6th Class Chapter 2: Globe - Model of the Earth PDF

Globe - Model of the Earth CHAPTER 2 CHAPTER 2 Learning Outcomes The students will be able to understand the Globe as a true model of the earth. understand Latitudes and Longitu des, Poles and the Equator. understand the motions of the Earth and how day and night, seasons occur. Globe - Model...

Globe - Model of the Earth CHAPTER 2 CHAPTER 2 Learning Outcomes The students will be able to understand the Globe as a true model of the earth. understand Latitudes and Longitu des, Poles and the Equator. understand the motions of the Earth and how day and night, seasons occur. Globe - Model of the Earth Earth Globe Latitudes Longitudes Land & Water Movements Northern Hemisphere 00 - 900 N Western Continents Hemisphere & Oceans 00 - 1800 W Southern Hemisphere 00 - 900 S Eastern Hemisphere 00 - 1800 E Revolution Rotation Day Night Seasons 30 Eclipses Solstices Equinoxes Pacific Ocean Pacific Ocean Have you ever seen the world map? Name the Ocean located on the left side in the given world map? Name the Ocean located on the right side in the given world map? Fig. 2.1 World map You will observe the same Ocean on both sides of the map. It is the Pacific Ocean. When you fold the world map, the two parts come together to one place. Thus, we can say that the Earth is round in shape. It has been proved by the ancient navigators during the 15th century and it is very much clear by Satellite images. So, the Globe is a true model of the Earth. In the previous chapter, you have read that our planet Earth is not a complete sphere. It is slightly flattened at the North and the South poles and bulges in the middle. Can you imagine how it looks like? You may look at a globe carefully in your class room to get an idea. The globe is not static. It rotates as a top toy or a potter's wheel. On a Globe, countries, continents and oceans are shown in proportionate size. Axis of the Earth You 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 ie., North Pole and South Pole. The Globe moves 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. Earth’s rotational axis is an imaginary straight line which runs through the North and South Poles. A NORTH POLE A SOUTH POLE Fig. 2.2 Globe DidYou YouKnow Know? Do The oldest terrestrial globe was made in 1492 by Martin Behaim. Another “remarkably modern looking” terrestrial globe of the Earth was constructed by Taqi Al - Din at the Constantinople Observatory during the 1570s. The World’s first seamless celestial globe was built by Mughal scientists under the patronage during Mughal empire. The word globe comes from the Latin word globus, meaning “sphere.” Think & Respond How does the earth rotate and revolve without any needle unlike the globe? Discuss with the teacher. All the celestial bodies are round in shape. Why ? 32 Axis Let's Do North Pole Take a big round apple. Pierce a cycle spoke through it. The spoke resembles the axis shown in a globe. You can now move the apple around this axis from left to right. South Pole Fig 2.3 Model of globe Northern and Southern Hemispheres The imaginary line running horizontally on the middle of the Globe divides it into two equal halves. This line is known as the Equator (0o latitude). The half that lies north of the Equator is known as the Northern Hemisphere and the half that lies south of the Equator is known as the Southern Hemisphere. Fig 2.4 Earth Hemispheres Think & Respond • In which Hemisphere is India located? • Which hemisphere has the maximum number of Continents? • In which Hemisphere is the Continent Antarctica located? Complete the table with the help of World map, Globe or Atlas Name the Continents in the Name the Continents in Name the Continents that Northern Hemisphere the Southern Hemisphere are spread over Southern and Northern Hemispheres Name of the Oceans in the Name of the Oceans in Name the Oceans that are Northern Hemisphere the Southern Hemisphere spread over Southern and Northern Hemispheres 34 Latitudes If you observe the globe closely you can see some lines drawn parallel to the Equator. These lines are Latitudes. They are parallel to each other and never meet. Latitudes range from 0o to 90o to the North and 0o to 90o to the South of the Equator. The 90o Latitude on the North is the North Pole and the 90 o Latitude on the South is the South Pole. There are 90o Latitudes in North and 90o Latitudes in South. All the Latitudes are circles except Poles. North Pole, the Arctic Circle and the Tropic of Cancer are the important Latitudes in the Northern Hemisphere. On the other hand, the South Pole, the Antarctic Circle and the Tropic of Capricorn are the important Latitudes in the Southern Hemisphere. The climatic division of the Earth can be studied with the help of Latitudes. Fill the table with the help of a Globe / Map Latitude North Pole Degrees Arctic Circle Tropic of Cancer Equator 0o Tropic of Capricorn Antarctic Circle South Pole DidYou YouKnow Know Do Fig. 2.5 Important Latitudes The imaginary circular lines parallel to the Equator are called latitudes. Latitude is related to the Latin word latitudo, meaning "breadth, width, extent, size." Think & Respond Why do latitudes get smaller towards the poles? Which latitude is the biggest circle? 36 Longitudes Western hemisphere Longitudes are called Meridians. 0o Longitude is called p r i me me r i d i an / Greenwich. The line seen opposite to it is called the International Date Line and found at 180o longitude. Based on these two lines the earth is divided into two Hemispheres; the one on the eastern side of the Greenwich is known as Eastern Hemisphere and the other as Western Hemisphere. Eastern hemisphere We see certain lines drawn perpendicular to the latitudes on the globe. These lines connect the North and South poles. They are called the Longitudes. Fig. 2.6 Longitudes DidYou YouKnow Know Do The imaginary semi circle lines that join the North and South Poles are called Longitudes. Longitude is related to the Latin word longitudo, meaning "length, long duration." Longitudes from the Greenwich to the International Date Line in the Eastern o (0 to 180 E) are known as eastern longitudes and those from the Greenwich to o o International Date Line in the Western (0 to 180 W) are known as western o o o longitudes. Infact 180 E and 180 W longitudes are same as 180 which is called International date line. o o There are 180 longitudes in east and 180 longitudes in west and in total o there are 360 longitudes including Greenwich. Calculating the exact location, time and climate of that place can be done with the help of latitudes and longitudes. This can be studied in detail in your next classes. o Facts about Longitudes Longitudes are known as Meridians. Facts about Latitudes Latitudes are parallel to each other and never meet. Longitudes measure the distance of east or west of the prime meridian. Latitudes help to measure the distances located towards the North or the South from the Equator. Longitudes are equal in length. Longitudes are farthest at the Equator and meet at the poles. Latitudes are invisible horizontal lines that run parallel to the equator. Longitudes are invisible vertical lines that run North-South direction. 38 Identify and write down the Latitude and Longitude between the extents of the given Andhra Pradesh map. You can take the help of Atlas. Bay of Bengal N C Map. 2.1 Andhra Pradesh political map Movements of the Earth There are many celestial bodies in the universe such as Stars, Planets, Satellites. The Earth is one of the planets among them. Planets rotate themselves while revolving round the Sun. The Earth basically has two movements. They are: Rotation and Revolution. Earth moves on its own Fig. 2.7 Earth Rotation - Day and Night axis from West to East at a speed of 1610 kilometers per hour. This movement is called “Rotation”. 40 Day and night are caused due to the Earth’s rotation. During rotation i.e., while the Earth moves on its own axis, only half of the portion of it receives Sun’s rays and therefore, it appears bright. The other half remains in darkness. It means that the half portion of the Earth hit by Sun’s rays has ‘day’ while the remaining portion has ‘night’. In the process of Earth rotation, the portion hit by Sun’s rays gradually goes into light and the light portion gradually goes into dark. That is why day and night occur alternately. It takes 23 hours 56 minutes and 4.09 seconds (about 24 hours) i.e., one day to complete one rotation. The Earth while moving on its own axis also moves around the Sun. This movement is called “Revolution.” The fixed and regular path through which earth revolves around the Sun is called “Orbit.” The orbit is elliptical in shape. The length of the Earth’s orbit is 965 million kilometers. Earth takes one year to complete one revolution. It takes 365¼ days. Usually a year consists of 365 days only. The remaining one-fourth of the day is added once in four years and that year is known as “Leap Year.” Hence a Leap Year consists of 366 days. In a Leap year, we have 29 days in the month of February. But in a normal year we have 28 days in February. Fig. 2.8 Revolution of the Earth and Seasons From the figure 2.8 it is clear that the Earth is moving around the sun in an elliptical orbit. Throughout its orbit, the earth is inclined in the same direction. A year is usually divided into summer, winter, spring and autumn seasons. Seasons change due to the change in the position of the Earth around the Sun. Look at the Figure 2.8 You will see that on 21st June, the Northern Hemisphere is tilted towards the Sun. The rays of the Sun fall directly on the Tropic of Cancer. As a result, these areas receive more heat. The areas near the poles receive less heat as the rays of the Sun are slanting. The North Pole is inclined towards the Sun and the places beyond the Arctic Circle experience continuous day light for about six months. Since a large portion of the Northern Hemisphere receives light from the Sun, it is summer in the regions north of the Equator. 42 The longest day and the shortest night at these places occur on 21st June. In the Southern Hemisphere all these conditions are reversed. It is winter season there. The nights are longer than the days. This position of the earth is called the Summer Solstice. On 22nd December, the Tropic of Capricorn receives direct rays of the Sun as the South Pole tilts towards it. As the Sun rays fall vertically at the Tropic of Capricorn, a larger portion of the Southern Hemisphere gets light. Therefore, it is summer in the Southern Hemisphere with longer days and shorter nights. The reverse happens in the Northern Hemisphere. This position of the earth is called the Winter Solstice. Equino x On 21st March and September 23rd, direct rays of the Sun fall on the Equator and the whole earth experiences equal day and nights. This is called an Equinox. On 23rd September, it is autumn season in the Northern Hemisphere and spring season in the Southern Hemisphere. The opposite is the case on 21st March, when it is spring in the Northern Hemisphere and autumn in the Southern Hemisphere. Thus, you find days and nights and changes in the seasons occur because of the rotation and revolution of the earth. Eclipses We have learnt that the Earth revolves round the Sun and the Moon revolves round the Earth. While they so revolve, at times it happens that they come in a straight line. Then either Solar Eclipse or Lunar Eclipse occurs. During the time of eclipses it appears that a shadow is cast either on the Sun or on the Moon. They are two types. Solar Eclipse A solar eclipse occurs when the Moon passes in a direct line between the Earth and the Sun. The Moon's shadow travels over the Earth's surface and blocks out the Sun's light as seen from Earth. Solar Eclipses occur only on new moon day, but not on all new Moon days. Lunar Eclipse At any given time, only half of the Earth faces the Sun. The other half will be in a shadow and is thus in darkness. A Lunar Eclipse occurs when the Moon passes directly behind Earth and into its shadow. This can occur only when the Sun, Earth, and Moon are exactly or very closely aligned with Earth between the other two. During a total Lunar Eclipse, Earth completely blocks direct sunlight from reaching the Moon. Lunar Eclipses occurs only on a full moon day. But lunar eclipse does not occur on all full moon days. You can have a detailed study of eclipses from your science textbook of class VI. DidYou YouKnow Know? Do Do you know that Christmas is celebrated in Australia in the Summer season? 44 Let's Do Fig 2.9 Example of Day and Night Harika and Sahasra are two children living at places located on almost opposite faces of the Earth. Harika lives in California in the USA and Sahasra lives in Guntur in India. You can see that these places are located on opposite faces of the Earth. While Harika is sleeping at night, Sahasra goes to school in the morning. While Harika goes to school in the morning, it will be night at Sahasra’s place. When it is day on one face of the Earth, the opposite face experiences night. Thus day and night are experienced one after the other. Let us see how this happens through a simple experiment. Fig 2.11 Day and Night occurrence Fig 2.10 Day and Night observation As shown in the picture, place a globe against any source of light. Now one face will be illuminated and the other will be in the dark. Turn the globe. You can see that the illuminated face gradually turns dark and the dark face gradually turns illuminated. Do you know that the most important source of light and heat for all life on Earth is the Sun? You have already learned that the shape of the Earth is spherical and that it spins on its own axis. The part of the Earth facing the Sun due to rotation gets illuminated and experiences day. As the opposite face does not get sun light, night is experienced there. Day and night are experienced one after the other due to the rotation of the Earth. 46 Glossary Axis : Equator : Tropic of Cancer Tropic of Capricorn Arctic Circle Antarctic Circle North Pole South Pole : : : : : : Meridians : Greenwich / Prime meridian : International Date Line : an imaginary line about which a body rotates 0o latitude 23½o Northern latitude 23½o Southern latitude 66½o Northern latitude 66½o Southern latitude 90o Northern most part of the Earth 90o southernmost part of the Earth longitudes connecting North and South Poles and shows mid-day 0o longitude 180o degrees east and west Latitudes : imaginary lines that runs parallel to the Longitudes : imaginary lines that runs between the Northern Hemisphere : Southern Hemisphere : Eastern Hemisphere : Western Hemisphere : Seasons : Solar Eclipse : Lunar Eclipse : Equator North Pole and South Pole the half of the earth that lies north of the equator the half of the earth that lies south of the equator. half of the Earth that lies east of the Prime Meridian. half of the Earth that lies west of the Prime Meridian. seasons are divisions of the year, defined by changes in weather. occurs when the Moon passes between the Sun and Earth on one line. occurs when the Earth moves between Sun and Moon on one line. 48