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Cosmic ray

cosmic rayscosmic radiationcosmic-ray
Minuscule numbers of antiparticles are generated daily at particle accelerators – total production has been only a few nanograms – and in natural processes like cosmic ray collisions and some types of radioactive decay, but only a tiny fraction of these have successfully been bound together in experiments to form anti-atoms.
A very small fraction are stable particles of antimatter, such as positrons or antiprotons.

Antihydrogen

anti-Hydrogenantihydrogen atomantihydrogen atoms
For example, a positron (the antiparticle of the electron) and an antiproton (the antiparticle of the proton) can form an antihydrogen atom.
Antihydrogen () is the antimatter counterpart of hydrogen.

Baryon asymmetry

matter-antimatter asymmetrymatter–antimatter asymmetryantimatter is rare in our universe
This asymmetry of matter and antimatter in the visible universe is one of the great unsolved problems in physics.
In physics, the baryon asymmetry problem, also known as the matter asymmetry problem or the matter-antimatter asymmetry problem, is the observed imbalance in baryonic matter (the type of matter experienced in everyday life) and antibaryonic matter in the observable universe.

Paul Dirac

DiracPaul Adrien Maurice DiracP. A. M. Dirac
The modern theory of antimatter began in 1928, with a paper by Paul Dirac.
Among other discoveries, he formulated the Dirac equation which describes the behaviour of fermions and predicted the existence of antimatter.

Positron

positronsantielectrone +
For example, a positron (the antiparticle of the electron) and an antiproton (the antiparticle of the proton) can form an antihydrogen atom. Dirac realised that his relativistic version of the Schrödinger wave equation for electrons predicted the possibility of antielectrons.
The positron or antielectron is the antiparticle or the antimatter counterpart of the electron.

Ionizing radiation

ionising radiationradiationnuclear radiation
The majority of the total energy of annihilation emerges in the form of ionizing radiation.
The positron or antielectron is the antiparticle or the antimatter counterpart of the electron.

Matter

corporealsubstancematerial
In modern physics, antimatter is defined as matter which is composed of the antiparticles (or "partners") of the corresponding particles of 'ordinary' matter (koinomatter).
This particular definition leads to matter being defined to include anything made of these antimatter particles as well as the ordinary quark and lepton, and thus also anything made of mesons, which are unstable particles made up of a quark and an antiquark.

Antiproton

antiprotonsanti-protonsantiparticle
For example, a positron (the antiparticle of the electron) and an antiproton (the antiparticle of the proton) can form an antihydrogen atom. In October 2017, scientists working on the BASE experiment at CERN reported a measurement of the antiproton magnetic moment to a precision of 1.5 parts per billion.
The questions of how matter is different from antimatter, and the relevance of antimatter in explaining how our universe survived the Big Bang, remain open problems—open, in part, due to the relative scarcity of antimatter in today's universe.

Dirac equation

Dirac particleDiracDirac mass
Dirac realised that his relativistic version of the Schrödinger wave equation for electrons predicted the possibility of antielectrons.
The equation also implied the existence of a new form of matter, antimatter, previously unsuspected and unobserved and which was experimentally confirmed several years later.

List of unsolved problems in physics

unsolved problems in physicsunsolved problem in physicsproblem
This asymmetry of matter and antimatter in the visible universe is one of the great unsolved problems in physics.

Antiparticle

antiparticlesanti-particleantiquark
In modern physics, antimatter is defined as matter which is composed of the antiparticles (or "partners") of the corresponding particles of 'ordinary' matter (koinomatter).
Otherwise, for each pair of antiparticle partners, one is designated as normal matter (the kind all matter usually interacted with is made of), and the other (usually given the prefix "anti-") as antimatter.

Quark

quarksantiquarkantiquarks
A proton is made up of quarks, so an antiproton must therefore be formed from antiquarks.
As with antimatter in general, antiquarks have the same mass, mean lifetime, and spin as their respective quarks, but the electric charge and other charges have the opposite sign.

Seetee Ship

and the science fiction term "seetee", as used in such novels as Seetee Ship.
Williamson's Seetee series is set in a future where space-dwelling miners attempt to harvest asteroids composed of CT or "contraterrene" matter (an obsolete term in physics) which today would be called antimatter.

Universe

physical worldThe Universeuniverses
Antiparticles are created everywhere in the universe where high-energy particle collisions take place.
The Universe appears to have much more matter than antimatter, an asymmetry possibly related to the CP violation.

Mass–energy equivalence

mass-energy equivalencemass-energyE=mc²
The amount of the released energy is usually proportional to the total mass of the collided matter and antimatter, in accordance with the mass–energy equivalence equation, E=mc 2.
One way to convert all the energy within matter into usable energy is to annihilate matter with antimatter.

Karl Pearson

PearsonPearson, KarlCarl Pearson
Between the 1880s and the 1890s, Karl Pearson proposed the existence of "squirts" and sinks of the flow of aether.
Pearson also discussed antimatter, the fourth dimension, and wrinkles in time.

Arthur Schuster

Sir Arthur SchusterSchusterSchuster, Arthur
The term antimatter was first used by Arthur Schuster in two rather whimsical letters to Nature in 1898, in which he coined the term.
Schuster is credited with coining the concept of antimatter in two letters to Nature in 1898.

Alpha Magnetic Spectrometer

AMS-02AMSAMS-01
Preliminary results from the presently operating Alpha Magnetic Spectrometer (AMS-02) on board the International Space Station show that positrons in the cosmic rays arrive with no directionality, and with energies that range from 10 GeV to 250 GeV.
The module is a detector that measures antimatter in cosmic rays; this information is needed to understand the formation of the Universe and search for evidence of dark matter.

PAMELA detector

PAMELAPayload for Antimatter Matter Exploration and Light-nuclei AstrophysicsPAMELA module
Antiprotons have also been found to exist in the Van Allen Belts around the Earth by the PAMELA module.
PAMELA was launched on 15 June 2006 and was the first satellite-based experiment dedicated to the detection of cosmic rays, with a particular focus on their antimatter component, in the form of positrons and antiprotons.

Baryogenesis

Sakharov conditionselectroweak baryogenesisasymmetry
The process by which this inequality between matter and antimatter particles developed is called baryogenesis. One of the necessary conditions for this asymmetry is the violation of CP symmetry, which has been experimentally observed in the weak interaction.
In physical cosmology, baryogenesis is the hypothetical physical process that took place during the early universe that produced baryonic asymmetry, i.e. the imbalance of matter (baryons) and antimatter (antibaryons) in the observed universe.

Anti-gravity

antigravityanti-gravitationalAnti-Grav
Schuster's ideas were not a serious theoretical proposal, merely speculation, and like the previous ideas, differed from the modern concept of antimatter in that it possessed negative gravity.
A longstanding question was whether or not these same equations applied to antimatter.

CP violation

CP-violationCP symmetryCP-symmetry
One of the necessary conditions for this asymmetry is the violation of CP symmetry, which has been experimentally observed in the weak interaction.
It plays an important role both in the attempts of cosmology to explain the dominance of matter over antimatter in the present Universe, and in the study of weak interactions in particle physics.

Particle accelerator

particle acceleratorsacceleratoraccelerators
Minuscule numbers of antiparticles are generated daily at particle accelerators – total production has been only a few nanograms – and in natural processes like cosmic ray collisions and some types of radioactive decay, but only a tiny fraction of these have successfully been bound together in experiments to form anti-atoms.
The Bevatron at Berkeley, completed in 1954, was specifically designed to accelerate protons to sufficient energy to create antiprotons, and verify the particle-antiparticle symmetry of nature, then only theorized.

International Space Station

ISSInternational Space Station (ISS)Space Station
Preliminary results from the presently operating Alpha Magnetic Spectrometer (AMS-02) on board the International Space Station show that positrons in the cosmic rays arrive with no directionality, and with energies that range from 10 GeV to 250 GeV.
Future plans are for the researchers aboard the ISS to examine aerosols, ozone, water vapour, and oxides in Earth's atmosphere, as well as cosmic rays, cosmic dust, antimatter, and dark matter in the universe.

CERN

European Organization for Nuclear ResearchEuropean Organization for Nuclear Research (CERN)European Laboratory for Particle Physics
In October 2017, scientists working on the BASE experiment at CERN reported a measurement of the antiproton magnetic moment to a precision of 1.5 parts per billion.