All life on the earth depends on the sun for heat and light. The development of life on the earth was made possible by the steady flow of light and heat from the sun. Life would be endangered if the sun’s heat and light were to vary: it would be too hot or too cold to live. Life also depends on the sun for food. The heat of the sun is trapped by the atmosphere which lets sunlight through to the surface of the earth. The light warms the earth but the heat it creates cannot easily pass through the atmosphere into space. This is known as the "greenhouse" effect. It is what happens when the glass roof lets the sunlight in to heat the plants in the greenhouse but it passes back through the roof only very slowly. All living things, both plants which make their own food through photosynthesis (they combine energy from sunlight with carbon dioxide from the air and water from the soil to make food). In the process they give off oxygen. Men and animals breathe this oxygen released by the plants and exhale the carbon dioxide which in turn is used by plants. Sunbath is the exposure of the body to sunlight or to sun lamps. Sunlight is made up of many different kinds of light rays. Infrared ray penetrate deeply into the body. They benefit the circulatory system and the muscles. Ultraviolet rays are chiefly absorbed by the skin and may cause sun burns and tanning. They also caused chemicals in the skin to produce Vitamin D, the sunshine vitamin. Sun lamps produce ultraviolet rays. The importance of the Sun was realised by the ancient peoples of India, Egypt and Greece. They worshipped it, made offerings to it and built temples to honour it. Today we acknowledge the sun as a source of light, heat and other kinds of energy. Life of men, animals and plants depends entirely on the energy of the sun. As we explained earlier, plants use sunlight to make their own food and in the process oxygen is released. Our infinitesimal position in the universe can be gauged from the fact that the life giving sun is only one of the billions of stars in the universe.

Sun Bathing
Sun gives warmth. Sun gives light. Sun gives colour to the sky. The change in the colour of sky when the sun is rising or when it is setting is vivid and it is different on different days and different at all moments. The feeling is exhilarating, seeing the sun rise on the hills, specially in Nagarkot in Nepal when actually you see the sun rise from below to the top above the seven hills one on which is Everest. The sun dipping in the sea has its own charm. When the sun sets it acquires a colour apart from its life-giving qualities.

The sun can be blazing and hot in summer in the deserts of Rajasthan. The air is hot as if it is blowing straight from the oven. It can burn the skin and give sun-stroke. It is the energy source of all life. Above all it is most important for our overall immunity and physical and emotional stability.

The Sun God is worshipped by Hindus. They offer water and prayers to the sun every morning after bath. The Sun is important for the very existence of life on earth: the plant life, marine life and animal life. The effect of the rays of the sun directly spreading on the human body, with which we are here concerned, may be of some nuisance to us in the tropics.

The effect of sunlight is two-fold as it causes:

1. Photochemical reactions; and
   
2. Heating effect

Sunlight is important for a proper growth, specially of our young ones. We know now that the solar ultraviolet radiation is necessary for synthesis of calciferol, the forerunner of vitamin D. Calciferol is released into the blood stream by the skin. This hormone is released when sunlight falls on the skin. Without calciferol not enough calcium would be laid in growing bones. Where it is not available, one comes across crippling deformities and rickets. Adequate sunlight is necessary for a proper growth of bones and the prevention of rickets.

The photochemical effects are restricted to limited spectrum region. The vision for example falls between approximately 0.4 m and 0.65m wave lengths of sun light rays which is important part of sun light. When sun light reaches the surface of the earth it passes through atmosphere. The ozone layer of atmosphere absorbs the ultraviolet and infra red rays are absorbed by water vapour, smoke, dust, gas molecules, water drops, etc. This foreign matter effects the quality of sun light.

Solar radiation may be blocked by many means. Among them is industrial smog seen in Mumbai and London and other polluted places. The long dark winter of North India and many North European countries, also leads to a forced and prolonged confinement of infants indoors during the winter. This affects their health.

In 1908, Theobald Palm, an English Medical Missionary who went to Japan was surprised to find the absence of rickets among the Japanese exposed to sunlight. Harry S. Hutchinson who conducted an investigation in Mumbai in the beginning of the century, found no rickets among poor Hindus who ate poor and inadequate diet but who worked outdoors all the day and while at work left their infants at some nearby site in the open air. In contrast, he found that rickets was common among wellfed members of other castes and upper class Hindus, whose women normally married at the age of 12 and whose offsprings usually remained with their mothers for the first 6 months of life in semidark rooms in the interior of the house.

Hutchinson concluded due to lack of sunlight, fresh air and exercise that children suffered. He proved the point by removing 10 children from enclosed "purdah" environments and keeping them out in the open air. They were all cured. Rickets cause swelling at the end of the long bones. Growth is retarded by the failure to make new bone. Due to defective mineralization, the bones become soft and weak and develop curvatures.

The human skin can generate an adequate amount of vitamin D if exposed to sufficient ultraviolet irradiation. However in countries with limited sunlight or where the population dresses in a fashion that reduces exposure to sunlight, the circulating levels of vitamin D metabolites are often low. This well explain why osteomalacia and rickets are common in Great Britain, Scandinavian countries, Middle East and India than in the United States.

To avoid rickets and osteomalacia, give plenty of milk to children and expose them to sunlight. Osteomalacia has been observed in 25 to 30% of bone biopsies among elderly patients who have suffered hip fracture in Scandinavia and Great Britain. Most likely this is because vitamin D intake and reduced sunlight exposure. Rickets among children are due to lack of vitamin D. Osteomalacia among the elderly is also due to lack of vitamin D. The prevention and cure of rickets by the formation of vitamin D through the skin by sunlight is of course firmly established.

Sunbathing has been advocated for keeping the cold away, developing immunity and robust health. Heat is soothing. When we take a sun bath it helps to relieve body pain and is relaxing. The effect of ultraviolet rays on common cold is well known. A group of subjects exposed to ultraviolet radiation reported about 40% lesser colds.

Sunbathing in olden times, was prescribed for tuberculosis. The beneficial effect was due to sunbathing and a general improvement in the regimen. After the manufacture of anti-tubercular drugs, generally a change of place or stay in a sanatorium for a few months is not prescribed. Sunbathing is liked by Westerners who on any sunny days take a holiday. All empty spaces and parks get filled with sunbathers.

The ultraviolet rays pass through the ozone layer of atmosphere its major portion gets absorbed. At mid day, when the sun is at ninety degrees it passes through much thinner layer of atmosphere and also thinner layer ozone. The content of ultraviolet rays is excessive and can cause sun burn. Before 8 a.m. or after 4 p.m. when the sun is at an angle it passes through a much thicker layer of atmosphere and ozone. So the content of ultraviolet rays is less and sufficient for body needs. The ultraviolet rays are needed for the formation of vitamin D in the skin. The pro-vitamin D in the human skin is dehydrocholesterol, and it is converted to vitamin D by the help of ultraviolet rays. So sunbathing in the morning or evening hours just sufficient for the vitamin D formation and not sufficient to burn the skin. This is the right hour for sunbathing.

The sun’s rays when they pass through the window glass have most of its ultraviolet content absorbed. In winter, sunbathing can be enjoyed anytime of the day behind a window glass, thus avoiding bad effects of excessive ultra-violet rays. The soothing and relaxing effect of the sun is due to its heating effect. We have a feeling of well being during sun bathing. Heat reduces pain in the body and relaxes muscles. This way you can also avoid the cold draft due to high velocity of wind. The effect of sunbathing will depend upon the clothing. White cloth reflects sunrays and so it has a cooling effect. If clothes are dark they absorb most of the heat and have a warming effect.

Tanning
It is a common practice among the whites to sunbathe for tanning their skins. After regular sunbathing their skin takes a dark tan which they consider makes them look more beautiful. Europeans do prolonged sunbathing to darken their skins faster.

Melanin is the pigment in the skin which gives a dark colour. Among the whites melanin pigments are present in the deeper layers of the skin called the malpighian layer. We went to Gorai beach in Mumbai (Aug. 97). We spent a few hours on the beach in the afternoon when it was very hot. There was high tide. The exposed skin of the body, particularly around the neck and shoulders reddened considerably, was itchy and we were very uncomfortable with a burning sensation. A few days later the affected skin peeled off by bits, as it healed. It is common knowledge that exposure to midday summer sun results in the reddening of the skin. After a day or so the erythema fades gradually and is replaced by brown colouration due to accumulation of melanin pigments, this well call "sun-tan". About 20 hours after exposure to ultraviolet rays, some of this melanin begins to migrate towards the surface. Following this there is production of new pigments in the basal cell layer, thus the skin starts getting darker after regular sunbathing. When these people return to work after holidaying in the sun the skin remains tanned for a few weeks. Thereafter the melanin pigments becomes much lighter. But they become darker if exposed to ultraviolet rays for a few days.

It exposed too long there may be some blistering and peeling off of the superficial layer. This is called sun-burn. Among the Negroes the sun burn is much less severe and erythema may be slight due to the presence of excessive pigments in the skin. The idea of sunlight is good for you is so established in public mind that an overdose on the part of many seems almost inevitable. It will be worth remembering that sun bathing is good for you, but in excess can be bad.

In all parts of the world they are trying to harvest the cheap source of energy from the sun. Why not we start harvesting the cheapest medical aid from the sun. If the skin is subjected to increasing intensities of heat the sensation of warmth, heat and pain are elicited successively. The maximum intensity of sunlight is sufficient to produce the sensation of heat but does not produce pain except after sunburn. The amount of radiant energy required to produce skin damage is about 10 times than that required to produce pain. This is why a direct exposure to sun never produces burn. Pain and burning can occur if the sunlight is focussed with a lens. When a person is sunbathing he usually feels the sensation of mild warmth from sunlight, unless the skin happens to be already irritated by sunburn.

The body gives out a certain amount of heat all the time from its own metabolism. The channel of loss is conduction convection (evaporation of sweat and moisture from lungs) and radiation. Thus when we are exposed to ice we lose heat. We gain it from hot rocks. The same is true of the solar energy. When the sun is too hot we receive heat from the sun. Part of it comes directly and part of it after getting reflected from the terrain.

If a man walks in desert at the rate of 3 miles per hour he will lose approximately 882 gm of water in one hour. This is why those having to work in a hot climate feel thirsty most of the time. Humidity also makes a lot of difference. If sunbathing on the rock or near green foliage, the temperature will be low near the green foliage than on the rock due to the evaporation of water from greenery. Evaporation adjusts itself due to sweating in such a way that the body temperature does not rise excessively.

There is some confusion over whether the protection of the body from the sun is only done by the formation of melanin pigmentation. One more important factor comes into reckoning. That is the thickening of the most superficial layer of skin called epidermal thickening. The result of the action of the ultraviolet radiation on the skin is rapid. It causes proliferation of the two layers of epidermis - corneum and malpighian. The thickening of corneum results in marked decrease in the amount of sunburn reducing radiation that reaches the malpighian layer. Thus the effectiveness of corneum as filter is increased. The skin becomes less sensitive to sunburn. Among the black skinned the thickening of the corneum is the principal means for protection of the skin from sunburn apart from melanin formation. Corneum in them is much thicker. This is why they are less susceptible to sunburn. Skin cancer is caused use to prolonged and excessive exposure to sun. This is more common among the white skinned people and less in negroes.

Eyes
The eyes are our most prized possession. We have to be careful no to harm our eyes while sunbathing. If the sun’s rays reach in a big quantity to the image producing screen of the eyes, the retina, it may get damaged. Our elders advises us not to look at the sun eclipse directly. It could cause eclipse blindness. When we look directly into the sun or in bright sunlight we may get pain in the eyes or have disturbances of vision, photophobia (fear from light), congestion of conjunctiva., excessive secretion and swelling depending upon the extent of injury. Such symptoms may also occur when the sun is bright over a snow field. When there is a good deal of diffused reflection of sunlight that reaches the eyes it may lead to "snow blindness". Normally, the wave lengths of the sun’s rays which can cause damage to the retina are absorbed in superficial layers of the eyes and do not cause any damage.

When the sun is bright it is better to wear good quality sunglasses. These should be designed in a way that they reduce the total amount of energy reaching the retina. It is not true that ultraviolet rays can cause cataract. This however can be brought about by lower temperature sources such as glass blowers furnaces which we call "glass blower’s cataract". It has more emission of infrared than sunlight.

The sun has many good effects on the body apart from the environmental factor. It influences the temperature of wind and ocean currents. It has its effect on rainfall and most important of all photosynthesis of plants.

Relax as you Sunbathe
You can mix sunbathing with relaxation. Lie in the sun, in a park, a mountain or a beach, near the lake or river, any place of your choice. It should be secluded and quiet. Remove the maximum amount of clothes as possible. Find a suitable place, lie down, comfortably. Take three deep breaths slowly deep in and out. Exhaling completely. As you exhale feel that you are exhaling out your tension. You feel that the sun is slowly warming the body. The air is clean and fresh and you can feel the breeze touching the body and flowing over it. You could listen to the musical sound of nature. The gurgling sound of water, the rustling of the breeze and may be, now then, a bird chirping. You cannot do anything else, but allow the nature outside and nature inside the body bring their gift to you, the gift of relaxation and the gift of recuperation. The gift is for you. You have earned it by virtue of your being there.

Notice the warmth of the sun on the forehead. It soothes the muscles of the forehead and the forehead and the scalp. Feel the warmth entering the muscles around the eyes, the facial muscles and the jaw. Let the warm relaxation flow down the body, over the shoulder, arms, over the chest, back, hips, thighs, calves and feet. Feel the relaxation covering you from head to toe in a warm golden glow. This is the protective covering against the pressures of the world and your own thoughts.

Shift your attention to the area of body about which your are concerned. Take a deep breath in and out. Feel you are breathing in and out through this, releasing all the tension in the area, allow the muscles to relax. Feel the blood vessels dilating, more blood flowing, more oxygen and healing minerals reaching the area. Feel all the toxins, wastes and deformed cells flowing out and being carried away in the blood. The affected area getting cleaner smoother and the pain gradually going down. Use all your will power to heal your self, let tension and exhaustion flow out and let the body be filled with relaxation, warmth and let it become cleaner and purer. Stay in the sun for half an hour, at least 15 minutes if you are in a hurry. Rouse the body gradually, open the eyes, stretch the body, see the beauty around you, sit down, wait for one minute more, now you are ready for the next important task of the day. You will be surprised to discover the mind’s capacity to heal and protect you. You will feel the soothing warmth of the sun helping your mind and body to do it better.