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Science

Dramatic Difference In Matter Vs. Antimatter 45

Posted by michael from the things-that-go-bang dept.
jma34 writes "The Stanford Linear Accelerator Center (SLAC) recently put up a press release announcing a 13% asymmetry between the interactions of matter and anti-matter. In most interactions matter and antimatter are mostly interchangeable, however our universe is matter dominated. This research helps to answer the question of where did all the antimatter go. PRL article here."
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Dramatic Difference In Matter Vs. Antimatter

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  • Problem Solved (Score:4, Funny)

    by xoboots ( 683791 ) on Friday August 06, 2004 @06:05PM (#9903945) Journal
    So that's why two wrongs don't make a right!

  • why not? (Score:2, Interesting)

    by Sparr0 ( 451780 )
    who says the universe is mostly matter? maybe its exactly half and half, they just got segregated really well. There could be entire antimatter galaxies out there and we would never know they werent 'normal' until we tried to visit them. The radiation of random particles (H and anti-H) at the bounds of the galaxies wouldnt be very noticable, if at all.
    • Because once the antiphotons hit our eyes we'd all annihilate.

      • Re:why not? (Score:5, Informative)

        by Anonymous Coward on Friday August 06, 2004 @06:29PM (#9904127)
        photons are their own antiparticles in the standard model.

      • Re:why not? (Score:5, Informative)

        by jerde ( 23294 ) on Friday August 06, 2004 @06:57PM (#9904365) Journal
        Because once the antiphotons hit our eyes we'd all annihilate

        No such thing. Or, at least, the photon is its own anti-particle, as far as I can find. I am not a particle physicist, nor do I play one on TV, but my limited understanding is that matter is a type of "frozen" energy with certain charge and spin, and anti-matter is the same phenomenon but with opposite charge and spin.

        Photons are just energy, with no properties you can put backwards as in anti-matter. I did find a number of pages out there that talk about anti-photons as somehow photons moving backwards in time, but I can't quite wrap my mind around that one.

        Anti-matter would "look" the same as matter from a distance, I think. The glow of an anti-matter star would be pretty and warm, until you got close enough for the anti-matter solar wind to start annihilating you.

        - Peter
      • As the others said anti-photons are indistinguishable form regular types but even if they weren't the anti-photons would only annihilate photons, not the mass in our eyes.

    • Re:why not? (Score:3, Informative)

      by Carnildo ( 712617 )
      Gas-cloud mapping shows that the universe isn't that well segregated, and if it isn't perfectly segregated, hydrogen-antihydrogen annhilation produces a distinctive signature.
      • yes, its distinctive... but is it "loud"? whats the particle density in inter-galactic space (not interplanetary or even intersolar, even though those are 'hard vacuum' by any normal definition)? take that, do some statistical analysis... if two distant galaxies were of opposite components (normal and anti), how often would a H/AntiH reaction take place on their 'border'? How much radiation would it produce? Would it even be noticable above background radiation? What are the odds that we are so deep

        • Re:why not? (Score:3, Insightful)

          by Sparr0 ( 451780 )
          i dont know why i said intersolar instead of interstellar. brain fart i guess.

        • Re:why not? (Score:1, Interesting)

          by Anonymous Coward
          Loud? There's few (none?) reactions that release as much energy with so little mass. There should also be place where we'd see such a reaction edge on. That would be hard to miss.

        • Re:why not? (Score:4, Informative)

          by Alsee ( 515537 ) on Saturday August 07, 2004 @07:48AM (#9907874) Homepage
          I'm no astrophysicist, but yeah, it would be "loud enough" for us to see. It has an extremely sharp and "hot" energy signature. Quite distinctive. Even a low level would blaze above the cosmic background if you look at the specific frequency.

          About the only way we could miss it would be if we we so "deep inside a matter boundry" that in every direction the boundary was outside the limit of the visible universe, some 15 billion or so light-year radius.

          Assuming adjacent galaxies could be opposite doesn't really work. Not only is there is far too much contact through intergalactic gas, but galaxies collide with each other almost routinely. It is believed that essentialy all elliptical galaxies (about 10% of all galaxies) are the result of roughly equal mass galaxies colliding, and that many "normal" galaxies have collided-with/gobbled-up smaller galaxies and restabilized.

          Here [www.xtec.es] is a Hubble photo of actual colliding galaxies, and here [stsci.edu] is a really neat 7.3 meg MPG of a galaxy collision simulation.

          Needless to say, it would be kinda hard to miss the fireworks from a matter-antimatter galaxy collision. It would likely be visible in broad daylight.

          Even aside from the radiation signature, large scale regioning doesn't work either. If it were within the range of current galaxy mapping (some 7 billion light-years or so) we would see the exact opposie of what we do actually observe. Matter-antimatter anihilations would carry the mass-energy away from the border zones. The lower gravity in the buffer regions would produce "walls" of low-density vacuum surrounding blobs of gravitating mass. Instead the large-scall mapping projects show "walls" of mass surrounding bubble-voids.

          To explain that better, the large-scale structure has been compared to a foam. The bubbles in the foam are voids in space in the foam-film is made up of galaxies. And like the soap film, the galaxies are essentially all linked together in sheets and walls rather than being surrounded by anihilation bubbles.

          -
    • It seems more likely that there is a time-reversed antiuniverse, because otherwise this one would have annihilated a long time ago. Hopefully our universe won't keep expanding though the cosmos and make contact with that antiuniverse. That would be one heck of a light show :)
    • Well, galaxies do collide. Astromers can find some colliding galaxies, right now.If half the galaxies were anti-matter galaxies and half regular galaxies, then one fourth of galactic collisions would be matter to anti-matter. The annihilations of these galaxies would be very noticable. Furthermore, why would the matter and anti-matter segregate to begin with. Wouldn't galaxies just just form with half of both leading to lots of annihilation and a radiation dominated universe.
      • ... assuming equal dispersion of the two.

        The original poster mentionned that they may be well spread out.

        You'd need to find two galaxies colliding in the area of space where the antimatter galaxies meet the normal galaxies if they were half and half.

  • 1606 decays in 200 million pairs (Score:3, Interesting)

    by Marxist Hacker 42 ( 638312 ) <seebert42@gmail.com> on Friday August 06, 2004 @06:31PM (#9904143) Homepage Journal
    Something tells me their decay detector is NOT 98% accurate as claimed.
  • . . . that, since the area around the Sand Hill Road exit on I-280 in Menlo Park still exists, SLAC has *not* yet succeeded in bringing matter and amtimatter together.

    Yeechang, who worked for two years in that exact location

    • Re:We can also conclude . . . (Score:5, Informative)

      by rangek ( 16645 ) on Friday August 06, 2004 @08:39PM (#9905266)

      since the area around the Sand Hill Road exit on I-280 in Menlo Park still exists, SLAC has *not* yet succeeded in bringing matter and amtimatter together.

      Huh? SLAC's whole purpose in life is to fire electrons and positrons at each other. The resulting collisions create the deacys they study. Why would this make "the area around the Sand Hill Road exit on I-280 in Menlo Park" no longer exist?

      If all of the energy of one positron and one electron were released in a collsion in the SLAC, something like 3 billionths of a Joule. Well, there could be a lot of particles... Hrm... digging around http://www.slac.stanford.edu/ and crunching their numbers... I get a total output on the order of 3000 kJ/s if all of their particles collide with each other. Gasoline has a heat of combustion of about 43MJ/kg, so that is the same amount as burning 7 thousandths of a kilo of gas per second.

      I think Menlo Park and the surrounding are are quite safe.

      • ... 3 billionths of a Joule.

        ...3000 kJ/s
        ... 7 thousandths of a kilo of gas per second
        Isn't that the same is 1 nanojoule, 1 mJ/s, and 1 gram per sec of gasoline? What good is the Metric system if you don't combine thousandths of kilograms to get grams?
        • Yeah, yeah. That would have been clearer. I was just mushing a bunch of stuff together. The point is it doesn't really matter if it is 7 kilos or 7 grams. They are many orders of magnitude away from blowing up the place.

  • No authors of hep-ex/0407057 can endorse [arxiv.org] Observation of Direct CP Violation in B0 -> K+pi- Decays
  • Check out the author list on the paper [arxiv.org] in the arxiv, it's like 2 pages long!!! When did author lists get so long?

    • Re:wow (Score:3, Informative)

      by PhysicsChick ( 803627 )

      >When did author lists get so long?

      The author lists got so long when the experiments became too expensive and complicated for any one group to run by themselves. Because so many different groups contribute in many different ways (through construction, testing, writing specialized software, or analyzing results) they all have to be acknowledged.

      I'm author #104 of #113 on a different paper (I went to a university very near the end of the alphabet), and it doesn't bother me at all that I have realtivel

      • I'm author #104 of #113 on a different paper (I went to a university very near the end of the alphabet),
        So, the rise to prominence of Aarhus university (in Denmark) is explained.

  • Dramatic Difference In Matter Vs. Antimatter? (Score:1, Funny)

    by Anonymous Coward
    There has always been a dramatic difference between matter and anti-matter, they are opposites! It doesn't get any more different than that.

  • Oops! (Score:4, Funny)

    by eingram ( 633624 ) on Friday August 06, 2004 @09:14PM (#9905562)
    We have observed a clear, strong signal for asymmetrical behavior By observing they changed the outcome of their experiment! ;)

  • Quark Mixing? (Score:3, Interesting)

    by pubudu ( 67714 ) on Saturday August 07, 2004 @06:06PM (#9910390)
    The CP violation in the decay of B mesons is more noticeable than in the decay of neutral Kaons (K0), so my question isn't entirely offtopic. I'm really confused by neutral kaons and the 'quark mixing' that describes them, and was wondering if anyone could help me out here. Since I can't put a bar over letters or use Greek characters, I'll put antimatter in bold italics and use P for an uppercase 'psi'.

    The composition of K+ makes perfect sense (up and anti-strange), as does that of K- (anit-up and strange). But K0 makes no sense at all (both long and short K0). What is K0-short? (P(d s ) + P( d s)) * 2^-1/2. And K0-long just replaces the '+' with a '-'. I'm told this is due to quark mixing. But I have absolutely know idea what it means to say this. Any help?

    • I am in a similar but more humble boat than you - I have even less physics skills to come to grips with the issue. I wish someone would try and explain an anomlay in what after all has been cornerstone in our understanding of physics. The other comments seem to be following the path of reality TV descending into content free pap designed to make the author and reader feel good about being ignorant. A great pity as Slash dot used to be about "Stuff that matter"
  • At a very high level, this seems to be similar to chirality among amino acids.

    Even though the molecules can be either left or right handed, there is a predominance of left handedness among amino acids.

    This is similar to matter where the left handedness of an amino acid is synonymous with matter and the right handedness with antimatter.

    Although matter and antimatter are almost mirror images of each other and left and right handed amino acids are mirror images of each other, small differences result in a p
    • So I remember reading a few years ago that there was a slight asymmetry in chirality of amino acids found in asteroids - anyone know if more data has been found? Or theories on _why_ there would be this asymmetry?

      I seem to remember that some famous physicist was quoted when they discovered an asymmetry due to the weak nuclear force in (muon?) decay that "God is not left-handed!" (similar to "God does not play dice").

      But apparently, God plays dice left-handedly. =)

      -Marcus

      (Note that with amino acids, bi
      • You can google on "chirality amino acids" and you'll get some relevant links, including some humorous religious ones that get the final point incorrect.

        My asteroid hypothesis is that different conditions gave rise to different tendencies which may lead to different molecules.

        Also check on New Scientist, Eurekalert and Sciencedaily's sites for more info.

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