NIOS Environment Important Notes Part 1 for AEES, KVS, NVS, DSSSB, UPTET, REET, CTET, BTET, MPTET, HTET and All other Teaching Exams
Origin of Earth and Evolution of The Environment
- We live on a beautiful planet called earth, along with a wide variety of plants, animals and other organisms.
- Our earth, however is a part of a vast universe. The universe is about 15 to 20 billion years old. The age of the earth is approximately 4 to 5 billion years, while human beings evolved around 2 million years ago.
Earth as part of the Universe and the Solar System
- Our earth, with all the diversity along with other planets and their satellites, the sun, the moon, the many galaxies (huge groups of millions of stars) form the universe. There are also countless asteroids and comets in orbit around the sun. All these are also part of the universe.
- When you look up at the sky on a clear night, you see many points of light- most of which are stars.
- Stars are huge balls of bright, hot glowing gases.
- The ‘Sun’ is also a star. It is the star nearest to earth- about 150 mk (million kilometers) away.
- A solar system consists of a star in the middle with a number of planets orbiting around it.
- The earth is a part of its solar system. It is one of the eight planets of the solar system that has the sun (a star) in the middle and the eight planets moving around it.
- Until recently solar system was believed to have nine planets. However, on the basis of the latest scientific assessment, Pluto, is no longer regarded as a planet of earth’s solar system.
Origin of the Universe and origins of the Earth
- The widely accepted theory of the origin of universe is the ‘Big Bang’ theory.
- According to this theory, universe started with a huge explosion and matter (dust and gases) filled the
entire space. - The temperature of the universe then, was about hundred billion degrees
Celsius. Scientists believe that the big bang occurred about 15 to 20 billion years ago. - The
huge collection of dust and gases then began to spin. As it spun faster and faster, the center
became very hot. It became the Sun. From the edges of this ball of dust and gas, big blobs
or chunks of dust broke off and formed eight ball shaped planets. This founded our solar
system. - The earth broke off about 4.5 billion years ago with an explosion. It was
a burning hot white mass of gas and dust. Over a long period of time, dust and gas gradually
condensed to form solid rock. Such condensation and shrinking made the earth heat up so
much that the rock melted into a gluey liquid. After millions of years, the outer surface of
the earth or the earth’s crust cooled and formed hard rock again, just as melted chocolate
or wax solidifies upon cooling. The interior of the earth is still very hot.
- The crust of the earth was formed from cooling and hardening of the molten matter and
hot gases. With cooling of the earth the crust hardened and formed the land. Cooling of the
earth also condensed water vapour into liquid water filling the depressions to form seas.
Click here for Part 2