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Topic: Science > Physics
User: "patrick"
Date: 26 Apr 2005 04:39:08 AM
Object: electron
The electron charge to mass ratio e/m is known from experiments. So there is
no doubt about that.
But has experiment established for sure the absolute mass and charge e and m
independently?
In most calculations in QM and QED it is the ratio e/m that is used i think?
Surely until e and m is established for sure there must be doubt about the
electrons extent and whether it is a single particle or a collection of sub
particles?
patrick
.

User: "Old Man"

Title: Re: electron 26 Apr 2005 07:28:30 PM
"patrick" <networkone@eircom.net> wrote in message
news:W_nbe.52225$Z14.42457@news.indigo.ie...

The electron charge to mass ratio e/m is known from experiments. So there
is no doubt about that.

But has experiment established for sure the absolute mass and charge e and
m independently?

Electron charge: Milliken oil drop experiment.

In most calculations in QM and QED it is the ratio e/m that is used i
think?

No.
Compton wave length: hbar / m_e * c
Fine structure constant: e^2 / hbar*c

Surely until e and m is established for sure there must be doubt about the
electrons extent and whether it is a single particle or a collection of
sub particles?

There's no doubt about Patrick's ignorance.

patrick

[Old Man]
.

User: "Gregory L. Hansen"

Title: Re: electron 26 Apr 2005 09:11:28 AM
In article <W_nbe.52225$Z14.42457@news.indigo.ie>,
patrick <networkone@eircom.net> wrote:

The electron charge to mass ratio e/m is known from experiments. So there is
no doubt about that.


But has experiment established for sure the absolute mass and charge e and m
independently?
In most calculations in QM and QED it is the ratio e/m that is used i think?

It's been known for about a hundred years.
http://dbhs.wvusd.k12.ca.us/webdocs/AtomicStructure/Determine-electron-charge.html
I don't know how modern measurements are done, but they might involve a
velocity selector and an energy-sensitive detector.


Surely until e and m is established for sure there must be doubt about the
electrons extent and whether it is a single particle or a collection of sub
particles?

The values of e and m have very little to do with whether the electron has
size or whether it's a single particle. E.g. the proton has the same
magnitude of charge as the electron, and a known m, and it is composite.
The muon has the same charge but a larger mass as the electron, and it is
elementary.
The most straightforward way to explore the electron's composition is by
scattering experiments. Point particles scatter differently than
composite particles, that's how the proton structure was found.
--
"You're not as dumb as you look. Or sound. Or our best testing
indicates." -- Monty Burns to Homer Simpson
.
User: "John Sefton"

Title: Re: electron 26 Apr 2005 10:31:14 AM
Gregory L. Hansen wrote:

In article <W_nbe.52225$Z14.42457@news.indigo.ie>,
patrick <networkone@eircom.net> wrote:

The electron charge to mass ratio e/m is known from experiments. So there is
no doubt about that.


But has experiment established for sure the absolute mass and charge e and m
independently?
In most calculations in QM and QED it is the ratio e/m that is used i think?



It's been known for about a hundred years.

http://dbhs.wvusd.k12.ca.us/webdocs/AtomicStructure/Determine-electron-charge.html

I don't know how modern measurements are done, but they might involve a
velocity selector and an energy-sensitive detector.


Surely until e and m is established for sure there must be doubt about the
electrons extent and whether it is a single particle or a collection of sub
particles?



The values of e and m have very little to do with whether the electron has
size or whether it's a single particle. E.g. the proton has the same
magnitude of charge as the electron, and a known m, and it is composite.
The muon has the same charge but a larger mass as the electron, and it is
elementary.

The most straightforward way to explore the electron's composition is by
scattering experiments. Point particles scatter differently than
composite particles, that's how the proton structure was found.

Not to put too fine a point
on the original poster's concern,
but in the realm of points, there are
big points and little points.
The big points are the ones we are going
to be able to resolve with the next improvement
in our technology e.g. better microscope
but the fine points IMIO are cut from finer
cloth.
The Planck length dictates how big the proton
has to be.
The electron is *the insides* of the proton
which are ejected upon its creation like a spray
of millions of stars, which *somehow* stay together
as a (very deformable) cloud stretching from the
nucleus to the atom's edge. The matrix
this material is drawn on is much finer than the
Planck length- it is the next order down.
In the Galaxy Model for the atom, an electron is
a spiral arm of stars, separated from the other electrons
by bands of dust.
http://users.accesscomm.ca/john/
John
.


User: "Bjoern Feuerbacher"

Title: Re: electron 26 Apr 2005 05:21:32 AM
patrick wrote:

The electron charge to mass ratio e/m is known from experiments. So there is
no doubt about that.


But has experiment established for sure the absolute mass and charge e and m
independently?

Yes.
<http://pdg.lbl.gov/2004/listings/s003.pdf>

In most calculations in QM and QED it is the ratio e/m that is used i think?

Wrong. In most calculations, what is used are m and alpha, which is
e^2/(4 pi epsilon_0 hbar c)

Surely until e and m is established for sure there must be doubt about the
electrons extent and whether it is a single particle or a collection of sub
particles?

People have searched for *decades* now for a substructure of
electrons. They found none so far.
Bye,
Bjoern
.


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