Dark matter is for WIMPs

By Phil Plait | February 27, 2008 12:29 pm

What the heck is dark matter?

We know it’s real: many, many independent observations indicate that the majority of matter in the Universe does not give off light that we can detect, but we can detect the effects of dark matter very clearly.

We also know it’s not made of normal matter, like anything made up of electrons, neutrons, or protons. The effects we see would be very different if it were, so it must be made up of some kind of exotic matter we don’t have experience with, yet.

A leading contender for this stuff are WIMPs, or Weakly Interacting Massive Particles. It’s a bit of a generic term for a class of subatomic particles that don’t interact well with normal matter. They can pass right through you — actually zillions of them can — without having any effect on you whatsoever.

That’s not to say that WIMPs don’t interact at all. It’s just that they affect us weakly. According to theory, every now and again a single WIMP will ping off an atomic nucleus of normal matter, making it resonate like a hammer hitting a bell. It’s possible to detect that effect, and from that deduce the mass of the particles. That in turn will tell physicists a lot about the particle itself.

So lots of folks are looking for just that ringing. Caltech has an experiment running called Cryogenic Dark Matter Search, or CDMS. Deep underneath northwest Minnesota, 2400 feet (730 meters) down, is a laboratory that contains cryogenically cooled detectors, kept to within a hair’s-breadth of absolute zero. Billions of WIMPs pass through the detector every second, but it’s likely that only one or two per year will actually smack into a nucleus and shake it up.

New results just announced indicate that the mass of any purported WIMPs must be less than 100 times the mass of the proton. How do they know? Because they have been looking long enough that if any WIMP more massive than 100 times a proton existed, they’d have detected it by now. They haven’t, so the mass must be less than that.

It sounds like a negative result, but that can still be pretty useful. In this case, it’s consistent with theory, which poses the most likely WIMP mass at about 40 times the mass of a proton. As the experiments continue to run, and the detectors get better, they’ll be able to nail things down to that mass range as well.

If and when they find their WIMP interactions, it’ll be a HUGE day for astronomy. It’s a little frustrating to know that dark matter is out there, to see it affecting whole galaxies and clusters of galaxies, but not know what the heck it is!

I bet that inside of a decade (probably sooner) we’ll have either detected WIMPs, or ruled them out as a contender for dark matter. I’m not sure which I’d prefer. It would be incredible to have a new particle in our repertoire, especially since its existence would have been predicted by astronomy and not from the standard model of subatomic particles. It would also be fascinating to find out that there is something out there even weirder than WIMPs, which are plenty weird enough.

And while you’re thinking on that, chew on this: it’s only been in the past few decades that the very biggest thing of all — the Universe — has been tied to the smallest things of all — subatomic particles. The very small and the very big are connected in a fundamental way, and it’s only been through science that we’ve perceived that connection.

Some people like to say that science can’t answer questions like why are we here, and what the Universe is all about. I think those people are wrong. By peeking behind the Universe’s curtain, we’re learning more about it every day. Big questions deserve big answers, and science is up to the task.

CATEGORIZED UNDER: Astronomy, Cool stuff, Science

Comments (56)

  1. Dave C

    Awesome blog! I am an amateur astronomer and a physics teacher myself. Dark matter fascinates me.

    So that leads me to a question. What makes these scientists so sure that they should have detected any particles yet? Even if the mass of these particles is larger than 100x mass of a proton, couldn’t they interact so weakly with matter that nothing would be detected? What exactly makes them so certain?

  2. As an undergrad working on CDMS (albeit in a really unimportant role), I feel I have to point out that CDMS is a huge collaboration, with Stanford and UC Berkeley also playing big roles (I think MIT is involved too, Wikipedia doesn’t say). But I thought my adviser (Prof Blas Cabrera) was the PI, and I know that the detectors were built off of technology he pioneered (you might remember him from the so-called “Valentine’s Day Monopole”, when he though a SQUID picked up a magnetic monopole, but it didn’t pan out). At the very least, the early detectors were housed here (in fact, the room where they were is where I currently work).

    Also, it’s cool to know I can talk about this, since we were gagged until after the results were announced.

  3. SLC

    But 75% of all the gravitating force in the universe is attributional to dark energy. Are there any ideas as to what dark energy is?

  4. Remek

    Worthwhile (even if the result is zero), but wish the overall hardware were cheaper –

    – imagine being able to fund several, less-expensive, science-equivalent experiments (in every discipline) each year, rather than the current single expensive experiment every 3-5 years.

  5. ioresult

    The recent universe today article (LINK) seems to imply that dark matter is composed of black holes and neutrinos.
    What would be the mass ratio in the universe between WIMPS, black holes and neutrinos?

  6. Keith

    Hey Phil,

    One thing I’ve been wondering lately that maybe you can help clear up is:

    How do we know that the indirect effects we are seeing are not due to the collective effect of a bunch of fairly small (e.g. dust-sized) particles that we just can’t see with our telescopes, instead of this fundamentally different type of matter?

    Thanks too for taking the time to write thoughtful blog articles. I love it :)

    Take care,
    Keith

  7. Philip

    Phil,
    I thought science will answer all the how questions!?
    All the why questions are so, for a lack of a better word, spiritual or even irrelevant.

  8. KaiYeves

    Hey, I don’t really get dark matter. Does that make me a…
    Oh, wait, it’s an acronym!

  9. Doc

    WIMPs, MACHOs, SQUIDs – I love this stuff, but it makes my brain hurt. I miss the old days though, looking at the spirals made by electron-positron pairs in bubble chamber photos.

  10. I’m still holding out for massy neutrinos.

    That said, I don’t think discovering more about how the universe works brings us any closer to answering questions like “Why are we here?” That’s not the sort of thing that’s amenable to an empirical test. Science can tell us how we got here, not why things happened that way.

  11. SQUIDs???

    Shame on you. We don’t talk about that kind of stuff here.

  12. alex

    do you remember “ether”?? in the physics of the XIX siecle was the medium in which the light was transmitted. then came A.Einstein, and that idea became obsolete. i’m a layman, but sometimes i wonder if the “dark matter” is the new ether…

  13. phunk

    Keith – They know it isn’t dust because dust can be seen, either when it’s blocking light from more remote sources, or when it’s being heated and emitting infrared.

  14. Ken G

    ioresult: dark matter is not thought to be made primarily of either neutrinos or black holes, but those are examples of dark matter.

    Bad Astronomer: Exciting take on dark matter. I’m not sure you can back up the loftier claims about the kinds of questions science can answer, however. Has there ever been a historical example of a question that it was widely regarded as unanswerable by science by people who understand what science is, say dating from the time of Galileo, that has been answered in the 4 centuries since? I don’t really think so, my guess is science actually understands less now than what Galileo would have expected it would by now (largely due to how much more surprising and complex the universe turned out to be than what he might have imagined, and that may always continue to be true).

  15. Cusp

    Sorry BA – there is no proof dark matter is “real” – there is observational evidence that 1/r^2 gravity does not work at large scales and there are several potential physical solutions to this, including dark matter, but also modified gravity etc. While many feel the observations point to a physical dark matter, there are of course those who are looking at the other alternatives.

    In truth, DM is a parameter of ignorance which may be physical matter or may indicate new physics.

  16. KC

    When the barely stable chaos known as family life threatens to spin out of control, I occasionally act as translator. It’s amazing how different parties can derive different meanings from the same question. The question “Where is my science hand-out” can, depending on whom you ask, devolve into deducing the probably location by process of elimination or a description of said hand-out. The question of the why of the universe is like that:

    “Why is there a universe?”

    “Well, as best as we can determine, everything seems to have emerged from a single point and –“

    “No, I mean, why is there a universe?”

    “Before the Big Bang? That’s a difficult question. Some think there was a collision between universes and –“

    “No: Why are we here?”

    The problem is in the meaning of the word “why.” To one the question is how, to the other the question is if there’s a purpose behind it. Science has a good track record at answering the first because it’s essentially a cause and effect question. Science isn’t very good at answering the second because it’s not addressed by the physical.

    Consider the Venus of Willendorf. We can determine that it’s made of limestone, that it was carved between 24,000 and 22,000 BC, that it was covered in red ochre, and that there are similar figures. But we can’t determine why they exist. Were they religious artifacts? Fertility symbols? Science can’t answer that. All we can do is speculate.

    Is this a knock on science? Hardly. The scientific method is a proven tool for investigating the universe and how it works. Yet just as dental floss makes a poor paint brush, science is a poor tool for jobs it’s not designed to do.

    One day we may know exactly how the universe formed and the laws of physics unified into one grand theory of how things work. But science will be no closer to the answer of whether all of it has meaning or not. But, then, that’s a question beyond science’s ability to answer.

  17. Modified gravity was pretty much ruled out by the data from the bullet cluster.

    Oh, and BA: SQUIDS are fine if you capitalize…

  18. Cusp

    > Modified gravity was pretty much ruled out by the data from the bullet cluster.

    Yes, the bullet cluster reaffirms the views of those who think dark matter is physical, but the entire community is not convinced – e.g.

    The Bullet Cluster 1E0657-558 evidence shows modified gravity in the absence of dark matter

    Brownstein, J. R.; Moffat, J. W.

    Affiliation:
    AA(Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5, Canada), AB(Department of Physics & Astronomy, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada)

    Publication:
    Monthly Notices of the Royal Astronomical Society, Volume 382, Issue 1, pp. 29-47. (MNRAS Homepage)

    Publication Date:
    11/2007

    Origin:
    MNRAS

    MNRAS Keywords:
    gravitation , gravitational lensing , galaxies: clusters: individual: 1E0657-558 , dark matter , X-rays: individual: 1E0657-558

    10.1111/j.1365-2966.2007.12275.x
    Bibliographic Code:
    2007MNRAS.382…29B

    Abstract
    A detailed analysis of the 2006 November 15 data release X-ray surface density ?-map and the strong and weak gravitational lensing convergence ?-map for the Bullet Cluster 1E0657-558 is performed and the results are compared with the predictions of a modified gravity (MOG) and dark matter. Our surface density ?-model is computed using a King ?-model density, and a mass profile of the main cluster and an isothermal temperature profile are determined by the MOG. We find that the main cluster thermal profile is nearly isothermal. The MOG prediction of the isothermal temperature of the main cluster is T = 15.5 +/- 3.9keV, in good agreement with the experimental value T = 14.8+2.0-1.7keV. Excellent fits to the 2D convergence ?-map data are obtained without non-baryonic dark matter, accounting for the 8? spatial offset between the ?-map and the ?-map reported in Clowe et al. The MOG prediction for the ?-map results in two baryonic components distributed across the Bullet Cluster 1E0657-558 with averaged mass fraction of 83 per cent intracluster medium (ICM) gas and 17 per cent galaxies. Conversely, the Newtonian dark matter ?-model has on average 76 per cent dark matter (neglecting the indeterminant contribution due to the galaxies) and 24 per cent ICM gas for a baryon to dark matter mass fraction of 0.32, a statistically significant result when compared to the predicted ?-cold dark matter cosmological baryon mass fraction of 0.176+0.019-0.012.

  19. Cusp

    > Modified gravity was pretty much ruled out by the data from the bullet cluster.

    Yes, the bullet cluster reaffirms the views of those who think dark matter is physical, but the entire community is not convinced – e.g.

    The Bullet Cluster 1E0657-558 evidence shows modified gravity in the absence of dark matter

    Brownstein, J. R.; Moffat, J. W.

    Monthly Notices of the Royal Astronomical Society, Volume 382, Issue 1, pp. 29-47.

    Abstract
    A detailed analysis of the 2006 November 15 data release X-ray surface density s-map and the strong and weak gravitational lensing convergence ?-map for the Bullet Cluster 1E0657-558 is performed and the results are compared with the predictions of a modified gravity (MOG) and dark matter. Our surface density s-model is computed using a King ?-model density, and a mass profile of the main cluster and an isothermal temperature profile are determined by the MOG. We find that the main cluster thermal profile is nearly isothermal. The MOG prediction of the isothermal temperature of the main cluster is T = 15.5 +/- 3.9keV, in good agreement with the experimental value T = 14.8+2.0-1.7keV. Excellent fits to the 2D convergence ?-map data are obtained without non-baryonic dark matter, accounting for the 8? spatial offset between the ?-map and the ?-map reported in Clowe et al. The MOG prediction for the ?-map results in two baryonic components distributed across the Bullet Cluster 1E0657-558 with averaged mass fraction of 83 per cent intracluster medium (ICM) gas and 17 per cent galaxies. Conversely, the Newtonian dark matter ?-model has on average 76 per cent dark matter (neglecting the indeterminant contribution due to the galaxies) and 24 per cent ICM gas for a baryon to dark matter mass fraction of 0.32, a statistically significant result when compared to the predicted ?-cold dark matter cosmological baryon mass fraction of 0.176+0.019-0.012.

  20. Cusp

    > Modified gravity was pretty much ruled out by the data from the bullet cluster.

    Yes, the bullet cluster reaffirms the views of those who think dark matter is physical, but the entire community is not convinced – e.g.

    The Bullet Cluster 1E0657-558 evidence shows modified gravity in the absence of dark matter

    Brownstein, J. R.; Moffat, J. W.

    Monthly Notices of the Royal Astronomical Society, Volume 382, Issue 1, pp. 29-47.

    Abstract
    A detailed analysis of the 2006 November 15 data release X-ray surface density s-map and the strong and weak gravitational lensing convergence k-map for the Bullet Cluster 1E0657-558 is performed and the results are compared with the predictions of a modified gravity (MOG) and dark matter. Our surface density s-model is computed using a King b-model density, and a mass profile of the main cluster and an isothermal temperature profile are determined by the MOG. We find that the main cluster thermal profile is nearly isothermal. The MOG prediction of the isothermal temperature of the main cluster is T = 15.5 +/- 3.9keV, in good agreement with the experimental value T = 14.8+2.0-1.7keV. Excellent fits to the 2D convergence S-map data are obtained without non-baryonic dark matter, accounting for the 8? spatial offset between the s-map and the k-map reported in Clowe et al. The MOG prediction for the k-map results in two baryonic components distributed across the Bullet Cluster 1E0657-558 with averaged mass fraction of 83 per cent intracluster medium (ICM) gas and 17 per cent galaxies. Conversely, the Newtonian dark matter k-model has on average 76 per cent dark matter (neglecting the indeterminant contribution due to the galaxies) and 24 per cent ICM gas for a baryon to dark matter mass fraction of 0.32, a statistically significant result when compared to the predicted l-cold dark matter cosmological baryon mass fraction of 0.176+0.019-0.012.

  21. Cusp

    > Modified gravity was pretty much ruled out by the data from the bullet cluster.

    Yes, the bullet cluster reaffirms the views of those who think dark matter is physical, but the entire community is not convinced – e.g.

    The Bullet Cluster 1E0657-558 evidence shows modified gravity in the absence of dark matter

    Brownstein, J. R.; Moffat, J. W.

    Monthly Notices of the Royal Astronomical Society, Volume 382, Issue 1, pp. 29-47.

    Abstract
    A detailed analysis of the 2006 November 15 data release X-ray surface density s-map and the strong and weak gravitational lensing convergence k-map for the Bullet Cluster 1E0657-558 is performed and the results are compared with the predictions of a modified gravity (MOG) and dark matter (abridged)

  22. Cusp

    [Sorry for the multiple posts]

  23. Cusp: Sean @ Cosmic Variance had a post about this. The general agreement seems to be that while MOND can account for individual observations, it has a hard time explaining all observations. Baryonic matter has been conclusively ruled out. Add to that the need in particle physics for heavy supersymmetric partners in the ground state, and you have seveal branches of physics all pointing in the same direction: nonbaryonic dark matter.

  24. Cusp

    Pieter – I assure you I am very much in the field (organizing a major international conference on dark matter in particle and astrophysics last year). I also understand gravitational lensing and clusters well. As I said, I agree that the signs point to dark matter being a physical substance, but there is no conclusive proof that it is -

    Our understanding of gravity could be wrong and people are looking at this.

    Even if the LHC spits out a single heavy supersymmetric particle (and not everyone thinks it will) – this will not be “proof” that it is dark matter – it will be a candidate for dark matter.

    I’m sure a number of people think that dark energy is equally physical, but again, there is a community that disagrees (read the recent work on the illusion of dark energy due to relativistic back reaction).

    Until there is conclusive proof one way or the other, dark matter remains a parameterization of ignorance.

  25. Ivo

    If weak interacting particles interact weak with other particles, why should they explain 75% of the gravity-gap in the universe? This just seems counterintuitive.

    why does the scientific community assumes a uniform elasticity of space and try to explain gravity anomalies with unelegant things like dark matter? It makes little sense to me.

    Why do religious people think they have a monopoly on the ultimate “why” question and why do we always try to find an explanation for the things that happen around us?

    enlighten me.

  26. Cusp

    > If weak interacting particles interact weak with other particles, why should they explain 75% of the gravity-gap in the universe? This just seems counterintuitive.

    They don’t – they interact gravitationally.

  27. I like your phrase “parameterization of ignorance” (I may borrow it), but remember that it applies in principle to all scientific theories: not much is conclusively proved. My impression is that we are in the middle of a paradigm shift (a la Kuhn) towards the acceptance of dark matter as fact: Some have embraced it already, and some still vigorously resist the idea. And there will always be people who will never accept it. They will just have to die for progress to take place… ;-)

  28. Phil wrote:

    “We also know it’s not made of normal matter, like anything made up of electrons, neutrons, or protons. The effects we see would be very different if it were,”

    How WOULD the effects be different if Dark Matter were made of ordinary stuff?

  29. Thanks

    Great article, great blog.

  30. Cusp

    I agree Pieter – although I wish the public were more evidence driven, rather than such-and-such as being a fact. The evidence is squarely on the side of dark matter being physical, but in my public talks I stress this and that there is the possability (however remote) that it will all be chucked in the bin in the future.

    As for parameterization of ignorance – Seeing I pinched it off someone else, I’m more than happy for you to use it :)

  31. Cusp

    > How WOULD the effects be different if Dark Matter were made of ordinary stuff?

    It would not be dark. Normal matter is happy to interact with photons and so it would glow. Even cold rocks would glow in the IR and be visible to IR telescopes.

    It’s very difficult to make matter not glow.

  32. What principle do these detectors work on? How do you design a device to detect something when you have no idea what the “something” is?

    How can you tell the difference between a nucleus “ringing” from a DM hit vs. one that’s been hit by some other random particle?

    Is this anything like neutrino detectors that have to be buried to screen out all of the “normal” exotic particles? Can they tell the difference between DM and neutrinos?

    - Jack

  33. Now for a moment of humor:

    Do WIMPs gladly pay you Tuesday for a hamburger today?

    (too obscure?)

    J/P=?

  34. JeffF

    As a senior grad student on CDMS, thanks so much for the publicity! It’s really fantastic to see our work showing up here, and thus working its way to the public eye.

    A couple of comments:

    Phil: I’m sorry to complain, but your characterization of the result isn’t quite right. It’s still possible that dark matter could be composed of particles heavier than 100x the proton mass – as Dave C points out, they just need to interact weakly enough. Our result sets the strictest constraints to date on such interactions in this mass range, but lower interaction rates are still possible.

    Stuart: As you say, numerous institutions were involved in this work – you can see the bunch on the author list of our preprint (linked above). The spokesperson of the current CDMS experiment is Bernard Sadoulet from Berkeley, with Blas Cabrera as the Co-Spokesperson. The superconducting sensors developed by the Cabrera group are critical components of CDMS’s success, but as a Berkeley-ite I should note that the first iterations of CDMS detectors came out of Berkeley. :)

  35. JeffF

    In reply to Jack Hagerty:

    Roughly speaking, the detectors work by measuring two attributes of each particle impact: the heat deposited and the ionization generated (number of electrons knocked free from their orbits). The ratio of these two tells you whether the particle collided with an atomic nucleus or with atomic electrons. The “ringing” looks different in these two cases.

    This is how we can look for a dark matter particle without knowing exactly what it is. Any sufficiently heavy particle (~100x the proton mass in most theories) moving at galactic orbital velocities should deposit energy more effectively in collisions with heavy nuclei than with light electrons. Even if we don’t know exactly what the dark matter is, we’re still looking for nuclear impacts and these are actually very rare – most backgrounds from radioactivity transfer energy to electrons.

    We bury these detectors underground for the same reason that neutrino detectors are underground – the particles we’re looking for can still get there, but most cosmic rays can’t. We’re particularly worried about keeping away neutrons induced by cosmic rays, since these cause nuclear impacts that can fool our detectors.

    Neutrinos are light, depending on their energy they can cause electron or nuclear impacts. They’re not a major issue until we build much bigger experiments.

  36. SQUIDs???

    Shame on you. We don’t talk about that kind of stuff here.

    Oi!

    How do we know that the indirect effects we are seeing are not due to the collective effect of a bunch of fairly small (e.g. dust-sized) particles that we just can’t see with our telescopes, instead of this fundamentally different type of matter?

    We’d be able to detect the effects of objects moving through this normal matter. Things would leave “wakes”. Gravity would twist the stuff into clumps, and the clumps would pass between us and other objects, causing little occultations. Bright objects would light up the dust (like zodiacal light).

    /
    /
    /
    /
    /
    ////
    / / /

    Hmm, it is much harder to draw an ascii squid than I imagined it would be in this typeface.

  37. shane

    How and why will be answered when we have all the science. As someone said once we just don’t have all the science. How is most important and will probably go much of the way to explaining why.

    Why is a metaphysical pejorative used by religiotards against the reality based community when faced with the inadequacies of their own answer “goddidit”.

  38. csrster

    I wouldn’t be as combative about it as shane, but I think some of the “skeptical” comments on this thread are a bit off in their understanding of how science works. “Dark Matter” is a theory – or rather a collection of theories – which a) explain a significant body of observations and b) have been used successfully to predict new observations. The comparison with the lumeniferous ether is instructive. The ether theory was eventually brought down by a combinations of new observations which apparently contradicted it and a new theory which encompassed all the existing phenomena _and_ made new and testable predictions. Incredulity of the “your just making this stuff up” variety didn’t contribute to the death of the ether and isn’t helpful in discussing dark matter either.

  39. Jeffersonian

    @KC
    “Science isn’t very good at answering the second because it’s not addressed by the physical.”

    Science, no, but math, yes!
    Random probability; the same thing that effected how your day came out and how tomorrow will, too. The problem lies in the people who hold a grudge against accepting the answer due to indoctrinated beliefs or the feeling the universe somehow owes them more.

    “Consider the Venus of Willendorf”
    After studying Native American petroglyphs, I came to the conclusion that there doesn’t need to be a why to this. In any given culture there are artists. There’s always gonna be a person who is left-brained and just wants to create for no reason. Man’s brain has not changed, in this respect, for millenia. So, science can answer this in the fields of Connectomics, Sociology and Anthropology but, ultimately, it’s going to be problematic to answer questions of art with science.

  40. Pat

    With ether, as with any of these, the idea is to make testable predictions. With collisionless CDM, we’ve tried to set up some limits on what we should see, and test that in rigorous conditions designed to eliminate false positives. Kind of like gravitational waves, for which we also have a few tests. Ether ran into issues with whether it was “stiff” because of how light behaves, and, if so, how it interacted with normal matter.

    We still have a lot of odd behaviors, such as the “hollow” profile of DM “shells,” some ellipticals that appear to have no DM, and so on. MoND would not allow for galaxies with no DM, collisionless particles cause problems as well. Some small irregular galaxies have DM profiles to their core. It’s the variance and exceptions that keep causing the hubub.

  41. AlexBenj

    There may be different types of dark matter, interacting strongly gravitationally and weakly via some other forces, producing different observation results.

    Or maybe all of dark matter is ordinary matter separated by branes but able to interact via gravity.

    Or it’s just spilled fairy dust from some deity’s bag.

  42. shane writes:

    [[Why is a metaphysical pejorative used by religiotards against the reality based community when faced with the inadequacies of their own answer “goddidit”.]]

    No, it’s an interrogative pronoun asking about motivation, purpose, or first cause.

    Hey, “religiotards” is an interesting one. You manage to slander theists and mentally handicapped people in one word.

  43. Rick Johnson

    For those that are interested you can tour both the abandoned iron mine and the CDMS lab in the summer. Many tours per day are offered. The mine is now a Minnesota State Park — no park permit needed however there is a fee for each tour.

    http://www.dnr.state.mn.us/state_parks/soudan_underground_mine/index.html
    http://www.dnr.state.mn.us/state_parks/soudan_underground_mine/physicslab.html

    When looking at the pictures of the lab remember all of it went down the same small mine elevator you take a half mile down to the lab! Quite a feat in its own right. Neutrino and proton decay research is also done in the lab.

    I live in northern Minnesota so I’ve been down and it’s well worth the trip if you are ever in the area. It was just a neutrino lab when I was there last so I plan a return visit this summer.

    Rick

  44. SkepticTim

    Interesting: but hasn’t the intriguing possibility of unparticles been left out in the cold here? After all, if these things exist, An unparticle does not have one given mass, but can take on any possible mass or have all possible masses at the same time, depending on how you look at it.

    SQUIDs??? So what’s wrong with Superconducting QUantum Interference Devices (SQUIDS) – the users of MRIs and geophysical magneto-telluric devices would be dismayed!

  45. TheBlackCat

    No, it’s an interrogative pronoun asking about motivation, purpose, or first cause.

    No, it’s an interrogative pronoun assuming motivation or purpose. If there is no motivation or purpose then there is no “why”. Asking the question “why” is only meaningful if you assume that there is a “why” to begin with, something that is far from certain.

    A first cause, if such a thing even exists, does not require a “why” because it does not require motivation or purpose. A first cause that was purely random or inevitable from a purely mechanical standpoint does not have a “why” at least in the sense that it is normally asked (that is, asking what the motivation or purpose is behind something). Some religions, including abrahamic ones, assign motivation and purpose to their supposed first cause but this is not universal even amongst religions.

  46. JeffF says: “In reply to Jack Hagerty:
    Roughly speaking, the detectors work by measuring two attributes of each particle impact…”

    Thank you! I knew that someone would 1) have the answer, and 2) know that my questions were serious.

    - Jack

  47. Pat

    Rick:
    CDMS needs a new logo : ) The MINOS logo kicks its keester…

  48. Tom Marking

    http://en.wikipedia.org/wiki/Pioneer_anomaly

    Assuming that the so-called Pioneer anomaly is real then would any of the proposed theories for dark matter such as WIMPs explain it? Could you have enough WIMPs in a volume the size of the solar system to affect the trajectory of spacecraft to the measured amount? – which appears to be a sunward acceleration for both the Pioneer 10 and 11 spacecraft of 8.74E-10 m/s^2 which is anomalous under existing theories of physics.

  49. You know, reading this, it seems that while dark matter is a theory, so far WIMPs are more of a hypothesis.

  50. Oratio

    Well, it is important to remember that the theory about dark matter isnt a fact until they find WIMPs or some other particle turning out to be the actual alleged dark matter. There is also the thoery of “TeVeS”, that is worth checking out. Dont just accept everything that is put to print, dont turn science into religion. Be critical to everything until its utterly proven.

  51. All this is so confusing to a layperson. I am not a physicist, mathematician or astronomer. The only physics/maths I did was up to year twelve. However everyone has become so esoteric in each field how could you pass a new theory or concept to the general community? Everyone speaks in acronyms and synonyms. Please (for a layperson) keep it simple. There are questions that puzzle me. Therefore, I am asking if anyone out there is kind enough to respond to the following questions:

    Dark Matter / Dark Energy: is this what pre-Einstein ether was?
    Was Tesla right and Einstein wrong?
    Why did Einstein have to twig his original theory on relativity? Could both his theories be wrong?
    From what I remember, light rays/waves (and all the spectrum of waves) can self propagate through space because they are made up of magnetic and energy fields (at right angles to each other). What happens if the magnetic field is taken away to the energy field in waves and vice versa? Firstly, can this be done or am I way off here? Does Bark Matter have anything to do with the propagation of magnetic or energy or both fields?

    One thing that I do not understand is the big bang theory. Apparently, (from what I hear and read) at one stage in time all matter was condensed and an explosion occurred and the universe developed with all its galaxies, stars, planets etc and due to the big bang the universe is expanding.

    Then, where was the dark matter when all was one big mass?
    Was the Dark Matter mixed with the Matter we know off, or did the Dark Matter encompass the matter we know off?
    Are the galaxies moving apart because the dark matter is “pushing them apart”?

    Is Dark Matter expanding too, as the Universe (if it is matter)? If not, then does it mean it was present before, and after the Big Bang?

    What if all matter is removed from the universe does it mean that Dark Matter is what is left?

    It can’t be a particle or energy, remembering that E=MC2. Am I wrong here?

    Is E=MC2 too simplistic?

  52. First of all, thanks for your articles, they’re quite popular and accessible.

    > The very small and the very big are connected in a fundamental way, and it’s only been through science that we’ve perceived that connection.

    ‘We’ as the whole WoMankind? Or just the scientific community? ,)
    Spiritual (and I don’t think it’s a very bad word (Philip Says), as far as words go) investigators, that go more by the ways of feeling and sensing oneself + Universe, than by logging down and analyzing, have perceived it thousands of years ago.

    In no way do I mean that as offense, on the contrary, I rejoice seeing science and spiritual discovering more and more points of intersection.

  53. Bobby

    I have no credentials for typing this and please excuse the typos, I just have an idea…that’s all and any feedback would be apreciated.

    I’ve decided that dark matter wants to turn every piece of matter inside out. I think that’s what makes gravity…. Dark matter is gravity without the matter. So take everything out of the universe. No big bang, no matter, no gas, no anything. There wouldn’t be any gravity because dark matter has nothing to pull on. Then put a spec of dust in space…and dark matter already pulls on it and this spec now has a little gravity. Because dark matter is all around, it pulls in every direction, so put a planet in the universe now…and it wants to pull everything to the center. Now fast forward and put more matter in the universe… Everything (that isn’t already attatched to something else) will have gravity all on it’s own in outer space. Just like planets and solar systems colliding, galaxies collide too. Because there is no wind resistance and everything is free to float around in the fabric of space, leads me to think 2 things….Either one day everything in the universe (if it can be counted for) will come together into one ball. The density and mass will be so great it will pull so hard on itself creating massive ammounts of heat and energy that it will again “blow up”. Kinda like when large stars blow up then make black holes. 2 Just like the first part..the big ball of matter will pull so hard on itslef that it will be reduced to something so small and dense that dark matter will pull on it so hard it would be blown out of the other side of where this dark matter is trying to pull everything. But if it’s blown out of the other side, I would think things would start all over again…Just like the infinity sign.

    Think of it like magnetism…the opposite poles attract eachother. Now throw in a spec of magnetized dust. Do you think it would one day get stuck in the middle of the “infinity” sign or just keep traveling back and forth between the poles. Put 2 specs of magnetized dust now. Eventually they would attract to each other and become one big piece of dust with a stronger N. and S. pull. Now put a ton of magnetised dust in the infinity sign. would it just travel forever between the poles or would it get stuck in the middle one day and have each pole pulling its opposite pole on the piece of dust. Now give the infinity sign an unlimited ammount of magnetic pull. The harder the poles pulled the more dense the piece of dust would get….so much in fact that it would get hot and the core would turn to liquid.

    So the stronger the pull from the outside, the stronger the pull on the inside. Like a knot that gets pulled equally as hard on both sides of the rope…the tighter the knot is. Now this pulls so hard that eventually one side of the rope will break. But the universe is not a rope….so what happens? This applies to everything from planets to stars to galaxies and even to particles.

NEW ON DISCOVER
OPEN
CITIZEN SCIENCE
ADVERTISEMENT

Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!

ADVERTISEMENT

See More

ADVERTISEMENT
Collapse bottom bar
+

Login to your Account

X
E-mail address:
Password:
Remember me
Forgot your password?
No problem. Click here to have it e-mailed to you.

Not Registered Yet?

Register now for FREE. Registration only takes a few minutes to complete. Register now »