The accepted wisdom is that photons are pure energy; massless particles of light. However, a distinction is made between REST mass and mass at the speed of light. Apparently photons do have mass while they are travelling at or near the speed of light. In fact, if we look at Einstein's famous equation explaining the relationship between mass and energy, E=mc squared, we can readily see that a photon, which we all agree is energy, MUST have mass. In the equation, if mass is zero, then c (the speed of light) must also be zero, and E (energy) would also have to be zero. But there IS energy in a photon and therefore there must be mass. The question then becomes, is the mass of the light in the galaxy sufficient to explain the galaxy's high apparent gravity? Maybe not by itself, but it looks like it might be part of the solution as to why galaxies don't fly apart due to their high rotational velocities. Maybe it is the mass of light AND the as yet undefined dark matter together that keep galaxies together.

Merit? As much merit as any hypothesis has until it is proven true or false.

I only have one word to say:
“The earth is flat”

Therefore this is wrong

At this is may only be a hypothesis. Of course, science has never claimed to be complete as new things are discovered every day. We (humanity) have a long way to go before we can perfectly define the how of gravity, light, space, and time. It is possible that Dark Matter and / or Dark Energy many not exist -- we just lack the ability to sense it, as of today.

I see theories, no matter how obscure, as being paramount to the advancement of science and knowledge. There was a video titled "Particle Fever" that showed both theoretical and applied physicists working on an idea of finding a particle and determining the existence of a multi-verse.

@hankster -- We have discovered doesn't matter and it has been shown to have no effect on anything whatsoever.

Yes, the thought is credible, but the effect (as stated in the article) would not be much. We know that photons do affect matter, so it isn't too much of a stretch to think that some of the rotational velocity differential might be affected by light. It is a notion worth looking into.

Very interesting, this is something to watch for...just to see if a new discovery will solve the mystery.

That's really interesting. I can't wait to hear how this plays out.

Like the article says, if photons had mass, then Proca stress would have given our own sun a highly elliptical orbit, which didn't happen, so I dunno why this theory is being considered.

This is interesting. Note also that in beer brewing light and it's absence play an important role. Also, beer is brewed in large but round containers. A big square container will not do the job. In many ways our Universe would seem to fit this also. What if we are all a brain in a beer vat? Should we fear being drank?

I like this. Thinking outside of the box! Fun thought to entertain anyway.

Not so "dark" after all. Who knows? The science is beyond me, let the experts figure it out.

how the universe works, on the science channel, explains dark matter rather well. i'm convinced it is at least likely (better than just possible).

g

The only merit I can rescue from this is the statement that we must keep looking. Dark matter remind me of the "ether" story...... Anyhow, last time I checked photons don't have mass and Proca applies to Z and W bosons, not photons.

In the text says that even counting on it, it is not enough. That was my first reaction.
Dark matter is an unknown in the equation.
Lets say you have a box of fruits, you put 3 apples there, and then you go count how many fruits are in the box, but you are in the dark, you count 7 fruits.
You know that there are 4 dark fruits there, you know they are there, you can measure them, but you do not know what they are until you can see it.
That is dark matter. It can be one thing, it can be many, it can be a new effect that we do not know. We just know that there is more things that we can see/detect generating gravity.

Also, we need to confirm or dismiss this experimentally because it is a theoretical study, it means that in paper it works (there is no mistake in the calculations).
For example: I saw a car going out of my town and you saw this car arriving in your town (50km distance) 1 hour later. We can say that the guy drove continuously at 50km/h, or he drove 100km/h with a long 30 min pause, or he drove 150km/h but went to your town, came back and went again.
All those models can explain the current observations. So until we find a way to measure in the middle of the road we cannot discard any of those, at the same time none of them can be the correct one. There can be more pauses, variation in speed, some shortcut that we are not aware off, 2 cars that are perfectly equal fooling us etc.

Basically in science you never discover what is true, you just discard the wrong ones and write in what conditions this theory is a good approximation of the experiments. (you control how wrong and not how correct you are)

I’m no astro physicists, so I can’t speak directly about it’s merits. Though the article said something about a ‘new paper’ on this subject. You may want to see the peer reviews to determine it’s validity.

Cool. Thanks for the post.

"What if...?" questions are just speculation. No merit until proven.

Above my pay grade. Ask @TheAstroChuck .