What happens when a particle is absorbed?

[Dale]

I believe a complicated object with a breathing organ like a photon must have a structure. What do you think?

Is this perhaps a machine translation error? A photon does not have organs (organs are body parts like the heart and liver) and does not breathe (breathe means to inhale and exhale air) nor does it have any structure (it is a fundamental particle). Surely you did not intend to say any of that.

 

[Darwin123]

If the linier momentum and the angular momentum are the only concern related to that kind of energy used to create a photon then do you mean the energy is a kinetic energy?

Here, energy means both kinetic energy and the energy associated with rest mass. Most particles have a nonzero rest mass. Photons have a zero rest mass, but they have a positive kinetic energy.

I mean, how two particles work together to control the speed of the newborn photon to be exactly c?

I am a physicist, not a veterinarian!

 

[John Huang]

Is this perhaps a machine translation error? A photon does not have organs (organs are body parts like the heart and liver) and does not breathe (breathe means to inhale and exhale air) nor does it have any structure (it is a fundamental particle). Surely you did not intend to say any of that.

Thanks for listening. About breathing, the electic/magnetic field moves with a photon (or is carried by a photon) is like a sine wave, not a constant amount, don't you think it is like the photon is breathing energy? About organ, since a photon in a laser beam can aim at a precise point so that its energy is stored at the center kernel and it also has polarization so that a photon has extended part to handle polarization. A fundamental particle still has a shape, isn't it? That is what I like to know.

 

[Dale]

Thanks for listening. About breathing, the electic/magnetic field moves with a photon (or is carried by a photon) is like a sine wave, not a constant amount, don't you think it is like the photon is breathing energy?

No, as several other people have already told you, its energy is constant. You need to forget this incorrect idea that its energy cycles up and down.

The field of a photon is not a classical field from Maxwell's equations with an associated classical energy density. It is a quantum field (aka wavefunction) which represents the probability of detecting the photon there. Wherever you detect it, it will have its full given amount of energy.

About organ, since a photon in a laser beam can aim at a precise point so that its energy is stored at the center kernel and it also has polarization so that a photon has extended part to handle polarization.

You have to be very careful talking about photons in laser beams. The photons in a laser beam are in what is called a coherent state, which has some strange properties. For one, there is an uncertainty relationship about the number of photons, meaning that a laser beam does not have a definite number of photons.

http://en.wikipedia.org/wiki/Coherent_states

A fundamental particle still has a shape, isn't it? That is what I like to know.

That is an interesting question. I suppose that you could come up with one or more shape operators and use those to measure the shape of a photon. It would be a lot of effort, and I don't think that anyone has bothered, but I don't know why it couldn't be done.

Since photons are eigenstates of the energy operator they would undoubtedly not be eigenstates of the shape operator, so I think that the most you could say would be that their shape is uncertain.

 

[John Huang]

No, as several other people have already told you, its energy is constant. You need to forget this incorrect idea that its energy cycles up and down.

The field of a photon is not a classical field from Maxwell's equations with an associated classical energy density. It is a quantum field (aka wavefunction) which represents the probability of detecting the photon there. Wherever you detect it, it will have its full given amount of energy.

To change an idea is easy if the main difficulty is solved. My question for QFT is how the high possibility sections are established by the nature.

You see, if a photon moves along a STRAIGHT line at a CONSTANT speed with a GIVEN energy, then logically speaking, you will expect an EVENLY distributed possibility EVERYWHERE on the line to find that photon. Isn't it? How can the nature assign the CREST and TROUGH sections of that line to have high possibility under the idea of QFT?

I don't know what kind of energy is carried by a photon. To make a photon both wave and particle, a photon may have different mass, electric field, speed or possibility per cycle. To me, all of three possible energies and the fourth option of possibility are not easy to understand. That is why I think, it will be a little bit easier if a photon will never die.

 

[Dale]

You see, if a photon moves along a STRAIGHT line at a CONSTANT speed

That isn't even close to an accurate description of how a photon moves. A better description would be that a photon moves along all possible paths at all different speeds simultaneously. Each of these possible paths interferes with all of the others in a specific way to establish the probability of detecting the photon at a given time and place.

To me, all of three possible energies and the fourth option of possibility are not easy to understand. That is why I think, it will be a little bit easier if a photon will never die.

It might indeed be easier, but unfortunately we are stuck with a not-so-easy universe. What you suggest is contradicted by experiment, and the more complicated idea is confirmed by experiment.

 

[mfb]

You see, if a photon moves along a STRAIGHT line at a CONSTANT speed with a GIVEN energy, then logically speaking, you will expect an EVENLY distributed possibility EVERYWHERE on the line to find that photon. Isn't it?

If a car moves along a straight line at constant speed with a given energy, do you expect a uniform distribution for its position on the line (if you measure it)? I don't.

How can the nature assign the CREST and TROUGH sections of that line to have high possibility under the idea of QFT?

Photons have a circular polarization, they do not have those concepts.

I don't know what kind of energy is carried by a photon. To make a photon both wave and particle, a photon may have different mass, electric field, speed or possibility per cycle.

No.

 

[John Huang]

That isn't even close to an accurate description of how a photon moves. A better description would be that a photon moves along all possible paths at all different speeds simultaneously. Each of these possible paths interferes with all of the others in a specific way to establish the probability of detecting the photon at a given time and place.

Yes, "Each of these possible paths interferes with all of the others in a specific way" and a photon always appeare (ALMOST 100% as we are able to measure) with a constant speed along a straight line in VACUUM.

It might indeed be easier, but unfortunately we are stuck with a not-so-easy universe. What you suggest is contradicted by experiment, and the more complicated idea is confirmed by experiment.

If the experiment must CREATE a photon, physicists will face another problem. What kind of force should be used to accelerate a photon to run from 0 to c and how long does it take? If a photon will not die, it will be easier with the exchange of momentum.

 

[mfb]

Yes, "Each of these possible paths interferes with all of the others in a specific way" and a photon always appeare (ALMOST 100% as we are able to measure) with a constant speed along a straight line in VACUUM.

The result of the interference of all possible parts is usually something close to a straight line, this can be calculated.

If the experiment must CREATE a photon, physicists will face another problem. What kind of force should be used to accelerate a photon to run from 0 to c and how long does it take? If a photon will not die, it will be easier with the exchange of momentum.

No. There is no need to accelerate anything.

 

[andrien]

Photons have a circular polarization, they do not have those concepts.

Hey,what about the plane polarized?

Yes, "Each of these possible paths interferes with all of the others in a specific way" and a photon always appeare (ALMOST 100% as we are able to measure) with a constant speed along a straight line in VACUUM.

which path,can you follow photon?

If the experiment must CREATE a photon, physicists will face another problem. What kind of force should be used to accelerate a photon to run from 0 to c and how long does it take? If a photon will not die, it will be easier with the exchange of momentum.

Damn it!

 

[Dale]

Yes, "Each of these possible paths interferes with all of the others in a specific way" and a photon always appeare (ALMOST 100% as we are able to measure) with a constant speed along a straight line in VACUUM.

As an expectation value for the speed of a large number of photons, sure. However, the question you posed was not about speed but about how the probability amplitude varies, and the interference I mentioned is how.

If the experiment must CREATE a photon, physicists will face another problem. What kind of force should be used to accelerate a photon to run from 0 to c and how long does it take?

The expectation of the speed never runs at 0 and always runs at c, so there is no photon acceleration. Furthermore, the expectation of the momentum, like the energy, is always constant.

If a photon will not die, it will be easier with the exchange of momentum.

Again, nature doesn't care about what is easier for you to understand, so it is completely useless to talk about it.

 

[Darwin123]

You see, if a photon moves along a STRAIGHT line at a CONSTANT speed with a GIVEN energy, then logically speaking, you will expect an EVENLY distributed possibility EVERYWHERE on the line to find that photon. Isn't it? How can the nature assign the CREST and TROUGH sections of that line to have high possibility under the idea of QFT? [/QUOTE]
So obviously, the photon DOESN'T always move in a straight line at a constant speed. This type of motion is inconsistent with the wave nature of light.

Quantum field theory (QFT) hypothesizes that the photon behaves both as a wave and as a particle. Properties that are inconsistent with either model under the conditions of the experiment are hypothesized to be impossible.

Under the experimental conditions one is determining the diffraction pattern, the wave properties of light have to dominate. Therefore, the photon can't move in a straight line with a constant speed under those experimental conditions.

[/QUOTEI don't know what kind of energy is carried by a photon. To make a photon both wave and particle, a photon may have different mass, electric field, speed or possibility per cycle. To me, all of three possible energies and the fourth option of possibility are not easy to understand. That is why I think, it will be a little bit easier if a photon will never die.[/QUOTE]
According to QFT, all energy carried by a photon is kinetic energy. Because the photon has a zero rest mass and zero charge, there is no potential energy associated with the photon. In a constant gravitational potential, all changes in the energy of the photon are changes in kinetic energy.

The photon is part of the electromagnetic field. Therefore, the energy of a photon can also be called electromagnetic field energy. However, this hypothesis is not mutually exclusive of the energy being kinetic energy. Generally, when light is acting as a wave we call it electromagnetic field energy. When it is acting as a particle, we call it kinetic energy. It is the same energy.

According to QFT, the photon does not change energy during a cycle.

What may be confusing you is the behavior of photons in a short pulse. In a short pulse of light, which may contain only one cycle, the photons have a wide distribution of energies. However, the energy of each photon does not change during the pulse. The energy of each individual photon in a short pulse is indeterminate due to the uncertainty principle. However, the energy of the photon does not change during the cycle.

There are incomplete models outside of QFT that include the gravitational potential of a photon. According to general relativity (GR), the photon "carries" gravitational potential energy. This has been "proven" in such experiments as the Rebecca-Pound experiment. However, there is as of yet no complete theory that includes both QFT and GR.

 

[berkeman]

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