NCERT Class 6 Geography Chapter 1 Notes

Sun

• Head and center of the solar system.
• Made of extremely hot gases.
• Source of heat and light for us.
• 150 million km away from the Earth.

Planets

• Eight planets move around the Sun in a fixed path called orbits.
• Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
• Earlier Pluto was considered a planet but now it is categorized as a dwarf planet.
• Mercury is the nearest and Neptune is the farthest.
• Venus is considered the twin planet of the Earth.
• The first four planets are called inner planets.
• The last four planets are called outer planets.
• Jupiter is the biggest and Mercury is the smallest planet.

Earth

• The earth is the third nearest planet to the sun.
• In size, it is the fifth-largest planet.
• Life is only found on Earth to date. Earth has life-supporting conditions. As it is neither too hot nor too cold.
• Earth is called a blue plant because of the ~70% water cover over the surface.
• Earth has an atmosphere to protect us from the harmful radiation from the Sun.
• Earth has one natural satellite which moves around the earth. It is called the Moon.
• It is slightly flattened at the poles. That is why its shape is described as a Geoid. Geoid means an earth-like shape.
  • Geo or Ge – the Greek word for Earth.

Moon

• The diameter is one-fourth of the earth’s diameter.
• The moon takes 27 days to complete one circle around the Earth and the same time it takes to complete one spin about its axis.
• It is 3,84,800 km away from the earth.

Celestial Bodies

We all observe many twinkling stars, different shapes of the Moon, the Sun in the Sky. Sometimes at night, we see shooting stars. Similar to our planet earth we have other planets and dwarf planets.

All these stars, planets, satellites, asteroids, meteoroids comets, etc. are called celestial or heavenly bodies.

 All these stars have their own light and heat. They emit their light and heat in the form of radiations. If their reach us then we are able to see them otherwise they will not be visible to us. The Sun is also a star.

Why are the stars not visible during day time?

Because the Sun is the nearest star for us and its light reaches to the Earth and gets scattered all around us during the day time. In the sunlight, we are not able to see the other distant stars. During the nighttime, the Sun is on another side of the Earth. At this time lights from other stars reach us and we can see them during the night time.

Why do the stars appear twinkling?

Stars emit their light. When this light reaches us we are able to see the stars. But once the light enters our atmosphere it has to pass through various layers of the atmosphere. There are various gases with different densities and temperatures. While passing through these gases, the path of the light gets deviates multiple times. Because of this deviation in the path, we see the stars twinkling.

Why does the sky appear blue in the daytime?

Sunlight is made of various different colors (have you seen a rainbow?). Each color has different properties. When the light passes through the atmosphere it gets scattered because of the small particles present in the atmosphere. Blue and Violet colors are scattered more than other colors. And our eyes are more sensitive towards the blue color. Hence, the sky appears blue to us during the daytime.

Constellations

Various patterns formed by the group of stars are called constellations. There can be so many patterns. Our imaginations can match these patterns with any shape. There are some famous and easily recognized patterns i.e. Ursa Major and Ursa Minor.

For example,
Ursa major – also called as big or the great bear constellation
Ursa Minor – also called as a small bear constellation

These patterns are observed in the north direction over the north pole. The Indian name of the Ursa Minor constellation is Saptarishi means seven sages – a group of seven stars.

Polaris Star

It is a bright shiny star found in the north direction and it is a part of the minor constellation (Saptarishi). It has a fixed position. Since it is over the north pole of the Earth, hence it is called the Pole star. In ancient times, people used this star to figure out the directions during night times. Indian Hindi’s name for this star is Dhruv Tara.   

Moon

Moon is the natural satellite of the Earth. It moves around the Earth and also rotates or spins about its axis. It takes about 27 days to complete one revolution and also one rotation. Therefore we see the different shapes and sizes of the moon during a month. When the Moon is fully visible to us, we call is it Full Moon night (Poornima in Hindi). When it is not at all visible to us, we call it New Moon night (Amavasya in Hindi) because the next day onward we start seeing the moon again. Our Indian Hindi Calendar follows the Moon for deciding the days. Similarly, we have other celestial bodies like asteroids, comets, meteoroids, etc. Please follow the below link to read about them in another article on the Universe.

Class 6 Geography Chapter 1 Online Test