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.
Does a study have to be empirical? I’m not aware of any rule.
When you see study, it’s more statistical analysis of things.
So things like clinical studies doing studies on population of people.
Where this is more publication of a mathematical idea.
Source: have a degree in physics and it’s one of those unwritten rules. Kinda like how English sentences have an order. The soft brown big bunny sounds wired.
I’ve also got a degree in physics and I think it’s a valid if kinda wonky use of the word study. They studied whether or not GR allowed this specific thing and that’s enough to say it’s physically possible. It’s not just publishing an idea so much as proving the validity of it within current models, to me a study implies investigation of some kind and that’s definitely what went on here.
I’ve definitely heard it used this way before, even if it is less common. I wouldn’t say it’s an unwritten rule so much just that people have learnt to infer that there’s some direct observation going on.
Agreed that it’s valid if wonky.
It’s why I compared it to the sentence structure. It just rings a little weird in my ear and that’s why.
TIL.
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.
Is this the sort of negative mass that would possibly allow for stable wormholes and therefore time travel?
I’d recommend Stephen Baxter’s “Ring” novel as a primer on cosmic strings, domain walls (the shell-like mass described here) and using wormholes for time travel.
Basically covers all of the funky science described in this article
It’s also really well written. You’ll have to read the rest of the Xeelee sequence afterwards though
Agreed. My favorite is still Raft
Does this explain the bullet cluster? If it doesn’t, it’s kinda useless.
the current theory is “not by itself sufficient to discredit the dark matter hypothesis — it could be an interesting mathematical exercise at best, but it is the first proof that gravity can exist without mass,” he added.
(Quote by the author of the study himself)
It’s a purely mathematical construct that could explain bending of light without mass.
To be fair dark matter is a purely mathematical construct to explain the presence of gravity without (visible) mass. Certainly dark matter has more credibility than this new idea but hypothetical mathematical constructs make up a good chunk of physics.
Sure, I’m blaming the concerned journalist(s) here. It’s rlly scummy to hype up an evidenceless hypothesis like this. Does injustice to both, the scientists and the public.
But per the definition given involving negative mass, it should be “meassurable mass in the presence of exotic matter”. Anywho…
I mean, cool to prove a theory of massless gravity though, whatever their motivation.
This is so hot ! Thanks 😋
https://en.m.wikipedia.org/wiki/Bullet_ClusterNp <3
You say that about everything
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.
