# Enlightening Dark Matter?

As an ironic twist, I wanted a story in which dark matter is actually caused by light. Somehow, the physics of light cause it to create the appearance of the existence of dark matter. But I'm not a theoretical physicist, so I'm not sure how this COULD work. What changes would be needed in the physics of how light works for it to be responsible for the apparent presence of dark matter, given that up until now, scientists haven't detected the difference?

Emphasis would be on giving an explanation that can be relayed in a story. If there are exotic implications for physics in general, please explain them.

• The more I think about this question, the less sense it makes. "Dark matter" is a gravitational effect that affects the trajectories of celestial bodies on a galactic scale. There's nothing light to do to "create the appearance" of that; even optically faking the positions of celestial bodies doesn't get rid of their gravitational effects or other physical behaviors of matter being somewhere other than its faked position. Aug 31, 2021 at 4:12
• @GrumpyYoungMan I'm looking for something outside the box that is a property light COULD have that no one understands, and accounts for the apparent existence of dark matter. Like, "Light actually behaves like it had mass, but the effect is so tiny, they didn't see it, and all the light emitted and unabsorbed over the history of the universe accounts for dark matter." Or "Light acts differently than our models suggest, and "Dark Matter" is simply a manifestation of how light really behaves, because (fill in reason). If there is no answer, it's simply impossible. I'll accept a frame challenge. Aug 31, 2021 at 4:20
• Unfortunately, the fact that we can see other galaxies shows that the light escapes them, instead of staying trapped around them to produce the effect of dark matter. And dark matter is also needed to account for effects on the cosmic background in the very early universe. And this would break the equivalency of mass and energy... Oct 31, 2021 at 1:08

We have theories in which this is actually the case!

There's a class of dark matter candidates known as dark photons. There are many different theoretical variants, but they all involve a new boson corresponding to a $$\mathrm{U}(1)$$ gauge symmetry, much like the photon - and so the dark photon gets its name not because it has anything directly to do with the electromagnetic force, but rather because it obeys a similar mathematical structure. In some models, this dark photon interacts with dark matter; in others, it's actually the main component. This has led to plenty of experimental searches for dark photons, both in particle accelerators and in astronomical observations.

This doesn't quite satisfy your requirements - there's a difference between photons and particles that obey the same symmetries. Fortunately, we can invoke something called kinetic mixing, a predicted phenomenon in which dark photons could in fact change back and forth into regular photons, analogous to neutrino oscillations. This provides a mechanism for light to not just be responsible for dark matter, but to actually be dark matter.

We don't know if this is the case in our universe, but it's theoretically possible to have self-consistent physics in which dark matter and photons are intimately related - and that's all you need for yours.

Dark matter is responsible for temporal refraction of photons: while for ordinary refraction we see the beam of light slightly changing its direction of propagation in space, for temporal refraction we would see changing its propagation in time, meaning that we would either see the beam appear from nowhere or disappearing without any sign.

The disappearance would account for why the dark matter is "dark": any light we shine on it will be visible somewhere in the past or the future, not in the time we are doing it.

• If there was temporal shift in the past, we'd see the dark matter from future, if there was a temporal shift to the future, we'd see dark matter from the past (relatively speaking). But we'd still see it, unless something else happens too.
– hyde
Jan 27 at 10:19

# Complex Frequency photons

When there is a high photon concentration in a region of the space that have a strong gravity well (like stars), then some negative frequency photons will appear and travel some time $$\lambda$$ were they will decay in imaginary frequency photons, that will interact with the Higgs field, thus making for the missing matter in the universe.