Dust
Dust is a general name for minute solid particles with
diameter less than 500 micrometers 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 , under some circumstances it can be an explosion hazard.
Encyclopedia
Dust is a general name for minute solid particles with
diameter less than 500 micrometers 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 , under some circumstances it can be an explosion hazard.
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.
House dust
The dust which collects in houses is composed of atmospheric dust combined with dust generated by the inhabitants, mostly from sloughed
skin cells. It can be removed with a
broom, dusting cloth,
vacuum cleaner or by a swipe of one's hand. In average, approximately 6 mg/m
2/day of house dust are formed in private households.
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 devices such as dusters and vacuum cleaners.
However, technological approaches to the removal of dust are offset by the fact that many energetic devices produce a commensurate form of pollution, usually ozone which are harmful to the body at malicious doses. Moreover, 'dusting' the house may often amount to little more than making much of it airborne, thus more capable of entering the human body than it otherwise would be, dirtying carpets or filming up furniture. With this in mind, perhaps the best form of dusting is simply opening windows and allowing a breeze to blow through, or to remove it manually, ensuring as little of as possible escapes the dust bin.
House dust mites, often found in fibers like carpets and beds, feed on the organic components of house dust. Their faeces, in turn, become part of house dust and can provoke allergic reactions in humans.
Dust in outer space
Cosmic 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.
Dust in fiction
- In Philip Pullman's bestselling series His Dark Materials, dust plays an important part by creating a connection between different worlds.
- In the TV comedy Little Britain is a character-based BBC [i] radio [i] and television [i] sketch show [i] written by...
, Fat Fighters group leader Marjorie Dawes distinctively instructs the dieters to eat dust as it is 'low in fat'.
- In JM Barrie's children's novel Peter Pan, "pixie dust" is a substance used to help create magical effects.
- In Clark Ashton Smith's short horror story "The Treader In The Dust" a scholar unwittingly calls forth a demon which personifies dustiness.
- In Hal Clement's short science fiction story "Dust Rag", two astronauts struggle with dust that stuck to their helmets, blinding them.
Dust in religion
In the
Bible:
- In Genesis 3:19, God--following The Fall, Adam and Eve's transgression--states to the couple :
- By the sweat of your brow you will eat your food until you return to the ground, since from it you were taken; for dust you are and to dust you will return. [Emphasis added]
This latter clause is used in the
Ash Wednesday service in some churches for the administering of ashes.
- I will make your offspring like the dust of the earth, so that if anyone could count the dust, then your offspring could be counted.
See also
Reference
- Holmes, Hannah; The Secret Life of Dust. Wiley. ISBN 0-471-37743-0
Sources
