In a hospital PET scan, the patient receives a tracer that releases positrons inside the body. The scanner itself sends nothing in. It only catches pairs of photons flying out of the patient. Positrons go in; photons come out. What happens in between?
The patient's body is full of electrons. Each released positron almost immediately meets one. When a particle meets its antiparticle, both vanish. Their mass does not disappear into nothing: the mass turns into energy, and that energy typically flies away as photons.
Annihilation can happen because mass can convert into energy and energy can convert into the mass of new particles. A later topic puts an exact number on that conversion. For now, the fact is enough: when matter meets antimatter, the mass becomes energy.
That explains the PET scanner: each positron annihilates with an electron inside the patient, and the scanner catches the two photons that fly out.
A student says the mass of an annihilating pair is simply gone. What actually becomes of it?
The mass does not vanish into nothing.
Annihilation can happen because mass can convert into energy and energy can convert into the mass of new particles.
The mass converts into energy. It leaves as photons, not as nothing.
A proton meets an antiproton. What happens to the pair?
An electron and a positron meet, and both vanish into energy. What typically carries the energy away?
A particle and its antiparticle meet, both vanish, and their mass turns into energy. What is this event called?
Deep in space, an electron meets a positron. Afterward, what remains?
Annihilation turns a pair's mass into energy. Why is this conversion possible?
In a lab, antiprotons are sent into a tank of hydrogen gas, where they meet protons. What happens to the mass of each meeting pair?