• Question: What is antimatter

    Asked by markbarwell to Andrew, Daniel, Hayley, Natalia, Peta on 17 Nov 2011.
    • Photo: Daniel Scully

      Daniel Scully answered on 15 Nov 2011:

      Anti-matter is identical to matter in every possible way, except that all their properties have the opposite values:
      So if a particle has electric charge +1, its anti-particle has electric charge -1.

      The masses of a particle and its anti-particle are identical though. This is one of the rules of particle physics. If it wasn’t true, lots of other things could go wrong.

      Not all particles have an anti-matter partner, for example the photon. But all the particles which make up the matter we’re made of, like the electron, do have anti-matter partners (as far as we know).

      The thing most people know about anti-matter is that if it meets its matter partner, they annihilate each other into pure energy/radiation. Sometimes in fiction this is used as an idea for a bomb, but all you’d really do is give the people nearby a nasty radiation dose!

    • Photo: Hayley Smith

      Hayley Smith answered on 16 Nov 2011:

      Not really much to add to Daniel’s answer I don’t think…
      Except I always think it’s kind of cool that antimatter (positrons and antineutrinos) are produced in the naturally occuring beta decay (beta+ or beta-, I can’t remember off the top of my head whihc goes with which) of radioactive isotopes.

    • Photo: Peta Foster

      Peta Foster answered on 16 Nov 2011:

      Yes Daniel’s answer pretty much covers what it is….

      One might wonder why there is so much matter and so little antimatter…
      …it was suggested that at the point of the big bang lots of matter and antimatter was created and for some reason there was just a bit more matter and after the whole annihilation of the antimatter occurred we were just left with the matter. It does seem a bit like we could just have easily ended up as an antimatter world, but essentially this is one of the biggest unsolved problems in physics… why is there so much matter?

      Where would you get some antimatter then?…
      ….Well if you have a very intense laser you can create the antimatter at the focus. You can have certain radioactive isotopes which emit anti-matter as part of their decay process… however in our ‘all matter’ world it really doesn’t take very long before the antimatter is annihilated.

      What use is antimatter?…
      …well one of the current big uses is actually in medicine. You can use isotope that produce anti-electrons (called positrons) to allow you to trace and track things happening within the body. Cancer for example is greedy for sugar… so attach a anti-matter releasing radio isotope to a sugar molecule and away you go… you can now use the radiation that comes off (x-rays) when the positrons annihilate in order to work out where exactly that sugar went…. good stuff huh?

      Is there anything else weird about anti-matter?…
      … Well apart from the strangeness of having so much matter in the universe the work of Richard Feynman (a nobel prize winning physicist) says that anti-matter particles travel backwards in time! Yes you read that correctly… backwards in time 😀 Very weird stuff indeed!

    • Photo: Andrew Cairns

      Andrew Cairns answered on 17 Nov 2011:

      I think the particle physicists have the answer to this – leave the rest of real matter to Chemists! (JOKE!)

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