Anti-Matter

What exactly is Anti-Matter?

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Particle Science
March 05, 2024

Anti-Matter

What is Anti-Matter?

What is Anti-matter and who came up with it?

You might have heard of this scientist before, but maybe you didn’t know his connection to this topic. His name is Paul Dirac, and he was responsible for first theorizing about the existence of anti-matter.

Dirac in 1928 came up with a new equation to describe particles like electrons when traveling close to the speed of light.

This is the equation right here:

However, he found that his equation had two different solutions, just as the square root of a positive number has two solutions. One of these solutions described an electron, while the other solution he at first dismissed. After 3 years he then said that the other solution was actually describing something that exists in real life, an anti-electron.

This anti-electron has the same properties as a normal electron but with only one change, it has an opposite charge. This means that if an electron has a negative electric charge, then the anti-electron has a positive electric charge. We can also call an anti-electron a ‘positron’. What’s interesting about this is also that the same is true for every particle, including quarks, which make up protons, and hence the existence of ‘anti-protons’. If there are anti-electrons and anti-protons, then there must be anti-atoms!

Anti-atoms make up anti-matter, just as atoms make up matter!

What does this mean?

Well, this means that it would be possible to have things that are made up completely of anti-matter since it’s essentially the same thing as matter but with an opposite electric charge. There could be entire planets made up of anti-matter, entire stars, galaxies, and perhaps universes.

Have we detected Anti-Matter?

Anti-matter is not just a thought or an idea, in fact just 4 years after Dirac came up with his equation, Carl Anderson took a picture of a particle going through a bubble chamber (Just know that a bubble chamber is used to detect electrically charged particles) and measured a particle that had the same mass of an electron, but with a positive electric charge, this was the first-ever detection of anti-matter!

Matter-Antimatter Asymmetry

There’s a pretty interesting interaction that happens when matter and anti-matter come into contact, they annihilate each other.

Since matter and anti-matter are identical except for their opposite electrical charges, we expect them to have been created at the big bang in equal amounts. The problem is that this is clearly not the case, since first of all, if there were equal amounts of matter and anti-matter created in the universe, they would have annihilated each other, and the universe would only be a structureless ocean of radiation. Secondly, we know this is not the case because it it were, our universe as we know it would not exist.

This has puzzled physicists for a long time, and is known as the Matter-Antimatter Asymmetry problem.

Some people have questioned if maybe the anti-matter got separated from matter and it’s still somewhere in the universe. Another possibility might be that somehow, just after the big bang, there could have been an extremely tiny imbalance of matter and anti-matter, an imbalance of only 1 extra proton per 1 billion anti-protons. This imbalance would be enough to get everything that we see in the universe today.

The Matter-Antimatter Asymmetry problem is something that we are currently trying to answer. Perhaps you might be the one to help out someday to find an answer!

Questions that may arise from this topic:

  • Are there anti-universes?

  • What is a Bubble Chamber?

  • What are all the particles known?

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Bibliography:

What is Antimatter? (World Science Festival)

Scientists get closer to solving mystery of antimatter (BBC)
https://www.bbc.com/news/science-environment-66890649

Why Is There More Matter Than Antimatter? (Scientific American)
https://www.scientificamerican.com/article/why-is-there-more-matter-than-antimatter/

The matter-antimatter asymmetry problem (CERN)
https://home.cern/science/physics/matter-antimatter-asymmetry-problem