[ExI] CQT Researcher Uncovers Quantitative Link Between Quantum Non-Locality and Uncertainty.

[BillK]

On Sun, Dec 5, 2010 at 6:19 AM, Damien Broderick wrote:
> Presumably the photon is bumping into, and interacting with, all kinds of
> things on the way to the cardboard, but they apparently don't count as
> "measurements." >
>
> Air molecules, say, So, for example, does the double slit gag work better,
> more clearly, if it's done in vacuo rather than through the air of the lab?
> What happens if you run your photons or electrons through water before they
> hit the slits?
>
>

That's a simple question, but the answer gets as complicated as you like.  :)

I'll start with a few simple explanations that experts will start
picking holes in, but might be`enough for you.

Basically light doesn't react with air molecules. That's why we can
see. If our eyes were sensitive to different wavelengths that do react
with air, our eyesight would be poor and that model didn't survive
evolution.

----------------------
You next question is probably 'WHY doesn't light react with air molecules?'
(Careful, you're getting more complicated).


Photons are very tiny and gas molecules are widely separated, so hits
are rare. But light does weaken, the more stuff it has to go through.
Occasional hits do happen. Think of absorption lines in light from
distant stars.

By default any object will be transparent to a certain wavelength
(color) of light, unless that wavelength is of the exact energy needed
to cause something to happen in the object, like promoting an electron
to a higher energy level. The molecules in air aren't effected much by
the visible wavelengths of light, so most of the time light will pass
through the air without having an effect on it. (Different
wavelengths, like X-rays, can see through flesh).

When a photon (of any region of the spectrum) hits an atom a number of
things can occur:
1) the atom can absorb the energy and an electron will move to a
higher state within it, this can either be stored or released in
another frequency e.g. metals often release heat, and phosphorus turns
UV into visible light
2) the electron can jump, revolve once and release the photon back in
the opposite direction i.e. reflection
3) the atom may not be able to absorb the energy and the electron may
continue uninhibited.

There are also all sorts of scattering processes that can occur. In
scattering the photon is not actually absorbed, but 'bounces' off in a
different direction, sometimes at a different wavelength. Scattering
is what causes the sky to be blue, since nitrogen scatters blue light
more than other colors.
----------------------


If you want to go to the top for the most complicated explanation, it
is Quantum Electrodynamics.
<https://secure.wikimedia.org/wikipedia/en/wiki/Quantum_electrodynamics>
Feynman has some good lectures (and books) on it.


BillK