Universe’s missing half: What is antimatter and why it matters

In 1930, theoretical physicist Paul Dirac was trying to reconcile quantum mechanics with Einstein’s theory of relativity when his equations hinted at something strange: the existence of a “mirror” particle identical to the electron, but with opposite charge. Its implications made him uneasy  — that every particle has an antiparticle, and that perhaps the whole of nature is constructed in this way. 

Dirac’s calculation wasn’t to be a mere mathematical quirk. Two years later, American particle physicist Carl Anderson found the positron, the electron’s antimatter twin, in cosmic ray experiments. It was a moment of rare scientific poetry: a particle predicted by pure mathematics, then seen in nature.

Antimatter sounds like something from science fiction. And indeed, it has captured the imagination of writers from Star Trek (where it powers warp drives) to Angels and Demons (where it threatens to obliterate Vatican City). But antimatter is very real, though vanishingly rare in our universe. Whenever a particle meets its antiparticle, they annihilate in a flash of energy — converting all their mass, as per Einstein’s , into pure light. That property makes antimatter the most energy-dense substance imaginable. A single gram could, in theory, produce as much energy as a nuclear bomb.