tisdag 6 december 2022

Corruption of Modern Physics 18: What is a Photon?

This is a continuation of Corruption of Modern Physics 1 as a celebration of the 2022 Nobel Prize in Physics to be delivered on Dec 10 by King Carl XVI Gustaf. 

I read in Electromagnetic fields, size, and copy of a single photon by Shan-Liang Liu:

  • Light is almost involved in each field of science anddaily life of everyone, and yet light’s true nature has eluded us for centuries. 
  • Albert Einstein successfully explained the photoelectric effect in 1905 by the assumption that light is composed of photons and showed that a photon has constant energy hν and momentum h/λ where h is the Planck constant, ν is the requency, and λ is the wavelength. 
  • The theory of relativity tell us that a photon has zero rest mass and always moves at the speed of c=λν in vacuum.
  • However, these answers are not satisfactory. Roy J. Glauber once jokingly summarized his theory of photo detection by the sentence: “I don’t know anything about photons, but I know one when I see one”.
  • Single photons are essential for the fundamental study of the quantum mechanics and the development of photonic quantum technologies such as optical quantum computing and quantum communication
  • However, there is not still a satisfactory answer to the problem what a photon is.
  • Experiments have indicated that a single photon can locate in very small space and very short time duration  but how to know the size of a photon is till a puzzling question. 
  • The wave-like properties of light or photons are well described by the classical theory of electromagnetic fields. 
  • How to properly describe the electromagnetic fields of a single photon is still a fundamental and unresolved question in physics. 
So I get confirmation for my long held suspicion that physicists still today, in particular in the light of the Nobel Prize in Physics this year which was awarded to so called entangled photons, do not know what they are talking about when they are talking about photons. This is yet another example of the strangeness of modern physics.

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