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Antimatter is matter made up of antiparticles . Anti- atoms have atomic shells made of positrons and atomic nuclei made of antiprotons and possibly antineutrons .

Anti-atoms and anti-molecules are unknown in nature and can only be produced through complex experiments. In contrast, light anti- particles arise in nature from cosmic radiation and during beta-plus decay . There are also short-lived exotic atoms like positronium made up of one electron and one positron, and molecules like di-positronium made up of two positronium atoms .

Antiparticles and also anti-atoms can be generated in pairing reactions using particle accelerators . Positrons can be obtained with little effort by producing beta-plus-active radionuclides . This positron radiation enables the important real-time imaging process of positron emission tomography (PET) in modern medical technology .

When a matter particle and its antiparticle collide, they can “annihilate” in an annihilation reaction. The entire energy contained in the particle reappears in a different form, and u. Other particles may arise.


In 1898 the physicist Arthur Schuster first used the term antimatter in two letters to Nature . He speculated about star systems made of antimatter, which would be indistinguishable from our matter by observation. Karl Pearson in 1892 and William Mitchinson Hicks in the 1880s had already spoken of possible “negative matter”.

In 1928 Paul Dirac set up the Dirac equation based on the work of Wolfgang Pauli , a relativistic first-order wave equation for the description of the electron based on the special theory of relativity . Based on this equation, Dirac predicted the existence of the positron as an antiparticle to the electron. Put simply, in the so-called Dirac picture of quantum field theory, the vacuum consists of a Dirac lake filled to the brim with electrons. An electron-positron pair created by pair creation consists of the electron that was removed from this Dirac Sea by excitation (i.e. energy supply) and the “hole” left behind, which represents the positron. Today, according to the Feynman-Stückelberg interpretation, the states of negative energy are interpreted as production operators for antiparticles of positive energy, which has made the Dirac lake unnecessary.

In 1932, the positron was the first antiparticle to be detected in cosmic rays by Carl David Anderson . Also antimuons generated by cosmic rays, if it penetrates into the earth's atmosphere.

The antiproton was detected in experiments at the Bevatron particle accelerator in 1955 , and the antineutron in 1956.

In 1995, a working group under Walter Oelert from Forschungszentrum Jülich was the first to detect some anti-hydrogen atoms on the Low Energy Antiproton Ring (LEAR) at CERN, i.e. bound systems made up of an antiproton and a positron. In the following two years, researchers at Fermilab in the USA repeated the experiment.

At the end of 2009, the Fermi space telescope surprisingly discovered positrons during thunderstorms ; the telescope should really only be used to search for gamma rays.

In 2010, 38 anti-hydrogen atoms were detected at CERN in the ALPHA project , which were trapped in a magnetic trap for 172 milliseconds . However, significantly larger amounts are required for a spectroscopic examination. In 2016, the follow-up experiment ALPHA-2 finally succeeded in analyzing the 1s – 2s transition using laser spectroscopy . As predicted by the CPT theorem, the spectral lines of hydrogen and anti-hydrogen agree to an accuracy of 2 · 10 −10 .

In April 2011, CERN succeeded in capturing 309 anti-hydrogen atoms at a temperature of around one Kelvin for almost 17 minutes, 5800 times as long as in November 2010. This is widely viewed by CERN researchers and commentators as a major breakthrough opens up new opportunities to research the properties of antimatter. This involves, for example, possible violations of symmetries in particle physics . This concerns the question of why more matter than antimatter arose after the Big Bang.

The heaviest anti-matter atomic nucleus observed so far was the anti- 4 He generated at the Relativistic Heavy Ion Collider in April 2011 .

Energy balance in reactions

The annihilation releases the energy stored as mass during the pair formation . In electron-positron annihilation, this occurs as electromagnetic radiation , in the case of heavy particles (proton-antiproton) sometimes also in the form of other particles with high kinetic energy. The entire mass of the particle-antiparticle pair is converted and not just a small fraction , as is the case with nuclear fission and nuclear fusion (see mass defect ). Annihilation of a given mass of 50% matter + 50% antimatter would release much more energy than the reaction of an equal mass of fusion reactor fuel. For example, the annihilation of a hydrogen atom with an anti-hydrogen atom would yield the energy 1.88 GeV ; the fusion of a deuterium nucleus with a tritium nucleus , on the other hand, provides only 17.6 MeV, i.e. about one hundredth.

Because of this high storage effect for energy, the use of antimatter (in the form of positrons) for weapons purposes has been considered. In space travel, the potential benefits for drive systems have been discussed several times . Scientists at Pennsylvania State University investigated theoretical concepts in the AIMStar and ICAN-II projects in the 1990s. So far, however, there is no realistic concept of how sufficient amounts of antimatter could be produced, stored and transported for such technical purposes.

Antimatter can never be an energy resource , because it does not exist in exploitable form in the universe, and its artificial production always requires at least as much energy as could be obtained from it.

Antimatter in the universe

The previous experiments and theories show largely identical behavior of matter and antimatter (see CP violation ). According to this, after the hot and dense initial state of the universe , the Big Bang , matter and antimatter were created in approximately equal amounts and shortly afterwards "annihilated" again.

On the other hand, all previous observations in the cosmos only show "normal" matter. It must be the remnant of a minor imbalance at the beginning of the universe. Earlier assumptions that the universe was filled with matter in some areas and antimatter in others are now considered unlikely. So far, no annihilation radiation, which should arise in the border areas, has been detected. The direct search for anti-helium atomic nuclei in cosmic rays , which was carried out in 1998 with an alpha magnetic spectrometer on board a space shuttle , remained inconclusive: around three million helium nuclei were detected, but not a single ancient nucleus was found.

The comparison of model calculations within the framework of the Big Bang theory and astronomical measurement data ( primordial nucleosynthesis , WMAP ) suggests that the ratio of matter and antimatter was initially almost 1 to 1. A tiny imbalance - about 1 particle excess for 1 billion particle-antiparticle pairs - resulted in a remnant of matter remaining, which is detectable in our universe today. This imbalance between matter and antimatter is one of the prerequisites for the stability of the universe and thus also for life on earth. If in perfect equilibrium, matter and antimatter would have been completely converted into radiation as the universe cooled down.

The reason for this imbalance is one of the great puzzles of elementary particle physics and cosmology ; It is assumed that only unifying theories (e.g. string theory , M-theory , supersymmetry ) will explain this unequal distribution satisfactorily. One of the prerequisites for a preponderance of matter is the CP violation (see baryogenesis ). This was first discovered in kaons in the 1960s. In the 1990s, 200 million B-meson- anti-B-meson pairs were generated at SLAC in the USA and investigated how they disintegrate again. During the evaluation it was found that the B mesons decay into a pion and a kaon about twice less often than their antiparticles. In the kaon system studied earlier, the difference was four to a million.

Antimatter in science fiction

Antimatter appears in many novels and films where its physical properties can differ from the real ones. In the world of Star Trek , a matter-antimatter reaction serves as an energy source for the fictitious warp drive to accelerate it to faster than light and also as a weapon. In the pulp novel series Perry Rhodan antimatter used varied by about gravity - shock waves radiate and to deliver a message, but above all as a basis for advanced weapon systems and power generation. In the novel Angels & Demons by Dan Brown fictional scientists have made CERN visible amounts of the substance and stored long-term in a magnetic trap.


Web links

Wiktionary: Antimatter  - explanations of meanings, word origins, synonyms, translations

Individual evidence

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