Re: [Phys-L] quantum physics

[David Bowman <David_Bowman@georgetowncollege.edu>]

Regarding:

> Quantum mechanics contains and explains classical physics, but
> the converse is not true. Really not. It makes no sense to try
> to explain (much less define) QM directly in terms of classical
> particles or waves.
>
> Quantum mechanics is not classical, except in certain limits.
> Classical waves are a classical idea.
> Classical particles are a classical idea.
> So, again: It makes no sense to try to explain (much less
> define) QM directly in terms of classical particles or waves.
>
> Rather than saying something is both a wave and a particle, I
> prefer to say it is neither. That is: In QM there is only stuff.
> Sometimes stuff looks sorta like a classical wave and sometimes
> stuff looks sorta like a classical particle, but mostly it's
> just stuff. Sui generis.
>
> We can use analogies to hint at the nature of real (i.e.
> quantum mechanical) universe, in the same way that it is
> possible to communicate the idea of "blue triangle" without
> actually exhibiting one:
>    https://av8n.com/physics/img48/blue-triangle.png
>
> It takes a big leap of the imagination to go from things we can
> get our arms around to the real quantum mechanical stuff.

Amen.  The content of JSD's nice discussion here is why I have always tried to use the Chinese story of the 5 blind men and the elephant as a crude analogy when attempting to explain the relationship of the quantum world to the classical one to introductory level students.  In the analogy the elephant is the quantum model of nature and the character of the elephant's ear is *sort of* like the particle limit of QM, and the characteristic properties of the elephant's trunk is *sort of* like the classical wave limit.  And the argument regarding the contradictory properties of an ear and a trunk between the blind men who felt each body part in discussing the nature of the elephant is analogous to arguments between people who argue about the contradictions and incompatibilities in wave-like or particle-like phenomena.

> The leap is much bigger than can be captured by the idea of
> "duality".

Yes.  That is *another* reason why I like the elephant analogy.  There are 5 blind men arguing amongst themselves who felt 5 different elephant body parts--not just the 2 particle and wave guys, & the extra blind men and arguments correspond to other extra weirdnesses of the quantum model that can't be simply lumped into either a classical particle or classical wavelike picture.

David Bowman