Dust

From Free net encyclopedia

For other uses, see Dust (disambiguation).

Image:Laptop dust.jpg Dust is a general name for minute solid particles with diameter less than 500 micrometers (otherwise see sand or granulates) and, more generally, for finely divided matter. On Earth, dust occurs in the atmosphere from various sources: soil dust lifted up by wind, volcanic eruptions, and pollution are some examples; airborne dust is considered an aerosol and can have a strong, local radiative forcing on the atmosphere and significant effects on climate. In addition, if composed of a flammable substance (such as flour), it can be an explosion hazard. The physical behavior of dust follows laws that are not always comparable with that of solid or fluid matter. For example, the pressure on a box full of dust need not be uniform.

Dust is responsible for the lung disease known as Pneumoconiosis, including black lung disease that occurs among coal miners. These have resulted in a number of laws regulating environmental standards for working conditions.

1 House dust
2 Dust in outer space
3 See also
4 Reference

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House dust

Image:Dust.jpg The dust which collects in houses is composed of atmospheric dust combined with dust generated by the inhabitants, mostly from sloughed skin cells and fibers from clothing and coverings. It can be removed with a broom, dusting cloth, vacuum cleaner or by a swipe of one's hand.

House dust mites, often found in fibers like carpets and beds, feed on the organic components of house dust. Their feces, in turn, become part of house dust and can provoke allergic reactions in humans.

A variety of technology has been developed for the purpose of removing accumulated dust in the house. The air filter is frequently used on inlet of the air ducts to trap dust. These can be supplemented by air purifiers, including devices that employ ionization to trap dust particles. Accumulated dust is collected by means of dusters and vacuum cleaners.

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Dust in outer space

Dust is also widely present in outer space, where gas and dust clouds are primary precursors for planetary systems. The zodiacal light, seen in the sky at night, is produced by sunlight reflecting off particles of dust in orbit around the Sun. The tails of comets are produced by emissions of dust and ionized gas from the body of the comet. Dust also covers planetary bodies, and great dust storms are produced on Mars that can cover nearly the entire planet. Interstellar dust is found between the stars, producing diffuse nebula and reflection nebula.

It is thought that dust samples returned from outer space could tell scientists much about the early conditions in the solar system. Several spacecraft have been launched in an attempt to gather samples of dust and other materials. Among these was Stardust which flew past the comet Wild 2 in 2004 and landed a capsule filled with remains of the comet back in the US in January 2006. The Japanese Hayabusa spacecraft is attempting a sample return of dust collected from the surface of an asteroid.

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