Antimatter is at the heart of science fiction novels and shows such as Star Trek, but in reality, its existence in our universe is not fiction at all. As its name implies, this substance is the opposite of matter and was discovered in the first half of the 20th century. It continues to intrigue physicists and science fiction fans alike.
Matter, the stuff that all physical things are composed of, is made of atoms that are themselves composed of particles such as protons, electrons, and neutrons. Similarly, antimatter contains antiparticles that are called antiprotons, positrons, and antineutrons, respectively. Particles and antiparticles have the same mass but opposite charges; for example, an electron is negatively charged and its opposite, the positron, is an electron with a positive charge. Antimatter is an umbrella term that refers to the culmination of these antiparticles.
When matter and antimatter come into contact with one another, they are both annihilated. This releases a large amount of energy. Very generally, the big bang theory of the creation of the universe involves the large scale encounter of matter and antimatter.
Antimatter is not significant on Earth unless it is created artificially in a physics laboratory or similar setting. Scientists have been able to create relatively small amounts in the form of antihydrogen. It briefly occurs naturally as a result of cosmic rays penetrating the atmosphere as well as the breakdown of radioactive materials. Within a matter of nanoseconds, antiparticles and particles meet and are destroyed, which is why antiparticles are not very common on Earth. In space, however, it is much more common and observable through the use of finely tuned instruments.
The ability to artificially create antimatter is very important in medical science, specifically in Positron Emission Tomography (PET) scans. A PET scan uses the byproducts of the annihilation of the electron and the positron — gamma photons — to test for and diagnose cancer. Antimatter is used in some other forms of radiation technology as well.
In theory, antimatter could be used as a renewable and completely efficient source of fuel. The time, effort, and cost of creating it, however, currently outweighs the benefit of the energy that it could potentially produce. In the future, when it is better understood, it may in fact become a plausible solution for our current energy crisis as it relates to environmental degradation.