ABSTRACT
The quantum theory was founded by Max Planck, but it was Albert Einstein who made the simplest and probably the most universally valid statement about it, namely that when matter emits or absorbs light, the energy is transformed in single units. Physicists are agreed that Einstein's theory works very exactly so long as the two observers are in uniform motion relative to one another, like a man on a platform and a man in a steadily moving train. The energy of blue light is given out in bigger packets than that of red light, and that of red light in bigger packets than that of infra-red radiation, which physicist cannot see, but can feel as heat. When one attempts to apply it to events which are very far apart in space or time it yields results which are probably incorrect.
