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Most Sensitive Detector Yet Fails To Find Any Signs of Dark Matter
ananyo writes "A U.S. team that claims to have built the world's most sensitive dark matter detector has completed its first data run without seeing any sign of the stuff. In a webcast presentation today at the Sanford Underground Laboratory in Lead, South Dakota, physicists working on the Large Underground Xenon (LUX) experiment said they had seen nothing statistically compelling in 110 days of data-taking. 'We find absolutely no events consistent with any kind of dark matter,' says LUX co-spokesman Rick Gaitskell, a physicist at Brown University in Providence, Rhode Island. Physicists know from astronomical observations that 85% of the Universe's matter is dark, making itself known only through its gravitational pull on conventional matter. Some think it may also engage in weak but detectable collisions with ordinary matter, and several direct detection experiments have reported tantalizing hints of these candidate dark matter particles, known as WIMPs (Weakly Interacting Massive Particles). Gaitskell says that it is now overwhelmingly likely that earlier sightings were statistical fluctuations. Despite the no-shows at XENON-100 and LUX, Laura Baudis, a physicist on XENON-100 at the University of Zurich in Switzerland, says physicists are not ready to give up on the idea of detecting WIMPs. They may simply have a lower mass, or may be more weakly interacting than originally hoped. 'We have some way to go,' she says."
Pulling in other posts below it :D
"When information is power, privacy is freedom" - Jah-Wren Ryel
Just sayin'...
Maybe it's just not there.
Dark matter always reminds of the 18th century hypothesis of the aether.
http://en.m.wikipedia.org/wiki/Luminiferous_aether
Same principle. Same made up matter that no one can see or detect but somehow fills the entire universe.
from the article :
"... physicists are not ready to give up on the idea of detecting WIMPs. They may simply have a lower mass, or may be more weakly interacting than originally hoped....We have some way to go"
So former wimps are having a hard time finding WIMPs themselves? That's an interesting turn of events !!
What is best in life? To crush your enemies, to see them driven before you and to hear the lamentations of their women.
...that maybe they're not seeing it because it's just not there?
Just a suggestion.
So undetected dark matter pulling stuff together more than expected and undetected dark energy pulling stuff apart more than expected.
Hmmm. Isn't it possible that the theory is just wrong about how gravity and spacetime works at really large scales?
Where are we going and why are we in a handbasket?
Usually it is in and around the drumstick area.
Dark matter experiments sometimes remind me of the luminiferous aether theory experiments of the 19th century. After a certain number of tests fail to return a result you start to suspect that the experiment is working perfectly it's just that there's nothing to detect and something is fundamentally flawed with your theory.
clearly it's too dark to see so they should just use a flashlight.
Anons need not reply. Questions end with a question mark.
The SANTA and EASTER BUNNY teams are also reporting negative results today. Film at 11.
Circle the wagons and fire inward. Entropy increases without bounds.
from astronomical observations that 85% of the Universe's matter is dark"
They don't *know*, they're deducing this from reconciling observed data with general relativity but it's far from certain.
However relativity is not infallible, maybe it's true only in a special case -- like how Newtonian mechanics works great but only in a special case (bigger size than quantum scale, less velocity than ~1/10 c, etc)
Maybe at very large size and mass such as galaxies, general relativity doesn't hold and there's a better theory for explaining motion and gravity. If so we wouldn't have to invent nonexistent dark matter to account for the faster-than-expected galactic rotation and other things.
Several different experiments have tried to measure dark matter directly in the lab, and the experimental situation is pretty confusing. This plot shows the confidence intervals and exclusion limits for various experiments (but it does not include LUX yet). The shaded regions are confidence intervals, that basically say "we've seen dark matter, and its properties lie somewhere in this region. But the dotted lines say "we haven't seen it, and if it exists, it can't lie above these lines".
What is strange, then, is that all of the detections are in regions that have been excluded by other experiements. LUX just makes the situation even more strained by pulling those upper bounds even lower. Still, those bounds and intervals depend on assumptions about the properties of dark matter, and it may be possible to reconcile the results.
It will be interesting to see what happens to those tentative detections when they get more data. My bet is that in the end some systematic effect will be found to be responsible for the apparent signal. Or (much less likely) that they were just flukes. But who knows?
unless you are using DOS
if this is supposed to be a new economy, how come they still want my old fashioned money?
Matter of fact, it's all dark.
The dark matter theory has always felt a bit contrived to me. But I don't have the background to make an cogent argument against it, nor have standing for my words to carry weight.
Gravitational lensing.
(And I'm kidding here:) You can't explain that!
Of course they hadn't considered it earlier! What fools they've been shown to be!
(Hint: If you're a random commenter on Slashdot, then, yeah, the experts in the field have probably considered your idea before you suggested it.)
HAND.
it's spiders.
teeny-weeny black spiders.
hundreds of Quattuordecillions of teeny-weeny black spiders per cubic centimeter, crawling between the very fabric of creation.
crawling in your ear, in your eye.
SPIDERS.
the preceding comment is my own and in no way reflects the opinion of the Joint Chiefs of Staff
This has been bugging me for years, but I don't understand enough to either substantiate or falsify my thoughts. I also don't want to try and convince people that it's right since it sounds crazy even to me, but please tell me if you can find something wrong with it... I know that there are some extensive theories and observations involved, and I'm very aware of the relevant xkcd... http://xkcd.com/675/
All that said, it's very interesting to consider the possibility that there's a common cause of the observations that prompted dark matter/energy theories. I've read far too much about physics on Wikipedia trying to disprove the notion, with little success. All I've managed to do is find more and more curious aspects of things that would be *solved* by the idea.
I'd be very interested in someone finding evidence to falsify the possibility of dark matter and energy sharing a common anti-gravitational cause. I've been trying to find a contradiction for a very long time, and have found nothing conclusive.
If we consider that the anti-gravity could be caused by the missing antimatter purportedly absent due to baryogenesis, we might expect to find annihilation emissions in the spectra (Hmmm... http://en.wikipedia.org/wiki/Space_roar ? Doubtful, but who knows?). However, such an observation could be absent for at least two possible reasons: It doesn't exist...or the bulk of the antimatter is something weakly interacting and low-mass, sharing the same problem as the standard dark matter model.
I don't mean that antimatter would fall up in such a changed model. Its inertial mass could behave as expected, and follow spacetime the same way as normal matter. It would just exert repulsive influence. Galaxies would be compressed by rings (or spheres, how dark matter is modeled?) of antimatter surrounding them and spread out somewhat in intergalactic space (dark matter), while being repelled from each other by the spherical gravitational dipole effect (dark energy).
If you model a binary system with one matter and one antimatter particle, they orbit a barycenter on the opposite side of the matter particle from the antimatter particle...in lock-step with each other. Put a black hole at that barycenter, add more particles of each type, and you get an orbiting system that goes much faster than it should from just the matter...just like dark matter's effects on galaxies.
There's some amazing symmetry if you think about this, and some weird implications. Inertial and gravitational mass would no longer be identical. Relativistic mass might be gravitationally neutral. An antimatter particle would chase a matter particle and require new interpretations of conservation of energy (Probably one of the biggest potential arguments against the whole concept, except it violates assumptions, not any evidence I'm aware of).
My most recent consideration from all this was the idea of applying CPT symmetry to the big bang (since it could be expected to involve both matter and antimatter), with some truly crazy implications. Unfortunately my understanding of it seems to be even more lacking than I thought, and I'm not sure how to mathematically formulate/test the possibility of the Universe sharing a common beginning and ending if you look at matter and antimatter versions in opposite time-space terms.
I don't know what I'm doing, and really wish someone could put this musing to rest one way or another. Unfortunately, I doubt we really have the experimental evidence either way. All of my musings amount to relaxation of assumptions--I haven't found a concrete contradiction, and all the predicted effects seem too subtle for current experiments to show.
If anyone could give good evidence for falsification of this common cause hypothesis, or point me in a direction for finding it, I'd be very appreciative. I've spent far too much time thinking about this with nothing to show for it, despite trying to break it.
Thanks for reading. Please get this out of my head. :P
I still think it is lots of baryonic matter in black holes or whatever, aka MACHOs(Massive Compact Halo Object).
Anytime I lose something in the dark I just get a bigger flashlight. All we need to do is launch a giant version of those 30 LED flashlights you can get at Harbor Freight for like $2. It has to be in pink though just to make it pretty.
Harrison's Postulate - "For every action there is an equal and opposite criticism"
Was she scared of gravity as a child or something? Too much falling down perhaps?
Harrison's Postulate - "For every action there is an equal and opposite criticism"
The main lines of evidence for dark matter:
* Galactic rotation curves
* Velocity distribution in clusters of galaxies
* Gravitational lensing in general
* The Bullet Cluster in particular
* The pattern of positions of galaxies in the universe
* The pattern of Baryon-acoustic oscillations in the cosmic microwave background and in the galaxy distribution
* The primordial distribution of light elements in the universe
We know of some kinds of dark matter already: There is a huge amount of neutrinos left over from the big bang, and since these interact very weakly with other stuff, they definitely qualify as dark. Other known kinds of dark matter are black holes, and compact, cold objects made out of baryons (normal matter). So dark matter exists.
The problem is that there isn't enough of the normal kinds of dark matter. To match the pattern in the cosmic microwave background and the amount of hydrogen, helium and lithium in the universe, one needs by far most of the dark matter to be non-baryonic (i.e. not normal matter, but something like neutrinos, but heavier). This kind of dark matter is something we have to postulate exists in order to match observations. But when we do assume it exists, the theory matches observations extremely well. As an example, look at the CMB power spectrum as mesured by Planck. The error bars are so small that you mostly can't see them, and the points lie smack on top of the theory curve. But only if dark matter is included.
And it just so happens that the amount of dark matter that makes theory match the points in that graph also makes the element abundances, galaxy distribution, lensing observations and galaxy cluster velocities work too. Such a coincidence is pretty telling, I think.
But yes, people have tried to avoid dark matter by modifying gravity instead (though nowadays, the most common motivation for modifying graivty is to avoid dark energy). MOND is an example of that. MOND is like normal Newtonian gravity as long as the gravitational acceleration is large (like in the solar system), but instead of falling to arbitrarily low values as distances increase, the gravitational acceleration has an effective minimal value that it approaches as you move away. And such a constant value is just what you need to get the flat rotation curves we observe in galaxies. Which is the problem MOND was invented to solve.
MOND is an elegant solution for galaxies, but it loses all its elegance and predictive power when you try to apply it to the other areas where dark matter shows up. And in some cases it is plainly ruled out as an explanation. MOND, like Newtonian gravity, is a central force, which means that the force points towards the mass that generated it. But in the Bullet cluster, the gravitational force points towards areas with little visible matter, away from areas with much visible matter. This is impossible to fit into MOND. So the Bullet cluster basically killed MOND.
Some of MOND lives on in TeVES, which is an attempt at a relativistic version of MOND. Sadly TeVES has none of the simplicity and elegance of MOND, and while it can explai
Not usually one to support AC but yes, I checked the 'turn off adds' box tonight because I really don't want to have pornographic Korean games shoved down my throat (ahem). Fix it please /.
"Our opponent is an alien starship packed with atomic bombs," I said. "we have a protractor"
I think he just misunderstood when she didn't want to go down on him.
Everything is better with chainsaws.
It's not going to do you any good looking for the Dark Matter here.
I'm keeping it safe and sound on the Dark Side of the Moon.
Oh, and next time use a flashlight.
-- Tigger warning: This post may contain tiggers! --
Or dark energy. Or black holes. Or machos. Or wimps. or whatever other mathematical fantasy they dream up to patch the ever widening gap between observations and an outdated theory.
Because we live in an electric universe. Because the electric force is orders of magnitude stronger than gravity.
"The Electric Sky" explains many many things that surprise those still worshiping the standard model as if it were gospel.
http://amzn.com/0977285111
There is no dark matter. Changing our view of the nature of space can however explain what we observe. Einstein tried to show the way when he described gravity as the deformation of space.
We incorrectly deduce that there must be unseen mass because the outer edges of galaxies move at a rate that implies missing mass. We use the doppler shift of light to measure the speed of the stars in the galaxy. We assume that the speed of light and the speed of gravity are the same as they pass through the usual three dimensions of space. In a theoretical vacuum this may be true, but we live in a universe filled with matter and charged particles.
By changing our assumption and considering space as two three dimensional fields, electrostatic and gravitational that are superimposed upon each other we can easily reconcile what we see. The galactic center has a stronger gravitational field than the outer edge of the galaxy and gravitational space is compressed relative to electrostatic space. When we use light as a yardstick we fail take into consideration that the galactic gravitational field is compressed where the galactic electrostatic field is not.
This the Electro-Gravitic theory of space and provides a clear explanation for dark matter, dark energy, refraction and the unification of the strong force and gravity without resorting to anything we have not already proven experimentally or incredibly complex math that defies human understanding.
Greed is the root of all evil.
Does temperature affect gravity? What about light, does heat or cold affect the speed or strength of light beams? /Stolzy
I think there is an ether. It is not "particles", hence the difficulty measuring it, but energy -- thus explaining the 10^^120 discrepancy in the measured vs. calculated background temperature.
- Floyd Maxwell, author of "Spring-And-Loop Theory"
I come here for the love
If they would just reconfigure the main deflector to emit a tachyon pulse...
Sean Carroll's "Dark Matter, Dark Energy" Great Course to the rescue. Like all GC's, it is very expensive, but libraries seem to have it.
I come here for the love
It's awfully hard to detect a math error with a physical sensor.
Yep!
And at the 2012 Electric Universe Conference in Las Vegas, I got to see a lecture by a renowned astrophysicist / astronomer who found a cluster of stars supposedly orbiting around a black hole at a phenomenal speed. In fact, when astronomers calculated the speed one of the stars was whipping around the supposed black hole, it came out to a staggering 2.5x the speed of light. It's photographic evidence over the course of many weeks that is very hard to debunk.
Now, if an entire star system can be flung into FTL speeds, i think that paints a pretty rosy picture for far less massive spacecraft, you know?
Slashdot Valentines Beta Massacre: iT WORKED! The boycotts killed Beta!!
On occation, I've made a note to disable central air, close windows, keep out sunlight, and ignore high temperature fluxuating days, and would almost always catch *something*.
I've come to a few theories as to why these things move. Static, The moon, ELF waves, and possibly dark matter.
The key to catching these things is to use an older , non compressing, non high defitioning camera, and use a very low threshold (few pixel changes causes capture ) on the capture software.
Either:
A. There is a fundamental aspect of space/time we don't understand. (Maybe there is some type of Aether?)
B. We don't understand gravity over long distances. (Maybe it has a different effect over longer distances than we are aware)
C. We are not measuring something else properly. Light, time, distance....?
This whole "dark matter" thing has been unreasonably preposterous from the word go.
I hold very few opinions. I hold information based on observation and fact. If you wish to disagree, please use facts.
Neither electric fields, magnetic fields nor gravity fields consist of particles. So perhaps we ought to call it dark energy. It might form a "gravity-dark energy" pair analogous to electro-magnetism.
Much as magnetic fields interact with electric fields, perhaps dark energy interacts with gravity, giving us indications of it, but not being measurable using particle detectors (as the one described in the article).
Thoughts, anyone?
For 30 years the evidence that the SM is incomplete has been building. This result, which frankly I didn't expect, seems like the final nail in the coffin.
The sad thing, of course, is that we have no model for anything else. Nor have we figured out any tests that might find new physics. We've spent the last 30 years building machines to tell us what we already knew.
The happy part of the story is that it's the low-cost machines like this, and telescopes, that keep putting out the real physics.
Wouldn't it be simpler to revise the laws of gravity at astronomical distances rather then dream up some ridiculous, invisible massive particle?
I really hope someone on here can explain what I'm missing here...
Why is it not possible that "dark matter" is not simply just regular matter like asteroids, comets, planets, nebulae, and neutrinos?
I mean, they're discovering exoplanets at an alarming rate lately and we're still discovering asteroids and comets in our own solar system. Extrapolating these findings to all the other stars out there has got to add up to something substantial, right?
What about stars that have exploded and spewed their contents across the universe? Would not these contents become dark after they cool, thereby making them invisible to us? That would be the entire mass of a star that we couldn't see, right? And there's got to be billions upon billions of these, depending on how far away into the past we're looking, right?
Then there are neutrinos, which we know exist because we can detect them, but do we really know how many of them are out there?
Surely, the mass of all of these normal types of matter would add up to something substantial... right?