In the 1980s a global dark-sky movement emerged with the founding of the International Dark-Sky Association (IDA). Awareness of the deleterious effects of light pollution began in the second half of the 19th century, but efforts to address its effects did not begin until the 1950s. It is most severe in highly industrialized, densely populated areas of North America, Europe, and Asia and in major cities in the Middle East and North Africa like Tehran and Cairo, but even relatively small amounts of light can be noticed and create problems. Its sources include building exterior and interior lighting, advertising, outdoor area lighting (such as car parks), offices, factories, streetlights, and illuminated sporting venues. Light pollution is a side-effect of industrial civilization. Light pollution competes with starlight in the night sky for urban residents, interferes with astronomical observatories, and, like any other form of pollution, disrupts ecosystems and has adverse health effects. Adverse consequences are multiple some of them may not be known yet. The term is most commonly used in relation to in the outdoor environment and surrounding, but is also used to refer to artificial light indoors. Light pollution is the presence of anthropogenic artificial light in otherwise dark conditions. However, because it is a manmade phenomenon, addressing its impacts on humans and the wider ecological systems of Earth involves vast societal complexities that overlay light pollution with political, social, and economic considerations. Solutions to light pollution are often easy steps like adjusting light fixtures or using more appropriate lightbulbs. Globally, it has increased by at least 49% from 1992 to 2017. Ī major side-effect of urbanization, light pollution is blamed for compromising health, disrupting ecosystems, and spoiling aesthetic environments. The area affected by artificial illumination continues to increase. It has been estimated that 83 percent of the world's people live under light-polluted skies and that 23 percent of the world's land area is affected by skyglow. Īlthough this type of pollution can exist throughout the day, its effects are magnified during the night with the contrast of darkness. Light pollution can be understood not only as a phenomenon resulting from a specific source or kind of pollution, but also as a contributor to the wider, collective impact of various sources of pollution. In a descriptive sense, the term light pollution refers to the effects of any poorly implemented lighting, during the day or night. And images showed Comet 67P to be a rugged object with lots of activity shaping its surface.Light pollution is the presence of unwanted, inappropriate, or excessive artificial lighting. Rosetta detected building blocks of life on this comet, too. Rosetta dropped a lander on the nucleus, then orbited the comet for two years. Rosetta, a mission of the European Space Agency that had several NASA instruments onboard, studied Comet 67P Churyumov-Gerasimenko. Scientists found those particles to be rich in hydrocarbons, which are chemicals we consider the “building blocks” of life.

NASA’s Stardust mission collected samples from Comet Wild 2 (prounounced like “Vilt two”) and brought them back to Earth. In recent years, though, several spacecraft have had the chance to study comets up close. But it wasn't possible to get a good view of a comet nucleus from Earth since it is shrouded by the gas and dust of the coma.

People have been interested in comets for thousands of years. The ion tail (blue) always points directly away from the Sun, while the dust tail (yellow) points away from the Sun in a slightly different direction than the ion tail. Both tails are always directed away from the Sun. A comet has two tails that get longer the closer it gets to the Sun.

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