Dark matter detected?

[DaveR]

Interesting article on the Guardian website re dark matter. Will be really important if verified.

http://www.guardian.co.uk/science/2009/dec/17/dark-matter-detected

[AG Hybrid]

It was only a matter of time. A great find indeed.

[Esseth]

Damn, "The claim, if confirmed next year, will rank as one the most spectacular discoveries in physics (http://www.guardian.co.uk/science/physics) in the past century."

Pretty much covers it, i've been hearing about Dark Matter since i got interested in science... epic indeed.

[gary]

Hi Dave,

Thanks for the link to the article which is also a good piece of journalism.

It certainly is tantalizing and hopefully we will see the published results soon! :thumbsup:

[Robh]

Most interesting!
But we need more confirmation. As stated, the result has a 1 in 4 chance of being due to some other effect in the detectors.

Regards, Rob.

[Ric]

I really hope that they have discovered Dark Matter.

It's these type of discoveries that really give science the shot in the arm that it needs every so often.

Cheers

[michaellxv]

If this turns out to be true does that then mean that they know how to do it and can then refine the equipment to produce more succesful results?

[Baron von Richthofen]

I wonder what is the particle density of dark matter is per cubic meter:question:

[renormalised]

Had to calculate that for my exam this semester. Can't remember the answer offhand, but I'll see if I can find it:D

[Gemini2544]

It's drawing a large bow when you claim to have detected dark matter when now one has ever captured dark matter. How can they prove this...It could also be a new undiscovered element. Without a proven model or physical sample it's still only theory.

If it looks like a duck, quacks like a duck then it must be a duck QED

[sjastro]

The particles are believed to be WIMPS and behave like massive neutrinos.

If it is confirmed as dark matter it is going to mess up the Standard Model of Particle Physics:D

Steven

[Baron von Richthofen]

If you could find out that would be fantastic

[renormalised]

Oh yes:D:D

[TrevorW]

Well I didn't see that one coming

[marki]

I have worked in underground mines and let me tell you it is no suprise that they found dark matter down there. When the lights go out the place is full of the stuff :P.

Mark

[sjastro]

Then we can apply the "The can't prove anything with String Theory" and hey presto DM becomes part of the Standard Model.;)

Steven

[renormalised]

Yeah, large stopes and cutaways you can disappear down really quickly:P:D

Oh, and bat droppings...maybe that's what they found:P:D

[renormalised]

No "hey prestos" in science, Steven. That's magic:P:D

Oh, I forgot, that's what the SM is:P:D

[sjastro]

That's right Carl. When you don't know the mathematics behind the SM it does appear to be magic. :)

Steven

[renormalised]

You know yourself Steven, the biggest criticism of the SM is that it's not entirely without fault itself. In many cases, it's been a matter of finding the particle first then fudging the maths in order to get the new particle to fit the model. The maths themselves are fine (for the given particles, now they've found them), it's the pulling of rabbits out of a hat which many scientists don't like, or would wish wasn't the case. In some cases, it's been things coming out of left of field which has thrown a spanner in the works, Or, like DM, stuff which appears to be real but just doesn't fit in anywhere. The SM needs more than a top overhaul, now. More like a replacement crankshaft;):D

[sjastro]

No Carl it doesn't work that way.:)

Particles in the SM are grouped according to their mathematical symmetries. If you fudge the maths to suit a newly found particle you will destroy the entire model as the symmetries of other particles in the model will no longer relate to their physical properties and interactions.

Steven

[renormalised]

Yes, that's true, however, that's what they've been doing all along when they find something that doesn't fit in with their current SM. They tweak everything in order to make it fit. Or they don't explain it at all. Or if they're good at it, they manage to predict another new particle that fits. That's what I said originally, or at least implied in my last post. What happens if this dark matter they think they've found doesn't fit in with the SM, which is just as likely as it is fitting in. Going to be hard trying to explain something that lies completely outside of the SM. Means the SM isn't standard, does it;):D

It's having no luck with gravity, nor with neutrinos (why they may have mass). And, what the hell happens if they don't find the Higgs, at all. Considering that the SM predicts the existence of the Higgs, having one of its "feature" particles not appearing at all is going to be a tad embarrassing:D But, let's see what happens with the LHC.

What it all means, is that the SM is far from complete and it's probably not even the best theory from explaining all the possible particles and interactions as it presently is.

[sjastro]

The idea that the mathematics is tweaked to get the right answer is creative accounting not science.

Neutrinos with mass illustrates why this doesn't occur. The reason why neutinos with mass are not in the SM is that mathematics doesn't predict their existence. By your line of reasoning all that has to be done is to "tweak" the mathematics.

Unfortunately it's not that simple. As I have already explained tweaking the mathematics will effectively destroy the entire model.

The major problem however it completely flies in the face of the role of the mathematics. Any change to the mathematics reflects a change in the physics. Tweaking the mathematics requires a physical interpretation for the change. That is not achieved by simply changing the maths for the sake of getting the right answer.

Once again the neutrinos with mass problem serves as an example. It is relatively easy to "tweak" the maths to the get the particles into the SM. What scientists are in fact doing are using GUTs (Grand Unified Theories) to explain the discrepancy.

If it works then any change to the maths is justified without compromising the model. It also enhances our understanding.

Finally altering the maths on the basis of predicting an outcome, instead of the outcome itself, violates the scientific method.

It's a classic example of "argumentum ad ignorantiam".

Regards

Steven

[IanT]

If I tried to publish a paper with a 75% chance of the results being incorrect, a journal would reject the paper instantly. In science a 90% or 95% level of confidence in the results is normally required. Physics and astro-physics in particular, seem to have their own rules which do not apply to most other sciences. I'll bet these preliminary findings will form the basis for huge research and infrastructure grants in the next ARC round (which co-incidentally is just around the corner)! Strategic publicity I think.
Ian

[renormalised]

And you don't think there is any "creative accounting" going on in science labs, Steven??.

Yes, the reason why neutrinos with mass aren't predicted by the SM is because it will invalidate the SM as it is at present (i.e. The SM doesn't allow for them). But unfortunately for the SM, it appears that all neutrinos may have mass. And so, they use GUT's to try and explain it, but GUT's of a particular kind. Problem is, if the new physics doesn't appear at around 10^16GeV and those masses aren't what they expect, that'll throw all their calculations right back out the window.

All the SM explains is the synthesis between the EM/weak interaction and the strong interaction. It doesn't explain everything and it certainly draws a blank on gravity. So in the final analysis, it can't be correct as it is. It's only a partially formed theory with big holes in it. Holes which may or may not be plugged depending on the outcomes of experiments of which they're not even sure than can actually perform with the given equipment that they have. They hope their calculations are correct, but that's all it is...hope. They maybe wrong.

So, in the end Steven, they'll just tweak their maths and modify their model in order to suit what they've found. As you said, tweaking the maths means changing the physics to accommodate the change. It may destroy the entire model as it is, and so be it. Whoever said the SM is the be all and end all of particle physics. It's incomplete as it is. Why hold onto something that doesn't fully and elegantly explain all that needs to be explained. Just because a theory or model seems to work up to a point and appears to be correct doesn't mean it ultimately is. There's any one of a number of examples of this in science.

We may have a SM in the future, but it most likely won't be the SM that we have now. That, you can be assured of.

[sjastro]

You have made the grandoise claim that the maths is fudged to get the right answer.
It's now time to backup those claims.
Show me where the maths is fudged, in your own words explain the inconsistancies, and I will debate it with you on a mathematical level.

[Baron von Richthofen]

I am still trying to find out what is the particle density of dark matter is per cubic meter:question:

[renormalised]

Firstly, I'm not stupid enough to debate the maths with an applied mathematician. I may have some grasp of the subject but I am not a mathematician and have never claimed to be. I know enough of the physics to be able to follow the general principles behind the subject and follow the more advanced parts when needed, but I don't claim to know enough to derive them from 1st principles. However, that doesn't mean to say I don't know enough about the subject to not be able to make a comment about tweaking of the maths.

In any case, this forum is not the place to debate principles of mathematics, especially maths as involved as this...you could conceivably take up pages of forum and still get nowhere. Not only that, it wouldn't be fair on the other posters here. Many would, themselves, have even less chance of contributing to the discussion than those of us that do have some grasp (no matter how basic or advanced that might be) of what's being discussed. How would they feel if they wanted to say something and all we were doing is talking over their heads??

In order to unify the EM, weak and strong interactions, they had to take what was known about the particles involved and come up with equations for a theory that satisfied all the characteristics and physical interactions of these particles. They had to fit the model to the known characteristics of the particles and make sure that those characteristics could be explained. Then, once they established a mathematical framework upon which they could base predictions, they could then go look for other particles. Which the SM has been pretty good at, so far.

So, basically the SM was constructed from a set of known characteristics for the particles and interactions they already knew, and they just designed the theory around the already known values, in order to explain them. This was a case where observation and experimentation initially preceded the theory and the theory was tweaked in order to fit the observations. Only later did the theory's predictions precede observations.

Yes, the SM has been able to predict the existence of new particles based on their calculated physical properties, but when you get things like neutrinos having mass (not predicted, not allowed), gravity, dark matter and energy, the matter/antimatter problem, the hierarchical problem and the problems it has with modern cosmological models, then you have to consider that the SM is not a complete theory because if it was, then it would be able to explain the properties of all the particles and their interactions and tie them in with a model that could applied to all situations. If they have found the dark matter they say they have, and they also find conclusive evidence for dark energy, then what are they going to do. Or what happens if the Higgs boson doesn't exist, or it exists but at energies much higher than they expected. What happens if the GUT's theories (which are speculative anyway) they're using to extend the SM w.r.t. the neutrino mass problem are found not to correlate with what they find. What if the neutrino masses aren't as they predict and the energy isn't at the GUT scale predicted. Sort of throws a spanner into the works. Or what if the GUT scale is correct but the neutrino masses aren't. Anything could be found, but we hope that things fit in with theory.

In the meantime, they're going to have to incorporate gravity into the model at some stage. They will have to tweak their equations or come up with some new ones in order to explain what's happening. If that means modifying what they've already got, then that's what they'll have to do. If that also means possibly modifying the physical characteristics or making additions to those characteristics of the known particles, then they will have to.

[sjastro]

You have made specific claims that scientists fudge the maths.
I have responded by stating the nature of the model (and the maths) rules this out as a possibility.

The fact that you disagree would naturally cause the discussion to tend towards a mathematical nature. As you have now admitted to having a limited knowledge of the mathematics, your argument is no more than an assumption that you cannot substantiate.

I am still leaving the door open. All you need to show is one peer reviewed publication that shows the maths was fudged in the discovery of the top and charm quarks, the W and Z bosons, and the gluon.

Regards

Steven

[DaveR]

Again from the Guardian but this time a comment from Paul Davies. Pitched for general readers.
Merry Christmas all

http://www.guardian.co.uk/commentisfree/2009/dec/23/dark-matter-key-understanding-universe