| Topic: |
Science > Physics |
| User: |
"ganesh" |
| Date: |
12 Apr 2004 10:32:24 AM |
| Object: |
some doubts on spin |
hi,
Am not sure if these Q makes sense in the first place, but here goes.
1) The electron spin results in a magnetic field. So is the generalization
true: All half integer (1/2, 3/2, 5/2....) lead to magnetic field.
Similarly, is it true that none of the integer spins lead to magnetic fields.
If so, is there any intuition behind it, or its just an observed fact,
and nothing more can be said about it??
2) If two fermions result in a composite particle having an integer spin, then
is this spin anyway different from an elementary boson having the same
integer spin?? By similarity I mean in the experimental sense. The same
experiment which can detect the spin of the elementary boson, should in
principle be also be able to detect the spin of the composite boson (composed
of the two fermions).
3) Does the experimental detection of spin depend on whether the particle is
massive or not. If my understanding is right, if I've a massless particle
say photon havin a spin s in the z-direction, and a lorentz boost is
is applied along z-axis, then the spin s remains the same in the other
reference frame also. But for a massive particle this may not be true.
4) Does a neutrino have a zero rest mass or a non-zero rest mass?? I seem to
be comming across both.
ganesh
.
|
|
| User: "aran" |
|
| Title: Re: some doubts on spin |
13 Apr 2004 06:15:42 AM |
|
|
"ganesh" <gans1973@rediffmail.com> wrote in message
news:510dfbbf.0404120732.6159c080@posting.google.com...
hi,
Am not sure if these Q makes sense in the first place, but here goes.
1) The electron spin results in a magnetic field. So is the generalization
true: All half integer (1/2, 3/2, 5/2....) lead to magnetic field.
Similarly, is it true that none of the integer spins lead to magnetic
fields.
If so, is there any intuition behind it, or its just an observed fact,
and nothing more can be said about it??
Spin is tiny magnet, regardless half or integer. I am measuring nuclear
spins (NMR).
D has spin one and is very well measured. You must note here that neutron
has no charge,
but has spin half. You can not measure spin-one of electrons (ESR) or other
fermions since
two spins in the same orbit has always opposite and vanish (Pauli's excl.).
This is why only
the radicals ("alone" electrons in a substance) and some excited species in
a special way
can be measured by ESR.
Photon has no real spin. If photon had spin one, in a magnetic field the
energy would be
splitt in three levels, due to S=-1,0,+1. It does not. And S=0 of photon has
never been observed.
However phon acts like it has a spin +/-1 because it has a definite "angular
momentum" although it has
no orbital angular momentum (so that angular momentum must be due to
intrinsic moment). This is due to polarisation. No polarisation, no
propogation of the wave. Even "plane" waves can be decomposed
to two circular polarisation, but in opposite direction (spin +/-).
2) If two fermions result in a composite particle having an integer spin,
then
is this spin anyway different from an elementary boson having the same
integer spin?? By similarity I mean in the experimental sense. The same
experiment which can detect the spin of the elementary boson, should in
principle be also be able to detect the spin of the composite boson
(composed
of the two fermions).
3) Does the experimental detection of spin depend on whether the particle
is
massive or not. If my understanding is right, if I've a massless
particle
say photon havin a spin s in the z-direction, and a lorentz boost is
is applied along z-axis, then the spin s remains the same in the other
reference frame also. But for a massive particle this may not be true.
4) Does a neutrino have a zero rest mass or a non-zero rest mass?? I seem
to
be comming across both.
ganesh
.
|
|
|
| User: "" |
|
| Title: Re: some doubts on spin |
13 Apr 2004 12:46:34 PM |
|
|
"aran" <m.a.ersin@kjemi.uio.no> wrote in message news:<c5gi4p$1hn$1@readme.uio.no>...
[snip]
Spin is tiny magnet, regardless half or integer.
Welll.... It's not the magnitude of the spin that determines
whether or not it has a magnetic field. That is true.
You can not measure spin-one of electrons (ESR) or other
fermions since
two spins in the same orbit has always opposite and vanish (Pauli's excl.).
This is why only
the radicals ("alone" electrons in a substance) and some excited species in
a special way
can be measured by ESR.
What is denied by the Pauli exclusion is two electrons in the exact
same state. However, it is possible for one electron to be in the
ground state and another to be in an excited state. So you could
have Helium with one electron in the lowest energy S and another in
the next-to-lowest, and so have them sum up to total spin 1. The
system would not be stable, of course.
Photon has no real spin. If photon had spin one, in a magnetic field the
energy would be
splitt in three levels, due to S=-1,0,+1. It does not. And S=0 of photon has
never been observed.
However phon acts like it has a spin +/-1 because it has a definite "angular
momentum" although it has
no orbital angular momentum (so that angular momentum must be due to
intrinsic moment). This is due to polarisation. No polarisation, no
propogation of the wave. Even "plane" waves can be decomposed
to two circular polarisation, but in opposite direction (spin +/-).
No, photons are spin 1. They don't have a 0 component because they
are massless.
Socks
.
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|
| User: "FrediFizzx" |
|
| Title: Re: some doubts on spin |
13 Apr 2004 06:45:48 PM |
|
|
<puppet_sock@hotmail.com> wrote in message
news:c7976c46.0404130946.40712f78@posting.google.com...
| "aran" <m.a.ersin@kjemi.uio.no> wrote in message
news:<c5gi4p$1hn$1@readme.uio.no>...
| [snip]
| > Spin is tiny magnet, regardless half or integer.
|
| Welll.... It's not the magnitude of the spin that determines
| whether or not it has a magnetic field. That is true.
|
| > You can not measure spin-one of electrons (ESR) or other
| > fermions since
| > two spins in the same orbit has always opposite and vanish (Pauli's
excl.).
| > This is why only
| > the radicals ("alone" electrons in a substance) and some excited species
in
| > a special way
| > can be measured by ESR.
|
| What is denied by the Pauli exclusion is two electrons in the exact
| same state. However, it is possible for one electron to be in the
| ground state and another to be in an excited state. So you could
| have Helium with one electron in the lowest energy S and another in
| the next-to-lowest, and so have them sum up to total spin 1. The
| system would not be stable, of course.
|
| > Photon has no real spin. If photon had spin one, in a magnetic field the
| > energy would be
| > splitt in three levels, due to S=-1,0,+1. It does not. And S=0 of photon
has
| > never been observed.
| > However phon acts like it has a spin +/-1 because it has a definite
"angular
| > momentum" although it has
| > no orbital angular momentum (so that angular momentum must be due to
| > intrinsic moment). This is due to polarisation. No polarisation, no
| > propogation of the wave. Even "plane" waves can be decomposed
| > to two circular polarisation, but in opposite direction (spin +/-).
|
| No, photons are spin 1. They don't have a 0 component because they
| are massless.
I think really they have helicity instead of spin.
FrediFizzx
.
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|
|
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|
| User: "Igor" |
|
| Title: Re: some doubts on spin |
12 Apr 2004 07:31:15 PM |
|
|
(ganesh) wrote in message news:<510dfbbf.0404120732.6159c080@posting.google.com>...
hi,
Am not sure if these Q makes sense in the first place, but here goes.
1) The electron spin results in a magnetic field. So is the generalization
true: All half integer (1/2, 3/2, 5/2....) lead to magnetic field.
Similarly, is it true that none of the integer spins lead to magnetic fields.
If so, is there any intuition behind it, or its just an observed fact,
and nothing more can be said about it??
Not all particles with half-integer spins have a magnetic field. Only
particles that have both charge and spin will possess magnetic fields.
Same goes for integer spin particles also. There are no restrictions
on spin quantum numbers leading to magnetic fields, so long as it's a
charged particle.
2) If two fermions result in a composite particle having an integer spin, then
is this spin anyway different from an elementary boson having the same
integer spin?? By similarity I mean in the experimental sense. The same
experiment which can detect the spin of the elementary boson, should in
principle be also be able to detect the spin of the composite boson (composed
of the two fermions).
There's no real difference between a composite particle and a
so-called fundamental particle, at least with respect to spin.
3) Does the experimental detection of spin depend on whether the particle is
massive or not. If my understanding is right, if I've a massless particle
say photon havin a spin s in the z-direction, and a lorentz boost is
is applied along z-axis, then the spin s remains the same in the other
reference frame also. But for a massive particle this may not be true.
Experimental detection really doesn't depend on whether the particle
has a mass or not. It can usually be acertained by how much angular
momentum is transferred in an interaction. What you say about the
distinction between them is correct, but not really relevant to
detection.
4) Does a neutrino have a zero rest mass or a non-zero rest mass?? I seem to
be comming across both.
It seems to be the latter.
ganesh
.
|
|
|
| User: "ganesh" |
|
| Title: Re: some doubts on spin |
13 Apr 2004 03:53:40 AM |
|
|
(Igor) wrote in message news:<d434b6c6.0404121631.a14eaaa@posting.google.com>...
gans1973@rediffmail.com (ganesh) wrote in message news:<510dfbbf.0404120732.6159c080@posting.google.com>...
hi,
Am not sure if these Q makes sense in the first place, but here goes.
1) The electron spin results in a magnetic field. So is the generalization
true: All half integer (1/2, 3/2, 5/2....) lead to magnetic field.
Similarly, is it true that none of the integer spins lead to magnetic fields.
If so, is there any intuition behind it, or its just an observed fact,
and nothing more can be said about it??
Not all particles with half-integer spins have a magnetic field. Only
particles that have both charge and spin will possess magnetic fields.
Same goes for integer spin particles also. There are no restrictions
on spin quantum numbers leading to magnetic fields, so long as it's a
charged particle.
So, if we look at a neutron, a neutron gets deflected in a magnetic field.
But itself will not produce any magnetic field. I'm somehow trying to
understand this. Lets say we have a neutron and an electron. The electron
will exert a force on the neutron via its magnetic field (produced due to
the spin of the electron).
But the neutron will not and cannot exert any force(electric or magnetic)
on the electron. Does this mean when we talk of microscopic particles,
the third law of newton (action and reaction are equal and opp), is just
not applicable?? Or am I missing something??
ganesh
.
|
|
|
| User: "Franz Heymann" |
|
| Title: Re: some doubts on spin |
13 Apr 2004 09:55:35 AM |
|
|
"ganesh" <gans1973@rediffmail.com> wrote in message
news:510dfbbf.0404130053.4a31e4c9@posting.google.com...
thoovler@excite.com (Igor) wrote in message
news:<d434b6c6.0404121631.a14eaaa@posting.google.com>...
gans1973@rediffmail.com (ganesh) wrote in message
news:<510dfbbf.0404120732.6159c080@posting.google.com>...
hi,
Am not sure if these Q makes sense in the first place, but
here goes.
1) The electron spin results in a magnetic field. So is the
generalization
true: All half integer (1/2, 3/2, 5/2....) lead to magnetic
field.
Similarly, is it true that none of the integer spins lead to
magnetic fields.
If so, is there any intuition behind it, or its just an
observed fact,
and nothing more can be said about it??
Not all particles with half-integer spins have a magnetic field.
Only
particles that have both charge and spin will possess magnetic
fields.
Same goes for integer spin particles also. There are no
restrictions
on spin quantum numbers leading to magnetic fields, so long as
it's a
charged particle.
So, if we look at a neutron, a neutron gets deflected in a magnetic
field.
The neutron is a composite particle. It contains both negative and
positive charge. They total out to zero, but they have different
radial distributions.
But itself will not produce any magnetic field.
It does produce a magnetic field, since it has a magnetic moment.
[snip]
Franz
.
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|
| User: "Igor" |
|
| Title: Re: some doubts on spin |
13 Apr 2004 05:43:02 PM |
|
|
(ganesh) wrote in message news:<510dfbbf.0404130053.4a31e4c9@posting.google.com>...
thoovler@excite.com (Igor) wrote in message news:<d434b6c6.0404121631.a14eaaa@posting.google.com>...
(ganesh) wrote in message news:<510dfbbf.0404120732.6159c080@posting.google.com>...
hi,
Am not sure if these Q makes sense in the first place, but here goes.
1) The electron spin results in a magnetic field. So is the generalization
true: All half integer (1/2, 3/2, 5/2....) lead to magnetic field.
Similarly, is it true that none of the integer spins lead to magnetic fields.
If so, is there any intuition behind it, or its just an observed fact,
and nothing more can be said about it??
Not all particles with half-integer spins have a magnetic field. Only
particles that have both charge and spin will possess magnetic fields.
Same goes for integer spin particles also. There are no restrictions
on spin quantum numbers leading to magnetic fields, so long as it's a
charged particle.
So, if we look at a neutron, a neutron gets deflected in a magnetic field.
But itself will not produce any magnetic field. I'm somehow trying to
understand this. Lets say we have a neutron and an electron. The electron
will exert a force on the neutron via its magnetic field (produced due to
the spin of the electron).
But the neutron will not and cannot exert any force(electric or magnetic)
on the electron. Does this mean when we talk of microscopic particles,
the third law of newton (action and reaction are equal and opp), is just
not applicable?? Or am I missing something??
ganesh
The reason a neutron gets deflected in a magnetic field is that it has
a non-zero magnetic dipole moment. In fact, this was a big clue
indicating that the neutron could not have been a truly fundamental
particle -- it has no net electric charge, yet it has a finite
magnetic dipole moment. Anything that has a magnetic dipole moment
will also have a magnetic field, since as far as we know dipoles are
their fundamental sources.
You make a good point in that a spinning particle doesn't necessarily
need to have a net electric charge in order to have a magnetic field.
So long as it has a charge distribution, such as a neutron, it can
have a magnetic field. And if the neutron has a magnetic field, it
must be able to exert magnetic forces, but not electric forces, on the
electron. Frankly, I've never really heard about any experimental
investigations into this effect, but it should occur.
.
|
|
|
| User: "Bjoern Feuerbacher" |
|
| Title: Re: some doubts on spin |
14 Apr 2004 06:10:59 AM |
|
|
Igor wrote:
[snip]
And if the neutron has a magnetic field, it
must be able to exert magnetic forces, but not electric forces, on the
electron. Frankly, I've never really heard about any experimental
investigations into this effect, but it should occur.
Try reading up on "Rosenbluth formula". Essentially it describes the
scattering of electrons by neutrons (or protons) due to the magnetic and
electric "density distribution" of the neutron (resp. proton).
Bye,
Bjoern
.
|
|
|
|
| User: "Gregory L. Hansen" |
|
| Title: Re: some doubts on spin |
13 Apr 2004 07:45:59 PM |
|
|
In article <d434b6c6.0404131443.2597a2f3@posting.google.com>,
Igor <thoovler@excite.com> wrote:
gans1973@rediffmail.com (ganesh) wrote in message
news:<510dfbbf.0404130053.4a31e4c9@posting.google.com>...
thoovler@excite.com (Igor) wrote in message
news:<d434b6c6.0404121631.a14eaaa@posting.google.com>...
gans1973@rediffmail.com (ganesh) wrote in message
news:<510dfbbf.0404120732.6159c080@posting.google.com>...
hi,
Am not sure if these Q makes sense in the first place, but here goes.
1) The electron spin results in a magnetic field. So is the generalization
true: All half integer (1/2, 3/2, 5/2....) lead to magnetic field.
Similarly, is it true that none of the integer spins lead to
magnetic fields.
If so, is there any intuition behind it, or its just an observed fact,
and nothing more can be said about it??
Not all particles with half-integer spins have a magnetic field. Only
particles that have both charge and spin will possess magnetic fields.
Same goes for integer spin particles also. There are no restrictions
on spin quantum numbers leading to magnetic fields, so long as it's a
charged particle.
So, if we look at a neutron, a neutron gets deflected in a magnetic field.
But itself will not produce any magnetic field. I'm somehow trying to
understand this. Lets say we have a neutron and an electron. The electron
will exert a force on the neutron via its magnetic field (produced due to
the spin of the electron).
But the neutron will not and cannot exert any force(electric or magnetic)
on the electron. Does this mean when we talk of microscopic particles,
the third law of newton (action and reaction are equal and opp), is just
not applicable?? Or am I missing something??
ganesh
The reason a neutron gets deflected in a magnetic field is that it has
a non-zero magnetic dipole moment. In fact, this was a big clue
indicating that the neutron could not have been a truly fundamental
particle -- it has no net electric charge, yet it has a finite
magnetic dipole moment. Anything that has a magnetic dipole moment
will also have a magnetic field, since as far as we know dipoles are
their fundamental sources.
You make a good point in that a spinning particle doesn't necessarily
need to have a net electric charge in order to have a magnetic field.
So long as it has a charge distribution, such as a neutron, it can
have a magnetic field.
Did you know that electrons have a magnetic dipole moment?
And if the neutron has a magnetic field, it
must be able to exert magnetic forces, but not electric forces, on the
electron. Frankly, I've never really heard about any experimental
investigations into this effect, but it should occur.
Neutron beams are commonly used to study the magnetic structure of
crystals.
--
"What are the possibilities of small but movable machines? They may or
may not be useful, but they surely would be fun to make."
-- Richard P. Feynman, 1959
.
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|
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| User: "Igor" |
|
| Title: Re: some doubts on spin |
14 Apr 2004 09:04:12 AM |
|
|
(Gregory L. Hansen) wrote in message news:<c5i1k7$7gh$1@hood.uits.indiana.edu>...
In article <d434b6c6.0404131443.2597a2f3@posting.google.com>,
Igor <thoovler@excite.com> wrote:
gans1973@rediffmail.com (ganesh) wrote in message
news:<510dfbbf.0404130053.4a31e4c9@posting.google.com>...
thoovler@excite.com (Igor) wrote in message
news:<d434b6c6.0404121631.a14eaaa@posting.google.com>...
gans1973@rediffmail.com (ganesh) wrote in message
news:<510dfbbf.0404120732.6159c080@posting.google.com>...
hi,
Am not sure if these Q makes sense in the first place, but here goes.
1) The electron spin results in a magnetic field. So is the generalization
true: All half integer (1/2, 3/2, 5/2....) lead to magnetic field.
Similarly, is it true that none of the integer spins lead to
magnetic fields.
If so, is there any intuition behind it, or its just an observed fact,
and nothing more can be said about it??
Not all particles with half-integer spins have a magnetic field. Only
particles that have both charge and spin will possess magnetic fields.
Same goes for integer spin particles also. There are no restrictions
on spin quantum numbers leading to magnetic fields, so long as it's a
charged particle.
So, if we look at a neutron, a neutron gets deflected in a magnetic field.
But itself will not produce any magnetic field. I'm somehow trying to
understand this. Lets say we have a neutron and an electron. The electron
will exert a force on the neutron via its magnetic field (produced due to
the spin of the electron).
But the neutron will not and cannot exert any force(electric or magnetic)
on the electron. Does this mean when we talk of microscopic particles,
the third law of newton (action and reaction are equal and opp), is just
not applicable?? Or am I missing something??
ganesh
The reason a neutron gets deflected in a magnetic field is that it has
a non-zero magnetic dipole moment. In fact, this was a big clue
indicating that the neutron could not have been a truly fundamental
particle -- it has no net electric charge, yet it has a finite
magnetic dipole moment. Anything that has a magnetic dipole moment
will also have a magnetic field, since as far as we know dipoles are
their fundamental sources.
You make a good point in that a spinning particle doesn't necessarily
need to have a net electric charge in order to have a magnetic field.
So long as it has a charge distribution, such as a neutron, it can
have a magnetic field.
Did you know that electrons have a magnetic dipole moment?
Yeah, I believe I heard about that somewhere. Actually, that was the
whole point of the original post -- that charged particles with spin
will also have magnetic moments, and thus magnetic fields. That last
question was with regard to particles with no net charge still having
magnetic fields.
And if the neutron has a magnetic field, it
must be able to exert magnetic forces, but not electric forces, on the
electron. Frankly, I've never really heard about any experimental
investigations into this effect, but it should occur.
Neutron beams are commonly used to study the magnetic structure of
crystals.
That wasn't the point. I was wondering about how an electron would
respond to the magnetic field of a neutron, and commenting about how I
was not aware of any experimental research into this effect.
.
|
|
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| User: "Gregory L. Hansen" |
|
| Title: Re: some doubts on spin |
14 Apr 2004 09:30:03 AM |
|
|
In article <d434b6c6.0404140604.25c650c0@posting.google.com>,
Igor <thoovler@excite.com> wrote:
glhansen@steel.ucs.indiana.edu (Gregory L. Hansen) wrote in message
news:<c5i1k7$7gh$1@hood.uits.indiana.edu>...
And if the neutron has a magnetic field, it
must be able to exert magnetic forces, but not electric forces, on the
electron. Frankly, I've never really heard about any experimental
investigations into this effect, but it should occur.
Neutron beams are commonly used to study the magnetic structure of
crystals.
That wasn't the point. I was wondering about how an electron would
respond to the magnetic field of a neutron, and commenting about how I
was not aware of any experimental research into this effect.
I thought how a neutron would respond to the magnetic field of an electron
might be relevant to how an electron would respond to the magnetic field
of a neutron.
It would work into the structure factors of electrons scattered from
nuclei. It would give a correction for the spectrum of deuterium and
tritium, besides just correcting for the mass of the nucleus, if
spectroscopy were sensitive enough to see it. I don't know of specific
experiments.
--
"When the fool walks through the street, in his lack of understanding he
calls everything foolish." -- Ecclesiastes 10:3, New American Bible
.
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| User: "ganesh" |
|
| Title: Re: some doubts on spin |
15 Apr 2004 12:14:14 AM |
|
|
Thanks to Igor and others, I did get the clarifications.
Note to Socks:
Internet may be the worst place or the second worst place or whatever,
but is the only place for someone like me to interact with experts.
And yeah, it cant replace books, but it certainly is a supplement...
and I guess a v. essential one...as such interactions can correct/change
one's thought process....
ganesh
thoovler@excite.com (Igor) wrote in message news:<d434b6c6.0404131443.2597a2f3@posting.google.com>...
gans1973@rediffmail.com (ganesh) wrote in message news:<510dfbbf.0404130053.4a31e4c9@posting.google.com>...
thoovler@excite.com (Igor) wrote in message news:<d434b6c6.0404121631.a14eaaa@posting.google.com>...
gans1973@rediffmail.com (ganesh) wrote in message news:<510dfbbf.0404120732.6159c080@posting.google.com>...
hi,
Am not sure if these Q makes sense in the first place, but here goes.
1) The electron spin results in a magnetic field. So is the generalization
true: All half integer (1/2, 3/2, 5/2....) lead to magnetic field.
Similarly, is it true that none of the integer spins lead to magnetic fields.
If so, is there any intuition behind it, or its just an observed fact,
and nothing more can be said about it??
Not all particles with half-integer spins have a magnetic field. Only
particles that have both charge and spin will possess magnetic fields.
Same goes for integer spin particles also. There are no restrictions
on spin quantum numbers leading to magnetic fields, so long as it's a
charged particle.
So, if we look at a neutron, a neutron gets deflected in a magnetic field.
But itself will not produce any magnetic field. I'm somehow trying to
understand this. Lets say we have a neutron and an electron. The electron
will exert a force on the neutron via its magnetic field (produced due to
the spin of the electron).
But the neutron will not and cannot exert any force(electric or magnetic)
on the electron. Does this mean when we talk of microscopic particles,
the third law of newton (action and reaction are equal and opp), is just
not applicable?? Or am I missing something??
ganesh
The reason a neutron gets deflected in a magnetic field is that it has
a non-zero magnetic dipole moment. In fact, this was a big clue
indicating that the neutron could not have been a truly fundamental
particle -- it has no net electric charge, yet it has a finite
magnetic dipole moment. Anything that has a magnetic dipole moment
will also have a magnetic field, since as far as we know dipoles are
their fundamental sources.
You make a good point in that a spinning particle doesn't necessarily
need to have a net electric charge in order to have a magnetic field.
So long as it has a charge distribution, such as a neutron, it can
have a magnetic field. And if the neutron has a magnetic field, it
must be able to exert magnetic forces, but not electric forces, on the
electron. Frankly, I've never really heard about any experimental
investigations into this effect, but it should occur.
.
|
|
|
|
|
| User: "" |
|
| Title: Re: some doubts on spin |
13 Apr 2004 11:34:53 AM |
|
|
(ganesh) wrote in message news:<510dfbbf.0404130053.4a31e4c9@posting.google.com>...
[still more questions]
Seriously, the internet is probably the second worst place to try to
learn these things. (The worst is probably a bathroom at a bus station.)
You need to get yourself a couple good books on quantum mechanics
and such like, and read them pretty carefully. Get one that deals
with relativistic quantum mechanics for starters, at least as far
as the Dirac equation. Plus, to get any of the details of how this
works for nucleons, you will need to get into how composite particles
work for spin.
Socks
.
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| User: "Jon Bell" |
|
| Title: Re: some doubts on spin |
12 Apr 2004 11:22:37 AM |
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In article <510dfbbf.0404120732.6159c080@posting.google.com>,
ganesh <gans1973@rediffmail.com> wrote:
4) Does a neutrino have a zero rest mass or a non-zero rest mass?? I seem to
be comming across both.
Non-zero. This is a recent development; anything written more than a
couple of years ago is likely to be out of date.
Last week I heard a guy from CERN give a talk at USC about neutrino
physics, which focused mainly on neutrino oscillations. Between
observations on solar neutrinos, atmospheric neutrinos, and
accelerator-produced neutrinos, there's pretty clear evidence that
neutrino oscillations exist, and various experiments are zooming in on the
oscillation parameters. Current data imply that at least one type of
neutrino must have a mass (energy equivalent) of at least 0.03 eV (if I
remember the number correctly). Other kinds of experiments imply that it
cannot be greater than a few eV.
He talked about a coming era of "precision neutrino physics," which is
kind of mind-boggling to someone who wrote a dissertation over twenty
years ago, based on a few dozen neutrino events in a bubble chamber.
--
Jon Bell <jtbellm4h@presby.edu> Presbyterian College
Dept. of Physics and Computer Science Clinton, South Carolina USA
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| User: "" |
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| Title: Re: some doubts on spin |
13 Apr 2004 07:30:10 AM |
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In article <c5efod$3ip$1@jtbell.presby.edu>,
(Jon Bell) wrote:
<snip>
He talked about a coming era of "precision neutrino physics," which is
kind of mind-boggling to someone who wrote a dissertation over twenty
years ago, based on a few dozen neutrino events in a bubble chamber.
I feel the same way when I see a box smaller than a bread box
doing more than what our computers did and stored; and they
needed a gymnasium foot print. I was completely floored a few
weeks ago when I held, in my hand, something the size of a
ciagrette lighter and realized I could carry away dozens of my
software sets on that thing. I wasn't physically able to carry
one set back then.
/BAH
Subtract a hundred and four for e-mail.
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| User: "G=EMC^2 Glazier" |
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| Title: Re: some doubts on spin |
14 Apr 2004 09:51:21 AM |
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ganesh It would not be an electron if it had no spin. We have QM
giving its twist to classical spin. It states that particles have an
intrinsic amount of spin that is either a whole number or a half a whole
number(in multiples of the Planck's constant),and which never changes.
A spinning electron is a spinning cloud of photons. they spin at the
speed of "c" Half of all photons are virtual It is virtual phiotons
that create the magnetic field. They create action over distance. Sorry
if most of this is my thinking. t comes out of my "Spin is in theory"
Bert.
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