Reflective surfaces are surfaces that can deliver high solar reflectance (the ability to reflect the visible, infrared and ultraviolet wavelengths of the sun, reducing heat transfer to the surface) and high thermal emittance (the ability to radiate absorbed, or non-reflected solar energy). Reflective surfaces are a form of geoengineering.
The most well-known type of reflective surface is the cool roof. While cool roofs are mostly associated with white roofs, they come in a variety of colors and materials and are available for both commercial and residential buildings. Today's "cool roof" pigments allow metal roofing products to be EnergyStar rated in dark colors, even black.
Light is electromagnetic radiation within a certain portion of the electromagnetic spectrum. The word usually refers to visible light, which is visible to the human eye and is responsible for the sense of sight. Visible light is usually defined as having wavelengths in the range of nanometres (nm), between the infrared (with longer wavelengths) and the ultraviolet (with shorter wavelengths). This wavelength means a frequency range in terahertz (THz).
The primary properties of visible light are intensity, propagation direction, frequency or wavelength spectrum, and polarization, while its speed in a vacuum, is one of the fundamental constants of nature.
The world is a common name for the whole of human civilization, or for the planet Earth and all life upon it. In terms such as world map and world climate, world is used in the sense detached from human culture or civilization, referring to the planet Earth physically. In a philosophical context the term may refer to the whole of the physical Universe, or an ontological world, described by Martin Heidegger as world disclosure. In a theological context, world usually refers to the material or the profane sphere, as opposed to the celestial, spiritual, transcendent or sacred. The "end of the world" refers to scenarios of the final end of human history, often in religious contexts. World history is commonly understood as spanning the major geopolitical developments of about five millennia, from the first civilizations to the present. In terms such as world religion, world language, world government, and world war, world suggests international or intercontinental scope without necessarily implying participation of the entire world.