For every one of these types, there is also an antiparticle. Antiparticles have the same mass as their normal counterparts, except they have the opposite electric charge. Anti-matter and matter cannot exist near each other. Whenever matter and antimatter collide, they destroy each other with a huge release of energy equivalent to E=mc, where m is the combined mass of the particles, c is the speed of light, and E is the energy produced. These collisions often take place in large particle accelerators, where the energy can be converted the other way, into matter by the same equation. This can produce many odd, often heavy (large mass) particles that exist only for a short time.