The Earth is the most suitable planet to support life. It has three major Components that we call as the realms of The Earth- lithosphere, hydrosphere and Atmosphere. The three components along With suitable climate make life possible on Earth. All living things exist in a narrow Zone called the biosphere. Now let us have A close look at each of the spheres

Lithosphere:

The word lithosphere is derived from The Greek word Lithos, which means Rocky. The Lithosphere is the land on which we live. It is the solid outer layer Of the Earth consisting of rocks and soil.

Hydrosphere:

The word Hydro means water in Greek. The hydrosphere consists of water Bodies such as oceans, seas, rivers, lakes, Ice caps on mountains and water vapour in the atmosphere.

Atmosphere:

The word Atmo means air in Greek. Atmosphere is the envelope of air that surrounds the Earth. Different types of Gases make up the atmosphere. The Major gases are Nitrogen (78%) and Oxygen (21%). The other gases like Carbon dioxide, Hydrogen, Helium, Argon and Ozone are present in meager Amounts.

Biosphere:

The narrow belt of interaction among the lithosphere, the hydrosphere and the Atmosphere, where life exists is known As Biosphere. Bio means life in Greek. It consists of distinct zones. Each zone has its own climate, plant and animal life. These Zones are known as ecosystems.

Directions:

The directions on the ground are always shown with respect to the North. If we know the North, then it is easy to find the other directions, namely South, East and West. These are the four cardinal Directions

We know that the Sun rises in the East and sets in the West. If we stand facing the sun in the morning, then we face the East. The west is towards our back. The Left hand points towards the north and the Right hand points towards the south. We should always keep this in mind.

Globe:

We live on the planet Earth, which is found third from the Sun. Since the Earth is Huge and we live on a very small area, we are not able to see the Earth as a whole. But, when we travel to space, we can see The Earth as a whole.

So, in order to see the shape of the Earth as a whole and to know its unique Features, a three dimensional model of the Earth was created with a specific scale.The surface area of the Earth is 510.1 million Square kilometres.

The Earth which is spherical is flat at the poles and bulges at the Equator. The Earth cannot be compared with any other Geometrical shape as it has a very unique Shape. Hence, its shape is called a geoid (earth shaped).The Earth moves around the Sun. It Also rotates from the West to East on its Axis at an inclination of 23 ½°. The globe is also inclined at an angle of 23 ½°. The Axis is an imaginary line. It is not actually found on the Earth.

Lines on the Globe:

There are imaginary lines which Are drawn on the globe horizontally and vertically to find a location and calculate Distance and time. These imaginary lines are Called lines of latitudes and longitudes.

Latitudes:

The imaginary lines which are drawn horizontally on East – West direction on the Earth are called the lines or parallels of Latitudes. The 0° line of latitude which divides The Earth into two halves is known as the Equator. From the Equator, parallel lines are drawn towards the North and South Poles at equal intervals. The latitudinal Extent between 1° lines of latitude on Earth Is 111 km. Since the Earth is geoid shaped, the Length of the lines of latitude decreases From the Equator towards the South and North Poles. The 90° North and South Poles Are not found as lines, but as points.The lines of latitude that are drawn Horizontally between the Equator and the North Pole are called ‘Northern latitudes’And those which are found between the Equator and the South Pole are called ‘Southern Latitudes’.The lines of latitude consist of 89Parallels in the Northern Hemisphere and 89 parallels in the Southern Hemisphere, One at the Equator and the two poles Are found as points. Totally, there are 181 Parallels found on earth.

The Equator is the longest of all lines of latitude. Hence, it is also known as ‘The Great Circle’.

The area of the Earth found between The Equator (0) and the North Pole (90°N) is called the Northern Hemisphere.

The location of any country or place is based on this division of the hemispheres.

Important lines of latitude:

The earth rotates on its axis at an Inclination of 23½°. It also revolves around the sun while rotating. Based on the angle at which the sun’s rays fall on the earth, certain lines of latitude gain significance.

The Sun’s rays do not fall equally on all Parts of the earth. They fall vertically over The Equator and slanting towards the poles. Thus, all the places on earth do not have The same amount of temperature. Based On the amount of heat received from the Sun, the lines of latitude help in dividing the earth into different climatic zones.

Torrid Zone:

The region from the Equator towards The Tropic of Cancer (23½°N) and the Tropic Of Capricorn (23½°S) is called the Torrid Zone. The Sun’s rays fall vertically over this Region and the average temperature is very high. Hence this region is known as the Torrid Zone.

Temperate Zone:

From the Tropic of Cancer (23½°N) To the Arctic Circle (66½°N) and from The Tropic of Capricorn (23½°S) to the Antarctic Circle (66½°S), the Sun’s rays fall Slantingly. Moderate temperature prevails In this region. Hence, this region is called Temperate Zone.

Frigid Zone:

From the Arctic Circle (66½°N) to the North Pole (900N) and from the Antarctic Circle (66½°S) to the South Pole (90°S), The Sun’s rays fall further inclined, through Out the year. The temperature is very low. Hence, this region is known as Frigid Zone.

Longitudes:

The imaginary lines drawn vertically connecting the North Pole and the South Pole are called lines or meridians of Longitude. These lines of longitude are Seen as semi circles.

The 0° line of longitude is called the Prime Meridian. There are 180 lines Of longitude towards the East and West From the Prime Meridian. So, there are Totally 360 lines of longitude. These Lines converge at the poles. The 180° W And 180° E line of longitude are the same Line.

The lines of longitude that are found Between the Prime Meridian and the 180° East line of longitude are called‘Eastern Longitudes’ and the lines of Longitude that are found between the Prime Meridian (0°) and the 180° West Line of longitude are called ‘Western Longitudes’. Two opposite meridians Form a great circle.

The lines of longitude:

Are found as semi circles Covering 111 km at the Equator, 79 km at 45° latitude and no Space between the lines at the poles.

Eastern Hemisphere:

The part of the Earth between the 0° Line of longitude and the 180° East line Of longitude is known as the Eastern Hemisphere.

Western Hemisphere:

The part of the Earth from 0° line of Longitude to 180° West line of longitude is called as Western Hemisphere

Significant Lines of Longitude:

Greenwich Meridian The Royal Astronomical Observatory is Located at Greenwich near London in England. According to the International Meridian Conference held in 1884 inWashington DC in the U.S.A. all nations  Agreed on choosing the Greenwich Meridian As the international standard meridian (0°). This line of longitude is called the Prime Meridian and it is also known as the Greenwich Meridian because it passes Through Greenwich

International Date Line:

The 180°E Line of longitude has been Fixed as the International Date Line, drawn On the Pacific Ocean between Alaska and Russia through Bering Strait. If a person Crosses this line from the West to East, he Loses a day. On the other hand, when he Crosses from the East to West, he gains a Day. Based on this, the date is fixed for Different countries or regions of the world.

Longitude and Time:

 As many as 360° lines of longitude Are drawn to connect the North and South Poles around the Earth 180° on the Eastern Hemisphere and 180° on the Western Hemisphere. Time is calculated on the Basis of the lines of longitude.

The Earth takes one day to Rotate on its axis.

1. 1 day = 24 hours
2. 1 hour = 60 minutes
3. 24 hours = 24 x 60 = 1440 Minutes
4. The angle of the earth = 360 °
5. 360 ° = 360 ° Longitudes
6. 360 ° = 1440 minutes
7. So 1 ° = 1440 / 360 = 4 minutes
8. In 4 minutes = 1°rotation
9. In 60 minutes = 60/4 = 15° Rotation
10. So, in an hour (60 minutes) the Earth rotates 15°

Local Time:

When the sun is overhead on a Particular line of longitude, it is 12 noon At all the places located on that line of Longitude. This is called local time.The Sun is overhead on a line of Longitude only once in a day. So the local Time differs for every line of longitude.When the Sun is overhead the Greenwich Meridian at 12 noon, it is the Local time of that place. The world time is Calculated by this standard line of longitude. It is known as the Greenwich Mean Time (GMT).For example, if the time is 12 noon at Greenwich Meridian, it is 12:04 p.m. at 1°E line of longitude and 11:56 a.m. at 1°W line of longitude. So, as one moves Towards the east from any meridian the time Increases. And if one moves towards the West from any meridian, time decreases.

Standard Time:

Local time is calculated when the sun is Overhead at noon. Many lines of longitude May pass through a country. Countries may Or may not observe a common time. The Standard time of a country or a part of it iscalculated keeping a particular meridian As a standard one. The meridians are selected in multiples Of 15° or 7 ½°. It is done in such a way That the variation of standard time from the Greenwich is expressed either as 1 hour or ½ an hour.

The longitudinal extent of India is from 68°7’ E to 97°25’ E. As many as twenty Nine lines of longitude pass through India. Having 29 standard time is not logical. Hence 82½° E line of longitude is observed As the Prime Meridian to calculate the Indian Standard Time (IST).

The 82½°E line of Longitude passes through Mirzapur near Allahabad In Uttar Pradesh. This is located at An equal distance from GhuarMota In Gujarat and Kibithu in Arunachal Pradesh.

Time Zones:

The world has 24 time zones. Some Countries have a great longitudinal extent. So they have more than one standard time. Example: Russia has 7 time zones.