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A street light , light pole , lamppost , street lamp , light standard , or lamp standard is a raised source of light on the edge of a road or walkway. Modern lamps may also have light-sensitive photocells that activate automatically when light is or is not needed: dusk , dawn , or the onset of dark weather . This function in older lighting systems could have been performed with the aid of a solar dial . Many street light systems are being connected underground instead of wiring from one utility post to another.

Early lamps were used by Greek and Roman civilizations, [ citation needed ] where light primarily served the purpose of security , both to protect the wanderer from tripping on the path over something or keeping the potential robbers at bay. [ citation needed ] At that time oil lamps were used predominantly as they provided a long-lasting and moderate flame. The Romans had a word 'lanternarius', which was a term for a slave responsible for lighting the oil lamps in front of their villas. This task remained the responsibility of a designated person up to the Middle Ages where the so-called ' link boys ' escorted people from one place to another through the murky winding streets of medieval towns.

Before incandescent lamps, candle lighting was employed in cities. The earliest lamps required that a lamplighter tour the town at dusk, lighting each of the lamps. According to some sources, illumination was ordered in London in 1417 by Sir Henry Barton , Mayor of London though there is no firm evidence of this. [1]

The first widespread system of street lighting used piped coal gas as fuel. Stephen Hales was the first person who procured a flammable fluid from the actual distillation of coal in 1726 and John Clayton, in 1735, called gas the "spirit" of coal and discovered its flammability by accident.

William Murdoch (sometimes spelled "Murdock") was the first to use the flammability of gas for the practical application of lighting. In the early 1790s, while overseeing the use of his company's steam engines in tin mining in Cornwall, Murdoch began experimenting with various types of gas, finally settling on coal-gas as the most effective. He first lit his own house in Redruth , Cornwall in 1792. [3] In 1798, he used gas to light the main building of the Soho Foundry and in 1802 lit the outside in a public display of gas lighting, the lights astonishing the local population.

The first public street lighting with gas was demonstrated in Pall Mall, London on January 28, 1807 by Frederick Albert Winsor . [ citation needed ] In 1812, Parliament granted a charter to the London and Westminster Gas Light and Coke Company , and the first gas company in the world came into being. Less than two years later, on December 31, 1813, the Westminster Bridge was lit by gas. [ citation needed ]

Following this success, gas lighting spread to other countries. The use of gas lights in Rembrandt Peale 's Museum in Baltimore in 1816 was a great success. Baltimore was the first American city with gas streetlights, provided by Peale's Gas Light Company of Baltimore.

1-2-2017  · radiometric dating n. A method for determining the age of an object based on the concentration of a particular radioactive isotope contained within it and ...

Is Dating Really Important? Index For This Page: I wish this page was unnecessary. Because of the distortions and lies spread by fundamentalists about scientific ...

ra·di·o·paque (rā′dē-ō-pāk′) adj. Not allowing the passage of x-rays or other radiation. ra′di·o·pac′i·ty (-ō-păs′ĭ-tē) n. radiopaque ...

A flare , also sometimes called a fusee, is a type of pyrotechnic that produces a brilliant light or intense heat without an explosion. Flares are used for signalling ...

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A flare , also sometimes called a fusee , is a type of pyrotechnic that produces a brilliant light or intense heat without an explosion . Flares are used for signalling, illumination, or defensive countermeasures in civilian and military applications. Flares may be ground pyrotechnics, projectile pyrotechnics, or parachute-suspended to provide maximum illumination time over a large area. Projectile pyrotechnics may be dropped from aircraft, fired from rocket or artillery , or deployed by flare guns or handheld percussive tubes.

The earliest recorded use of gunpowder for signalling purposes was the 'signal bomb' used by the Song Dynasty Chinese as the Mongol -led Yuan Dynasty besieged Yangzhou in 1276. [1] These soft-shelled bombs, timed to explode in mid-air, were used to send messages to a detachment of troops far in the distance. Another mention of the signal bomb appears in a text dating from 1293 requesting their collection from those still stored in Zhejiang . [1] A signal gun appears in Korea by 1600. The Wu I Thu Phu Thung Chih or Illustrated Military Encyclopedia written in 1791 depicts a signal gun in an illustration. [2]

Flares produce their light through the combustion of a pyrotechnic composition . The ingredients are varied, but often based on strontium nitrate , potassium nitrate , or potassium perchlorate and mixed with a fuel such as charcoal , sulfur , sawdust , aluminium , magnesium , or a suitable polymeric resin. [3] Flares may be colored by the inclusion of pyrotechnic colorants . Calcium flares are used underwater to illuminate submerged objects.

Many in-service colored signal flares and spectrally balanced decoy flares contain perchlorate oxidizers. Perchlorate, a type of salt in its solid form, dissolves and moves rapidly in groundwater and surface water. Even in low concentrations in drinking water supplies, perchlorate is known to inhibit the uptake of iodine by the thyroid gland. While there are currently no US federal drinking water standards for perchlorate, some states have established public health goals, or action levels, and some are in the process of establishing state maximum contaminant levels. For example, the US Environmental Protection Agency have studied the impacts of perchlorate on the environment as well as drinking water. [4] California has also issued guidance regarding perchlorate use. [5]

US courts have taken action regarding the use of perchlorate in manufacturing pyrotechnic devices such as flares. For example, in 2003, a federal district court in California found that Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) applied because perchlorate is ignitable and therefore a “characteristic” hazardous waste. (see Castaic Lake Water Agency v. Whittaker, 272 F. Supp. 2d 1053, 1059–61 (C.D. Cal. 2003)).

In the civilian world, flares are commonly used as signals, and may be ignited on the ground or fired as an aerial signal from a pistol -like flare gun , or launched from a self-contained tube. Flares are commonly found in marine survival kits.

Red flares, either sent as a rocket or held in the hand, are widely recognized as a maritime distress signal. [6] RMS Titanic however used rocket-launched distress shells to attract assistance, emitting white stars to a great height and a deafening sound. [ citation needed ]



Radiopaque - definition of radiopaque by The Free Dictionary

1-2-2017  · radiometric dating n. A method for determining the age of an object based on the concentration of a particular radioactive isotope contained within it and ...

Is Dating Really Important? Index For This Page: I wish this page was unnecessary. Because of the distortions and lies spread by fundamentalists about scientific ...

ra·di·o·paque (rā′dē-ō-pāk′) adj. Not allowing the passage of x-rays or other radiation. ra′di·o·pac′i·ty (-ō-păs′ĭ-tē) n. radiopaque ...

A flare , also sometimes called a fusee, is a type of pyrotechnic that produces a brilliant light or intense heat without an explosion. Flares are used for signalling ...