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Author Topic: What is the specific formula of the electron ?  (Read 12789 times)

Offline Soul Surfer

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Re: What is the specific formula of the electron ?
« Reply #25 on: 30/08/2006 10:20:23 »
This is probably the place to clarify one of the questions that I have often heard about atomic structure.  That is why don't the electrons collapse on to the nucleus  but move in orbits.  Now its clear that the S1 and above electrons have angular momentum and are kept away from the nucleus ny the two S0 electrons with opposing spins but what about the S0 ones that have no net angular momentum.  The answer is that they HAVE collapsed on to the nucleus but the low mass and energy content of the electron means that they are quite big physically and it is much more likely that they will be found outside the nucleus than inside it!

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Offline bostjan

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Re: What is the specific formula of the electron ?
« Reply #26 on: 30/08/2006 10:47:40 »
i still don't understand the correlation between bell's theorem and spin.
 

Offline lightarrow

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Re: What is the specific formula of the electron ?
« Reply #27 on: 30/08/2006 12:32:36 »
quote:
Originally posted by bostjan

i still don't understand the correlation between bell's theorem and spin.


http://atschool.eduweb.co.uk/rmext04/92andwed/pf_quant.html#Q30

Here it was described an experiment made with photons, but could be made with electrons, protons ecc. as well.
« Last Edit: 30/08/2006 12:34:32 by lightarrow »
 

Offline syhprum

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Re: What is the specific formula of the electron ?
« Reply #28 on: 30/08/2006 13:35:18 »
I grew up in an age before neutrons when atomic nuclei contained electrons and protons, atoms had nuclei with little solid electrons whizzing around them and we had a nice solid ether for electo-magnetic waves to propagate in.
I sometimes long for the old days and find modern physics rather puzzling (I am not as old as Methusala but our school textbooks were)

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Offline bostjan

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Re: What is the specific formula of the electron ?
« Reply #29 on: 31/08/2006 04:37:10 »
the epr paradox has to do with measuring two correlated spins simultaneously.  i don't think bell's theorem contradicts the existance of spin all together.
 

Offline lightarrow

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Re: What is the specific formula of the electron ?
« Reply #30 on: 31/08/2006 07:49:38 »
quote:
Originally posted by bostjan

the epr paradox has to do with measuring two correlated spins simultaneously.  i don't think bell's theorem contradicts the existance of spin all together.
Please, explain the result of Stern-Gerlach experiment I have showed you in my post, in terms of spin as a real property of an atom or electron or else.
 

Offline bostjan

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Re: What is the specific formula of the electron ?
« Reply #31 on: 31/08/2006 20:08:02 »
Just read the paper you posted, Bell's original paper, and the EPR paradox.

The Stern-Gerlach experiment shows that spin is real and observable  A Stern-Gerlach device only measures the z component of spin (where z is along the axis of the beam.  If the spin is one half, the beam splits into two parts, one with the z-component of spin positive and the other negative.

Bell's theorem deals with hidden variables (the hidden variable being the correlation between the spin states of two separate particles heading in opposite direction).  Bell showed that these hidden variables are illogical (those variables that relate the two spin states).  The reason Stern-Gerlach is mentioned is because it is the apparatus used to measure spin.

Quantum spin states are very real.  See Scientific American 241, 158 (Nov. 1979) by B d'Espagnat.
 

Offline lightarrow

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Re: What is the specific formula of the electron ?
« Reply #32 on: 01/09/2006 08:08:36 »
quote:
Originally posted by bostjan

Just read the paper you posted, Bell's original paper, and the EPR paradox.

The Stern-Gerlach experiment shows that spin is real and observable  A Stern-Gerlach device only measures the z component of spin (where z is along the axis of the beam.  If the spin is one half, the beam splits into two parts, one with the z-component of spin positive and the other negative.

Bell's theorem deals with hidden variables (the hidden variable being the correlation between the spin states of two separate particles heading in opposite direction).  Bell showed that these hidden variables are illogical (those variables that relate the two spin states).  The reason Stern-Gerlach is mentioned is because it is the apparatus used to measure spin.

Quantum spin states are very real.  See Scientific American 241, 158 (Nov. 1979) by B d'Espagnat.

I would like to understand if you agree with me or not and, if not, exactly where, about these (mine) statements:

1.If a particle's spin x-component is a real property of the particle, then measuring its z-component should not affect the previous one; otherwise it's not a property of the particle alone, at least, but of the entire system particle-detector .

2.If that it's a real, intrinsic property of the particle, then it should behave as an "hidden" variable.

3.Bell's theorem showed that the hidden variable hypothesis gives results inconsistent with quantum mechanics results. Specifically, according hidden variable hypothesis, the result is something like:
N1 < N2, while, according Q.M., the result is N1 = A, where A > N2.

4.Experimental results have shown that the results agree with Q.M.
 

Offline Soul Surfer

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Re: What is the specific formula of the electron ?
« Reply #33 on: 01/09/2006 11:08:11 »
We are talking here about a quantum level measurement.  Because of the uncertainty principle you cannot make any measurements without affecting them.
to measure the spin of an electron in any direction you create a field that will turn the spin in that direction. if the spin is not in that direction it turns and you detect a photon that reperesents the energy used in turning the spin  id does not turn and nothing happens and you do not detect the photon  either way the spins end up aligned in the way your apparatus has been set to them

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Offline lightarrow

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Re: What is the specific formula of the electron ?
« Reply #34 on: 01/09/2006 12:49:27 »
quote:
Originally posted by Soul Surfer

We are talking here about a quantum level measurement.  Because of the uncertainty principle you cannot make any measurements without affecting them.
to measure the spin of an electron in any direction you create a field that will turn the spin in that direction. if the spin is not in that direction it turns and you detect a photon that reperesents the energy used in turning the spin  id does not turn and nothing happens and you do not detect the photon  either way the spins end up aligned in the way your apparatus has been set to them
I knew I was exploring an  undermined ground here!

Please don't shoot at me for my statements! (I'm joking, of course).
I'm just trying to understand better; I don't even have a degree in physics (I studied it for 3 years and then I had to stop), so, forgive me if I say something silly.

When you say "...to measure the spin of an electron in any direction you create a field that will turn the spin in that direction..." you are assuming, I presume, that electrons have this intrinsec property that you call spin?

If your answer is "yes", mine is: no, because, in this case, it would be an hidden variable.
Maybe I'm making a mistake.
 

Offline bostjan

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Re: What is the specific formula of the electron ?
« Reply #35 on: 02/09/2006 07:01:01 »
1.  It is, indeed a property of the measurement.  Theoretical spin states can vary in all sorts of ways, but measuring the spin in a certain direction will only show you one integral or half-integral state (i.e. +1/2 or -1/2 for an electron).

2.  Spin is not a hidden variable, it is measured directly by a Stern-Gerlach apparatus and although it is a property of a quantum particle, it is quite real, much like momentum or charge.  Think of charge as an intrinsic property of a particle with integer values.

3.  The hidden variables in question are about finding a way to determine the measured spin states, in effect taking away all randomization of the measurement.  These are some unseen degrees of freedom, that were postulated by Einstein, Bohm, de Broglie, and Bethe, but are regarded by a majority of physicists to be debunked now, thanks to John Bell and a plethora of experiments to back him up.

4.  Yes.  (S Freedman and J Clauser, Phys Rev Lett 28, 938 (1978))

 

Offline lightarrow

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Re: What is the specific formula of the electron ?
« Reply #36 on: 02/09/2006 11:36:55 »
quote:
Originally posted by bostjan

1.  It is, indeed a property of the measurement.  Theoretical spin states can vary in all sorts of ways, but measuring the spin in a certain direction will only show you one integral or half-integral state (i.e. +1/2 or -1/2 for an electron).

2.  Spin is not a hidden variable, it is measured directly by a Stern-Gerlach apparatus and although it is a property of a quantum particle, it is quite real, much like momentum or charge.  Think of charge as an intrinsic property of a particle with integer values.

3.  The hidden variables in question are about finding a way to determine the measured spin states, in effect taking away all randomization of the measurement.  These are some unseen degrees of freedom, that were postulated by Einstein, Bohm, de Broglie, and Bethe, but are regarded by a majority of physicists to be debunked now, thanks to John Bell and a plethora of experiments to back him up.

4.  Yes.  (S Freedman and J Clauser, Phys Rev Lett 28, 938 (1978))
Ok, thank you for your explanation, bostjan.

I'm still puzzled, however: what does "(The hidden variables in question are about finding a way)...to determine the measured spin states..." exactly mean?
 

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Re: What is the specific formula of the electron ?
« Reply #36 on: 02/09/2006 11:36:55 »

 

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