Breakthrough Announced in Dark Matter Detection Technology
washington.edu
washington.edu
>t is the world’s first and only experiment to have achieved the necessary sensitivity to “hear” the telltale signs of dark matter axions. This technological breakthrough is the result of more than 30 years of research and development, with the latest piece of the puzzle coming in the form of a quantum-enabled device that allows ADMX to listen for axions more closely than any experiment ever built.
Basically, is the purpose to announce that a new higher-fidelity device has come online? If that's the case, I feel mildly bamboozled... creation of a newer, better tool doesn't to me indicate any new "discoveries" regarding dark matter.
I'm pretty bad at understanding anything "physics" above the most basic classical stuff though so it's very possible I'm totally off base here.
“This result signals the start of the true hunt for axions,” said Fermilab’s Andrew Sonnenschein, the operations manager for ADMX. “If dark matter axions exist within the frequency band we will be probing for the next few years, then it’s only a matter of time before we find them.”
Basically this is a new experiment about to begin operating. If nothing goes wrong, within a few years we'll be able to confirm or reject the axion theory of dark matter. Which is pretty big news, all told. A confirmed axion detection would be at least as important to physics as the Higgs result from CERN or the discovery of the W/Z in the 80's.
Well, we'll be able to reject the current axion theory of dark matter. I suspect we won't be able to reject all possible ones. (But I don't know for sure.)
So not speciously true of all predictions or most (before String Theory came along!)
It's written by someone more interested in conveying truth than hyping a null result, so it even mentions a woman was involved in inventing it! (rather than the copywriter who instead just mentions the man that gave it a name).
[1] https://en.wikipedia.org/wiki/Bullet_Cluster
[2] https://en.wikipedia.org/wiki/Dark_matter#Cosmic_microwave_b...
http://backreaction.blogspot.com/2018/04/no-that-galaxy-with...
As a non-scientist, it seems like dark matter has been relentlessly adjusted and overfitted and still appears very inadequate to fit all the evidence.
Some do, but they're in the minority (which, to be clear, doesn't necessarily make them wrong). You can find scientists who refute climate change, too. That says nothing of the state of prevailing consensus, though.
That's an appeal to nature as well as a false equivalency. It is difficult to refute climate change because we have incredible amounts of tactile observations that match predictions - the stuff from which the scientific method stems.
At one point science (well, philosophy as the progenitor of science) said that the Earth was flat. It was a small number of rebellious scientists that corrected this misconception. Group-think and consensus do not mean that you are correct, it could mean that you are collectively wrong.
We've never seen dark matter. The so-called "evidence" that is continuously regurgitated[1] is an image of the problem. It would be like making a map of the missing periodic table of elements and calling it all "Dark Elements," never bothering to figure out what the missing elements individually are. We didn't do that, which is why we can do so many useful things with heavier elements today.
If axion decay is observed, I will have no choice but to agree with the WIMP theories. As it stands, there is zero credible and scientific evidence for the stuff.
[1]: http://www.esa.int/spaceinimages/Images/2007/01/3D_map_of_da...
This article is literally about the development of new sensor technologies designed to make that kind of progress for dark matter.
It seems you just have a chip on your shoulder and a complete misunderstanding of the concept of dark matter.
Which is exactly what the last paragraph in my comment addresses.
And yet people try. If this were a discussion on climate change, someone could link to a scientist trying to refute it and say "some disagree." We both agree that linking to a single blog post that refutes climate change would be unconvincing. Why hold this topic to a different standard?
> The so-called "evidence" that is continuously regurgitated is an image of the problem.
That's what evidence is, isn't it? Then scientists get to solve the mystery that's revealed by the evidence. Just like detectives solve a crime based on evidence at a crime scene. Evidence can precede answers.
Having evidence doesn't mean we've figured out what dark matter is. It means we can put constraints on possible explanations. So far, scientists have ruled out several theories, because they don't fit the evidence.
> As it stands, there is zero credible and scientific evidence for the stuff.
If there were no evidence, there wouldn't be a mystery to solve.
Agreed. I didn't mean to imply that dark matter is a solved problem. In fact, I'm pretty sure I implied the exact opposite when I said it "doesn't necessarily make them wrong."
> Dark matter may be popular but only because it is currently the best theory that fits
Exactly. That's a pretty good reason to favor one theory over another.
Unfortunately you're missing the thrust of Hossenfelder's developing argument: in upgrading MOND to a full relativistic theory, you necessarily seriously blur the difference between "modified gravity" and "particle dark matter".
There's some meat on this in the comments on that blog page, notably the point raised (and her subsequent reference to it) by "M_Malenfant".
Essentially her point is that when you relativize some theories of MOND (detailed examples in Famaey & McGauch https://arxiv.org/abs/1112.3960 section 7) you are inevitably adding a field to the existing fields. Whether you put it on the right or the left of the Einstein Field Equations is a matter of personal taste. The thoretical requirements however are that the field couples with matter somehow (even just gravitationally), just like the particle dark matter case (where particles may interact weakly or even just gravitationally). Moreover, when you have a dynamical, relativistic field like this, you tend to think of how to quantize it, which typically means particles as the field content and particles mediating the interaction between that and the field content of the Standard Model.
So, as she says, perhaps it's more a question of sociology than mathematics that splits particle dark matter theorists (solving cosmological problems like the details of the cosmic microwave background and its neutrino equivalent, or solving problems with the Standard Model like the QCD strong CP problem) or from modified gravity theorists (solving velocity curve problems). At some level, almost all of the still-viable proposals for these and related problems boil down to adding a field on curved spacetime.
On the other hand -- and this is where Hossenfelder (among others) deserves some credit -- this wouldn't have been quite so obvious ten or so years ago, let alone in the early 1980s when Milgrom began developing MOND.
In general, I'm suspicious of dark matter. It would make an interesting development if it ended up being the planet Vulcan of our time, where we doggedly postulate its existence despite mounting counter-evidence because it's unpleasant to question baser theories.
Chandra data for the Bullet Cluster is from 2004; it was a crisis for then non-relativistic MOND, precisely because the Bullet Cluster is manifestly a relativistic, dynamical system. It is not now a crisis for appropriate relativistic theories of "modified gravity" where an additional field is added to General Relativity (again, see Famaey & McGauch 2011 -- section 8.3 is directly relevant) where in the non-relativistic and static limit (with some additional symmetries) the MOND interpolating function is recovered. This was tremendous progress, but leads ineluctably to the question: what is really the difference between adding a vector or scalar field on one side or the other of the EFEs?
The result: convergence on the idea that there is some field content that drags on luminous matter. We already had that with particle dark matter, with the main disagreements being the nature of the field (WIMPs vs axions etc.). Now it's more a question of how to do an initial values formulation that concords with available evidence. For straightforward particle dark matter, that's really easy once a candidate is found in a lab experiment. For less straightforward particle dark matter -- and for "modified gravity" fields on curved spacetime -- it's not so obviously easy, but almost certainly easier than was believed in 2004!
In all cases, structure evolution simulations are possible today that were undreamed of in the 1980s when MOND and CDM were first proposed.
> suspicious of dark matter
There can't be many people whose job -- or even calling -- it is to convince you personally of anything rather than, say, look for evidence to further constrain the CDM parameter space. However, I'm sure you could arrange something. You seem to like Bee, so perhaps http://backreaction.blogspot.com/p/talk-to-physicist_27.html is worth a shot.
Welcome to physics. The Copenhagen Interpretation is the most concise and robustly tested theory in all of physics. Yet it was dreamt up by a literal absurdist who thought that the universe itself has no objective state of existence. For all we know about the universe, we can still not answer many of the most basic questions about it. The lesson to be learnt from this is that our greatest theories are at best woefully incomplete, and that even our greatest scientists don't have the ability to talk about many things with any level of objective certainty.
I’d also argue that you’re substituting “basic” for “fundamental” and that’s bordering on dishonesty. We don’t have answers to some of the. OST fundamental questions, assuming we’re even asking the right questions, but the basics are well covered.
QED works quite well in most cases, but only if you don’t look too closely, and only if you ignore one of the fundamental forces. QED offers no explaination for gravity, which even non-physicists know exists.
What is gravity? What is a particle? What is space? These are all quite basic questions that were not even close to having complete answers for. QED provides a “good enough” explaination for how particles and space work, just as relativity gives a “good enough” explaination of gravity. But any physicist who’s being intellectually honest knows that we only have a rudimentary understanding of these concepts. The wave function is just an excellent tool we use to smooth out our lack of understanding. Your comment is a perfect example of the arrogance that pervades the scientific community, and the inability to acknowledge the limits of our own understanding. Which I think only inhibits the wider community’s ability to communicate effectively with the general public.
Fundamental = bedrock
QED works to the best ability of any test, down to one part in ten billion, so looking very close indeed. Then in order...
What is gravity? The geometry of spacetime.
What is a particle? A localized excitation of a field.
It may be that you don’t like or understand the answers, but they exist and allow people to make precise predictions, build machines that work based on said principles. Maybe you’re confusing scientific answers with philosophical ones?
Adjective
1. forming an essential foundation or starting point; fundamental.
Your answers to those questions are either deliberately over-simplifying to avoid the question, or you don’t understand QED yourself. Your definition of a particle describes a possible outcome of a measurement, and ignores the existence of a wave function. Your description of gravity cannot be created in QED. You have provided no explanation of space whatsoever, which is so woefully unexplained by quantum mechanics, that it is referred to as the ‘vacuum catastrophe’.
Anybody who investigates these concepts can see that our understanding of them is woefully incomplete. However scientists tend to have a very hard time acknowledging these limits of our understanding, and will often respond to such acknowledgements with thinly veiled contempt. Just as you have done by trying to undermine my opinion on them, rather than responding to what I have said. I think that by failing to acknowledge the limits of scientific understanding, maybe you are confusing science with religion?
That couldn't be further from the truth. Scientists have been very upfront about the limits of our understanding, particularly when it comes to combining gravity with quantum physics. Listen to Neil DeGrasse Tyson or any other science communicator talk about general relativity or quantum physics and you'll hear them drive this point home.
We know that quantum physics and general relativity don't combine well, yet both are among the most thoroughly tested theories in science. We know we need new physics to combine them, but they're still useful in their own domains. Just like before we had general relativity, we knew that Newtonian gravity was incomplete because it didn't correctly explain the orbit of Mercury. But Newtonian gravity was (and is) still useful, even with those limitations. The key is knowing where the limitations apply.
General relativity applies to scenarios of high mass/energy. Quantum physics applies at small scales. They both work great in their respective domains. It's when you have high mass/energy in a small volume that things break down, because both quantum physics and general relativity apply, but we don't know how to combine them.
> I think that by failing to acknowledge the limits of scientific understanding, maybe you are confusing science with religion?
I don't see dbasedweeb failing to acknowledge anything. dbasedweeb wrote, "incomplete in very extreme conditions such as the interiors of black holes or the first instants after the Big Bang," which happen to be two places where quantum physics and general relativity are both applicable and we therefor run into the limitations that I mentioned above.
You're right that there are examples of scientists who highlight these gaps in our knowledge, there are more who simply pay some lip service to them, and then there's a much larger group of people, like dbasedweeb, who irrationally suppress all criticisms of scientific theories as if they were literally religious beliefs.
And yet you seem to think that when it comes to physics, this same rule won’t apply. If you really care about the subjects you’re talking around, take some intro courses, really learn about it, or accept that you can only bullshit people who know less about the subject than you.
Phrases like, “the basic nature of our universe” sound good if you don’t know the first thing about the topic at hand, and probably impress people with no education or experience on said topic. To others, they’re huge giveaways that you don’t know what you’re talking about. Other red alerts are, “What is space?” “Empty space” and broad, substance-free critiques.
If you care about the subject and not just projecting a particular image of yourself, then bother to actually learn about them beyond the level of pop science. Critiquing something you demonstrably don’t have a deep knowledge of is a pointless exercise unless you’re just trying to impress people who know even less about it than you.
Here are some resources.
Intro To SR: https://ocw.mit.edu/courses/physics/8-20-introduction-to-spe...
Intro to GR: http://www.staff.science.uu.nl/~hooft101/lectures/genrel_201...
Further reading on GR: Gravitation by Misner, Thorne, Wheeler.
Intro to QED: http://sophia.dtp.fmph.uniba.sk/~peterp/QED_A.pdf
http://hepwww.rl.ac.uk/hepsummerschool/Evans%2008%20Intro%20...
https://www-thphys.physics.ox.ac.uk/people/FrancescoHautmann...
Intro to QFT: QFT Demystified is a great starting point...
Quantum Field Theory by Claude Itzykson and Jean-Bernard Zuber
Anything by Zee, especially “For The Gifted Amateur”
It does; gravitation in perturbative QED on time-dependent curved backgrounds has exactly the same explanation as General Relativity. [1] This generalizes very well. [2]
One can look at it the other direction too: General Relativity guarantees flat spacetime in the neighbourhood of every point on the manifold with signature 1,3 or 3,1. As long as the radius of curvature is large compared to the system under study there is no trouble at all (QED systems are usually pretty tiny, so you're good down to and through astrophysical black hole apparent horizons). This is implicit in laboratory tests of QED.
> But any physicist who’s being intellectually honest knows that we only have a rudimentary understanding of these concepts
Everyone should be honest about how much she or he really knows, and how much he or she can judge how much someone else really knows.
"The first principle is that you must not fool yourself — and you are the easiest person to fool" -- Feynman
- --
[1] [BirrellDavies] N.D. Birrell and P.C.W. Davies, Quantum fields in curved space, Cambridge University Press, Cambridge U.K. (1982).
[2] [BGZV] A.O. Barvinsky, Yu.V. Gusev, V.V. Zhytnikov, and G.A. Vilkovisky, SPIRES-HEP:Print-93-0274(Manitoba), (1993). https://arxiv.org/abs/0911.1168
That’s science working as intended, or as people here like to say, a feature and not a bug. The more a theory has to make assumptions or introduce things like new particles and fields to make predictions, the less popular it tends to be. Of course once you constrain the solution space to the point where the simplest theories can’t hold, you have to consider the more complex ones. The important thing to remember is that none of this happens in a vacuum, and while personal preferences play a role, they do so only insofar as the constraints placed on theory by observation allow for it.
Incidentally that’s also why falsifiablility is such a big deal, because in its absence you can assert or believe any old thing.
Essentially they can ringfence the potential masses/energies of axions based on other things, if they exist, this device contains a resonant cavity that should be able to detect them breaking down across most of the theoretical energy range