Antimatter is real and is defined as particles with quantum properties opposite to those of matter. For example, an antielectron, or positron, has a positive charge compared to the electron's negative charge. When matter and antimatter particles meet, they annihilate each other.

When antimatter and matter annihilate, they convert their entire mass into pure energy, as described by Einstein's E=mc². This process is incredibly efficient, producing a massive amount of energy from a small amount of mass due to the speed of light squared factor. This differs from nuclear reactions, which only convert a small percentage of mass into energy.

Every particle in the universe has a corresponding antiparticle. Even neutral particles like neutrons have antineutrons, made of antiquarks, which have opposite fractional charges to their quark counterparts. This implies the existence of a complete 'opposite world' of antimatter particles.

Matter and antimatter can be spontaneously created from sufficiently energetic photons (light). This process always creates a matter-antimatter pair (e.g., an electron and a positron) to conserve fundamental properties like charge. The new particles move in opposite directions to conserve momentum.

In the early, hot universe, energy constantly created matter-antimatter pairs, which then annihilated back into energy. If the universe had behaved symmetrically, all matter and antimatter would have annihilated, leaving only a universe of light. However, we observe a universe filled with matter.

The existence of matter in our universe suggests a slight asymmetry in the early universe, where for every 100 million matter-antimatter pairs that annihilated, one matter particle was left over. This fundamental imbalance, often called 'symmetry breaking,' is not fully understood by science but resulted in everything we see today.

Scientists question whether antimatter galaxies exist. However, observations of colliding galaxies show no evidence of annihilation, suggesting our universe is predominantly matter-based. This leads to speculative theories about whether the missing antimatter could reside in entirely separate universes.

Antimatter continues to be a subject of cutting-edge research, with recent discoveries like the heaviest antimatter hypernucleus pushing the boundaries of scientific understanding. The study of antimatter encourages critical thinking and challenges established paradigms, fueling scientific and societal progress.