Is antimatter real, or just science fiction?

Antimatter has a name that sounds like it belongs in a spaceship engine. Yet the basic evidence comes from tracks in detectors, not from fiction. The simplest example is the positron. Dirac’s equation, combining quantum physics with relativity, suggested an electron partner; Anderson’s 1932 cloud-chamber track then supplied evidence for that positively charged particle. An electron carries negative electric charge. A positron carries positive charge and has the same mass. The word “anti” marks this relationship; it does not mean the particle is unreal or has negative mass.

A positron can meet an electron and take part in a process called annihilation. The original particles are replaced by other particles, such as photons, the particles of light. Energy is conserved. Nothing has vanished from the physical account. Some natural radioactive processes and collisions involving cosmic rays also produce antiparticles. They are not found only inside huge research machines.

Scientists have gone further and assembled anti-atoms. Antihydrogen contains an antiproton and a positron, in place of hydrogen’s proton and electron. Studying it lets researchers ask a sharp question: do matter and antimatter obey the same rules to the precision we can measure?

Two common pictures need care. Antimatter is not an invisible substance called dark matter. It has familiar interactions with light. And an antimatter apple would not be a black silhouette or a fruit that ages into yesterday. Such an apple is hypothetical, but ordinary-looking light and chemistry would be expected if it could exist away from normal matter. Nobody has made one.

The major mystery is not whether antimatter exists. It is why so little of it remains across the visible universe compared with matter. Keeping those questions apart matters. We can have strong evidence for an object and still lack a full account of its history. That is the situation here.