Some consider white to be a color, because white light comprises all hues on the visible light spectrum. And many do consider black to be a color, because you combine other pigments to create it on paper. But in a technical sense, black and white are not colors, they’re shades.

There are three main theories of colour vision; the trichromatic theory, the opponent process theory and the dual processes theory.

Usually because they have more or fewer types of cone cells, the wavelength sensitive photoreceptors in the retina at the back of their eyes. These are people, mostly women, who have an extra set of cones. They can distinguish far more colours than anyone else.

Black is the absence of light. Some consider white to be a color, because white light comprises all hues on the visible light spectrum. And many do consider black to be a color, because you combine other pigments to create it on paper. But in a technical sense, black and white are not colors, they’re shades.

Because the light is outside the range of human vision, it is invisible, so a room illuminated with a black light appears dark. There are many types of black lights, including special fluorescent lamps, LEDs, incandescent lamps, and lasers. These light are not created equal, as each produces a unique spectrum of light….

Einstein’s theory of special relativity says that time slows down or speeds up depending on how fast you move relative to something else. Approaching the speed of light, a person inside a spaceship would age much slower than his twin at home. Picture a four-dimensional fabric called space-time….

This energy travels as electromagnetic waves at about the speed of light, which is miles per hour,1 or 300 million meters per second. 2 However, the electrons themselves within the wave move more slowly….