Re: [Phys-L] Math List Serves

[David Bowman <David_Bowman@georgetowncollege.edu>]

Regarding Brian W's expanded explanation:

> I see that you (or I) were hoist by a petard. A punctuation
> petard, no less. I will capitalize  to exaggerate the point:
> Consider a LONG uniform thin rigid rod of NEGLIGIBLE THICKNESS
> AND LENGTH,           L....
> It were the comma that done it, yer honor.

OK, *now* I see your point and the possibility for the interpretation of my statement as being self-contradictory. But I think it isn't so much a matter of a misplaced or missing comma as one of a possibly missing clarifying word.  The word in question is 'of'.  If I had written
"Consider a long uniform thin rigid rod of negligible thickness and *of* length, L precariously balanced and standing vertically upright at rest on a frictionless horizontal floor." then I think there would be no possible occasion for thinking the word 'negligible' also modified the word 'length' in addition to the word 'thickness'.  The reason for the lack of a comma between 'thickness' and 'and length' is that the series following 'rod' and describing its size & shape had only 2 parts, the negligible thickness part and the length part.  Traditionally, commas are not inserted to separate the constituent pieces of series of only 2 parts.  The reason for the comma after 'length' and before 'L' is that both the word 'length' and 'L' refer to the same concept and are being identified with each other.  The comma pause between them is supposed to indicate that the 'L' after the comma is actually a restatement of the same thing/concept as the 'length' just before it.

David Bowman