- From: Ian Hickson <ian@hixie.ch>
- Date: Wed, 12 Dec 2007 06:19:57 +0000 (UTC)

On Wed, 1 Nov 2006, Christoph P?per wrote: > > The second to last example should probably better read: > > <var>E</var> = <var>m</var> ? <var>c<var><sup>2</sup> > > or maybe, as the speed of light is a constant, > > <var>E</var> = <var>m</var> ? c<sup>2</sup>. If you are suggesting adding the multiplication sign, I disagree; the equation is always just written E=mc^2 in my experience. On Sat, 4 Nov 2006, Matthew Paul Thomas wrote: > > Is that equation ever legitimately rendered (in physics textbooks etc) > with the "m" in a different style from the "c"? If not, perhaps the > definition of <var> needs to be expanded to include physical constants. On Mon, 6 Nov 2006, David Walbert wrote: > > No, constants and variables are presented identically in equations. The > student simply is expected to know whether they are constants or not. > This requires some context, but the equation makes sense only with > context anyway. If I understand the draft standards correctly the var > would be defined by a prior dfn element, and that is where one would > note (if one believed it necessary) that the speed of light was > constant. > > If that equation is considered only algebraically, then E, m, and c are > treated identically anyway -- there is no difference in how you handle > them mathematically. > > Is var really not meant to include constants represented algebraically? > That would take semantic markup to a level that seems to me frankly > silly. I agree, as does the spec. Constants in physics are variables in mathematics, and the spec explicitly refers to variables in the mathematical sense. -- Ian Hickson U+1047E )\._.,--....,'``. fL http://ln.hixie.ch/ U+263A /, _.. \ _\ ;`._ ,. Things that are impossible just take longer. `._.-(,_..'--(,_..'`-.;.'

Received on Tuesday, 11 December 2007 22:19:57 UTC