--6.SOLAR SYSTEM:

The solar system includes nine planets and sun being at the centre.All the planets revlove around teh sun .The solar system also includes the asteroids,meteors and numerous comets.All of these travel around the sun in a particular orbit .The planets which are the significant part of the solar system namely,Mercury,venus,earth,mars,Jupiter,Saturn<ur anus,neptune and the pluto.

All the theories about teh formation of teh solar system agree on two facts.One is that the age of solar system is 4.5billion years and secondly the planets were formed from the gas and dust within the vicinity of the sun.The gas and dust condensed into tiny bodies which eventually built up the present day planetary system.

MOTION OF THE PLANETS

The planets perform two types of motions.
1,rotation at tehir axisis
2.revolution or the orbital motion along their orbits around the sun.

THE AGE OF THE SOLAR SYSTEM:

Meteoric evidence suggests that the solar system is 4530+20 million years old.and that was formed in less than 25 million years.
The solar system is believd to be formed from a globe of gas and dust that consisted mainly of hydrogen

--7.THE SUN

The sun is the most significant star for the existence and life of living beings on earth.The whole life on earth depends on this brightest object in the sky.The living things get their energy from sun and the appropriate distance of earth from sun maintains an appropriate temeprature which is ideal for the survival of all the life present on earth.
The sun is the principle source of energy for all the planets of the solar systems .Through a constant stream of particles that flow outward from the sun ,heat,radiation,light and UV rays are emitted.the UV rays that reach the earth from sun are considered to be the most harmful ones.Most of the UV and other high energy radiation are absorbed by the Ozone layer and the atmosphere of the earth.This stream of particles is called solar wind.

STRUCTURE OF THE SUN:

The visible surface of the sun is called photosphere which is a turbulent region and is 570 kilometere deep.
The layer outside the photosphere is chromosphere which is a broad layer and is several miles thick.
The outside layer of the sun is corona.Energy released by the sun passes from chromospher to the corona and then to the outer space.

--8.EARTH:

The third farthest planet from the sun is earth.The earth rotates on its axis in about 24 hours.The diametre of earth is 12756 km.The earth completes its rotation along its axis in 23.9 hour and one tip along its orbit in 365 days,6 hours and 9 minutes and 9.4 seconds.The orbit of the earth is not a circle but a ellipse .

STRUCTURE OF THE EARTH:

The earth has four major structural components.
1.The Crust
2.The Mantle
3.The Outer core
4.The Inner Core.

THE CRUST:The upper most layer of the earth is called the crust.A solid and a complex layer of the lithosphere in both physical and chemical nature.The crust is composed of wide variety of rocks which are known as sedementry rocks .The crust is further divided into ocean crust and continental crust.

THE MANTLE:According to the various kinds of scientific evidneces the upper mantle of teh earth is made up of silicate minerals.The temperature increases rapidly with depth in outer of the earth.Due to high temperatures the rocks start melting .These molten rocks form the basis of lava which erupt from ocanic volcanoes.

THE CORE:The core starts where marked physical and chemical changes occur across the vore mantle boundries.The outer core is thought to be made of mixture of melted iron and nickle.In the inner core the mixture is thought to be nickle and iron alloy.

ATMOSPHERE OF THE EARTH:

The chief gases in the atmosphere of the earth are,
Nitrogen 78.09%
Oxygen 20.95%
Argon 0.93%

The remaining 0.03% is made of carbon dioxide,small quantities of neon,helium,ozone and hydrogen and minute traces of krypton,methane,xenon and other gases.
Another important constituent of the atmosphere is water vapour which makes up 4 percent by volume and 3 percent by weight.
Life is not possible without the atmosphere of the earth Oxygen present in the atmosphere is necessary for both animals and plants for respiration.Carbon dioxide is needed by teh plants which use this gas in the process of photosynthesis.Water vapours present in the earth are necessary for the process of rain and otehr percipitation.
The atmosphere is a valuable natural source of many gases that are widely needed in industry,argon for the purpose of welding and oxygen is required for hospitals and other metal industries.
the earth's atmosphere alo posseses the protective role against the dangerous UV rays and other high radiative energy from space.The atmosphere of the earth absorbs these rdiations which are a cause of various health hazards.

--9.MINERALS

A mineral is an inorganic substance formed naturally.They are infact building blocks from which rocks are made and they may form crystals.
Minerals are produced by the physical force of the earth.They are the basic units of rocks .Every rock can be considered as the accumulation of minerals.geologists classify rock principally according to the way which they are formed ,not according to their composition as most rocks consists of two or more than two different minerals.

As rocks are formed by minerals,therefore there are three kinds of rocks igneous,sedimentary and metamorphic.

The igneous rocks are formed when the molten magma cools and solidifies .
The sedimentary rocks originate from the deposits of material worn away from the plants and animals and also by the pre existing rocks.
Metamorphic rocks are formed by the alteration of pre existing rocks by great heat or pressure.

The abundent element in these rocks is oxygen and silicon.because of this the mineral silica is very often found in the rocks.In the rocks the silica is combined with other elements such as aluminium,calcium,iron,magnesium,pottasium,or sodium.