WWII poster, reminding citizens of blackouts for civil defense

A blackout in time of war, or apprehended war, refers to the practice of collectively minimizing external light, including upward-directed (or reflected) light. This was done in the 20th century to keep the crews of enemy aircraft from being able to navigate to their targets simply by sight. In coastal regions a shore-side blackout of city lights would also help protect ships from being seen and attacked by enemy submarines farther out to sea. The term blackout in peacetime refers to a cessation of electrical energy through electric power transmission systems. ... Image File history File links Size of this preview: 451 × 599 pixel Image in higher resolution (771 × 1024 pixel, file size: 89 KB, MIME type: image/jpeg) Poster reminding citizens of complete blackouts as a civil defense procedure. ... Image File history File links Size of this preview: 451 × 599 pixel Image in higher resolution (771 × 1024 pixel, file size: 89 KB, MIME type: image/jpeg) Poster reminding citizens of complete blackouts as a civil defense procedure. ... Look up war in Wiktionary, the free dictionary. ... Prism splitting light Light is electromagnetic radiation with a wavelength that is visible to the eye (visible light) or, in a technical or scientific context, electromagnetic radiation of any wavelength[1]. The elementary particle that defines light is the photon. ... Spheres reflecting the floor and each other. ... (19th century - 20th century - 21st century - more centuries) Decades: 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s As a means of recording the passage of time, the 20th century was that century which lasted from 1901–2000 in the sense of the Gregorian calendar (1900–1999... Table of geography, hydrography, and navigation, from the 1728 Cyclopaedia. ... Italian Full rigged ship Amerigo Vespucci in New York Harbor, 1976 A ship is a large watercraft capable of deep water navigation. ... German UC-1 class World War I submarine A model of Günther Priens Unterseeboot 47 (U-47), German WWII Type VII diesel-electric hunter Typhoon class nuclear ballistic missile submarine USS Virginia, a Virginia-class nuclear attack (SSN) submarine A submarine is a specialized watercraft that can operate...

Lights can simply be turned off or light can sometimes be minimized by tarring the windows of large public structures. Tar is a viscous black liquid derived from the destructive distillation of organic matter. ...

These benefits against air attack are now largely nullified in the face of a technologically sophisticated enemy. As early as World War II, aircraft were using radio-beam navigation (see battle of the beams) and targets were detected by air to ground radar eg H2X. Today not only are night-vision goggles readily available to air crews, but sophisticated satellite-based and inertial navigation systems enable a static target to be found easily by either an aircraft or a guided missile. Combatants Allied powers: China France Great Britain Soviet Union United States and others Axis powers: Germany Italy Japan and others Commanders Chiang Kai-shek Charles de Gaulle Winston Churchill Joseph Stalin Franklin Roosevelt Adolf Hitler Benito Mussolini Hideki Tōjō Casualties Military dead: 17,000,000 Civilian dead: 33,000... The Battle of the Beams was a period in early World War II when Luftwaffe bombers started using radio navigation for night bombing. ... This long range Radar antenna, known as ALTAIR, is used to detect and track space objects in conjunction with ABM testing at the Ronald Reagan Test Site on the Kwajalein atoll[1]. Radar is a system that uses radio waves to determine and map the location, direction, and/or speed... The H2X radar, nicknamed the Mickey set, provided a ground mapping capability for both navigation and in daylight when overcast (and at night) for the USAAF during World War II. The H2X system replaced the British H2S radar. ... Two American soldiers pictured during the 2003 Iraq War seen through an Image Intensifier Night vision is the ability to see in a dark environment. ... An Earth observation satellite, ERS 2 For other uses, see Satellite (disambiguation). ... In physics, an inertial frame of reference, or inertial frame for short (also descibed as absolute frame of reference), is a frame of reference in which the observers move without the influence of any accelerating or decelerating force. ... A guided missile is a military rocket that can be directed in flight to change its flight path. ...

During the Battle of the Atlantic in World War II the German U-boats were greatly aided in the "second happy time" with the sinking of unescorted ships in American coastal waters, because the ships were back lit by coastal lights. In any naval war this would still be an advantage which a blackout would help to nullify. lalalalala Combatants Royal Navy Royal Canadian Navy United States Navy Kriegsmarine Regia Marina Commanders Sir Percy Noble Sir Max K. Horton Ernest J. King Erich Raeder Karl Dönitz Casualties 30,248 merchant sailors 3,500 merchant vessels 175 warships 28,000 sailors 783 submarines The Second Battle of the Atlantic... Combatants Allied powers: China France Great Britain Soviet Union United States and others Axis powers: Germany Italy Japan and others Commanders Chiang Kai-shek Charles de Gaulle Winston Churchill Joseph Stalin Franklin Roosevelt Adolf Hitler Benito Mussolini Hideki Tōjō Casualties Military dead: 17,000,000 Civilian dead: 33,000... U-boat is also a nickname for some diesel locomotives built by GE; see List of GE locomotives October 1939. ... The second happy time was a phase in the Second Battle of the Atlantic during which Axis submarines attacked merchant shipping along the east coast of North America. ...