Each particle has its matching antiparticle. When the two collide, they annihilate each other—in the process creating energy that is then emitted into the universe.
Anti-particle Term Timeline in A Brief History of Time
The timeline below shows where the term Anti-particle appears in A Brief History of Time. The colored dots and icons indicate which themes are associated with that appearance.
...can also create unstable particles, such as mesons, which are made when quarks join with antiquarks. These fit the no color rule (they are white, e.g. because a red particle joins... (full context)
...reverse process—the production of quarks and protons. If there were regions of anti-matter (made of anti-particles), there would be a lot of radiation given off at the border with other regions,... (full context)
...universe expands and cools, forces that do not obey the symmetry of T cause more anti-electrons to become quarks than electrons to become anti-quarks, creating the matter we see today. Of... (full context)
...the universe would have been made up of photons, electrons, and neutrinos, along with their anti-particles, and some protons and neutrons. As the universe cooled, electron and anti-electron pairs would annihilate... (full context)
...C, P, and T symmetries, a particle going backward in time could be considered an anti-particle going forward in time. For example, black holes “emit” particles, where one component of a... (full context)