Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: thebrain13 on 20/12/2007 01:01:20
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I wish somebody could make me understand why we support the idea that force carrying particles exist. Why do we conclude that an object has to carry a particle over to another in order to affect it? What evidence supports that idea?
I'll start with the weak force and strong force. both particles are very shortlived so how do we measure them? Gravity has never been observed. And then there is the big grandaddy of them all the photon which mediates electromagnetism. Probably the inspiration for trying to unify the other forces to particles. But why? what evidence shows that a photon has any connection with electromagnetism. I can think of tons of reasons why it wouldnt, and I cant think of any reasons why it would. What is so convincing that causes most scientists to believe a photon regulates electromagnetism?
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Well... it all comes from applying quantum mechanics to fields. You probably accept that electromagnetism is classically regulated by the electromagnetic field. If you have an electric field, you can calculate how it will push or pull a charged particle around. However, if you apply quantum mechanics to this field, you find out that if you look closely enough there are tiny building blocks that make up this field. These building blocks are "photons." Therefore if the field regulates the force on a large-scale, its tiny building blocks have to actually be doing so on a small scale.
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What experiment shows that to be the case? What experiment shows that electromagnetism isnt a consequence of a smooth electric field that acts over a distance, but that it is "grainy" in nature? I know photons carry quantized amounts of energy, but what experiment connects them to electromagnetism?
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What experiment shows that to be the case? What experiment shows that electromagnetism isnt a consequence of a smooth electric field that acts over a distance, but that it is "grainy" in nature? I know photons carry quantized amounts of energy, but what experiment connects them to electromagnetism?
They say there are many: photoelectric effect, Compton effect, bunching/antibunching effect, multiphoton photoemission, which-way experiments ecc.
Some of them don't conclusively prove your assertion, but all together provides a strong evidence (and so reduces the probability of my interpretation [:(]).
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The classic experiments that caused Albert Einstein to realise that electromagnetism must be quantised into photons was the photoelectric effect. He won the Nobel prize for this work and not the theory of relativity. When you shine a light at the surface of some materials it is possible to expel electrons from the surface of the material. This photoelectric effect was used for light sensors before the current solid state devices were developed. The amount of electrons expelled depends on both the intensity and the frequency of the light but there is a threshold frequency below which no electons will be emitted however intense the light radiation is and if the radiation has a high enough frequency or short enough wavelength some electrons will be expelled however weak the radiation is. Different materials have different threshold frequencies. This result means that electromagnetic radiation comes in clumps with a defined energy that gets bigger as the frequency of the light gets higher. ie Quanta
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The classic experiments that caused Albert Einstein to realise that electromagnetism must be quantised into photons was the photoelectric effect. He won the Nobel prize for this work and not the theory of relativity. When you shine a light at the surface of some materials it is possible to expel electrons from the surface of the material. This photoelectric effect was used for light sensors before the current solid state devices were developed. The amount of electrons expelled depends on both the intensity and the frequency of the light but there is a threshold frequency below which no electons will be emitted however intense the light radiation is and if the radiation has a high enough frequency or short enough wavelength some electrons will be expelled however weak the radiation is. Different materials have different threshold frequencies. This result means that electromagnetic radiation comes in clumps with a defined energy that gets bigger as the frequency of the light gets higher. ie Quanta
They say that is not a strong prove. Standard (the one studied by Einstein) photoelectric effect seems to be described as well in a semi-classical way (EM wave described classically, metal described quantum mechanically), without the concept of photon. These computations are in "Mandl & Wolf - Optical Coherence and Quantum Optics".
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those experiments all show that light is quantized. But that is not my question. I know light is quantized. I don't know why light is considered the carrier of electromagnetic force. Why is there any connection between light and electromagnetism in the first place? what experiment shows that?
Why would it make any more sense to say light is the carrier of electomagnetic force than to say light is the carrier of gravitational force? What ties light to electromagnetism?
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Why is there any connection between light and electromagnetism in the first place? what experiment shows that?
The photoelectric effect certainly does. You shine a light onto metal and you notice that electrons are being kicked off the surface by electromagnetic forces. Clearly the light is carrying the electromagnetic force. You can do the opposite and oscillate a charged particle, which will create electromagnetic waves. If you do this fast enough you reach the "visible light" part of the spectrum. You can move the particle mechanically for long enough wavelengths of light.
Additionally, classical electromagnetic theory (Maxwell's equations) predicts electromagnetic radiation travels as waves at the speed of light. These equations came from trying to describe the forces of electricity and magnetism. The waves that come out of it weren't built into the theory, but are a consequence of how the fields work. If you look in nature for waves that behave as you expect electromagnetic waves to do, you find that light matches the requirements perfectly.
You could argue that the light is just riding along with an undetectable force-carrying field. If that were the case, then to the best of our knowledge and experimental evidence, that field has the same properties as the light riding it. So there's no real reason to think that the field is something separate from the light.
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How does this work in string theory?
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photons can affect electrons, how does that prove that photons are the mediators of electric force? Electrons can affect electrons, protons can affect electrons, does that make protons and electrons the mediators of electric force?
You guys keep telling me about the photoelectric effect and how light is quantized, but that seems completely arbitrary to me, unless you can show that electromagnetism is quantized too. Do you see how you created a little paradox here? The only way your argument works is if you allready proved that light is the only mediator of electric force. This is like me asking how do we know that gravity pulls planets together, and you guys responding gravity pulls the planets together.
How about I point out ways that photons act different from electric force, and ya'll can point out my errors.
1.The fact that photons are only created in oscilating/accelerating charges seems completely arbitrary since oscillation and acceleration have nothing to do with electromagnetism/maxwells equations.
2.if photons mediate the electric force, that would mean that a photon would have to arrive at an object in order for it to experience electric force, as far as I know, no experiment shows that to be the case.
3.Photons can be blocked/redirected, as far as i know no experiment shows that to happen to electromagnetism.
4. Photons always push, electromagnetism pushes and pulls.
5. electromagnetism is greatest at right angles to motion, photons dont mainly emit themselves at right angles to motion.
6. electrons always seem to be the emitters of photons shouldnt an equal amount come frome protons, since electric force applies to both?
7. electric force drops in strength at the inverse square law, photons would obey that law if they were emitted in completely random directions, they arent ie lasers.
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photons can affect electrons, how does that prove that photons are the mediators of electric force?
http://math.ucr.edu/home/baez/physics/Quantum/virtual_particles.html
One of the first steps in the development of quantum mechanics was Max Planck's idea that a harmonic oscillator (classically, anything that wiggles like a mass bobbing on the end of an ideal spring) cannot have just any energy. Its possible energies come in a discrete set of equally spaced levels.
An electromagnetic field wiggles in the same way when it possesses waves. Applying quantum mechanics to this oscillator reveals that it must also have discrete, evenly spaced energy levels. These energy levels are what we usually identify as different numbers of photons. The higher the energy level of a vibrational mode, the more photons there are. In this way, an electromagnetic wave acts as if it were made of particles. The electromagnetic field is a quantum field.
Electromagnetic fields can do things other than vibration. For instance, the electric field produces an attractive or repulsive force between charged objects, which varies as the inverse square of distance. The force can change the momenta of the objects.
Can this be understood in terms of photons as well? It turns out that, in a sense, it can. We can say that the particles exchange "virtual photons" which carry the transferred momentum. Here is a picture (a "Feynman diagram") of the exchange of one virtual photon.
\ /
\ <- p /
>~~~ / ^ time
/ ~~~~ / |
/ ~~~< |
/ \ ---> space
/ \
The lines on the left and right represent two charged particles, and the wavy line (jagged because of the limitations of ASCII) is a virtual photon, which transfers momentum from one to the other. The particle that emits the virtual photon loses momentum p in the recoil, and the other particle gets the momentum.
This is a seemingly tidy explanation. Forces don't happen because of any sort of action at a distance, they happen because of virtual particles that spew out of things and hit other things, knocking them around. However, this is misleading. Virtual particles are really not just like classical bullets.
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Electrons can affect electrons, protons can affect electrons, does that make protons and electrons the mediators of electric force?
You guys keep telling me about the photoelectric effect and how light is quantized, but that seems completely arbitrary to me, unless you can show that electromagnetism is quantized too.
Exactly! This is what is done in QED, Quantum Electro Dynamics: fields (E and B) are quantized. "Proves" in the sense of absolute proves don't exists; but the high experimental success of QED make physicists believe is a very good theory, one of the best ever created. Of course, one day it will be replaced with a better one, as happens with physics theory, one day or another...
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How about I point out ways that photons act different from electric force, and ya'll can point out my errors.
1.The fact that photons are only created in oscilating/accelerating charges seems completely arbitrary since oscillation and acceleration have nothing to do with electromagnetism/maxwells equations.
??? Are you sure to know what Maxwell's equations are?
2.if photons mediate the electric force, that would mean that a photon would have to arrive at an object in order for it to experience electric force, as far as I know, no experiment shows that to be the case.
Can you explain please?
3.Photons can be blocked/redirected, as far as i know no experiment shows that to happen to electromagnetism.
Who said it? Apply an electric field to a piece of metal and you can find that the electric field is canceled inside the metal.
4. Photons always push, electromagnetism pushes and pulls.
Attractive forces are not very simple to explain with photons, as the article from math.ucr.edu I linked in my previous post shows, but it's possible to explain with them.
5. electromagnetism is greatest at right angles to motion, photons dont mainly emit themselves at right angles to motion.
Who told you? If you move a charge periodically along a direction, it will generate an EM wave and so also photons, even in the perpendicular direction (furthermore, the fields are maximum just in the perpendicular direction, at high distances).
6. electrons always seem to be the emitters of photons shouldnt an equal amount come frome protons, since electric force applies to both?
When photons of enough energy interact with matter, they can create couples electron/antielectron.
7. electric force drops in strength at the inverse square law, photons would obey that law if they were emitted in completely random directions, they arent ie lasers.
Infact in that case electric and magnetic fields don't decay as 1/r2.
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There are em waves, there are charges, there are systems with charges bound to each other (atoms, molecules and larger structures).
It has been found, in hundreds of instances, that em waves are responsible for changes in the energy states,structure of chemical compounds and the currents which flow in conductors. All of the phenomena involved with these things have been demonstrated in countless different experiments and they all point to the same basic thing; electromagnetic waves interact with electronic systems.
The photoelectric effect proves (? yes) that electromagnetic energy is exchanged in small packets. We call these packets 'photons'.
BUT many, many of the effects caused by electromagnetic waves can be dealt with and proved without recourse to quantum physics. There are perfectly good classical arguments (Based on Maxwell's Equations) which show that electric and magnetic fields produce forces and that electromagnetic waves will produce 'pushing forces' because of the momentum which they possess.
If 'thebrain' were to read around a bit he would find that all his objections to the sum total of human knowledge are dealt with in most elementary electromagnetism textbooks.
Electrons are not ' the emitters of em waves' any more than protons or any other charged systems. It is when you have any system of charges and fields - e.g. an electron near a nucleus or an electron in a field or two atoms in a molecule or protons and neutrons in a nucleus etc, etc that you find there are photons involved when there are changes. IT SO HAPPENS that visible light is associated with the energies associated with the outer electrons around atoms. Other wavelengths of em radiation are associated with totally different levels of energy. There is nothing special about optical wavelengths except that we can 'see' them.
Before you start objecting to things you don't understand, make sure you digest precisely what is actually meant by the established Science dealing with those things. None of your seven points make any real sense and most are actually wrong. It is not worth dealing with them individually; read any good book and it will put you right on all of them - with rock solid derivations of the maths and good experimental evidence.
It is up to you to disprove, with a good body of evidence (not just loopy websites), not for them to re-prove what is already accepted.
If you can do that, we will all listen agog!
Go ahead - if you think you are hard enough.
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Brain you are talking rubbish. go away and read some basic textbooks.
The simple explanation is you get one hydrogen atom in a slightly excited state one of its electrons changes its orbit, loses some electromagnetic energy and emits a photon and nothing else. That is precisely how photons mediate the electromagnetic force ie every change of electromagnertic energy in every particle in a material invoves the emission and absorbtion of photons.
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Im just going to go over your rebuttals for all my points.
1. You dont have to answer this question since it isnt a problem per se, I just find it odd that the creation of photons corresponds with something that is totally unrelated to electromagnetism.
2. a photon is the mediator of electric force and the only mediator, so you could say that the only way for an object to experience electric force is if the object absorbs a photon. So if the titanic were to set sail and accelerate each one of its particles would have to absorb its very own photon, corresponding with the exact amount of energy required to accelerate it to that velocity. So if you ever found a particle that accelerated without absortion of a photon, not counting the other forces, that would violate the photon/electromagnetic connection. However this isnt a specific problem, the others are more specific, so lets just drop it.
3. okay your saying that if you put an object that is capable of blocking the photons that pass inbetween two charged objects, that it would also stop the net electric force between the two by creating an "anti field" of the exact opposite strength relative to the two(if it blocked all photons). This is the first real argument ive seen since its the only one that actually relates photons to electromagnetism. But I doubt that method actually works in every situation. I see a lot of potential problems with that idea. but ill just start with one. what if you put a great insulator, and an object that blocks a lot of photons in between it? Because in order for it to work, the blocking ability of the object would have to correspond exactly with the new induced field inside it.
4. I didnt understand the explanation in that link at all. did you? What experiments show that that idea is valid. Explanations like that is what makes people not like quantum mechanics.
5. whats wrong with my statement? the fields are maximum perpendicular to the force, so shouldnt the amount of photons released be maximum perpendiular to the motion as well?
6. I dont see how your response is remotely related to my question.
7. What experiment shows that electric and magnetic fields dont decay at 1/r^2
Also while I was writing this I thought of a couple more problems I dont understand. And Ill add them to my orignal list.
8. All objects dont emit the same amount of photons, an oxygen atom on the surface of the sun emits a lot more than an oxygen atom at the north poll. Yet electric charge is always conserved.
9. What about static objects with charge, how do they emit photons?
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4. I didnt understand the explanation in that link at all. did you? What experiments show that that idea is valid. Explanations like that is what makes people not like quantum mechanics.
Quantum mechanics isn't easy in the slightest. It's also counterintuitive in many ways, since it deals with scales which we never encounter in daily life. At any rate, to answer your rebuttal, the theory of using photons to create attractive forces has been thoroughly tested in all sorts of regions, and it agrees with reality. You can model atoms with it, as well as more fundamental particle interactions that take place at high energy particle accelerators, and the agreement with the photon theory is phenomenal.
5. whats wrong with my statement? the fields are maximum perpendicular to the force, so shouldnt the amount of photons released be maximum perpendiular to the motion as well?
I don't see why this is a problem. The direction in which more photons are released should coincide with the direction in which the field is biggest, so if the field is biggest perpendicular to the motion (such as in a dipole) then you'd expect more photons in that direction.
6. I dont see how your response is remotely related to my question.
Protons should emit photons just as electrons do. The issue is that they don't interact with things as easily as electrons do. Protons are locked up in the nucleus of atoms, while electrons are hanging out around the outer edges of the atom and ready to interact with incoming photons.
7. What experiment shows that electric and magnetic fields don't decay at 1/r^2
Fields radiated by point charges decay as 1/r^2, but general fields don't have to. Take a flashlight for example: the bulb emits a field that's decaying as 1/r^2, but when it reflects from the mirror, the beam gets a direction and certainly doesn't decay as 1/r^2 anymore.
Also while I was writing this I thought of a couple more problems I dont understand. And Ill add them to my orignal list.
8. All objects dont emit the same amount of photons, an oxygen atom on the surface of the sun emits a lot more than an oxygen atom at the north poll. Yet electric charge is always conserved.
What does electric charge being conserved have to do with photons? Photons don't carry charge. The number of photons something emits has to do with the strength of the field it emits which in turn has to do with how much it's moving around, or how much energy it has. A molecule in the sun has much more energy and therefore emits many more photons than a molecule at the north pole.
9. What about static objects with charge, how do they emit photons?
Photons are the basic building blocks of the electromagnetic field. As building blocks, if you add them up right you can make a wave that travels through space, or you can make a static fields, depending on how you add them up. Remember, though, it's very dangerous to think of something as "static," since every particle had to be created and moved into its current location at some time. The leading edge of the static field it's giving off has to exist somewhere. So it's going to look like a static field close to the particle but have an outward edge that's propagating.
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Im just going to go over your rebuttals for all my points.
1. You dont have to answer this question since it isnt a problem per se, I just find it odd that the creation of photons corresponds with something that is totally unrelated to electromagnetism.
You are wrong. Study electromagnetism.
2. a photon is the mediator of electric force and the only mediator, so you could say that the only way for an object to experience electric force is if the object absorbs a photon.
Yes, according QM. Where is the problem?
So if the titanic were to set sail and accelerate each one of its particles would have to absorb its very own photon, corresponding with the exact amount of energy required to accelerate it to that velocity. So if you ever found a particle that accelerated without absortion of a photon, not counting the other forces, that would violate the photon/electromagnetic connection.
Sincerely I didn't understand exactly what you want to say; anyway, if this is what you intended, atoms are bound together by EM forces and so by the exchange of virtual photons; so, if you apply a force to an atom of a rigid body, this force will be transmitted to all the other atoms by virtual photons exchange.
3. okay your saying that if you put an object that is capable of blocking the photons that pass inbetween two charged objects, that it would also stop the net electric force between the two by creating an "anti field" of the exact opposite strength relative to the two(if it blocked all photons). This is the first real argument ive seen since its the only one that actually relates photons to electromagnetism. But I doubt that method actually works in every situation. I see a lot of potential problems with that idea. but ill just start with one. what if you put a great insulator, and an object that blocks a lot of photons in between it? Because in order for it to work, the blocking ability of the object would have to correspond exactly with the new induced field inside it.
Please explain in detail, if possible with a drawing.
4. I didnt understand the explanation in that link at all. did you? What experiments show that that idea is valid. Explanations like that is what makes people not like quantum mechanics.
In this case I agree with you.
5. whats wrong with my statement? the fields are maximum perpendicular to the force, so shouldnt the amount of photons released be maximum perpendiular to the motion as well?
A simple *classical* analysis: in an EM wave which is plane and linearly polarized, E field is, e.g., directed along + x axis, B field along +y, so the wave is moving along +z axis. It hits a positive charge, what happens?
1. The E field accelerates the charge along the + x direction.
2. The B field acts on the now moving charge, because of the Lorentz force F = q vXB; since v is along + x and B along + y, the vectorial product and so the force is along the + z direction, exactly the direction of wave propagation.
6. I dont see how your response is remotely related to my question.
Sorry, I saw the word "photon" instead of "proton" in your post. The answer is that of course protons emits photons as electrons do. The reason you hear more often about electrons emitting photons is because in atoms are electrons which change their energies from one level to another, not protons, at least until nuclear reactions are not involved; in this last case nuclei change their energy levels and indeed photons are emitted (gamma photons).
7. What experiment shows that electric and magnetic fields dont decay at 1/r^2
Very simple case: in a spherical EM wave. There (at high enough distances from charges, that is, not in the near proximity of them) fields decay as 1/r. If the wave is plane, fields don't decay at all with distance. You don't need strange experiments, this is standard electromagnetism from about a century.
Also while I was writing this I thought of a couple more problems I dont understand. And Ill add them to my orignal list.
8. All objects dont emit the same amount of photons, an oxygen atom on the surface of the sun emits a lot more than an oxygen atom at the north poll. Yet electric charge is always conserved.
Photons don't have electric charge and even if they had, your reasoning wouldn't prove anything: to excite an atom so that it then emits photons, you have to give it energy; even if you give it this energy by collision with another atom, this collision is mediated through electromagnetic forces, so you will have to exchange virtual photons with that atom; if photons were electrically charged, you could ascribe electric charge conservation to the fact that you give electric charge to that atom when you excite it.
9. What about static objects with charge, how do they emit photons?
And if they didn't emit photons, but they simply generate classical fields, how do they generate them? If you answer me to this question, I answer to your. [:)]
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First off, I dont understand why you guys are all attacking me (outside of jp) for asking supposedly elementary questions that could be explained by any electromagnetism textbook. Apparently asking questions is rubbish, right soul surfer?
My questions represent that I dont understand how this works, you guys pretend like im trying to tear down the theory or make up new physics, im not. And even if I was I still wouldnt understand your rudeness. They are problems that I see in the theory that I dont know how to resolve, Im not saying that they cant be resolved, or that they are real "problems".
Maybe im a really bad writer, since I never seem to get my point across, but let me point out to you why I am not accepting your logic to my question. Remember what my question is? What evidence shows that electromagnetism is mediated completely and only by the emission of photons. Observe the structure of my questions, all my questions start with my understanding of electromagnetism, and then my understanding of how photons are emitted, then I try to tie them together, but I find that when I do that they seem incompatible. Notice that I state something about electromagnetism AND something about photons. The question is about how to relate the two, so your answers should also be about relating the two, just like my questions do. You guys always only mention one side of the argument, and you assume that the answer is a given while you are answering. Does this make any sense to anyone?
For example the photoelectric affect seems to be a popular choice to supposedly "answer" my question. This is an experiment that explains the nature of photons. Its not about the nature of electromagnetism, unless you assume that the answer to my question by saying "and since photons are the mediators of electromagnetism, electromagnetism is also quantized". You cant make that jump, IT IS MY QUESTION. That's about as usefull as telling me supercalifragilisticexpeolidoucious means supercalifragilisticexpeolidoucious. You cant assume the answer of the question while answering. Now please if you dont understand what I mean by this, just stop answering my questions, since you will only make me more frustrated.
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1. Where in electromagnetism does it say that acceleration affects the strength of
charge?
3. Im just saying that if your theory of blockage works then the ability for an object to block photons from passing would have to correspond exactly with its reluctance to become polarized. does it?
5. Great you explained how electromagnetism affects the strength of charge perpendicular to the motion, I allready knew that, where is your connection then to quantum mechanics theory where it apparently says photons are emitted more in a perpendicular direction to motion?
6. Well if electrons are in better position to absorb photons, wouldnt that mean that electrons should have a stronger charge on average than protons?
7. Talking about groups of particles just complicates things, im talking about the individual, since macroscopic scales are just the products of the individual. There are ways to direct the emission of a photon, I dont know of a way to direct the field of electromagnetism, or at least not in the same way you would direct a photon.
8. I didnt mean that photons carry negative or positive charge, making other particles more or less charged. I meant that if you had an object with the same amount of charge, lets say two electrons. If one was in a position to absorb more photons than the other, it would push harder than the other(if photons are the carriers of electric force)
9. Charges affect each other wether they are accelerating or not.
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First off, I dont understand why you guys are all attacking me (outside of jp)
I have answered to your questions, why do you call it "attacking"? Certainly if I answer you but you don't understand or you don't want to verify in the books what I tell you, I cannot do more than what I've already done.
for asking supposedly elementary questions that could be explained by any electromagnetism textbook. Apparently asking questions is rubbish, right soul surfer?
My questions represent that I dont understand how this works, you guys pretend like im trying to tear down the theory or make up new physics, im not. And even if I was I still wouldnt understand your rudeness. They are problems that I see in the theory that I dont know how to resolve, Im not saying that they cant be resolved, or that they are real "problems".
Maybe im a really bad writer, since I never seem to get my point across, but let me point out to you why I am not accepting your logic to my question. Remember what my question is? What evidence shows that electromagnetism is mediated completely and only by the emission of photons. Observe the structure of my questions, all my questions start with my understanding of electromagnetism, and then my understanding of how photons are emitted, then I try to tie them together, but I find that when I do that they seem incompatible. Notice that I state something about electromagnetism AND something about photons. The question is about how to relate the two, so your answers should also be about relating the two, just like my questions do. You guys always only mention one side of the argument, and you assume that the answer is a given while you are answering. Does this make any sense to anyone?
For example the photoelectric affect seems to be a popular choice to supposedly "answer" my question. This is an experiment that explains the nature of photons. Its not about the nature of electromagnetism, unless you assume that the answer to my question by saying "and since photons are the mediators of electromagnetism, electromagnetism is also quantized". You cant make that jump, IT IS MY QUESTION. That's about as usefull as telling me supercalifragilisticexpeolidoucious means supercalifragilisticexpeolidoucious. You cant assume the answer of the question while answering. Now please if you dont understand what I mean by this, just stop answering my questions, since you will only make me more frustrated.
To lightarrow
1. Where in electromagnetism does it say that acceleration affects the strength of
charge?
Nowhere, infact it's wrong. No one of us has ever stated that. Your previous question was different:
"The fact that photons are only created in oscilating/accelerating charges seems completely arbitrary since oscillation and acceleration have nothing to do with electromagnetism/maxwells equations."
3. Im just saying that if your theory of blockage works then the ability for an object to block photons from passing would have to correspond exactly with its reluctance to become polarized. does it?
Sorry but I sincerely didn't understand your question (not to mention that it seems completely different from your previous question).
5. Great you explained how electromagnetism affects the strength of charge perpendicular to the motion, I allready knew that, where is your connection then to quantum mechanics theory where it apparently says photons are emitted more in a perpendicular direction to motion?
At this point it's not clear of what kind of "motion" you are referring. Previously I tought you was talking about the direction of the wave's propagation; is that what you mean or something else?
P.S. Electromagnetism never "affects the strength of charge"
6. Well if electrons are in better position to absorb photons, wouldnt that mean that electrons should have a stronger charge on average than protons?
Sorry but I don't understand the meaning of this phrase.
7. Talking about groups of particles just complicates things, im talking about the individual, since macroscopic scales are just the products of the individual. There are ways to direct the emission of a photon, I dont know of a way to direct the field of electromagnetism, or at least not in the same way you would direct a photon.
A photon is as directed as the EM wave is, no more no less.
8. I didnt mean that photons carry negative or positive charge, making other particles more or less charged. I meant that if you had an object with the same amount of charge, lets say two electrons. If one was in a position to absorb more photons than the other, it would push harder than the other(if photons are the carriers of electric force)
Ok, let's say one electron absorbs more photons and so it's pushed more than the other. Where is the problem? In the photoelectric effect (e.g.) you don't observe all the metal's electrons coming out of it!
9. Charges affect each other wether they are accelerating or not.
But they affect each other differently if they are accelerating or not. If one of them is accelerating, then, at high enough distances, the coulombian force is practically zero, while the EM radiation "push" is not. This because static electric field decays as 1/r2 while dynamic fields decays as 1/r (in a spherical wave radiation).
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Brain we have tried very hard to explain the process to you in simple language but you seem to be unable to accept the explanations for some reason and persist in asking what is essentially the same question. What is more you seem to be using inaccurate physics to try to prove that the explanations we are giving are wrong.
You must remember that apart from the gravity that holds us on the surface of this planet just about everyting you experience and what you are made of is down to electromagnetism and the exchange of photons between particles and is fully explained by these processes.
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I think this is an example of laziness. People would rather have an argument / question and answer session than go to the trouble of reading a textbook. There can be no objection to using textbooks on the grounds that they aren't up to date. So far, brain, you have not approached near enough in your understanding to push the frontiers further than they were in about 1950. When you have used some rigour, some proper maths and a lot of reading, you will have answers to nearly all of you questions / objections. Trying to learn about a subject like this is hopeless if you rely on questions of your own making - there are far too many blind alleys if you try it that way.
You are making far too many assertions about things you don't yet understand - no wonder you are getting on peoples' nerves. Private study from books will give you a chance to increase your basic knowledge - and to see that the whole subject is VERY BIG AND HARD.
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"oooooooooooooooooohhhh" -using both hands raises handbag to chin..........
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Was I too harsh?
It's just that people don't engage their brain before starting to write.
This stuff isn't trivial and I wish people would acknowledge it.
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Q: Can a magnetic field interrupt the path of a laser? Can a magnet bend light? —"Bending light", Vancouver, British Columbia, Canada
[NASA] Laser light reflected by mirrors but unbent by magnets
A: A magnet can bend the path of any moving charged particle. In fact, that’s how your TV screen displays a video picture. A magnet deflects a beam of electrons to create a video pattern on the screen. Light, however, has no charge and therefore its path is unaffected by a magnet.
But, you mention a magnetic field, which includes changing fields. If it’s a changing field, things get more complicated. Any changing magnetic field generates a changing electric field and that produces an electromagnetic wave.
Electromagnetic (EM) waves cannot interact directly with light photons since photons have no charge. EM waves do not bend light, at least enough that we can measure. If radio waves, for example, bent light appreciably then a transmitting radio station would look blurry. But stations don’t go blurry.
Actually, electromagnetic waves can bend light through an indirect, quantum effect—but to such a tiny degree that we cannot measure it. This quantum effect (called Delbrück scattering) "is a process where, for a short time, the photon disintegrates into an electron and positron pair," says Norbert Dragon, physicist at the Institute for Theoretical Physics in Hanover, Germany. The charged pair interacts with an EM wave and then recombines into the photon with a changed direction. Thus, the EM wave bends the light.
"More probably the charged pair will annihilate into two or more photons—this process has been observed under extreme conditions—but, then, the light ray is not bent but rather split into several rays," says Dragon.
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I got to admit that I find the idea of them having a EM 'field' a little weird myself. I can see them as having a (quantized) momentum depending on 'energy', but from that to a oscillating electromagnetic field? The question seems to be if it is only momentum creating the photoelectric effect, why does it need to of a certain energy to do the job, knocking of a electron? Why does massive amounts of less 'energy'-rich 'photons' fail to the same when directed?
But that one seems not altogether true. "billions of slightly lower energy put together..." cannot produce a photoelectron. This is only true for the single-photon photoemission, which is what the standard photoelectric effect is. We have plenty of observations of multiphoton photoemission using photons with energy LESS than the work function." from ZapperZ
So I can understand Brains confusion somewhat :) If it only was Electromagnetic oscillations, shouldn't magnets 'bend' a photon? Also " No, the accelerating of a charged particle such as an electron does not increase the charge of the electron, it merely increases the energy carried by the electron, as a result it releases this excess energy as photons. Photons do not create EM force, they are the EM force as it were, when negative charged particles approach each other they exchange photons, therefore giving each accelerating each other away from one another. " from noblec04.
well, if 'photons' are the 'EM force'?
Why don't they 'bend'?
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They transfer energy, right?
So when meeting that electron, could I see that as a transitionally effect in where the photon interact, in a 'emergence' momentarily changing state, that is if we assume that another photon is emitted later? I must admit that I'm having a lot of problems with those slippery rascals :)
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gosh, reading stuff from 2007 is crazy, this was my least favorite thread ever. I think this is an example of me very thoroughly misrepresenting what I was trying to say.
I was questioning why do we believe that the forces have to travel in particles at all? What decisive proof exists that particles don't react with each other directly and smoothly over a distance? And that the "force carrying particles" are just misnamed pieces of mass.
The photoelectric effect isn't a good example because all it does is show that photons need specific amounts of energy to dislodge an electron. That fact doesn't really have anything to do with whether or not the photon is the carrier of electric and magnetic force.
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From your original post.
what evidence shows that a photon has any connection with electromagnetism
Brain you are talking rubbish. go away and read some basic textbooks.
The simple explanation is you get one hydrogen atom in a slightly excited state one of its electrons changes its orbit, loses some electromagnetic energy and emits a photon and nothing else. That is precisely how photons mediate the electromagnetic force ie every change of electromagnertic energy in every particle in a material invoves the emission and absorbtion of photons.
That seems to be the simplest and most straightforward answer to me.
Here is another that says the same thing even simpler:-
The frequency of light emitted by an electron is the same as the orbital frequency of that electron.
The photon and electron are the most basic 'particles' and the above shows their intimate equivalence
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And here's another completly but very obvious answer to the question:-
From your original post.
what evidence shows that a photon has any connection with electromagnetism
Your looking at it right now. [;D]
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Hi all,
Sorry for bumping a very old topic, but I am doing some personal research in this specific area and wanted to ask something specifically related to photons and EM force. are involved. What I don't understand is this thought experiment:
Initial assumption:
Virtual photons are the carriers for EM force even in static situations.
Initial setup:
Two oppositely charged parallel metallic plates are set up like a simple capacitor, inside the plates are an uniform static electric field, fringe fields are ignored.
Based on the force carrier model, virtual photons are responsible for this uniform electric field. A plate of non-conductive, non-polar material should be capable of blocking any photons (except for high energy ones?).
In this case, the force carriers would be unable to reach their destination and there would be no electric field.
But in reality the electric field passes straight through the non-conductive plate.
Where have I gone wrong?
Cheers Zed.
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Think i got stuck on that one too some while ago? At least a similar one using two 'horse shoes'. And I found a answer to it but I'll have to look it up. And no Brain, your questions wasn't stupid, even then :) It's all about getting to see how people think, and using a forum like this for it helps a lot.
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A nice question might be.. If photon's only push, how can a electro magnetic field attract? .. And I'm paraphrasing yours there Brain :)
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http://www.thenakedscientists.com/forum/index.php?topic=18161.0
It's sort of really nice :)
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It's hard to see how a fuzzy "electron cloud" could interact with the electromagnetic fields of a photon to promote the electron into a fuzzy cloud with a slightly different shape.
Perhaps a macroscopic illustration of photon electromagnetism is the rainbow, where light is bent on passing through raindrops.
- Water has a different permittivity than free space (http://en.wikipedia.org/wiki/Permittivity). This means that the water "resists" the electric field of the photon, and light travels more slowly through water, causing refraction.
- A similar effect happens for materials which have a different permeability than free space (http://en.wikipedia.org/wiki/Permeability_%28electromagnetism%29), only this time it is the magnetic field of the photon which is affected.
- So light is an electromagnetic effect, because the velocity of the photons are affected by the permittivity and permeability of the medium they are passing through.
Or perhaps we can see electromagnetism by blowing it up from the quantum domain to a more familiar macroscopic scale, where the electrons are constrained to known paths instead of fuzzy clouds?
- Instead of protons jiggling inside an atomic nucleus and producing gamma rays (photons with very high energy)
- ...or an electron jiggling inside an atom and producing visible light
- ...or a molecule changing its rotation and emitting infra-red light (photons with slightly lower energy)
- How about electrons oscillating in a coil of insulated wire and producing radio waves (photons with a very low energy)?
You can detect the radio wave photons in two main ways:
- With a coil of wire - the oscillating magnetic field of the photons induces an oscillating current in the coil of wire which is picked up by the radio receiver
- With a "Rabbit-Ears" antenna (similar to a TV antenna), where the electric field of the photons induces an oscillating voltage between the two wires, which is picked up by the radio receiver.
- This experiment courtesy of Hertz, Marconi etc illustrates the Transverse Electromagnetic Field nature of electromagnetism