【Selected Readings】

As peculiar as antimatter may sound, if you come across a piece of antimatter, it won't make any difference to matter. Even individual atoms of matter and antimatter cannot be distinguished. It is only inside the atoms that their true nature is apparent.

Inside the atoms of matter – the matter that makes up everything – are electrons that revolve around the central nucleus. The hydrogen atom is the simplest element and consists of a nucleus made up of an electron and a proton. Electrons have a negative charge, while protons have a positive charge. The opposite charges attract each other, keeping the atoms together.

The antihydrogen atom is the same, but the charge is reversed. The negatively charged "antiproton" in the center grabs the positively charged "antielectron", also known as the "positron". The attraction of force at the positive and negative electrodes is the same, so the electromagnetic force that turns an atom into a molecule should also apply to the antiatom.

When a particle encounters its antiparticle twin, they annihilate each other in an instant. This destruction isn't just a sci-fi plot. Some radioactive substances naturally release positrons. In fact, positron annihilation has been used in medical diagnosis for decades in the form of PET (positron emission tomography) scanners found in hospitals.

But why is there matter in the universe and not nothing when the laws of physics imply that the energy of the Big Bang should condense into matter and antimatter equally? They were supposed to destroy each other.

But is this theory correct? It was tested in the 90s of the 20th century by annihilating electrons and positrons in a particle accelerator. They accelerate at nearly the speed of light and collide head-on. The resulting flash of energy, in a region smaller than a single nucleus, resembles the situation shortly after the birth of the universe.

By recording the results of these "small explosions", experiments confirmed that energy can be transformed into equilibrium particles and antiparticles. It reinforces the idea that matter and antimatter emerge in perfect equilibrium. So where is the missing antimatter?

Solving this puzzle requires the study of antimatter atoms. If the positron happens to be captured by the electric field of the antiproton, there will be an antihydrogen atom. It has no net charge, but it reacts to a magnetic field. But how do you preserve a substance that can destroy anything it touches?

First of all, you need a very good vacuum environment so that antimatter doesn't inadvertently hit free atoms in the air. Then you need to keep it away from your container, as these are also made of matter. The solution is a "magnetic bottle" that uses electric and magnetic fields to trap antimatter.

However, to study antihydrogen atoms, you first need to make and store a large number of atoms. The challenge now is to get the positrons and antiprotons close enough to give their electrical attraction a chance to trap them, forming an antihydrogen atom before they are annihilated by ordinary matter.

This has already been done at CERN, by slowing down the antiprotons in a machine called AD (Antiproton Reducer). Then the electromagnetic force and positrons bring them together. Since 2009, Alpha has trapped atoms in magnetic bottles hundreds of times.

In 2011, CERN's Alpha experiment succeeded in creating an antihydrogen atom (the antimatter equivalent of hydrogen) and storing it for nearly 17 minutes. The following year, scientists changed the direction of the magnetic field of the antiatoms and irradiated them with microwaves. This suggests that it is possible to measure their properties in more detail.

In January 2014, scientists at CERN created a beam of antihydrogen atoms and found 80 antimatter atoms in the beam. This is one step closer to unraveling the mystery of antimatter, as a large number of antihydrogen atoms are needed to collect enough data to answer big questions.

Scientists will study the atomic spectrum — a pattern of colored lines that resemble a barcode. The behavior of the positrons in the antihydrogen atom is predicted to be exactly the same as the electrons in the hydrogen atom, so their atomic "barcode" should be the same.

If there is any difference in their atomic "barcodes", we will find the difference between matter and antimatter, although scientists will still have to figure out what that means. When they do, we may be closer to solving the mystery of missing antimatter, and the question of why there is something and not nothing.

So far, CERN scientists have managed to store several hundred antimatter atoms. If they can do more, the possibilities are far-reaching. Just one gram of antimatter could be used to propel a spacecraft to Mars or create a bomb equivalent to the Hiroshima atomic bomb.

However, science may prevent this application. With current technology, it takes 10 billion years to produce one gram, and 1 billion bottles to store it requires at least the energy you recycle. Perhaps, the world would be a better place if a small amount of antimatter was safely stored.

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