Sunday, September 26, 2021

Do we understand the propagation of light?

We know that electromagnetic radiation is propagated when an excited electron orbiting a nucleus collapses from a higher orbit to a lower orbit or a higher state of energy to a lower state of energy thereby giving off light.
How well do we understand the process? Do we now understand exactly what’s taking place?
Do we know the shape of light quanta when propagated? Do we understand the reason for the speed of light? And how and why the speed takes place? Can we understand the starting energies and the energies of quanta after many years in space and of the ever-increasing size of light as it travels through space?
Is there an article, study or book that deals with electromagnetic propagation that could explain or explore this subject in detail?
Any reading material recommended would be appreciated.


  1. We know that nature tends to want to be in a state of low energy. So if an electron has a chance to be in a lower energy state, it will go there and release an electron (basic quantum mechanics). How it moves there is not really known, because the electron doesn’t circle around an atom, but is located everywhere in the universe, with the biggest probability in a special lob around the atom (also basic quantum mechanics, I can’t explain this very well in English).
    You can’t speak of a shape of light quanta. It is a photon, a wave, which behaves like a particle. (basic quantum mechanics)
    We do not know the reason for the speed of light, and there are theories that it is not constant (which would kill relativity).
    The reason for the ever expanding size of light is because space expands. As space expands everything in it expands as well, even you and me.
    I suggest you get a book about quantum mechanics. Not the popular stuff (like what the bleep do we know), but a scientific one. Like this one:
    Griffiths is a really great writer. His book about electromagnetism is great (Introduction to electrodynamics I believe).

  2. Wow, that’s a lot of questions. And unfortunately, they are from a very broad selection of physics. So it will be very hard to get a single book that tells you all the answers. In fact, it would take years of study to get a good understanding of these issues. So if you really want to understand, my advice is get a degree in physics. But, having such a thing myself, I can say a bit.
    We do understand electromagnetic wave propagation and the speed of light. If it is changing slowly (which it might be, we don’t know) we do not understand that. We understand the starting and long term energies of quanta (they wouldn’t change after many years in space). The only thing that changes the energy of a quantum is if the system changes. They increase in size due to uncertainty, not expanding universes. We do know the shape of propagating light (it is a reasonably simple math problem based on the shape of what the light is propagating through, though the simple problem can have an impossible to calculate answer). We do understand atomic orbitals and emission of photons when atoms de-excite. We do understand this process when it is stimulated (as is the case for lasers) and we do not really understand the cause of this process when it is spontaneous (not stimulated) which is usually the case.
    But all these questions are very complicated and come from electromagnetism, quantum mechanics, atomic physics, and relativity (both general and specific). But, probably your best bet would be to get a book on quantum physics, since most of these questions are rooted there. You could try Griffiths as was suggested. The Feynman lectures also cover a broad swath of physics, but at a fairly advanced level. To understand propagation of light, any optics book will help you, but would probably be too detailed. And you would need a book on general relativity to answer you speed of light questions, though a simple explanation would be found in most introductory E&M books that cover light (try Serway’s 2nd intro book or Holliday-Resnick).
    If you want to really understand these issues, you have months or years of work ahead of you.


Please enter your comment!
Please enter your name here

Explore additional categories