Talk:Impedance of free space

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[edit] Merge?

I'd guess that impedance of free space is a far commoner term than vacuum impedance, and that the latter is in turn far commoner than references to the band Impedance of Free Space. Google seems to confirm this with factors of 41 and 16 respectively.

Search term Google hits
"impedance of free space" 37,800
"vacuum impedance" 912
"impedance of free space" (IDM OR electronica) 57

I must concede that I've probalby missed some references to the band - I don't know mmuch about them, other than they've got a good name. Anyway, I'd like to move/rename vacuum impedance -> impedance of free space, and then add a hatnote like the one on this page: Kepone, linking to Impedance of Free Space. --catslash 17:03, 2 January 2007 (UTC)

I agree with that Alessio Damato 16:57, 13 February 2007 (UTC)

[edit] Requested move

The following discussion is an archived discussion of the proposal. Please do not modify it. Subsequent comments should be made in a new section on the talk page. No further edits should be made to this section.

The result of the proposal was PAGE MOVED per discussion above. -GTBacchus(talk) 05:08, 20 March 2007 (UTC)

Vacuum impedance → Impedance of free space – This is a purely procedural nomination. See comments in section above. I have no opinion. ···日本穣? · Talk to Nihonjoe 00:23, 14 March 2007 (UTC)

[edit] Survey

Add "# Support" or "# Oppose" on a new line in the appropriate section followed by a brief explanation, then sign your opinion using ~~~~. Please remember that this survey is not a vote, and please provide an explanation for your recommendation.

[edit] Survey - in support of the move

  • Support linas 00:39, 16 March 2007 (UTC)
  • Support (see #Merge?) --catslash 15:18, 16 March 2007 (UTC)

[edit] Survey - in opposition to the move

[edit] Discussion

Add any additional comments below.

The above discussion is preserved as an archive of the debate. Please do not modify it. Subsequent comments should be made in a new section on this talk page. No further edits should be made to this section.

[edit] Recent (Feb 2008) edits

Hi Brews ohare, I'm going to take issue with some of your recent edits - I'll try to give good reasons in each case. Do you by any chance have some connection with the NIST? --catslash (talk) 00:18, 24 February 2008 (UTC)

  • I've restored the 'Exact value' section. I think it's relevant that this constant has an exact value by definition, and is not subject to experimental error. Also the value is not obtained from the NIST, it's obtained by multiplication. --catslash (talk) 00:51, 24 February 2008 (UTC)
  • Is it necessary to give values when mentioning ε0, μ0 and c? It's clearer when it's less cluttered I think. --catslash (talk) 02:19, 24 February 2008 (UTC)
No connection. However, they and BIPM have the best web sites for finding things.
No problem with your edits: I did change a few minor things. Brews ohare (talk) 05:54, 24 February 2008 (UTC)
  • Define/Choose... The constants Z0, ε0 etc. are defined as constants of proportionality between various physical quantities (force, current, distance etc.). These quantities have to be measured in various units (A, m etc.) which themselves need to be defined. A cunning scheme for defining these units is to choose the values of the constants (did I put the values or the numerical values? - maybe not). Anyway, the definition of the units keeps changing while the definition of the constants is constant (-ish). So if in 2011 the definition of the ampere changes, then the numerical value of Z0 could change but its definition will be the same, it will just be measured against a slightly different yardstick. Also, the numerical value of Z0 will then (probably (unless the kg (and therefore the N) are redefined at the same time)) be subject to experimental error, whereas at the moment it is not. This interesting and relevant, but peripheral to significance of Z0, being more to do with the definition of the units. I intended to convey this when I originally wrote the 'Exact value' section - but I was to terse. --catslash (talk) 18:36, 24 February 2008 (UTC)
  • (this is a similar point to the preceding one, but after more thought)... (1) The speed of light (for example) 'existed' as a physical quantity before the invention of the metric system. And (2), I wouldn't consider \stackrel{\mathrm{def}}{=} to be a symmetric relation. So I'm happy with
1 \mathrm{metre} \stackrel{\mathrm{def}}{=} c \frac{1 \mathrm{second}}{299792458}
but not
c \stackrel{\mathrm{def}}{=} 299792458 \mathrm{metre}/\mathrm{second}
because
  • If we were to choose a different number, then the size of the metre changes (relative to (say) my height), but the magnitude of the speed of light stays the same (relative to (say) the speed of a snail).
  • The size of the metre has changed in the past, and with it the number of metres per second in the speed of light - but the actual speed of light stayed the same and the universe went on unchanged.
Does that make any sense? --catslash (talk) 22:36, 24 February 2008 (UTC)