Antimatter

The Mirror of the Universe

Antimatter is truth stranger than fiction. While its ability to obliterate when it meets normal matter produces energy bursts that inspire fictional bombs and starship engines, it also plays a crucial role in solving some of modern physics’ biggest questions and mysteries.

You don’t need to delve into science fiction to encounter it; in fact, small amounts of antimatter exist in your body. This occurs because potassium decays and occasionally releases positrons, which are anti-electrons. Yes, that means bananas, which are rich in potassium, are also a source of antimatter.

Paul Dirac, 1933

Paul Dirac, 1933

The story of antimatter starts with British physicist Paul Dirac. In 1928, Dirac combined quantum mechanics, which deals with subatomic particles, with Einstein’s theory of relativity. This was to explain the behavior of electrons moving close to the speed of light. His equation suggested that, much like the solution to x2 = 4 can be x = 2 or x = −2, there could be an electron with positive energy and another with negative energy.

While classical physics argued that energy must always be positive, Dirac went against the grain. He suggested that every particle has a mirror-image counterpart with the opposite charge. For the electron, this counterpart is the positron, which is identical in every way except for its positive charge. This revolutionary idea opened the door for the possibility of entire galaxies and universes made of antimatter.

American physicist Carl Anderson validated Dirac’s theory a few years later. While studying cosmic rays that strike the Earth’s atmosphere, Anderson observed a particle in his detector with the same mass as an electron but with a positive charge. This discovery confirmed the existence of positrons. Both Dirac and Anderson received Nobel Prizes in Physics for their groundbreaking discoveries, Dirac in 1933 and Anderson in 1936.

Cloud chamber photograph by Carl Anderson of the first positron ever identified

Cloud chamber photograph by Carl Anderson of the first positron ever identified

However, when matter and antimatter meet, they annihilate, releasing vast amounts of energy. Following the Big Bang, the universe was only energy. As it cooled and expanded, both matter and antimatter came into being. Considering that both were produced in equal quantities and behave similarly, logic dictates that all matter and antimatter should have annihilated one another, leaving the universe empty. So, the overarching question is: why does the universe contain more matter than antimatter? This puzzle remains unsolved.

One theory suggests that slightly more matter than antimatter was created at the universe’s inception, leaving enough matter to eventually form stars, galaxies, and everything on Earth. According to this idea, less than 1 in 1 billion ordinary particles survived to constitute the present-day universe.

The neutrino—a minuscule, elusive particle that rarely interacts with matter—could hold the key. If it indeed acts as its own antimatter counterpart, a tiny percentage of neutrinos might have transitioned from antimatter to matter during the early universe, causing a slight imbalance. Experiments aiming to verify this idea have yet to provide a definitive answer.

Today, we can produce antimatter using advanced particle accelerators like the Large Hadron Collider near Geneva, operated by CERN. Scientists there have created antihydrogen and even antihelium, the most complex form of antimatter known to date. Researchers are also examining whether gravity affects antimatter in the same way it does matter. These experiments are pushing the boundaries of our understanding of the universe’s fundamental laws. Only time will tell what new discoveries await.

TL;DR

Antimatter was first theorized by Paul Dirac in 1928, suggesting every particle has an opposite-charge counterpart. It was confirmed by Carl Anderson’s discovery of the positron, an anti-electron, in the early 1930s, earning both Nobel Prizes. While fascinating for its energy-releasing annihilation with matter, antimatter also poses a scientific puzzle: why does the universe contain more matter than antimatter, given that both should have been created in equal amounts after the Big Bang? This puzzle remains unsolved. Today, CERN produces antimatter, investigating its properties and how gravity affects it, continually advancing our understanding of the universe’s fundamental laws.

Editors’ finds

Words of wisdom

“I am a slow walker, but I never walk back.” —Abraham Lincoln

“Sometimes it is the people no one can imagine anything of who do the things no one can imagine.” —Alan Turing

“We have now sunk to a depth at which restatement of the obvious is the first duty of intelligent men.” —George Orwell

“The only way to deal with an unfree world is to become so absolutely free that your very existence is an act of rebellion.” —Albert Camus

Bibliography

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