darkening
51Optics — For the book by Sir Isaac Newton, see Opticks. Optical redirects here. For the musical artist, see Optical (artist). Optics includes study of dispersion of light. Optics is the branch of …
52Pastel — For other uses, see Pastel (disambiguation). Commercial pastels Pastel is an art medium in the form of a stick, consisting of pure powdered pigment and a binder. The pigments used in pastels are the same as those used to produce all colored art… …
53Professional wrestling — For the Olympic sport, see Wrestling. For other uses, see Professional wrestling (disambiguation). Professional wrestling A professional wrestling match. Two wrestlers grapple in a wrestling ring while a referee (in white, right) looks on …
54Star — For other uses, see Star (disambiguation) …
55Radioactive waste — 2007 ISO radioactivity danger logo, designed in part for long term radioactive waste depositories which might survive into a far future time in which all knowledge of the meaning of present common radiation danger symbols and signs has been lost… …
56Human skin color — Skin pigmentation redirects here. For animal skin pigmentation, see Biological pigment. Variety of skin colors Human skin color is primarily due to the presence of melanin in the skin. Skin color ranges from almost black to white with a pinkish… …
57Optical amplifier — An optical amplifier is a device that amplifies an optical signal directly, without the need to first convert it to an electrical signal. An optical amplifier may be thought of as a laser without an optical cavity, or one in which feedback from… …
58Uranus — This article is about the planet. For other uses, see Uranus (disambiguation). Uranus   …
59Titan (moon) — Titan Titan in 2005 by Cassini spacecraft Discovery Discovered by Christiaan Huygens …
60Betelgeuse — Starbox begin name =Betelgeuse, Alpha OriStarbox image caption = Betelgeuse is the upper left star (pink arrow) in the rectangle of bright stars in Orion.Starbox observe epoch = J2000.0 constell = Orion ra = RA|05|55|10.3053cite web… …
