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These skills allowed humans to harvest more of the sunlight than was possible through glycolysis alone http://www.airmax1pascher-fr.eu/ , and human population began to grow. During the Neolithic Revolution, the domestication of plants and animals further increased human access to solar energy. Fields devoted to crops were enriched by inedible plant matter, providing sugars and nutrients for future harvests. Animals which had previously only provided humans with meat and tools once they were killed were now used for labour throughout their lives, fueled by grasses inedible to humans. The more recent discoveries of coal, petroleum and natural gas are modern extensions of this trend. These fossil fuels are the remnants of ancient plant and animal matter, formed using energy from sunlight and then trapped within the earth for millions of years. Because the stored energy in these fossil fuels has accumulated over many millions of years, they have allowed modern humans to massively increase the production and consumption of primary energy. As the amount of fossil fuel is large but finite, this cannot continue indefinitely nike air max 1 pas cher , and various theories exist as to what will follow this stage of human civilization (e.g. alternative fuels, Malthusian catastrophe, new urbanism, peak oil). Cultural aspects Many people find direct sunlight to be too bright for comfort, especially when reading from white paper upon which the sun is directly shining. Indeed, looking directly at the sun can cause long-term vision damage. To compensate for the brightness of sunlight, many people wear sunglasses. Cars, many helmets and caps are equipped with visors to block the sun from direct vision when the sun is at a low angle. In colder countries http://www.airmax1pascher-fr.eu/hom[....]gris-nike-air-max-1-chaussures.html , many people prefer sunnier days and often avoid the shade. In hotter countries the converse is true; during the midday hours many people prefer to stay inside to remain cool. If they do go outside, they seek shade which may be provided by trees, parasols, and so on. Sunshine is often blocked from entering buildings through the use of walls, window blinds, awnings, shutters or curtains. Sunbathing Sunbathing is a popular leisure activity in which a person sits or lies in direct sunshine. People often sunbathe in comfortable places where there is ample sunlight. Some common places for sunbathing include beaches, open air swimming pools nike air max 1 bleu gris blanc , parks, gardens, and sidewalk cafs. Sunbathers typically wear limited amounts of clothing or some simply go nude. An alternative some use to sunbathing is to use a sunbed that generates ultraviolet light and can be used indoors regardless of outdoor weather conditions and amount of sun light. For many people with pale or brownish skin, one purpose for sunbathing is to darken one's skin color (get a sun tan) as this is considered in some cultures to be beautiful, associated with outdoor activity, vacationsholidays, and health. Some people prefer nude sunbathing so that an "all-over" or "even" tan can be obtained. Skin tanning is achieved by an increase in the dark pigment inside skin cells called melanocytes and it is actually an automatic response mechanism of the body to sufficient exposure to ultraviolet radiation from the sun or from artificial sunlamps. Thus, the tan gradually disappears with time nike air max 1 grise et verte homme , when one is no longer exposed to these sources. Effects on human health Main article: Risks and benefits of sun exposure The body produces vitamin D from sunlight (specifically from the UVB band of ultraviolet light), and excessive seclusion from the sun can lead to deficiency unless adequate amounts are obtained through diet. Excessive sunlight exposure has been linked to all types of skin cancer caused by the ultraviolet part of radiation from sunlight or sunlamps. Sunburn can have mild to severe inflammation effects on skin; this can be avoided by using a proper sunscreen cream or lotion or by gradually building up melanocytes with increasing exposure. Another detrimental effect of UV exposure is accelerated skin aging (also called skin photodamage), which produces a difficult to treat cosmetic effect. Some people are concerned that ozone depletion is increasing the incidence of such health hazards. A 10% decrease in ozone could cause a 25% increase in skin cancer. A lack of sunlight, on the other hand, is considered one of the primary causes of seasonal affective disorder (SAD), a serious form of the "winter blues". SAD occurrence is more prevalent in locations further from the tropics, and most of the treatments (other than prescription drugs) involve light therapy, replicating sunlight via lamps tuned to specific (visible nike air max 90 noir et rose femme , not ultra-violet) wavelengths of light or full-spectrum bulbs. A recent study indicates that more exposure to sunshine early in a person life relates to less risk from multiple sclerosis (MS) later in life.
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