IAS Prelims (GS) Preparation 2018
Day # 11 (April 3, 2017)
Topics of the Day: Geography – NCERT 6th standard chapter 1 to 4 (key points)
Chapter - 1
-The sun, the moon and all those objects shining in the night sky are called celestial bodies.
-Stars are celestial bodies which have their own heat and light and emit it in large amounts.
-The sun is a star.
-Various patterns formed by different groups of stars are called constellations.
-Ursa Major or Big Bear is one such constellation.
-One of the most easily recognisable constellation is the small bear or Saptarishi(Saptaseven, rishi-sages). It is a group of seven 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. We can locate the position of the Pole Star with the help of the Saptarishi.
-Some celestial bodies do not have their own heat and light. They are lit by the light of the stars. Such bodies are called planets.
-The word ‘planet’ comes from the Greek word “Planetai” which means ‘wanderers’.
-The moon is a satellite. It is a companion of our earth and moves round it.
-The sun, eight planets, satellites and some other celestial bodies known as asteroids and meteoroids form the solar system.
-‘Sol’ in Roman mythology is the ‘Sun god’.
-Those who study the celestial bodies and their movements are called astronomers.
-Aryabhatta was a famous astronomer of ancient India.
-Sun provides the pulling force that binds the solar system.
-The sun is about 150 million km away from the 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.
-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.
-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. That is why, its shape is described as a Geoid. Geoid means an
earth-like shape.
-From the outer space, the earth appears blue because its two-thirds surface is covered by water. It is, therefore, called a blue planet.
-Jupiter, Saturn and Uranus have rings around them. These are belts of small debris.
-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.
-Neil Armstrong was the first man to step on the surface of the moon on 21 July 1969.
-Our earth has only one satellite, that is, the moon.
-Moon is about 3,84,400 km away from our earth.
-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 neither water nor air. It has mountains, plains and depressions on its surface. These cast shadows on the moon’s surface.
-A Satellite is a celestial body that moves around the planets in the same way as the planets move around the sun.
-Asteroids are tiny bodies which move around the sun and they are found between the orbits of Mars and Jupiter.
-The small pieces of rocks which move around the sun are called meteoroids.
-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.
-Our solar system is a part of milky galaxy.
Chapter – 2
-Earth is slightly flattened at the north and south poles and bulge in the middle.
-Globe is a true model of the earth.
-Earth rotates from West to East.
-Equator is an imaginary line divides the globe into 2 equal parts.
1.Northern part is called Northern Hemisphere.
2. Southern part is called Southern Hemisphere.
-All Parallel circles from the equator upto the poles are called Parallels of Latitudes.
-Equator represents the zero degree of latitude.
-90 degree North latitude marks the north pole
-90 degree south latitude marks the south pole.
-One can know the latitude of their place by measuring the angle of the pole star from their place.
-There are four important parallels of Latitudes
a. Tropic of cancer - 23 1/2 degree north in the northern hemisphere.
b. Tropic of Capricorn - 23 1/2 degree south in the southern hemisphere.
c. Arctic circle at 66 1/2 degree north of the equator.
d. Antarctic circle at 66 1/2 degree south of the equator.
-The mid day sun is exactly overhead at least once a year on all latitudes in between the tropic of cancer and the tropic of capricorn. This area receives the maximum heat and is called
the Torrid Zone.
-The angle of the sun rays goes on decreasing towards the poles. therefore the areas bounded by the tropic of cancer and the arctic circle in the Northern Hemisphere and the tropic of capricorn and the antarctic circle in the southern hemisphere have moderate temperature.
These are therefore called temperate zone.
-Areas lying between the arctic circles and the north pole in the Northern hemisphere and the Antartctic circle and the south pole in the southern hemisphere are very cold. These are called Frigid Zones.
-The lines of references running from the north pole to the south pole are called the meridians of longitudes. All these meridians meet at the poles.
-The meridians which passed through Greenwich where the British Royal Observatory is located is called the Prime meridian. Its value is zero degree longitude.
-The shadow cast by the sun is longest at sunrise and sunset.
-The shadow cast by the sun is shortest at noon.
-The sun is at the highest point in the sky when it is mid day.
-The longitude of 82 1/2 degree east is taken as the standard time for a whole country. It is known as the Indian Standard time(IST).
-India is located east of Greenwich at 82degree30minutes is 5hours and 30 minutes ahead of GMT(Greenwich Mean Time).
-The Earth has been divided into 24 time zones of 1hour each.
Chapter 3
- Rotation is the movement of the earth on its axis.
- The period of rotation of earth is known as the Earth day.
- It takes 365 days 6 hours to revolve around the sun.
- Earth goes in an elliptical orbit around the sun.
- On 21 june, the Northern Hemisphere is tilted towards the sun. The rays of the sun fall directly on the tropic of cancer. This position of the earth is called Summer Solstice.
- On 22 December the tropic of capricorn receives direct rays of the sun. This is called Winter Solstice.
- On 21st March and 23rd september direct rays of the sun fall on the equator. This is known as Equinox.
- On 23rd September it is autumn season in the Northern Hemisphere and spring season in the southern hemisphere.
Chapter 4
- The three components of maps are Distance, Direction and Symbol.
- Directions (North, South, East and West) are called Cardinal Points.