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Earth and Its Natural Satellites (Part 2) Class 5 Notes Science

You will learn about

Moon


The Moon

  • The moon is the natural satellite of the earth. 
  • It is a lifeless place. It has no air or water. 
  • It does not have its own light. It shines because it reflects the sunlight that falls on it.
  • No sound can be heard on the moon due to the absence of air. 
  • Its surface is covered with rocks and dust. 
  • There are tall mountains and plains on the moon. 
  • There are also large round ditches called craters.
  • If you look at the moon on a full moon night, you can see the light and dark areas. The dark areas are plains, and the light ones are mountains. 
  • Craters of the moon can be easily seen with a telescope.

Apollo 11 was the first spacecraft to land on the moon on 21st July, 1969. It carried three American astronauts – Neil Armstrong, Edwin Aldrin and Michael Collins.

 Chandrayaan–1, India’s first unmanned spacecraft was launched successfully on October 22, 2008 from Satish Dhawan Space Centre, Sriharikota by Indian Space Research Organisation (ISRO). This mission was aimed to map the moon’s surface and get more details of the moon. After completing most of the objectives it was finally called off on 30 August, 2009.

Phases of Moon

The moon takes about one month to revolve around the earth. As it revolves, it also rotates slowly. Since it revolves and rotates at the same speed, the same side of the moon always faces us. The moon seems to change its shape every day. The different shapes of the moon as visible from the Earth are called phases of the moon. The shape of a particular phase depends on the sunlit part that can be visible to us from the Earth. 

  • The day when we cannot see the moon in the sky is called the New Moon day. The moon is not visible as side of the Moon facing us gets no sunlight at all. 
  • In the next couple of days a small portion of the side of the moon facing us gets sunlight and is visible to us. This is the crescent Moon. 
  • In a week, the first quarter moon is visible. 
  • In the next three days from then, three-quarters of the Moon is visible to us. This is the waxing gibbous Moon. 
  • On the fourteenth day the entire side facing us gets sunlight and we can see the Full Moon. 
  • In the next fourteen days the moon progressively decreases in size, and the phases reverse. After the full moon is seen the waning gibbous moon, then the last quarter moon, the waning crescent moon and finally the new moon.

Effect on Tides 

  • Tides are the rise and fall of the water level in the oceans and seas. 
  • The rising of sea level is known as high tide. The fall of the sea level is called low tide. The rise and fall of the tides are known as the tide cycle. 
  • The gravitational force of the moon pulls the oceans slightly towards itself. This causes a bulge or high tide on the side of the earth closest to the moon.
  • The sun’s gravitational pull also plays a part.
  • When the sun and moon are in line with the earth (as during a full moon or new moon), their combined gravity cause very high and very low tides called spring tides.
  • When the sun and moon are at right angles to each other (as during a waxing or waning moon), the gravity of the sun helps to cancel out the pull of gravity from the moon causing neap tides.

 Eclipses

  • The sun is a source of light and the Earth and moon are opaque objects. 
  • When any opaque object comes in the path of light, it blocks light and casts its shadow. 
  • Sometimes, the sun, the Earth and the moon happen to come in a straight line. At times, the Earth comes between the sun and moon or the moon comes between the sun and Earth. 
  • In such a situation, the object in the middle casts its shadow on the other. This is called an eclipse.

Types of Eclipse

1. Lunar Eclipse

  • When the Earth comes between the sun and the moon, it casts its shadow on the moon. This is called lunar eclipse.
  • When the moon is completely in the dark shadow of the Earth, it is called a total lunar eclipse. 
  • When the moon is partly hidden by the dark shadow of the Earth, it is called a partial lunar eclipse.
  •  The part of the shadow that totally blocks the light is called umbra. 
  • The part that blocks only a part of sunlight is called penumbra.

2. Solar Eclipse

  •  When the moon comes between the sun and the Earth, it blocks sunlight from reaching the Earth and casts a shadow on the Earth. This is called solar eclipse.
  • When the sun cannot be seen at all, it is a total solar eclipse. 
  • When the sun is partly visible, it is a partial solar eclipse.
  •  Solar eclipses last for very short duration, a few minutes or so.

Artificial Satellites

  • Artificial satellites are man-made objects that revolve around the Earth. 
  • Artificial satellites are used for forecasting weather, transmitting signals of mobiles or television programmes, etc . 
  • The first artificial satellite was Sputnik 1, launched by Russia on 4 October 1957. 
  • Since then hundreds of artificial satellites have been launched. India has launched several satellites.  
  • Aryabhata was India’s first satellite launched in the year 1975. 
  • Cartosat-2 is a remote sensing satellite launched by India on 12 January, 2018. 
  • India launched the world’s first educational satellite called EDUSAT in September 2004.
  • Bhaskara, Rohini, INSAT-2A and CARTOSAT are some other Indian satellites. 

Uses of Artificial Satellites

  • Some are communication satellites (e.g. GSAT-15 was launched on 11 November 2015) which are used to send telephone conversations and television programmes around the world.
  • Weather satellites are used to forecast the weather. Such pictures not only help us to forecast the weather but also to give early warning of dangerous storms and cyclones.
  • Some satellites, called remote sensing satellites take photographs of the earth to study the features of the earth’s surface.
  • Satellites are also used to study outer space. They have helped to increase our knowledge of the planets and stars.

Space Travel

  • Space is a lonely and difficult place. 
  •  who go to space are exposed to high levels of radiation. 
  • Vigorous training is needed to prepare for space missions.
  •  Rakesh Sharma, late Kalpana Chawla and Sunita Williams are astronauts of Indian origin who have travelled in space.
The document Earth and Its Natural Satellites (Part 2) Class 5 Notes Science is a part of the Class 5 Course Science Class 5.
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FAQs on Earth and Its Natural Satellites (Part 2) Class 5 Notes Science

1. How does the Moon affect tides?
Ans. The Moon's gravitational pull is the primary factor that causes tides on Earth. As the Moon orbits around the Earth, its gravitational force creates a tidal bulge on the side of the Earth facing the Moon, causing a high tide. At the same time, there is another high tide on the opposite side of the Earth due to the centrifugal force caused by the Earth-Moon system's rotation. The areas between these high tides experience low tides. This gravitational interaction between the Moon and Earth creates a regular pattern of high and low tides.
2. What is the role of the Moon in eclipses?
Ans. The Moon plays a crucial role in both solar and lunar eclipses. During a solar eclipse, the Moon passes in between the Earth and the Sun, blocking the Sun's light from reaching certain parts of the Earth. This occurs when the Moon is in its new moon phase. On the other hand, during a lunar eclipse, the Earth comes between the Sun and the Moon. The Earth's shadow falls on the Moon, causing it to darken or turn reddish. Lunar eclipses occur when the Moon is in its full moon phase.
3. How do artificial satellites work?
Ans. Artificial satellites are man-made objects that orbit around the Earth or other celestial bodies. These satellites are launched into space using rockets and are equipped with various instruments and technologies for specific purposes. Once in orbit, they follow specific trajectories determined by their intended mission. Artificial satellites can be used for communication, weather forecasting, scientific research, mapping, and surveillance. They stay in orbit due to the balance between their forward motion and the gravitational pull of the Earth.
4. What are the benefits of space travel?
Ans. Space travel has numerous benefits. It has enabled scientific discoveries and advancements in various fields like astronomy, astrophysics, and planetary science. Space missions provide valuable data about the universe, our solar system, and Earth itself. Space travel also plays a crucial role in technological advancements, leading to innovations in materials, communications, and computing. Furthermore, space exploration inspires and motivates people, fostering curiosity and expanding our knowledge of the universe.
5. How do we travel to space?
Ans. Currently, space travel is accomplished using rockets. Rockets are powerful vehicles that use the principle of Newton's third law of motion, which states that for every action, there is an equal and opposite reaction. By expelling high-speed gases in one direction, rockets generate thrust in the opposite direction, propelling them forward. Once outside the Earth's atmosphere, rockets continue their journey by using orbital mechanics to achieve the desired trajectory. The journey to space requires careful planning, precise calculations, and advanced technology to ensure the safety and success of the mission.
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