More than two hundred years passed after Thomas Young performed the famous double-slit experiment as a demonstration of the wave behavior of visible light and still it's revelation puzzles our sanity ever since. In short, if we shoot a beam of light at a panel with two small slits (less than a millimeter apart), the photons - elementary particles that light is made of, have to figure out how to get through the slits to radiate out the other side. If they are truly particles, like in macro world, they would project a solid image of two piles on the background wall behind the slits. If they travel similar to the waves, like water does in macro world, the image would resemble a wave-like interference pattern: alternating locations, equidistantly spaced, where particles leave a mark on the wall. Thanks to the outcome of the experiment, we know that light is capable to do both. It always travel in wave like fashion, even if we shoot photons in a row towards slits, one after another. Qua...