Antimatter has created a vast area of study for particle physicists. It was one of the most exciting discoveries in physics of the XXth century. Even if many people think that this type of matter belongs to science-fiction, antimatter is produced on Earth every day. However, to understand what is antimatter, we first have to understand what is matter.
Composition of matter
The atoms that exist in our universe are formed by a variety of particles (electrons, quarks up and quarks down). Grouping themselves in different ways and quantities, these fundamental particles (that to say, they can’t be divided into more particles) are the ones that form the different chemical elements.
For example, hydrogen, the simplest element in the universe, is formed by a proton (formed by two quarks up and one quark down) and an electron around it. However, helium is formed by two protons, two neutrons (formed by two quarks down and one quark up) and two electrons orbiting them.
What is antimatter?
If the matter is formed by particles, antimatter is formed by antiparticles. As we will see later on, these antiparticles were predicted by the British physicist Paul Dirac, and have the characteristic of having an opposite electric charge to the “normal” particles.
Every particle of matter (such as the electron) has an associated antiparticle. In the case of the electron, which has a negative charge, its antiparticle is called positron (which has a positive electric charge). Moreover, when an antiparticle makes contact with a particle, they annihilate each other, converting 100% of their mass into pure energy.
It is for this reason that antimatter is not very abundant in our universe, as, in an instant, antimatter particles collide with matter and it disappears, leaving in the process pure energy.
Where is antimatter created?
As I previously said, antimatter is produced on Earth and in many other places of the universe every day. For example, a banana produced a positron every 75 minutes, there is evidence that positrons are also produced in electric storms, and antiparticles are also created when cosmic rays impact the Earth’s atmosphere.
As we can see, antimatter can be formed in a natural way. However, thanks to the technological advances of the last years, physicists have been capable of producing antiparticles, and even anti-atoms.
The Large Hadron Collider (LHC) has produced antiparticles at near-light speeds. In addition, anti-hydrogen atoms have also been produced (a positron orbiting an antiproton). The most complex antimatter element that has been created was the anti-helium.
This enormous difficulty to produce antimatter makes its price to be very elevated: with the current production techniques, a milligram of antimatter would cost about 61.2 billion dollars.