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Encounters between a particle and an antiparticle lead to both of them being destroyed. This gives rise to high-energy photons (gamma rays), neutrinos, and lower-mass particle–antiparticle pairs.

What is it made of?[change | change source]



Annihilation[change | change source]


In 1928, the physicist Paul Dirac was looking for an equation that would predict how very fast particles should behave. There was already another equation that could describe slow-moving particles, the Schrödinger equation, but Einstein's theory of special relativity said that fast particles could be very different from slow particles. Dirac knew that particles like electrons were usually moving very fast. He realized the old equation would not make good predictions for fast particles. So he came up with a new equation that could describe particles moving close to the speed of light.[1]

For fast particles, it is no longer true that the energy is . Instead, Dirac's new equation worked for particles where the energy was given by . In the new equation for energy, the symbol is called the momentum, and it measures how fast the particle is going and how hard it is to stop. This equation says that very fast particles have more energy, so they are different from slow particles. You can take the square root of each side of this equation, since both sides are equal. However, any real square root has two answers, and . You can think of the answer with negative energy as being antimatter.[2]


Where is all the antimatter?[change | change source]

Many scientists think that in the first few moments after the Big Bang, which created the universe a very long time ago, both matter and antimatter mixed together. If the Big Bang made equal amounts of matter and antimatter, then the two would annihilate and become energy. After a long time, there would be no matter and no antimatter left, just energy. But our universe today looks like it is almost all matter and hardly any antimatter. Physicists do not yet know for sure that equal amounts of matter and antimatter were created, and because of this, they are also wondering where the antimatter went, and if any was left over from the beginning of the universe.

One explanation is that there was just a little bit more matter than antimatter in the beginning, so that whatever was left over after most of the matter and antimatter annihilated into energy became the mostly-matter universe we see today. Another theory is that there is lots of antimatter on the other side of the universe, hidden far beyond our vision. They could have formed their own galaxies and solar systems too.

Uses[change | change source]




References[change | change source]

  1. Dirac, P. A. M. (1928-02-01). "The Quantum Theory of the Electron". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences. 117 (778): 610–624. doi:10.1098/rspa.1928.0023. ISSN 1364-5021.
  2. Griffiths, David J. (David Jeffery), 1942- Introduction to elementary particles. 2nd ed. (2013). Studyguide for Introduction to elementary particles by Griffiths, David, 2nd edition. Cram101. ISBN 1490226435. OCLC 858962936.CS1 maint: multiple names: authors list (link) CS1 maint: extra text: authors list (link)