antimatter in physics and chemistry

What is Antimatter?

This baryonic matter that is so well known to us, at its most basic scale, is composed of quarks and usually accompanied by leptons.

Leptons (such as electrons or neutrino) are subatomic particles that are subject to electromagnetism, gravity, and weak interaction, but not strong interaction (which is the strongest force in the universe, laying the lapse). This means that they have mass and spin and some have an electric charge, but none have a chromatic charge. The most important to constitute the matter we know is the electron, which has a very small but real mass, a negative electrical charge and spin 1/2.

Quarks are subject to all four forces, including strong, and therefore can present mass, spin, electrical charge and chromatic charge. This universe serves them in six flavours, which we call up, down, charm, stranger, top and bottom. For the formation of baryonic matter, the most relevant are the first two, as they make up the protons and neutrons. Both are made up of three quarks. The proton, for two ups and one down. The neutron, two down and one up.

Read more: How are the String theories related?

Reverse matter

Antimatter is simply a matter where some of the loads are invested with respect to ordinary matter. Let’s see it with an electron, which is understood very well. The electron, as a lepton it is, has mass and spin but only one charge: electric, always negative. Its antiparticle, called a positron, possesses exactly the same mass, spin and electrical charge; however, in this case, the electrical charge is positive.

Interactions Between Loads Of The Same And Different Nature

In this way, the position maintains all the properties of its antiparticle the electron but electromagnetically reacts upside down. For example, two electrons, because they have negative charges, tend to repel each other. But an electron and a positron, even if everything else is identical, tend to attract each other because one has a negative electrical charge and the other positive. And so with everything.

Example of a Neutron’s Color Structure. You Can See The Composition Of Quarks And The Color Load It Adopts.

The same thing happens with quarks. The quark above, for example, has an electrical charge of +2/3 (two-thirds of that of a positron). Antiarriba, on the other hand, has an electric charge of -2/3 (two-thirds of that of an electron). Its colour load also changes: if for example, it is in a red state, the antiquark will be in anti-red, which is often called magenta. (Don’t be confused by this colour thing: it’s a symbolic way to represent its state in the face of quantum chromodynamics; it has nothing to do with true colours.)

Let’s see what happens then with a proton and an antiproton; for example, with regard to electromagnetism, which is simpler. We have agreed that the protons (like all baryons) are composed of three quarks and that in their case these are two up and one down. The quark above carries an electrical charge of +2/3 and the quark below, another of –1/3. Let’s add them up: (+2/3) + (+2/3) + (–1/3) + 3/3 s +1. Result: the proton has a positive charge.

Now let’s look at the antiproton, consisting of two antiquarks above (load –2/3) and an antiquark down (load +1/3). Notice that it is formed exactly the same, only with the reversed versions of the quarks. Let’s sum (–2/3) + (–2/3) + (+1/3) – –3/3 – –1. Result: The antiproton has a negative charge.

All other loads are also reversed. In those leptons that have no electrical charge (neutrinos) a different property is reversed, helicity, which is the projection of the spin relative to the moment of inertia. Or, alternatively, they may be Majorana particles and constitute their own antiparticle. But let’s not get in the way at the moment.

So let’s imagine an atom, the most basic of all: hydrogen-1 or protio (current hydrogen). It consists of a proton (positive electrical charge) and an electron (negative electrical charge) in orbit around it. This configuration is possible because the proton and electron, having different loads, tend to attract (just as gravity does with a spacecraft orbiting a planet).

If we replace the electron with its antiparticle, the positron, or the proton with an antiproton, this atom becomes impossible: both would have the same load, repel each other violently and leave each on their side.

But if we replace the two – the electron and the proton – with a positron and an antiproton, the atom is equally possible because the relationships between the two are maintained; only now they’re inverted. 

Now the positive charge is in the orbiting positron and the negative is found in the antiproton of the nucleus, but as the relationship between the two remains (inverted loads), the atom can exist. And it’s called antihydrogen. Not only can it exist, but we’ve made a little bit. CERN (yes, the same as the LHC) was the first to achieve this, probably in 1995 and verified from 2002 in its particle accelerators.

small number of anti-deterio (antihydrogen-2) and anti helium-3 nuclei have also been created in the accelerators. We’re talking, in any case, about figures of one billionths of a gram. With the technology present, its cost would be as exorbitant as its rarity: approximately 50 billion euros per gram of antihydrogen.

But it’s not all that hard. For example, there have been technological applications based on antimatter for some years, such as positron emission tomography (PET) for widespread use in modern medicine.

Matter-antimatter annihilation and the problem of containment

Unfortunately, no effective method of containing anti-atoms is yet known without them coming into contact with the surrounding matter. Charged particles – positrons and ions or loose cores, for example – can be kept for some time in magnetic traps, such as Penning traps. The atoms, on the other hand, end up coming into contact with the surrounding matter and annihilate each other.

Much has been said about the matter-antimatter annihilation: the most energetic reaction in the universe, in which both masses disappear completely to release the energy that forms them according to the famous equation E= mc2. It is absolutely real and actually occurs constantly around us, every time a natural antiparticle comes into contact with ordinary matter (e.g. in the Earth’s atmosphere).

What happens is that their charges –electromagnetic, chromatic or of whatever type– cancel each other out. Suppose an electron and a positron, because they have opposite electrical charges, they tend to attract and eventually collapse with each other, resulting in a particle twice as massive as an electron (or a positron) and zero charged. 

However, such a particle is outside the stability ranges of matter: it cannot exist in this universe. It is dead matter, so to speak, even before it happens. So they change to a more basic state: they lose their mass and it is transformed entirely into energy. 

The result is usually two gamma rays (composed of photons, lacking charge and effective mass) that retain their linear and angular momentum, as well as the total energy (by the principle of conservation of matter and energy). In short: that its matter has been completely transformed into energy, in the form of gamma radiation.

The same thing happens to a proton and an antiproton: they transform into gamma rays and a neutral pion. But the neutral pion is highly unstable and decays in a bi-millionth of a second to transform into two gamma rays (or, sometimes, an electron-positron pair). The neutron and antineutron also become a pair of gamma rays, but with terrifying energy. 

In short: the encounter between matter and antimatter produces energy in the most optimal way possible in this universe, in the form of radiation and in turn leading to the disappearance of the preceding mass. This is the much vaunted matter-antimatter annihilation.

Antimatter in the cosmos

The discovery of antimatter is derived from early studies on quantum mechanics in the early 20th century. The first serious proposal in this regard was made by Paul Dirac in 1928, elaborated on the relativistic version of Schrodinger’s quantum wave equation for the electron, which led him to theoretically conclude that there could be anti-electrons (positrons).

They are Nobel Laureates for these things: Carl Anderson proved his real existence in 1932 and Dirac took the Nobel Prize in Physics, in 1933, for this and other things as postulating much of modern atomic theory (Anderson was also awarded, in 1936). He also wrote Principles of Quantum Mechanics, in 1930, a magna work that marked a before and after in our understanding of reality.

https://videos.cern.ch/record/1065975

Dirac, an extremely humble and atheist genius like himself, who has been said to suffer from a certain degree of autism (although it may have been simply a very taciturn character) theorized more things about antimatter. According to their equations, validated beyond all doubt by the material discovery of the positron and the other antiparticles, each particle of this universe should be given an antiparticle… and should have annihilated each other at the beginning of everything, preventing the consolidation of matter.

In fact, according to the observations made – and at this point, we have looked very far – the amount of antimatter in the cosmos is much lower than that of matter; such a phenomenon is called baryonic asymmetry.

For many years this asymmetry has been one of the great unresolved problems in physics, and even today we only have some well-founded hypotheses about it. One possibility is that there are simply large amounts of antimatter beyond the limits of the currently observable universe; however, this speculation is unstopped and does not explain why such separation is due when matter and antimatter should attract each other. In general, it shows a violation of the cosmological principle. A more interesting hypothesis, nominated by Cronin and Fitch in 1964 (Nobel Prizes 1980) is the so-called cp symmetry violation; the Nobel is because this violation has been experimentally verified.

Symmetry C and P symmetry govern the way matter and antimatter can form. As early as the 1950s, some particles had been found not to strictly meet the parity that was supposed to all of them. Cronin and Fitch demonstrated that these symmetries occur under the action of all but one of the forces: weak interaction. 

This means that our universe, at least from very early times, is not exactly symmetrical but skewed towards matter versus antimatter (from where some multiverse proponents suggest the existence of at least another universe that favours antimatter versus matter). It is not the only asymmetry of our universe: the chirality of the cosmos is turned to the left in all its fields, from physics to biology (this usually becomes a political joke, but it is a fascinating phenomenon that we will talk about one day).

However, there appear to be large accumulations of antimatter within the observable universe. The European space observatory INTEGRAL has confirmed the existence of one of these near the centre of our own galaxy: an antimatter cloud that emits strong gamma radiation because it is annihilating positrons at a rate of 1.5 followed by 42 zeros every second. 

However, the proportion remains anomalously low and it is suspected that all or almost all of the antimatter existing in the current universe is recent, created in processes linked to matter.

This is an unanswered question, which is carefully considered because solving it would involve destroying one of the great obstacles to achieving a great unified theory.

Antigravity?

Some have speculated that the existence of antimatter would imply the existence of antigravity. However, this is not proven and all odds suggest it is the wrong idea. We know that matter gravitationally attracts antimatter as if it were ordinary matter, it does not repel it as it would be if we were faced with an antigravity phenomenon. The main reason is that antimatter reverses the load, but not the mass. In antimatter, mass is still mass, not anti-mass.

Although the reverse phenomenon has not yet been verified (gravitationally attract matter with antimatter), due to how weak the gravity and little antimatter we have managed to produce for their study, everything points to that matter and antimatter are also attracted by gravity as if both were ordinary matter (or antimatter).

Antimatter as a source (or accumulator) of energy.

It is certainly not practicable with present technology, but the matter and antimatter interaction has been evidently postulated many times as a source (or at least accumulator) of extraordinary energy (for both civilian and military use). 

These transformations of matter into energy by annihilation are the most energetic of the known universe, and are impressive.

Let’s take an example. Half a gram of matter interacting with half a gram of antimatter (one gram of total mass) spontaneously generates 89,876 gigajoules of energy (obtained by simply applying E = mc2; E – 0.001 299.792.4582 x 89,875,517,873,682 J). 

In terms of usable energy, this equates to about 25 gigawatts-hour (a nuclear power plant like Cofrentes pulling watts at full throttle for almost an entire day); if we want to present it in terms of explosive energy, it’s 21.5 kilotons: like Nagasaki more or less. With a single gram of material.

Compare military-grade uranium-235 can optimally produce 88.3 gigajoules per gram; the mixture normally used in civilian power plants, between half and three and a half. Under a thousand times less. The fusion of deuterium-tritium in thermonuclear weapons can reach 337 gigajoules per gram, and the most energetic fusion possible is over 650; that is, a hundred and peak times less.

Matter and antimatter annihilation have another advantage: unlike fusion, it occurs spontaneously in all energy ranges. Unlike fission, it occurs with any amount of matter and antimatter. 

This means that it would not present containment problems: the conceptual design of a matter-antimatter reactor would look a lot like that of a carburettor or, if you prefer, a rocket engine or a normal thermal power plant. If you need more energy you increase the flow a little, if you need less you reduce it, if you stop needing it you cut it. That’s all.

The problem we have seen before and it is essentially the usual one: there is currently no practical way to produce antimatter in industrial quantities; much less, to do so at an economically and energy-effective cost (much more energy is consumed to produce an antimatter atom than the resulting energy generated by the annihilation of that atom).

However, this is a real possibility if we were able to create a source of practicable antimatter. For this reason, and for everything else set out here, it is an extremely interesting field of research for theoretical physics. The European CERN has dedicated and dedicated great efforts in this area.

The study of antimatter – which already brought us enormous benefits as part of atomic and quantum theories, without which all the contemporary technologies we use on a daily basis would never have emerged – can give us immense knowledge about the profound nature of reality, the origin and evolution of the universe and new forms of energy production that we can now only dream of; not to mention their medical and other applied sciences.

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Recommended books:

1. Antimatter (Oxford Landmark Science)

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2. Matter, Dark Matter, and Anti-Matter: In Search of the Hidden Universe

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3. Story Of Antimatter, The: Matter’s Vanished Twin

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