Physicists Want to Ditch Dark Energy
48 comments
·January 12, 2025pclmulqdq
DoctorOetker
What annoys many was the pretense of a theory. At some point in the history of physics we stopped calling open problems, puzzles and (yet) unresolved paradoxes as what different but similarly unexplained phenomena were called in the past and pretended we resolved them.
It's simply unnecessary to pretend its a theory, it is possible to name things without pretending they are theories.
Filligree
Dark matter in particular strikes me as… “yes, obviously”.
There’s about a dozen quantum fields corresponding to particles. These form a graph, which is by no means fully connected; the fields each interact with a subset of each other, and neutrinos in particular only interact with gravity and the weak force.
If the connections are in some sense random, then it should come as no surprise whatsoever that the graph has disconnected subsets. In fact dark matter theory is effectively stating that the subset we’re a part of is one of many, which also agrees with the copernican principle.
antonvs
That's all essentially true, but it doesn't necessarily mean that there's a quantum field that matches the properties needed to explain the phenomena dark matter is supposed to explain.
It just means that it's plausible, and wouldn't be surprising, if there were such a field.
the__alchemist
I've been doing a deep-dive in the past few weeks of papers and data sets regarding to rotation curves, mass densities etc. (SPARC, papers describing the rotation curves of various dwarf galaxies etc). The impression I get is that most of the authors are not critical of a CDM dark matter halo explaining rotation curve data. The papers I'm reading span from ~1990 to present.
Retric
That seems really time consuming.
One question I’ve had for a while but didn’t seem worth the look is if there any consideration for local gravitational interaction between stars exchanging momentum between them and thus flattening the rotation curve.
I’m assuming that’s one of the first things looked at but couldn’t find a paper on the subject. Remember any references on the topic?
uoaei
Have you seen any work from Stacy McGaugh? https://tritonstation.com/new-blog-page/
the__alchemist
No; checking it out. Ty!
begueradj
Maybe that's the evidence that dark energy and dark matter are the reality which our dark side refuses to admit.
uoaei
Dark matter is and always has been curve-fitting to residuals between theory and data. There is no there there, every map you see is nothing more than subtracting theory from data and having residuals left over. Dark energy is similar except much more coarse, in that the "model" is just a single parameter with a very simplistic interpretation.
Neither are theories, but good luck coming away unscathed when mentioning this in the presence of ΛCDM dogmatists.
Chance-Device
One of the better nautilus articles I’ve read, usually they’re unreadable and boring, despite an interesting title. Unsurprising that it was written by Sabine Hossenfelder. Good science communication is a real skill.
chuckadams
Every science documentary I've watched tells me most physicists want to ditch "dark energy" because it's a placeholder term for something we still don't understand yet. Map-makers didn't actually believe there were dragons after all.
the__alchemist
I've heard the same about Dark Matter, and that was previously my amateur mental model. This was naive; in practice it confidently refers to CDM (cold dark matter), which is matter that interacts gravitationally, but not electromagnetically, with normal matter.
XorNot
That's literally what a placeholder is: it's a description of a suite of observed properties.
Hot dark matter would be a black body emitter - we would see it.
If it interacted electromagnetically then effects like the bullet cluster's gravitational lensing shouldn't happen.
And if it didn't interact gravitationally then we should see normal galactic rotation curves.
floxy
>Hot dark matter would be a black body emitter - we would see it.
Hot dark matter would be stuff like neutrinos and axions which don't interact electromagnetically.
the__alchemist
I think we are on the same page. I was sloppy in my wording; my point is, "dark matter" is not a placeholder for discrepancies in Newtonian simulations of cosmological features with observation, but a placemholder for a type of gravitational-interacting bodies.
andrewflnr
No, hot dark matter would not magically start interacting with the EM field to make black body radiation. I believe the hot/cold dark matter question is entirely about the velocities of the particles.
uoaei
> it's a description of a suite of observed properties
"Looks like matter" is not a property, this interpretation already presupposes a theory that excludes many others that are heretofore still plausible. Physicists tend to ignore those other options, I believe, because of a combination of natural human linguistic biases and the desire for certainty in explanatory models that drives many of us into studying physics. Some get too confident too early and start making dogma their entire academic personality.
andrewflnr
The truncation of the title to remove "These" does severe violence to its meaning.
propter_hoc
The anti-clickbait truncation HN applies to headlines works well in the singular: "This politician wants to ban bicycles" --> "Politician wants to ban bicycles."
In the plural it should probably convert "These" to "Some" rather than implying that "all physicists want to ditch dark energy."
the__alchemist
> This theory has it that all types of energy—including matter, radiation, and pressure—curve space, and the curvature in return influences how the energy-types move. The authors of the new paper, led by Antonia Seifert, don’t question this. They question instead how we use Einstein’s math.
This is so fascinating. I think the principle applies to so much of the natural sciences. GR describes a set of rules (differential equations using tensors) that describe how matter moves in spacetime, and how it curves it. But outside of certain specific conditions (Schwarzschild etc), we can't (yet) use it to build useful models! We can use it to an extent to validate parts of models, but it leaves so much to the imagination. We are still using Newtonian models in cosmology, then applying GR effects like GEM piecemeal, and the time dilation effects in the article, where complexity and understanding allow.
We have these rules, but don't know how to use them to model! See also: Quantum mechanics and ab-initio chemistry. It's as if the universe is written in differential equations, but we are novices at how to use them.
jinushaun
Ah yes, the “cosmological principle” that everything averages out to be basically the same everywhere over large distances. It makes sense that this principle would need to be violated in order to eliminate dark energy.
One of my favorite sci fi concepts is a universe where the cosmological principle was false.
readthenotes1
Alas, the top hits for "timescape" refer to a sci-fi book.
But timescape wiltshire leads to a nice presentation:
https://www.nottingham.ac.uk/physics/documents/talesoflambda...
And without math, https://en.m.wikipedia.org/wiki/Inhomogeneous_cosmology
pk-protect-ai
Why don't they want to ditch dark matter? It is more plausible candidate to ditch :)
moffkalast
> In this timescape model, what we observe in our vicinity, in our own patch, is governed by different laws than what happens on average at larger distances. It is much like how what you observe in your home city may be a poor description for what happens in the world on average.
If a dark matter alternative ends up being an accepted theory, then RelMOND stans are gonna be beyond smug, and well rightfully so I suppose.
MattPalmer1086
No, the laws are the same everywhere. The timescape model just takes into account gravitational time dilation in large voids (where time passes faster). They say this can explain the observation that the universe is expanding faster (in other words, it's not, it just looks like it).
Also, this is about dark energy, not dark matter
moffkalast
Ah right yeah, had them mixed up for some reason.
quantadev
When you run the Schwarzschild radius calculation for the universe (relating mass of a black hole to event horizon radius) you get a prediction that's close enough to the size of the universe and it's mass, so to me that's pretty good evidence our universe is an event horizon.
This means all 3D points in our space are on the horizon itself, and the time dimension is the normal vector to that "surface" (3D manifold). It explains why space is expanding, because Event Horizons always only expand (excluding considering Hawking evaporation of course, which happens too slowly to affect things)
antonvs
Sean Carroll discusses this in "The Universe is not a Black Hole": https://www.preposterousuniverse.com/blog/2010/04/28/the-uni...
Relevant quote:
> "Still, some folks will stubbornly insist, there has to be something deep and interesting about the fact that the radius of the observable universe is comparable to the Schwarzschild radius of an equally-sized black hole. And there is! It means the universe is spatially flat."
rosseitsa
Really curious, how do you quantify "close" in such numeric ranges?
Quick calculations say that ratio is 1.71:1 (https://rentry.co/k85wy696). I guess given the scale of the numbers having such a low ratio is interesting.
But my intuition says that in physics constants are scattered in a sort of logarithmic way, i.e. the orders of magnitude are uniformly scattered in some range. So small ratios between such constants not impossibly rare.
I may be full of shit though!
thrance
Is there any experimental evidence for this model, does it actually lead to any verifiable predictions?
jacknews
I'm not a physicist but both dark energy and dark matter have a definite whiff of 'luminiferous aether' imho.
Of course they're just placeholders for things we don't understand, but my guess is that they are not any form of energy or matter at all, but a misunderstanding of the geometry of space or something similar.
devoutsalsa
Totally! All these ideas are just a placeholder to make a note of something we can observe until we have a better theory.
Luminiferous aether was invoked to explain the ability of the apparently wave-based light to propagate through empty space. [1] Eventually we found evidence that contradicted that idea.
Dark matter is implied by gravitational effects which cannot be explained by general relativity unless more matter is present than can be observed. [2] We are searching for direct evidence, but haven’t found any yet.
the__alchemist
This applies here too: See my comment above; most cosmologists are confident (And/or focus most work on) Cold Dark Matter, e.g. in an ellipsoidal halo around galaxies. I am not making a qualitative judgement, but dark matter is not used in cosmology papers as a placeholder.
danparsonson
It's a placeholder in the sense that we don't know specifically what it is though, right? No cosmologist uses "matter" when they mean "protons" for example.
ggambetta
I've been saying this for at least 6 years [0]. Got downvoted to oblivion back then, glad to see opinions are changing.
elashri
The submission title is edited in a questionable way. Specially that the original one is not clickbait and does fit in the title letters limit.
There is a world of difference between " These Physicists Want to Ditch Dark Energy " and " Physicists Want to Ditch Dark Energy". One is about new model from some physicists and the other implying a conciseness around ditching dark energy.
edit: I didn't know that there is automatic re-write rules for HN. However the fact that the edited title is clickbait now regardless the reason. Just clarifying in case of this is considered an attack on the submitter.
Tomte
It‘ almost certainly Hacker News‘ automatic title rewriting, and not the submitter‘s fault. A missing word at the start is a sure sign.
elashri
That's interesting, I didn't know before that there are re-write rules applied. It seems that this at least a case of when this failed.
null
Dark energy and dark matter aren't really theories. They are sort of the default solution to a set of problems that exist in cosmology. In a sense, every physicist wants to ditch dark matter or dark energy (or at least our current understandings of them), but they just don't know what to replace them with.