CBSE Notes For Class 6 Geography Social Science Chapter 1 The Earth in the Solar System
Celestial Bodies
- The Sun, the Moon, and all those objects shining in the night sky are called celestial bodies. These are made up of gases. Some of these are very big and hot.
- The celestial bodies that have their own heat and light are called stars. They can emit their heat and light in large amounts. For example, the Sun is a star as it has its own light and heat.
- The twinkling stars in the night sky are similar to the Sun. However, their heat or light cannot be felt and they look so tiny because they are very far away from the Earth.
Knowledge Plus: The people who study the celestial bodies and their movements are called astronomers. Aryabhatta was a famous astronomer of ancient India. According to him, the Moon and the planets shine due to reflected sunlight.
Constellations: The various patterns formed by different groups of stars are called constellations. Ursa Major or Big Bear is an example of the constellation.
- The constellation that is very common and can be easily seen is Saptorishi (sapla means seven and rishi means sages). It is a group of seven stars, that forms a part of Ursa Major Constellation.
- The ancient people used to determine directions with the help of stars during the night. The Pole star or North star always remains in the same position in the sky and shows the North direction.
- One can locate the position of the Pole star with the help of the Saptarishi. If an imaginary line is drawn joining the pointer stars and extended further, it will point to the Pole star.
CBSE Notes For Class 6 Geography Chapter 1 The Solar System
- The Sun, eight planets, satellites, and other celestial bodies known as asteroids and meteoroids form the solar system. It is also called the solar family with the Sun as its head.
- In Roman mythology ‘Sol’ is the ‘Sungod’, thus ‘Solar means ‘related to the Sun’. The family of the Sun is, therefore, called the solar system.
The Sun: The Sun is in the center of the solar system. It is huge and made up of extremely hot gases. It provides the pulling force that binds the solar system.
The Sun is the ultimate source of heat and light for the solar system. However, its tremendous heat is not felt because despite being the nearest star, it is far away from the Earth. The Sun is about 150 million km away from the Earth.
Knowledge Plus: Light travels at the speed of about 300,000 km per second. Even with this speed, the light of the Sun takes about eight minutes to reach the Earth.
Planets: The word ‘Planet’ comes from the Greek word ‘Plantai’ which means ‘wanderers’.
- Planets are those celestial bodies that do not have their own light and receive light from the stars. All the planets in the solar system get heat and light from the Sun.
- There are eight planets in the solar system which move in fixed paths around the Sun. These elongated paths are called orbits.
- According to the distance from the Sun, the planets can be arranged as Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
- Mercury is the nearest planet to the Sun. It takes only 88 days to complete one round along its orbit. Neptune is the farthest planet from the Sun.
- The shape and size of Venus are similar to the Earth, thus it is considered Earth’s-twin.
- Till August 2006, Pluto was also considered a planet. However, after the decision of the International Astronomical Union in a meeting, Pluto is considered a dwarf planet, like other celestial objects (Ceres, 2003 UB313).
- An easy way to memorize the name of the planets in order of their distance from the Sun is ‘My Very Efficient Mother Just Served Us Nuts
Knowledge Plus: Jupiter, Saturn, and Uranus have rings around them. These are belts of small debris. These rings may be seen from the Earth with the help of powerful telescopes.
The Earth: The Earth is the fifth largest planet in size and the third nearest planet to the Sun. The shape of the Earth is called Geoid because of its slightly flattened shape at the poles.
- The Earth is a unique planet in the solar system because it is the only planet where life exists. The conditions that are favorable to support life on the Earth are * The Earth is neither too hot nor too cold.
- It has water and air, which are very essential for our survival.
- The air of the Earth has life-supporting gases like oxygen.
- The Earth is known as a blue planet because two-thirds part of its surface is covered with water and this makes it look blue from outer space.
- The Moon
- The Moon is the only natural satellite of the Earth. The Moon has no life due to the absence of life-supporting conditions.
- The surface of the Moon is covered with plains, mountains, and depressions which form shadows on the Moon’s surface. These shadows can be observed on full Moon day.
- The Moon is 3,84,400 ions away from the Earth. The diameter of the Moon is only a quarter of the Earth. It looks bigger due to its closeness to the Earth than other celestial bodies.
- The Moon moves around the Earth in about 27 days, ft takes exactly the same time to complete one spin. This makes only one side of the Moon visible from the Earth.
- The Moon is visible on most of the days. It may appear in different shapes, times, and positions. The full Moon appears only once in a month which is called full Moon night or Poornima.
- However, after a fortnight, the Moon can not be seen at all. This is the new moon night or Amavasya. On this night one can observe a clear view of the sky.
Knowledge Plus: Neil Armstrong was the first man to step on the surface of the Moon on 20th July 1969.
Asteroids: A large number of small celestial bodies are found between the orbits of Mars and Jupiter that move around the Sun. These bodies are called asteroids.
Scientists believe that asteroids are the parts of a planet, which are formed by the explosion of planets many years ago.
Meteoroids: The small pieces of rocks that move around the Sun are called meteoroids. Sometimes, they come close to the Earth and drop upon it.
- During this dropping, they get heated up and burn due to friction with the air.
- This causes a flash of light. Sometimes, meteors do not get burned completely and fall on the Earth’s surface creating a hollow.
CBSE Notes For Class 6 Geography Chapter 1 1-3 Galaxy
- A galaxy is a huge system that contains billions of stars, gases, and clouds of dust. The solar system is a part of the Milky Way Galaxy.
- This galaxy is a cluster of millions of stars that appear as a glowing path across the sky on a clear night.
- This Galaxy was named Akash Ganga as it was believed to be a river of light flowing in the sky. The universe comprises millions of galaxies.
- It is very difficult to find out the size of the universe because of its huge expansion.