Re: How to make measurements of a particle



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Topic: Science > Physics
User: "Mike Helland"
Date: 04 Aug 2004 11:35:09 AM
Object: Re: How to make measurements of a particle
Bjoern Feuerbacher wrote:

Mike Helland wrote:

Bjoern Feuerbacher wrote:

Mike Helland wrote:


[snip]


Ok, so, can anyone point me to an accessible text on how exactly
how
the measurements are made, all the way through setting up the
experiment, describing what happens, and then ending up with the
numbers?


Irrelevant. This is true for *all* possible measurements.

This follows simply from the wave-particle duality - but can also

be

shown more mathematically from Heisenberg's commutation relation
(which is an axiom of QM).



What do you mean irrelevant?


Exactly what I said. The details of the measurements are irrelevant
for the outcome. The uncertainty principle is true for *all* possible
measurements.

I realize that. But knowing how the an experiment involving electrons
and some light produces a measurement of the electron's position or
momentum should contain some knowledge on exactly how the
electromagnetic interaction works in the real world. And I wish to
learn about the interaction.

I'd like to know how to set up the experiment involving an electron

and

some light.
I'd like to know what happens during the experiment, and
I'd like to know how the measurement follows from that.


Why? What's so important about that special type of experiment?

What I know about the electromagnetic interaction is this:
like charges repel and unlike charges attract.
Because of HUP surely there is more to the basic interaction than what
I know, and understanding how the interaction produces a measurement of
position or momentum should tell me a little more.

All I need is a pointer to them.


So Sam Wormley's links did not help?

No. One of his links was to the HUP, which you said I got essentially
right, and the other was an unfriendly reference to one of my ideas.
How to measure the position of an electron was not discussed in either
link.
I can't find what I'm looking for using
http://www.google.com/search?hl=en&ie=UTF-8&q=experiment+measure+position+electron&btnG=Google+Search
I thought someone here or in sci.physics.research would have a more
specific explanation of how this is acheived.
.

User: "Bjoern Feuerbacher"

Title: Re: How to make measurements of a particle 05 Aug 2004 03:03:39 AM
Mike Helland wrote:
[snip]

But knowing how the an experiment involving electrons
and some light produces a measurement of the electron's position or
momentum should contain some knowledge on exactly how the
electromagnetic interaction works in the real world. And I wish to
learn about the interaction.

I don't know for sure, but I would guess that the photons scatter
of the electrons (essentially Compton scattering), and from the
changed direction and energy of the photons, one can get information
about the positions and momenta of the electrons.
[snip]

What I know about the electromagnetic interaction is this:

like charges repel and unlike charges attract.

That's electrostatics only. What about the forces between currents
(magnetostatic forces), for starters? What about the forces which
are exerted by electromagnetic waves on charges?

Because of HUP surely there is more to the basic interaction than what
I know,

That has little to do with the HUP.

and understanding how the interaction produces a measurement of
position or momentum should tell me a little more.

Perhaps you should read up on the Compton effect. But as I said: that
has little to do with the HUP.
[snip]
Bye,
Bjoern
.


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