Is Dark Energy Getting Weaker? New Evidence Strengthens the Case. (quantamagazine.org) 67
Cosmologists have uncovered stronger evidence that dark energy -- the mysterious force accelerating cosmic expansion -- may be weakening over time. The Dark Energy Spectroscopic Instrument (DESI) collaboration presented their latest findings at the Global Physics Summit in Anaheim, California, reinforcing their preliminary results from last year.
The DESI team analyzed data from approximately 15 million galaxies collected over three years, more than doubling their previous dataset of 6 million galaxies. Combined with supernova observations and cosmic microwave background data, their analysis shows a 4.2-sigma deviation from the standard Lambda-CDM cosmological model, which assumes dark energy remains constant.
"We are much more certain than last year that this is definitely a thing," said Seshadri Nadathur of the University of Portsmouth, a key DESI researcher. These findings align with recent independent results from the Dark Energy Survey (DES), which earlier this month reported a similar 3.2-sigma tension with Lambda-CDM -- a tension that disappears if dark energy is allowed to vary. If confirmed, evolving dark energy could fundamentally alter cosmologists' understanding of the universe's ultimate fate. Instead of expanding indefinitely until all particles become impossibly separated, the universe might follow alternative trajectories.
"It challenges the fate of the universe," explained Mustapha Ishak-Boushaki from the University of Texas at Dallas. "It's game-changing." Moreover, these findings challenge the simplest explanation of dark energy as vacuum energy, which quantum physics suggests should remain constant. Instead, the results indicate unknown physics, possibly involving a new particle, a modification to Einstein's theory of gravity, or even a new fundamental theory. DESI will continue observing through 2026, eventually producing a final map expected to include 50 million galaxies, potentially providing definitive evidence for this cosmic paradigm shift.
The DESI team analyzed data from approximately 15 million galaxies collected over three years, more than doubling their previous dataset of 6 million galaxies. Combined with supernova observations and cosmic microwave background data, their analysis shows a 4.2-sigma deviation from the standard Lambda-CDM cosmological model, which assumes dark energy remains constant.
"We are much more certain than last year that this is definitely a thing," said Seshadri Nadathur of the University of Portsmouth, a key DESI researcher. These findings align with recent independent results from the Dark Energy Survey (DES), which earlier this month reported a similar 3.2-sigma tension with Lambda-CDM -- a tension that disappears if dark energy is allowed to vary. If confirmed, evolving dark energy could fundamentally alter cosmologists' understanding of the universe's ultimate fate. Instead of expanding indefinitely until all particles become impossibly separated, the universe might follow alternative trajectories.
"It challenges the fate of the universe," explained Mustapha Ishak-Boushaki from the University of Texas at Dallas. "It's game-changing." Moreover, these findings challenge the simplest explanation of dark energy as vacuum energy, which quantum physics suggests should remain constant. Instead, the results indicate unknown physics, possibly involving a new particle, a modification to Einstein's theory of gravity, or even a new fundamental theory. DESI will continue observing through 2026, eventually producing a final map expected to include 50 million galaxies, potentially providing definitive evidence for this cosmic paradigm shift.
"The DESI team" (Score:4, Funny)
I'll be sad if there isn't a LUCY team.
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There is.
https://science.nasa.gov/missi... [nasa.gov]
The simple solution: (Score:2, Insightful)
The most simple solution to the problems faced here, is that we don't understand physics. In the same way Newton didn't understand the nature of gravity.
Re:The simple solution: (Score:4, Insightful)
The most simple solution to the problems faced here, is that we don't understand physics. In the same way Newton didn't understand the nature of gravity.
I have this sneaking suspicion that what we don't know about physics outweighs what we know by a substantial enough amount to make us seem like toddlers trying to understand calculus. Especially astrophysics. There's just so much more out there than we can wrap our puny little minds around, and we've likely barely scratched the surface on the experimentation necessary to understand even gravitational dynamics on the scale of galaxies or superclusters. "Dark energy" and "dark matter" today seem to just be placeholders for "all that stuff we don't really have an explanation for yet." And while I look forward to seeing what we actually manage to discover, I don't have a lot of faith in us figuring it out within my lifetime. It's just too vast of a field for progress to suddenly speed up enough to actually sort it out that fast.
Epistemology (Score:4, Insightful)
We know there are gaps, and we can identify specific gaps too. Such as a discrepancy between observation and the theoretical Hubble constant. That doesn't mean the theories are completely wrong, but there are factors that are missing.
Dark energy and dark matter are observed facts. They are not just placeholders, but the names we've given to a phenomena that comes up repeatedly in observations. It would be like being skeptical that lightning exists before it was discovered to be an electrical phenomenon. That lighting exists was never in dispute in the 18th century. Just like that dark matter exists as a phenomena should not be much of a surprise to anyone in the 21st century.
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There is no proof whatsoever that either dark energy or dark matter exist. There are phenomena that are not understood that may be explained by these, but there is no proof for either.
Re:Epistemology (Score:4, Informative)
You misunderstood the above post. There is no proof that they have the same nature as "common energy" and "common matter", but there is overwhelming observational evidence that the universe doesn't behave as the Standard Model of cosmology predicts it should given the known amount and distribution of mass in the universe. That discrepancy between what is predicted and what is observed is called "dark matter", and you can't deny that the observations exist.
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Quote:
"Dark energy and dark matter are observed facts. They are not just placeholders"
They are not observer facts and they are just placeholders. There is plenty that we don't understand, these have been proposed as solutions. Many proposals have been made for any number of things throughout history - most were wrong. "We call this thing that we have no idea what it is 'dark matter' because we have observational issues with galactic rotations". "We call this thing that we have no idea at all what it is
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They are not observer facts and they are just placeholders. There is plenty that we don't understand, these have been proposed as solutions.
You seemed confused about the situation. Why do you think we have "proposed solutions" if there were no observable facts? There are observable facts; you just refuse to acknowledge they exist. Over a hundred years of observable facts suggest dark matter is real.
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I'm sorry, but your reply makes no sense at all.
You quote me as saying that there is plenty that we don't understand and that these have been proposed as solutions, but then somehow make the bizarre leap to me not acknowledging that these things exist.
Then you go on to say:
"Over a hundred years of observable facts suggest dark matter is real."
Yes, things are happening that we have no explanation for. Go science, figure it out. Because after a hundred years, we still have no idea. So 'dark matter' is syno
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You quote me as saying that there is plenty that we don't understand and that these have been proposed as solutions, but then somehow make the bizarre leap to me not acknowledging that these things exist.
Only you haven't thought about the situation clearly. Your assertion is that we have no observable facts yet we have proposed solutions. What are we trying to solve if there are no observable facts? That's like me proposing a solution to my current problem of a leaky faucet but I have never observed my faucet leaking.
Yes, things are happening that we have no explanation for. Go science, figure it out.
We do not have full explanation. You keep asserting we have zero information. We also know dark matter and energy are not regular matter or energy
Because after a hundred years, we still have no idea. So 'dark matter' is synonymous with "well, we have to call it something, but really we have no idea what it is".
Again, not having FULL explanation is not the s
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"Over a hundred years of observable facts suggest dark matter is real."
Equally so, how can the observed facts be "of" dark matter if in fact they only "suggest" it is real?
I'm not trying ot be awkward - most of physics is like this. We almost never observe the thing directly. Most often that would be impossible. So we observe an effect that we think the thing, and if done under the right conditions we take that secondary observation (of the thing's effects, rather than the thig itself) to be evidence for th
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Equally so, how can the observed facts be "of" dark matter if in fact they only "suggest" it is real?
I think the poster above is objecting to the semantics of what you're saying. My reading of it is that s/he doesn't disagree that there are observaitons of discrepencies in the galactic observations, and that these discrepent observations suggest (strongly, and almost exclusively) that dark matter is the cause, but this is not the same as saying "Dark energy and dark matter are observed facts".
No, in this post and in another post, the poster is specifically saying "there is no proof" and "there are no obser
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ChatGPT said: "Suggested Refinement:
If you want to make a similar point but avoid the gotcha tone, you could say:
"If future discoveries showed that another forceâ"such as electromagnetism or a modification to gravityâ"explains galaxy rotation curves without needing dark matter, how would that change your perspective? Would you still consider dark matter the best explanation, or would you be open to alternatives?"
This way, you still challenge the assumption but invite an open-ended discussion rathe
Re:Epistemology (Score:4, Informative)
The mass-to-light ratio is an observe fact that anyone can independently verify. There are really two choices, that General Relativity is horribly wrong by a few orders of magnitude. Or that there is a mass that cannot be accounted for, and we can confirm that it's not Baryonic matter. (that's complicated). At the end of the day, DM is observed to be ubiquitous in gravitationally-collapsed structures, from the galaxies equivalent in size to Milky Way to the smallest known galaxies.
So no. It's not a placeholder. It's not a theory. But we also do not have a complete explanation for what we observe. It's important to keep in the front of our mind that we keep seeing this and that it exists. And the next step is of course to find the underlying cause and mechanism.
A somewhat long but informative video covers it pretty well for the layperson: dark matter is not a theory [youtube.com]
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I agree, it is not a theory, it is a postulate. It irks me in the video that you linked when the person refers to 'the theory'. There is no theory. There is an observational basis only. To get to the level of 'theory', a strong mathematical and experimentation basis have to be developed.
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" DM is observed to be ubiquitous in gravitationally-collapsed structures, from the galaxies equivalent in size to Milky Way to the smallest known galaxies."
ChatGPT says:
Not entirely. While dark matter is inferred to be present in most galaxies, the claim that it is ubiquitous in all gravitationally collapsed structures is an oversimplification. There are notable exceptions:
Galaxies with Little to No Dark Matter
Some galaxies, like NGC 1052-DF2 and NGC 1052-DF4, show velocity dispersions too low to require s
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There are really two choices, that General Relativity is horribly wrong by a few orders of magnitude.
False Dichotomy. Newtonian Physics works pretty darn well for a lot of situations, is simple, so much so, we still use it because it is practical. But it is wrong.
For all we know, Einstein's equations may be suffering the same basic problem, we just haven't figured out why it isn't working where we see it not working as expected. But it works for a large number of scenarios that it is still usable.
That is my current working theory ;-)
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There is no proof whatsoever that either dark energy or dark matter exist. There are phenomena that are not understood that may be explained by these, but there is no proof for either.
By "no proof" do you mean we have over a hundred years of evidence [youtube.com] for dark matter? The first evidence was from Lord Kelvin in 1884. Remember science is not math; evidence, not proof, is the measure to evaluate. Granted we do not have full understanding about the nature of dark matter today. That does not mean we do not have evidence.
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If your statement is:
"Something that we do not understand is clearly happening, but we have no idea what is causing these things. Let's just all it 'dark matter' for the time being".
Then I have no problem with that. If 'dark matter' is just a placeholder term, and nothing more, than that is fine by me.
And, btw, the link to Dr. Becky, she states that we have no idea what dark matter is. Simply that this question has been unresolved for a long time.
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"Something that we do not understand is clearly happening, but we have no idea what is causing these things. Let's just all it 'dark matter' for the time being".
Your original statement: "There is no proof . . . " is factually incorrect. We have evidence. Over a hundred years of evidence. We do not have full understanding. You keep confusing evidence with full understanding. They are not the same thing.
And, btw, the link to Dr. Becky, she states that we have no idea what dark matter is. Simply that this question has been unresolved for a long time.
Again we do not have full understanding. We do know it is not normal, baryonic matter. We have over a hundred years of evidence.
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Yes - exactly. Now you understand. We have over a hundred years of observations that can not be explained. This is evidence that there is something that is not explained. In fact, my original statement is exactly correct:
"There is no proof whatsoever that either dark energy or dark matter exist. There are phenomena that are not understood that may be explained by these, but there is no proof for either."
By proof, I mean either experimental, errr ahhh what's the word, oh "evidence". Show me one experim
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Yes - exactly. Now you understand. We have over a hundred years of observations that can not be explained. This is evidence that there is something that is not explained. In fact, my original statement is exactly correct:
No. You said "there is no proof". That is false. You did not say, 'there is no explanation."
By proof, I mean either experimental, errr ahhh what's the word, oh "evidence". Show me one experiment.
Wow you understanding of science is lacking. Experiments is not the totality of evidence. Observations are also evidence. You seem not to understand that. By your logic, none of planets in this solar system exist because we have not created one in an experiment as we can only observe them.
Show me one theoretical framework. There are none.We call the things that have been observed for over a hundred years that can not be explained by any theory or experiment "dark matter".
You logic is completely binary. If we do not have full explanations for something, they do not exist in your world. We have eviden
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You are right but I think we are now just getting very smart people to make up mathematics that matches what we see as opposed to actually understanding it. Dark matter and dark energy seem to me to be just oh our models don't quite work lets just add this then say it works. We know something is missing but we are stuck on what and it doesn't seem to me that these this are particularity good solutions.
Re: Epistemology (Score:2)
Dark matter and dark energy are absolutely not facts. Theyâ(TM)re are things we canâ(TM)t explain in the universe today that currently seem best explained by the existence of more matter that we canâ(TM)t see; and some energy causing inflation to accelerate, but there are absolutely alternative explanations that donâ(TM)t need those things to exist. One competing theory to dark matter is MOND where instead of claiming that thereâ(TM)s more matter we claim that Newtonâ(TM)s la
Re: The simple solution: (Score:5, Insightful)
"Dark energy" and "dark matter" today seem to just be placeholders for "all that stuff we don't really have an explanation for yet."
Not "seem", that's literally what they are.
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Well kinda yeah
There's basically two things which are odd that we absolutely definitely do not understand. Firstly galaxies rotate faster then we expect based on what we can observe in them. Secondly, the universe appears to be expanding ever faster where you'd expect the opposite to be the case as gravity pulls it back together.
The former has alternative hypotheses, like MOND. But invisible mass so far fits the observations better than MOND, so it's regarded as the best hypothesis.
I'm the second case, well
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The former has alternative hypotheses, like MOND. But invisible mass so far fits the observations better than MOND, so it's regarded as the best hypothesis.
The problem for MOND is while it provides a possible solution without invoking dark matter, it fails to adequately explain known phenomena like relativity, gravitational lensing, cosmic microwave background radiation, etc. As such, few astrophysicists work on it as there are many problems to overcome.
Re: The simple solution: (Score:2)
That, and there are some galaxies out there that *do* rotate at the speed we expect them to, or that rotate faster. Those observations seem to require something that can vary locally (like the amount and arrangement of dark matter), rather than one universal cosmic rule.
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That's not a solution. That's giving up.
They're chasing this because they don't know what dark energy is. Scientists didn't stop trying to understand gravity after Newton's description, and they didn't stop after Einstein produced a better one. And for whomever figures out dark energy (if anyone does), scientists aren't going to stop with that.
Re:The simple solution: (Score:4, Insightful)
The phrase that most often leads to scientific breakthroughs in our understanding of the universe isn't "Eureka!", but rather, "Huh... that's weird..."
Finding out that our models fail at a spot we didn't expect them to fail helps us to create more comprehensive theories that better explain the things we don't understand.
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"Eureka!" and "That's weird" occur at different points. "That's weird" is where you start looking for a new anwser, "Eureka" is when you find an answer that fits all your data.
(Yeah, it's a nice quote, but it's wrong.)
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Scientists also came up with more incorrect explanations than correct ones.
Re: The simple solution: (Score:2)
Infinitely more in fact. The key is that each explanation is more correct than the last.
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How do you know you're not in an epicycular trap?
Someone said in another comment: "But so far no one has cone up with an explanation which fits the data better [...]"
For how long did epicyclists say that?
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They're chasing this because they don't know what dark energy is.
They are trying to figure out why their mathematical model of the universe doesn't add up. "Dark energy" is just a number to plug in to make the model work. My bet is that this is a little like the complicated formulas used to explain how the sun and stars rotate around the earth.
Re:The simple solution: (Score:5, Informative)
The most simple solution to the problems faced here, is that we don't understand everything about physics. In the same way Newton didn't understand the nature of gravity in all circumstances.
FTFY. Certainly we understand many things about physics and Newton understood the nature of gravity but not in a relativistic frame.
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That is definitely not the simplest solution.
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"n the same way Newton didn't understand the nature of gravity."
And you think we do?
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Richard Feynman said the same about Quantum Physics back in the 1970ies. And still, we can handle Quantum Physics with a precision which allows LIGO and measuring changes of the magnitude on a thousandth of a proton's diameter. I don't have any issue with the "not understanding" part, as long as the predictions we make work out.
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As my humble zero-analysis Dunning-Kruger take... (Score:1)
... it certainly sounds like dark energy and cosmological inflation might be the same phenomenon, representing a single field or mechanism which weakens by many orders of magntiude with respect to time/density.
Anyone here have any less-Dunning-Kruger takes on the topic? :)
Unknown but Interesting (Score:2)
You can develop theoretical models that connect the two - for example
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My take:
They're parts of the same process in the current models. The inflation is what we see signs of (as in measured distances to supernovae, etc.). Dark energy is how the inflation is explained.
The thing that bothers me is the big bang itself. I don't see how inflation can explain getting through a Schwarzschild barrier, the big bang was clearly dense enough to put the universe within that barrier, and I've been assured that we can't be living within a black hole. ISTM that ONE of those has to be wro
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I don't see that as a problem at all? Surely the expansion of space (or something that creates the effect that's perceived as the of the expansion of space) directly offsets inspiraling, no? Surely if inflation is sufficiently high at such extreme mass densities, there's no barrier at all, no?
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That would work if the universe being inside a black hole were possible. But I've been told that that's not compatible with current theories.
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I didn't understand the explanation. Actually I've had a least two different explanations as to why that wasn't possible, and didn't understand either of them, but one of them was by someone that I trust to know what he's talking about. (And possibly both explanations were the same reason from different approaches.) It's been too long since I've even looked at tensor calculus, so I *can't* form my own opinion, I have to rely on someone else's..
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You'd have to have a pretty weird curve describing its strength. It would almost certainly require fewer parameters to just have separate fields.
Weaker consistent with primordial black holes (Score:2)
Back in the mid 80's when I was working on my degree I had discussions with professors about the implications of Hawking Radiation (evaporative black holes), primordial black holes (created as part of the immense pressures a tiny fraction after the big bang) and quantum relativity. It pains me when dark energy was first proposed I never thought to consider that primordial black holes could be the source.
If they are, which has recently been proposed, than you would predict that the strength of dark matter/e
From my layman perspective after 2 beers :D (Score:1)
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Seems dark energy was/is highly suspect to begin with. A compensation, to another compensation and now they even need variation in dark energy to make it all fit. Seems dark energy is a completely wrong approach. YMMV.
Then how do you explain the decades of evidence that there is an energy that physicists cannot directly measure but seems to fit the data that exists?
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Dark energy is the observation that the best fit line on this graph has a greater slope than expected:
https://www.e-education.psu.ed... [psu.edu]
Variable dark energy is the observation that the line might actually be a curve.
Dark energy isn't an "approach." It's an observation.
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Variable dark energy is the observation that the line might actually be a curve.
Or a straight line with a slope that changes over time.
Here's an idea:
1. Our universe exists within a black hole.
2. There is probably "something" outside this black hole (an accretion disk in the higher order universe, for example).
3. The effects of this external matter influence the curvature of the space within our universes black hole.
4. Over time, the matter in this accretion disk changes (ejected, whatever) in that higher order universe, changing the curvature of our space.
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> Or a straight line with a slope that changes over time.
You MAY want to look at an elementary-level geometry text and see if you can find a definition for 'straight line' and 'curve'.
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The x axis on that graph is effectively "time." So something that changes in strength over time will trace out a curve. Something that is constant in time will be straight. "A straight line that changes slope over time" doesn't make sense.
Vacuum energy (Score:2)
Getting weaker because the bag is full.
Should have named is Dark Fudge. (Score:1)
That fudge now has curves.