Bringing WIMP Theory into Question: Is There Another Dark Matter Explanation?
Written by Ian O'Neill
Weakly Interacting Massive Particles (WIMPs) are thought to dominate dark matter and huge efforts are under way to detect them. By their definition, WIMPs are massive theoretical particles, and they are very weakly interacting with normal matter. WIMPs are therefore notoriously difficult to detect, if they exist that is.
However, some physicists aren't so confident that WIMPs are key to the hunt for dark matter. In a new study, two US researchers have re-opened the debate about dark matter, suggesting the bulk of it could be composed of heavier, strongly interacting particles, or possibly smaller, even more weakly interacting particles than WIMP theory. The physicists also go as far as suggesting that the Universe would be an even more interesting place where WIMP-less dark matter dominates…
"We know little about dark matter, since we can't measure it directly," said Jonathan Feng, a physicist at the University of California, Irvine. "But there are theories and models. WIMPs are attractive because they happen to appear in many popular theories of new particles and interactions. But what if there are other well-motivated possibilities for dark matter besides WIMPs?"
Feng, with co-author Jason Kumar, published a paper in Physical Review Letters called "Dark-Matter Particles without Weak-Scale Masses or Weak Interactions," and the results have called into question the validity of focusing on WIMPs as the main component of the dark matter thought to make up the majority of mass in our Universe. The problem with dark matter, as stated by Feng, is that we cannot measure (observe) it directly and we therefore have little clue what it is. We know it's there, the motion of galaxies and galactic clusters indicate a gravitational influence of something other than what we can see (i.e. luminous matter), but dark matter does not interact via the electromagnetic force, making it a particularly difficult entity to study.
There are strong theoretical reasons to believe WIMPs are at the centre of dark matter studies, but Feng and Kumar have composed models that suggest other weakly, and strongly, interacting particles can explain some of the phenomena we are observing.
"WIMPs are a very specific example of dark matter, but there is a broader class of particles," Feng added. "We found that some of the models also predicted the right amount of dark matter for the universe, but with dark matter that was much more strongly or weakly interacting than WIMPs. We are wondering if almost-exclusive attention for WIMPs is really warranted."
Indeed, a lot of attention is focused on WIMP theory, what if dark matter researchers are being blinkered by one theory at the detriment of a more subtle explanation? One of the key points raised is that there is strong evidence supporting dark matter candidates with a mass of around 1 GeV. This finding comes from the DAMA (Dark Matter) project at the Gran Sasso National Laboratories, Italy, that investigates the signal from possible dark matter interactions in the galactic halo. WIMPS are far bigger, with a mass of 100 GeV. Could this signal be from a far lighter weakly interacting dark matter candidate?
There are also suggestions from other research that strongly interacting particles are annihilating all the time, generating high energy photons that can be observed pervading the entire Universe. Although this is theory, Feng is optimistic about energetic photon experiments.
However, re-analysing the WIMP dominance over dark matter creates some interesting scenarios for the Universe. By considering WIMP-less dark matter, some rather exotic explanations begin to form.
"There are theories that there is a shadow world behind ours. It is a mirror world that is like ours, but doesn’t interact with ours," Feng said. "With WIMP dark matter, that possibility is remote."
"WIMP-less dark matter requires new forces that we don’t really know much about. If you could have evidence of this type of dark matter, it might be a hint that this shadow world exists."
A shadow world may sound a little eccentric, but it is also built of viable theories just as the generally accepted WIMP theory is. This new study is certainly a reminder that dark matter is an unknown quantity, and researchers should be open to other particles and not just WIMPS…
Publication: Physical Review Letters
Source: Physorg.com
Filed under: Dark Matter
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December 14th, 2008 at 12:28 am
One picture of B H Obama who might not even be a citizen of USA gets tens if not hundreds of posts, but here about wimps this is the first???? I dont buy into wimps and I dont buy into any American who can not produce his records. ( birth, high school, college, post grad) Wimps hahha
December 14th, 2008 at 12:47 am
bill……I HATE you….please leave……..this planet.
December 14th, 2008 at 12:48 am
seriously
December 14th, 2008 at 1:04 am
Bill, I posted this article not 30 minutes ago… be proud you were the first to comment… but it would have been nice if you kept on topic. Any thoughts about dark matter and weakly interacting massive particles? Hmmm?
December 14th, 2008 at 1:28 am
Unless you believe in God, miracles, alchemy, and witchcraft like Newton did, gravity is a myth. Argon is twice as heavy as nitrogen, and nitrogen is heavier than oxygen but somehow we can magically breathe because the elements in the atmosphere defy gravity. Ozone (O3) is heavier than oxygen (O2) but it defies gravity. Water vapor and clouds are heavier than air but they defy gravity. Earth has not exceeded escape velocity or crashed into the sun so unless you believe the Newtonian God, in His infinite wisdom, gave the planets the exact perfect orbital velocity at the time of creation 4.5 billion years ago there is no such thing as gravity. How come Mercury doesn't crash into the sun? Aren't impact craters and Birkeland currents frictional force? How come stars orbiting Sagittarius A* exhibit Keplerian orbits instead of being sucked into the alleged black hole by the force of gravity? There is no such thing as fixed stars. Galaxies collide (Arp). And black holes, neutron strars, dark energy, and gravity are myths. Welcome to the 21st century.
December 14th, 2008 at 1:30 am
Typo: argon is heavier than oxygen, and nitrogen is lighter than oxygen but they are all found in equal amounts throught the atmosphere.
December 14th, 2008 at 3:45 am
mmm…. good article (not that I really understand it!).
A shame about the crackpot comments…
December 14th, 2008 at 4:00 am
So now we have three possibilities for dark matter: wimp-free, wimp and wimpier. Sadly there is no theoretical limit on crackpottery.
December 14th, 2008 at 4:23 am
Martin,
No there isn't any theoretical limit on crackpottery, and for good reason, there shouldn't be. Its these "crackpot" theories that have led us to many, if not all of the discoveries in astronomy, from the sun centered solar system, to gravity, to relativity.
Anyone with half a brain is smart enough to look back and understand that all proven theories have branched from crackpot theories and future discoveries will continue to do so. Look at the scientific revolution.
“There are two objectionable types of believers: those who believe the incredible and those who believe that 'belief' must be discarded and replaced by 'the scientific method”
I think this Max Born Quote sums up the last 300 years plus of scientific discoveries because of our crackpot theories. Its because of these scientists that we understand why we stick to this giant rock we call earth, why we can't walk on water and turn it to wine…god help us if we could do both at once. We could pass out on water too.
All in all, without these types of theories, we would never be where we are today. Without sounding like many philosophers, eventually we, as a race, have found so many ugly theories to be proven wrong, that one so beautiful develops and is proven right.
December 14th, 2008 at 6:04 am
I was thinking of the crackpottery of the early comments. To your Max Born quote I'll add Niels Bohr (version taken from among many on Wikiquote):
"We are all agreed that your theory is crazy. The question that divides us is whether it is crazy enough to have a chance of being correct."
December 14th, 2008 at 9:49 am
Oils, you obviously haven't a clue about Newton or Kepler's Laws. I sorry to have to say this but your willfully ignorant rant shows that the average twelve-year old understands the fundamentals of physics better than you do.
I still find it pretty astounding how some people will reject the work of tens of thousands of scientists over the last three hundred years — work that has been confirmed observationally to the nth degree countless number of times — and then claim to believe one or two cranks who usually aren't even scientists and who spout crackpot theories that aren't even good science fiction.
It's utterly bizarre, and at some point (as with Oils) you just have to throw up your hands and give up trying to teach these people anything. They're just not interested in learning in the first place.
December 14th, 2008 at 10:20 am
So Tacitus, if argon is heavier than oxygen how are we able to breathe?
December 14th, 2008 at 10:57 am
Argon is a noble gas, meaning it is pretty well inert. Oxygen bonds to itself, forming O2 which is heavier than argon. There is also the fact that weight and density are not the only factors which serve to "emulsify" our atmosphere. There is also convection and turbulence resulting ultimately from the energy added to the system (sunlight). The fact that you show ignorance of something so basic, and thus try to deny that which defies your understanding without ever giving it serious study, indicates to me that you are indeed a crackpot.
I could go on poking holes in your statements, but you bore me. Moving on to the next article.
December 14th, 2008 at 11:07 am
Welcome in the past OillsMastery. Your question has been answered over a hundred years ago.
Your argument is a strawman, an absurdly simplified version of physics, the theory of gravity doesn't predict anything like an layered atmosphere, thus saying "the atmosphere isn't layered!" doesn't prove anything.
What it boils down to: The atmosphere isn't the static thing that you picture. All the different atmospheric gases are mixed together into a swirling mass through the process of diffusion. This page on Wikipedia describes diffusion with the aid of diagrams – http://en.wikipedia.org/wiki/Diffusion
The Brownian motion of molecules prevents the atmosphere from forming layers.
Sometimes you have to look at the big picture OillsMastery, you can "disprove" all scientific theories if you ignore all the other factors that are involved in observed phenomena.
December 14th, 2008 at 11:28 am
OIM is a troll who believes that Gravity is a myth, subduction doesn't happen, all Oil is Abiogenic, Velikovsky was right, and the list goes on and on.
He's already had his misconceptions explained to him on at least one other forum that I regularly attend.
December 14th, 2008 at 11:29 am
Oils, three simple facts:
1) There is 22 times as much oxygen in the atmosphere than argon.
2) Argon is only 25% more dense than oxygen, so Argon doesn't settle out in a layer below oxygen because even the slightest current of air is enough to mix the gases. If you're in a completely sealed room, your movement and the very act of breathing in will ensure that you get enough oxygen to breath, even if you're lying with your nose to the floor.
3) In addition, the effect of Brownian motion (look it up) will help to mix the gases too.
Hint: do some reading. This really is very basic science — there is no mystery, no conspiracy of silence, just very basic high school physics and chemistry. Wikipedia is always a good place to start.
December 14th, 2008 at 12:19 pm
I think we will eventually find that the gravity effect of dark matter is produced by matter that is less exotic than is currently believed.
What about something as simple as there is an extended halo of gas, dust, lone stars and brown dwarfs around the galaxies that goes out, let's say 4 times as far as the easily visible galaxy limits.
We've already detected halos producing x-ray emissions but what if there is still an even greater halo than the x-ray producing region.
http://www.universetoday.com/2006/02/04/hot-halo-surrounds-distant-galaxy/
December 14th, 2008 at 1:05 pm
anyone know if the LARGE "HARD-ON" collider is back online?
it may shed some light on the debate. perhaps aside from hopefully finding the higgs-boson, could it also discover evidence of what makes up dark-matter?
all the sane people in the forum, please simply ignore the retards….maybe call them names or something.
December 14th, 2008 at 2:30 pm
http://xkcd.com/386/
Oh my god… Someone is WRONG on the INTERNET!
December 14th, 2008 at 3:11 pm
It would be funky if the spiritual world existed in Dark Matter and we were CS Lewis's "Shadowlands" as described in the Great Divorce. Not saying anything's right or wrong, just interesting.
December 14th, 2008 at 4:39 pm
Hmm. Sounds like an idea for my next book (if I ever finish my first one, that is!).
Mind if I steal it?
(just kidding).
December 14th, 2008 at 5:14 pm
Something does not add up with WIMP's and other Dark Matter theories. Well, I understand we cannot really directly observe or sense it, because it is not interacting enough with the electromagnetic field, but it still interacts with normal matter through gravitation. That's why we "know" it is there. Now if the Universe is really made mostly of DM, I'd expect that there would be plenty of it everywhere around us too. And that there would be much more of it around any massive object, because it would trap the DM gravitationally. Or oppositely that the DM objects would bind visible massive objects and that they would then orbit around them. However, AFAIK, we did not observe anything like that. And despite the fact that the DM is not observable, a close amassing of DM or a flyby of a huge DM object (or a cloud) around visible objects would be well measurable even with today's technology. If the DM makes for 60% (or 90%, or whatever) of the Universe mass, then I would expect a rather frequent flyby's of DM objects around or through the Earth and other planets in our Solar system, or in other solar systems in the Galaxy. Why doesn't the Earth have a dozen of DM moons? Or DM rings? And do not tell me it would not be detectable! It would.
Well, the only explanation is that the DM is internally bound with much stronger forces than the gravitation, and actually does not create any gravitationally bound objects, and does not amass in the way visible matter does, and rather creates a mesh (like a sponge) through which the visible objects move freely. If it is so, then the theory about the DM being formed by strongly interacting particles does not make sense to me.
Anyway I admit I am ignorant as for DM goes, and know about it as little as the experts studying it
December 14th, 2008 at 5:19 pm
To the people responding to the likes of 'Bill' and 'OilsMastery'…..can you please stop feeding the trolls?
Just listen to the sheer stupidity of these people, but being the optimist i am, i think the best explanation is that these are trolls…they are more than 14 kinds of wrong, and they know it….troll'ism at its best.
December 14th, 2008 at 8:55 pm
trux, whatever dark matter is, it's too diffuse on a local scale to affect normal matter enough for us to measure it's gravitational effect. If the Earth happened to travel through a large volume of diffuse gas, we would barely notice it, and it would not automatically collect together into rings or moons, so there is no reason why dark matter should, especially since it is even less dense and interactive.
I think the best you can hope for is that there is a very slightly greater concentration of dark matter in and around more massive normal objects like stars, but even then it would be like finding a very, very slightly more dense area of gas, not a ring or a moon of DM.
December 15th, 2008 at 12:29 am
"To the people responding to the likes of 'Bill' and 'OilsMastery'…..can you please stop feeding the trolls? "
I'm not responding for the trolls sake, but there may be readers here who are interested in why the atmosphere doesn't form layers and don't know the science involved. Ignoring dumb ideas may work in academia where the harshest thing is being ignored by your peers. We're on the internet though.
December 15th, 2008 at 7:36 am
I'm all in favour of far out theories and speculation and have always loved the idea of WIMPs, axions, gravitinos, super-symmetricdal partners to the usual family of bosons etc. However, proposing particles that are even MORE weakly interacting than the ones we haven't yet seen is pushing the envelope just a bit too far. Experimentalists just hate it when theoreticians come up with ideas that are on the far shores of possibility.
Still it's a wonderful read. More please.
December 15th, 2008 at 8:49 am
Anyone who still believes in the Newtonian God's divine gravity should get one of these for Christmas: http://www.teachersource.com/ElectricityAndMagnetism/ElectricityAndMagnetism/Anti-GravityGlobe.aspx
December 16th, 2008 at 1:56 am
Oh, shoot, I have the same name as the crazy dude…
Anyways, the post with the included link to xkcd, that was me. Nutty tangent about Obama, definitely not me.
Man, this sucks. I can't just go with my first name anymore… Thanks for ruining my day, Crazy-Ass Bill.
December 16th, 2008 at 10:31 am
I have been wondering about this.
If gravity spent much of the cycle out of our brane then we might expect otherwise normal matter to be capable of oscillation along the same plane.
Non coherent ions with this (fruitloop?) energy level would of course not interact* with each other.
I have still not worked out what a coherent (machine) object would be capable of; strange things, I am sure.
*very much; one would expect a Fred Hoyle style continuous creation thingee to be visible at some level; a very low level.
December 19th, 2008 at 8:24 am
Bill L. ,
The artist formally known as Bill L. ?
December 19th, 2008 at 8:59 am
Perhaps I am on someone's troll list. I am well fed, though, so I will throw out food for thought. One of the underpinnings of the dark matter conjecture is the pie-plate rotation of spiral galaxies. That is, by Newtonian mechanics we expect the closer-in stars to orbit the center of mass of the galaxy faster than those farther out. In fact the galaxies rotate as if they were a single object. Thus the conjecture arose that they are embedded in a larger structure of invisible gravitating mass. There are a number of alternative explanations, though, for instance: the conjecture of MOND (modified Newtonian gravity). Not to mention EM forces, whose responsible particles create forces (both attractive and repulsive) that are 10^34 times more powerful than neutral gravitating particles (attractive only). So we are far from the final chapter in the discussion of DM. Let the troll-calling begin.
December 19th, 2008 at 10:16 am
Looking further back (I had neglected to go to page one comments) I see I am not the troll reference, I thought someone had taken offense at a prior post of mine. That Oil guy has some mashup of uncorrelated thoughts. As for the other bill…BillO of Fox – lurking? Bill Illis – you're onto it…Occam's razor got rusty on this issue, there are known forces and alternate theories that are candidates for the DM effect, that should be seriously considered in lieu of invoking entirely new, conjectural, possibly imaginary entities.
March 4th, 2009 at 3:51 pm
Not shadow world, " shadow universe " It exists beyond the speed of light.
March 19th, 2009 at 5:37 am
A layman's question: Could dark matter be explained as the gravitational influence of matter existing in a different dimension or universe? That it is not actually matter that exists in our universe?