Re: [Phys-l] Is light pure energy?

[Carl Mungan <mungan@usna.edu>]

> Feynman's words provide a description of a calculation.  They are not the 
> calculation.  As long as they lead to the correct calculation, it matters 
> not that he has not led you to a variety of other possible calculations.
> I suggest viewing the words as a sort of poetry, the mathematics carries 
> the essence of the physics.
> 					Regards,
> 						Jack

I basically agree. I would say the words are intentionally a bit colloquial or unpolished. I think that's how Feynman prefers to speak, particularly in his works for broader audiences.

In a related vein, I have been taken to task (elsewhere) a bit for disagreeing (rigourously) with Feynman's words that "work has been converted to heat" in discussing sliding friction elsewhere in the Lectures (Vol. 1). But I think it's the same thing: not very precise but we know that he knows how to do the calculations and physics. Still, that doesn't mean we shouldn't try to be more precise in our choice of words when we can and when the audience can understand it. (One must also add however that word usage evolves with time -- terms like "energy" and "heat" have developed more precise pedagogical frameworks nowadays.) -Carl