Category Science

What are the seas of the moon?

               When we look towards the surface of the moon with the naked eyes, we observe some dark smooth regions. The earliest astronomers believed that these dark regions on the moon’s surface were covered with water like the seas on earth. It was Galileo who first studied these dark areas through his telescope in 1609 and concluded that these were the areas covered with water. Galileo also studied some bright rugged regions of the moon’s surface and found that the bright areas were highlands. The highlands catch the sun’s rays. The darker patches are low lying plain areas of moon. Therefore once these were thought to be seas of the moon.

               In the later centuries, with the development of better telescopes, it became evident that the “Seas of the moon” were not seas at all, but low-lying and completely arid basins or plains. However, they continued to be called “Seas”. Astronomers called the dark areas Maria, meaning “Seas”. Strangely enough, no extensive Maria occurs on the lunar far side, which is almost entirely covered by mountainous terrae formations.

               The Seas of the moon can be divided into two types: the circular shaped and the ones with irregular outline. The circular type Seas are generally surrounded by mountains. Mare Imbrium (Sea of showers) and Mare Crisium (Sea of crises) on the near side and Mare Moscoviense (Sea of Moscow) on the far side are of this type. The irregular seas, such as Mare Tranquillitatis (Sea of Tranquillity) and Oceanus Procellarum (Ocean of Storms) have no extensive bordering mountain walls.

               The lunar seas are paved with successive lava flows. These might have been formed by the collisions of high velocity giant asteroids or meteorites. This would have ruptured the surface or triggered off volcanic eruptions allowing vast quantities of lava to well up from the lunar interior. The surface is made up of much the same elements as are volcanic rocks on earth but they contain no water. From the analysis of Maria basalts collected by the Apollo astronauts, it appears that the filling of the maria basins took place about 3500 million years ago. The terrae are much older regions than the maria. Most of these high ranges border the maria.

 

How can you find out date with the help of stars?

               We see a large number of stars in the sky every night. Since the ancient times they have helped man in more ways than one. He used to find out direction with the help of the Pole Star. He developed astronomy by studying stars and planets. Man has been trying to know more and more about these stars. Powerful telescopes have been made to provide valuable information about the stars. It is also possible to tell the date with the help of stars. Do you know how?

               To find out the date, take a large sheet of paper and draw a circle of at least eight inches in diameter. Divide this circle into twelve equal parts — just as a clock face is divided. On each division of the circle, write the name of each month. At the position of 12’O clock write the month of March. Keeping the usual order of the months, write them anticlockwise. Mark the centre of the circle as ‘North Star’. Imagine that the distance on the circle between each month is divided into 30 smaller divisions.

               Take your diagram outdoor on a clear night. Hold it in such a manner that the month of March is at the top. Imagine the diagram in the sky, with the North Star as the centre. Note the location of the Big Dipper. Now draw the Big Dipper on your diagram in the same location as you find it in the sky. Having done this, draw a straight line from the pointer to the North Star. This line will pass through the circle at a point that will indicate the date on which you are making your observation. If the line passes half way between the June and July positions on the circle, it is the day of 15th June. Of course, unless you have drawn a very large circle, it will be difficult to estimate 30 divisions between months on the circle. However, you can come within a few days of the exact date.

               The important thing is to note that on the diagram you have made on any particular date at midnight, the pointers are in line with that date on the star calendar. This is how we can find out the date by the stars.

Why is it difficult to see things immediately when we enter a dark room?

               It is a matter of common experience that when we move into a dark place from a lighted one we are not able to see things clearly immediately. First they appear blurred and then gradually start appearing clearly. Do you know why it happens so?

               We see things in bright light as well as in dim light. The pupil of our eye adjusts its size according to the brightness of light. When we are in dim light the pupil expands to let more light enter the eye. When we are in bright light, the pupil contracts. But when we move into a dark room from bright sunlight, the pupil takes some time to dilate. Therefore it takes some time for things to become visible clearly.

               There is another important reason for this. The inner most layer inside our eye is called retina on which images of objects are formed. But we do not see the object until light-sensitive nerve endings on the retina send the brain a message along with the optic nerve. The coloured part of the eyes is called iris. This can open and close to let more or less light pass through the pupil. The retina is composed of many cells called rods and cones. These rods contain a purple-coloured substance called rhodopsin. When light coming from an object falls on the retina, it splits rhodopsin into two substances. The splitting of rhodopsin produces electrical signals which go to the brain and we see the object.

               If rhodopsin is continuously decomposed by the light entering our eyes, a time should come when the whole stock of rhodopsin would be decomposed. And in this condition the person would go blind. But actually this condition is never reached because it is simultaneously decomposed and formed. Therefore, the retina never suffers from a complete loss of rhodopsin. In bright light, our eyes may feel fatigued, but will never become blind.

               A lot of rhodopsin is decomposed in bright light. In this condition if we suddenly enter a dark room we cannot see things clearly because the amount of rhodopsin is reduced. It takes some time for the rhodopsin to form again, after which things become clearly visible to us.

               In the opposite case, when we suddenly enter into bright light from a dark room, our eyes get dazzled. The reason is that in a dark room very less rhodopsin gets decomposed. But on a sudden exposure in bright light a lot of rhodopsin gets washed. And thus, the intensity of the electric impulses reaching the brain increases and our eyes get dazzled.

               For the production of rhodopsin vitamin ‘A’ is required. Deficiency of vitamin ‘A’ causes night blindness. Vitamin ‘A’ is found in leafy vegetables, carrots, eggs and milk. 

Why does milk spill out when boiled?

 

               When milk is heated it comes up in the container and finally spills out. Do you know why does it happen?

               Unlike water, milk is not a simple substance. It is a colloid and contains many substances in suspended form. It contains fat, sugar, starch, protein, vitamins and minerals. When milk is heated slowly, the proteins and fat get separated. Since they are lighter than milk they get collected on the surface in the form of a layer called cream.

               During heating some water gets converted into water vapour. As the upper layer of the milk is covered with cream, the vapour gets trapped under it. As the milk is heated further the water vapour expands and thick foam is produced on top. Finally, the trapped vapour pushes the layer up and in the process bursts through. As the vapour escapes, a lot of cream and milk spill out. 

 

 

 

                It is very easy to prevent milk from spilling. All one has to do is to provide a passage for the vapour to go out. For this we can keep a long spoon in the milk container so that water vapour is able to escape along the handle of the spoon. This prevents the vapour from getting deposited under the layer of the cream and thus spilling out of the milk. 

How is flood caused?

               If we look at the history of mankind, we find many instances of great floods. The primitive man settled in the valleys that were close to rivers as it not only met his basic need for water but also made the land fertile after floods.

               Now, the question arises — what is flood? Generally, when a river overflows its banks and water spreads out over the surrounding lands, a flood is said to have taken place. Floods can be terribly destructive. They often wash away the fertile top soil and may leave the land unfit for cultivation for years to follow or take a large toll of human and animal lives.

               However, some floods are very useful to man. For example, the annual flooding of the Nile without which the great Egyptian civilization could not have existed. In fact, Egypt is called “The Gift of Nile”. From the beginning, the annual floods of the river were the basic mechanism of the economy and set the rhythm of life on river banks for the Egyptians.

               But, what causes floods? Sometimes rainfall is unusually heavy and the river banks may not be able to contain it. Water from other streams or reservoirs also feed the rivers. Erosion of soil around river banks due to wanton deforestation also causes flood. Combined with all these factors, the river overflows. We also know that most of the rivers build up their natural banks by depositing heavy particles on its sides as they can’t be carried away by the river flow. These natural banks are called “levees”. One of the main causes of flood is the breaking of the so called “levees” due to heavy pressure of water.

               There are several ways to control floods. One is to have levees or dikes to protect lowlands, where the river water tends to pile up. There must be some emergency channels, such as spillways or floodways to discharge out the excess water. Another method is to develop huge dams or reservoirs to hold back flood waters and release them in a regulated way. Another important method is the afforestations on the vicinity of river banks and embarkments to prevent soil erosion and also to make the river banks more compact. 

Why the cotton plant is called Daughter of the Sun?

               The ancients called the cotton plant the ‘Daughter of the Sun’. This was because it was only under the powerful rays of the sun that the plant would grow and flourish. The hotter the sun, the whiter and stronger would be the fibres produced. Ideal conditions for cotton growing require sunlight, heat and rain. Due to these reasons cotton is mostly grown in hot and tropical places all over the world.

               The plant grows upto 2 metres and produces seed pods or bolls which contain about 30 seeds each covered with downy hairs. As the bolls ripen, they grow and then burst open to reveal a mass of fibres.

               The cotton fibres provide the most common material used in clothing. The cotton industry is the greatest of the textile industries and gives work to millions of people all over the world. Cotton fibre is the only fibre that does not have to be softened by soaking or subjected to any other expensive treatment. It just requires to be freed from seeds before being used. However, cotton disease (byssinois) are caused by cotton dust which affects the lungs of those working in industries.

               There are about 20 species of cotton plants, only four of which are cultivated. The People’s Republic of China is the leading producer of cotton, followed by the United States. Apart from these countries cotton is also grown in large quantities in India, Peru, Russia, Brazil, Egypt, and Pakistan and in other tropical and sub-tropical regions of the world. Cotton fibres vary in length from less than 2cm to 4 cm or more. However, short and medium length fibres account for about 90% of world production. Cotton fibres are used in textiles, rugs, sheets, bandages and book binding. Cotton seed can be squeezed for oil used in margarine, salad oil and mellorine. This is also used in manufacturing of cosmetics, paints and soaps. The seeds are then processed into cattle cake and fertilizer.