Re: Where is the original data?

[Chuck Britton <britton@ACADEMIC.NCSSM.EDU>]

When I first had a student come to me and gleefully announce that their
chemistry class had just calculated the 'wavelength' of a golf ball
traveling at 50 m/s I was a bit taken aback.

I now ask them to repeat the calculation for the ball as it sits
'motionless' on the tee!!!

They seem to get a bit freaked out over the INFINITE wavelength!

THEN they might be ready to begin learning about the REALLY weird world of
quantum mechanics where we must insist that all objects that share the same
Q #'s are truely indistinguishable from their bretheren and hence the
arising of the Exclusion Principle etc. Two pieces of a golf ball DON'T
count as being indistinguishable and hence DON'T get treated with de
Broglie (or any OTHER) wave characteristics.


> > Well, without worrying about any of the niceties, the de Broglie
> > wavelength of the elephant is surely extremely short
>
> ...and meaningless. The niceties are *very* important. Just because
> you can plug the mass and velocity of an elephant into a formula
> you should not conclude that you have inferred something physically
> relevant by doing so. While buckyballs can be made to interfere
> with one another or with themselves, elephants cannot. To do so an
> elephant would have to remain in a coherent quantum state for a
> period of duration at least as great as its length divided by the
> speed of light.
>
> We are always railing against the tendency of our students to take
> any formula that seems to have the correct symbols and then to plug
> in the data given (often with no attention paid to dimensions) to
> obtain a numerical answer. That's just what you instantiate if you
> perform this silly calculation.
>
> It may be "fun" to do so, but don't do it, unless you disclaim the
> result's meaning immediately afterward.
>
> Leigh (the killjoy curmudgeon)


It's no accident that stressed          Chuck Britton
spelled backwards is desserts.          britton@odie.ncssm.edu

It's no accident that stressed          Chuck Britton
spelled backwards is desserts.          britton@odie.ncssm.edu