6 Social SEM-1 Textbook PDF

Our Earth in the Solar system CHAPTER 1 Learning Outcomes The students will be able to understand the celestial bodies. understand different components of the Solar System. differentiate between Stars, Planets and Satellites. recognise that the Earth is a unique celestial body. Celestial Bodies...

Our Earth in the Solar system CHAPTER 1 Learning Outcomes The students will be able to understand the celestial bodies. understand different components of the Solar System. differentiate between Stars, Planets and Satellites. recognise that the Earth is a unique celestial body. Celestial Bodies Sun Planets Earth Asteroids Satellites Moon Solar System Milky way / Galaxy Universe 2 Meteoroids Comets In summer months we prefer to sleep on the terrace or in open air. At night time what do we observe in the sky? The whole sky is visible with many twinkling objects. Along with these bright objects, we also see the Moon on most of the days. Let us know more about these bodies. Fig 1.1 Sky during Night Do you wonder why we can’t see the Moon and all the bright tiny objects during day time? It is because, the very bright light of the Sun does not allow us to see all these bright objects of the night sky. The Sun, the Moon and all those objects shining in the night sky and other bodies like Earth etc., are called the celestial bodies. Some celestial bodies are very big and hot. They are made up of gases. They have their own heat and light which they emit in large amounts. These celestial bodies are called Stars. The Sun is a Star. Countless twinkling stars in the night sky are similar to the Sun. But we do not feel their heat or light, and they look so tiny because they are very far away from us. Some celestial bodies do not have their own heat and light. They are lit by the light of the Stars. Those are Planets, Satellites, Asteroids, Meteoroids, Comets etc. The Earth on which we live is a Planet. It gets all its heat and light from the Sun, which is our nearest star. If we look at the Earth from a great distance, it will appear to be shining just as the Moon. The Moon that we see in the sky is a Satellite. It is the companion of our Earth and moves around it. Like our Earth, there are seven other Planets that get heat and light from the Sun. Some of them have their Moons too. 4 Let’s Do Why can’t we see the moon and the other bright objects after the sunrise? Let us observe celestial bodies: Required material: Torch, sheet of plain paper, pencil and a needle. Process: 1. Place the torch in the centre of the paper with its glass front touching the paper. 2. Now draw a circle around the torch. 3. Perforate the paper with the needle within the circled area. 4. Now place the perforated circle part of the paper on the glass front and wrap the paper around the torch with a rubber band. 5. In a dark room, stand at some distance facing a plain wall. Switch off all other lights. Now flash the torch light on the wall. You will see numerous dots of light on the wall, which look like stars at night. 6. Switch on all the lights in the room. All dots of light will be almost invisible. 7. You may now compare the situation with what happens to the bright objects of the night sky after the Sun rises in the morning. Constellations Have you ever noticed various patterns formed by different groups of stars in the sky? Those are called ‘Constellations’. They were named after different animals, objects and creatures depending on the shape they look. Ursa Major or Big Bear is one such Constellations. One of the most easily recognisable constellation is Saptarishi. It is group of seven stars. Do You Know ? In ancient times people used to determine directions during the night with the help of Stars. In the Northern Hemisphere people determine the North direction with the help of the North Star. It indicates the north direction. It is also called the Pole Star. It always remains in the same position in the sky. We can locate the position of the Pole Star with the help of Saptarishi (Ursa Major) constellation. Fig 1.2 Saptarishi and the North Star 6 The Solar System We came to know that the Earth doesn’t have its own heat and light. Where does the Earth get light and heat from? It is the Sun that gives the Earth light and heat. The Sun is the closest Star to the Earth. So the Earth receives light and heat from the Sun. Not only the Earth but also seven other Planets are moving around the Sun. The Sun, eight Planets, Satellites and some other celestial bodies known as Asteroids and Meteoroids form the Solar system. We often call it a solar family with the Sun as its head. The Sun The Sun is in the centre of the Solar System. It is huge and made up of extremely hot gases. It provides the pulling force that binds the Solar System. Each member of the Solar System revolves around the Sun. The Sun is the ultimate source of heat and light for the Solar system. The surface temperature of the Sun is around 60000C. But that tremendous heat is not felt so much by us because it is far away from us. The Sun is about 150 million kms away from the Earth. Fig 1.3 The Sun Did You Know Know ? Do You How big is the Sun? 13 lakhs Earths can fit inside the Sun. Think & Respond From the ancient times people worship the Sun as God. Give reasons. Planets There are eight Planets in our Solar system. According to their distance from the Sun the order of Planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. All the eight Planets of the Solar system move around the Sun in fixed paths. These paths are elongated. They are called orbits. The four Planets nearer to the Sun are called Inner Planets. Those are Mercury, Venus, Earth and Mars. The inner Planets are comparatively smaller in size and are composed of rocks. The last four Planets are called as Outer Planets. Those are Jupiter, Saturn, Uranus and Neptune. They are large and made up of gases and liquids. Mercury is the nearest planet to the Sun. Venus is considered as Earth’s twin because its size and shape are very much similar to that of the Earth. Jupiter is the biggest and Mercury is the smallest planet. To remember the order of eight planets around the sun. My Very Educated Mother Just Served Us Noodles 8 Fig 1.4 Solar System Explore Browse the following website and know more about Solar system. https://spaceplace.nasa.gov/menu/solar-system/ 10 4.MARS 3.EARTH 2.VENUS One orbit around sun - 3651/4 days One spin on axis - 1 days Number of Moons - 1 One orbit around sun - 687 days One spin on axis - 1 days Number of Moons - 2 One orbit around sun - 255 days One spin on axis - 243 days One spin on axis - 59 days 1.MERCURY One orbit around sun - 88 days One orbit around sun - 84 years. One spin on axis - 17 hours 14 minutes, number of moons 27 One orbit around sun - 164 years. One spin on axis - 16 hours 7 minutes, number of moons 14 8.NEPTUNE One orbit around sun - 29 years, 5 months. One spin on axis - 10 hours 40 minutes, number of moons 82 (53 are confirmed, 29 are identified and yet to be named) One orbit around sun - 11 years, 11 months about 12 years. One spin on axis - 9 hours 59 minutes, number of moons 79 7.URANUS 6.SATURN 5.JUPITER Explore Up to 2006 there were nine Planets in our Solar System, but now we have only eight Planets. What was the 9th planet? What happened to it? Find out the reasons with the help of your teacher. Let’s Do Observe the following picture and name the planets in the boxes given below. Fig 1.5 Planets The Earth Our home planet the Earth is the third nearest planet to the Sun. In size, it is the fifth largest planet. It is slightly flattened at the poles and bulges in the middle. That is why its shape is described as a Geoid. Geoid means an Earth-like shape. The only natural satellite of the Earth is the Moon. From the outer space, the Earth appears blue because its two-thirds surface is covered by water. It is, therefore, called a Blue planet. Fig 1.6 Earth Think & Respond What do animals and plants require in order to grow and survive? 12 The Earth is the most suitable planet to support life. It has four major components that we call as the realms of the Earth - Lithosphere, Hydrosphere, Atmosphere and Biosphere. The first three components along with suitable climate make life possible on the Earth.This is called the Biosphere. Now let us have a look at each of the spheres. Fig 1.7 Spheres of the Earth DidYou YouKnow Know? Do Light travels at the speed of about 300,000 km per second. Yet even with this speed, the light of the Sun takes about eight minutes to reach the Earth. Lithosphere The lithosphere is the land on which we live. It is the solid outer layer of the Earth consisting of rocks and soils. Hydrosphere The hydrosphere consists of water bodies such as Oceans, Seas, Rivers, Lakes, Ice caps on mountains, Tanks etc., Atmosphere Atmosphere is the layer of air that surrounds the Earth. Different types of gases make up the atmosphere. The major gases are Nitrogen (78%) and Oxygen (21%). The other gases like Carbon dioxide, Hydrogen, Helium, Argon, and Ozone are present in smaller amounts. Biosphere All living things existing on the land, in the water and in the air together called as biosphere. It consists of plants, animals, bacteria and other tiny organisms. We will learn more about these spheres in higher classes. Think & Respond How can you say that our Earth is a unique Planet in the Solar system? 14 Satellites A Satellite is a celestial body that moves around the Planets in the same way as the Planets move around the Sun. Mercury and Venus do not have any Satellites. All the other Planets have Satellites. The Moon Our Earth has only one natural satellite, that is the Moon. Its diameter is only onequarter that of the Earth. It appears so big because it is nearer to our planet than other celestial bodies. It is about 3,84,400 km away from us. Fig 1.8 Moon Now you can compare the distance of the Earth from the Sun and that from the Moon. The Moon moves around the Earth in about 27 days. It takes exactly the same time to complete one spin. As a result, only one side of the Moon is visible to us on the Earth. The Moon does not have conditions favourable for life. It has mountains, plains and depressions on its surface. These cast shadows on the surface of the Moon. Do You Know ? Neil Armstrong, an American Astronaut, was the first man to step on the surface of the Moon on 21st July 1969. Explore Who is the first Indian Astronaut to go into space? Have you heard about Chandrayaan-1 and Chandrayaan-2. Try to know about them and discuss in the class. Man-made Satellite It is an artificial body. It is designed by scientists to gather information about the universe and the Earth for communication. It is carried by a rocket and placed in the orbit around the Earth and other Solar bodies. Some of the Indian Satellites in space are INSAT, IRS, EDUSAT etc. 16 DidYou YouKnow Know? Do Indian Space Research Organisation (ISRO) launches Satellites into space from its launching station at Sriharikota. It was named as ‘‘Satish Dhawan Space Centre (SDSC) Sriharikota High Altitude Range (SHAR)’’ in memory of Satish Dhawan, former Chairman of the ISRO. Fig 1.9 Launching of Satellite into space Think & Respond How are man-made Satellites useful to mankind? Discuss. DidYou YouKnow Know Do ? On 24th September, 2014 Mangalyaan (Mars Orbiter Mission - MOM), launched by the Indian Space Research Organization (ISRO), reached the orbit of Mars to explore its atmosphere and topography. ISRO has now become the fourth space agency in the world to reach Mars after the Soviet Space programme, NASA and the European Space Agency. Aster oids Apart from the Planets and Satellites, there are number of small rocky objects which also move around the Sun. These bodies are called Asteroids. They are found between the orbits of Mars and Jupiter. Scientists are of the view that Asteroids are parts of a Planet which exploded many years back. 18 Fig 1.10 Asteroid Meteoroids The small pieces of rocky or metallic bodies which move around the Sun are called Meteoroids. Sometimes these Meteoroids come near the Earth and tend to drop upon it. During this process due to friction with the air they get heated up and burn. It causes a flash of light. Sometimes, a meteor without being completely burnt, falls on the Earth and creates a hollow. Comets A Comet is a celestial object made up of a head and a tail. The head of a comet consists of solid particles held together by ice and the tail is made of gases. Halley’s Comet is the most famous comet which comes close to the Earth every 76 years. This comet appeared in 1986 and will appear next in 2061. Fig 1.11 Comet Galaxy We can see a white glowing path across the sky on a clear starry night. It is a cluster of millions of Stars. A galaxy is a huge cluster of Stars. Our Solar System is a part of Milky Way or Galaxy. In ancient India it was imagined to be a river of light flowing in the sky. Thus, it was named Akash Ganga. Fig 1.12 Galaxy Universe There are millions of galaxies that make the Universe. It is difficult to imagine how big the universe is. The scientists are still trying to find out more and more about it. We are not certain about its size but we know that all of us belong to this universe. 20 Think & Respond Can you relate yourself with the Universe now? You are on the Earth and the Earth is a part of the Solar System. Our Solar System is a part of the Milky Way or Galaxy which is part of the Universe. Think of the fact that Universe contains millions of such galaxies. How do you fit in the picture? How tiny you are? Think a while. Fig 1.13 Earth and Universe Glossary Galaxy : the cluster of Stars Asteroids : irregular shaped rocks between Mars and Jupiter Meteoroids : small rocky or metallic bodies in outer space Satellites : celestial bodies that move around the Planets Orbit : the path in which the Planets move around the Sun Geoid : Earth like shape Lithosphere : outer rocky layer on the Earth Hydrosphere : water layer on the Earth Atmosphere : layer of gases above the Earth Biosphere : layer of life on the Earth Constellation : patterns of Stars Improve Your Learning 1. 2. 3. 4. 5. 6. How does a planet differ from a star? What is meant by the ‘Solar System’? Why is life not possible on all Planets? Why do we always see only one side of the Moon? What is the Universe? Air and water are essential to live on the Earth. But now they are being polluted by humans. What happens to the life of humans on this Earth if pollution increases further? 22 7. Scientists are now trying to explore more about Moon and other Planets. Do you think their efforts benefit us? 8. Observe the figure 1.4 and fill the table Sl.No Name of the Planet Distance from the Sun No. of Moons Project Work 1. Prepare a model of the Solar System. Choose the correct answer 1. Though tremendous heat is emitted by the Sun, why do we receive only limited heat? [ ] A) The sun is very far from the Earth B) The sun is very small compared to the Earth C) The sun is very close to the Earth 2. The planet known as the Earth’s twin is ____ A) Jupiter B) Saturn C) Venus [ ] 3. Which is the third nearest planet to the Sun ? A) Venus B) Earth C) Mercury [ ] 4. All the Planets move around the Sun in a ____ A) Circular path B) Rectangular path C) Elongated path [ ] 5. Asteroids are found in between the orbits of ____ A) Saturn and Jupiter B) Mars and Jupiter C) Earth and Mars [ ] Match the following 1. Blue Planet [ ] a. Mars 2. Farthest Planet to Sun [ ] b. Neptune 3. Fourth Planet from Sun [ ] c. Mercury 4. Nearest Planet to Sun [ ] d. Earth 24 Let’s Do Solve the puzzle with the terms defined in the following statements CROSS 1. The cluster of millions of Stars 2. The natural satellite of the Earth 3. The ringed planet (see figure 1.4) 4. The sphere of water 5. The celestial object that is made up of head and tail DOWN 1. The shape of the Earth 2. The closest Star to the Earth 3. The path of the Planets that move around the Sun 4. The sphere of gases that surrounds the Earth 5. The small pieces of celestial bodies, move around the Sun between Mars and Jupiter 4 1 2 5 2 5 3 26 3 Let’s Do 1. You might have heard that people make human chains and run for world peace etc. You can also make a Solar System and run for fun by using the following steps. Step - 1: All children of your class can play this game. Assemble in a big hall or on a playground. Step - 2: Now draw eight circles on the ground. Draw all circles in the same manner. Step - 3: Prepare 10 placards. Name them as Sun., Moon, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. Step - 4: Select 10 children in the following order and give each one of them a placard. Order of placard distribution ü The Sun - tallest, The Moon - smallest; Mercury, Mars, Venus and Earth (almost equal heights); Neptune, Uranus, Saturn and Jupiter taller than the earlier four Planets but smaller than the Sun. ü Now ask the children holding placards to take their places with the Sun in the centre in their orbits. Ask the child holding the Moon placard to keep the hand of the child holding the Earth placard always. ü Now your Solar system is almost ready to go into action. ü Now make everybody move slowly in the anti-clockwise direction. Your class has turned into a small human replica of the Solar system. ü While moving on your orbit you can also turn around. For every celestial body the spin should be anti-clock wise except for Venus and Uranus who will make the spin in the clock-wise direction Field Visit 1. Observe the video of Planetorium in the QR Code. Describe your experiences. 2. Visit SHAR which is located in SPSR Nellore Distirct. 28