What is light pollution and how does that effect us or how is it harmful to us?????

Question

What is light pollution and how does that effect us or how is it harmful to us?????

Answer 1

ONLY LIGHT POLLUTION I KNOW OF IS FLOURESENT BULBS, INCLUDING THE ROUND ONES, ALL THE FACTORIES CHANGED THEM OUT BECAUSE THEIR BAD FOR YOUR EYES AND WHEN THEY DROP AND BREAK THE POWDER INSIDE IS POISONOUS TO BREATHE.

Answer 2

to explain it simple, light pollution only blocks our view of the stars because light produces a dull orange thing or something that blocks other lights. it affect us by disrupting our view of the night sky. it is not really harmful.

Answer 3

Light pollution is a term that is used by amateur astronomers and hobbyists to  describe the night sky. A magnitude 3 sky has moderate light pollution, a 2 or below is severe pollution, and 5 to 6 is light, and 7 up is little or none.

The human eye is capable of seeing down to the 6/7 magnitude star. The higher the magnitude of the objects your trying to see, the fainter the objects are. The general rule for magnitudes is that for ever 0.5 magnitudes, you double the amount of seeable stars. Ex) For a 3 magnitude sky, you can see a faint trace of our Milky Way Galaxy, where a magnitude 4 sky, the (MWG) is much more pronounced.

For bright objects you classify them at an negative magnitudes. Ex) The Sun at -26 and the full moon at -12 mag. For comparison; The planets generally are bright objects and are assigned minus magnitudes.

Light pollution dims the sky to the point where only the brightest of the stars can be seen. You can see that the skies in the dark country side are very beautiful as compared to the city and surrounding suburbs.

http://antwrp.gsfc.nasa.gov/apod/ap04082...

http://stellafane.org/misc/dark_sky.html

Answer 4

It means the light from street lights and houses in towns.  the light is wasted by just lighting up the sky.  apart from wasting fuels & maybe global warming it's not harmful.

Answer 5

I think light pollution is described as the following clipped article.Light pollution can be defined as illumination (outdoor lighting) generated at night by cities and towns around the world that prohibit viewers from observation of the natural night sky (Wiley 1990).  It has been known to have negative impact in  the biological, environmental, and economical areas (Crawford 1999 and International Dark-Sky Association 1999).  Biologically, it has disoriented turtle hatchlings and nesting females and in humans it could possibly be contributing to psychological problems (Crawford 1999 and International Dark-Sky Association 1999).  Environmentally, it has prevented the observation of the natural night sky (Wiley 1990).  Finally, economically, it is a waste of unused light, overused energy, and wasted money (International Dark-Sky Association 1998).  Obviously, light pollution has an affect on many things and it is important to understand its causes and its problems to figure out a solution .

I am experiencing Hong Kong has the very severe light pollution problem. It has raised as a matter of public concern for the glaring florescent lights installed nearby their windows making them have the sleep problem. How can we have a comfortable life in Hong Kong, a cement forest is being surrounded by hot and noisy advertising lights all night long? More detailed information about light pollution is described in the following website.

http://search.yahoo.com/search?search=Wh...

Answer 6

Light pollution:

Light pollution, also known as photopollution or luminous pollution, is excess or obtrusive light created by humans. Among other effects, and like any other form of pollution, it disrupts ecosystems, can cause adverse health effects, obscures the stars for city dwellers, and interferes with astronomical observatories. Light pollution can be construed to fall into two main branches: annoying light that intrudes on an otherwise natural or low light setting and excessive light, generally indoors, that leads to worker discomfort and adverse health effects. Since the early 1980s, a global dark-sky movement has emerged, with concerned people campaigning to reduce the amount of light pollution.

Light pollution is a side effect of industrial civilization. Its sources include building exterior and interior lighting, advertising, commercial properties, offices, factories, streetlights, and illuminated sporting venues. It is most severe in highly industrialized, densely populated areas of North America, Europe, and Japan and in major cities in the Middle East like Cairo, but even relatively small amounts of light can be noticed and create problems. Like other forms of pollution, such as air, water and noise pollution, light pollution causes damage to the environment.

With recent advances in private spaceflight, the prospect of space-based orbiting billboards appearing in the near future has provoked concern that such objects may become another form of light pollution. With this in mind, the United States Federal Aviation Administration sought permission, in May 2005, to enforce a law prohibiting "obtrusive" advertising in earth orbit. Similar intentions are yet to be expressed by authorities in most other countries.

Types of light pollution:

- Light trespass.

- Over-illumination.

- Glare.

- Clutter.

- Sky Glow.

Measurement of light pollution and global effects:

Measuring the effect of sky glow on a global scale is a complex procedure. The natural atmosphere is not completely dark, even in the absence of terrestrial sources of light. This is caused by two main sources: airglow and scattered light.

At high altitudes, primarily above the mesosphere, UV radiation from the sun is so intense that ionization occurs. When these ions collide with electrically neutral particles they recombine and emit photons in the process, causing airglow. The degree of ionization is sufficiently large to allow a constant emission of radiation even during the night when the upper atmosphere is in the earth's shadow.

Apart from emitting light, the sky also scatters incoming light, primarily from distant stars and the Milky Way, but also sunlight that is reflected and backscattered from interplanetary dust particles (the so-called Zodiacal light).

The amount of airglow and zodiacal light is quite variable but given optimal conditions the darkest possible sky has a brightness of about 22 magnitude/square arcsecond. If a full moon is present, the sky brightness increases to 18 magnitude/sq. arcsecond, 40 times brighter than the darkest sky. In densely populated areas a sky brightness of 17 magnitude/sq. arcsecond is not uncommon, or as much as 100 times brighter than is natural.

To precisely measure how bright the sky gets, night time satellite imagery of the earth is used as raw input for the number and intensity of light sources. These are put into a physical model of scattering due to air molecules and aerosoles to calculate cumulative sky brightness. Maps that show the enhanced sky brightness have been prepared for the entire world.

Inspection of the area surrounding Madrid reveals that the effects of light pollution caused by a single large conglomeration can be felt up to 100 km away from the center. Global effects of light pollution are also made obvious. The entire area consisting of southern England, Netherlands, Belgium, west Germany, and northern France have a sky brightness of at least 2 to 4 times above normal (see above right). The only place in continental Europe where the sky can attain its natural darkness is in northern Scandinavia.

In North America the situation is comparable. From the east coast to west Texas up to the Canadian border there is very significant global light pollution.

Consequences of light pollution

- Energy waste.

- Effects on human health and psychology.

- Disruption of ecosystems.

- Loss of safety.

- Effect on astronomy.

Reducing light pollution:

- Improving lighting fixtures.

- Adjusting types of light sources.

- Re-designing lighting plans.

Answer 7

What is light pollution

Definition

Light pollution

is the alteration of light levels in the outdoor environment (from those present naturally) due to man-made sources of light.

(A peer-reviewed 2000 article where it was published with slightly different wording is [1]. Previous to that, confusing concepts of light pollution have been common, limiting it just to “adverse effects”, “skyglow” etc. This practice continues even now, unfortunately. Some consequences of such pollution (by light and of natural light) are welcome by some and disliked by others, some consequences are considered adverse by everybody. Many consequences are not known yet: the relevant discipline scotobiology [2] is just emerging. The most general consequence is a disruption of a day-night cycle as it had existed on Earth for billions of years.)

How it can be quantified

– absolutely

As for all pollutants, light added artificially to the environment can be measured by

concentration

of the pollutant in some volume of the environment (of air or water). For light, a convenient unit for this purpose is lumen per square metre (it can be further divided by speed of light to get a true volume concentration). It can be computed from a pair of fish-eye images (integrating the luminance over the full space angle). Seldom used for light.

emissions

– amount of pollutant released to the environment within a time interval by some source. For light expressed most easily as lumen seconds. On packaging of lamps (incandescent, fluorescent and other discharge ones), their nominal luminous flux (rate of emissions) in lumens is usually given.

For light as a pollutant, two additional properties are relevant: its direction and spectrum. Complete characterisation of rate of emissions (from any surface) or of pollutant influx (to any irradiated volume element) is given by a quantity called spectral radiance. It is a function of both direction and wavelength (or, alternatively, wavenumber, frequency or photon energy). Watt per steradian per square metre per nanometre (W.sr-1m-2.nm-1) belongs to its common units. From this quantity, the parameter “how bright is this spot” called luminance can be computed, integrating spectral radiance × spectral sensitivity of human daylight perception (photopic vision); its unit is candela per square metre.

In general, any radiometric or photometric quantity can be employed as a measure of light pollution in some situation. For example, any source of pollution (e.g., a single luminaire) can be characterised integrally (as a whole) by specifying how large luminous intensity it emits in each direction. This is an adequate parameter for very distant sources appearing as points. However, if a visible source is so close that it does not appear as a point, larger kinds (like long fluorescent tubes instead of small high-intensity discharge burners) with the same luminous intensity may be less polluting, as their luminance is lower (the same luminous intensity is produced by a larger surface).

Amount of pollutant hitting some surface is a useful integral measure in case of light. Per second and square metre, it it is measured directly by a luxmetre; the quantity is then illuminance, its unit is lux. The orientation of the surface element makes illuminance differ from direction-less pollutant concentration (luminance is integrated just over the proper half of the full space angle and multiplied by cosine of angle of incidence to the surface element – then light tangential to the surface makes no contribution to its illuminance). Per whole area and time interval, it can be expressed in lumen seconds.

– relatively

Light is always present naturally. Thanks to that, there is a convenient way of expressing light pollution by giving the ratio:

man-made part of any photometric or radiometric quantity  

natural part of the same quantity  

In most cases, it's preferable to express pollution this way: as a dimensionless number rather than by photometric units. An amount of light which is a serious pollution at night may be negligible at noon. Even when there is a sharp boundary between the polluted and unpolluted part of a visual scene, people do not notice the pollution if the artificial contribution to the luminance of the polluted spot is below one per cent of its natural luminance (assuming it holds even for “blue luminance”). In many cases, even ten per cent increase of luminance over the natural value may not be noticed (if there is no sharp boundary between areas of differing luminance) – because of that, pollution which is less than 10 % of natural light level is often considered as insignificant.

For example, people are concerned with man-made increase of light amounts from clear night skies (a typical reported quantity is sky luminance in zenith, or the man-made increase of that luminance divided by natural luminance), because of the loss of visibility of stars. Relative pollution may be however much higher under overcast sky, implying a huge disruption of the natural environment.

Let's compute it. Under overcast moonless night sky, the natural amounts of light are about ten times less than under clear sky. If the absolute amount of artificially added light would be the same in both cases, in relative terms it would therefore cause ten times more pollution under overcast sky, locally. However, far from emission sources, even the intruding absolute light amounts can rise, as the light cannot escape to the space and is reflected back to the ground by clouds. This can be further amplified by snow. Then the same emissions, which cause increase of incident light amounts say by 100 % under clear sky (it means the man-made and natural parts are about the same, pollution is 1 in relative terms, very significant and conspicuous), cause relative pollution of at least 100, hundred times more than under clear sky! (In the remote areas of the largest Czech national park the relative concentration of the pollutant (light) under overcast sky was three hundred times larger than under clear sky, as measured in winter 2005.)

The radiometric or photometric quantity can be itself a ratio, a number with no unit, like contrast. Then the pollution by man-made light can be expressed even as a decrease of a quantity from its natural value. It is adequate to say that stars get dimmer due to light pollution: it means their contrast to the surrounding sky becomes lower, when the luminance of that sky is increased due to man-made light. To compute it exactly, each star can be ascribed an element of a space angle, which is perceived as a point by our vision (depending on acuity, sky luminance and brightness of the star, it can be a circle with a diameter of 1′ to 5′ for young people with good eyesight). So we can speak about luminance of a star, like about luminance of any target which should be seen. Then the (Weber's) contrast of target is

luminance of the target − luminance of the background  

luminance of the background  

– doubly relatively

Ratio of contrasts in polluted and unpolluted situation is the best measure of pollution, as regards visibility of faint lights. They include stars and another celestial phenomena, fireflies and glowworms, or plentiful faint sparkles of light (bioluminiscent plankton) which are so wonderful in sea, but mostly unknown to population in areas where strong artificial lighting is ubiquitous.

It is not just a matter of their visibility for people. In case of luminous insects, in polluted environments they don't recognise each other over long distances, don't find mates, cease to reproduce and their populations collapse eventually (this is common in towns and cities, unfortunately). For marine life, the ecosystem consequences of loss of visibility of bioluminiscent signals on moonless or overcast nights are not understood yet, but can hardly be negligible.

Reduction of contrast can wipe out whole terrestrial panoramas, even the very outlines of giant mountains ([3]).

– with special regard to physiology of vision

Vision does poorly register absolute levels; due to adaptation, it adjusts itself to the prevailing light levels. E.g., stars are perceived as dimmer if some other, additional light comes to our eyes. This added light may come from spots of high luminance, as from luminaires, windows of lit rooms, vehicle lights and outdoor surfaces illuminated on purpose. Stars become invisible in urbanised environments not just because of increased sky luminance, but also because of glare (including veiling luminance produced by dispersion of light inside eyes) and mostly because of changed adaptation of vision due to increased light levels. In fact, the sky may be perceived as black or very dark from such heavily polluted sites, unlike in nature where vision adapts to its luminance during twilight and night: natural clear night sky is never dark between the stars, being the main source of illumination of terrestrial landscape.

So, light pollution not only diminishes contrasts, but due to animal and human vision getting adapted to artificially increased light levels, light pollution reduces the number of photons registered at retina from the natural sources. Physiologically, such sources become fainter not just in relative, but even in absolute terms. This further reduces their visibility, as more contrast is needed if are to be noticed (contrast sensitivity is worse at the bottom end of the span of perceived luminances than in its middle).

Where the direction or a spectrum plays a role

With closed eyelids, we almost don't perceive direction of the incoming light, but it is still important: if it comes from one side only, we can turn to the other side (reducing illuminance of our face this way). Similarly, trees affected by acid deposits brought by a wind coming from west are less affected at thei