Hello folks! Welcome to our very first stem blog series- ‘Antimatter Unraveled’. We will post new episodes of this series every Friday for alternate weeks! In this series, you will learn and understand about Antimatter, how it originated in the world of Modern physics, and everything from its discovery to advancement.

Today, we are discussing the discovery of Antimatter, an unexpected new form of matter in the era of the Quantum Revolution.

When we study Modern Physics deeply, we often come across the term ‘Antimatter’ and how all particles in final theory must have an antimatter counterpart of themselves. So, what actually is Antimatter?

Antimatter obeys the same laws as an ordinary matter, except it has the opposite charge. Basically, Antimatter can be thought of as antiparticles of the corresponding particles of matter but with reversed charge, parity, and time. The famous particle that we often keep hearing about- Positron, is itself an antimatter of an electron (anti-electron) with a positive charge instead of a negative one. In fact, all subatomic particles have their anti-twins such as- antiquarks, antineutrinos, antiprotons, etc while spanning the boundary between a matter and its antimatter. And what is even more interesting is that these antiparticles can combine to form anti-atoms and in principle, antimatter, and regions in our universe filled with them(however, this has not been discovered yet)! In the further episodes, we will learn how scientists have created antiparticles and anti-atoms using particle accelerators.

So far we have understood, what Antimatter is. Now, a question might arise, what if Matter and Antimatter collide? When they do so, they explode in a burst of energy while annihilating each other.

Coming round to the theory of everything where all particles in the final theory must have an antimatter counterpart and matter and antimatter destroy each other when collide, the universe wouldn’t have matter to create stars, planets, species, etc. since it is predicted that Big Bang have created equal amount of matter and antimatter. In order for that to occur, there must be the presence of an extra matter that is left to create the elements of the universe. However, this violates the Standard Model of Antimatter, which states- for every particle there is an antiparticle present. And hence, research is still going on on this theory.

The origin of the term Antimatter dates back to 1898, when  Arthur Schuster, a German Physicist, coined it in two of his whimsical letters to Nature speculating about negative matter.

“The atom and the anti-atom may enter into chemical combination, because at small distances molecular forces would overpower gravitational repulsions. Large tracts of space might thus be filled unknown to us with a substance in which gravity is practically non-existent, until by some accidental cause, such as a meteorite flying through it, unstable equilibrium is established, the matter collecting on one side, the anti-matter on the other until two worlds are formed, separating from each other, never to unite again. Matter and anti-matter may further coexist in bodies of small mass. Such compound mixtures flying hither and thither though space, coming during their journey into the sphere of influence of our sun, would exhibit a curious phenomenon. The matter circulating in a comet's orbit, the anti-matter repelled and thrown back into space, forming an appendage which is always directed away from the sun.”

The above is an extract from one of his letters where he mentioned about antimatter.

Later in 1928, Paul Dirac, a British Mathematician and Physicist, indicated the existence of a positively charged electron- positron, with the help of his new equation.

When Schrödinger’s equation started showing limitations with respect to Einstein’s Special Theory of Relativity, Dirac was set to find an equation that was compatible to Einstein’s Special Theory of Relativity to describe the quantum waves of probability spreading through space.

His equation indeed was significant in quantum physics since it discovered the spinning properties of an electron. However, along with that Dirac noticed a duplicacy in the machinery. Along with the negatively charged particle, he observed a particle with the same mass as an electron but with a positive charge. However, at that time a lot of other scientists claimed the equation to be wrong due to the emergence of an unknown particle which led to strange confusion.

It was then in 1932 that, Carl Anderson, an American physicist, who was trying to study cosmic rays at that time, discovered something similar. In order to measure the energy of the ejected electrons by smashing the rays into atoms in the atmosphere, he used an extremely strong magnetic field to bend the electrons and deduced that if they had high energy and moved fast, they would bend less sharply to escape the vicinity of the magnetic field. Later when he observed the photographic plates of his ‘cloud chambers’ he found traces of paths that were bent in an opposite direction to that of those electrons in the magnetic field by particles having the same mass as that of electrons. Although Anderson knew nothing about Dirac’s equation earlier, later he found out about it, and Dirac’s equation was proven right. With this, he called the particle- Positron.

Seems like we have reached the end of the first episode of  Antimatter Unraveled. Hope you liked reading the blog so far and got the chance to weave your interest in Antimatter.

Want to know about the CP violation and the asymmetry in processes producing matter and antimatter? Stay tuned for the upcoming episode of this series!

Sources:

• Office of High Energy Sources 

• The One Thing You Need To Know- Marcus Chown

• Etymology

• The God Equation- Michio Kaku

• Picture Courtesy: Pinterest