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Just like it says in the question title. I have heard that photons are force carriers of electromagnetism.

Is it not true, that when a golf club imparts force on to a golf ball, then the fundamental force involved is the electromagnetic force ? Is yes, then would it be true , that during this interaction, there is some kind of photon transfer from / between golf club and golf ball ?

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  • $\begingroup$ True. what of it? $\endgroup$ Jun 12, 2021 at 10:51
  • $\begingroup$ In that case, is it true for magnets as well ? If a magnet is attracting another piece of metal across the room , then are photons moving across the room ? Are these photons same as "regular" photons ? Can these photons be measured/detected through sensitive enough instruments ? HAVE they been measured/detected through sensitive enough instruments ? $\endgroup$ Jun 12, 2021 at 10:54
  • $\begingroup$ They are virtual photons, of course. The detection question is wide off the mark. $\endgroup$ Jun 12, 2021 at 10:56
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    $\begingroup$ Does that mean that these virtual photons are hard to detect with current tech ? Or do you mean , they are not even detectable theoretically ? Are the existence of these virtual photons something of an "interpretation" thing where the math says they have to exist to make sense of the observations ? But they can never be observed ? $\endgroup$ Jun 12, 2021 at 11:03
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    $\begingroup$ They are a shared metaphor for a mathematical computational technique in quantum mechanics. $\endgroup$ Jun 12, 2021 at 11:15

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The blank assertion that "photons are the force carrier of the electromagnetic force" is sort of true, but a bit misleading if you don't have the technical knowledge to unpack what it is trying to say.

When the golf club pushes the ball, it is correct that the forces are largely electromagnetic. The situation also involves the Pauli exclusion principle (the fact that two electrons can't occupy the same state of motion and spin) and in consequence the whole interaction is quite complicated, but for present purposes let's just consider electromagnetic interaction between a pair of charged things such as electrons.

When we say that "photons" are involved in this kind of electromagnetic repulsion, the word "photons" is very much in inverted commas. These are not real photons, not like the ones you see with your eye or which travel along in light beams etc. Rather, it is a way of talking about how the underlying physics of quantum fields and their interactions works. The interaction between charged objects can be expressed as an integral over all the ways in which one object (e.g. an electron) can interact with the electromagnetic field which in turn interacts with the other object (e.g. another electron). These interactions can themselves be expressed a number of ways, but a particularly nice way is to assert that an electron emits something called a "virtual photon". This virtual photon is quite like a real photon, but not completely like, the main difference being that it does not propagate like an ordinary wave but more like an exponentially decaying excitation, and it should not be considered as a thing which could in any sense go on its way to the rest of the world and interact with anything else. Rather, it is a way of talking about part of the interaction between the particular two electrons under consideration.

A good image here is that of a diagram where two electrons come in, and two go out, and in the middle various virtual photons are exchanged in a network of interactions: but notice, none of those virtual photons come in or out as overall input or overall output to the network. When you understand quantum field theory, you know that this aspect of the diagram tells you that these "photons" are not entities with any independent existence of their own; they are just a convenient way to discuss, and calculate accurately, the interaction between two electrons via the electromagnetic field.

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  • $\begingroup$ Your answers are always interesting and good to read. Nevertheless, what you are saying here is something like, since the magician takes the white rabbit out of the previously folded hat, it must have always been there.Isn't it time to give the electric field and the magnetic field new elementary particles to be defined as the basis of their structure in a model-like way? $\endgroup$ Jun 13, 2021 at 4:15
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    $\begingroup$ So, are virtual photons really more of a mathematical model to make sense of what is happening ? $\endgroup$ Jun 13, 2021 at 5:32
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    $\begingroup$ If they arent even real photons, why did we call them, well, photons? And then why is quantisation of forces taken so seriously when it is just for mathematical elegance and nothing else. $\endgroup$ Jun 13, 2021 at 6:13
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    $\begingroup$ @IndischerPhysiker why not post that as a question? $\endgroup$ Jun 13, 2021 at 6:20
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    $\begingroup$ New question by IndischerPhysiker: physics.stackexchange.com/q/645218/123208 $\endgroup$
    – PM 2Ring
    Jun 13, 2021 at 12:07
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What is an electromagnetic force?

We have an electrical interaction between the electrical charges of the subatomic particles and a magnetic interaction between the magnetic dipoles of the subatomic particles.

Furthermore, we have inductive processes in which two of three participants induce the third (electric drive with the Lorentz force, electric generator and the electromagnets).

And last but not least, we have electromagnetic radiation, in which mutually dependent electric and magnetic field components move through space at the highest possible speed. The photons of this radiation are part of the known list of elementary particles.

Virtual photons have been brought into play out of ignorance or lack of interest in the inner structure of electric and magnetic fields. They do not exist, but at least one can draw diagrams with them and concoct verbal explanations. Let's wait and see when the inner structure of fields will meet with interest in science. Then the embarrassing solution of virtual photons can be consigned to the mothballs.

There are no verifiable interactions between two golf balls at a distance. Between two contacting golf balls there is electrical repulsion from the surface electrons.

Of course, there is a temperature balance between everything and everyone that is on the line of sight to each other. Any body above zero Kelvin emits photons. More precisely, the excited subatomic particles do this. And are themselves excited by incoming photons from other bodies.

The direct line of sight is the only criterion for direct interaction between two bodies. But this does not mean that it is the main interaction. The gas molecules between the bodies have a much stronger influence on the temperature progression of the golf ball than the second golf ball does. Simply because the lines of sight to the gas molecules are more numerous and the event of photons arriving from the gas molecules happens much more frequently.

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    $\begingroup$ " The direct line of sight is the only criterion for direct interaction between two bodies " But doesnt magnetic and electric force act upon bodies even without line of sight ? $\endgroup$ Jun 13, 2021 at 5:30
  • $\begingroup$ Of course yes: A charge between two charges develop a common field between all three of them. $\endgroup$ Jun 13, 2021 at 5:42

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