Planck\'s constant

[editor]

Brian Greene, in his book \'The Elegant Universe\' Chapt 4 talks about Planck\'s constant. He assures us that it is h bar. In the notes to the chapter he gives the value as 1.05 x 10^-27 gram.cm/s this is indeed the value for h bar, leaving aside his choice of strange values ( don\'t we all use Joule.second these days, i.e. 6.626 x 10^-34 kg.(m^2/s^2).s ) But that\'s not Planck\'s constant which is h. It is h/2pi. Why the confusion ??

Perhaps Xerxes could ask him ??

[Flynnstone]

I noticed that one when i was reading it, it is a bit strange., then again h-bar is as prevalent in quantum mechanice as h is so mayb its just some obscure convention.

[Edited on 1-22-2005 by Flynnstone]

[editor]

Thanks for the reply.
\'maybe its just some obscure convention\'
Not if you are calculating E = hf, for example, then it would be hbar*2pi*f Puzzling. although we do use hbar*omega.
Maybe this is being pedantic, but physics should be precise.

[Xerxes314]

Well, that\'s just the thing. f is not an important quantity. Calculus works on radians, not circles. So h-bar is more important because it multiplies frequency in radians rather than h which multiplies frequency in hertz. Or something like that. At the end of the day, it\'s really just whatever you find more convenient.

Xerxes

[Flynnstone]

Originally posted by editor
Thanks for the reply.
\'maybe its just some obscure convention\'
Not if you are calculating E = hf, for example, then it would be hbar*2pi*f Puzzling. although we do use hbar*omega.
Maybe this is being pedantic, but physics should be precise.

Physics is presice but he does state that what he\'s calling plancks constant is actualy h-bar so he\'s fairly clear on it. Science is also about conventions; like astronomers enjoying the use of nonstandard units.