| Topic: |
Science > Philosophy |
| User: |
"darwinist" |
| Date: |
26 Oct 2006 09:57:35 PM |
| Object: |
When light "slows down" is it just taking a detour? |
For example, is its path still traveled at c, but altered by going
around or interacting with the atoms which are between its origin and
destination?
Does anything (at that scale) actually move slower than light-speed, or
is it just moving in a funny shape?
.
|
|
| User: "Bill Hobba" |
|
| Title: Re: When light "slows down" is it just taking a detour? |
27 Oct 2006 02:07:31 AM |
|
|
"darwinist" <darwinist@gmail.com> wrote in message
news:1161917855.496062.322270@k70g2000cwa.googlegroups.com...
For example, is its path still traveled at c, but altered by going
around or interacting with the atoms which are between its origin and
destination?
The situation you are describing is the realm of QFT. In the perturbation
approach it is absorbed then reemitted at c and that is what causes it to
slow down. But whether perturbation theory is fundamental or not is
anyone's guess.
Thanks
Bill
Does anything (at that scale) actually move slower than light-speed, or
is it just moving in a funny shape?
.
|
|
|
|
| User: "Wordsmith" |
|
| Title: Re: When light "slows down" is it just taking a detour? |
27 Oct 2006 12:26:25 AM |
|
|
On Oct 26, 8:57 pm, "darwinist" <darwin...@gmail.com> wrote:
For example, is its path still traveled at c, but altered by going
around or interacting with the atoms which are between its origin and
destination?
Does anything (at that scale) actually move slower than light-speed, or
is it just moving in a funny shape?
Stick a pencil in a glass of water. See how it looks bent? The water
slows down the light...a little bit.
W : )
.
|
|
|
|
| User: "Sue..." |
|
| Title: Re: When light "slows down" is it just taking a detour? |
27 Oct 2006 12:16:23 PM |
|
|
darwinist wrote:
For example, is its path still traveled at c, but altered by going
around or interacting with the atoms which are between its origin and
destination?
Does anything (at that scale) actually move slower than light-speed, or
is it just moving in a funny shape?
No... Light slows in proportion to the number of
*coupled* charges that have to be accelerated along a path.
<< There are no free charges or free currents in the medium.
There is also no bound charge density (since the medium is uniform),
and no magnetization current density (since the medium is
non-magnetic).
However, there is a polarization current due to the time-variation
of the induced dipole moment per unit volume. According to Eq. (859),
this current is given by... >>
<< Maxwell's equations for the propagation of electromagnetic waves
through a dielectric medium are the same as Maxwell's equations for
the propagation of waves through a vacuum (see Sect. 4.7), except that
,
where
(1146)
is called the refractive index of the medium in question. Hence, we
conclude that electromagnetic waves propagate through a dielectric
medium slower than through a vacuum by a factor (assuming, of
course, that ). This conclusion (which was reached long before
Maxwell's
equations were invented) is the basis of all geometric optics involving
refraction. >>
http://farside.ph.utexas.edu/teaching/em/lectures/node98.html
http://physics.nist.gov/cuu/Images/alphaeq.gif
http://physics.nist.gov/cuu/Constants/alpha.html
It is not much different than the mass and tension of a
musical instrument string.
http://hyperphysics.phy-astr.gsu.edu/Hbase/waves/string.html
Sue...
.
|
|
|
|
| User: "RP" |
|
| Title: Re: When light "slows down" is it just taking a detour? |
27 Oct 2006 09:52:38 PM |
|
|
darwinist wrote:
For example, is its path still traveled at c, but altered by going
around or interacting with the atoms which are between its origin and
destination?
Does anything (at that scale) actually move slower than light-speed, or
is it just moving in a funny shape?
Nothing is moving other than the charges involved. Light is the delayed
interaction between charged particles. When a source charged jiggles
it causes other charges to jiggle at a time r/c later, where r is the
radial displacement in all directions from the charge. Since there are
many charged particles in an optical media, these jiggle in the form of
a wave front of radius r intially, but via feedback in an optical media
the curvature of the wave front is altered. Each of the charges within
the media, when recoiling from their interaction with the source
charge, in cause other electrons to jiggle, again at a time r'/c later.
If you follow the light cone back from the detector to all of these
other electrons, then the detector sees a field that is a superposition
of all of the fields of those jiggling electrons rather than just the
field of the source electron. There is feedback generated within the
optical media, because the waves are spherical, i.e. propagate both
forward and backward. The backward propagation is what we perceive as
"reflection", and the forward propagation is what we perceive as an
optically delayed and/or otherwise altered signal. The detector is
simply looking back into time and responding to the field that it sees
surrounding it in each instant. This is also the field that we "see",
since, as it were, our sight is generated by the jiggling of charges in
our retinas.
Feynman's sum over approach is simply a matter of summing up the
interference paths generated during this purely classical process. The
signal literally takes all possible paths, but sums to zero along some
of them via superposition of all of the secondary radiation and the
source radiation. Light is just short wavelength em waves, and must
obey the same laws as all other em waves. One would hardly interpret
ordinary radio transmissions and thier interference patterns in terms
of probability amplitudes. Any radio engineering handbook will simply
calculate the wave interference patterns, which are not considered as
probability waves, but as real waves that are actually propagating
along those many paths.
One photon being absorbed and reemitted simultaneously by many
electrons in an optical media is a statement that stands in stark
contrast to the idea that atomic orbital electrons can only absorb and
emit energy in discrete amounts. Thus Feynman's description is
contradictory to the accepted theory of photoelectron emission. Had
QED been formulated by a lesser figure, such as by those regarded as
cranks here, then no doubt it would have been immediately rejected as a
crackpot theory. Even in reading through Feynman's writings, and the
writings of those propounding the theory, it has all the air of the
many truly crackpot notions presented here by cranks. The difference
lies only in this, the foundational concepts of QED were patched, and
skewered, and then patched again and again until the idea of photons
has by now been forcibly made to fit the data. That isn't science, it's
just plain old Ptolemaic propaganda.
These guys apparently don't even understand the source of magnetism,
which was expounded fairly well by Weber quite some time ago. The
resolution to all of the conceptual difficulties encountered in the
so-called acceptable theories lies in the conjoining of Weber's and
Ampere's electrodynamics with Lorentz invariance. Though the original's
weren't precisely correct, well then neither was photon theory in the
beginning, so that's all I have to say on that subject.
Richard Perry
.
|
|
|
| User: "RP" |
|
| Title: Re: When light "slows down" is it just taking a detour? |
27 Oct 2006 09:59:05 PM |
|
|
RP wrote:
darwinist wrote:
For example, is its path still traveled at c, but altered by going
around or interacting with the atoms which are between its origin and
destination?
Does anything (at that scale) actually move slower than light-speed, or
is it just moving in a funny shape?
A few typos corrected for clarity's sake.
Nothing is moving other than the charges involved. Light is the delayed
interaction between charged particles. When a source charge jiggles
it causes other charges to jiggle at a time r/c later, where r is the
radial displacement in all directions from the charge. Since there are
many charged particles within an optical media, these jiggle in the form of
a wave front of radius r intially, but via feedback the curvature of the wave front is altered.
Each of the charges within
the media, when recoiling from their interaction with the source
charge, in turn cause other electrons to jiggle, again at a time r'/c later, where r' is the radial
displacement from the recoiling charge in the media.
If you follow the light cone back from the detector to all of these
other electrons, then the detector will "see" a field that is a superposition
of all of the fields of those jiggling electrons rather than just the
field of the source electron. There is feedback generated within the
optical media, because the waves are spherical, i.e. propagate both
forward and backward. The backward propagation is what we perceive as
"reflection", and the forward propagation is what we perceive as an
optically delayed and/or otherwise altered signal. The detector is
simply looking back into time and responding to the field that it sees
surrounding it in each instant. This is also the field that we "see",
since, as it were, our sight is generated by the jiggling of charges in
our retinas.
Feynman's sum over approach is simply a matter of summing up the
interference paths generated during this purely classical process. The
signal literally takes all possible paths, but sums to zero along some
of them via superposition of all of the secondary radiation and the
source radiation. Light is just short wavelength em waves, and must
obey the same laws as all other em waves. One would hardly interpret
ordinary radio transmissions and thier interference patterns in terms
of probability amplitudes. Any radio engineering handbook will simply
calculate the wave interference patterns, which are not considered as
probability waves, but as real waves that are actually propagating
along those many paths.
One photon being absorbed and reemitted simultaneously by many
electrons in an optical media is a statement that stands in stark
contrast to the idea that atomic orbital electrons can only absorb and
emit energy in discrete amounts. Thus Feynman's description is
contradictory to the accepted theory of photoelectron emission. Had
QED been formulated by a lesser figure, such as by those regarded as
cranks here, then no doubt it would have been immediately rejected as a
crackpot theory. Even in reading through Feynman's writings, and the
writings of those propounding the theory, it has all the air of the
many truly crackpot notions presented here by cranks. The difference
lies only in this, the foundational concepts of QED were patched, and
skewered, and then patched again and again until the idea of photons
has by now been forcibly made to fit the data. That isn't science, it's
just plain old Ptolemaic propaganda.
These guys apparently don't even understand the source of magnetism,
which was expounded fairly well by Weber quite some time ago. The
resolution to all of the conceptual difficulties encountered in the
so-called acceptable theories lies in the conjoining of Weber's and
Ampere's electrodynamics with Lorentz invariance. Though the original's
weren't precisely correct, well then neither was photon theory in the
beginning, so that's all I have to say on that subject.
Bohm is boss!
Richard Perry
.
|
|
|
|
| User: "RP" |
|
| Title: Re: When light "slows down" is it just taking a detour? |
27 Oct 2006 09:59:18 PM |
|
|
RP wrote:
darwinist wrote:
For example, is its path still traveled at c, but altered by going
around or interacting with the atoms which are between its origin and
destination?
Does anything (at that scale) actually move slower than light-speed, or
is it just moving in a funny shape?
A few typos corrected for clarity's sake.
Nothing is moving other than the charges involved. Light is the delayed
interaction between charged particles. When a source charge jiggles
it causes other charges to jiggle at a time r/c later, where r is the
radial displacement in all directions from the charge. Since there are
many charged particles within an optical media, these jiggle in the form of
a wave front of radius r intially, but via feedback the curvature of the wave front is altered.
Each of the charges within
the media, when recoiling from their interaction with the source
charge, in turn cause other electrons to jiggle, again at a time r'/c later, where r' is the radial
displacement from the recoiling charge in the media.
If you follow the light cone back from the detector to all of these
other electrons, then the detector will "see" a field that is a superposition
of all of the fields of those jiggling electrons rather than just the
field of the source electron. There is feedback generated within the
optical media, because the waves are spherical, i.e. propagate both
forward and backward. The backward propagation is what we perceive as
"reflection", and the forward propagation is what we perceive as an
optically delayed and/or otherwise altered signal. The detector is
simply looking back into time and responding to the field that it sees
surrounding it in each instant. This is also the field that we "see",
since, as it were, our sight is generated by the jiggling of charges in
our retinas.
Feynman's sum over approach is simply a matter of summing up the
interference paths generated during this purely classical process. The
signal literally takes all possible paths, but sums to zero along some
of them via superposition of all of the secondary radiation and the
source radiation. Light is just short wavelength em waves, and must
obey the same laws as all other em waves. One would hardly interpret
ordinary radio transmissions and thier interference patterns in terms
of probability amplitudes. Any radio engineering handbook will simply
calculate the wave interference patterns, which are not considered as
probability waves, but as real waves that are actually propagating
along those many paths.
One photon being absorbed and reemitted simultaneously by many
electrons in an optical media is a statement that stands in stark
contrast to the idea that atomic orbital electrons can only absorb and
emit energy in discrete amounts. Thus Feynman's description is
contradictory to the accepted theory of photoelectron emission. Had
QED been formulated by a lesser figure, such as by those regarded as
cranks here, then no doubt it would have been immediately rejected as a
crackpot theory. Even in reading through Feynman's writings, and the
writings of those propounding the theory, it has all the air of the
many truly crackpot notions presented here by cranks. The difference
lies only in this, the foundational concepts of QED were patched, and
skewered, and then patched again and again until the idea of photons
has by now been forcibly made to fit the data. That isn't science, it's
just plain old Ptolemaic propaganda.
These guys apparently don't even understand the source of magnetism,
which was expounded fairly well by Weber quite some time ago. The
resolution to all of the conceptual difficulties encountered in the
so-called acceptable theories lies in the conjoining of Weber's and
Ampere's electrodynamics with Lorentz invariance. Though the original's
weren't precisely correct, well then neither was photon theory in the
beginning, so that's all I have to say on that subject.
Bohm is boss!
Richard Perry
.
|
|
|
| User: "FrediFizzx" |
|
| Title: Re: When light "slows down" is it just taking a detour? |
27 Oct 2006 11:55:37 PM |
|
|
"RP" <no_mail_no_spam@yahoo.com> wrote in message
news:1162004358.028211.129430@b28g2000cwb.googlegroups.com...
RP wrote:
darwinist wrote:
For example, is its path still traveled at c, but altered by going
around or interacting with the atoms which are between its origin
and
destination?
Does anything (at that scale) actually move slower than
light-speed, or
is it just moving in a funny shape?
A few typos corrected for clarity's sake.
Nothing is moving other than the charges involved. Light is the
delayed
interaction between charged particles. When a source charge jiggles
it causes other charges to jiggle at a time r/c later, where r is the
radial displacement in all directions from the charge. Since there
are
many charged particles within an optical media, these jiggle in the
form of
a wave front of radius r intially, but via feedback the curvature of
the wave front is altered.
Each of the charges within
the media, when recoiling from their interaction with the source
charge, in turn cause other electrons to jiggle, again at a time r'/c
later, where r' is the radial
displacement from the recoiling charge in the media.
If you follow the light cone back from the detector to all of these
other electrons, then the detector will "see" a field that is a
superposition
of all of the fields of those jiggling electrons rather than just the
field of the source electron. There is feedback generated within the
optical media, because the waves are spherical, i.e. propagate both
forward and backward. The backward propagation is what we perceive as
"reflection", and the forward propagation is what we perceive as an
optically delayed and/or otherwise altered signal. The detector is
simply looking back into time and responding to the field that it
sees
surrounding it in each instant. This is also the field that we "see",
since, as it were, our sight is generated by the jiggling of charges
in
our retinas.
Feynman's sum over approach is simply a matter of summing up the
interference paths generated during this purely classical process.
The
signal literally takes all possible paths, but sums to zero along
some
of them via superposition of all of the secondary radiation and the
source radiation. Light is just short wavelength em waves, and must
obey the same laws as all other em waves. One would hardly interpret
ordinary radio transmissions and thier interference patterns in terms
of probability amplitudes. Any radio engineering handbook will simply
calculate the wave interference patterns, which are not considered as
probability waves, but as real waves that are actually propagating
along those many paths.
You are doing OK up to this point. It just happens to be fortunate that
the probability waves of EM radiation and the classical waves have the
same spatial pattern.
One photon being absorbed and reemitted simultaneously by many
electrons in an optical media is a statement that stands in stark
contrast to the idea that atomic orbital electrons can only absorb
and
emit energy in discrete amounts. Thus Feynman's description is
contradictory to the accepted theory of photoelectron emission.
Now you are getting hinky on us. ;-) What is up with this "One photon
being absorbed and reemitted simultaneously by many electrons..."? Do
you have a reference for that? Are you leaving something out here?
Had
QED been formulated by a lesser figure, such as by those regarded as
cranks here, then no doubt it would have been immediately rejected as
a
crackpot theory. Even in reading through Feynman's writings, and the
writings of those propounding the theory, it has all the air of the
many truly crackpot notions presented here by cranks. The difference
lies only in this, the foundational concepts of QED were patched, and
skewered, and then patched again and again until the idea of photons
has by now been forcibly made to fit the data. That isn't science,
it's
just plain old Ptolemaic propaganda.
Feynman did not formulate QED; he merely helped put some finishing
touches on it to make it work better. You can blame Dirac for QED. ;-)
And many others who helped along the way even starting with Einstein. I
don't really recall any "patches" done to it other than perhaps the
concept of renormalization and regularization. But most of that had to
do with fermions and not photons. The concept of photons even worked
pretty good back in the 1920's before QED.
These guys apparently don't even understand the source of magnetism,
which was expounded fairly well by Weber quite some time ago. The
resolution to all of the conceptual difficulties encountered in the
so-called acceptable theories lies in the conjoining of Weber's and
Ampere's electrodynamics with Lorentz invariance. Though the
original's
weren't precisely correct, well then neither was photon theory in the
beginning, so that's all I have to say on that subject.
Ah, the source of magnetism. Actually, Maxwell had a pretty good handle
on it also in 1861 with "On Physical Lines of Force",
http://www.vacuum-physics.com/Maxwell/maxwell_oplf.pdf
But then stepped away from it. That paper could probably be called a
precursor to quantum field theory.
Bohm is boss!
Nah! Quantum Vacuum Charge rules, baby!
FrediFizzx
Quantum Vacuum Charge papers;
http://www.vacuum-physics.com/QVC/quantum_vacuum_charge.pdf
or postscript
http://www.vacuum-physics.com/QVC/quantum_vacuum_charge.ps
http://www.arxiv.org/abs/physics/0601110
http://www.vacuum-physics.com
.
|
|
|
| User: "RP" |
|
| Title: Re: When light "slows down" is it just taking a detour? |
28 Oct 2006 07:23:11 AM |
|
|
FrediFizzx wrote:
"RP" <no_mail_no_spam@yahoo.com> wrote in message
news:1162004358.028211.129430@b28g2000cwb.googlegroups.com...
RP wrote:
darwinist wrote:
For example, is its path still traveled at c, but altered by going
around or interacting with the atoms which are between its origin
and
destination?
Does anything (at that scale) actually move slower than
light-speed, or
is it just moving in a funny shape?
A few typos corrected for clarity's sake.
Nothing is moving other than the charges involved. Light is the
delayed
interaction between charged particles. When a source charge jiggles
it causes other charges to jiggle at a time r/c later, where r is the
radial displacement in all directions from the charge. Since there
are
many charged particles within an optical media, these jiggle in the
form of
a wave front of radius r intially, but via feedback the curvature of
the wave front is altered.
Each of the charges within
the media, when recoiling from their interaction with the source
charge, in turn cause other electrons to jiggle, again at a time r'/c
later, where r' is the radial
displacement from the recoiling charge in the media.
If you follow the light cone back from the detector to all of these
other electrons, then the detector will "see" a field that is a
superposition
of all of the fields of those jiggling electrons rather than just the
field of the source electron. There is feedback generated within the
optical media, because the waves are spherical, i.e. propagate both
forward and backward. The backward propagation is what we perceive as
"reflection", and the forward propagation is what we perceive as an
optically delayed and/or otherwise altered signal. The detector is
simply looking back into time and responding to the field that it
sees
surrounding it in each instant. This is also the field that we "see",
since, as it were, our sight is generated by the jiggling of charges
in
our retinas.
Feynman's sum over approach is simply a matter of summing up the
interference paths generated during this purely classical process.
The
signal literally takes all possible paths, but sums to zero along
some
of them via superposition of all of the secondary radiation and the
source radiation. Light is just short wavelength em waves, and must
obey the same laws as all other em waves. One would hardly interpret
ordinary radio transmissions and thier interference patterns in terms
of probability amplitudes. Any radio engineering handbook will simply
calculate the wave interference patterns, which are not considered as
probability waves, but as real waves that are actually propagating
along those many paths.
You are doing OK up to this point. It just happens to be fortunate that
the probability waves of EM radiation and the classical waves have the
same spatial pattern.
One photon being absorbed and reemitted simultaneously by many
electrons in an optical media is a statement that stands in stark
contrast to the idea that atomic orbital electrons can only absorb
and
emit energy in discrete amounts. Thus Feynman's description is
contradictory to the accepted theory of photoelectron emission.
Now you are getting hinky on us. ;-) What is up with this "One photon
being absorbed and reemitted simultaneously by many electrons..."? Do
you have a reference for that? Are you leaving something out here?
Had
QED been formulated by a lesser figure, such as by those regarded as
cranks here, then no doubt it would have been immediately rejected as
a
crackpot theory. Even in reading through Feynman's writings, and the
writings of those propounding the theory, it has all the air of the
many truly crackpot notions presented here by cranks. The difference
lies only in this, the foundational concepts of QED were patched, and
skewered, and then patched again and again until the idea of photons
has by now been forcibly made to fit the data. That isn't science,
it's
just plain old Ptolemaic propaganda.
Feynman did not formulate QED; he merely helped put some finishing
touches on it to make it work better. You can blame Dirac for QED. ;-)
And many others who helped along the way even starting with Einstein. I
don't really recall any "patches" done to it other than perhaps the
concept of renormalization and regularization. But most of that had to
do with fermions and not photons. The concept of photons even worked
pretty good back in the 1920's before QED.
These guys apparently don't even understand the source of magnetism,
which was expounded fairly well by Weber quite some time ago. The
resolution to all of the conceptual difficulties encountered in the
so-called acceptable theories lies in the conjoining of Weber's and
Ampere's electrodynamics with Lorentz invariance. Though the
original's
weren't precisely correct, well then neither was photon theory in the
beginning, so that's all I have to say on that subject.
Ah, the source of magnetism. Actually, Maxwell had a pretty good handle
on it also in 1861 with "On Physical Lines of Force",
http://www.vacuum-physics.com/Maxwell/maxwell_oplf.pdf
If that's a pretty good handle, then a lot of cranks who have posted
here deserve apologies.
Richard Perry
But then stepped away from it. That paper could probably be called a
precursor to quantum field theory.
Bohm is boss!
Nah! Quantum Vacuum Charge rules, baby!
FrediFizzx
Quantum Vacuum Charge papers;
http://www.vacuum-physics.com/QVC/quantum_vacuum_charge.pdf
or postscript
http://www.vacuum-physics.com/QVC/quantum_vacuum_charge.ps
http://www.arxiv.org/abs/physics/0601110
http://www.vacuum-physics.com
.
|
|
|
|
|
|
|
| User: "Tom Roberts" |
|
| Title: Re: When light "slows down" is it just taking a detour? |
27 Oct 2006 08:58:37 AM |
|
|
darwinist wrote:
For example, is its path still traveled at c, but altered by going
around or interacting with the atoms which are between its origin and
destination?
Does anything (at that scale) actually move slower than light-speed, or
is it just moving in a funny shape?
In QED there are basically two ways to interpret this:
A) The individual photons of the light beam get repeatedly
absorbed and re-radiated by the charged particles in the
material.
B) The individual photons of the light "seek out" all possible
paths through spacetime, and while doing this the charged
particles in the material alter their phases; the overall
speed of the wavefront is reduced from c due to the way the
phases of these different paths interfere with each other.
(A) is essentially the perturbation approach, in which one writes down
specific Feynman diagrams for which a photon is absorbed and
re-radiated, and in which there is an explicit sum over all charged
particles in the universe.
(B) is essentially the path integral itself, considered directly.
These are different interpretations, but computations based on them
obtain the same answer.
There is another description that is really (A), but differs in the
order in which the different diagrams are summed:
C) By summing the diagrams in an appropriate order, one can
compute the process by drawing the lowest-order diagram
with "dressed" electrons and photons (higher-order diagrams
combine to alter the effective masses of electrons and
photons, called "dressing"). Inside the material the dressed
photons have a non-zero effective mass, and thus travel
slower than c; in vacuum the dressing has no effect and the
photons travel at c.
So the answers to your questions really depend upon which interpretation
of QED one selects. (A) is the approach generally used by particle
physicists; (B) is useful only for qualitative descriptions; (C) is
generally used by condensed matter physicists -- they have developed
techniques to compute the effects of dressing without actually summing
the infinite series of diagrams. The difference is in whether or not
higher-order diagrams are important (for high-energy gammas and
electrons in particle experiments they are not, but for low-energy
collective excitations of materials they are).
Tom Roberts
.
|
|
|
|
|
Related Articles |
|
|
