back to article We know what you're thinking: Where the hell is all the antimatter?

The mystery behind why there is an imbalance between matter and antimatter in the universe could be one step closer to being solved. First, let's kick off with some gentle particle physics to set the scene. Scientists are hunting for something called neutrinoless double beta decay: in normal double beta decay, two neutrons …

  1. Forget It

    Feynman diagram here

    https://upload.wikimedia.org/wikipedia/commons/thumb/3/34/Double_beta_decay_feynman.svg/375px-Double_beta_decay_feynman.svg.png

    https://en.wikipedia.org/wiki/Double_beta_decay#Neutrinoless_double_beta_decay

  2. DougS Silver badge

    What if there are supermassive Majorana particles?

    In the early stages of the universe when matter first began to condense out of the soup of energy, some really high energy particles (maybe so high energy we have no hope of ever creating them in a particle accelerator) that are their own antiparticle could have been created. If those preferentially decayed into 'matter' rather than 'antimatter' that would neatly explain why matter appears to be the majority in the universe.

    Unfortunately, if this is true we won't ever have any way of proving it. However, the existence of Majorana particles that are created only in accelerators and don't exist in nature proves that this is a possible explanation.

  3. Zog_but_not_the_first Silver badge
    Boffin

    Mexit, of course

    Mexit (matter-exit). When we took back control and turned our back on those meddling anti-bosons and anti-fields. We got back proper curved spacetime as God intended. And to all those downvoters mumbling about dark energy...

    1. AIBailey

      Re: Mexit, of course

      Mexit means Mexit!

    2. Anonymous Coward
      Anonymous Coward

      Re: Mexit, of course

      "We got back proper curved spacetime as God intended."

      Heresy! Clapton intended space-time to be flat.

      Anyway, even though it works, just about, the Standard Model is a botched, bloated mess. Wish I could think of an analogy to illustrate the point...

      1. Anonymous Coward
        Anonymous Coward

        Re: Mexit, of course

        "Wish I could think of an analogy to illustrate the point..."

        The standard model feels like it's likely to be analogous to the geocentric model of the solar system. Sure the equations accurately predict the results, but that's because they've been finessed until they fit the data. They don't explain the underlying phenomena.

      2. Jos V

        Re: Mexit, of course

        LeeE, were you looking for this to illustrate the point?

        https://xkcd.com/1489/

    3. allthecoolshortnamesweretaken Silver badge

      Re: Mexit, of course

      I still say it's just a glitch in The Matrix. Should be fixed in one of the next patches.

    4. I ain't Spartacus Gold badge

      Re: Mexit, of course

      It's nothting to do with physics at all.

      All the anitmatter in the universe got used up making Antipopes.

      Wikipedia (I know, I know, but I'm too lazy to do the research properly) lists 41 of them over the years.

      Since we've not had an antipope since the 16th Century and we can't see any antimatter (except that we create ourselves), this proves that there's none left. QED.

  4. Your alien overlord - fear me
    Paris Hilton

    I don't think anyone really knows where stuff you can't see has gone.

    Hang on, if something you can't see isn't there, how do you know it's missing? Science eh !!

    Paris - only brain ache icon available

    1. Swarthy Silver badge

      Not to Antigonish anyone....

      As I was going up the stair

      I met a particle who wasn't there!

      It wasn't there again today,

      Oh how I wish it'd go away!

      1. Frumious Bandersnatch Silver badge

        Re: Not to Antigonish anyone....

        Flappity, floppity, flip

        The mouse on the mobius strip;

        The strip revolved,

        The mouse dissolved

        In a chronodimensional skip.

        1. Swarthy Silver badge

          Re: Not to Antigonish anyone....

          The mouse dissolved

          In a chronodimensional skip.

          With a bit of a mind-flip

          You're into the time slip

          And nothing can ever be the same.

  5. Hollerithevo Silver badge

    IANAS

    I an not a scientist, but it must be the most awesome peak of coolness to be able to spend your working life around tanks of argon and tracking anti-matter. Makes everything else look like tiddlywinks.

    1. Anonymous Coward
      Anonymous Coward

      Re: IANAS

      F**k yes. I walked away from High Energy Physics (as an electronic eng doing H/W and S/W for it) in the early 80's thinking I'd earn more spondoolicks in the commercial world.

      Biggest regret of my life. Even bigger than my first marriage. Could have been working on the LHC. And had a decent pension, thanks to USS (the UK Academic scheme). Only prob, I'd probably have become an alcoholic.

      1. hnwombat
        Pint

        Re: IANAS

        = I'd probably have become an alcoholic.

        So, no downside?

      2. anothercynic Silver badge

        Re: IANAS

        An alcoholic? Nah! Too much fun to be had*! :-)

        * speaking as someone working in that sector.

    2. Anonymous Coward
      Anonymous Coward

      Re: IANAS

      Potentially the most boring job in the world surely? Awaiting something that may never happen and when it does it will be a tiny blip on a computer oscilloscope, rather than a 'must-see' supernatural event.

      1. Tom 7 Silver badge

        Re: IANAS Boring? Never

        My first proper job after big school was chip designing. Running automated checks on the computers that were around then used to take several days. Several days spent researching things related to work that may or may nor help in my job. Never a must-see supernatural event but the flashes of recognition of other peoples brilliance were fireworks enough for me. Admittedly working with people at the pinnacle of any 'discipline' can give you imposter syndrome but if you cant get a buzz out of learning you should move into management and abuse people instead.

        1. Anonymous Coward
          Anonymous Coward

          Re: IANAS Boring? Never

          Yeah, it's pretty bloody awesome when a guy who was a PhD student when I was working there has gone on to be the main architect of the CMS experiment (Jim Virdee).

    3. Trigonoceps occipitalis

      Re: IANAS

      "Makes everything else look like tiddlywinks."

      I believe the correct pastime is "stamp collecting".

      1. ridley
        Big Brother

        Re: IANAS

        I say, well done

    4. The First Dave

      Re: IANAS

      Would it have been too hard to mention that the Argon is at approx 88 degrees in proper SI units?

      Incidentally, does anyone know why, and is there any relation to 'Back to the future' style time travel?

  6. Little Mouse

    No charge

    In trying to create a charge-free environment, have they considered siting the experiment in a room without a woollen carpet? Plus, the scientists should avoid rubbing balloons against their jumpers. And wearing polyester-mix trousers.

    It seems obvious, but it's best to double-check these things.

    1. Kubla Cant Silver badge

      Re: No charge

      the scientists should avoid rubbing balloons against their jumpers. And wearing polyester-mix trousers

      The carpet and balloon requirements can be met, but I'm afraid polyester-mix trousers are non-negotiable for scientists. There may even be the odd nylon shirt in there.

      1. Michael H.F. Wilkinson Silver badge
        Happy

        Re: No charge

        Polyester-mix trousers? Sorry, but no!! I am a scientist and wear cotton for preference: my t-shirts (Pratchett Processor/Anthill Inside logo today) and jeans are cotton.

        1. theN8
          Thumb Up

          Re: No charge

          +1 for the Discworld Tee!

  7. Daedalus Silver badge
    Boffin

    The little man who wasn't there

    Let's be clear here: identifying a neutrino-less decay could be seen as a matter of not detecting something that you can't detect anyway. A neutrino, or in this case an antineutrino, has a 50% chance of making it through half a light-year of solid lead.

    But of course I'm sure they've thought of that.

    1. Tom 7 Silver badge

      Re: The little man who wasn't there

      They have - they have shit loads of men who aren't there so they can miss most of the things that dont happen and still have a good chance of seeing it.

    2. I ain't Spartacus Gold badge
      Happy

      Re: The little man who wasn't there

      Method:

      1. For this experiment, we first manufactured a 1/2 lightyear cube of lead.

      2. Then we sat and had a cup of tea, while waiting for some neutrinos to come along.

      3. ...

    3. DavCrav Silver badge

      Re: The little man who wasn't there

      "But of course I'm sure they've thought of that."

      Yes, they have. Because they know what they are doing, and have decades of experience with this thing. Some of them will have produced the factoid you are quoting.

      "A neutrino, or in this case an antineutrino, has a 50% chance of making it through half a light-year of solid lead."

      But there's loads of them.

      1. Daedalus Silver badge

        Re: The little man who wasn't there

        After a little thought, it comes out like this:

        The neutrino was originally discovered because, after physicists added up the bits after a nuclear reaction and compared them with the bits they started with, there was something lost, so something undetectable must have sneaked away.

        So to detect a neutrino-less event, you look for ones where the before and after bits all add up to the same.

        Which means that instead of knowing something was there because there was something was missing, they will know that nothing is there because nothing is missing.

  8. Andy The Hat Silver badge

    Neutrino and antineutrino

    If the neutrino is its own antiparticle, wouldn't this be more easily be detected by studying neutrino/neutrino decay directly?

    What we seem to have is the study of a theoretical decay chain which in itself requires a theoretical decay mechanism ... To me that smacks of Nobel Prize or little hope of success ...

  9. Dr. G. Freeman

    All the matter-antimatter's gone bang already, we're the left-over ash, and "Dark Matter" is the smoke.

    It was a big bang after all.

  10. Chris G Silver badge

    The neutrinoless double-beta reaction?

    I just don't see it!

  11. andrewj

    MAGA

    Make Antimatter Great Again!

  12. Androgynous Cow Herd

    The thing about anti-matter

    it doesn't really matter.

    1. Jos V

      Re: The thing about anti-matter

      Yeah true, or...

      So close no matter how far

      Couldn't be much more from the heart

      Forever trusting who we are

      And nothing else matters

  13. Kernel

    They're looking in the wrong place!

    I seem to remember watching some US based physicist on TV not that long ago who stated that bananas are a (comparatively) rich source of anti-matter - something to do with the potassium 40 they contain. Apparently a banana will emit a positron approximately once every 75 minutes.

    Instead of spending money on flash kit they need to get down to the local supermarket with a halfway decent knife and start slicing.

    1. Anonymous Coward
      Anonymous Coward

      Re: They're looking in the wrong place!

      Is that you, Ray "Banana Man" Comfort?

    2. Orv Silver badge

      Re: They're looking in the wrong place!

      Severe thunderstorms also seem to produce antimatter naturally -- or at least, they produce hard gamma rays at energy levels that we only know how to explain as matter-antimatter reactions. This is one of those things we discovered by accident while looking for something else -- a satellite intended to study cosmic gamma ray sources was getting hit by occasional short bursts so close by that they overwhelmed all of its detectors.

      https://en.wikipedia.org/wiki/Terrestrial_gamma-ray_flash

  14. caffeine addict Silver badge

    I am not a scientist...

    I'm very very much not a scientist, but this has always appealed to me...

    If space is n-dimentional, why couldn't the big bang have gone in two directions down one one those dimensions, with *most* of the matter being flung one way, and most of the anti-matter being flung the other way?

    The bonus to that is that you get two universes which would explode if they ever came into contact with each other, which makes science fiction much more fun.

    1. Roj Blake Silver badge

      Re: I am not a scientist...

      Or maybe the antimatter was flung backwards in time...

  15. Anonymous Coward
    Anonymous Coward

    anti-matter...

    ...schmanti-matter.

    The only matter regarding matter that matters is whether Timecop was right. Science isn't working hard enough in the area of pub quiz question creation.

    Can the same matter occupy the same space?

  16. Anonymous Coward
    Anonymous Coward

    Sorry, I goofed up.

    I've got all the extra antimatter. It's in my shed. Sorry. I didn't realise it was causing a problem. I was going to sell it on eBay.

    If someone posts an address here, I'd be glad to return it all, providing I can afford the postage.

    AC - because there's nothing more dangerous than a herd of irate theoretical physicists.

    1. caffeine addict Silver badge

      Re: Sorry, I goofed up.

      It's okay. As soon as they get up to speed, they lose track of where they are...

    2. Orv Silver badge
      Black Helicopters

      Re: Sorry, I goofed up.

      Zephram Cochrane, is that you?

  17. Scroticus Canis Silver badge
    Paris Hilton

    Explain where the positive charge comes from

    Neutrinos and anti-neutrinos are neutral, no charge hence the name. So how does the theoretical lack of a neutrino or anti-neutrino (or two) impart a positive charge to the inside of the chamber?

    Neutron (no charge) decays producing a proton (positive charge), an electron (negative charge) and an anti-electron-neutrino (no charge). Charge is conserved as the proton and electron cancel each other's charge. Do it twice still no net charge.

    Must be fucking magic! Unless some how the energy the anti-neutrino would normally have carried away from the decay (neutron being slightly heavier than a proton plus an electron) gives the electrons enough extra velocity to escape the germanium thus leaving a positive charge.

    Any ideas?

    1. Gio Ciampa
      Coat

      Re: Explain where the positive charge comes from

      Paragraph 2: "in normal double beta decay, two neutrons convert to protons and two electrons"

      Same thing happens in the neutinoless version...

      (Mine's the one with the Physics degree ... OK - it was a Third: if only I'd proved there was a Black Hole under the Department of Physics at Birmingham...)

  18. Anonymous Coward
    Anonymous Coward

    As we know, there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns – the ones we don't know we don't know.

  19. adam 40

    What's the spectrum of Antihydrogen?

    Funny I typed this last night but maybe it was in positrons and annihilated itself. Anyhoo - here goes - again.

    How do we know that distant galaxies aren't antimatter. Maybe "where the hell is it" - is all around us?

    I still haven't had a decent explanation of why this can't be the case.

    We are quite close to being able to measure the spectrum of antihydrogen, although it should be the same as normal hydrogen, if there do turn out to be some subtle differences then we will know what to look for out there.

  20. leliel

    We have observed the spectrum of antihydrogen, just before christmas. It is identical to hydrogen :(

    Biggest reason why other galaxies can't be antimatter is that intergalactic space isn't completely empty, only nearly so. The boundary between matter and antimatter would glow with a characteristic gamma energy. it doesn't, so it isn't there.

    1. adam 40

      I've heard this assertion before about the glow from annihilation events. So I started looking into what we should be looking for.

      Of course you are only going to get this effect between am/m pairs, not m/m or am/am.

      Proton/antiproton annihilation results in a pair of gamma rays of around 938MeV. These may be red-shifted if the galaxies are far away, so we could be looking for a spectrum maybe between 90-900MeV.

      What about the intensity of this radiation (if it were there) what would we expect? Would all the gas have mixed and annihilated aeons ago, or do you expect to see gas streaming out of the galaxies still? If so, at what rate?

      Finally, looking at various observations from gamma ray observatories, these are currently at low resolution and show some radiation that may overlap with the expected spectrum. So I don't think the matter is settled, unless you can come up with specific research sources that can demonstrate the negative result with some certainty.

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