LEADER OF THE PARTICLE PACK: CMS, one of two general-purpose particle physics experiments at the Large Hadron Collider in Europe, could soon tell astronomers what dark matter is made of.
Image: © CERN
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Gravity's Engines
We’ve long understood black holes to be the points at which the universe as we know it comes to an end. Often billions of times more massive than the Sun, they...
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BALTIMORE—Dark matter pervades the universe, giving shape to the cosmos on the grandest scales. So perhaps it is fitting that physicists are turning to a large-scale physics experiment to uncover what dark matter is made of.
Dark matter helps mold galaxy formation and accounts for five times the mass of all the ordinary, visible matter in the universe, but it has eluded direct detection for decades. Astronomers can see its gravitational effects—galaxies and galaxy clusters behave as if they have far more mass than ordinary matter alone can provide—but the particle nature of the stuff remains a mystery.
At a recent dark matter symposium at the Space Telescope Science Institute here, hopes for a solution via the Large Hadron Collider loomed large. The LHC, essentially a 27-kilometer particle racetrack buried 100 meters belowground near Geneva, started up in 2009 and quickly became the most powerful particle collider in the world. At a series of controlled impact points, protons boosted to near the speed of light collide head-on, and physicists sift through the outflying debris to look for hints of new physics.
Astronomers and cosmologists have their fingers crossed that a positive ID on a dark matter particle will be among the new phenomena that should soon come streaming out of the LHC. After all, astronomical probes that have sought out the signature of dark matter particles have come up empty, as have experiments on the ground designed to detect the stuff.
"I'm feeling a little pessimistic," astronomer Sandra Faber of the University of California, Santa Cruz, said during a panel discussion at the symposium. "As every speaker in the last two days gave their talk, I thought to myself, 'How can I make a case here that astronomy is going to answer the nature of dark matter?' I think it's pretty thin. I think we have to turn to the physicists to actually discover this particle—or particles—and tell us what it is."
One ongoing possibility is that one of many specialized dark matter detectors—such as Xenon100 in Italy or CoGeNT in Minnesota—could catch a whiff of the stuff as Earth passes through an ambient haze of dark matter. But many researchers hold out more hope for the LHC, which could produce dark matter in its particle collisions.
That would light the way toward other complementary detections. Many researchers, for instance, have used the Fermi Gamma-Ray Space Telescope to look for the signature of dark matter particles crashing into one another, mutually annihilating, and giving off gamma rays. Dan Hooper of Fermilab and Lisa Goodenough of New York University published a study in Physics Letters B in March showing that Fermi observations of the center of the Milky Way Galaxy seem to show a gamma-ray excess indicative of dark matter annihilations there.
But the data are somewhat ambiguous, U.C. Santa Cruz physicist and Fermi team member Robert Johnson said in a talk at the dark matter symposium. "You don't see any residuals at the galactic center that would suggest something extra going on there," he said. "I think it's an open question whether there is a dark matter source at the galactic center. It's very difficult to disentangle it from the other stuff going on there."
In an interview Johnson noted that the LHC should be able to clarify things considerably. "We're kind of looking blind at the data now," he said. If the LHC could pin down the attributes of a promising dark matter particle, the Fermi data would come into much tighter focus. "The LHC has a much greater reach in the parameter space for looking for something like supersymmetric dark matter," Johnson said. Supersymmetry is a popular hypothetical model for particle physics that posits that each elementary particle—quarks, electrons and so on—has a hidden counterpart particle just waiting to be discovered. One such supersymmetric partner might provide an ideal candidate for the dark matter particle.
Looking for supersymmetry is one of the LHC's primary tasks, along with discovering the long-sought Higgs boson, which is theorized to lend other elementary particles mass. And depending on the traits of the supposed supersymmetric particles, the LHC may be close to finding them. "By this summer or this winter we may have something to say if there are supersymmetric particles living out there," physicist Albert de Roeck of CERN, the European particle physics lab that operates the LHC, said at the symposium.
Even if it takes a bit longer than that—as it may if supersymmetry resides in a regime less accessible to the LHC's detectors—astronomers are willing to wait. "Give us about three years for the LHC to reach maximum luminosity," astrophysicist Joe Silk of the University of Oxford said in the panel discussion. "If they find evidence of supersymmetry, I think this would give a fantastic boost to the field."
Astronomers are counting on the LHC to break new ground in the dark matter search, but in an interview de Roeck said their expectations were not putting significant added pressure on CERN. "Supersymmetry is good—it will satisfy many customers," he said. But compared with the race to find the Higgs and the political pressure to deliver returns on such an ambitious and expensive experiment, the added pressure to find dark matter is "peanuts," de Roeck said.
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24 Comments
Add CommentThe dark matter camp should be getting desperate after so many decades and so many conclusions based on the presumptive dark matter.
Reply | Report Abuse | Link to thisAs for the Higgs boson, its existence presumes that all forces are properties of matter. Unlike the other forces, which do emanate from matter and are mediated by the exchange of particles, the effects of gravitation appear to require the presence of mass but emanate from space.
Perhaps mass is not properly a material force but a separate, external energy field associated with the initial condensation of matter in the early universe? Perhaps it is this external energy that produces particle spin and charge and the resulting material forces?
Nature has been giving us a consistent answer to all particle dark matter searches for the past 30 years.
Reply | Report Abuse | Link to thisThe answer is: The dark matter is not composed of any form of subatomic particle.
One form of dark matter for which there is excellent observational evidence already gathered and published is "primordial" stellar-mass black holes. The MACHO microlensing experiment and the ARCADE-2 radio background experiment both yielded concrete evidence that is consistent with a huge population of "primordial" stellar-mass black holes.
Particle physicists can keep wasting their time and millions of our dollars on their fool's errand to find "WIMPs". They are clearly wrong, but apparently they have too much invested in the game to stop now. Besides, then they would then have to admit they were completely wrong, and we all know that theoretical particle physicists appear to be congenitally incapable of admitting error.
Robert L. Oldershaw
http://www3.amherst.edu/~rloldershaw
Discrete Scale Relativity; Fractal Cosmology
Wasn't there an article in this publication just a few days ago maintaining there was growing doubt in the physics community about the whole idea of dark matter? It seems like string theory all over again.
Reply | Report Abuse | Link to this@Robert Schmidt, I would not immediately shut down all particle dark matter searches. But I would radically shift the emphasis and direction of dark matter research. And I would stop the torrent of hype promoting string/brane theories, unicorn particles, and the cornucopia of untestable pseudo-science that has been foisted upon us.
Reply | Report Abuse | Link to thisA scientist let's nature show him/her the answers. The scientist does not tell nature how it should be.
But the latter is what theoretical particle physicists have been doing for decades. They INSIST that the dark matter has to be some particle. This is not a scientific attitude.
The evidence for MACHOs and "primordial" stellar-mass dark matter is superior to the lack of evidence for "WIMPs". So why is our research effort and confidence in the candidates so bizarrely and unscientifically reversed?
Robert L. Oldershaw
http://www3.amherst.edu/~rloldershaw
Discrete Scale Relativity; Fractal Cosmology
Dark matter and dark energy are NOT facts, they are theories proposed to explain what we observe, or think we observe. Short of a Wayback machine and a dark matter/energy detector, we are a long way from proof of either.
Reply | Report Abuse | Link to thisI think you are right Outsidethebox. Additionally, as I recall SA had a very interesting article sometime last Spring that dark matter might not exist at all. As I recall the article suggested that the observable universe is a low density bubble in a higher density space, and the gravitational attraction of the surrounding higher density area outside our section of the universe was giving the illusion of an accelerating expansion of space. (My apology to SA if I am accidentally misrepresenting the article!)
Reply | Report Abuse | Link to thisWe have not defined what space-time is.With a multitude of virtual particle popping in an out of existence the potential for a huge amount of hidden mass is there.So why can't it's self be Dark-mass-energy.
Reply | Report Abuse | Link to thisDark matter and dark energy are the same two forces that mysteriously created this universe. What force collapsed the single singularity and what force expelled it into the expanding universe we observe today. This problem from the very beginning was never addressed and it has come full circle proving a weak foundation from the start. Stating the universe started before time and space therefore pre-big bang needs no explanation is a foolish game and has cost us a lot of time and money. Because of this weak concept of a beginning we now search for something we believe to be tangible when it is merely a concept, a different way to view what is actually happening that needs to be addressed. We have gone through these futile steps before trying for years to explain the motion of the planets with the earth in the center of the universe. The science world needs to rethink what the constant speed of light really means, its holy grail, its box that it cannot escape from.
Reply | Report Abuse | Link to thisI suggest a hypothesis that addresses both the mystery of dark matter, and the mystery of the balance between 'normal matter' and antimatter in my recently published book "The Short Range Antigravitational Force and the Hierarchically Stratified Space-time Geometry in 12 Dimensions". In my book, I suggest that space-time is hierarchically stratified into 3 layers (strata) consisting of 4 space-time dimensions (3 space, 1 time). In addition, in each of these strata there is a stratum dependent variation in parameters (c,G,h etc.), and nature and range of fundamental forces operating within (see page 44 of my book for a complete listing).
Reply | Report Abuse | Link to thisIt is my hypothesis that baryonic matter oscillates within the entire 12 dimensional structure consisting of 3 strata, and that dark matter (under other than high energy circumstances) normally only oscillates through the bottom 2 strata consisting of 8 dimensions. This explains why dark matter does not interact with baryonic matter via the electromagnetic force, because this force only operates in the uppermost stratum of space-time geometry. During nucleosynthesis in stars interstratum, gravitational interaction between baryonic matter and dark matter causes dark matter to oscillate into the baryonic matter stratum (instead of continuing to oscillate within the lower strata of 8 dimensions it begins to oscillate within the entire 3 strata, 12 dimensional structure) in the form of antimatter (positrons). These positrons then annihilate with electrons in the stellar plasma producing gamma rays. In other words the so-called missing antimatter has never been missing (it is just dark matter that is normally restricted from interaction with baryonic matter due to stratum dependent variation in space-time structure, fundamental forces and operating parameters (c,G,h etc.)
"Dark Matter" consists of consciousness. It is a cognitive function inherent in all things. The human
Reply | Report Abuse | Link to thisspecies is a contributing element (observer effect). In the beginning 'potential' 'borrowed' substance from the 'future' to generate a force effect. This also expresses as 'expectation'. All matter holds the same place. All energy arises from one interval. The transformation generates from expectation.
Dark Matter is People!
Reply | Report Abuse | Link to thisThere's been a lot of chatter about: all the wasted time/money looking for dark matter/energy. The idea is all the scientific community had to do is to ask me! I know ..., for example, it's not a WIMP but a MACHO! Primordial or micro-black holes have never been observed, despite many searches for their end of life expected gamma ray bursts. Another one says ... it's all consciousness! Maybe it's all about unseen unicorns or perhaps gremlins?
Reply | Report Abuse | Link to thisDark matter & energy are dark. Science proceeds by firstly finding out what is happening before the hows and whys are answered. We know that gravity exists and basically what it does. We still don't know how and why it does what it does. One could even call normal Newtonian gravity "dark" gravity since we have yet to discover the so-called "graviton." However we use it guide our satellites, spacecraft etc. These newer "dark" discoveries are in the same "dark" boat.
The particle experiments as well as the astrophysical ones are important. It isn't wasted time/money! They may not find what they are looking for but we will learn things. How great is that! The burden of proof sits on everyone page including those of you who already know everything! Let's get real!
You are over complicating things everything is a smaller part of a lager whole. This can be seen in electrons when they spin and orbit in the same direction creating a stronger magnetic force.
Reply | Report Abuse | Link to thisI do believe there are more dimensions than 4. The expansion force of the universe has its own 3 dimensions and its own 4th dimension of time. Matter has its own 4th dimension as it occupies three dimensional expanding time. How matter expands with or does not expand with expanding time and dimension is what makes it relative.
Black holes create infinite density because 3 dimensional expanding time stops at its event horizon making a black hole a gateway to 3 dimensional collapsing time.
Matter is the interaction between 3 dimensional expanding time and 3 dimensional collapsing time in one or more moments of time. Mass and energy are relative.
Matter in motion would occupy each moment in time infinitely if it were not for the force of black holes. Anti matter is, the same matter existing in different moments of time. It is a fluctuation of time and energy that produces matter and its counter part anti matter in the same moment of time.
The building blocks to the problem are simple all that are needed to create this universe is expanding and collapsing forces which produces three specific patterns spheres, connected spheres, and corkscrew events. If extra dimensions are introduced without this in mind it will not create a manifold that produces anyone of these specific patterns which means it is most likely wrong.
It is not extra dimensions that are needed to create the mass, energy, matter paradox it is density. There are different generations of matter because there are different generations of space which create different generations of time. Black holes with infinite density prove this.
In the equation of general relativity it is the density that needs to change to match the different generations of matter not dimensions. It is the tensor strength that needs to progress with the progression of matter.
The speed of light is not the fastest that can be traveled it is the fastest that can be measured which defines what a moment is. Wavelengths prove moments pass by in waves one after another. Gravitational red shift wavelength dilation proves gravity is produced by the absorption of time by matter.
dear No Toe,
Reply | Report Abuse | Link to thisInfinite densities do not exist in our 4-d causal deterministic universe.
The moment you say that matter is "expanding" you inroduce the time dimension, even an electron "moving" needs the time factor to do so, if not you can not compare a former location with a new one, time is the awareness of difference between the minimum of two states.
How do you come to the saying that matter occupies infinetely each moment, if it were not the force of a black hole, this seems to me rather nonsense, it is not the force of black holes that are responsible for the fact that each moment is unique and therefore endless, but the essence of reality, and furthermore I don't believe in the singulairities in black holes nor in the singulairity in the Big Bang (which is also a "what if" of scientists)
You are mixing anti matter and dark matter, the last is a so called solution for the differences in observed velocities of stars in galaxies, perssonnally my expectations are directed to MOND from Mordechai Milgrom.
For the speed of light I can agree with you, going faster then the speed of light gives you the possibillity to "LOOK" back on the past, not to change it. (you are going faster that the photons emitted for example on yesterday, so you can 'revive" yesterday.
keep on thinking
Wilhelmus.
The existence of dark matter is inferred because the visible matter in galaxies does not explain the apparent total (dark and visible matter) effect of gravity on the galaxy. But locally, our solar systems (visible matter) mass distribution and gravitational effects balance without invoking dark matter, though (theoretically) we are awash in dark matter. Why does dark matter's gravitational effect show up on the galactic scale, bit not on the solar scale?
Reply | Report Abuse | Link to thisDUMB = Dark Unknown Matter B... ( I'm too dumb to come up with the B-word ).
Reply | Report Abuse | Link to thisIt seems that those who are confused by the observed rotational characteristics of vast, distributed galaxies containing hundreds of billions of stars, since they are not the same as the several planets orbiting the Sun, figure that the dark matter that would clear things up for them can only exist in the Milky Way between 100,000 light years to 300,000 light years from the galactic center in order to balance its rotation. However, since no one has explained how to keep the dark matter out of the area up to 100,000 light years from the galactic center, particle physicists know that it must exist throughout the galaxy.
Reply | Report Abuse | Link to thisSo particle physicists look for dark matter here on Earth, but if they do find it, that will not prove that dark matter can explain the observed galactic rotational characteristics, which requires that it not be found within 100,000 light years of the galactic center...
It's only as complicated as you want to make it - just don't try to put it all together!
Scientific American should consider an article to address some of these questions and points concerning gravity and dark matter. To this layman it is beginning to smell of phlogiston. But maybe some patient, objective explanations could counter this perception.
Reply | Report Abuse | Link to thisI agree that it's about time for a 'minority report' from accredited, professional physicists who can and have demonstrated that no dark matter or modification to gravitational effects is necessary to explain the observed rotational characteristics of galaxies. I can even provide a list of practicing physicists who have written research reports, some of which have even been published in established scientific journals, indicating that galactic dark matter is not required, at least in some cases. Since I'm also a lay person that list does not include myself.
Reply | Report Abuse | Link to thisWhile the majority of the physics industry continues to spend many millions of dollars annually to study what this dark matter could possibly be or how fundamental gravitational theory might be changed, as it has done for well over 30 years, it is not too soon to reconsider the original conclusion that some mysterious factor is involved in the dynamics of very large scale masses.
Please feel free to contact me - I would be more than happy to assist in any way I can.
A recent article talked about looking toward the galactic core and seeing a few(10) Jupiter class planets transiting stars at 20k light years away..they extrapolated that there could be as many of them as the stars...I think that there are millions more of them than the stars....just a thought.....
Reply | Report Abuse | Link to thisBetter yet, DUMP...Dark Unknown Matter Particle.
Reply | Report Abuse | Link to thisIt' interesting that you would respond to my posting with the statement: "You are over complicating things everything is a smaller part of a larger hole." In fact, my ideas are influenced by an application of General Systems Theory to cosmology (you might find works by Ludwig von Bertalanffy and Arthur Koestler's : "Ghost in the Machine" instructive). Everything in nature can be seen as a complex hierarchy of self-organizing systems (wholes) which are themselves composed of systems that are their parts (parts that are also wholes in themselves). Furthermore, the whole is always greater than the sum of its parts, and there are a number of patterns that can be observed in all systems regardless of their type or place within the hierarchy of nature. Everything in nature is interdependent and it is reasonable to infer that general patterns that are found throughout the hierarchy of systems apply to the biggest system of all-the universe. Also every conceivable system has both a beginning and end, and when a system ceases to be, its component parts at some level of its hierarchical structure become parts in other systems (for example when the system that is me or you eventually dies the chemical components that our body are comprised of will be used again perhaps to produce the structure of a newly forming plant). Another pattern found by Gneral Systems Theory is nature's ubiquitous use of homologous structures to produce even more complex systems (a good example is the human brain which has retained the reptilian brain in its now more complex structure). It is not unreasonable to assume that dark energy, dark matter and baryonic matter fit together in a complex homologous pattern that has arisen through a cyclic evolution due to inherent thermodynamic pressures (which is what I contend in my previously mentioned book). In any case, no theory of cosmology or quantum mechanics can be correct unless it is consistent with General Systems Theory. Good luck in search for understanding. If it is any comfort, the reason there is so much debate about issues in cosmology and quantum mechanics is because very little is really understood right now.
Reply | Report Abuse | Link to thisPerhaps stars only form in about 1 in 25 gas nebulas.
Reply | Report Abuse | Link to thisDARK MATTER
Reply | Report Abuse | Link to this-- James Ph. Kotsybar
The universe is mostly abnormal,
if we accept that physicists aren’t wrong
and Newton’s gravity’s uniformal,
otherwise galaxies couldn’t last long.
They’d spin themselves apart, unless, unseen,
missing mass resolves the disparity.
Dark Matter is needed to intervene.
Though not found, it can’t be a rarity.
“Shining stars are like icebergs,” they patter,
“if the mathematics are to be served.
There’s as much as five times normal matter
needed to resolve dynamics observed.”
Though they’ll claim science is observation,
that can tweak, if it fits the equation.