[Phys-L] foundations of QM : fluctuations

[John Denker <jsd@av8n.com>]

On 02/18/2014 07:19 AM, David Bowman wrote:
> In short, my point is a point about words, not physics.  Physical 
> arguments won't affect that.

Then we have nothing to discuss.  I'm interested in the physics.
I'm not interested in playing word games.

> My point is that zero point 'motion' ought to be called that if 
> something is actually moving,

The physics says that the atomic electron is moving.  This
is objectively measurable.  Moving has to do with velocity.
If the velocity were zero, then ⟨v^2⟩ would be zero, and
it's not.

It may be that the long-time average ⟨v⟩ is zero, but that
does not mean that v itself is zero.  Indeed, that's pretty
close to being a definition of fluctuation, when the average
⟨v⟩ is zero but ⟨v^2⟩ is not.

> measuring the radiation supposedly going in or out would require
> measuring at least one photon's worth of radiation in transit.

Nonsense!

You can choose to measure anything you like, but bear in 
mind that other people are free to choose differently.

In particular, I'm pretty sure that voltmeters exist.  If
you measure the voltage, it fluctuates.  Really it does.
This is objectively measurable.  No word-games are going
to change this.

If you /choose/ to use the photon-number basis, you won't
see the fluctuations, but that's a choice, not a universal
law.  This is the opposite of looking under the lamp-post.
If you insist on looking in the one single place where the
phenomenon can't be seen, you won't see anything.  Meanwhile
everybody else is seeing the fluctuations.

Voltmeters exist.  Voltmeters can see the fluctuations.
Been there, done that.

Zero-point motion is motion.