I understand the fact the light can be proved to be both a particle and a wave, but one thing I don't understand: Every other wave I have known, travels through a medium of some sort. A wave consists of a particle moving one way and then back to its original position. Then the particles next to it move the same way and back to their original position. So, the wave can be said to be moving, but the particles consisting of the wave after it passes, stay in place. A light "wave" baffles me.. If there is nothing to move one way and back, how can a wave progress? http://www.kettering.edu/~drussell/Demos/waves-intro/waves-intro.html shows animations and explanations of what I mean as a wave.