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2, GLOBE : LATITUDES AND LONGITUDES, , Figure 2.1 : Globe, , Let’s Do, Take a big round, potato or a ball., Pierce a knitting, needle through it. The, needle resembles the axis, shown in a globe. You can, now move the potato or the, ball around this axis from, left to right., , In the previous chapter, you have read that our planet, earth is not a sphere. It is slightly flattened at the, North and the South Poles and bulge in the middle., Can you imagine how it looks? You may look at a, globe carefully in your classroom to get an idea., Globe is a true model (miniature form) of the earth, (Figure 2.1)., Globes may be of varying size and type – big ones,, which cannot be carried easily, small pocket globes,, and globe-like balloons, which can be inflated and are, handy and carried with ease. The globe is not fixed. It, can be rotated the same way as a top spin or a potter’s, wheel is rotated. On the globe, countries, continents, and oceans are shown in their correct size., It is difficult to describe the location of a point on a, sphere like the earth. Now the question arises as to, how to locate a place on it? We need certain points of, reference and lines to find out the location of places., You will notice that a needle is fixed through the, globe in a tilted manner, which is called its axis. Two, points on the globe through which the needle passes, are two poles – North Pole and South Pole. The globe, can be moved around this needle from west to east, just as the earth moves. But, remember there is a major, difference. The real earth has no such needle. It moves, around its axis, which is an imaginary line., Another imaginary line running on the globe divides, it into two equal parts. This line is known as the, equator. The northern half of the earth is known as, the Northern Hemisphere and the southern half is, known as the Southern Hemisphere. They are both

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equal halves. Therefore, the equator is an, imaginary circular line and is a very, important reference point to locate places, on the earth. All parallel circles from the, equator up to the poles are called parallels, of latitudes. Latitudes are measured in, degrees., The equator represents the zero degree, latitude. Since the distance from the, equator to either of the poles is one-fourth, of a circle round the earth, it will measure, ¼th of 360 degrees, i.e. 90°. Thus, 90, degrees north latitude marks the North, Pole and 90 degrees south latitude marks, the South Pole., As such, all parallels north of the Figure 2.2 : Latitude, equator are called ‘north latitudes.’, Similarly all parallels south of the equator are called, Do you know?, ‘south latitudes.’, The value of each latitude is, therefore, followed by, By measuring, either the word north or south. Generally, this is, the angle of the, indicated by the letter ‘N’ or ‘S’. For example, both, Pole Star from, Chandrapur in Maharashtra (India) and Belo your place, you can know, Horizonte in Brazil (South America) are located on the latitude of your place., parallels of about 20° latitude. But the former is 20°, north of the equator and the latter is 20° south of it., We, therefore, say that Chandrapur is, situated at 20° N latitude and Belo, Horizonte is situated at 20° S latitude., We see in Figure 2.2 that as we move, away from the equator, the size of the, parallels of latitude decreases., , IMPORTANT PARALLELS OF LATITUDES, Besides the equator (0°), the North Pole, (90°N) and the South Pole (90° S), there, are four important parallels of latitudes–, (i) Tropic of Cancer (23½° N) in the, Northern Hemisphere. (ii) Tropic of, Capricorn (23½° S) in the Southern, Hemisphere. (iii) Arctic Circle at 66½°, north of the equator. (iv) Antarctic, Circle at 66½° south of the equator., GLOBE : LATITUDES AND LONGITUDES, , Figure 2.3 : Important Latitudes and Heat Zones, , 11

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HEAT ZONES, , Figure 2.4 : (a), , Torch-light falling on a straight, surface is bright and covers a, smaller area., , Figure 2.4 : (b), , Torch-light falling on a slanted, surface is less bright but covers a, bigger area., , OF THE, , EARTH, , The mid-day sun is exactly overhead at, least once a year on all latitudes in, between the Tropic of Cancer and the, Tropic of Capricorn. This area, therefore,, receives the maximum heat and is called, the Torrid Zone., The mid-day sun never shines, overhead on any latitude beyond the, Tropic of Cancer and the Tropic of, Capricorn. The angle of the sun’s rays, goes on decreasing towards the poles. As, such, the areas bounded by the Tropic, of Cancer and the Arctic Circle in the, Northern Hemisphere, and the Tropic of, Capricorn and the Antarctic Circle in the, Southern Hemisphere, have moderate, temperatures. These are, therefore, called, Temperate Zones., Areas lying between the Arctic Circle, and the North Pole in the Northern, Hemisphere and the Antarctic Circle and, the South Pole in the Southern, Hemisphere, are very cold. It is because, here the sun does not rise much above, the horizon. Therefore, its rays are, always slanting and provide less heat., These are, therefore, called Frigid, Zones (very cold)., , WHAT ARE LONGITUDES?, , Figure 2.5 : Longitudes, 12, , To fix the position of a place, it is, necessary to know something more, than the latitude of that place. You, can see, for example, that Tonga, Islands (in the Pacific Ocean) and, Mauritius Islands (in the Indian, Ocean) are situated on the same, latitude (i.e., 20° S). Now, in order to, locate them precisely, we must find, out how far east or west these places, are from a given line of reference, running from the North Pole to the, South Pole. These lines of references, are called the meridians of longitude,, THE EARTH : OUR HABITAT

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and the distances between them are measured in, Let’s Do, ‘degrees of longitude.’ Each degree is further divided, Draw a circle., into minutes, and minutes into seconds. They are semiLet the Prime, circles and the distance between them decreases, meridian divide, steadily polewards until it becomes zero at the poles, it into two equal halves., where all the meridians meet., Colour and label the, Unlike parallels of latitude, all meridians are of equal eastern hemisphere and, length. Thus, it was difficult to number the meridians. the western hemisphere., Hence, all countries decided that the count should Similarly draw another, begin from the meridian which passed through circle and let the equator, Greenwich, where the British Royal Observatory is divide it into two halves., located. This meridian is called the Prime Meridian. Now colour the Northern, hemisphere and Southern, Its value is 0° longitude and from it we count 180°, hemisphere., eastward as well as 180° westward. The Prime Meridian, and 180° meridian divide the earth into, two equal halves, the Eastern Hemisphere, and the Western Hemisphere. Therefore,, the longitude of a place is followed by the, letter E for the east and W for the west. It, is, however, interesting to note that 180°, East and 180° West meridians are on the, same line., Now look at the grid of the parallels of, latitude and meridians of longitude on the, globe (Figure 2.6). You can locate any point, on the globe very easily if you know its, latitude and longitude. For example,, Dhubri in Assam is situated at 26° N, latitude and 90° E longitude. Find out the, Figure 2.6 : Grid, point where these two lines cut each other., That point will be the location of Dhubri., To understand this clearly draw equidistant vertical, and horizontal lines on a paper (Figure 2.7). Label the, vertical rows with numbers and horizontal rows with, letters, draw some small circles randomly on points, where these horizontal and vertical lines intersect each, other. Name these small circles as a, b, c, d and e., Let vertical lines represent East Longitudes and, horizontal lines as North Latitudes., Now you will see that circle ‘a’ is located on B° N, latitude and 1° E longitude., Find out the location of other circles., Figure 2.7, GLOBE : LATITUDES AND LONGITUDES, , 13

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14, , THE EARTH : OUR HABITAT, , Figure 2.8 : Time zones of the World

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LONGITUDE, , AND, , TIME, , The best means of measuring time is by the movement, of the earth, the moon and the planets. The sun, regularly rises and sets every day, and naturally, it is, the best time-keeper throughout the world. Local time, can be reckoned by the shadow cast by the sun, which, is the shortest at noon and longest at sunrise and, sunset., When the Prime Meridian of Greenwich has the sun, at the highest point in the sky, all the places along, this meridian will have mid-day or noon., As the earth rotates from west to east, those places, east of Greenwich will be ahead of Greenwich time and, those to the west will be behind it (Figure 2.8). The, rate of difference can be calculated as follows. The earth, rotates 360° in about 24 hours, which means 15° an, hour or 1° in four minutes. Thus, when it is 12 noon, at Greenwich, the time at 15° east of Greenwich will be, 15 × 4 = 60 minutes, i.e., 1 hour ahead of Greenwich, time, which means 1 p.m. But at 15° west of Greenwich,, the time will be behind Greenwich time by one hour,, i.e., it will be 11.00 a.m. Similarly, at 180°, it will be, midnight when it is 12 noon at Greenwich., At any place a watch can be adjusted to read 12, o’clock when the sun is at the highest point in the, sky, i.e., when it is mid-day. The time shown by such, a watch will give the local time for that place. You can, see that all the places on a given meridian of longitude, have the same local time., , WHY DO WE HAVE STANDARD TIME?, The local time of places which are on different, meridians are bound to differ. For example, it will be, difficult to prepare a time-table for trains which cross, several longitudes. In India, for instance, there will be, a difference of about 1 hour and 45 minutes in the, local times of Dwarka in Gujarat and Dibrugarh in, Assam. It is, therefore, necessary to adopt the local, time of some central meridian of a country as the, standard time for the country. In India, the longitude, of 82½° E (82° 30 ' E) is treated as the standard, meridian. The local time at this meridian is taken as, the standard time for the whole country. It is known, as the Indian Standard Time (IST)., GLOBE : LATITUDES AND LONGITUDES, , Figure 2.9 : Indian Standard Meridian, , 15

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Kabeer lives in a small town near Bhopal. He tells his friend Alok that they will, not be able to sleep tonight. A day and night cricket match between India and, England had started at 2 p.m. in London. This means that the match would begin, at 7.30 p.m. in India and finish well into the night. Do you know what is the time, difference between India and England?, India located east of Greenwich at 82°30'E is 5 hours and 30 minutes ahead of, GMT. So it will be 7:30 p.m. in India when it is 2:00 p.m. noon in London., Some countries have a great longitudinal extent and so they have adopted, more than one standard time. For example, in Russia, there are as many as eleven, standard times. The earth has been divided into twenty-four time zones of one, hour each. Each zone thus covers 15° of longitude., , 1. Answer the following questions briefly., (a), , What is the true shape of the earth?, , (b), , What is a globe?, , (c), , What is the latitudinal value of the Tropic of Cancer?, , (d), , What are the three heat zones of the Earth?, , (e), , What are parallels of latitude and meridians of longitude?, , (f), , Why does the torrid zone receive maximum amount of heat?, , (g), , Why is it 5.30 p.m. in India and 12.00 noon in London?, , 2. Tick the correct answers., (a), , The value of the prime meridian is, (i) 90°, , (b), , (e), , 16, , (ii) the Equator, , (iii) the Tropic of Cancer, , The total number of longitudes are, (i) 360, , (d), , (iii) 60°, , The frigid zone lies near, (i) the Poles, , (c), , (ii) 0°, , (ii) 180, , (iii) 90, , The Antarctic circle is located in, (i), , the Northern hemisphere, , (ii), , the Southern hemisphere, , (iii), , the Eastern hemisphere, , Grid is a network of, (i), , parallels of latitudes and merdians of longitudes, , (ii), , the Tropic of Cancer and the Tropic of Capricorn, , (iii), , the North Pole and the South Pole, THE EARTH : OUR HABITAT

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3. Fill in the blanks., (a), , The Tropic of Capricorn is located at _________________., , (b), , The Standard Meridian of India is ____________________., , (c), , The 0° Meridian is also known as ____________________., , (d), , The distance between the longitudes decreases towards___________., , (e), , The Arctic Circle is located in the ____________ hemisphere., , 1. Draw a diagram of the globe showing the earth’s axis, the Equator, Tropics, of Cancer and Capricorn, Arctic Circle and Antarctic Circle., , 1. Draw and cut out six circles of the same size (approx. 3 cm. radius) from, cardboard. Mark diametres (NS, EW) and 23½o angles on each face of the, circles as shown on the figure. Place the circle one on top of the other and, stitch along the line NS. Now there are twelve semi-circles. Let one semi-circle, represent 0o or Greenwich Meridian (Prime Meridian). The 6th semi-circle from, it will be the 180o Meridian. Between the 0o and 180o there are 5 semi-circles, on both sides which are West and East longitudes 30o apart. On two ends of, the stapled line stick pins to represent the North and South Poles., A rubber band around the model touching the EW points will represent the, Equator. Two rubber bands touching the 23½o points, South and North of, the EW points will represent the tropics., , GLOBE : LATITUDES AND LONGITUDES, , 17