Gerald Florence, age 14, of Roselle, I11., for his question:

WHAT IS ANTIMATTER?

Antimatter is material composed of atomic particles that are the opposite of ordinary atomic particles. These opposite particles are called antiparticles, and they have an electric charge or some other property that is the reverse of an ordinary particle’s.

The electron is an ordinary atomic particle that has a negative electric charge. The electron’s antiparticle, the positron, has a positive electric charge. Both ‘the electron and the positron have the same mass. When they collide, they destroy each other and produce a form of energy called gamma radiation.

Antimatter could never be found on earth, and, if it does exist, it exists outside the solar system. Some astronomers believe energy from colliding galaxies consists of antimatter.