How does QED explain charge interaction in the macro world?

In summary, QED explains macro-world dynamics through the statistics of the quantum world. The laws of physics in the macro-world are the average behavior of many particles in the quantum world. The exchange of virtual particles is responsible for the attraction and repulsion between like and unlike charges, respectively. This is due to the symmetry of the wavefunction and gauge invariance. The reason for the different behaviors lies in the coupling of particles to the electromagnetic field, which can take on both positive and negative values. The math behind this reveals that like charges repel and opposites attract. Further discussions and explanations can be found in various sources such as Zee's book "Quantum field theory in a nutshell".
  • #1
DennisChen
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0
I have personally been deeply fascinated by the processes and principles that underlie the QED and have done some recent research myself. However, recently my teacher posted me a question that stunned me. He went,"Why do like charges repel and unlike attract?" In QED I understand that this is due to electromagnetic interactions between charged particles by exchanging virtual photons. However, what left me hanging in curiosity was how the virtual photons cause the difference between attraction and repulsion. Does it have something to do with the momentum of photons? And how does this translate to the macro world? Essentially, why do "unlikes" attract and "likes" repel?
 
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  • #2
QED explains macro=world dynamics in terms of the statistics of the quantum world. The macro laws of physics appear as the average behavior of many particles in the quantum world. But I don't think that's what you mean.

You mean, "how can a particle exchange lead to an attractive force?"

It's down to the symmetry of the wavefunction of the virtual particle.
http://math.ucr.edu/home/baez/physics/Quantum/virtual_particles.html
 
  • #3
Its to do with gauge invariance - it's not even really quantum in nature although its nice looking at it that way:
http://quantummechanics.ucsd.edu/ph130a/130_notes/node296.html

For the detail see if you can get a hold of the following:
http://scitation.aip.org/content/aapt/journal/ajp/61/2/10.1119/1.17279

The reason lies in the coupling to the EM field can take on positive and negative values. There is no more fundamental reason for that except you really would like some way to have zero net charge (charge is basically a measure of how strongly a particle couples to the EM field).

Chug through the math and low and behold like charges repel, opposites attract.

Thanks
Bill
 
  • #4
There is also a nice and interesting discussion in Zee's book "Quantum field theory in a nutshell", which shows that whether a theory leads to repulsion or attraction of particles of like charge depends on the spin of the mediating particle being odd or even.
 
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1. How does QED explain the concept of charge interaction in the macro world?

Quantum electrodynamics (QED) is a theory that explains the interaction between electrically charged particles in the macro world. According to QED, these interactions are caused by the exchange of photons, which are particles of light. This theory states that charged particles are surrounded by a field of virtual photons, and when two particles interact, they exchange these virtual photons, resulting in the attraction or repulsion between the particles.

2. What is the role of virtual particles in QED's explanation of charge interaction?

Virtual particles are a key concept in QED and play a crucial role in explaining charge interaction in the macro world. These particles are not physical particles like electrons or protons, but rather fluctuations in the quantum field. These fluctuations create a force field that surrounds charged particles and allows for the exchange of virtual photons, which ultimately leads to the interaction between the particles.

3. How does QED account for the strength of charge interaction in the macro world?

QED uses mathematical equations to describe the strength of charge interaction in the macro world. These equations take into account the charge of the particles, the distance between them, and the exchange of virtual photons. The closer the particles are, the stronger the interaction between them will be, and the larger the charge of the particles, the stronger the force will be.

4. Can QED explain all types of charge interactions in the macro world?

QED is a very successful theory and has been able to explain a wide range of charge interactions in the macro world. However, there are some phenomena, such as the strong nuclear force, that cannot be fully explained by QED. This is where other theories, such as quantum chromodynamics, come into play.

5. How does QED relate to classical electromagnetism?

QED is a quantum theory, meaning it describes the behavior of particles at a very small scale. In contrast, classical electromagnetism is a macroscopic theory that explains the behavior of electrically charged particles on a larger scale. However, QED can be used to derive the equations of classical electromagnetism, providing a deeper understanding of the underlying principles of electromagnetism.

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