• Question: What is anti-matter?

    Asked by anon-231888 to Mark, Liam, Laura, Kasia, Gina, Felix on 12 Nov 2019. This question was also asked by anon-232577.
    • Photo: Mark Johnson

      Mark Johnson answered on 12 Nov 2019:

      Hey!

      Everything around us on Earth is made up of ‘normal matter’ – tiny subatomic particles like electrons, protons and neutrons. In the 1930s, scientists discovered that all of these particles have something called an ‘antiparticle’, with an opposite set of properties. For example, the electron has antiparticle called the positron (or ‘anti-electron’) that has a positive electric charge instead of a negative one. When a particle meets it’s own antiparticle, they are both ‘annihilated’ and converted into a flash of radiation.

      These days, physicists think our universe contained equal amounts of matter and antimatter just after it was created. This is a bit of a problem – if matter and antimatter cancel each other out, there would be nothing left to form stars, galaxies and planets today! I work on an experiment that’s trying to find tiny clues to explain why our universe only contains normal matter today.

    • Photo: Liam Gaffney

      Liam Gaffney answered on 15 Nov 2019:

      Radioactive isotopes emit anti-matter all of the time, even your banana. Bananas and other fruits and nuts are full of potassium and a certain fraction of that is potassium-40, which can sometimes decay by kicking out a positron. The positron is the anti-matter version of an electron, so there is anti-matter all around you.

    • Photo: Laura Sinclair

      Laura Sinclair answered on 19 Nov 2019:

      We use that concept of anti-matter in medical imaging. In Positron Emission Tomography (PET), we inject patients with a substance that emits positrons these collide with electrons in your body, this then produces two gamma rays back-to-back which can be used to create an image!

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