Shadowlight is a form of light which exists at very small wavelengths, far beyond the visible spectrum. It has a smaller wavelength even than microwaves, enabling it to propagate through solid objects (without exciting their molecules and making them explode, as luck would have it). As it passes through solids, shadowlight excites the dark particles lying within them, causing a current of dark in the same direction. Thus, dark can be seen flowing out of the side of objects facing away from the light source. Transparent objects contain a much lower dark density, and thus produce weaker shadows.[...«]