What did Feynman mean?

  • Thread starter Farn
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  • #1
Farn

Main Question or Discussion Point

As I was recalling one of the Feynam lectures, I rememberd him saying that the only phenomena QED couldn't explain are the physics of the nucleus and one other that I can't remember...gravity maybe? Anyway, since QED deals with atomic particle interactions it was the nuclier one that surprised me. I sort of got the impression that he ment both QED and QM couldn't explain nuclier physics(but not sure if he was including QM).
So my questions are: Does anyone know what aspects of nuclier physics are not explainable with QED? AND, was he including QM when he said that?
 

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  • #2
chroot
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QED, quantum electrodynamics, is a quantum-mechanical theory of electromagnetism. You can think (loosely) of the following relationship:

quantum mechanics + classical electrodynamics = quantum electrodynamics

QCD, quantum chromodynamics, is a quantum-mechanical theory of the strong force, which is the force responsible for keeping protons and neutrons together in nuclei. QCD and QED are peers, one describing electromagnetism with quantum mechanics, and one describing the strong force with quantum mechanics.

There is currently no quantum-mechanical theory of gravity, though several approaches (loop quantum gravity and string theory) are being attempted simultaneously.

- Warren
 
  • #3
FZ+
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Maybe it's because QED = Quantum electrodynamics refers to the EM force, and for nuclear effects you should be looking at QCD = Quantum Chromodynamics which deals with the strong nuclear force that is dominant in nuclear interactions?
 
  • #4
elas
All quantum theories are predictive theories that predict behaviour. They do not explain the cause of the action or what the entities are.
There is some difficulty with this because most books fail to point out the limitations of the Standard Model (quantum theories and relativity) but Scientific American recently did a special issue on this subject and the steps being taking to find the answers.
Feyman stated in one of his lectures that no one has explained what magnetism is and in his opinion no one ever would. This appears in one of the lectures in the three volume publication of his lectures. If you have access to a copy (I do not) look up the opening lecture on magnetism.
 
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