Dark Matter WIMP Detection Claimed 167
Scientists at the University of Rome claim they have discovered evidence for Weakly Interacting Massive Particles (WIMPs). Their paper will be presented on Friday, and of course the verification process will take a while. The claimed particles weigh as much as a nickel atom, and could turn out to be the dark matter that astrophysicists have sought for so many years. All you touch and all you see may be only 20% of the universe. Read the
NYTstory (free reg. req.) and then visit the
TBTFblog
for detailed information.
Re:What can you do with WIMPs? (Score:1)
Could this "dark matter" really be the force, and could we detect disturbances in the force?
Oh sure, blame all the problems of the universe (Score:1)
DARK MATTER.
Oh, sure. DARK MATTER. BLACK HOLES. Endless pits where we can throw down "matter" ( = money ).
I love how these bastards are always trying to use racial parallels in everything to scare people. Would "gravitational hole" sound scary? NOOOO!! But BLACK HOLE, man, that sounds SCAAAARY. Better give us our research dollars.
DAAAAARRRRRK MATTER.
Oh, sure. Blame all the problems of the universe on the black man.
I love how lilly white academics are so quick to label everything black as if it's a problem instead of letting us manage our own destiny.
That's the problem with the academic types -- they claim to be open minded, but in reality their minds are just another kind of ghetto. Equal rights for us as long as we don't date their daughters.
I prefer the unmasked scorn of honest bigots to the rat-behind-your-back crap these acadmic liberals come up with.
What's next, rent control for Matter of Color?
80% of matter in universe? (Score:1)
so, maybe there's more matter out there than just dark?
No registration required... (Score:1)
NYTimes no-login (Score:1)
If instead you go to http://www10.nytimes.com/library/national/science/ 021900sci-dark-matter.html [nytimes.com], it will bring up the story, with no login and no cookies whatsoever.
Interesting.
Did you even read the article? (Score:1)
Did read the article? Have you ever taken a particle physics course? Do you even understand how science works? I don't mean to flame here, but frankly your quick dismissal of this possible discovery as bovine fecal material seems extremely premature.
As someone who actually has taken a course in QM (not particle physics in particular), I do know that interaction cross-sections depend on a number of factors, and mass is only one of them. And the mass is usually not even the most significant factor for calculating a cross-section. More often then not, a particle's charge (or lack thereof) is much more important than it's mass.
I think some healthy skepticism is warranted here, but an out-right dismissal is totally unfounded, at least until some other groups have had a chance to look over the data and attempt to confirm the experiment.
Re:Did you even read the article? (Score:1)
Gas in thermal equilibrium would still be detectable as very narrow, but strong aborption lines along the line of site to other galaxies. Such clouds of gas and dust have been detected, but not on the scale required to make up for the "missing" mass. Given that, I don't think the gas and dust explanation is strong enough, even though I do agree that it's still the simplest and therefore best explanation. Unfortunately, the data does not seem to bear that out right now.
I guess, ultimately, I have to question why you're judging this so harshly? It's a borderline personal attack, which IMHO is just in poor taste. These guys don't seem to be pulling a Pons and Fleischman here, and in fact I really don't see anything too unusual about thier press release either, given the fact that 90% of press releases end up completely misrepresenting the research anyway: A problem I had the misfortune of encountering about a year ago, there are some "editors" that I would love to see strung up by their finger-nails after the way they rewrote a press release I co-authored!
Re:Dark Matter (Score:2)
All right, Mr. Scientist, since you seem to be such an authority on the universe I'm sure we'd love to hear your theories. Why is the idea that there's more than one kind of matter so far-fetched?
For the paranoid "I never log in crowd" (Score:2)
P : slashdolt
works fine. They'll probebly kill it soon ( like
they did for cypherpunk & cypherpunks ).
What can you do with WIMPs? (Score:1)
the development "is just the tip of an incredible iceberg, if this is right."
So what can we do with the WIMPs? I hope
Re:What can you do with WIMPs? (Score:1)
Re:Dark Matter? (Score:1)
A simple experiment:
The elves surely must have some mass. Hmm... I wonder what the possability is that the keys were sucked out of existance by random weakly interacting antimatter collisions :-)
As for the difficulty of detection, wouldn't one of the active neutrino projects, like SNO pick up some very peculiar collisions if dense matter is going to occasionally interact and spew a photon? Off the cuff, wouldn't the intensity of photons released during collision of a neutrino differ greatly from that of an atom with the mass of Nickel, with an unspecified velocity?
Oh wait... it appears that's what they did... using seasonal fluctuations in the earth's velocity. That makes sense. I'll be quiet now.
Some day I'll have to get back into Physics.
...'n' MACHOs 'n' the Cosmological Constant (Score:2)
The missing mass needed to close the universe has always been assumed, I've assumed, to exist in the form of either WIMPs or MACHOs (massive compact halo objects) or the Cosmological Constant. Interesting times when evidence for all three is strengthening at once. The current Science News features a solid survey of the unanimity the remarkable idea of an accelerating universal expansion has garnered in just two years -- so much so that the current best-guess value for the CC, the push factor, is engraved on a plaque at the top of the spiral "walk through time" in the new Rose Center (formerly the Hayden Planetarium) in NYC. And convincing evidence for the existence of MACHOs was presented at the recent Atlanta meeting of the AAS. (I'll have links for all these loose ends when the next TBTF issue comes out.)
Re:Black and white aren't colors (Score:1)
When it comes to pigmeat, it's a question of tomato-based versus vineger-based.
Re:Did you even read the article? (Score:2)
Science works this way (compressed version): I say "Bullshit", you keep showing me evidence until I stop saying "bullshit".
The attitude to hold should be one of *utmost* skepticism. WIMPS are an extraordinary claim, and one should yell bullshit until we are shown extraordinary proof. I don't think the person you're replying to was dismissing at all. He was wagering.
I will raise him $50 that the study when released is shoved in a drawer and forgotten.
Why are people here so clueless.. (Score:1)
Re:Status of a subject... - small correction (Score:1)
And lo and behold - the superpartner of the photon, called the neutralino
If I remember correctly from my thesis, netralino is a mix of partners of photon, Z-bozon and up and down Higgz (being called Higgzino if Higgz portion dominates)Re:Neutralinos? (Score:2)
"Come! Dine at Neutralino's, where your fettucini is always protected by our stricly anonymous dining laws!"
-LjM
Re:Dark Matter? (Score:1)
Re:Dark Matter? (Score:2)
I think this is a perfect example of science trying to fit things into place with a theory. There's nothing wrong with that, as long as the theory doesn't account for something thats easily explainable by something else. This whole dark matter issue is explainable by unseen dust, and unseen matter. We don't need to theorize about weak particles the size of nickel that weakly flow through the Universe, because there's nothing that truely tells us this.
Now I'm not saying its not possible. I just have an overwhelming feeling that the paper will be released. Physicists everywhere will say its bullsh1t, and we'll never hear about it again... with which half of
BTW, I have the fountain of youth. Its a combination of a couple off the counter drugs. I'll be releasing it in my paper Wednesday.
Thats my case
Re:Did you even read the article? (Score:2)
I never said it wasn't possible, and I'm not accusing them of anything. What I'm saying is that I have an _extremely_ hard time believing anything _YET_. This is simply because they're showing us nothing.
PD apparently is the only one here who sees this as rhetoric. I'm yelling bullshit because we've _seen_ _nothing_. Yeah there are lots of amazing theories and ideas in the world. The rotational curve of galaxies being a result of WIMPs is one of them. I'd just say that they're due to gas and dust thats undectible because they've reached thermal equillibrium. The evidence atleast suggests that.
$50 says that the study is shoved in a drawer and forgotten.
Re:Did you even read the article? (Score:2)
The issue is that half of
Based on that, I'd say there's no basis for it. The whole theory of WIMPs in general just seems a bit far fetched to begin with. Thats basicly all I'm saying. Everyone just feels the need to jump on my back when I say that I think its bs, because right now, I've read nothing that tells me otherwise.
I'm actually very interested in the whole topic itself. I'd like to see the unified theorem come to fruition. I'm just not going to let my hope talk me into believing something that as of this moment, has no evidence.
Thats pretty much my stance.
As for the absorption lines, gas isn't the only form of matter in the Universe
Dark Matter? (Score:3)
"Though astronomers have been measuring the gravitational pull of the dark matter since the 1930's, they have never succeeded in detecting it directly."
I assume with this statement they're refering to the velocity vs distance from the center for stars in a galaxy. Its always been known that the fact that the stars in a spiral galaxy rotate with uniform motion, like a disk, simply because of the amount of dust and gas in between the stars.
If you ask me, I call this someones "what if" explaination, and attempted proof, that will quickly be disproved if it does in fact have any scientific basis. Of course, when this happens however, it won't make it to the presses
Re:Validating my previous theory about speed of li (Score:1)
Re:Oh sure, blame all the problems of the universe (Score:1)
Re:ether? (Score:1)
Re:A Research Gift (Score:1)
Re:What can you do with WIMPs? (Score:1)
Lets see: They have no electromagnetical interaction, so they pass through anything easily. They have the weak interaction, so you might be able to upset radioactive processes if you could concentrate enough stuff in one place. This has lots of uses.
African American Matter, dammit! (Score:1)
Re:Oh sure, blame all the problems of the universe (Score:1)
Headline: (Score:3)
Sorry, couldn't help myself. I like physics, too.
Regards,
Re:Status of a subject... (Score:2)
proton + antiproton -> very energetic gluons -> squark + antisquark -> neutralinos + lots of other junk.
You could detect all of the other junk and measure its energy and momentum, and you'd see that there's a giant difference between that and the initial beam energy, so the difference must be particles that escaped your detection. Similarly you could measure the "missing charge" and so on, so you get a pretty good fix on what escaped.
The only catch is that 134GeV is actually about the absolute max that LHC will be able to see. The problem is that, while the interaction energy is about 2TeV (once everything's at full spin), the particles are protons and antiprotons. At these energies, you have to think of each of these as composite objects; bound states of three quarks (antiquarks) and a lot of gluons. The actual scattering is a quark off an antiquark, so each constituent particle has only about 1/7 of the total beam energy. On top of that, because of various conservation laws neutralinos (or any other SUSY particle) have to be created in pairs, so you need a lot of energy to do this.
But finding these particles (the buzzword is 'LSP,' Lightest Supersymmetric Particle) is one of the primary missions of LHC.
Yonatan
Status of a subject... (Score:5)
The matter you can actually see through a telescope is really only luminous matter; things which are directly emitting (a great deal of) light. Namely, stars, quasars, occasionally black holes (which are black but infalling matter creates huge X-ray jets) and things like that. Anything else, by definition, is "dark matter." (So by definition, you and I are made of dark matter - this is not generally that wierd a stuff)
The reason we know dark matter is there in large quantities is by measuring the motion of stars in galaxies and so on. Basically, we understand how gravity works pretty well (at least on astrophysical scales) and so by watching the motions and orbits of luminous objects, we can work backwards and find the distribution of mass in the universe. From this we find that only about 10% of all mass is luminous - the rest is "dark matter."
Now, it turns out we can find out substantially more about dark matter from these gravity measurements. (There are a lot of different kinds of measurements which I won't go into; suffice it to say that they all more or less agree) For one thing, we can tell how it clumps up, and from that deduce some things about its internal structure. For example, dark matter made out of heavy noninteracting particles (say about the mass of an iron nucleus) will move around very differently from dark matter made out of very light fast particles, which will move differently from large lumps of matter each about the size of a star, and so on.
The basic types of dark matter are:
Hot Dark Matter: (HDM) Small light particles moving about at close to the speed of light. Measurements suggest that there isn't much of this around, not enough to make a huge difference. Neutrinos would fall into this category.
Baryonic Cold Dark Matter: (Baryonic CDM) Heavy particles in the form of ordinary nuclei and atoms. Up to and including ourselves. This category also includes "MACHOs" (An acronym whose expansion I can't remember right now), which are essentially star-sized or bigger objects which we can't see. Brown dwarfs, large gas giants, and so on. Large dust clouds also fall into this category.
Non-Baryonic CDM: CDM means that the particles in question are heavy and so move much slower than the speed of light. Non-baryonic means that they're not made up of ordinary nuclei. This category includes what are called WIMPs (Weakly Interacting Massive Particles), which are any sort of big, heavy particle that doesn't interact much with other matter in the universe. (e.g., it can't have an electric charge, since that would make its dynamics very very unlike experimental data)
The reason WIMP searches are so cool is that any particle that turns out to be a WIMP will probably be very interesting in its own right. I can't explain all of the details in something of this length, but there is a symmetry called Supersymmetry (SUSY) which is postulated to exist. There are lots of good theoretical reasons to believe in it (for the technically minded: Grand unification doesn't work entirely right without SUSY, and you can't introduce fermions into string theories without SUSY.) and by now everyone is pretty much expecting to discover it experimentally soon; in fact, a discovery that SUSY doesn't exist would be even more interesting than a discovery that it does.
The reason I bring up this whole dreary story is that SUSY predicts that for every particle of ordinary matter (electrons, protons, photons, etc.) there is another related particle, its superpartner. A direct detection of a superpartner would be both a vivid confirmation of SUSY and incredibly useful experimental data about the structure and nature of the universe. (There are armies of physicists who are ready to strip every imaginable drop of information out of data right now. People have been waiting for this for a while.)
And lo and behold - the superpartner of the photon, called the neutralino, happens to have some properties that would make it a great candidate for a WIMP. It interacts very weakly indeed; for comparison, the Coulomb force between two electrons is proportional to 1/r^2, where r is their separation. The force between two neutralinos would scale something like e^(-r/r0)/r^2, where r0 is a characteristic distance on the order of perhaps 10^-20 meters. They're also stable - due to some conservation laws (analogous to conservation of electric charge, which makes circuits work) they can't decay into anything else, so once they're created, you're pretty much stuck with them drifting through the universe. And they're heavy - experimentally, their mass should be somewhere between 80-a few hundred GeV. (For comparison, a Hydrogen atom has a mass of just over 1GeV)
Now the Rome group is claiming to have detected WIMPs of masses somewhere between 52 and 134 GeV, which are candidates to be neutralinos. This will definitely spark some excitement and a lot of discussion. What happens next is that people are going to be reading this and arguing over every detail of their data analysis and so on, and other people will try to replicate their results. If this is confirmed, it represents a big step in understanding both the large-scale nature of the universe (WIMPs, and the nature and origin of dark matter) and its very small-scale structure. (SUSY, the fundamental interactions of matter)
OTOH, one shouldn't get too excited yet -- this represents an interesting result but it still has to go through a very rigorous checking and repeating process. It has happened (quite a few) times before that interesting signals have been observed which later turn out to be something very ordinary. It'll take some time to tell about this one, but hell - if it works, it's seriously neat.
Yonatan
Re:A Research Gift (Score:1)
Re:Temperature Effects (Score:1)
to isolate their NaI and phototubes by sealing
it in a box and flushing with N^2. Later in the 'print, they mention that when they look at the temporal variance in their 'background' (defined as counts above 90 keV), it is consistent with zero.
I'd rather see the paper after the referees have hacked it up, but they seem to understand their apparatus quite well.
- B
man... (Score:1)
[ c h a d o k e r e ] [dhs.org]
Damn WIMPS (Score:1)
Re:Validating my previous theory about speed of li (Score:1)
"What can you do with" == !necessarily important (Score:1)
Answering a long-standing problem in astrophysics is not inconsequential in my opinion. Unlike you, many, including myself, do have a healthy interest in how the universe works, and when a problem such as this appears as if it may be answered (I'm skeptical, and I'll wait to read their paper and see some supporting evidence before I'm convinced), we understandably take interest.
An experimental/observational validation of supersymmetry would itself be a momentous achievement, even apart from the context of dark matter, as it would have a significant impact on how we understand the physical world at its most fundamental level.
I do hope it's a major break thorugh and produces something useful in every day life.
I'm of the opinion that a measure of our scientific inquiry and discovery should remain separated from the incessant "what good is it?" questions. It's bad enough that most such science can't get funded anymore, that the politics of acquiring research funds requires, typically, a "product" after a year or two [often at the expense of doing a quality job of understanding the science], that only "tried and true," conservative problems seem to get attention, and that much of the business of doing science has become entrenched in rehashing dogma and maintaining the status quo.
Sometimes human beings do things that aren't necessarily useful in everyday life, but yet enrich the human experience somehow. If you've ever posted to Slashdot, played a video game, read a novel, looked at a pretty painting, attended an opera, or cogitated your place in this universe, you might appreciate this point. It's somewhat unfortunate that science has been recognized by the layperson primarily for its commercial, and not its philosophical, value.
My apologies for the long-winded response to your post.
The real dark matter problem (Score:2)
-r
Is this another step in the wrong direction? (Score:1)
If we look back to all areas of science, we see a trend:
1) make a theory that fits the general case
2) expand it till it works for all cases
3) throw the thing out once someone see the light
4) have a simply theory that works.
this has happend so many times in the past and the only consistant lession is that we will repeat the trend.
One of my theorys is gravity does push. These are lots of reasons why this can't happen and there are some easy to read accounts of the reasons in Dr Fineman's books but all those reasons are based on a gravity particle concept that we know isn't right. Calculus was invented because Newton was tring to prove the math behind gravity. It turns out that he couldn't integrate gravity pushing but he could do it if he decided gravity pulled and we have been using that theory since. So how does one prove if gravity pushes or pulls?
implications of weakly interacting matter (Score:1)
The implications of this discovery, if proven correct, might extend farther than appears at first glance. When discoveries like this are made things that seemed absurd yesterday suddenly become plausible.
Particles 50 times heavier than a proton which almost always pass through other matter without a trace - not only can we not observe these particles with our eyes, but we up until now haven't been able to observe them with our best scientific instruments. What if these particles don't just occur randomly? What if they have structure, either naturally occuring and evolved, or by deliberate design?
It would be interesting indeed if we were to discover large scale objects such a rocks, planets, or even life forms made of this stuff.
Validating my previous theory about speed of light (Score:1)
Pink WIMPs (Score:1)
maybe (Score:1)
I've read it... it plotted the next several Billion years of mankinds exsistance, I think it was called "Ring" because of the 'other' advanced baryonic race that developed the great ring as a means of slowing the advance of the dark matter birds.
MRo
Re:dark matter birds? (Score:1)
Re:Paraphrasing... (Score:1)
Re:Paraphrasing... (Score:1)
Re:NYT login (Score:3)
htt p://partners.nytimes.com/library/national/science
No annoying registration...who would've thought it would be that easy?
numb
Re:What can you do with WIMPs? (Score:1)
I'm sure the discovery of what constitutes (possibly) up to 90% of the known universe is totally inconsequential in itself, right?
OK, though I'm no expert in quantum mechanics, I'm sure there could be a way to harness these things for power (unless the "Weakly Interacting" part precludes it), though maybe not with current technology. Could a disturbance in this matter be made in to a sensor of some sort to detect movement or disturbances in magnetic fields? Who knows?
Re:Oh sure, blame all the problems of the universe (Score:1)
Ill give you an counterexample: In statistical physics there is a fundamentally broken concept called "white noise". White noise causes all kinds of problems, but is still sometimes easier to handle than realistic noise.
An imploding star that fails to become a black hole might become a white dwarf.
Even worse, Quantum Chromodynamics assign the property "blue" to particles without considering the consequences that this might have on people with a blue skin.
Re:Dark matter? (Score:1)
There are three different settings the Universe could be in.
1. closed universe
there is enough gravity so that eventually the universe will recollapse. The universe would expand in ball form and then stop and shink (thus making a limit to how far you can go: closed)
2. open universe
there is not enough matter, universe expands forever. In this form the shape of the universe would be all wacky and weird, like a ball that blew up, but still in one piece.
3. the middle path
there is just enough matter for there to be an equalimbrium, this is the smallest amount so that the universe will always expand. The form of this universe would be flat.
So far, the universe have followed the middle path, but the observable universe only has about 10% of the needed matter for this to be the case.
Login: (Score:1)
password: dotslash
Re:Is this another step in the wrong direction? (Score:1)
I don't mean to pick nits here... (well, maybe I do) but time actually speeds up as height increases. See, gravity slows time; the higher you go, the less gravity, and voila, time speeds up.
Re:Neutralinos? (Score:1)
Re:Status of a subject... (Score:1)
Re:...'n' MACHOs 'n' the Cosmological Constant (Score:1)
Komi
Only 20%?!?! (Score:1)
Re:Oh sure, blame all the problems of the universe (Score:1)
Actually, we already have that - quarks come in red, green, and blue!
--
Two reasons why... (Score:1)
Firstly, from calculations of a galaxy's structure. Even using simple methods like the Virial Theorem (2T=V where T is kinetic energy and V is gravitational potential energy IIRC) it can be shown that given the mass of stars in a galaxy, the diameter of the galaxy and the speed of rotation the gravitational potential of the galaxy is only about 10% of the value required to prevent the stars being flung out by centrifugal force. Seeing as galaxies are stable physicists must assume that the other 90% of this mass is "dark matter" which we cannot detect using current means. More detailed calculations show this is most likely to exist as a huge disc in which the visible galaxy is embedded.
The other reason has to do with the cosmological constant from Einstein's General Relativity. This value determines the "flatness" of empty space-time, and experimentally this as been measured as being less than 10^-120 i.e. almost certainly zero. However if the Universe is flat then the density of matter must be equal to some critical value. Current calculations of the matter density of the Universe vary from between 1% and 10% of this critcal value, and so again physicists have to assume the presence of dark matter which the cannot observe to account for this discrepancy. Given this critical density the Universe will eventually expand at a constant rate and there will be no Big Crunch.
Of course, the other explanation is that all these theories could be totally wrong, but this would require changing a lot of the physical theories of this century so it isn't too likely IMHO.
Stephan Baxter's Xeelee sequence (Score:1)
A truly excellent series of books, which are in order:
They are very much worth reading and have probably one of the grandest scopes of any hard science fiction I've ever read, and some amazing ideas about the history of the Universe and physics.
Re:JudgePagLIVR (Score:1)
It's nitpicking, but it's important to realize this. Because someday somebody's going to find out what the REAL contents of the universe are. and maybe modern theory will be just a little bit off, but close. Or maybe we'll find out that the vast majority of the universe is made out of licorice flavored jelly beans.
As silly as that sounds, the "dark matter" theory and the "licorice" theory stand on equal ground scientifically until the actual proof of the matter comes in.
Certainly, you and I personally have no direct evidence that the center of the sun is not made of jelly beans. However, we also have no direct evidence that we are not the proverbial brains in vats. I suppose you can set your standard of evidence so high that "the center of the sun in not made of jelly beans" remains an unproven theory. Even if you do so, it is rediculous to suggest that the jelly bean theory and the dark matter theory are on equal ground, just because both are unproven. The difference is that the dark matter theory has a body of evidence supporting, while the jelly bean theory does not. While the evidence for dark matter may not meet the standard of proof, that does not relegate it to the same level as all unproven theories.
Re:Dark matter? (Score:1)
I think dark matter works completely differently from 'normal' matter, part of which is not giving off photons. Making it very hard to detect, I guess.
-Ravagin
"Ladies and gentlemen, this is NPR! And that means....it's time for a drum solo!"
Re:What can you do with WIMPs? (Score:1)
It's science! It's fascinating! Why do we need a good reason to care, other than that it's interesting? And if you're not interested in it, fine, but why do you feel the need to spread your disinterest with a whining post?
God is a WIMP (Score:1)
1. Assume that god is omnipotent and everywhere simultaneously
2. Assume that omnipotence correlates with energy
3. E=mc^2
4. God has direct interaction with 1/1^7 individuls per year.
5. God is an individual (can be considered as a quanta)
6. God does not emit electromagnetic radiation
Therefore god is WIMP-Weakly Interacting Massive Particle.
Temperature Effects (Score:2)
I'd also like to see their report, but their server did not respond. The average NaI detectors is the equivalent of a 486 in the computer world. I wonder if that's what their web server is. Must be slashdoted.
Good luck to them.
Re:Is this another step in the wrong direction? (Score:1)
-=-=-=-=-=-=-
This signature contains text from the worlds funniest signature.
NYT login (Score:1)
Re:A Research Gift (Score:1)
You should write him about the banner idea, tho. ;)
A Research Gift (Score:2)
Maybe I can get some money to see if any light really does come out of black holes. $1,000,000 and a few years later i'll be able to publish, add a banner ad to my homepage, and laugh as it gets slashdotted, carrying me to financial indepedence.
I {heart} slashdot (Score:1)
Viel laerm um nichts.
At least it keeps these people off the streets.
Re:Did you even read the article? (Score:1)
Despite regular matter being a more straight-forward explanation of dark matter than WIMPS, there are a lot of problems with it. Gas can be ruled out because it's just too damned hard to hide. It both absorbs and emits enough radiation that it would be easily detected. Large quantities of dust are also difficult to hide. Neutron stars and black holes emit huge amounts of radiation (actually the matter around black holes), so we would notice those, also. That pretty much leaves large chunks of rock as the explanation of 'normal' dark matter. There are two huge problems with this. First, current cosmological theory predicts that at least 75% of baryonic matter, the stuff that atoms are made of, should be in the form of hydrogen. That has been confirmed numerous times by direct observation of the universe around us. And hydrogen gas has been ruled out as not being dark at all (as I said above). Second, there is absolutely no reason to believe that there are enough large chunks of rock out there to make up 90% of the mass of the universe. What we have observed is that rocky material makes up a very small percentage of the total mass. What you say about physics suggesting that dark matter is just plain old atoms is simply false.
WIMPs have the problem of very little expermental evidence supporting the theory. But there is some indirect evidence that gives the theory weight. We have observed weakly interacting particles that also have mass. The difficult part is determining how many of these particles exist and how massive they really are. Your hypotheses, on the other hand, are lacking in both theory and evidence.
The NYT is almost certain to get the story wrong, and some /.ers will jump on the band wagon of the 'new' theory (even though it isn't really new), but that doesn't warrant an immediate dismissal of WIMPs and modern astrophysics in general.
Re:Dark Matter? (Score:2)
The paper is about the detection of the particles. These types of particles are predicted by supersymmetry theory (as noted in the NYT) and this will be the first experimental confirmation of their existance if the results are reproducable. Detecting this type of particle is no easy matter, either. But you seem to imply that if they really did exist, somebody surely would have detected them by now. The fact that they only interact weakly (via the weak nuclear force) and gravitationaly with other particles makes them extremely difficult to detect. The only way to directly detect weak particles is to observe the aftermath of a direct colision with an atomic nucleus, which will produce a flash of light. This is an extremely rare event -- the average neutrino (another weak particle) could travel through a light year of solid lead before coliding with the nucleus of a lead atom. The existance of nuetrinos, by the way, has been well established for decades. They are easier to detect (indirectly) because they are byproducts of many nuclear reactions.
Blaming it on massive particles that weakly interact with regular mass is as valid as saying little elves are moving things around.
In the case of dark matter, the WIMPS are interacting with regular matter via gravity -- not just the weak force. The weak force has to be used to detect them experimentally because there is no way to differentiate the gravity from a weak particle from the gravity of a normal particle. We can, however, distinguish between particles that interact only weakly and those that interact weakly and electromagnetically. That's what this experiment does. The difference between WIMPs and elves is that WIMPs are predicted by theory, and elves are not. There is also evidence beyond this particular experiment that gives credence the the theories involved, although this is the first time that a WIMP may have been detected. If you can come up with a valid theory of elves and provide solid experimental evidence supporting it, then we can throw that in the dark matter pot also.
Re:Dark Matter? (Score:2)
WIMPs, if they exist, have more of an effect on the surrounding environment than neutrinos because they have a much greater mass and can exert a gravitational force on surrounding matter as well as the weak force. The fact that neutrinos have little, if any, mass rules them out as dark matter -- they primarily interact weakly. This isn't far fetched at all. These kinds of particles probably do exist -- the only question is whether or not there are enough of them to account for dark matter.
I think this is a perfect example of science trying to fit things into place with a theory. There's nothing wrong with that, as long as the theory doesn't account for something thats easily explainable by something else. This whole dark matter issue is explainable by unseen dust, and unseen matter.
You're getting things backwards here. If WIMPs were invented solely as an explanation of dark matter, then they would indeed be suspicious. WIMPs are predicted by supersymetry theory, which is an extension of quantum mechanics. It was only after this that some physicists realized that they could be the source of dark matter if they exist in great enough quantities. The theoretical discovery of WIMPs was made independently of any study of dark matter. This isn't some new theory that has popped up out of no where as a convienient explanation of dark matter.
You are correct in saying that the whole dark matter problem is explainable by the presence of unseen matter. That's what WIMPs are. They are real particles that don't interact electromagnetically, so we don't notice their presence in normal life. Dust and gas were ruled out as sources for dark matter long ago. The density of the clouds would be high enough that the gas and dust would start to glow and we would be able to detect that light. Red dwarfs were also recently ruled out as the explanation of dark matter.
This particular physicist believes that WIMPs are one of the best theories of dark matter to come along so far. I am not convinced that this experiment has actually detected WIMPs, but that is an experimental problem, not a problem with the theory. BTW - this theory is not nearly as bizarre as the theory that tachyons (faster than light particles) are the source of dark matter.
Re:Dark matter? (Score:3)
The other thing that tipped off the astrophysicists about how much dark matter is out there is the dynamics of spiral galaxies. If normal orbital dynamics were at work, then based on the distributions of stars, the stars in the centers of galaxies should have a much shorter orbital period than the stars on the rim. But what is observed is something much closer to the rotation of a semi-rigid disk -- the stars on the rim don't take much longer to go full circle than the stars very near the center. This suggests that the distribution of mass in spiral galaxies does not correlate with the distribution of stars.
Is it possible that this matter is maybe some form of elementary particle that doesn't give off other particles (ie, the smallest particle which would not give off photons) and that's why we can't see it? Just my own questions on the subject. Wish I knew more about it.
The WIMPs are a type of elementary particle. Unlike protons quarks (making up protons and neutrons) and electrons which respond to gravity, electromagnetism, and nuclear forces (strong and weak), WIMPs only respond to gravity and the weak nuclear force. The absence of electromagnetism is why they don't ever give off any light.
dark matter birds? (Score:1)
if i remember correctly, it had "birds" made of dark matter and they were trying to put out the sun by flying into the core, then carrying matter to the outer rim... which had the effect of reducing the sun's temp... it seems that light matter (??) effected them in some unpleasant manner and they wished to put an end to it...
no .sig please
Re:Status of a subject... (Score:2)
Re:Validating my previous theory about speed of li (Score:1)
WIMP weight (Score:1)
Re:Oh sure, blame all the problems of the universe (Score:1)
Re:white holes? (Score:1)
Re:Dark Matter (Score:1)
There are other things that need dark matter to explain, too, I just can't remember what they are.
Re:Particle accelerators... (Score:1)
actually, more like 10% seen (Score:1)
Dark Matter (Score:1)
Slightly off topic (Score:1)
Re:Validating my previous theory about speed of li (Score:1)
Of course you're right, I should have said "opposite charge", not "negative charge". Otherwise, electrons would be antimatter! However, I don't see how you could have neutral-charged antimatter. Negative zero is still zero, after all. Is it possible to have an antiphoton?
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Re:Validating my previous theory about speed of li (Score:2)
Not valid. Scientists have found antimatter, played with it, and still needed to look for dark matter.
Bzzt. Wrong. Antimatter has negative charge, not negative mass. Matter with negative mass is something else entirely, and is responsible for antigravity.
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It's a lot less than that... (Score:2)
Because there's also all that you taste, feel, love, hate, distrust, save, give, deal, buy, beg or borrow or steal, create, destroy, do, say and eat; everyone you meet, all that you slight, and everyone you fight, all that is now, all that is gone and also all that's to come.
And most impotantly, it must be remembered that this only the sum of everything under the Sun.
The Sun, you see, is eclipsed by the Moon, which as everyone knows is all dark, so all that you touch and see is more like only %0.083333333333333333 of the total mass of the Universe. Maybe less.
Acronyms (Score:1)
Weakly Interacting Massive Particles
I love how they come up with these acronyms.
Re:...'n' MACHOs 'n' the Cosmological Constant (Score:1)
Anyway, the best-guess on cosmic topology varies on whom you talk to. Judging by the redshift/supernova frequency data on distant galaxies, the universe looks open (hyperbolic). But if you look at the mean anisotropy diameter of the cosmic microwave background, it looks marginally open (flat geometry). And if you throw the CC in, you can conceivably have a universe of any mass you like still turn out open.
Re:Dark Matter? (Score:3)
The major candidates for this matter thus far have been MACHOS (massive compact halo objects - i.e. brown dwarfs/neutron stars/black holes), neutral gas (neutral hydrogen, in particular, is rather difficult to detect), and WIMPS. In the last few years, more evidence has been accumulating for all three of these classes. Personally, I expect that the missing mass will turn out to be a mixture of gas and WIMPS - if the halo contained enough compact objects to be significant, you'd think we'd see more stars there too.
From the source... (Score:3)
Re:Useful? (Score:1)
Neutralinos? (Score:2)
JudgePagLIVR (Score:1)
The most obvious problem I see is that "all the matter you touch and see" isn't 20% of the universe.
.00000000000000001% of the universe would be more like it.
The problem is that not only is dark matter theoretical - most non-dark (enlightened?) matter is also theoretical. Pluto, the center of the sun, heck even the center of the earth - all these are recognized only in theory.
It's nitpicking, but it's important to realize this. Because someday somebody's going to find out what the REAL contents of the universe are. and maybe modern theory will be just a little bit off, but close. Or maybe we'll find out that the vast majority of the universe is made out of licorice flavored jelly beans.As silly as that sounds, the "dark matter" theory and the "licorice" theory stand on equal ground scientifically until the actual proof of the matter comes in.
WIMP's Explain Stale Bread in Italy (Score:1)
It is not clear if the people in Italy would age faster also. But there, especially in Rome, more people wear black, perhaps to protect themselves instinctively from the WIMP swarms. Obviously more research is needed now the meutralino break-through has been made.
Would Vitamin E be effective against the focused neutralinos? If only Linus Pauling were still alive to conduct this research...
Re:Watch it, dude! (Score:1)
Dark matter? (Score:1)
Is it possible that this matter is maybe some form of elementary particle that doesn't give off other particles (ie, the smallest particle which would not give off photons) and that's why we can't see it? Just my own questions on the subject. Wish I knew more about it.
Null_Void
WIMPs (Score:2)