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Rossella Vanon | 9781138119888 | | | | | Blue light has a dark side - Harvard Health

Lighting People 1st edition seems to be disabled in your browser. You must have JavaScript enabled in your browser to utilize the functionality of this website. The history of the light bulb is filled with rivalry, failures and great achievements. The bulb has been called the most important invention since man-made fire. The light bulb helped to establish social order after sundown, extended the workday well into the night, and allowed us to navigate and travel safely in the dark. Without the light bulb, there would be no nightlife. However, creating a steady and affordable source of illumination was not as easy as many history textbooks suggest. The modern light bulb is the result of many innovators' work and Lighting People 1st edition improvements over years. The First Artificial Sources of Light. Before the arrival of electric lighting, people used a variety of tricks for navigating their neighborhoods at night. In The Downs, an area near the English Channel, patches of chalky soil were used as beacons known as down . In wooded areas, bark was strategically cut from trees to expose the lighter wood underneath. However, on most clear nights, the moon and starlight were strong enough to navigate at night. In the 18th century, and oil lamps illuminated many light fixtures in most homes and businesses. These early sources of illumination emitted a weak light, smoked, and gave off foul odors. They were also dangerous and required constant attention. Wealthy aristocrats used beeswax and spermaceti candles to light up their lavish households. The middle Lighting People 1st edition used cheap tallow candles while the poor used , makeshift candles made from reeds dipped in animal or vegetable fat and ignited, which burned Lighting People 1st edition a short time. During the 19th century, Lighting People 1st edition candles and oil lamps in many homes, businesses, and streets. Gas lamps produced a brighter and more efficient illumination. They also cost 75 percent less than candles or oil lamps, and were easier and safer to operate. By the s, most city streets in the United States and Europe were illuminated by gas lamps. Gas lighting is credited with reducing crime rates and increasing literacy in many areas. As electricity became more widespread during the turn of the century, gas lamps were replaced by incandescent lamps in streets, businesses, and theaters. The First Electric Lights. InSir Humphry Davy, an English physician, created the first electric light by passing a current through a Lighting People 1st edition strip. InDavy demonstrated the first carbon at the Royal Institute in by connecting two wires to a battery and attaching a charcoal strip between the other ends of the wires. While the scientific community and the public raved about the demonstration, the arc lamp burned too brightly and consumed a large amount of current, which quickly drained the battery and rendered the lamp impractical for commercial development and production. Several decades passed before electric generators made arc lamps practical for street and theater lighting. InPavel Nikolayevich Yablochkov, a Russian electrical engineer and inventor, developed the first practical arc lamp known as the "Yablochkov . Arc lamps produced an intense, bright light that was ideal for illuminating streets and outdoor spaces, but the dazzling lights were not suitable for indoor use. Lighting People 1st edition the late s, Thomas A. Edison and many other inventors began to experiment with incandescent lamps in search for a reliable and economical form of indoor lighting. Arc lamps were used for , lighthouses, stadium lights, film production lights, film projector lamps, and other high-intensity lighting applications until the s when advancements in short-arc lamps made them obsolete. The First Incandescent Light Bulbs. Incandescent light bulbs use electricity to heat Lighting People 1st edition carbon or metal base filament inside a glass bulb until it becomes hot and emits a radiant glow. A vacuum keeps the filament from burning up too quickly and blackening the interior of the glass bulb. However, these early experiments were pivotal in the development of the first commercially viable . InFrederick de Moleyns received the first patent for an incandescent lamp in England. The lamp used a glass bulb, a partial vacuum and powdered charcoal between two platinum filaments to emit light. However, the lamp was not efficient enough for commercial use. The vacuum's poor design caused the bulb to darken at the top and block light output, and the platinum filaments were too expensive. Inventors developing incandescent lamps quickly adopted the invention because it helped to preserve the filament inside the bulb. InHenry Woodward and Mathew Evans filed a patent for an incandescent light bulb with a carbon filament in Canada and the United States. The light bulbs, although they worked properly, sold poorly. They sold their patent to Thomas Edison in Lighting People 1st edition InWilliam E. Sawyer and Albion Man received the first U. The first Westinghouse light bulbs were based on the Sawyer-Man incandescent lamps. In many textbooks, Thomas A. Edison, an undisputed visionary, was not the only one competing to develop the first commercial incandescent bulb. Countless chemists, physicists, and inventors clamored for the honor and substantial payoff. Lighting People 1st editiona young Edison stated that he could create a safer, cheaper, and more reliable incandescent light to replace existing gas lights in just six weeks. The announcement caused gas company stocks to plummet. To prevent the filament from overheating and burning out, a problem that plagued earlier inventors, he created a regulating system that intermittently diverted the current away from the filament, permitting it to cool. The system was difficult to manufacture and operate, and the light bulb itself would shut off every few minutes, rendering the lamp impractical for commercial development. At the same time, Sir Joseph Wilson Swan, an English chemist and physicist, was independently working on an incandescent light bulb with a carbon filament. Swan began working on the incandescent bulb three decades earlier, but like other early inventors, he lacked a reliable vacuum and a suitable electric source to create a practical light bulb. In latehe reported to the Newcastle Chemical Society that he had created a working incandescent lamp and he received a UK patent that same year. In FebruarySwan demonstrated a working lamp during a lecture at the Newcastle Literary and Philosophical Society. His lamp design included an enclosed bulb with the air removed, platinum lead wires, and light-emitting carbon Lighting People 1st edition. The carbon rod had low electrical resistance and required a large amount of current to heat up and make the filament glow, which meant that the electric conductors to the lamp had to be short or unreasonably thick. The rod also released gasses when the lamp was turned on and dark soot quickly accumulated inside the glass, blocking light output. Swan improved his design and eventually established his own electric lighting company, The Swan Electric Light Company, in InEdison and his team discovered that a thin filament with high electrical resistance was more efficient. This meant that only a small amount of Lighting People 1st edition and reasonably sized copper cables were needed to make the filament glow. The team also experimented with carbonized filaments made from baywood, boxwood, cedar, cotton, hickory, and flax. InEdison's team improved the light bulb with a bamboo filament that burned for 1, hours. The carbonized bamboo filament became the standard filament for the next ten years. The same year, Edison received a second U. Representatives of the Edison Electric Light Company promoted the new incandescent lamps by holding demonstrations at the Menlo Park lab and attending trade shows and expositions all around the Lighting People 1st edition. The demonstrations were designed to associate Edision's name with the new lighting technology. During this time, Edison pursued legal action after Swan after mutual allegations of patent infringement. Edison bought Swan out of the company after a few years. Thomas Edison did not invent the first light bulb; however, he did improve the design and performance of the earliest incandescent lamps to create the first commercially viable Lighting People 1st edition bulb. He also developed other inventions that made the light bulb practical to for everyday use. The , a system of screw mounts that ensures compatibility between a light bulb and the base of a , and a complete electrical lighting system including feeders, switches and meters not only capitalized on his light bulb design, but it also made him a household name and secured his name in the history books. Edison's light bulb remained unaltered for several decades. InWilliam D. Coolidge, an American physicist at General Electric GEdeveloped tungsten filaments that lasted longer and burned brighter than carbon filaments. GE overhauled their bulb-making equipment and began selling light bulbs with tungsten filaments, replacing the carbonize bamboo filaments. InMarvin Pipkin, a American chemist and inventor, developed the frosted incandescent light bulb. Pipkin also devised a silica coating process that helped diffuse light, reduce , and minimize loss of light output. The halogen light bulb was first introduced in by GE. These light bulbs, while an adaptation of incandescent light bulbs, reduced the uneven evaporation of the filament and darkening of the envelope by filling the lamp with halogen gas rather than an inert gas. Halogen bulbs also lasted longer with an average life of 1, hours, and consumed 15 percent less energy. Despite numerous improvements over the years, modern incandescent bulbs remained inefficient. About ten percent of the electric power supplied to an incandescent light bulb is actually converted into visible light. The remaining energy is wasted as heat. The U. Lighting engineers began to adapt fluorescent lighting for residential use. Fluorescent lamps had been in use since the s, but they were mainly used for commercial Lighting People 1st edition industrial lighting. InEdward E. Hammer, an engineer at GE, bent a fluorescent tube into a spiral shape, creating the first compact fluorescent light bulb CFL. GE initially shelved the design because the machinery needed to mass produce Lighting People 1st edition light bulbs was too expensive at the time. The design was leaked and shortly thereafter, other manufacturers began to produce the light bulb. Consumers were hesitant to embrace the new lighting technology due to its price, size, and performance. Early CFLs were big and bulky, and did not fit in many light fixtures. They light bulbs also emitted a low light and performed inconsistently. History of street lighting in the United States - Wikipedia

For this reason, many regard Philadelphia as the birthplace of street lighting in the US. The colonial-era streetlights were lit by candles placed inside a glass vessel, which kept the candle from being blown out by wind. Franklin's design was four-sided, with four separate panes of glass, so that if one pane of glass was broken, the lamp did not need to be entirely replaced, and might not even blow out. After Lighting People 1st edition invention of gas lighting by William Murdoch incities in Britain began to light their streets using gas. The United States followed Lighting People 1st edition shortly afterwards with the introduction of gas lighting to Pelham Street in NewportRhode Lighting People 1st editionin Some locations in the US still use gas lights. After Thomas Edison pioneered electric use, light bulbs were developed for the streetlights as well. The first city Lighting People 1st edition the United States to successfully demonstrate Lighting People 1st edition lighting was Cleveland, Ohiowith twelve electric lights around the Public Square road system on 29 April Brush of Cleveland, Ohio wanted to publicly test his new invention the "Brush light" and needed a city to do so. The city council of Wabash, Indiana agreed to testing the lights and on March 31,Wabash became the "First Electrically Lighted City in the World" as a flood of light engulfed the town from four Brush lights mounted atop the courthouse. Lighting People 1st edition of the original Brush lights is on display at the Wabash County Courthouse. Fluorescent and incandescent lights became popular during the s and s, when automobile travel began to Lighting People 1st edition. A street with lights was referred to as a white way during the early 20th century. Part of Lighting People 1st edition York City's Broadway was nicknamed the Great White Way due to the massive number of electric lights used on theater marquees lining the street. The two main manufacturers in the American street lighting industry during the s were General Electric and Westinghouse. During this era, the most common lanterns in the local street lighting industry were Form and later, Form made by General Electric, and OV made by Westinghouse. Ina new breed of streetlight fixture was introduced; the "cobraheads". If viewed from beneath they resembled a cobra 's flared neck. Westinghouse dubbed its cobraheads the Silverliners, which remained in production over the next 25 years. The first model, the OV, is still a common streetlight fixture in many roads in North America. GE later introduced its own cobrahead, called the M The original M is noted for Lighting People 1st edition pointed front end that protrudes over its bowl-shaped diffuser also called a refractor. The M was the OV's main rival. They carried — watt bulbs and were common on Interstate highways and city boulevards. GE made the M which was exactly same design as the M but using plastic refractor made for watt. The M production ended in replacing with a MR. InWestinghouse produced an updated version of the OV, with a more rounded look. Only the diffuser was left unchanged. InGE updated its M and M with its PowrDoor design, in which two separate doors, one for the lamp, and one for the gear were used, rather than one door for both. Gone was the protruding front end, and the new MA and MA were also more streamlined although the original M and MR continued to be produced until Ina split-door M was introduced that shared the MA's bodyshell but had a nonvented door Lighting People 1st edition in place with a spring latch, while the MA's vented door was held in place with a bail latch. GE and Westinghouse also developed smaller fixtures. A small version of the M was made for suburban residential streets and alleys. That fixture was called the MR which replaced the M which looked exactly like the M but with plastic lens and rated for watt. In the same vein, Westinghouse offered three smaller Silverliners. The OV whose look resembles a miniature OV came out inand it became the companion model to the Canadian-market OVB, which had been introduced in These smaller fixtures carried — watt light bulbs. The second- generation M and M were the first fixtures to sport the new high pressure sodium HPS lights that came out in The existing Silverliners could not handle these new lights, so Westinghouse developed a new OV, as well as a new OV Both of these new Silverliners also known as TuDors, and were similar to GE's popular PowrDoor series described above now had a flat bottom, and weren't nearly as popular as the originals. More new manufacturers entered the streetlighting industry. The Model 25 was later the basis for a larger lookalike, the Model All three fixtures had a boxy look that usually sported grinning diffusers, a nod to the OVs and Ms. Of the three fixtures, only the Model is still in production. Earlier versions of the M and OV and, in very rare instances, the Model are noted for having fins on top of the Lighting People 1st edition. As newer ones were made, the fins were eliminated. Some well-known light fixtures came from the Line Material Company. In the s, during the height of the mercury lights' popularity, Line Material produced the Unistyle and the smaller Unistyle Both of these fixtures combined various characteristics of the Silverliners and GE M-series fixtures. When the sodium era began aroundthe company by then, renamed McGraw-Edison produced the boxy, rectilinear, more simplified Unidoor for metropolitan expressways and city boulevards and Unidoor for smaller residential streets and Lighting People 1st edition. Inthe entire Silverliner line was discontinued, when Cooper Lighting bought Westinghouse's streetlighting division, and rebranded them as Crouse-Hinds models with the OV and OV becoming the L and L, respectively. GE and Cooper continued to take streetlighting to new heights. GE was a pioneer in the full-cutoff arena, when it created a spinoff of the popular M and the rarer M in This fixture is noted for its pointed front end and lack of a diffuser. In addition, high-mast assemblies were developed for the light towers that were springing up along Interstate highways. These new fixtures, called the andhad a more-rounded look than their respective predecessors. While the Model continues production today, the Model was replaced by the Model in InGE revamped its entire lineup. One, called the MR2, had a flat bottom reminiscent of the third-generation Silverliners and once again used a single door; the other, now called the MA2, retained the original design but no longer had the vented door that the previous model did. Also, the MR2 featured a slightly flatter profile than the MR it replaced, and the MA2 now took on the boxy profile that was previously used by the M, which had been introduced in More recently, teardrop lamps both existing and reproductions have been used in favor of cobraheads in both urban and suburban areas. They are usually complemented with bishop's crook poles and more elaborate architectural elements. King Luminaire a division of the StressCrete Group manufactures these. Cree have also become one of the most popular brands for LED lighting. Open Arc lamps Lighting People 1st edition used in the late 19th and early 20th century by many large cities for street lighting. Their bright light required that the early arc lamps be placed on rather high 60 to foot towers; as such, they might be considered the predecessor to today's high-mast lighting systems seen along major highways. They were also widely used in film and stage. Arc lamps use high current between two electrodes typically carbon rods and require substantial maintenance. Arc lights have mainly been used where high lumen light was needed such as lighthouses. Today very few open arc lights remain in operation, primarily in a few lighthouses and some industrial uses. The only remaining examples of original street lighting use are the moonlight tower of Austin, Texas. A xenon lamp is a high pressure sealed arc lampand is in common usage today where extreme brightness in a relatively small space is required, typically in motion picture projectors in theaters, and stage and motion picture lighting. They are also found in car . The sealed arc lamps do not suffer from the inefficiency and high maintenance problems of the original open arc lamps, but they are not well suited for most street lighting use. Incandescent lights using a tungsten filament were the first low power electric lights in cities worldwide and introduced some 20 years after open arc lamps [ when? Some can still be found in streetlight service. Others have been installed in popular downtown areas of major cities to have a nostalgia effect. Incandescent light has excellent Color rendering index rated at is generally around — K depending on the type of lamp and replaced the higher maintenance arc lamps. An incandescent light bulb is less efficient when compared to High-intensity discharge lamp and gas discharge lighting such as Neon light and are being replaced by more efficient compact fluorescent lamps or converted to mains voltage or high pressure sodium lamps. Tungsten-halogen incandescent lights which are brighter and more efficient and are very commonly used in theatrical and motion picture lighting and better color temperature characteristics are little used in street lighting due to their relatively short lifespan. Standard incandescent lamps are very commonly used in traffic signals, although Lighting People 1st edition are increasingly replaced by LEDs. The first became common in the late s. These lamps are a form of discharge lamp where a small current causes a gas in the tube to glow. The typical glow is strong in ultraviolet but weak in visible light. The glass envelope is coated in a mixture of phosphors that are excited by the ultraviolet light and emit visible light. Fluorescent lamps are much more efficient than incandescent lamps, and for a short time became popular in street lighting both because of the efficiency and the novelty value. Fluorescent lamps for street lighting were first introduced to the public for commercial uses at the World's Fair. The Lighting People 1st edition problems with standard fluorescent lamps for street lighting is that they are large, and produce a diffused non-directional light. They are also rather fragile. Therefore, the fixtures needed to be large, and could not be mounted more than 20—30 feet above the pavement if they were to produce an acceptable Lighting People 1st edition level. Fluorescent lamps quickly fell out of favor for main street lighting, but remained popular for parking lot and outside building illumination for roadside establishments. Inthe first regular production mercury vapor MV streetlight assembly was developed. It was Lighting People 1st edition a major improvement over the incandescent light bulband shone much brighter than incandescent or fluorescent lights. Initially people disliked them because their bluish-green light made people look like they had the blood drained from them. Other disadvantages are that a significant portion Lighting People 1st edition their light output is ultraviolet, and they "depreciate"; that is, they get steadily dimmer and dimmer with age while using the same amount of energy, and in a few rare instances, they also cycle at the end of their life cycles. Even rarer is they can burn out, especially when the light is being burned while dim usually at the end of the life cycle. The UV light excites the phosphor, producing a more "white" light. These are known as "color corrected" lamps. Emergency Lighting - 1st Edition

Although it is environmentally friendly, blue light can affect your sleep and potentially cause disease. Until the advent of artificial lighting, the sun was the major source of lighting, and people spent their evenings in relative darkness. Now, in much of the world, evenings are illuminated, and we take our easy access to all those lumens pretty much for granted. But we may be paying a price for basking in all that light. At night, light throws the body's biological clock—the circadian rhythm —out of whack. Sleep suffers. Worse, research shows that it may contribute Lighting People 1st edition the causation of cancer, diabetes, heart disease, and obesity. Not all colors of light have the same effect. Blue wavelengths—which are beneficial during daylight hours because they boost attention, reaction times, and mood—seem to be the most disruptive at night. And the proliferation of electronics with screens, as well as energy-efficient lighting, is increasing our exposure to blue wavelengths, especially after sundown. Everyone has slightly different circadian rhythms, but the average length is 24 and one-quarter hours. The circadian rhythm of people who stay up late is slightly longer, while the rhythms of earlier birds fall short of 24 hours. Charles Lighting People 1st edition of Harvard Medical School showed, inthat daylight keeps a person's internal clock aligned with the environment. Some studies suggest a link between exposure to light at night, such as working the night shift, to diabetes, heart disease, and obesity. That's not proof that nighttime light exposure causes these conditions; nor is it clear why it could Lighting People 1st edition bad Lighting People 1st edition us. A Harvard study shed a little bit of light on the possible connection to diabetes and possibly obesity. The researchers put 10 people on a schedule that gradually shifted the timing of their circadian rhythms. Their blood sugar levels increased, throwing them into a prediabetic state, and levels of leptin, a hormone that leaves people feeling full after a meal, went down. Exposure to light suppresses the secretion of melatonin, a hormone that influences circadian rhythms. Even dim light can interfere with a person's circadian Lighting People 1st edition and melatonin secretion. A mere eight lux—a level of brightness exceeded by most table lamps and about twice that of a night light—has an effect, notes Stephen Lockley, a Harvard sleep researcher. Light at night is part of the reason so many people don't get enough sleepsays Lockley, and researchers have linked short sleep to increased risk for depression, as well as diabetes and cardiovascular problems. While light of any kind can suppress the secretion of melatonin, blue light at night does so more powerfully. Harvard researchers and their colleagues conducted an experiment comparing the effects of 6. The blue light suppressed melatonin for about twice as long as the green light and shifted circadian rhythms by twice as much 3 hours vs. In another study of blue light, researchers at the University of Toronto compared the melatonin levels of people exposed to bright indoor light who were wearing blue-light—blocking goggles to people exposed to regular dim light without wearing goggles. The fact that the levels of the hormone were about the same in the two groups strengthens the hypothesis that blue light is a potent suppressor of melatonin. It also suggests that shift workers and night owls could perhaps protect themselves if they wore eyewear that blocks Lighting People 1st edition light. Inexpensive sunglasses with orange-tinted lenses block blue light, but Lighting People 1st edition also block other colors, so they're not suitable for use indoors at night. If blue light does have adverse health effects, then environmental concerns, and the quest for energy-efficient lighting, could be at odds with personal health. Those curlicue compact fluorescent lightbulbs and LED lights are much more energy-efficient than the old-fashioned incandescent lightbulbs we grew up with. But they also tend to produce more blue light. The physics of Lighting People 1st edition lights can't be changed, but coatings inside the bulbs can be so they produce a warmer, less blue light. LED lights are more efficient than fluorescent lights, but they also produce a fair amount of light in the blue spectrum. Richard Hansler, a light researcher at John Carroll University in Cleveland, notes that ordinary incandescent lights also produce some blue light, although less than most fluorescent lightbulbs. Disclaimer: As a service to our readers, Harvard Health Publishing Lighting People 1st edition access to our library of archived content. Please note the date of last review or update on all articles. No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician. Harvard Health Letter. What Lighting People 1st edition blue light? The effect blue light has on your sleep and more. Updated: July 7, Published: May, Staying Healthy Sleep. E-mail Address. First Name Optional.