0_Wizard
I like the color red. Its at the end of the visible light spectrum.
Red is the colour at the end of the visible spectrum of light, next to orange and opposite violet.
chosen_Red_0
Red
chosen_topic_0_Red
Grow light
A grow light or plant light is an artificial light source, generally an electric light, designed to stimulate plant growth by emitting a light appropriate for photosynthesis. Grow lights are used in applications where there is either no naturally occurring light, or where supplemental light is required. For example, in the winter months when the available hours of daylight may be insufficient for the desired plant growth, lights are used to extend the time the plants receive light. If plants do not receive enough light, they will grow long and spindly. Grow lights either attempt to provide a light spectrum similar to that of the sun, or to provide a spectrum that is more tailored to the needs of the plants being cultivated.
Metamaterial cloaking
Metamaterial cloaking is the usage of metamaterials in an invisibility cloak. This is accomplished by manipulating the paths traversed by light through a novel optical material. Metamaterials direct and control the propagation and transmission of specified parts of the light spectrum and demonstrate the potential to render an object seemingly invisible. Metamaterial cloaking, based on transformation optics, describes the process of shielding something from view by controlling electromagnetic radiation. Objects in the defined location are still present, but incident waves are guided around them without being affected by the object itself.
Infrared photography
In infrared photography, the film or image sensor used is sensitive to infrared light. The part of the spectrum used is referred to as near-infrared to distinguish it from far-infrared, which is the domain of thermal imaging. Wavelengths used for photography range from about 700 nm to about 900 nm. Film is usually sensitive to visible light too, so an infrared-passing filter is used; this lets infrared (IR) light pass through to the camera, but blocks all or most of the visible light spectrum (the filter thus looks black or deep red). ("Infrared filter" may refer either to this type of filter or to one that blocks infrared but passes other wavelengths.)
Fluorescence
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation. The most striking example of fluorescence occurs when the absorbed radiation is in the ultraviolet region of the spectrum, and thus invisible to the human eye, while the emitted light is in the visible region, which gives the fluorescent substance a distinct color that can only be seen when exposed to UV light. Fluorescent materials cease to glow immediately when the radiation source stops, unlike phosphorescence, where they continue to emit light for some time after.
Infrared
Infrared radiation is electromagnetic radiation (EMR) with longer wavelengths than those of visible light, and is therefore invisible to the human eye. It is sometimes called infrared light. It extends from the nominal red edge of the visible spectrum at 700 nanometers (frequency 430 THz), to 1 millimeter (300 GHz) (although specially pulsed lasers can allow humans to detect IR radiation up to 1050 nm.). Most of the thermal radiation emitted by objects near room temperature is infrared. Like all EMR, IR carries radiant energy, and behaves both like a wave and like its quantum particle, the photon.
Light
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 400–700 nanometres (nm), or 4.00 × 10 to 7.00 × 10 m, between the infrared (with longer wavelengths) and the ultraviolet (with shorter wavelengths). This wavelength means a frequency range of roughly 430–750 terahertz (THz). The main source of light on Earth is the Sun. Sunlight provides the energy that green plants use to create sugars mostly in the form of starches, which release energy into the living things that digest them.
Li-Fi
Li-Fi (; short for "light fidelity") is a technology for wireless communication between devices using light to transmit data. In its present state only LED lamps can be used for the transmission of visible light. The term was first introduced by Harald Haas during a 2011 TEDGlobal talk in Edinburgh. In technical terms, Li-Fi is a visible light communications system that is capable of transmitting data at high speeds over the visible light spectrum, ultraviolet and infrared radiation. In terms of its end use the technology is similar to Wi-Fi. The key technical difference is that Wi-Fi uses radio frequency to transmit data.
1_Apprentice
Red is a great color.  
0_Wizard
Also red has a dominant wavelength measured at approximately 625-740 nanometres. 
It has a dominant wavelength of approximately 625–740 nanometres.
chosen_Red_0
Red
chosen_topic_0_Red
Red
Red is the colour at the end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–740 nanometres. It is a primary color in the RGB color model and the CMYK color model, and is the complementary color of cyan. Reds range from the brilliant yellow-tinged scarlet and vermillion to bluish-red crimson, and vary in shade from the pale red pink to the dark red burgundy. The red sky at sunset results from Rayleigh scattering, while the red color of the Grand Canyon and other geological features is caused by hematite or red ochre, both forms of iron oxide.
Blue
Blue is one of the three primary colours of pigments in painting and traditional colour theory, as well as in the RGB colour model. It lies between violet and green on the spectrum of visible light. The eye perceives blue when observing light with a dominant wavelength between approximately 450 and 495 nanometres. Most blues contain a slight mixture of other colors; azure contains some green, while ultramarine contains some violet. The clear daytime sky and the deep sea appear blue because of an optical effect known as Rayleigh scattering. An optical effect called Tyndall scattering explains blue eyes.
Dominant wavelength
In color science, the dominant wavelength (and the corresponding complementary wavelength) are ways of characterizing any light mixture in terms of the monochromatic spectral light that evokes an identical (and the corresponding opposite) perception of hue. For a given physical light mixture, the dominant and complementary wavelengths are not entirely fixed, but vary according to the illuminating light's precise color, called the white point, due to the color constancy of vision. On the CIE color coordinate space , a straight line drawn between the point for a given color and the point for the color of the illuminant can be extrapolated out so that it intersects the perimeter of the space in two points.
Color
Color (American English) or colour (Commonwealth English) is the characteristic of human visual perception described through color "categories", with names such as red, blue, yellow, green, orange, or purple. This perception of color derives from the stimulation of cone cells in the human eye by electromagnetic radiation in the spectrum of light. 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.
PAL
Phase Alternating Line (PAL) is a colour encoding system for analogue television used in broadcast television systems in most countries broadcasting at 625-line / 50 field (25 frame) per second (576i). Other common colour encoding systems are NTSC and SECAM. All the countries using PAL are currently in process of conversion or have already converted standards to DVB, ISDB or DTMB. This page primarily discusses the PAL colour encoding system. The articles on broadcast television systems and analogue television further describe frame rates, image resolution and audio modulation. In the 1950s, the Western European countries commenced planning to introduce colour television, and were faced with the problem that the NTSC standard demonstrated several weaknesses, including colour tone shifting under poor transmission conditions, which became a major issue considering Europe's geographical and weather-related particularities.
Delay line memory
Delay line memory is a form of computer memory, now obsolete, that was used on some of the earliest digital computers. Like many modern forms of electronic computer memory, delay line memory was a refreshable memory, but as opposed to modern random-access memory, delay line memory was sequential-access. Analog delay line technology had been used since the 1920s to delay the propagation of analog signals. When a delay line is used as a memory device, an amplifier and a pulse shaper are connected between the output of the delay line and the input. These devices recirculate the signals from the output back into the input, creating a loop that maintains the signal as long as power is applied.
Speed of light
The speed of light in vacuum, commonly denoted , is a universal physical constant important in many areas of physics. Its exact value is (approximately , or ). It is exact because the unit of length, the metre, is defined from this constant and the international standard for time. According to special relativity, is the maximum speed at which all conventional matter and hence all known forms of information in the universe can travel. Though this speed is most commonly associated with light, it is in fact the speed at which all massless particles and changes of the associated fields travel in vacuum (including electromagnetic radiation and gravitational waves).
1_Apprentice
Interesting.  Rubies are pretty too.
0_Wizard
Yes, they are. In prehistoric art, red was one of the first colors that was used.
Red pigment made from ochre was one of the first colors used in prehistoric art.
chosen_Red_0
Red
chosen_topic_0_Red
Red
Red is the colour at the end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–740 nanometres. It is a primary color in the RGB color model and the CMYK color model, and is the complementary color of cyan. Reds range from the brilliant yellow-tinged scarlet and vermillion to bluish-red crimson, and vary in shade from the pale red pink to the dark red burgundy. The red sky at sunset results from Rayleigh scattering, while the red color of the Grand Canyon and other geological features is caused by hematite or red ochre, both forms of iron oxide.
Prehistoric art
In the history of art, prehistoric art is all art produced in preliterate, prehistorical cultures beginning somewhere in very late geological history, and generally continuing until that culture either develops writing or other methods of record-keeping, or makes significant contact with another culture that has, and that makes some record of major historical events. At this point ancient art begins, for the older literate cultures. The end-date for what is covered by the term thus varies greatly between different parts of the world. The earliest human artifacts showing evidence of workmanship with an artistic purpose are the subject of some debate.
Prehistoric art in Scotland
Prehistoric art in Scotland is visual art created or found within the modern borders of Scotland, before the departure of the Romans from southern and central Britain in the early fifth century CE, which is usually seen as the beginning of the early historic or Medieval era. There is no clear definition of prehistoric art among scholars and objects that may involve creativity often lack a context that would allow them to be understood. The earliest examples of portable art from what is now Scotland are highly decorated carved stone balls from the Neolithic period, which share patterns with Irish and Scottish stone carvings.
Prehistoric Rock-Art Site of the Côa Valley
The Prehistoric Rock-Art Site of the Côa Valley is an open-air Paleolithic archaeological site located in a region of northeastern Portugal, along the Portuguese-Spanish border. In the early 1990s rock engravings were discovered in Vila Nova de Foz Côa in the course of the construction of a dam in the valley of the Côa River. They include thousands of engraved rock drawings of horses, bovines and other animals, human and abstract figures, dated from 22,000 to 10,000 years B.C. The sites were reviewed by archaeologists and other specialists of UNESCO and other agencies. Public support grew for preservation of the archaeological artifacts and rock paintings both within Portugal and internationally, and in 1995 elections led to a change in government.
Yellow
Yellow is the color between green and orange on the spectrum of visible light. It is evoked by light with a dominant wavelength of roughly 570590 nm. It is a primary color in subtractive color systems, used in painting or color printing. In the RGB color model, used to create colors on television and computer screens, yellow is a secondary color made by combining red and green at equal intensity. Carotenoids give the characteristic yellow color to autumn leaves, corn, canaries, daffodils, and lemons, as well as egg yolks, buttercups, and bananas. They absorb light energy and protect plants from photodamage.
Art of Europe
The art of Europe or Western art encompasses the history of visual art in Europe. European prehistoric art started as mobile rock, and cave painting art, and was characteristic of the period between the Paleolithic and the Iron Age. Written histories of European art often begin with the art of the Ancient Middle East, and the Ancient Aegean civilisations, dating from the 3rd millennium BC. Parallel with these significant cultures, art of one form or another existed all over Europe, wherever there were people, leaving signs such as carvings, decorated artifacts and huge standing stones. However a consistent pattern of artistic development within Europe becomes clear only with the art of Ancient Greece, adopted and transformed by Rome and carried; with the Empire, across much of Europe, North Africa and the Middle East.
Black
Black is the darkest color, the result of the absence or complete absorption of visible light. It is an achromatic color, literally a color without hue, like white (its opposite) and gray. It is often used symbolically or figuratively to represent darkness, while white represents light. Black ink is the most common color used for printing books, newspapers and documents, because it has the highest contrast with white paper and is the easiest to read. For the same reason, black text on a white screen is the most common format used on computer screens. In color printing it is used along with the subtractive primaries cyan, yellow, and magenta, in order to help produce the darkest shades.