The Science of Sustainability

Dark Matter Tests Positive (Sort of)

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The first evidence for dark matter came from Fritz Zwicky’s observation of the Coma Galaxy Cluster. Image Credit: NASA, JPL-Caltech, SDSS, Leigh Jenkins, Ann Hornschemeier (Goddard Space Flight Center), et al.

Dark matter (think of matter as a fancy word for stuff) is one of the most exciting but also potentially frustrating phenomena in cosmology today. It plays no detectable role on Earth in deciding how far we can throw a baseball, or determining the characteristics of the complicated materials we use to build computers. In fact the only reason we know that it exists at all is by looking through telescopes at objects so distant that it would take hundreds of millions of years to get to them even traveling at the speed of light. And yet we believe there is almost six times as much dark matter in the universe as the regular matter that we can see and feel and touch. Recent results of the Cryogenic Dark Matter Search (CDMS) may have brought us a step closer to understanding this elusive material.

Dark matter’s discovery belongs to Fritz Zwicky. Known for a bullying personality and a fondness for doing one-armed pushups in the Caltech dining hall, Zwicky also measured the Coma Galaxy Cluster in 1933, and noticed that galaxies seemed to be moving far more quickly than gravitational theory would predict. Either the theory of gravity had to be wrong, or some other hidden form of matter–dark matter–must be playing a role here. (Careful! This is not to be confused with antimatter, which stars in Dan Brown’s Angels and Demons, or with dark energy, an even more bizarre cosmological idea.)

Subsequent measurements have corroborated Zwicky’s conclusions, and today we can say with a fair degree of confidence that dark matter must exist. Still, we don’t have any idea why this is so or what dark matter might actually be.

Enter CDMS, a whopper of an experiment buried deep within the Soudan mine of northern Minnesota and consisting of a collaboration of no fewer than 18 experimental research groups scattered across the world. Some of the most promising theories predict that dark matter consists of a deluge of particles constantly washing through the distant galaxies we see, but also through our own Milky Way Galaxy and in particular through the Earth. Such particles, coined sometime in the 1980s as Weakly Interacting Massive Particles (or WIMPs), should be detectable on extraordinarily rare occasions if you can put your detector in a pristine enough location.

On December 17th, CDMS disclosed the final results of their most recent experiment, and they have reported two events that seem likely to have been caused by WIMPS. Statistically, they find that these events have only a 23 percent chance of being a coincidence. If they are real events, this will certainly be a landmark moment in the history of physics.

However, the search for dark matter has been marred by controversy before. Another large experiment called DAMA in Italy has insisted for years that they have irrefutable evidence for dark matter particles at their own detector. Unfortunately, many other experiments are in direct conflict with DAMAs claims, and consequently nobody seems to take that group seriously. Consequently, CDMS researchers are being careful not to overstate their case.

In the end the hunt goes on, perhaps rightly so. After all, there is a 23 percent chance of dark matter being something else entirely, and if the odds of winning the lottery were 23 percent I would be running off to buy a ticket right now.

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Category: Astronomy, Physics

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Christopher Smallwood

About the Author ()

Christopher Smallwood is a Graduate Student in Physics at UC Berkeley. He is interested in the nexus between the basic research community and society at large. Originally from the Bavarian-themed tourist town of Leavenworth, WA (yes, real people actually do live there!), he graduated with an A.B. in Physics from Harvard College in 2005, taught fifth grade at Leo Elementary School in South Texas, and has been pursuing his Ph.D. in the Bay Area since the fall of 2007. Currently, he studies experimental condensed matter in the Lanzara Research Group at Lawrence Berkeley National Laboratory. His past research interests have included Bose-Einstein condensation, rubidium-based atomic clocks, hydrogen masers, lenses and mirrors, mayflies, mousetrap cars, toothpick bridges, fawn lilies, the slinky, Legos, vinegar and baking soda volcanoes, wolves, choo-choo trains, and the word "moon."
  • Oa Ah

    This is really interesting. I wonder what it really is and if there is some on earth. Scientists need to take all research groups seriously though, because I there are two then they can correct each others mistakes. If they work together they can speed up the research and find out what it is faster.

  • barbarina zwicky

    Fritz Zwicky is the Father of Dark Matter and coined the term itself. It should not require my directive to ensure that a professional site restrain from parroting the embellished and exaggerated ramblings from the oral histories that have long been exhausted. The "anecdotes" find their origin in the less than original imaginations of mediocre colleagues, consumed by professional jealousy, who found an outlet for their shortcomings in mean-spirited character assassination. My father never bullied anyone, but the boldness of his vision, his genius and his numerous discoveries, grated on the scientific community.

  • Jo Yu

    I think that this is a very interesting subject, because its not something common. It is a topic that raises many questions and many have been unanswered. Since it is only a 23% chance that it is NOT dark matter and something else entirely, I think that it IS dark matter since the chances are pretty low. It may be 23% and it IS a possibility that it will not be dark matter, but who knows for sure, we may or may not find out int he future.

  • http://science.kqed.org/quest/2009/12/28/dark-matter-tests-positive-sort-of%E2%80%A6/ HO,IS

    I find it very peculiar that there is only a 23% chance of dark matter being something else entirely.Also i am curious is there is almost six times as much dark matter in the universe, is there not any on Earth?I also hope that the recent results of the Cryogenic Dark Matter Search (CDMS) provide us information on the dark matter.WOW I <3 SCIENCE

  • Be Wu

    Just the sound of "dark matter" gives me the chills. But anyways, it's a very interesting article. I never thought of having dark matter in the universe until now. And that suprises me how there is about 6 times as much dark matter than regular matter. I want to know what the dark matter might actually be though. COOL!!!!

  • Ee Re

    I think it's interesting that dark matter may exist. They might know someday what dark matter really is. However I really don't know if dark matter exists or if the theory of gravity is wrong. But I do know that they'll find out someday.

  • Je Ye

    So wait, let me get this straight. Some galaxies are moving more quickly than a theory predicted because something is doing something to the galaxy to make it go faster. Honesty, I think this is all just made up crud. The reason is that there is no concrete proof that dark matter exists. At most, these people have proven the posibility that it does, otherwise the rest of the theory is just speculation. The case is just too unstable to hold water, and it cant prove anything with hard evidence, like i said before, this is ALL speculation. Hey wasn't there a time where the brightest minds thought the world was flat like a coin or just around a century ago, when we thought the smallest matter in the universe was an atom, until we split it open and this mess of stuff came out? Point being, even geniuses make mistakes and i think this is one.

  • Gi Ts

    Dark matter is very interesting to me because no one knows what the matter is and why its in space. I think dark matter has to do something with how earth was formed and the beginning of life. People should send more research groups into space so they could figure out what it is and see if it could damage the earth or anything important to the human race. If dark matter was a object, hopefully inventors could make something useful with it.

  • KatFrat

    wow. that is really confusing. so there's supposed to be 6 times as much dark matter as regular matter, and it is found in caves? (and space?) and it has no effect on humans and the only reason we know about it was because a galaxy seemed to be moving to fast while looking through a telescope?? i'll say it again: WOW.

  • Rash

    The subject of dark matter has come to be a great interest to after this article because it says that it is both 6 times more abundant than regular matter, yet it was nearly impossible to see and discover. The fact that there is a very good chance that this intriguing material can be found on our very own Earth is simply amazing. Since we don't really know a lot about this substance, and if we can learn how to tap into its energy if there is any, there is a chance that we could improve daily life. I think that the scientists studying cosmology should really look into this more and run some tests.

  • http://orbitalfriendshipcannon.tumblr.com Tr Pe

    I was amused on how the writer of this article tried to make this more kid friendly, like we couldn't understand more scientific terms. I would have thought of this better if it had been more serious. On the other note, the subject of dark matter has always intrigued me after I played a game including it (it exploded). It was surprising for me to see a topic on it again, after so long. The portion about the mine surprised me; something that makes up the universe could be found here on Earth. I had to do some research on it because this article, which barely gave any information whatsoever what dark matter actually is, left me dubious, but I decided to follow-through. It mesmerized me how people tried to prove something "that isn't matter" exists. Even writing that made me feel stupid. If there is evidence, question that evidence, and you'll learn something new; that's how life works. If they can somehow study this and learn something which was totally unexpected (for example, the ability to communicate with other-worldly beings, like espers, time-travelers, aliens, and Santa Claus) then they should continue to study this "abundant but difficult to find" matter.

  • Ka El

    I think it is interesting that dark matter may acctualy exist. And not only exist but be 6 times more dark matter than actual mater we can touch and feel. Its also funny how zwicky created the theory about dark matter. But at the same time it was great thinking on his part to question another persons theory. I always think that most great theorys are made by pushing the envelope and questioning other peoples thoughts

  • LeCh

    I agree with 'TrPe' on this one. I had a hard time reading around all the parenthesis, and it made it all more confusing. So much so to the point that I had to read it more than two times to understand it. And I don't know about you, but there were more confusing and troubling words in there than 'matter', however they somehow forgot to include a synonym for it too. Also, when they said that it wasn't to be confused with antimatter, or dark energy, they had completely lost me. If anything, it made it worse, mentioning that. Now, onto the subject of article itself, I agree that the hunt should, in fact, go on. Again, I must say that 'TrPe' is in the right here when they said that this article gave little information. At least, that is what I felt. I, too, felt compelled to do my own research on it, and not because I'm a nerd and like to study and learn about things that I'm not required to for homework. Anyway, moving on. I am amazed at dark matter, for we don't know if it really exists, yet we find the possibility that it might. It also proceeds to escape our grasp any moment it can. I am also astounded that there is about 6 times as mush dark as regular matter. Although, if you really look at it, we have absolutely no idea how big the universe really is, how much space, how much matter, what have you, yet we decide to focus on something as insignificant as to whether something exists or not.

  • Wi Zh

    I think that this subject is very interesting. I never knew that there were 6x as much dark matter in the universe than that on Earth. But to be honest, I don't really think this is real, I mean, just by the title "Dark Matter Tests Positive (Sort of)" doesn't sound so reassuring. In a way, I agree with Je Ye.

  • He Gi

    For a Christopher "Smallwood" to post such an "find," I find it hard to sort of believe, but yet extremely amusing and easy to find mistakes and puns throughout this article. Dark matter, is an interesting concept, IF ever proved real. I think that these investigations should continue, yet if dark matter is just a hoax, you've learned one thing, and keep finding more things to discover. If there is 6x dark matter than regular matter, this COULD explain the far reaches of space, yet there is still room for error. I agree with Tr Pe that the way they worded this article was too kid-friendly. I also agree with Je Ye that this could all be a pile of crud, to word it in a nice way. And also, I am the first person to start my reply off with the word, 'for.'

  • LiGa

    I had never even heard of dark matter until now. This must be a difficult topic for scientists to study. So dark matter exists but doesn't affect us at all? I find that very interesting and remarkable.

  • Rh Go

    Dark matter is hard to imagine, and I'm not going to lie. What I find interesting is not the thing itself, but the fact that people are so willing to invest time and money in what is so far out of our lives. I always thought of the quote "out of sight, out of mind", as a true statement, but now I see that I am wrong. It's amazing how there are not few, but eighteen experimental research groups. There are people living day by day studying something that to me, seems so out of our reach. I think what it all comes down to is mystery, people wanting what they can't have, and trying to understand something that isn't connected to our own earthly problems. But on the other hand, it is in studying the unknown and unreachable, that people are able to conceive of possibilities.

  • Ta me

    I don't really understand dark matter. It is hard to imagine something that is not proven to be real or known what it looks like. It seems irrational to me that scientists will invest that much money into something that may or may not exist. It is also really mind twisting that we have no idea where this matter could possibly be located.

  • ChLi

    I don't understand why scientists are spending so much time on something that is only 87% true. What if it isn't? What will happen to all the time and effort going into this? Either way, it's not very likely that the money's just thrown away, but still. Oh well, got to take some chances right?
    And by the way, 'Dark Matter" is a creepy name. It like, makes me think of evil stuffs. O_O
    Nice article! c:

  • http://www.kapillavastu.com nilesh

    There 7 Neutrinos in every photon radiated. On being detected by any receiver, the displacement due to angular momentum is absorbed and the balance is measured as mass/ Therefore 7/(2^.333) = 5.56 relative mass that is undetectable. See http://www.kapillavastu.com/in… where the axiomatic derivations are presented in Sankhya the acme of unification.