# Matter - antimatter collision [duplicate]

I have read that when matter and antimatter collide they just cancel out each other with the emmision of bright light. But doesn't it violate law of conservation of mass? If the the atoms dissapear into nowhere?

Antimatter comes from the level of quantum mechanics and particle physics, not classical physics, and is subject to special relativity mechanics, not Newtonian mechanics. Specifically the particles are described by four vectors, $(E,p_x,p_y,p_z)$ where E is the energy of the particle and p the momentum.