onsdag 15 maj 2024

Feyman Doubling Down by QED


Feyman diagrams revealing the deepest secrets of Nature.

This is a continuation of the previous post on the evolution of theoretical physics during the 20th century in a sequence of doubling downs to a new more complex theory when facing difficulties with an old theory instead of resolving the difficulties. Let us take a look at the step from the Quantum Mechanics QM of atoms of the 1920s to the Quantum Electro Dynamics QED of the 1950s including light preparing for Quantum Field Theory QFT as the ultimate quantum theory of modern physics underlying the Standard Model of elementary particles.   

QED was presented to a general public by its leading proponent Richard Feynman in 4 lectures later collected into the book QED The Strange Theory of Light and Matter. 

Newton's primitive idea of light as a stream of light particles was in the late 19th century replaced by Maxwell's equations, where in particular light appears as a wave carried by oscillating electromagnetic fields. Maxwell's equations concisely captures all of electromagnetics as the top jewel of classical mathematical physics. 

Einstein refuted Newton in 1916 and Feynman refuted Maxwell in 1948 and so returned to Newton: Light is a stream of particles named photons. In the book Feynman's argues: 

  • The theory of QED describes Nature as absurd from the point of view of common sense. 
  • We have so far, found nothing wrong with QED. It is therefore the jewel of physics- our proudest possession.
  • It is very important to understand that light behaves as particles, especially for those of you who have gone to school, where you were probably told something about light behaving like waves.
  • We were talking about light. The first important feature about light is that it appears to be particles: when very weak monochromatic light (light of one color) hits a detector, the detector makes equally loud clicks less and less often as the light gets dimmer
  • Newton thought that light was made up of particles- he called them "corpuscles"—and he was right (but the reasoning that he used to come to that decision was erroneous). We know that light is made of particles because we can take a very sensitive instrument that makes clicks when light shines on it, and if the light gets dimmer, the clicks remain just as loud-there are just fewer of them. Thus light is something like raindrops-each little lump of light is called a photon—and if the light is all one color, all the "rain- drops" are the same size.
  • So now, I present to you the three basic actions, from which all the phenomena of light and electrons arise. ACTION #1: A photon goes from place to place. ACTION #2: An electron goes from place to place. ACTION #3: An electron emits or absorbs a photon.
  • The problem is, when we try to calculate all the way down to zero distance, the equation blows up in our face and gives meaningless answers-things like infinity. This caused a lot of trouble when the theory of quantum electrodynamics first came out. 
  • People were getting infinity for every problem they tried to calculate!
We see here typical ingredients of doubling down raising the bid so that it cannot be called as in poker: 
  1. The theory is absurd beyond comprehension. 
  2. The theory is perfect with perfect agreement with observation. 
  3. The theory appears to give meaningless results. 
  4. The theory is primitive as being reduced to Action #1-3.   
Since the theory is incomprehensible it cannot be questioned or called. That the theory shows perfect agreement with observation is impossible to check, since direct application of the theory by a non-expert gives meaningless infinities.

The reason QED produces infinities is Action #3 which opens to self-interaction: An electron emits a photon and then absorbs the photon, as discussed in this post showing the danger of self-feed back. 

Feynman like Einstein propelled himself to be the golden boy of modern physics as expressed in the book Genius: The Life and Science of Richard Feynman. In later years his geniality has been questioned by e g Freeman Dyson in particular the mystery of self-interaction.

The argument that light is shown to be a stream of particles because light can give rise to "clicks" of an instrument, is as silly as saying that a good joke is a particle because it can give rise to a laugh.  


PS The Standard Model divides particles into matter (fermions) and force carriers (bosons) with photon the massless carrier of the electromagnetic force. The trouble with this double set of particles with matter particles interacting by forces transmitted by force carrying particles, in the above setting electrons interacting by emitting and absorbing photon particles, is that it opens to self-interaction going wild into infinities. In the setting of gravitation this would require some form of graviton particles, which have not been found. Instead, gravitational force appears to come from a gravitational potential field present everywhere. The trauma of modern physics is that the Standard Model is incompatible with gravitation. The trouble comes from the role of bosons as force carrying particles. If there are no gravitons, maybe there are no bosons either? And then what about QED and QFT?   

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