This headline is pretty dumb. Dark matter is not a myth, it's clearly there in the data, so it exists for sure. Now the name might be completely wrong as it's neither dark and may not be matter, but it still exists. We should have just called it Pete or something, so the name wouldn't imply anything about it's properties. But the press always seem to think dark matter is something thought up to fix something, but that's not the case at all.

The numbers in the data don't match up and the difference is what's labeled as "Dark matter", simply putting another label on it or dismissing it doesn't fix the underlying data not matching up. And it isn't like a fault in the data, we've seen it in ALL the data, no matter what you look at or how you look at it, the signs of dark matter can be seen.

They keep saying "study" but this isn't a study, it's a math paper. This is a "model." The "model" shows this and that and those things, not "the study" of which there wasn't.

And what the "model" shows is that instead of invisible mass we can't see causing gravity, it could be alternating layers of invisible positive and negative mass.

There's even less evidence for negative mass being possible than for many dark matter candidates that "only" have to be massive and non-interacting (or weakly) with photons. It's always cool to kick around some new possibilities but this seems pretty weak. Negative mass opens up a big old can of worm(holes) too.

According to Lieu, the gravity needed to hold some galaxies or clusters together might come from “shell-like topological defects.” 

Topological defects are unique compact structures in space that have a high density of matter. 

Such defects likely first occurred in the early universe during phase transition — an event during which matter throughout the universe goes through a major physical change.

These defects might appear as long, linear formations called cosmic strings, or as flat, shell-like shapes.

“The shells in my paper consist of a thin inner layer of positive mass and a thin outer layer of negative mass; the total mass of both layers — which is all one could measure, mass-wise — is exactly zero, but when a star lies on this shell it experiences a large gravitational force pulling it towards the center of the shell,” Lieu explained.

It is somewhat similar to how photons, which themselves do not have mass, still experience gravity due to the presence of big astronomical entities. This is because when gravity warps space and time, it interacts with everything within the curvature whether it has mass or not.

Does this explain the bullet cluster? If it doesn't, it's kinda useless.

This will be a great comfort next time I step onto the scale

My pet hypothesis is that it's all virtual particles. Sometimes stuff just happens. Literally, stuff happens. Matter spontaneously emerges from a vacuum, as a consequence of quantum fluctuations. A divot and a hole form at the same time. When they rejoin, they zero out. And they will tend to rejoin immediately because they both have mass and there's nothing else for a zillion miles.

We observe this as the Casimir effect. Stick two flat surfaces really close together, in total vacuum, and they can act like there's gas pushing them apart. The divot and hole bounce off separate things. Clever tricks to abuse this have not worked: see every EM engine blasting energy into a vacuum chamber. As an engineer, not a scientist, I suspect some of the particles being blasted get negative momentum, somehow, and that's why the net force is immeasurable. Virtual particles play by their own rules.

But virtual particles still have mass. They bend spacetime as gravity. Cancelling that out would require negative mass, and antigravity, which sadly seems too cool to exist. This means all those pseudo-atoms in deep space drag things toward them. It looks like there's stuff out there, because... there was. Briefly.

This could also explain universal expansion. This transient noise in the fabric of reality means empty space has mass. So whatever we consider our universe, it's surrounded on all sides by unfathomable quantities of nothing, and the nothing is tugging it in all directions. It's not just escape velocity from the initial explosion; things are accelerating.

The MOND crowd pops up every now and then and makes some noise in the dark matter community. Evidence we do have points us toward matter, which is why we have billions being spent on detectors through various governments and collaborations around the world.

I’m not sure what direct detection experiments are going to do once we hit the neutrino floor.