Dark matter is ordinary light.

Dark matter is ordinary light.

         This idea did not originate with me. I read it on a forum, two computers ago. Well over a decade. The idea was roundly condemned, including a number of posts that could be summarised as "that's why women should not be allowed to do science." However, the idea stuck with me. Leaving aside the question of mass, she made the argument that, photons are a good fit for dark matter.
         Photons, visible light, and others are all around us and almost totally invisible. I say almost because a tiny fraction of them enter an eyeball. Most do not.
         The predictable distribution of photons throughout the observable universe is about the same as inferred for dark matter. Halos around galaxies, sites of galaxy collisions, and galaxy clusters.
         Because the weight of photon has not been measured here on Earth, the weight of all of the photon produced since the big bang could not have been added to the weight of the observable universe. I think this last point may have been added by me, I'm not sure. The next bit is mine.
         Before continuing I would like to say something about the difference between facts, assumptions, and definitions.
Facts are simply that; known, proven, measured, certain. They should be stated as such. not as beliefs or definitions.
Assumptions are beliefs based on facts. Where an assumption is shared by a large group of reasonable people will probably be true. But only probably,
A definition is a statement of how the universe is supposed to be. And with pontifical arrogance, people expect the universe to behave its self and do as it is told.
         If that definition of a scientific definition seems a bit mischievous. Think about phlogiston.
It is a fact that wood can be burned in air. It is a reasonable assumption that this indicates something about the nature of chemistry. Someone defined a wonderful substance called phlogiston, which leaves the wood as it burned. Some very intelligent people made some assumptions based on that definition.Then because the universe would not do as it was told, science was left with an embarrassing episode in its history.

         C is defined as the speed of light. C is also defined as the speed at which an object with any mass would have infinite mass. It is assumed that these two definitions of C have the same value. However, the speed of light has not been measured to the point that a better more accurate value is not possible.
The value of the relativistic definition of C has never been measured at all. So the assumption that they are the same is just that, an assumption.

         A photon of light is defined as being massless particles. And if the assumption about C is correct, then that definition must also be correct. Or every photon would have infinite mass.

         Suppose for a moment, just as a thought experiment, that a photon has the tiniest amount of rest mass. Then the two definitions of C would have to have separate values. And photons would be an almost perfect match for dark matter.

Everywhere in the universe in vast amounts                    Check.
Unseen                                                             99.9r+% Check.
Massive                               thanks to relativistic effects Check.

         So is there any reason to think photons do have mass, despite the definition? There is the radiometer. The little mill, in an evacuated glass ball, is pushed around by light. There is the quantum mechanics idea that a light wave can turn into a particle and antiparticle, both of which have mass, which then annihilates producing a light wave. From Einstein equations we get f*h/C² = M. Frequency times planks constant divided by C squared equals mass.

A quick trailer for my next piece.
Ian and the new thing.
A story told in part from the perspective of a deaf-blind child.