Dr Joe. Your superb answers are very much appreciated. I am very much indebted to hear these explanations at first hand. However, I should point out that the explanation of the hyperfine transitions in atoms is not so facilely explained as present theories make out. If you remember Lamb and Bethe working on the problem of hyperfine structure transitions in the late 1940’s, came to the conclusions that the electron as it orbits the nucleus is constantly emitting and absorbing ‘virtual photons’. (i.e., undergoing virtual transitions) this is the Lamb shift. These virtual photons are exactly the same as ordinary photons with the exception that the interactions last for such short periods of time that they are to al purposes ignored by the laws of conservation of energy and momentum. Therefore, the idea of a spin flip is not entertained in this theory. These virtual transitions explain how the electron self regulates its energy and is able to remain in orbit around the nucleus without falling in. Surely such a theory is, if not better, at least equally acceptable as the sometimes wave sometimes particle theory of quantum mechanics?Hi Jzz - nothing amiss!
Actually, some of the hiss of radio/tv static is CMB!
Most electromagnetic radiation (of all wavelengths) is generated by so-called thermal sources: fusion or other forms of heating. (Some is "non-thermal", generated by, primarily magnetic fields and their interaction with electrons).
These thermal sources (stars, gas clouds, etc) radiate at all wavelengths (more or less) but the peak fo their emission varies with temperature, and the photons with wavelengths off the peak could be few and far between. For example, the Sun's surface is some 6,000 degrees. The peak of emission of the solar surface is in the middle of the visible part of the spectrum (of course), but there are also other photons, X-ray, gamma-ray, UV, radio, IR. But at lower numbers. A cold gas cloud (the state that most hydrogen is in for a galaxy like ours) emits most of its electromagnetic radiation in the radio. There are SOME photons at other wavelengths but relatively few. Certainly the gas clouds absorb photons, and the energy imparted lead to that 21cm wavelength emission line I mentioned originally.
Keep in mind that most hydrogen is locked up in stars (only about 10%, give or take, is in the form of interstellar gas clouds).
By the way, I'm not saying the universe is quiescent - far from it. But the preceeding gives a (very high level) picture of the electromagnetic radiation field. And you are correct about the neutrinos (but they are barely interacting with anything). By the way, there are far more photons zipping around than there are particles of matter, and they are mostly the microwave photons from the CMB.
To diverge for a moment. How does mainstream physics use this explanation and then blandly state that the term photon frequency is a misnomer, it doesn’t exist it is a mathematical abstraction used to explain the energy of a photon. Yet, in these hyperfine structure transitions, photon frequencies are very clearly seen. The crucial point is that microwaves with a frequency of 1420405751.768(2) Hz have such extremely low energy that they cannot possibly overcome the opposing electrostatic and lets’ face it even gravitational forces within the atom. Therefore, what happens is that when an atom is raised to a metastable state the only way in which it can release its energy is to emit ‘conduction photons’ which form micro currents that radiate at exactly 1420405751.768(2) Hz! Which is the excess energy gained. Thus, it is possible for the atom to mediate its energy by emitting conductions photons which give rise to micro currents that radiate at 1420405751.768(2) Hz.
Again, the 21 cm hydrogen line is of huge importance, its redshift allows the rotational speed of galaxies to be calculated and its relatively long wave-length also enables the mapping of the Galaxies and of the Universe. How can this be explained by these two conflicting ideas? Same result, different solutions to getting there. I had written a paper on this entitled: “Some new ideas in Physics” (see link below It gets interesting from about the last para on page 13.
One of the dichotomies of modern physics is that no a posterior models of sub-atomic particles can exist by reason of the very nature of the laws of physics as articulated by Quantum Mechanics. The whole edifice of Quantum mechanics is built on