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Tags scientific reasoning , relativity , mass energy equivalence

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Old 10th June 2008, 09:19 AM   #41
ponderingturtle
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Originally Posted by Reality Check View Post
There is no such thing as "restmass". A particle with mass has a "rest mass". A particle with mass that is moving has a relativistic mass that is its rest mass multiplied by the Lorentz factor.
This statement is dependant ont he definition of mass being rest mass and not relativistic mass.

Yes that is what is currently popular, but really as long as you are being clear as to what you define mass as being, either can be viewed as equaly true, unless you have some experiment to show that reletivistic mass doesn't exist(seems unlikely given that they are just different formulations of the same equations and as such you are not going to get a difference in predictions)
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Old 10th June 2008, 09:47 AM   #42
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Originally Posted by wogoga View Post
Zosima's original statement:
Mass-Energy equivalence means that even though a photon is massless it has energy
If we replace mass with restmass we get:
Restmass-Energy equivalence means that even though a photon has no restmass it has energy
This version is obviously wrong, because there is no equivalence between restmass and energy. Equivalence only reigns between (relativistic) mass and energy. The alternative
Equivalence between (relativistic) mass and energy means that even though a photon has no restmass it has energy
doesn't make a lot of sense, because of the confusion between two different mass-concepts (mass and restmass).
I agree with most of what you're saying about Zosima's statement, but it's not an inconsistency of modern physics. He just chose his words poorly. He admitted that himself. I don't see what the big deal is.

All particles satisfy \footnotesize $E^2=\vec p^2c^2$+m^2c^4. This means that massive particles have energy even in a coordinate system where their velocity is zero, and that this energy comes from the particle's mass.

When m>0, we can express the right-hand side as \footnotesize (\gamma m)^2c^4. The quantity in parentheses is often called the "relativistic mass". So for massive particles, the equation expresses an equivalence between "relativistic mass" and energy.

I don't have a problem with that. What I don't like is when the equation is interpreted as an equivalence between relativistic mass and energy for all particles. The only way to interpret it that way is to define the relativistic mass m (using your trick with the colors) of a particle by setting the left-hand side equal to m2c4. This makes the equivalence between relativistic mass and energy true by definition, so it doesn't really say anything about the physics.

As you can see, there are several things that can be described as an equivalence between mass and energy: The equivalence between mass and energy in the rest frame. The equivalence between relativistic mass and energy, for massive particles. The equivalence between relativistic mass and energy, for massless particles. The first two describe properties of our universe. The last one doesn't really say anything.

Note also that by setting m=0, we see that the equation doesn't prevent massless particles from having energy or momentum.
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Old 10th June 2008, 08:29 PM   #43
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Try this equation P2 = EKINETIC*(Mrel + Mrest) an algebraic extension of the one equation that I have mostly been confronted with.

Sorry I do not know how to use the formatting to make it look significant.

I would appreciate any input on the formatting or the physics.
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Old 10th June 2008, 09:40 PM   #44
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Jesus Christ. My original comment was a throw-away comment about the flaws in a model that was completely awful. Mainly to say that it did not account for the behavior of objects with respect to relativity. It was terribly imprecise, but despite what Wogoga may claim, I am in no way a spokes-person for the theory of general relativity. My incompetence at explaining physics in no way impeaches the theory of general relativity, nor does Wogoga's capacity to misunderstand and/or misconstrue my words.

If I were going to phrase my statement precisely. I would probably say:
"Even though a photon has no rest mass it does contribute to the stress-energy tensor of general relativity and thus can be expected to exert a tiny gravitational force on the objects around it."

This is true. But honestly the mathematics is complex enough that any attempt to explain it is going to involve a certain amount of compromise. If you are truly interested I would recommend you order one of the many books available on the topic from amazon.

So this property of photons is a consequence of the theory of general relativity, a theory which has been far better tested than the soul juice theory of reincarnation.(Which you have no trouble believing, Wogoga)
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Old 10th June 2008, 10:46 PM   #45
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Old 11th June 2008, 06:54 AM   #46
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Originally Posted by The Man View Post
Try this equation P2 = EKINETIC*(Mrel + Mrest) an algebraic extension of the one equation that I have mostly been confronted with.

Sorry I do not know how to use the formatting to make it look significant.

I would appreciate any input on the formatting or the physics.
Your equation says that the kinetic energy is

$\frac{\vec p^2}{(\gamma+1)m}$

If my algebra is correct (I did it very fast without double-checking anything) this can be simplified to \footnotesize\gamma m-m. So your equation expresses the same thing as \footnotesize$E^2=\vec p^2+m^2.

(I'm using units such that c=1).
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Old 12th June 2008, 09:20 AM   #47
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Originally Posted by zosima View Post
... soul juice ...
  • Soul juice
is a contradictio in terminis in the same way as
  • the quadrangle-area of a triangle (i.e. the area of a triangle with four angles and four straight sides)
  • the rest-mass of a photon (i.e. the mass of photon at rest).
Juice is a paragon (an ideal incarnation) of divisibility or continuous changeability in quantity. Soul on the contrary is an embodiment of indivisibility and discreteness (see also: The relationship between quanta and psychons).

Interestingly, according to QED, photons in a transparent medium propagate always at c, and are regularly absorbed and reemitted so that a propagation speed of c/n is the result (n is the refractive index). There has been an interesting discussion on this aspect of QED on sci.physics.research: The speed of a photon. On my opinion see: Was QED intended as a joke?

Cheers, Wolfgang

A modern ('skeptic') variant of dogmatic belief: "the basic principles of physics are exactly what scientists say they are"
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Old 12th June 2008, 09:54 AM   #48
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Yup. The most precisely tested and verified theory in the history of physics is just a big joke.
So could you explain to me how Huygens explains, I dunno, Bose-Einstein condensate?
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Old 12th June 2008, 03:21 PM   #49
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Originally Posted by wogoga View Post
...snipped woo...
Interestingly, according to QED, photons in a transparent medium propagate always at c, and are regularly absorbed and reemitted so that a propagation speed of c/n is the result (n is the refractive index). There has been an interesting discussion on this aspect of QED on sci.physics.research: The speed of a photon. On my opinion see: Was QED intended as a joke?
Cheers, Wolfgang
You have it wrong. You do not really need QED to understand this.
Special Relativity that states that photons always travel at the speed of light in a vacuum. Matter (your "transparent medium") is mostly vacuum and photons travel at c in that vacuum. But photons are absorbed and emitted by atoms. This takes time and slows the measured speed of the photons.

P.S. "reemitted" suggests that the same photon that was absorbed is emitted. This is not correct. It is a different photon or even multiple photons, e.g. an electron absorbs a photon with a certain energy and ends up in an energy state that can decay via intermediate energy states back to the original energy state. Each decay emits a photon.

Quantum electrodynamics is definitely not a joke. It is the among the most precisely experimentally verified scientific theories in physics.



Your posted opinion is nonsense. A couple of points shows this:
  • QED does not say that photons always travel at c. Special Relativity states that photons that are not interacting with anything (in a vacuum) always travel at c. When the absorption and emission by atoms is added then the effective speed of photons is changed . This is where QED comes in.
  • The path-integral method of QED is not essentially the same as Huygens principle. The path-integral method integrates over all possible paths and is a quantum theory. Huygens principle adds up the waves from each point of an advancing wave front and is a classical theory.

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Old 12th June 2008, 03:21 PM   #50
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Originally Posted by Fredrik View Post
Your equation says that the kinetic energy is

$\frac{\vec p^2}{(\gamma+1)m}$

If my algebra is correct (I did it very fast without double-checking anything) this can be simplified to \footnotesize\gamma m-m. So your equation expresses the same thing as \footnotesize$E^2=\vec p^2+m^2.

(I'm using units such that c=1).

Spot on, Fredrik, on all points, as usual, and your algebra is non the worse for ware, but what this form of the equation can do is give us a way to explore the differences and similarities of relativistic and rest mass and perhaps some of the physics involved. For a photon, rest mass equals zero, so the proportion of momentum squared over kinetic energy equals its relativistic mass. Both momentum and kinetic energy are well understood, momentum a force times the time that force is applied and kinetic energy a force times the distance that forces is applied. Now the only time and distance that we can ascribe to a photon are its cyclic period and its wavelength. The resulting force that you can calculate from this relationship does not represent any real force applied to a traveling photon ( as I mentioned before) but does represent the maximum force that photon can apply to anything it interacts with, within the constraints of its cyclic period and its wavelength.

Although we can certainly conduct experiments that demonstrate a lack of rest mass (as in the case of the photon) we can conduct no experiments that demonstrate a lack of relativistic mass since even in a co-moving reference frame relativistic mass is just equal to rest mass. If we want to consider a reference frame co-moving with a photon we then loose all ability to perform any experiments.

If we consider an electron having rest mass but no discernable spatial extent at rest (as far as we can currently detect) other then its Compton wavelength, the same considerations apply. If we consider a proton or neutron with rest mass and a discernable spatial extent at rest (other then their Compton wavelengths) again the same consideration applies to those Compton spatial and temporal extents. Although we do now have something different in that discernable rest spatial extent (other then Compton wavelength) and its relationship to relativistic mass in a co-moving reference frame. Let’s remember that a co-moving reference frame is still a relativistic frame, just one with 0 relative velocity. That difference, in the non-Compton spatial extent, also provides us with a density related to the stress energy tensor from which we can calculate the frame invariant curvature of spacetime. A critical difference, no doubt, but in this aspect the force that we might calculate form that non Compton (or perhaps Compton as it is also frame invariant) spatial extent is actually (or apparently) applied to the curving of spacetime and/or the bodies within that curved spacetime, much like the photonic calculated force can be applied, in interactions only, and in this case an (considered resting) interaction with spacetime. From this consideration, it seems there are more similarities between rest mass and relativistic mass then there are differences.
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Old 15th June 2008, 07:47 AM   #51
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Originally Posted by Reality Check View Post
...
You do not really need QED to understand this. ... QED does not say that photons always travel at c. Special Relativity states that photons that are not interacting with anything (in a vacuum) always travel at c. When the absorption and emission by atoms is added then the effective speed of photons is changed. This is where QED comes in.
The attempt to attribute the explanation of the photon speed in transparent materials by absorption and emission to Special Relativity must be considered deliberate disinformation. Special Relativity is in this respect based on Maxwell's theory and Maxwell's theory explains different propagation speeds of electromagnetic waves by different permittivity and permeability values.

By claiming that "the light has an amplitude to go faster or slower than the speed c, but these amplitudes cancel each other out over long distances" (QED, p89-90), Richard Feynman somehow repeated the error of Niels Bohr (BKS theory), who had opposed the assumption of orderliness in emission and absorption processes of electromagnetic wave quanta by denying conservation of momentum and energy in single events. Both Bohr and Feynman were scientists in the theological tradition, preferring impressive counter-intuitive explanations to unprejudiced realistic ones.
P.S. "reemitted" suggests that the same photon that was absorbed is emitted. This is not correct.
Whether we consider the reemitted photon the same or a different photon, is irrelevant. Relevant however is that the reemitted photon must have exactly the same energy and momentum as the absorbed photon.
It is a different photon or even multiple photons, e.g. an electron absorbs a photon with a certain energy and ends up in an energy state that can decay via intermediate energy states back to the original energy state. Each decay emits a photon.
You confuse the extremely regular behaviour of light in optical lenses with scattering of photons e.g. in the atmosphere, where momentum and energy of photons actually are changed.

If continuous absorption and reemission were a genuinely physical explanation of the reduced speed in transparent media, then it would be possible to answer such questions as: How often (on average) is a 450-nm-photon absorbed and reemitted when traversing 1 cm of diamond?

By the way, in principle it is possible to label each atom of a given diamond with a unique number. If photons traversing this diamond actually were more than half of the time (n_diamond > 2) at rest (i.e. transformed into energy and momentum of carbon atoms), then it would in principle be possible to determine the path of a photon by enumerating the label-numbers of the atoms where the photon rested.

Yet on the other hand, QED makes the absurd claim that photons somehow use all possible paths.

Cheers, Wolfgang

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Old 15th June 2008, 08:15 AM   #52
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Originally Posted by wogoga View Post
You do not really need QED to understand this. ... QED does not say that photons always travel at c. Special Relativity states that photons that are not interacting with anything (in a vacuum) always travel at c. When the absorption and emission by atoms is added then the effective speed of photons is changed. This is where QED comes in.
The attempt to attribute the explanation of the photon speed in transparent materials by absorption and emission to Special Relativity must be considered deliberate disinformation. Special Relativity is in this respect based on Maxwell's theory and Maxwell's theory explains different propagation speeds of electromagnetic waves by different permittivity and permeability values.
You really do not understand Special Relativity or QED. SR is not based on Maxwell's equations which are for electromagnetic fields. SR applies to all things in motion and not only light.

Originally Posted by wogoga View Post
By claiming that "the light has an amplitude to go faster or slower than the speed c, but these amplitudes cancel each other out over long distances" (QED, p89-90), Richard Feynman somehow repeated the error of Niels Bohr (BKS theory), who had opposed the assumption of orderliness in emission and absorption processes of electromagnetic wave quanta by denying conservation of momentum and energy in single events. Both Bohr and Feynman were scientists in the theological tradition, preferring impressive counter-intuitive explanations to unprejudiced realistic ones.
Both Bohr and Feynman were scientists in the scientific sense - proposing theories on the evidence, making falsifiable predictions and only accepting their theories if the predictions were tested and found true.

I do not have the book so the quote may be correct and in context. But in QED it is the phases that cancel out or reinforce not the amplitudes.

Originally Posted by wogoga View Post
P.S. "reemitted" suggests that the same photon that was absorbed is emitted. This is not correct.
Whether we consider the reemitted photon the same or a different photon, is irrelevant. Relevant however is that the reemitted photon must have exactly the same energy and momentum as the absorbed photon.
It is a different photon or even multiple photons, e.g. an electron absorbs a photon with a certain energy and ends up in an energy state that can decay via intermediate energy states back to the original energy state. Each decay emits a photon.
You confuse the extremely regular behaviour of light in optical lenses with scattering of photons e.g. in the atmosphere, where momentum and energy of photons actually are changed.
The momentum and energy of photons is not changed when multiple photons are emitted.

If continuous absorption and reemission were a genuinely physical explanation of the reduced speed in transparent media, then it would be possible to answer such questions as: How often (on average) is a 450-nm-photon absorbed and reemitted when traversing 1 cm of diamond?

By the way, in principle it is possible to label each atom of a given diamond with a unique number. If photons traversing this diamond actually were more than half of the time (n_diamond > 2) at rest (i.e. transformed into energy and momentum of carbon atoms), then it would in principle be possible to determine the path of a photon by enumerating the label-numbers of the atoms where the photon rested.

Yet on the other hand, QED makes the absurd claim that photons somehow use all possible paths.

Cheers, Wolfgang

Science of yesterday degenerates into religion of today and superstition of tomorrow[/quote]

You are correct about the labelling. In classical mechanics it is possible to work out the path.

QED makes the valid claim that photons use all possible paths. For some strange reason this is verified by experiments. Look up quantum entanglement some time. If you really want to blow your mind then look up the Elitzur-Vaidman bomb-tester and its experimental verification: Interaction-free Measurement (PDF). Note that this experiment was done in 1994 so there are probably more recent ones (I will leave finding them as an easy exercise for you).

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Old 15th June 2008, 08:44 AM   #53
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Originally Posted by wogoga View Post
Both Bohr and Feynman were scientists in the theological tradition, preferring impressive counter-intuitive explanations to unprejudiced realistic ones.

Ah yes the old Science is a theology claim. Do you know why these “counter-intuitive explanations” are so impressive? Because they work, please provide any “unprejudiced realistic ones” that work better, along with the supporting experimental evidence for them.
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Old 17th June 2008, 10:34 AM   #54
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"The situation is especially strange as the path-integral method of QED is essentially the same as Huygens principle. So in this respect, QED is not even self-consistent!" (See)

Originally Posted by Reality Check View Post
The path-integral method of QED is not essentially the same as Huygens principle. The path-integral method integrates over all possible paths and is a quantum theory. Huygens principle adds up the waves from each point of an advancing wave front and is a classical theory.

A quote from Wikipedia:
Huygens principle follows formally from the fundamental postulate of quantum electrodynamics – that wavefunctions of every object propagate over any and all allowed (unobstructed) paths from the source to the given point. It is then the result of interference (addition) of all path integrals that defines the amplitude and phase of the wavefunction of the object at this given point, and thus defines the probability of finding the object (say, a photon) at this point.
We could also invert the order and say that the path-integral method of QED follows from Huygens' principle by formalization. Even the deficiencies are the same. Two quotes from mathpages.com:
From this simple principle Huygens was able to derive the laws of reflection and refraction, but the principle is deficient in that it fails to account for the directionality of the wave propagation in time, i.e., it doesn't explain why the wave front at time t + Dt in the above figure is the upper rather than the lower envelope of the secondary wavelets. Why does an expanding spherical wave continue to expand outward from its source, rather than re-converging inward back toward the source?
In any case, the Huygens-Fresnel Principle has been very useful and influential in the field of optics, although there is a wide range of opinion as to its scientific merit. Many people regard it as a truly inspired insight, and a fore-runner of modern quantum electro-dynamics, whereas others dismiss it as nothing more than a naive guess that sometimes happens to work. For example, Melvin Schwartz wrote that to consider each point on a wavefront as a new source of radiation, and to add the radiation from all the new sources together, "makes no sense at all", since (he argues) "light does not emit light; only accelerating charges emit light". He concludes that Huygens' principle "actually does give the right answer" but "for the wrong reasons". However, Schwartz was expressing the classical (i.e., late 19th century) view of electromagnetism. The propagation of light in quantum field theory actually is consistent with the very interpretation of Huygens' principle that Schwartz regarded as nonsense.
A third quote from the same page:
It could be argued that the "path integral" approach to quantum field theory – according to which every trajectory through every point in space is treated equivalently as part of a possible path of the system – is an expression of Huygens' Principle.
Cheers, Wolfgang
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Old 17th June 2008, 11:09 AM   #55
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Originally Posted by wogoga View Post
By the way, in principle it is possible to label each atom of a given diamond with a unique number.
No. It is in principle possible to label each carbon nuclei in a sample of diamond. It is most definitely NOT possible, even in principle, to label each electron in a sample of diamond. And electrons, not nuclei, dominate the interaction of light with matter. So you're simply wrong.
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Old 17th June 2008, 11:31 AM   #56
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Originally Posted by Reality Check View Post
You have it wrong. You do not really need QED to understand this.
Special Relativity that states that photons always travel at the speed of light in a vacuum. Matter (your "transparent medium") is mostly vacuum and photons travel at c in that vacuum. But photons are absorbed and emitted by atoms. This takes time and slows the measured speed of the photons.
In SR why view a photon as a particle and not an electromagnetic wave?

Electrodynamics already take all the effects of SR into acount anyway.
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Old 17th June 2008, 01:03 PM   #57
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Originally Posted by ponderingturtle View Post
In SR why view a photon as a particle and not an electromagnetic wave?

Electrodynamics already take all the effects of SR into acount anyway.
Because the subject of the threrad is photons.
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Old 17th June 2008, 01:10 PM   #58
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So, wogoga, where's the incredibly huge inconsistency?
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Old 17th June 2008, 01:17 PM   #59
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Originally Posted by Reality Check View Post
Because the subject of the threrad is photons.
But photons are not an SR object, but a QM object. Their SR counterpart is EM waves.

And EM is already in compliance with SR.
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Old 17th June 2008, 02:56 PM   #60
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Originally Posted by ponderingturtle View Post
But photons are not an SR object, but a QM object. Their SR counterpart is EM waves.

And EM is already in compliance with SR.
Ask the original poster.

But IMHO wave/particle duality means that it does not matter whether you treat photons as particles or waves. For example EM waves in media also do not travel at the speed of light (interference from scattering means that their effective speed changes).
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Old 17th June 2008, 02:57 PM   #61
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Originally Posted by godless dave View Post
So, wogoga, where's the incredibly huge inconsistency?

It would seem the inconstancy may be that he does not understand wave particle duality. Huygens principle is about wave theory only and therefore lacks the quantum elements so essential to modern physics and our modern technology. QED is a quantum theory and by that nature includes both wave and particle aspects. Regardless of their similarities (in wave aspects) Huygens principle is simply a principle about wave fronts and not a description of electromagnetic interactions (incomplete or otherwise). QED on the other hand is a complete and very precisely experimentally verified description of electromagnetic interactions.
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Old 17th June 2008, 05:07 PM   #62
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Originally Posted by Reality Check View Post
Ask the original poster.

But IMHO wave/particle duality means that it does not matter whether you treat photons as particles or waves. For example EM waves in media also do not travel at the speed of light (interference from scattering means that their effective speed changes).
I know, the point is that if you are really talking about special relativity then you are looking at a more classical theory
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Old 17th June 2008, 08:56 PM   #63
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Originally Posted by ponderingturtle View Post
I know, the point is that if you are really talking about special relativity then you are looking at a more classical theory

No, please remember that it was Einstein in one of the papers preceding Special Relativity that confirmed the quantum nature of light (photo-electric effect). Special Relativity is certainly not a classical theory (although classical theories of relative motion had been proposed before that).
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Old 18th June 2008, 05:34 AM   #64
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Originally Posted by The Man View Post
It would seem the inconstancy may be that he does not understand wave particle duality.
It is amazing how often that attitude is mistaken for a 'skeptical' stance on an issue. "I can't understand it, therefore you can't prove it".
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Old 18th June 2008, 06:20 AM   #65
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Photons have mass!!
I didn't even know they were Catholic.
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Old 18th June 2008, 07:01 AM   #66
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Originally Posted by The Man View Post
No, please remember that it was Einstein in one of the papers preceding Special Relativity that confirmed the quantum nature of light (photo-electric effect). Special Relativity is certainly not a classical theory (although classical theories of relative motion had been proposed before that).
I know that, it is also what won him the nobel prize. But what everyone is talking about here is from "On the Elctrodynamics of Moving Bodies".

E&M already fits perfectly with relativity and describes what happens to light perfectly.

The problem is that someone introduced the unnessacary concept of relativistic mass that it confuses people who don't really understand that it has fallen out of favor with physicists in general and so talking about massless particles is perfectly acceptable.
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Old 18th June 2008, 08:09 AM   #67
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Originally Posted by The Man View Post
Special Relativity is certainly not a classical theory (although classical theories of relative motion had been proposed before that).
That's not really correct, given the way these terms are used in modern physics. By a classical theory we mean one in which Planck's constant h is zero. Many classical theories - EM is a good example - are relativistic.

The point really is that SR is not exactly a theory - it's a set of rules which a theory can either be consistent or inconsistent with.
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Old 18th June 2008, 08:27 AM   #68
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Originally Posted by Reality Check View Post
If you really want to blow your mind then look up the Elitzur-Vaidman bomb-tester and its experimental verification: Interaction-free Measurement (PDF). Note that this experiment was done in 1994 so there are probably more recent ones (I will leave finding them as an easy exercise for you).
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Old 19th June 2008, 09:35 AM   #69
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Originally Posted by sol invictus View Post
That's not really correct, given the way these terms are used in modern physics. By a classical theory we mean one in which Planck's constant h is zero. Many classical theories - EM is a good example - are relativistic.

The point really is that SR is not exactly a theory - it's a set of rules which a theory can either be consistent or inconsistent with.
Sorry, I was referring to "classical" both in the sense of non-quantum (zero h value) and as applying to fixed universal space and time (upon which theories of relative motion prior to SR were based). I did not make that clear and my use of the term “classical” might not have been understood in both of those contexts.
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Old 19th June 2008, 11:26 AM   #70
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Originally Posted by wogoga View Post
By the way, in principle it is possible to label each atom of a given diamond with a unique number. If photons traversing this diamond actually were more than half of the time (n_diamond > 2) at rest (i.e. transformed into energy and momentum of carbon atoms), then it would in principle be possible to determine the path of a photon by enumerating the label-numbers of the atoms where the photon rested.

Originally Posted by Ziggurat View Post
No. It is in principle possible to label each carbon nuclei in a sample of diamond. It is most definitely NOT possible, even in principle, to label each electron in a sample of diamond. And electrons, not nuclei, dominate the interaction of light with matter. So you're simply wrong.

Your defense of the weird QED explanation of sub-luminal propagation speed of photons in transparent media is in the lines of Werner Heisenberg and Niels Bohr, who introduced immunization stratagems (uncertainty principle, complementarity) in order to defend their prejudices against genuinely physical objections (e.g. from Albert Einstein).

"Bohr rejected Einstein's particle of light, proposed in 1905, until well into the 1920s" (see). After evidence had shown more and more that Einstein was right, Bohr (and others) succeeded in transforming Einstein's physical photon-concept into a theological concept. Einstein then fought the theological properties attributed to quanta. Nevertheless, the supporters of the Bohr-fraction succeeded in convincing the world that Einstein (instead of Bohr) was the obstructionist in recognizing the reality of quanta.

What Ziggurat actually means is this:
I concede that physical reasoning (e.g. conservation laws, possibility of images in space and time) is applicable in the case of carbon atoms. However, such physical reasoning is not applicable in the case of electrons, because electrons are quantum objects, and quantum objects are not subject to physical reasoning.
But why should it not be possible to label the electrons of a diamond? It may be difficult or impossible to distinguish between the electrons of an electron pair. But from the fact that (normal, ideal) diamonds have a very regular crystal structure and are excellent electrical insulators, we conclude (by physical reasoning) that the two electrons of each carbon bond are essentially stationary. So if it is possible to label the carbon atoms, then it is also possible to label the carbon bonds and therefore the electron pairs.

So what Ziggurat advocates is this:
A photon traversing a diamond takes on the one hand all paths, i.e. the photon comes close to every single electron pair of the diamond. On the other hand, the photon is absorbed and reemitted by a sequence of (labeled) photon pairs.
Such a physical absorption and reemission is obviously inconsistent with the photons-use-all-paths claim. But in theology (as opposed to physical reasoning), there is always a solution. In analogy to virtual particles one can introduce virtual absorption and reemission. So photons are virtually absorbed and reemitted by all electron pairs of the diamond. In media with refractive index n > 1 in general, such virtual stops happening everywhere reduce the speed from c between two stops to c/n over many stops.

Cheers, Wolfgang
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Old 19th June 2008, 12:57 PM   #71
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I see Wolfgang is back on his "science is theology" hobby horse. Any yet more arguments from authority!

Where have I seen this before? I know - in every thread that he has posted in!

P.S. Wolfgang: QCD is not weird.

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Old 19th June 2008, 01:51 PM   #72
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Wolfgang: Just in case you are interested here is one of the tests of the fact that photons follow all paths in a system: Elitzur-Vaidman bomb-tester
Note that this test has been experimentally verified. Here is a paper on it (PDF)
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Old 19th June 2008, 03:10 PM   #73
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Originally Posted by wogoga View Post
Your defense of the weird QED explanation of sub-luminal propagation speed of photons in transparent media is in the lines of Werner Heisenberg and Niels Bohr, who introduced immunization stratagems (uncertainty principle, complementarity) in order to defend their prejudices against genuinely physical objections (e.g. from Albert Einstein).
Uh, no. The uncertainty principle is very physical, and can be experimentally observed all over the place. One of the simplest examples is a simple Stern-Gerlach experiment. Establish the spin about one axis, and measure it about another, and you'll see rather directly that the uncertainty principle holds, with direct and unambiguous consequences.

Quote:
What Ziggurat actually means is this:
Do not tell me what I mean. And you're still completely wrong. Nuclei are very much subject to quantum mechanics, but their larger masses and charges serve to localize them very well. The same cannot be said for electrons. That they do not behave the way your intuition suggests they should does not mean that they do not behave according to the laws of physics. That's your problem, not the universe's.

Quote:
But why should it not be possible to label the electrons of a diamond?
Because they are identical particles whose wave functions experience significant overlap.

Quote:
It may be difficult or impossible to distinguish between the electrons of an electron pair. But from the fact that (normal, ideal) diamonds have a very regular crystal structure and are excellent electrical insulators, we conclude (by physical reasoning) that the two electrons of each carbon bond are essentially stationary.
You can conclude whatever you like by whatever reasoning you think is applicable, but you're still be wrong. There are electrons in diamond which are delocalized. Diamond is a transparent insulator not because all the electrons are localized, but because the bands are full, and you cannot excite an electron without adding a significant amount of energy. Were electrons simply stationary and inert as you suggest, with every electron just stuck on one atom, carbon wouldn't even solidify, let alone turn into the hardest substance known.

Quote:
But in theology (as opposed to physical reasoning), there is always a solution.
You keep using the phrase "physical reasoning". I can only assume you mean hand-waving analogies, because what you're saying has absolutely no connection to any mathematical theory of the physical world. And here's a clue for you, since you seem to be in short supply: if you can't express your theory mathematically, nobody who actually knows anything about physics is going to take you seriously.
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Old 19th June 2008, 04:03 PM   #74
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Originally Posted by wogoga View Post
But in theology (as opposed to physical reasoning), there is always a solution.

You said it, Brother! Loosy-goosy gets the job done every time.

Theology: The study of the unknowable.
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Old 19th June 2008, 05:21 PM   #75
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Originally Posted by The Man View Post
Sorry, I was referring to "classical" both in the sense of non-quantum (zero h value) and as applying to fixed universal space and time (upon which theories of relative motion prior to SR were based). I did not make that clear and my use of the term “classical” might not have been understood in both of those contexts.
OK. FYI, the more common term for fixed space-time is "Galilean" or (less specifically) "Newtonian". When physicists say "classical", they always (in my experience at least) mean not quantum.

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Old 19th June 2008, 05:28 PM   #76
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Originally Posted by wogoga View Post
Your defense of the weird QED explanation of sub-luminal propagation speed of photons...
<nonsense snipped>
Wolfgang: do you see that computer you're reading this on? Do you know how it was made? Do you realize it's full of transistors, semiconductors, electron beams (if you have an old monitor), and tons of other extremely sophisticated parts? Do you realize that all that would never had been possible if physicists hadn't understood quantum mechanics?

Of course I'm talking to the guy that claimed the declining birthrate in Japan was due to a shortage of souls, so I'm not sure why I'm bothering.
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Old 19th June 2008, 10:12 PM   #77
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Originally Posted by wogoga View Post
Such a physical absorption and reemission is obviously inconsistent with the photons-use-all-paths claim. But in theology (as opposed to physical reasoning), there is always a solution. In analogy to virtual particles one can introduce virtual absorption and reemission. So photons are virtually absorbed and reemitted by all electron pairs of the diamond. In media with refractive index n > 1 in general, such virtual stops happening everywhere reduce the speed from c between two stops to c/n over many stops.

Cheers, Wolfgang

Why is physical absorption and reemission obviously inconsistent with the photons-use-all-paths claim? Sum over histories and the path integral refer to the paths from emission to absorption (or detection). A photon takes all paths from a physically emitting electron to the next physically absorbing electron within the lattice structure, not all paths through all valence electrons of the entire lattice structure. Real or physical photons require real and physical absorption and emission. What do you mean by virtual absorption? If the photons are not really absorbed or reemitted then they can not really be delayed. Even the exchange of virtual photons between the electrons and the protons of the carbon atoms involve real emission and absorption resulting in a real exchange of momentum. It seems that you only want physical absorption and reemission to be inconsistent with the photons-use-all-paths claim so you can solve that inconsistency by proposing your own principle of virtual absorption.

ETA:
http://en.wikipedia.org/wiki/Virtual_particle
Quote:
It is sometimes said that all photons are virtual photons. This is because the world-lines of photons always resemble the dotted line in the above Feynman diagram: the photon was emitted somewhere (say, a distant star), and then is absorbed somewhere else (say a photoreceptor cell in the eyeball). Furthermore, in a vacuum, a photon experiences no passage of (proper) time between emission and absorption. This statement illustrates the difficulty of trying to distinguish between "real" and "virtual" particles as mathematically they are the same objects and it is only our definition of "reality" which is weak here. In practice, a clear distinction can be made: real photons are detected as individual particles in particle detectors, whereas virtual photons are not directly detected; only their average or side-effects may be noticed, in the form of forces or (in modern language) interactions between particles.
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Old 19th June 2008, 11:09 PM   #78
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Originally Posted by wogoga View Post
"Bohr rejected Einstein's particle of light, proposed in 1905, until well into the 1920s" (see). After evidence had shown more and more that Einstein was right, Bohr (and others) succeeded in transforming Einstein's physical photon-concept into a theological concept. Einstein then fought the theological properties attributed to quanta. Nevertheless, the supporters of the Bohr-fraction succeeded in convincing the world that Einstein (instead of Bohr) was the obstructionist in recognizing the reality of quanta.

For those interested in the Einstein Bohr debates and not just what wogoga writes about them on other forums.

http://en.wikipedia.org/wiki/Bohr-Einstein_debates


Also check out the links in the “see also” section.
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Old 21st June 2008, 02:59 AM   #79
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Originally Posted by Ziggurat View Post
There are electrons in diamond which are delocalized. Diamond is a transparent insulator not because all the electrons are localized, but because the bands are full, and you cannot excite an electron without adding a significant amount of energy. Were electrons simply stationary and inert as you suggest, with every electron just stuck on one atom, carbon wouldn't even solidify, let alone turn into the hardest substance known.

Look at any visualisation of the cristal structure of diamond. The nuclei have a strong positive charge (6 protons versus 2 electrons), whereas each of the four bonds surrounding a carbon atom consists of an electron pair. The negative charge of such a pair is a strong adhesive between two neighbouring nuclei. The hardness of diamonds is due to the short distance between the positive nuclei and the negative electron pairs, resulting in huge electrostatic attraction. Because the electron pairs are (physically) stationary, a diamond is a good insulator and can only be deformed by breaking the bonds between atoms and thus resulting in fragmentation of the crystal.

Cheers, Wolfgang
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Old 21st June 2008, 03:31 AM   #80
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Originally Posted by wogoga View Post
The hardness of diamonds is due to the short distance between the positive nuclei and the negative electron pairs
...which also explains why hydrogen is far harder than diamond!
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