In modern physics, antimatter is defined as matter composed of the antiparticles of the corresponding particles in "ordinary" matter. Minuscule numbers of antiparticles are generated daily at particle accelerators—total artificial production has been only a few nanograms—and in natural processes like cosmic ray collisions and some types of radioactive decay, but only a tiny fraction of these have successfully been bound together in experiments to form antiatoms. No macroscopic amount of antimatter has ever been assembled due to the extreme cost and difficulty of production and handling. Theoretically, a particle and its antiparticle have the same mass, but opposite electric charge, and other differences in quantum numbers. A collision between any particle and its anti-particle partner leads to their mutual annihilation, giving rise to various proportions of intense photons, neutrinos, and sometimes less-massive particle–antiparticle pairs.