The Earth is the third planet from the Sun and the only place that’s inhabited by living things. It is the fifth-largest planet in the solar system, and it is the only world with liquid water on the surface. Among all the four planets closest to the Sun, the Earth is the biggest planet. The solar system consists of our star, the Sun, and everything bound to it by gravity – the planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune, dwarf planets such as Pluto, dozens of moons and millions of asteroids, comets and meteoroids. Below we have provided CBSE Class 6 Geography notes for Chapter 1 – the Earth in the Solar System so that students can learn the concepts more quickly.
At night the whole sky is filled with tiny shining objects some are bright, others dim. They all appear to be twinkling. A full moon occurs once in about a month’s time called Full moon night or Poornima. A fortnight later, you cannot see the moon at all which is called New moon night or Amavasya.
Celestial bodies – The sun, the moon and all those objects shining in the night sky are called celestial bodies. Some celestial bodies are very big and hot. They are made up of gases.
Stars – Stars are celestial bodies which have their own heat and light, which they emit in large amounts. The sun is a star.
Constellations: In the night sky, various patterns are formed by different groups of stars called constellations. Ursa Major or Big Bear is one such constellation.
One of the most easily recognisable constellations is the Saptarishi (Saptaseven, rishi-sages). It is a group of seven stars that forms a part of Ursa Major Constellation.
In ancient times, people used to determine directions during the night with the help of stars. The North star indicates the north direction. It is also called the Pole Star. It always remains in the same position in the sky.
Planets – Planets are celestial bodies that do not have their own heat and light. They are lit by the light of the stars. The word ‘planet’ comes from the Greek word “Planetai” which means ‘wanderers’.
The earth on which we live is a planet. It gets all its heat and light from the sun. The moon that we see in the sky is a satellite. It is a 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.
The Solar System
The sun, eight planets, satellites and some other celestial bodies known as asteroids and meteoroids form the solar system.
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. The sun is the ultimate source of heat and light for the solar system. The sun is about 150 million km away from earth.
There are eight planets in our solar system. In order of their distance from the sun, they 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 called orbits. Mercury is nearest to the sun. It takes only about 88 days to complete one round along its orbit. Venus is considered as ‘Earth’s-twin’ because its size and shape are very much similar to that of the earth. Till recently (August 2006), Pluto was also considered a planet. However, in a meeting of the International Astronomical Union, a decision was taken that Pluto, like other celestial objects (Ceres, 2003 UB313) discovered in recent past may be called ‘dwarf planets.”
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. The Earth shape is described as a Geoid. Conditions favourable to support life are probably found only on the earth. It has water and air, which are very essential for survival. The air has life-supporting gases like oxygen. From the outer space, the earth appears blue because its two-thirds surface is covered by water. It is also called a blue planet.
Moon is the earth’s satellite. Its diametre is only one-quarter 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. 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 moon’s surface.
Asteroids are tiny bodies that move around the sun. 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.
The small pieces of rocks 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.
A cluster of millions of stars is called the Milky Way galaxy. Our solar system is a part of this galaxy. In ancient India, it was imagined to be a river of light flowing in the sky. Thus, it was named Akash Ganga.
Galaxy – A galaxy is a huge system of billions of stars, and clouds of dust and gases. There are millions of such galaxies that make the Universe.