How do we know about anti matter?

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I understand antimatter is the opposite of matter and that it pops into existence and then disappears again as soon as it encounters matter (usually pretty instantly). But how did we even think to look for something that has such a fleeting existence? Was it the only logical way to explain the results of some experiment? Is there something about matter that doesn’t make sense unless antimatter exists?

In: Physics

4 Answers

Anonymous 0 Comments

It started with doing the math. A physicist named Paul Dirac figured out an equation that explained how electrons moved, and the equation worked to predict behavior. The equation also made it seem possible that there could be an oppositely charged particle to an electron (a positron), and any atoms built with positrons rather than electrons would be atoms of anti matter.

Years later, another physicist doing experiments related to cosmic rays observed a positron in the experiment, which was physical evidence that Dirac was right. That physicist was Carl Anderson.

Anonymous 0 Comments

It pops up in cloud chamber traces occasionally, which we have been doing for a long time. Also it is predicted by the varios Quantum equations/theories.

I don’t know if if was noticed or predicted first though.

Anonymous 0 Comments

in the late 1890s there was a physicist named schuster who wrote some letters to nature where he came up with the word and hypothesized about some speculative types of matter, but even speculated about the annihilation when antimatter meets “normal” matter. But the modern theory comes from a paper by Dirac in the 1920s. He came up with a relativistic version of schrodinger’s wave equation for electrons, and the possibility of antielectrons were predicted from solutions to that wave equation. He credits Oppenheimer with the prediction, since he argued for the existence of a positron instead of a proton on the grounds that the particle must have equal mass to an electron, not just opposite charge.

The first experimental evidence was in the 50s, when scientists found antiprotons during an experiment with particle accelerators. If you smash particles into eachother with enough energy, they will break apart and release other particles. You then set up detectors in a magnetic field. Based on how these particles move through this magnetic field, you can infer their charge and their mass and categorize them. Comparing experimental data with theory using Dirac’s equations from the 20s-30s allowed them to confirm the existence of lots of different antiparticles. We’ve since found antiparticles all over the place in nature too – in cosmic rays, as products of radioactive decay, above clouds during thunderstorms, etc.

The short answer is we thought to look for them because solutions to the math suggested they existed, and then we went looking and did find them.

Anonymous 0 Comments