I think it’s just a shit stirring paper to say “look, here’s something that has zero observational evidence to its existence and look how ridiculous it sounds. Dark matter also has zero observational evidence, so why is that not ridiculous?” Which I’m not sure I agree with, but based on the faaar stretches he makes in the paper and the comments by the author later, that’s what I gather.

Basically my take on it. It’s a new theory on gravity, but I’m not equipped to properly peer review it. For me, it’s an interesting read and is from a reliable source.

The weight of your brain. Gottem

I don’t think it is. If there are photons bouncing around in a material it contributes to its mass. Thought it’s an interesting question, does a singular photon traveling through space warp spacetime?

Also photons being defined as massless is the reason they can travel at the speed of light.

Because radiation = photons.

It helps to realize that mass is just a bookkeeping label that we assign to the “internal” energy of a system, where the choice of what counts as being “internal” is somewhat arbitrary and depends on the level we are studying.

For example, if you measure the mass of the nucleus of some atom, and then compare your measurement to the sums of the masses of the protons and neutrons inside of it, then you will see that the numbers do not agree. The reason for this is that much of the mass of a nucleus is actually the energy of the strong force bonds holding the nucleons together.

But you can actually drop down another level. It turns out that the vast (~ 99%) majority of the mass in the proton in turn does not come from the quarks but from the energy of the gluon field holding them together.

And if you drop down yet another level, the quarks get their mass through their interactions with the Highs field.

So in short, it is energy all the way down.

Dark Matter isn’t a theory. It’s a feature of some theories to account for otherwise unexplained phenomena (galactic rotation curves, microlensing, the structure of the CMB) but no one knows what Dark Matter actually consists of. It’s basically a placeholder which is compelling for some reasons (theories without Dark Matter tend to explain some but not all of the above phenomena) but not compelling for others (unable to determine what the stuff is made of).

The aether came about by an argument from ignorance rather than the observations. Until the discovery of the wave-like nature of light it was believed that all waves travel in some medium, like the waves on water. Then it was assumed there must be some medium for light as well. But this was an invalid assumption without any evidence to back it up.

The difference is that aether unraveled pretty quickly when we started seriously looking for it because experiments kept being outright inconsistent with what it was predicted we would see if it were there, whereas there are lots of independent lines of evidence that all point to the dark matter existing in the same page, so it really is not the same situation at all. The only problem with dark matter is that it doesn’t show up in our particle detectors (so far, at least), but there is no law of the universe that says that everything that exists has to.

The best way I’ve heard it put is “dark matter isn’t a theory, it’s a series of observed problems with our current model”

I think it’s simply more a placeholder term for something people haven’t found out enough about yet.

I’ve always wondered why people treat dark matter as a concrete fact. “Dark force” would be a better name, since we don’t even know that there’s matter there! We only presume it’s gravity keeping galaxies together and we only presume that it’s gravity due to matter. We also only presume that space is homogenous and that gravity has an equal effect across all regions of space.

It kind of is. It’s an extra variable introduced to account for a bunch of things that aren’t adding up.

Aether was the same thing, until people discovered electromagnetic fields. People knew light was a wave. Waves travel faster through more solid mediums. Light is pretty damn fast. Space is pretty empty.

Things didn’t add up. Light is simultaneously traveling through possibly the stiffest material in the known universe while also through nothing at all. People had to come up with Aether to try to explain that.

It was wrong, but it was an obvious placeholder acknowledging that something huge is missing from our current theories.

Tbh I have always had the same feeling about the absolute limit of speed being the speed of light (and thus most of relativity). I have always been curious if the behavior we observe that lines up with the theory is something akin to transition energy in a material. Once a material reaches the appropriate temperature to phase change, additional energy is needed to actually change phases. If you were able to raise water to precicely 100°C and only impart exactly as much energy is lost to infrared radiation and other effects, it would never actually start boiling.

Hypothetically, of we were water mocules observing our environment, that transition energy might look like a hard barrier with no way to observe the other side. Same idea here, we see masses increase and time slow down based on acceleration, and it appears asymptotic, but there is nothing saying there is not some here yet undiscovered energy level where the fabric of space begins to behave differently and the transition to superluminal velocities becomes possible.

Space is 3D, so we would observe it as shells.

My layman’s interpretation anyway.

dark matter always seemed unlikely to me

Yeah, same. I’ve always assumed (and probably read somewhere, too) that “dark matter” is basically a placeholder for some yet unknown phenomenon/energy/etc.

It doesn’t make sense that we couldn’t see it and the particles that could explain it seemed like they were invented just to justify dark matter

It always seemed like a natural assumption to me: the particles we know about were discovered because they interact with each other via at least one other force in addition to gravity. But there’s no other force common to all particles, so why not expect particles that only interact via gravity? They’d naturally be hard to detect, since gravity is so much weaker than the other forces.

I think he means the very large cosmic strings that appear when you look at the universe on the scale of galactic clusters.
I could be misreading it though.

This was my takeaway from this as well. I’ll have to see if I can locate an Arxiv copy of the full paper, but this just seems more like a thought exercise to explain dark matter using String Theory principles.

Well this one depends on negative mass, which is, as far as I know, no less weird and speculative than dark matter.

I don’t get the reference? lol

Moreover, as the width of the two Gaussians tends to zero, there is no finite spherically symmetric region (be it cavity or shell) over which the integral of ρ(r) yields a resolvably negative mass m(r) and its potentially undesirable consequences.