Antimatter is matter composed of antiparticles, particles with same mass but with opposite electric charges hence magnetic moment. They are among the most well known type of matter besides ordinary matter.
Notation and Nomenclature[]
Antimatter is named by adding the prefix anti- to the name of the ordinary matter
e.g. Antihydrogen
Due to historical reasons, some antimatter has their own names, for example the positron
Some neutral particles such as the photon, graviton, leviton and some WIMPS are antiparticles of themselves (majorana particle) Other neutral particles such as neutrinos has antiparticle counterparts because they annihilate when collide together
One convention for writing antimatter is to add a bar to the symbol of the antiparticle (this also applies when one express a composite particle into its constituent elementray antiparticles), for example:
a and uud
Another convention is to distinguish the particles by their electric charges, for example:
e- (electron) e+ (positron)
To prevent confusion, the two conventions are never mixed
Origin[]
Antimatter is created anywhere with energetic particle collision events, for example
- Cosmic rays impacting planetary atmospheres or other ordinary matter objects
- At the center of galaxies
Antimatter is also produced/found naturally via
- β decay of naturally occurring radioisotopes
- Inside thunderclouds (where electrons were accelerated by the electric fields in the clouds to high energies and the resulting positrons are produced by gamma ray photons interacting in pair production)
- Van Allen radiation belt of planets and planetoids
Properties[]
Antimatter is basically identical to ordinary matter in their interactions, except for a few
Symmetry[]
- Strong interaction (though some physicists suggest otherwise after checking the maths, however no experimental evidence of strong CP violation has been discovered in the 21st century)
- Electromagnetism
- Gravity
- Time
- Translation and rotation
Asymmetry[]
- Weak interaction (At least in the case of B mesons and Kaons, both particles oscillate between their ordinary and antimatter counterparts and has a preference for the matter counterpart)
- Levity (Levity is attractive to antimatter but repulsive to matter)
There is an abundance of matter than antimatter in the earth domain of the Standard universe (while there is an abundance of antimatter than matter in other domains), which is an unsolved problem in physics, although CP violation may account for a small fraction of this phenomenon.
Annihilation[]
One of the major interaction between matter and antimatter is annihilation (means to make into nothing). However in order for annihilation to occur it must satisfy a number of criteria:
- Conservation of energy
- Conservation of momentum (both linear and angular)
- All sets of quantum numbers must respectively add to zero (Electric charge(Q) is an example of a quantum number)
For example, an electron cannot annihilate with an antimuon as their flavour quantum numbers does not sum to zero (Any pair of particles that cannot annihilate will bounce away from each other without losing energy)
Due to the conservation of energy and both particles and antiparticles have positive masses , they never annihilate to nothing, but produce products depend on the initial energy of the collision. Due to the huge rest mass energy released as the mass of the particles converted into other forms of energy, annihilation is an explosively exothermic reaction
The opposite of annihilation is pair production
Low energy annihilation[]
Typical[]
When the particle-antiparticle pair possess little kinetic energy and/or are light, a pair of gamma ray photons each with half the total energy of the particle pairs are usually produced
For example in a electron-positron annihilation:
e- + e+ → γ + γ
Two gamma ray photons will be produced travelling in opposite direction (as at the instant of collision, both particles are momentarily at rest, thus the opposite travelling photons allows the momentum to sum to zero hence conserving momentum), or in a fork pattern (if it is a sideway collision which there is net momentum in the system)
(In the above example, electrons has a electron number of +1 while that of the positron has -1. Therefore both their electric charges and lepton numbers sum to zero thus the annihilation is permitted)
More photons are also possible to be generated but their probability decreases with increasing number of photons
Production of some light particle-antiparticle pairs (e.g. neutrinos and antineutrinos) are also possible but extremely unlikely
Single photon annihilation[]
Single photon production are usually forbidden in annihilation as they always possess net momentum, thus violating conservation of momentum. In order for such type of annihilation to happen, it must take place near another particle (e.g. a nucleus). The neighboring particle will then travel opposite to the direction of the single photon (i.e. carry away the excess momentum) thus the total momentum sums to zero.
The reverse process (pair production by a single photon) also obeys the above mechanism.
High energy annihilation[]
When the particle-antiparticle pair possess a huge amount of kinetic energy and/or are massive enough, the total mass-energy is sufficient to produce other heavy particle-antiparticle pairs. Photons and other light particles are also possible to be produced but will possess higher energies
Artificial production/Collection[]
Various methods are used to produce/collect antimatter
- Irradiating a millimeter thick gold foil with an intense laser pulse→make positrons
- Particle accelerators→make heavier antimatter such as antihydrogen
- Trapping positron produced by β decay of radioisotopes→make positron and antihydrogen
- Magnetic scoops used in the Van Allen Belt of planets
Storage[]
Human[]
- Penning trap (Usuing a combination of magnetic and electric fields in a bottle to contain charged antiparticles)
- Magnetic traps (Use magnetic fields to confine antiatoms in a region)
- Magneto-optical trap (Use a combination of magnetic fields and lasers to trap neutral particles)
Lodorian[]
- Same as above
- Monopole matter bottles for containing ordinary antimatter and ordinary biodegradable plastic for antimonopole matter (monopoles have different quantum numbers to the ordinary nucleons and leptons thus they cannot annihilate with each other)
- Physics fields generator bottles where antimatter does not annihilate with matter
Applications[]
Antimatter has a broad range of applications:
Medical[]
- Positron emission tomography (A positron emitting radionuclide is introduced into the body on a biomolecule of interest. The positrons then decelerates until it is slow enough to annihilate with the electrons of the body to produced a pair of gamma ray photons which will be detected by the scanning device. Antimatter lifeforms have analogous technology known as electron emission tomography, in which an electron emitting radioantinuclide is used instead)
- Antihydrogen had shown potential for treating cancers
Fuel and Energy source[]
Human[]
The breakthrough in the mining of the Van Allen belt of planets and space exploration, the efficiency of particle accelerators and the technology for antimatter storage of humans allows antimatter (usually antihydrogen) to be used efficiently and economically
- Medium source of energy (as 74% of the energy is lost as neutrinos and a small fraction of gamma rays cannot be converted into heat)
- Propulsion fuel for interplanetary and interstellar travel (as 46.8 petajoules of energy (minus the energy lost as neutrinos) is produced for each 1kg matter and 1kg antimatter)
Lodorians[]
The mastery in the technology of creating physics fields allows Lodorians to capture the energy lost in gamma rays and neutrinos by forcing the neutrinos to decay into other particles within the fields and then converting their kinectic energy into other useful forms, thus achieving 100% efficiency. Their energy applications are similar to that of humans.
Military[]
- Main article: Antimatter weapon
Due to the huge amount of energy released in annihilation and their economy, antimatter is used in various types of explosives and fusion weapons