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Dew is water in the form of droplets that appears on thin, exposed objects in the morning or evening. As the exposed surface cools by radiating its heat, atmospheric moisture condenses at a rate greater than that at which it can evaporate, resulting in the formation of water droplets.
When temperatures are low enough, dew takes the form of ice; this form is called frost.
Because dew is related to the temperature of surfaces, in late summer it is formed most easily on surfaces which are not warmed by conducted heat from deep ground, such as: grass, leaves, railings, car roofs, and bridges.
Dew should not be confused with guttation, which is the process by which plants release excess water from the tips of their leaves.
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Formation
Water will condense into droplets depending on the temperature. The temperature at which droplets can form is called the Dew Point. When surface temperature drops, eventually reaching the dew point, atmospheric water vapor condenses to form small droplets on the surface. This process distinguishes dew from those hydrometeors (meteorological occurrences of water) which are formed directly in air cooling to its dew point (typically around condensation nuclei) such as fog or clouds. The thermodynamic principles of formation, however, are virtually the same.
Occurrence
Sufficient cooling of the surface typically takes place when it loses more energy by infrared radiation than it receives as solar radiation from the sun, which is especially the case on clear nights. As another important point, poor thermal conductivity restricts the replacement of such losses from deeper ground layers which are typically warmer at night. Preferred objects of dew formation are thus poor conducting or well isolated from the ground, and non-metallic or coated as shiny metal surfaces are poor infrared radiators. Preferred weather conditions include the absence of clouds and little water vapor in the higher atmosphere to minimize greenhouse effects and sufficient humidity of the air near the ground. Typical dew nights are classically considered to be calm because the wind transports (nocturnally) warmer air from higher levels to the cold surface. But, if the atmosphere is the major source of moisture (this part of dew is called dewfall), a certain amount of ventilation is needed to replace the vapor that is already condensed. The highest optimum wind speeds could be found on arid islands. If the wet soil beneath is the major source of vapor, however (this part of dew is called distillation), wind always seems to be adverse.
The principles of dew formation do not strictly constrict its occurrence to the night and the outdoors. They are also working when eyeglasses get steamy in a warm, wet room or in industrial processes. However, the term condensation is preferred in these cases.
Measurement
A classical device for dew measurement is the drosometer. A small, artificial condenser surface is suspended from an arm attached to a pointer or a pen that records the weight changes of the condenser on a drum. Besides being very wind sensitive, however, this, like all artificial surface devices, only provides a measure of the meteorological potential for dew formation. The actual amount of dew in a specific place is strongly dependent on surface properties. For its measurement, plants, leaves, or whole soil columns are placed on a balance with their surface at the same height and in the same surroundings as would occur naturally, thus providing a small lysimeter. Further methods include estimation by means of comparing the droplets to standardized photographs, or volumetric measurement of the amount of water wiped from the surface. It has to be kept in mind that some of these methods include guttation, while others only measure dewfall and/or distillation.
Significance
Due to its dependence on radiation balance, dew amounts can reach a theoretical maximum of about 0.8 mm per night, measured values, however, rarely exceeding 0.5 mm. In most climates of the world, the annual average is too small to compete with rain. In regions with considerable dry seasons, adapted plants like lichen or pine seedlings, benefit from dew. Large-scale, natural irrigation without rainfall, such as in the Atacama Desert and Namib desert, however, is mostly attributed to fog water.
Another effect of dew on plants is its role as a habitat for pathogens such as the fungus Phytophthora infestans which infects potato plants.
In Greek mythology, Ersa is the goddess of dew.
Artificial harvesting
Several man-made devices such as antique, big stone piles in the Ukraine, medieval "dew ponds" in southern England, or volcanic stone covers on the fields of Lanzarote have been thought to be dew-catching devices, but could be shown to work on other principles. At present, the International Organization for Dew Utilization is working on effective, foil-based condensers for regions where rain or fog cannot cover water needs throughout the year. An interesting strategy for harvesting dew on large scale for drinking water was proposed in 1980.[1]
Large scale dew harvesting systems have been made by Indian Institute of Management Ahmedabad (IIMA) at coastal semi arid region Kutch. These condensers can harvest more than 200 litres (on average) of dew water per night for about 90 nights in the dew season October-May. The research lab of IIMA has shown that dew can serve as a supplementary source of water in coastal arid areas.
Morning Dew water in early medince
There is a fascinating history of morning dew being used in early chemistry, called alchemy. It was found to be remarkably medicinal, and was even used by the father of modern medicine and chemisty Paracelsus. His full birth name was Aureleous Phillipus Theophrastus Bombast von Hoenheim. Few people have contributed as much to humanity and have received such little recognition for it.
There is also a book which can be found in many public libraries in the USA which contains a report on a man who lived to be well over 100 years of age and was active and youthful until the end. He collected morning dew and distilled it over 100 times before consuming it was an Elixir of Life.
The health benefits of drinking morning dew are undeniable, and even the Rosicrucian Order is named after dew. ROS means dew, CRUCIS means crucible or flask. This is why the proper symbol for the Rosicrucian Order is a picture of a rose flower with dew droplets on the petals.
The Order of the Golden Dawn is a secret society which was formed by members of the Rosicrucian Order who split off to form their own group. The name was chosen because it represents their primary source or main ingredient for their Elixir of Life and Philosopher's Stone which can turn lead to gold.
There is also another society called the Order of the Morning Star, which refers to the planet Venus which shines like a bright star and rises only just before sunrise, which happens to be when morning dew is falling at it's highest levels.
From the manuscripts of these secret societies, we find a recipe for an Elixir of Life which was believed to cure every disease and be a veritable panacea, or 'cure all'. Dew was seen as the collector of moon light, and was represented by the metal silver. Sea salt was seen as he collector of sun light because over 80% of the earth is sea water exposed to the sun. By simply dissolving natural unprocessed sea salt in morning dew until it reaches it's saturation point and can hold no more, then digesting for a few weeks at 120°F (named by the alchemists the bath of Belneo Mary and abbreviated B.M.), a black powder forms and precipitates. The black powder is removed and dried, then heated until it turns gray. It is then placed in new morning dew water, and again heated for several weeks until it lightens further. After several cycles of these digestions and calcinations of the material, it becomes snow white. It can then be heated on a silver plate, and will melt like wax.
It is a powerful medicine, and extremely potent. Only 5 drops per day would be prescribed to cure even the most wicked of disease, and also wonderfully improves the mental functioning.
But the alchemists also found that this white liquid is able to dissolve gold and silver like ice in warm water, if the metal be in thin leaf form. And once digested, the metal solution becomes blackened, then goes through color changes to end as a beautiful red if gold is used, or white if silver was used. By this method a stone is made which is able to perform the seemingly impossible feat of transmutation of lead to gold or silver.
What is even more incredible is the fact this "stone" will begin to glow like a hot coal if made from gold and simply digested 7 times with the white dew/salt which dissolves it and putrefies it. And if made from silver, it begins to glow with a white fluorescent light.
However, a few of the old texts indicate the alchemists did not mean gold and silver as we know them, but instead meant antimony for gold, and bismuth for silver. Some also wrote that both the white and red stones should be combined to produce the true completed Philosopher's Stone, which will glow with a distinct ruby red gleam instead of the soft 'hot coal' orange glow of the red stone when it's alone. This stone is also heavier than lead because it contains bismuth, and thus fits well with the descriptions written down by the alchemists for the past eight centuries.
And so, because simply morning dew and sea salt are used to create the central "secret solvent" of alchemy which is the only thing one needs to make every medicine of alchemy (even superior extracts of herbs), it was said that alchemy is so easy it's child's play. But the way in which alchemists described the process in their books made it appear very dangerous and difficult work. Often they would describe this secret solvent as sulfuric acid which of course is very dangerous to do experiments with, but in reality their secret solvent is this strange compound made from nothing but harmless dew and salt.
References
External links
- OPUR (International Organisation for Dew Utilization)
- International Conference on Fog, Fog Collection and Dew
Wikipedia content modification information:
- This page was last modified on 12 October 2008, at 12:24.
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