Category Applied Science & Technology

Clouds are made of water droplets and dust in the atmosphere at altitudes of 1 to 16 km. While travelling through air, due to friction, the water droplets get electrically charged.

 Lightning occurs due to sparking between oppositely charged clouds – a high voltage spark rushes towards the ground (at zero potential) through moisture-filled air.

If any around based structure is on the path of the spark, the top of that structure is excited to a high electrical potential while its bottom (in contact with the around) remains at zero voltage. This high potential difference sets a very high current in the structure causing sudden heat generation in the material and destruction. But in flying aero-planes, there is nothing like a ground point which remains always at zero voltage.

Hence even if hit a lightning, the plane’s entire surface acquires the same high potential and due to lack of potential difference there is no current and hence no destruction.

           The mechanism of seeing in the dark involves two types of cells – rods and cones, in the eye. These cells are present in the light – sensitive innermost layer of the eye called the retina. They lie in front of a pigmented tissue layer. Cones are present in the area of greatest visual activity – fovea contrails, which lies at the centre of small yellow pigment spot behind the pupil. Rods and cones are present around the fovea.

            Cones are active under intense illumination, whereas rods are active in dim light. In the dark rods are sensitized by a pigment called Rhodospin or the visual purple that is formed within the rods. Rhodospin is bleaches by light and is reformed by the rods in darkness. Hence a person who steps from sunlight into a dark room experiences a blinding feeling till the pigments begin to form. This process takes around 30 minutes to reach maximum sensitivity.

            On completion the eyes become sensitive to low levels of illumination and are said to be dark-adapted. Meanwhile the cones adapt themselves to fainter light in the ambience of low intensity illumination, which may take around five minutes.

            The best example is finding our way to our seats in a movie theatre after the show begins. Initially there is a blinding feeling when we do not see anything. But later the cones in the retina get adapted to the light from the film screen, when we are able to find the seats; this is followed by adaption of the rods which enables us to see everyone around us.

          Mummies are embalmed bodies that have been preserved for thousands of years. The dead have been mummified with the help of good drying agents applied all over the body.

            Drying agents and other materials were stuffed inside the body to maintain its shape after removing the internal organs. The word mummy is derived from the Persian word mummia meaning bitumen because the black resin used for embalming the dead looked like bitumen.

            Three techniques of mummification have been discovered by Greek historians. The methodology was the same in all the three cases and the differences lie in the process of extraction of internal organs. Mummies belonging to 1570-1070 BC are still found to be in good condition.

            Actually in the process of mummification embalmers removed all the internal organs except the heart and kidneys. The brain was removed through the nostril using a hook. They soaked them in natron (a mixture of salt, sodium bi-carbonate and sodium carbonate). It was then bandaged and kept in jars. The internal cavities were stuffed with lines bags of sawdust, natron bags, and resin coated material.

            The nostrils and eyes were stuffed with linen rolls. Cedar oil, natron and purgatives were then smeared on the body to close the pores. After this, the body was wrapped in long sheets of fine line. Toes, fingers and limbs were separately wrapped and then the torso was wrapped up in several layers.

            A mask revealing the external features, made of pliable linen treated with resin was fixed on the face. According to ancient texts a complete treatment could take about 70 days. Though resin has burnt the skin of the dead body in many cases the hairs were seen to be intact.

            Human skin is made of four layers – the topmost layer is stratum cornium, followed by epidermis and sub-cutaneous layers. When mehndhi is applied on the skin, the red pigments present in it are transported along with water through the small pores in the stratum cornium. These pigments get trapped between the stratum cornium and epidermis. As the hand dries, the water evaporates leaving the pigments which impart the colour.

            In the case of the nail, the pigments are trapped between the horny plate-like cells which are piled in lamellar layers. The pores in the skin are larger than those in the nail. This actually accounts for the rapid fading of the colour in the skin compared to that of the nail.

  Any object will be stable in its position if the line drawn perpendicular to the ground from the object’s centre of gravity falls within its base.

            While walking on a rope, as the base is very thin (as thin as the rope), to be stable the artist has to move his centre of gravity appropriately. This he does by holding a bamboo pole horizontally or using an umbrella or just by spreading his hands.

            When the artist feels that he is falling to his left, he moves the pole to his right (and the vice versa) and counters the forces disturbing his balance and makes the centre of gravity fall within his base.

            Now one may ask, how does one sense these forces and maintain balance? This is achieved only by practice.

            According to the theory of rhythm perception, the perception of rhythm involves the motor system just as much as the sensory system. It postulates that a ‘beat’ is actually perceived as a movement.

            The theory then suggests that because a beat is perceived as a movement, the activation of a stereotyped behaviour such as tapping your foot in time with the beat is a natural extension of the way motor and sensory systems often work together to produce a percept.