Supernovae evidence for foundational change to cosmological models

https://academic.oup.com/mnrasl/article/537/1/L55/7926647

164 111 2 years ago

academic.oup.com

sylware• 2 years ago

javascript-walled.

thechao• 2 years ago

If the main barrier to your enjoyment of this article is some JavaScript, you're quite a bit heavier weight in the maths department than I'll ever be.

Bengalilol• 2 years ago

<https://watermark.silverchair.com/slae112.pdf?token=AQECAHi2...> I hope it helps

JumpCrisscross4• 2 years ago

Reading this as a layman, it looks like releasing ΛCDM's cosmological principle [1] reveals the nontrivial temporal effects mass clusters have via general relativity. As a result, there could be empty regions of space in which billions of years more have elapsed than in e.g. a galaxy. This not only changes how we interpret supernova data (the acceleration isn't generally happening, but an artefact of looking through space which is older than our own), but may also negate the need for dark matter (EDIT: dark energy) and the meaning of a single age of our univese.

(I'm also vaguely remembering a multi-universe model in which empty space inflates quicker than massed space.)

[1] https://en.wikipedia.org/wiki/Cosmological_principle

aeve890• 2 years ago

Reading this as a layman, it looks like releasing ΛCDM's cosmological principle

You mean relaxing. Also... "as a layman"? Lol what kind of layman are you. Respect.

JumpCrisscross4• 2 years ago

You mean relaxing

Fair enough, at high redshift the cosmological principle could still hold under timescape. (It doesn't require, it however.)

All that said, I'm generally sceptical about findings based on supernova data. They require so much statistical work to interpret correctly that the error rate on first publications is remarkably high.

sesm• 2 years ago

Overturning Lambda-CDM model removes only one observation that is explainable by Dark Matter (peaks in spectrum of CMB). It's not the only observation.

throwawaymaths7• 2 years ago

well the edges of a galaxy are in less of a deep gravity well than the center, so time and thus rotation should go faster. is that enough to account for flat rotation curves? i dont know enough to do a back of the envelope calculation

throwawaymaths7• 2 years ago

here could be empty regions of space in which billions of years more have elapsed than in e.g. a galaxy.

important to note that the motivation for releasing the cosmological principle, is that we know that there are "small" voids and that there is strong evidence of much larger voids and structure on the scale of tens of billions of light years that is incompatible with the cosmological principle, so it's not just a thing to do on a whim, it's supported by observation.

JumpCrisscross4• 2 years ago

we know that there are "small" voids and that there is strong evidence of much larger voids and structure on the scale of tens of billions of light years that is incompatible with the cosmological principle

Two cosmologists debate which of their town’s bars is better, the small one or the large one. The town has one bar.

escape_goat• 2 years ago

Back here on the lay benches, I think the best starting point in the Wikipedia is probably the the article on inhomogenous cosmology, of which the Timescape Comsology proposed by David Wiltshire (listed as an author on this paper) in 2007 is a notable example; it is discussed in the article.

<https://en.wikipedia.org/wiki/Inhomogeneous_cosmology>

Gooblebrai• 2 years ago

This is a mind-blowing theory!

astrobe_• 2 years ago

As a result, there could be empty regions of space in which billions of years more have elapsed

If they are empty, those billion years didn't happen. But nothing is really empty, right?

ben_w• 2 years ago

Assuming I correctly understood the argument in the link:

Even if the space was truly empty, the expansion of that space would have gone on for longer, and thus things on opposite sides would eventually notice they were more distant.

But also yes the space isn't really totally empty.

nine_k• 2 years ago

The higher the density, the more curved is the spacetime at that area, and the slower is the passage of time. You don't have to go to extremes like black holes vs absolute vacuum. A sufficient difference should be visible between regions closer to centers of galaxies, or just clusters of nearby galaxies, and really large "voids" between them, which contain some matter, and even some stars, but are vastly more empty. This is what the article explores.

(This connects in a funny way to Vernor Vinge's SF idea of slower and faster areas of space. The "high" / "fast" space is mostly empty, so the time passes there faster than in the "unthinking depths" around galactic cores, and hugely more progress is done by civilizations in the "fast" space, as observed from the "slow" space.)

pdonis3• 2 years ago

If they are empty, those billion years didn't happen.

No, that's not correct. Here's a better way to look at it:

In our cosmological models, we "slice up" the spacetime of the universe into slices of "space at a constant time"--each slice is like a "snapshot" of the space of the entire universe at a single instant of "cosmological time". The models, which assume homogeneity and isotropy, assume that the actual elapsed proper time at every point in space in each "snapshot" is the same--in other words, that "cosmologcal time" is also proper time for comoving observers everywhere in space at that instant of cosmological time--the time actually elapsed since the Big Bang on a clock moving with each observer.

What these supernova papers are examining is the possibility that "cosmological time" and proper time (clock time) for comoving observers do not always match: roughly speaking, in areas with higher mass concentration (galaxy clusters), proper time lags behind cosmological time (the time we use in the math to label each "snapshot" slice of the space of the universe), and in areas with lower mass concentration (voids), proper time runs ahead of cosmological time. The idea is that this mismatch between proper time and cosmological time can be significant enough to affect the inferences we should be drawing from the supernova observations about the expansion history of the universe.

As far as I know the jury is still out on all this; claims by proponents that what is presented in these papers is already sufficient to require "foundational change" are, I think, premature. But it is certainly a line of research that is worth pursuing.

Keysh2• 2 years ago

there could be empty regions of space in which billions of years more have elapsed than in e.g. a galaxy.

A problem with that idea would be that the ages of galaxies in low-density regions (including voids) tend to be younger than galaxies in denser regions, suggesting that galaxy evolution proceeds more slowly in voids.

https://www.iaa.csic.es/en/news/galaxies-great-cosmic-voids-...

chuckwfinley• 2 years ago

It is sure seeming like LCDM needs some work. It's not really clear if a timescape approach solves the outstanding issues though

incognito124• 2 years ago

Interesting that the following wiki has been updated with this paper:

https://en.wikipedia.org/wiki/Inhomogeneous_cosmology

dgroshev• 2 years ago

Previously (includes informed critique of the paper): https://news.ycombinator.com/item?id=42495703

ckcheng• 2 years ago

Also just 1 day ago: https://news.ycombinator.com/item?id=42587826

Maro2• 2 years ago

Python source:

https://github.com/antosft/SNe-PantheonPlus-Analysis

Input data:

https://zenodo.org/records/12729746

l0b0• 2 years ago

Thank you for sharing! I tried to see if I could replicate the result (unlikely, as I'm not a cosmologist, just a Python developer), but it's not possible:

- They don't share all the input data, including something called "`.FITRES` calibration files" which seem to be necessary - the first command, `python BuildPP.py`, fails because it can't find `Pantheon/calibration_files/FITOPT000_MUOPT000.FITRES`.

- Some code must be meant to be run with a different Python interpreter than the rest, because the syntax is not compatible with the only version mentioned in the project (see below).

The project also has some troublesome but not fatal flaws:

- No exact information about Python version. The only hint I could find was the mention of needing Python 2.7 (two years EOL when the repo was created).

- No information at all about dependency versions. The project needs matplotlib, numpy, pandas, and pymultinest, but there's nothing about which versions of any of these were used for the analysis.

gammarator• 2 years ago

Here’s an extended comment by another astrophysicst: https://telescoper.blog/2025/01/02/timescape-versus-dark-ene...

The most important bit:

The new papers under discussion focus entirely on supernovae measurements. It must be recognized that these provide just one of the pillars supporting the standard cosmology. Over the years, many alternative models have been suggested that claim to “fix” some alleged problem with cosmology only to find that it makes other issues worse. That’s not a reason to ignore departures from the standard framework, but it is an indication that we have a huge amount of data and we’re not allowed to cherry-pick what we want.

throwawaymaths7• 2 years ago

the thing is, this is not really an alternative model. it's rather actually bothering to do the hard math based on existing principles (GR) and existing observations, dropping the fairly convincingly invalidated assumption of large scale uniformity in the mass distribution of the universe.

if anything the standard model of cosmology should at this point be considered alternative as it introduces extra parameters that might be unnecessary.

so yeah it's one calculation. but give it time. the math is harder.

sandgiant• 2 years ago

This has the same number of free parameters as LambdaCDM. Also this result only looks supernovae, i.e. low redshift sources. LambdaCDM is tested on cosmological scales.

Very interesting, but “more work is needed”.

User234• 2 years ago

Calculation is harder in a world of functionally limitless compute is sort of interesting. Where do we go from here?

bsder• 2 years ago

dropping the fairly convincingly invalidated assumption of large scale uniformity in the mass distribution of the universe.

The problem with that is then you need a mechanism that creates non-uniformly distributed mass.

Otherwise, you are simply invoking the anthropic principle: "The universe is the way it is because we are here."

austin-cheney6• 2 years ago

That sounds like regression.

If this problem of regression occurs as regularly as your quote implies then the fault is not in these proposed alternatives, or even in the likely faulty existing model, but in the gaping wide holes for testing these things quickly and objectively. That is why us dumb software guys have test automation.

bubblyworld3• 2 years ago

I think automated hypothesis testing against new data in science is itself an incredibly difficult problem. Every experiment has its own methodology and particular interpretation, often you need to custom build models for your experimental setup to test a given hypothesis, there are lots of data cleanup and aggregation steps that don't generalise, etc. My partner is in neuroscience, for instance, and merging another lab's data into their own workflows is a whole project unto itself.

Test automation in the software context is comparatively trivial. Formal systems make much better guarantees than the universe.

(not to say I think it's a bad idea - it would be incredible! - but perhaps the juice isn't worth the squeeze?)

abdullahkhalids2• 2 years ago

You are oversimplifying science, especially theoretic physics. At the point where we are, there are neither any quick/cheap tests, and there is no objectivity. The space of possible correct theories is infinite, and humans are simply not smart enough to come up frameworks to objectively truncate the space. If we were, we would have made progress already.

There is a lot of subjectivity and art to designing good experiments, not to mention a lot of philosophical insight. I know a lot of scientists deny the role of philosophy in science, but I see all the top physicists in my fields liberally use philosophy - not philosopher type philosophy but physicist type philosophy - to guide their scientific exploration.

uoaei3• 2 years ago

The "shut up and calculate" attitude has done a lot of harm to physics research over the past decades. It is quite remarkable and more than a bit surprising that the primary tenet of general relativity -- that spacetime behaves differently where there is curvature vs where there is not -- was not sufficiently accounted for seemingly by any researchers this entire time.

I am interested to see some retrospective metaanalysis on how many cosmological models have not suffered from this glaring omission. I suspect it's very few but I also think that it would be difficult to do this kind of modeling before we were able to do analysis in silico so there would be an obvious bias in the set of theories.

JumpCrisscross4• 2 years ago

The "shut up and calculate" attitude has done a lot of harm to physics research over the past decades

This is a shut up and calculate paper. There is zero theoretical ground being broken. The meat is in the statistical analysis (which I concede is beyond me).

uoaei3• 2 years ago

This paper is distinct in that it's cogent about the underlying cosmological principles. "Shut up and calculate" poisoned academic physics by eliding the necessity of thinking of systems as systems, and not merely as sets of equations to be manipulated.

ANewFormation• 2 years ago

This is also the biggest surprise for me, but I'd frame it as people largely just handwaving in the assumption of a (at scale) isotropic universe, even though that's highly questionable.

I think the practical issue is that that assumption let a lot more work get done than would have been possible otherwise. Of course if it turns out the universe is not isotropic then most all of that work is worth less than nothing. So publish or perish strikes again?

programjames• 2 years ago

It is somewhat surprising, because one of the most famous papers in chaos theory, "The Applicability of the Third Integral of Motion" (Henon & Heiles), basically starts by saying a similar assumption isn't true, that stars aren't ergodically distributed in the axial/radial directions.

If you have five equations of motion in a six-dimensional universe (3 space + 3 velocity coordinates), you can compute the future trajectory of each point. Two equations come from constant energy & angular momentum, and these constrain where in phase-space the trajectories can go. Another two equations are do not make any such constraints, which implies stars are at least ergodically distributed in a 2D phase-space. Since none of these equations constrain the axial/radial velocity, you would expect the dispersions to be equal for both directions. However, this turns out to not be the case. This means there must be a third isolating equation of motion out there, and the surprising thing Henon & Heiles find is it's chaotic! Sometimes it constrains points to 2D regions of phase-space (i.e. concentric circles of orbits), and other times it lets them move in a 3D region (i.e. chaotic trajectories filling the space).

sampo2• 2 years ago

Also Pioneer Anomaly was solved, after dropping simple models treating the space probe as a simple or spherical particle, and accounting for the 3-dimensional shape of the probe.

Because of the shape of the space probe, part of the thermal radiation emitted from its surfaces were hitting some other surfaces, and thus the probe did not emit radiation evenly into every direction.

https://en.wikipedia.org/wiki/Pioneer_anomaly

caconym_• 2 years ago

It is quite remarkable and more than a bit surprising that the primary tenet of general relativity -- that spacetime behaves differently where there is curvature vs where there is not -- was not sufficiently accounted for seemingly by any researchers this entire time.

This was also my first thought when I heard about this paper. It seems almost impossible that nobody in the entire contentious field of physical cosmology had considered whether our current consensus models account for the relativistic effects of the (known!) large scale structure of space.

Following from that, my second thought was that maybe there is something more subtle about this analysis---maybe the question the researchers asked is less obvious than the headline makes it seem ("we forgot about relativity"). Obviously the subject matter is beyond me to answer that question myself, and I haven't found any good answers elsewhere.

justlikereddit2• 2 years ago

The way I see it people got stuck in a mindset of universal background time that is pretty much what earth clocks run at. With any serious relativity effects only being locally compartmentalized next to extreme cosmic phenomena.

Adding dark matter to this mindset makes it even worse because it homogenizes everything even further towards a Universal Standard Timeframe when 80% of all mass is finely dispersed as a background fog.

Put the Real back in Relativity.

It's by far a more satisfying solution than magic mystery matter.

My pet theory is that black holes are also vastly misunderstood because they're always seen from the Universal Standard Timeframe, if we probe a black hole and their local space from strongly relativistic timeframe they'll start to make more sense, but I'll leave that to the daydreams of the reader.

exe34• 2 years ago

GR calculations are very hard, and it's easy to think the effects aren't relevant outside of extreme conditions. this reminds me of the (sadly not very well supported) paper about gravitomagnetism explaining the rotation curves without dark matter.

sampo2• 2 years ago

It seems almost impossible that nobody in the entire contentious field of physical cosmology had considered whether our current consensus models account for the relativistic effects of the (known!) large scale structure of space.

One of the authors of the present study (prof. Wiltshire) has published this idea first time already 18 years ago: https://en.wikipedia.org/wiki/Inhomogeneous_cosmology#Timesc...

asplake• 2 years ago

It’s early days on this, so let me ask again what I have asked previously: What does timescape do to estimates of the age of the universe?

sigmoid10• 2 years ago

It would mean that we literally can't calculate it anymore, because expansion and everything else we see might just be artefacts of inhomogeneities beyond the scale of the observable universe. But that would crash hard with our observation of the CMB and since this study only looks at supernovae, I would not bet on it holding up for long.

geysersam• 2 years ago

How would

that we literally can't calculate it (the age of the universe) anymore

crash with our observation of the CMB?

I don't see how us being unable to calculate a quantity from one set of observations could possibly clash with another set of observations (the cmb).

What am I missing?

User234• 2 years ago

Even more fun, once you abandon isotropy you don't even need to posit matter inhomogenities. It could just be that spacetime itself has irregular topology.

Which, incidentally, is probably a better theory than dark matter. For example it can produce the same results without the problem of undetectable matter.

block_dagger• 2 years ago

Maybe Vernor Vinge was right.

Vecr• 2 years ago

He wasn't. He stated from the start that all of his stories were gimicked to remove the singularity.

This theory does not do that.

revskill• 2 years ago

Not much related but could we somehow calculate the Gravitational constant with only math ?

jmward012• 2 years ago

The expansion of the universe has always come down to one question for me. In an expanding universe when you throw a ball up what speed does it come down?

pezezin• 2 years ago

My very limited understanding of the topic is that for a gravitationally bound system like the Earth, the usual rules apply, but on cosmological scales the expansion of the universe means that time-translation is not invariant and thus conservation of energy is not well-defined.

https://en.wikipedia.org/wiki/Conservation_of_energy#General...

jmward012• 2 years ago

Getting rid of the time side then, think of it as an orbit. If the universe was expanding then something could be orbiting slower than gravity would allow. Basically this question keeps bringing me back to the ties between mass and the expansion of the universe. No matter how you look at it mass must be special when it comes to expansion because it is either giving off 'free' energy in the form of slow orbits and acceleration between two objects or it -isn't- giving off that energy and something is canceling it out. Following this rabbit-hole is pretty interesting at a minimum.

thomquaid• 2 years ago

if you throw less than escape velocity, about the energy you threw with less system losses. if you throw greater than escape velocity, about any energy is possible less system losses, if you allow enough time for it to come back after its trip around the solar system. if you throw it into the milky way, same thing, easier potentials. if you throw it at relativistic velocities, expansion of the universe could play a significant role.

PaulHoule2• 2 years ago

When I worked at arXiv one of my coworkers was a fresh astrophysics PhD who was cynical about the state of the field. He thought that we didn't know what the hell was going on with accretion disks but that a few powerful people in the field created the impression that we did and that there was no dissent because it was so difficult to get established in the field.

When I first saw the ΛCDM model my first impression was that I'd didn't believe it, it seemed bad enough to have dark matter that we didn't understand (though WIMPs and axions are plausible) but adding equally mysterious and physically unmotivated dark energy made it seem just an exercise in curve fitting.

There have been a longstanding problem that the history of the universe and cosmological distance scale haven't made sense.

https://medium.com/starts-with-a-bang/the-hubble-tension-sti...

When I was getting my PhD in condensed matter physics I was going to the department colloquium all the time and seeing astrophysics talks about how some people thought the hubble constant was 40 km/s/Mpc and others thought it was 80 km/s/Mpc. With timescape cosmology maybe they were both right.

Another longstanding problem in astronomy is that since the 1970s it's been clear we have no idea of how supermassive black holes could have formed in the time we think the universe has existed. With the JWST there are a flood of results that show the first 500 million years of the universe probably lasted a lot more than 500 million years

https://iopscience.iop.org/article/10.3847/2041-8213/ac9b22

colechristensen• 2 years ago

On the topic of early black hole growth I saw this released a couple of months ago, an early black hole apparently growing at 40x the Eddington limit 1.5 billion years after the big bang.

https://chandra.si.edu/press/24_releases/press_110424.html

A super-Eddington-accreting black hole ~1.5 Gyr after the Big Bang observed with JWST

https://www.nature.com/articles/s41550-024-02402-9

dotancohen2• 2 years ago

Correct me if I'm wrong, but the term Eddington limit is a bit misleading as it does not describe some physical rate that cannot be exceeded. Lots of super Eddington objects are known.

somenameforme• 2 years ago

Slightly tangential but how does the ad hoc nature of things like cosmic inflation seemingly not bother more people? Quite the opposite, it's a rather lauded discovery. This is more cosmology than astronomy, but at least reasonably related. That topic alone destroyed my interest in an academic pursuit of astronomy.

'Here's an idea that makes no logical sense, has no physical argument whatsoever (let alone evidence) in support of its existence, and just generally seems completely absurd - but if we ignore all of that, it solves a lot of other pesky problems with reality, as observed, practically falsifying other lauded theories.'

Just add more epicycles?

stouset• 2 years ago

Nobody’s happy with dark energy, it’s just the only framework we have that fits the data. All the other ideas might be brilliant and inspired but are measurably worse at describing the real world.

Even the name “dark energy” is a tacit acknowledgment that—along with dark matter—we have no clue what the underlying physics actually is.

lutorm• 2 years ago

Well, it's not like people pulled it out of thin air. Both inflation and the lambda-CDM models are solutions to the GR equations, so in that sense it's perfectly justifiable to see if general relativity can explain the data. I don't think it's fair to say that it "makes no logical sense".

gosub100• 2 years ago

What do you mean by "bother"? The universe appears to be expanding, so I assume you don't deny that evidence, correct?

Xlr8head• 2 years ago

Most, and I mean scientists and not, don't seem to understand that ALL modelling is curve fitting. Applying maths equations to real data is always thus.

Keysh2• 2 years ago

There have been a longstanding problem that the history of the universe and cosmological distance scale haven't made sense. https://medium.com/starts-with-a-bang/the-hubble-tension-sti...
When I was getting my PhD in condensed matter physics I was going to the department colloquium all the time and seeing astrophysics talks about how some people thought the hubble constant was 40 km/s/Mpc and others thought it was 80 km/s/Mpc. With timescape cosmology maybe they were both right.

You're (mis)remembering a different (old) problem and confusing it with a new one. The problem in the 1970s and 1980s was: what is the local expansion rate of the universe? Where "local" mean "within a few hundred megaparsecs". There were two main groups working on the problem: one group tended to find values of around 50 km/s/Mpc and other values of around 100. Gradually they began to converge (in the early 1990s, the low-H0 group getting values of around 60, the high-H0 group values of around 80), until a consensus emerged that it was in the low 70s, which is where we are now.

The "Hubble tension" is a disagreement between what we measure locally (i.e., a value in the low 70s) and what theory (e.g., LCDM) says we should measure locally, if you extrapolate the best-fitting cosmological models -- based on cosmological observations of the CMB, etc. -- down to now (a value in the upper 60s). This has only become a problem very recently, because the error bars on the local measurement and the cosmological predictions are now small enough to suggest (maybe/probably) meaningful disagreement.

Another longstanding problem in astronomy is that since the 1970s it's been clear we have no idea of how supermassive black holes could have formed in the time we think the universe has existed. With the JWST there are a flood of results that show the first 500 million years of the universe probably lasted a lot more than 500 million years https://iopscience.iop.org/article/10.3847/2041-8213/ac9b22

That's not a "longstanding" problem, it's a problem from the last 25 years or so. In order for there to be a problem, you have to have what you think are reliable estimates for the age of the universe and evidence for large supermassive black holes very early in the universe. This is something that has emerged only relatively recently.

(Your link, by the way, is to a paper that has nothing to do with black holes.)

Maro2• 2 years ago

I was doing an astrophsyics Phd 15 years ago, and one of the many reasons I abandoned it is exactly this. To get published, I would have had to start all my papers introducing and assuming the ΛCDM model, even though it just didn't seem right to me (too many "dark" components, too many assumptions, inflation).

To be fair, people a lot smarter than me think it's good, or good enough.

dmn322• 2 years ago

" He thought that we didn't know what the hell was going on with accretion disks but that a few powerful people in the field created the impression that we did and that there was no dissent because it was so difficult to get established in the field." ... seems to be an epidemic of this stuff in academia tbh.

nimish3• 2 years ago

Finally. We should use numerical relativity and simulate using full-fat GR. Not the half-assed approximations.

XorNot• 2 years ago

Yes I'm sure the problem was no physicist working in the field their entire career thought to just do this.

nimish3• 2 years ago

Well no one bothered to actually implement it so who cares whether they thought it first or not?

SaintSeiya• 2 years ago

The ΛCDM model always felt "wrong" in my gut: dark matter? dark energy? is just the modern equivalent of the aether theory. The fact that is more complex to calculate is not an excuse to prefer the ΛCDM model. The God's theory is even simpler as it spares of any math and physics, yet we do not use it.

cryptonector4• 2 years ago

Most recently discussed in https://news.ycombinator.com/item?id=42587826 ?

Supernovae evidence for foundational change to cosmological models

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