Antimatter is a mysterious and fascinating subject – a concept that has been explored in science fiction and real science alike. Scientists have been studying antimatter for over a century and yet there is still a lot left to uncover. In this article, we will explore the history of how antimatter was discovered and some of the pioneering experiments that have been conducted.
What is Antimatter?
Antimatter is a type of matter made up of antiparticles. It is distinct from regular matter, which is composed of particles. An antiparticle is an entity that shares identical physical properties to a particle, but with opposite electric charge – for example an anti-electron (or positron) is the antiparticle to an electron, and an anti-proton is the antiparticle to a proton.
The nucleus of an atom consists of protons and neutrons. Antimatter is composed of antiprotons and antineutrons in the nucleus. When matter and antimatter interact, they mutually annihilate into energy in the form of gamma rays. This phenomenon was suggested by Albert Einstein in his famous equation E=mc2, which is still used by scientists today.
Antimatter Defined
The term ‘antimatter’ was coined in 1928 by physicist Paul Dirac. He suggested that each type of particle has an antiparticle that is equal in mass, but opposite in charge. In other words, an electron has an antiparticle known as the positron, and a proton has an antiparticle called the antiproton; each of these would be equal in mass, but with opposite charges.
History of Antimatter
The idea of antimatter has been around for many centuries. Ancient Greek philosophers debated whether atoms were indivisible or could be split, which is the same fundamental question that scientists grapple with today. Ancient Greek scientist Democritus even hypothesized the reality of an undefined “anti-universe” in which particles had negative instead of positive aspects.
The Discovery
The discovery of antimatter truly began with the work of renowned British physicist Paul Dirac. In 1928, he published his famous equation, the Dirac equation, which predicted the existence of a subatomic particle with a positive charge- the antielectron, or more commonly termed the positron. A year after unveiling his equation, the correct version of the positron was discovered.
Paul Dirac
Paul Dirac was an English theoretical physicist who made a series of monumental contributions to the field of quantum mechanics. He was awarded the 1933 Nobel prize in physics for his contribution to the theory of electrons and for his discovery of the positron. Dirac’s famous equation is that of the Dirac Hamiltonian, wherein he proposed that matter and antimatter particles are equal but oppositely charged.
The Dirac Equation
The Dirac equation is a relativistic quantum mechanical equation that describes the behaviour of electrons, after the discoveries of quantum mechanics and special relativity. It attempts to explain the behaviour of scalar, spin-½ particles such as fermions, and in particular, the behaviour of electrons. It also predicted the existence of positrons or antiparticles of electrons.
CERN’s Contributions
The European Organization for Nuclear Research, more commonly referred to as CERN, is one of the world’s leading research institutions in particle physics. In the 1950s and ‘60s, CERN conducted an enormous number of experiments in the hopes of detecting traces of antimatter and understanding its properties.
The ALPHA Experiment
In 2002, the ALPHA experiment at CERN passed a major milestone in particle physics. Using a state-of-the-art detector, researchers successfully trapped antihydrogen atoms for the first time. This experiment provided the first evidence that antimatter could be contained in a laboratory.
The AEgIS Experiment
The AEgIS experiment at CERN is another groundbreaking project in antimatter research. This experiment is attempting to determine whether the force of gravity behaves differently when acted upon antimatter instead of regular matter. Initial results indicate that the force of gravity may in fact operate differently on antimatter.
Other Experiments
Since the early days of Dirac’s discoveries, a number of other experiments have been conducted to better understand the properties of antimatter. Most recently, researchers have used the Large Hadron Collider (LHC) to study high-energy collisions between particles and antiparticles.
It is remarkable to think that only a century ago, antimatter was still largely a concept existing within the realms of science fiction. But with the help of revolutionary research and experiments by scientists such as Dirac, CERN, and the AEgIS experiment, we have made tremendous progress in uncovering some of antimatter’s mysteries. Much of what we know about antimatter today is thanks to the pioneers of quantum mechanics and we continue to explore further and gain an even clearer understanding of this enigmatic substance.
