For every particle in the universe, physicists believe that there should exist an antiparticle with the same mass, but the opposite charge. When a particle and an antiparticle meet, they annihilate one another and are transformed into pure energy. Looking around, though, it's obvious that most of the antimatter has disappeared and the universe has not been annihilated into pure energy. Although antimatter has been observed in nature, it occurs in far smaller quantities than its twin, which begs one of the most perplexing questions in physics: where did all the antiparticles go? Or to put it another way: why do we exist?

Read more at motherboard.vice.com