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Underground Lab To Probe Ratio of Matter To Antimatter 82

Posted by Soulskill
from the scotty-unavailable-for-consult dept.
Wired reports on the Enriched Xenon Observatory 200, a particle detector scientists hope will answer the question of why there is significantly more matter than antimatter in the universe. Quoting: "The new detector will try to fill in the picture, determining basic features of [neutrinos], like their mass and whether or not they, unlike almost all other particles, are their own antiparticles. That quirk is why some scientists believe neutrinos could be the mechanism for the creation of our matter-filled universe. Almost all other particles have an antiparticle twin that, if it comes into contact with the particle, immediately annihilates it. But if neutrinos are their own antiparticles they could conceivably be knocked onto matter's 'team,' thereby causing the cascading win for matter over antimatter that we know occurred. As the Indian theoretical physicist G. Rajasekaran put it in a speech [PDF] earlier this year, neutrinos that are their own antiparticles would explain 'how, after [the] annihilation of most of the particles with antiparticles, a finite but small residue of particles was left to make up the present Universe.'"
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Underground Lab To Probe Ratio of Matter To Antimatter

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  • I thought it wasn't possible to tell antimatter from matter from afar?
    --
      IP Finding [ipfinding.com]

    • by someone1234 (830754) on Saturday October 25, 2008 @05:27AM (#25508169)

      Even in your closet!
      So you don't have to look afar.

      • by BiggerIsBetter (682164) on Saturday October 25, 2008 @06:39AM (#25508423)

        Even in your closet!

        Neutrinos are gay?

        • Re: (Score:3, Insightful)

          by TheLink (130905)
          Researchers are trying to figure out whether neutrinos are straight or bi, they think this might help explain why the rest of the universe is mostly straight (allegedly).

          Except most of them are not even sure what >90% of the universe is made of, so what makes them so sure that the rest of the universe is mostly straight?
        • by rrohbeck (944847)

          Gays are everywhere! Vote yes on 8! We have to stem the tide of gay neutrinos! Think of the children! They'll all be made gay if we let the neutrinos take over the school system!

    • Re:How can you tell? (Score:5, Interesting)

      by CRCulver (715279) <crculver@christopherculver.com> on Saturday October 25, 2008 @07:15AM (#25508567) Homepage

      I thought it wasn't possible to tell antimatter from matter from afar?

      That's the premise in one of Larry Niven's old Beowulf Shaeffer stories (collected in Crashlander [amazon.com] ). Shaeffer and a Steve Fosset-like millionaire come upon an isolated planet, only to discover to their dismay that it is made out of antimatter. Unfortunately, the relatively believable science ends there, because Niven's way of having them colonize it relies on a species of unobtainium

      • by Fëanáro (130986)

        -Spoiler-

        I remember the story differently:

        They cannot figure out why the planet and sun are such an anomaly
        (high velocity indicating origin outside of the milky way, no sign of interstellar debris, unusual high activity of the sun)

        They argue about landing on the planet, even thought their ships hull gets damaged by an unknown force

        In the end they decide not to risk it, and go back to civilisation, and only then are told that their hull must have been damaged by antimatter, that therefore the whole system wa

        • by CRCulver (715279)
          I think Niven's telling of a way to colonize it was in one of his later collections, N-Space or Playgrounds of the Mind. It's been a few years, though.
        • "Crashlander" follows the story of Beowulf Shaeffer for a few years (it's actually a set of different short stories held together by a "glue" story). It is said in the glue story that matters got complicated, the UN got involved and eventually nobody went back due to bureaucratic reasons.

          • I thought they tossed a UN flag down to watch the fireworks though.
          • by Agripa (139780)

            In the last two Ringworld books, the design of the UN ships reveals that they are powered by antimatter and as I recall, The Hindmost tells his allies that the UN has possession of an antimatter system which presumably is the same one Shaeffer and Elephant visited. The Kzinti's source of antimatter remains a mystery. The most recent Man-Kzin Wars book might discuss it.

            Shaeffer must have been good about keeping secrets since his son Louis apparently does not know about any of his father's exploits. Oddly

        • by RockDoctor (15477)

          Spoiler for yourself CRCulver (715279) and Ernesto Alvarez (750678) : there is significant new matter on this in the recent "Juggler of Worlds" by LarryN and ANOther.
          .
          .
          .
          Spoiler space
          .
          .
          .
          There isn't any plan to colonize the antimatter planet as such, but there is a plan to send people and/ or equipment to mine the antimatter planet. The military implications of this are not lost on the pacified species (Kzinti) of Known Space, nor on the several remaining dangerous, if not aggressive, species (not named - RTF

      • by sjames (1099)

        In my recollection, the idea that it might be colonized using a stasis field was one reason Niven opened Known Space to other writers and took a bit of a hiatus himself (and then went back and covered the earlier history a bit). He felt that too many problems were too easily solvable at that point.

    • Re:How can you tell? (Score:4, Informative)

      by hpa (7948) on Saturday October 25, 2008 @12:15PM (#25509895) Homepage

      I thought it wasn't possible to tell antimatter from matter from afar?

      In a perfect vacuum, it isn't. However, even the intergalactic medium isn't a perfect vacuum, and somewhere there would have to be a border between a matter region and an antimatter region. Such a region would give off a very specific gamma ray spectrum, with a peak at 511 keV due to positron-antipositron annihilation and several peaks in the 70-400 MeV range due to proton-antiproton annihilation; the rate of interaction would be low, but the surface area of the frontier so large that we should be able to observe it from Earth. If it is a more localized phenomenon (like Niven's star system), then it would be travelling through the interstellar medium, inside a galaxy, which is far denser.

      • due to positron-antipositron annihilation

        Am I missing something? Isn't a "antipositron" an electron? Generally the anti- prefix goes with the antimatter, not the matter.

        • by hpa (7948)

          I meant electron-positron annihilation, of course. My brain had "proton-antiproton" in its head when I wrote that, and so it came out weird.

          • Actually the 'positron-antipositron' bit makes more sense from my POV. If anti- means antimatter, why not make it consistent?
            • by mindstrm (20013)

              If anti means antimatter, you would express it as
              electron / antielectron.

              Antielectron == positron

      • by pugugly (152978)

        Pardon my naivete, but given the theories of hyperexpansion in the early universe, isn't it just as likely that the preponderance of matter was strictly local, the same way the differences in the background radiation were exceedingly small, but sufficient differentiate spacial regions?

        Neat as any gamma ray spectra at X keV would be, I would presume that any ongoing border between a matter/antimatter region would create sufficient 'pressure' for the regions to not mix, the same way dropping sodium on water

  • How so? (Score:4, Interesting)

    by KasperMeerts (1305097) on Saturday October 25, 2008 @05:47AM (#25508247)
    Who says there is more matter than antimatter in the universe? Has anyone ever gone to the Andromeda galaxy? So how do we now it consists of normal matter? Doesn't matter react the same as antimatter in every possible way?
    • Re:How so? (Score:5, Informative)

      by Anonymous Coward on Saturday October 25, 2008 @05:59AM (#25508287)

      If there had been an exactly equal amount of matter and antimatter since the birth of the universe, it would have long ago annihilated into photons. Since this has manifestly not occurred, one is in excess of the other. Which one you label as "matter" and which one "antimatter" is purely down to personal preference.

      Some differences can be observed in the behaviour of matter and antimatter; for example, in a magnetic field, electrons will curve in one direction and positrons in another. Another example is the asymmetries observed in the oscillations of mesons (the classic example being the K0) which reveal a clear, fundamental difference between matter and antimatter.

      • Re:How so? (Score:5, Informative)

        by Anonymous Coward on Saturday October 25, 2008 @06:19AM (#25508365)

        Even an easier explanation. The annihilation of antimatter with matter gives off very distinct spectral patterns. We know what these are, and we have calculated them for any observable red/blue-shift range. We've yet to observe any great quantity, or even a 'halo' around any other galaxies. In an equally distributed universe, you would see such things, as high-velocity matter from one universe collided with another, and give off pretty lights. We don't see such, hence, the universe is mostly matter.

      • by da5idnetlimit.com (410908) on Saturday October 25, 2008 @10:08AM (#25509273) Journal

        Dear citizens and members of the galactic Economic Council

        The rumors about a shortage of antimatter to fuel or spacefleets and habitats is unfounded.

        Everyday our scientists everywhere in this universe are finding new ressources, new anti-black stars to drill for our energy.

        We used antimatter for thousands of millenia now, will continue for a lot more. I am happy to announce you the we finally opened for production that galaxy on the outer left reach of the milky way. There most advanced civilisation is a monkey like tribe that have barely learned to cover themselves and there was so to speak no Spaceflight activities to be observed.

        One or two derelicts spacecrafts have been observed, but they use a primitive explosion system, so we are sure those Terrans will not mind if we pump their galaxy dry of the stuff.

        The message from SF DR SD 3, President of ExNegMat power industries.

    • Re:How so? (Score:5, Informative)

      by daniel_newby (1335811) on Saturday October 25, 2008 @06:13AM (#25508339)

      Who says there is more matter than antimatter in the universe? Has anyone ever gone to the Andromeda galaxy? So how do we now it consists of normal matter?

      Gas is observed between the galaxies, but not the hard radiation that would be produced when it reached a galaxy and annihilated.

    • by walter_f (889353)

      Additionally, if some far away galaxy consisted completely of antimatter, to the inhabitants of this galaxy we would clearly be the "antimatter people".

      Like in telecommunications with another civilization somewhere else in the universe it would not be a trivial task to agree upon the meaning of "left" vs. "right" (no political pun intended here).

      --
      "My parents have been on vacation to a planet where the dominant species has no lateral symmetry - and all they brought me is this lousy F-shirt!"

  • by MichaelBuckley (1258630) on Saturday October 25, 2008 @06:02AM (#25508295)
    If these particle detector scientists watched TNG, they'd know that there's only one ratio of matter to antimatter.
    • Re: (Score:2, Funny)

      by Trip6 (1184883)
      If they're not careful they'll lose anti-matter containment and open up a rift in the space-time continuum.
      • by Ihmhi (1206036)

        Has a breach in Matter/Anti-Matter containment ever opened up a time rift? Not AFAIK...

      • I think Star trek has enough problems with space, time and continuity without the need for anti-matter.

  • by kanweg (771128) on Saturday October 25, 2008 @06:15AM (#25508347)

    Does antimatter attract matter or repulse it (could a double star, one of antimatter and one of matter, i.e. where the stars revolve around each other exist?).

    Would it be a prerequisite that a big bang produces as much matter as antimatter?

    Bert

    • by Anonymous Coward on Saturday October 25, 2008 @06:43AM (#25508441)

      Does antimatter attract matter or repulse it

      *Charged* antimatter will attract its matter counterpart electrostatically via the Coulomb force. For example, an electron will attract a positron. This does not occur for neutral particles.

      The gravitational attraction between bodies must also be considered: it is negligible between individual particles, but comes into effect for macroscopic objects. The gravitational interaction is determined by the amount of mass present, and is always attractive, regardless of whether it is between matter or antimatter.

      (could a double star, one of antimatter and one of matter, i.e. where the stars revolve around each other exist?).

      A star will be (on average) neutrally charged, otherwise Coulomb repulsion between like charges will break it apart. Therefore it is fair to say that both the matter and antimatter star will be electrically neutral or at least not significantly charged.

      Even if there were two charged objects, the Coulomb force, like the gravitational force, follows the inverse square law, so extra electrostatic attraction will be equivalent to more mass.

      In either case, a stable orbit could form.

      Would it be a prerequisite that a big bang produces as much matter as antimatter

      I'm moving out of my depth here, but the answer is probably no. Even if it did, future interactions between particles may cause an imbalance (as is thought to have occurred in our universe). A prerequisite for what, anyway?

      • by shma (863063) on Saturday October 25, 2008 @08:29AM (#25508831)

        Would it be a prerequisite that a big bang produces as much matter as antimatter?

        I'm moving out of my depth here, but the answer is probably no. Even if it did, future interactions between particles may cause an imbalance (as is thought to have occurred in our universe). A prerequisite for what, anyway?

        I'm afraid the answer is actually yes, at least if you replace 'a prerequisite' by 'excepted from the laws of physics'. Since there is nothing in the laws of physics to make us believe that matter is 'preferred' over anti-matter, we naturally assume that the amounts of both in the early universe are the same. The problem with this most natural assumption is that, if there was the same amount of matter and anti-matter in the universe, and they stayed in thermal equilibrium as the universe cooled (which is true for most of its history), they would almost completely annihilate and there would be too little matter left over today to make up what we presently see. So we need an event that favours matter over anti-matter to produce the required leftover matter we see. This is called the baryogenesis problem [wikipedia.org]. Of course, you CAN just demand that the required extra matter be put in as an initial condition, but most physicists shun that approach, especially since the matter excess is one part in 10 billion, an unnaturally small number which would have to be put in by hand. We prefer to find a way to generate that asymmetry dynamically.

      • The gravitational attraction between bodies must also be considered: it is negligible between individual particles, but comes into effect for macroscopic objects. The gravitational interaction is determined by the amount of mass present, and is always attractive, regardless of whether it is between matter or antimatter.

        This is an unproven assertion. Noone ever built a large enough lump of antimatter to verify that its gravitational force is indeed attractive. It is true that within the current physical theories gravity is always attractive (leaving aside the cosmological terms), yet, unless this is verified by experiment it is but a very convincing assumption.

    • Basic answer (Score:4, Informative)

      by pjt33 (739471) on Saturday October 25, 2008 @06:50AM (#25508479)

      Does antimatter attract matter or repulse it

      IANA particle physicist or cosmologist, but I can answer this one: it depends on which particles. For example, a position (anti-electron) has opposite charge to an electron and will thus attract electrons and repulse protons.

  • To pick a nit (Score:2, Informative)

    by yttrstein (891553)
    That may not need to be picked, but as I understood it, a neutrino isn't actually it's own anti-particle, strictly, it's that a neutrino doesn't actually have a known strictly defined antiparticle equivalent. I understand it *looks* like I'm saying the same thing, but I do see a difference, however subtle.

    It's been theorized, I think, that the former is true, that it really is it's own antiparticle, based on hypothesized neutrinoless double-beta decay--which, if true, insinuates the former. But this is cl
    • Re:To pick a nit (Score:4, Informative)

      by j-beda (85386) on Saturday October 25, 2008 @08:46AM (#25508897) Homepage
      At the very least, you have forgotten the third family, the Tau and Tau-neutrino.

      See the graphic at http://en.wikipedia.org/wiki/Elementary_particle [wikipedia.org] and the article at http://en.wikipedia.org/wiki/Antiparticle [wikipedia.org] is also of interest.

      Elementary particles with no charge cannot have an anti-particle, since the definition of anti-particle has to do with having the opposite charge, as I understand things.

      • Re: (Score:3, Informative)

        by Anonymous Coward

        Actually, in the standard model, both neutrinos and antineutrinos exist and are distinct. The key point is that it is the weak, not electromagnetic, force that is important.

        The weak interaction 'connects' leptons and neutrinos. For example, an electron can turn into an electron neutrino by emitting a virtual W- boson. Conversely, a positron turns into an anti-electron neutrino by emitting a virtual W+.

        Just like electrons have non-zero electromagnetic charge, neutrinos and leptons have non-zero weak charge,

    • Re:To pick a nit (Score:5, Interesting)

      by The_Wilschon (782534) on Saturday October 25, 2008 @09:44AM (#25509143) Homepage
      IIRC, standard model neutrinos are Dirac particles, which have well defined antiparticles. However, the hypothesis being tested is whether or not neutrinos are actually Majorana particles, which are invariant under charge conjugation (that is, they are precisely the same particle as their antiparticle.). It all comes down to representation theory and the Lorentz group (and friends). If we claim that charge conjugation is an interesting transformation to examine, then we must clearly describe exactly how each of our fields (particles) changes when we apply that transformation. Dirac and Majorana particles transform two different ways, and we don't know that our conjecture that all the fermions are Dirac particles is actually correct.
    • by jpflip (670957) on Saturday October 25, 2008 @11:52AM (#25509785)

      The Standard Model assumes that all three neutrino species (electron, muon, and tau) are massless, and is essentially agnostic about whether neutrinos are their own antiparticles. If a neutrino is (is not) its own antiparticle, we call it a Majorana (Dirac) particle. Most any reaction which could tell the difference between Majorana and Dirac neutrinos can't occur in a Standard Model with massless neutrinos, so the difference is subtly and has no real experimental consequence.

      We know the Standard Model is wrong, however. From neutrino oscillations, we know that neutrinos have tiny masses. This suddenly means that there ARE experimental consequences: neutrino-less double beta decay is possible for Majorana neutrinos but not Dirac neutrinos, for example. This is what EXO and many other experiments (GERDA, MAJORANA, CUORE, ...) are looking for. Existing results aren't quite sensitive enough to tell the difference, but new ones may be.

      Just because something is not part of the Standard Model doesn't mean that it's unpopular - we need to change the Standard Model somehow, after all, since it's wrong about neutrino masses! My impression (as a particle physicist, but not in this sub-field) is that most particle theorists actually expect neutrinos to be Majorana particles. There are very interesting theories based upon a scheme called the "see-saw mechanism" which can simultaneously explain why neutrinos have such tiny masses and why the universe has so much more matter and antimatter. If neutrinos are just boring old Dirac particles, it will be back to the drawing board!

    • Re: (Score:3, Interesting)

      by rasputin465 (1032646)

      a neutrino isn't actually it's own anti-particle, strictly, it's that a neutrino doesn't actually have a known strictly defined antiparticle equivalent.

      IAAPP. Neutrinos have very well-defined antiparticles, and we observe them all the time in nature. We can verify that they and neutrinos have quantum numbers that are opposite to one another. Normally, for charged particles, the antiparticles have the opposite charge and so there is no question that these are distinct. But for neutral particles, really the only non-zero quantum number available is the handedness (this is related to helicity, which describes if their spin is left-handed or right-handed w

      • by yttrstein (891553)
        Haha, this is working the nomenclature! Well, I'm glad it doesn't just happen in chemistry. Who was it who said "Science is the study of naming things incorrectly"
      • by Kagura (843695)
        Why does the existence of neutrino oscillations mean that neutrinos must have mass? IANAPP, so I don't know how being a massive particle makes it able to oscillate between other kinds of neutrinos.
        • Re: (Score:1, Interesting)

          by Anonymous Coward

          Why does the existence of neutrino oscillations mean that neutrinos must have mass?

          Over simplifying (IANAPP): to oscillate, a thing much change. To change, a thing must experience time. Things traveling at the speed of light cannot experience time (a consequence of special relativity). A massless neutrino would travel at the speed of light.

          Since neutrinos oscillate, they experience time, which means they cannot travel at the speed of light, which means they cannot be massless, which means they must have mas

          • by Kagura (843695)
            I was about to call you a loony, but that seems like a realistic explanation. Thanks for the reply, can anybody confirm this?
  • Why does it matter if there is more matter than anti-matter? What is the matter with these people?
  • It sounded like there was going to be some government investigation into missing anti-matter, as if someone embezzled it.

    I guess I've got Quark on the brain from watching too much DSP DVDs.
  • So it's an "underground lab" now, is it. I've better not catch you geeks smoking in the basement.
  • Neutrons have no electrical charge, so what happens when one meets it's opposite? Opposite what?
  • Aren't they supposed to make Meth or something? Why are they switching to Neutrinos? Do they give you an even better buzz? Has anybody tried Neutrinos? How was it?

    • Neutrinos are lame - almost no effect at all! You can barely even tell they're interacting with you at all. I prefer to stick with proton-centric multicyclic dipolar magnetoresitant plasmoidonigistics. They don't get you high, but by the time you've finished pronouncing them, the whip-its kick in and you're too stoned to finish talking :)

  • If E=Mc^2, then wouldn't -M*c^2=-E?.

    So in any localized area where there was more anti-matter, the negative energy produced from anti-matter conversions would annihilate any positive energy around, but if there is no energy around, the anti-energy wouldn't be able to exist in our universe. Only as positive energy could it remain in existence -- but positive energy can only inter-exchange with matter -- not anti-matter. Thus after all the matter and antimatter combined, some of the anti-energy would have d

    • If this is a joke, forgive me for letting it WHOOSH over my head but... you really need to re-read the memo on matter/antimatter... you did get that memo, didn't you?

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