Color Color Color (American English), or colour (Commonwealth English), is the characteristic of human visual perception described through color "categories", with names such as red, orange, yellow, green, blue, or purple. This perception of color derives from the stimulation of cone cells in the human eye by electromagnetic radiation in the visible spectrum. Color categories and physical specifications of color are associated with objects through the wavelength of the light that is reflected from them. This reflection is governed by the object's physical properties such as light absorption, emission spectra, etc. By defining a color space, colors can be identified numerically
Moving walkway the book, the fast lane stops while the second lane keeps running at ). In the Wells and Asimov works there are more steps in the speed scale and the speeds are less extreme. In Arthur C. Clarke's novel, "Against the Fall of Night" (later rewritten as "The City and the Stars") the Megacity of Diaspar is interwoven with "moving ways" which, unlike Heinlein's conveyor belts, are solid floors that can mysteriously move as a fluid. In the novel, Clarke writes, In his non-fiction book "Profiles of the Future", Arthur C. Clarke mentions moving sidewalks but made of some sort