the equivalence of 7 human years per dog year, but is that actually an official definition? Does it belong here? BW95 (talk) 20:51, 20 August 2009 (UTC)

You will have a hard time finding official definitions for many units of measure. Although trade associations and scientific societies can make suggestions, only nations can establish binding official definitions. Some (most?) have made the official definitons of SI mandatory in commerce, but the United States doesn't purport to even have an exhaustive list of customary units, so no one knows for sure all the units that might be used in the US. --Jc3s5h (talk) 21:17, 20 August 2009 (UTC)

Well, I'm going to remove them. A) Until someone can come up with a better-supported or consensus definition of generation, and B) Aging in dogs points out that there is no linear correlation between dog years and human years. BW95 (talk) 04:00, 24 August 2009 (UTC)

How about that, just today Slate's Explainer column goes into detail about dog years (in short, 7:1 is not an immutable ratio): http://www.slate.com/id/2227076/ BW95 (talk) 01:22, 3 September 2009 (UTC)

Information entropy

This section seems strange to me. I'm leaving it alone for now since I'm no expert on the subject, but someone more knowledgeable needs to taka a look at it. I am aware that there are parallels between thermodynamic entropy and information entropy, but to actually take units from it (joules per kelvin)? How does that even work? BW95 (talk) 04:07, 27 August 2009 (UTC)

I would suggest that you research the subject before making any comments on it, I'd suggest reading Shannon's paper on the subject. That provides a good foundation, there are numerous other papers on the subject. —Preceding unsigned comment added by 130.85.236.149 (talk) 19:10, 24 November 2009 (UTC)

-Joe

I wasn't making comments, I was asking questions. If you're knowledgeable about this subject, you're welcome to illuminate the section by providing background information or sources for it. BW95 (talk) 00:03, 25 November 2009 (UTC)