SHORT NOTES ABOUT OUR EARTH, Summaries of Geography

Download SHORT NOTES ABOUT OUR EARTH and more Summaries Geography in PDF only on Docsity! History of Our Earth BANARAS HINDU UNVERSITY History of Our Earth Practice Essay Formation of Our Earth Our Earth  Earth is the third planet from the Sun.  Large volumes of water can be found throughout the Solar System, About 71% of Earth's surface is made up of the ocean.  Only Earth sustains liquid surface water.  Distance from Sun - 149.6 million km  Age – 4.543 billion years  Radius - 6,371 km Formation of Our Earth  Earth formed around 4.5 billion years ago.  In the beginning, all matter forming the universe existed in one place in the form of a “tiny ball” (singular atom) with an unimaginably small volume, infinite temperature and infinite density.  At the Big Bang the “tiny ball” exploded violently. This led to a huge expansion. It is now generally accepted that the event of big bang took place 13.7 billion years before the present.  The expansion continues even to the present day.  As it grew, some energy was converted into matter.  There was particularly rapid expansion within fractions of a second after the bang.  The expansion has slowed down. Within first three minutes from the Big Bang event, the first atom began to form.  Within 300,000 years from the Big Bang, temperature dropped to 4,500 K (Kelvin) and gave rise to atomic matter. The universe became transparent.  The expansion of universe means increase in space between the galaxies. An alternative to this was Hoyle’s concept of steady state. It considered the universe to be roughly the same at any point of time. However, with greater evidence becoming available about the expanding universe, scientific community at present favours argument of expanding universe. BIG BANG THEORY  Edwin Hubble is a Father of Big Bang Theory.  He provided evidence that the universe is expanding in 1920.  The Big Bang Theory is also called expanding universe hypothesis, galaxies move further and further apart. Land - There are over 510 million square kilometers of area on the surface of Earth, but less than 29% of this is covered by land. Ocean - The creatures on the earth are lucky that it is a water planet, otherwise we all would have no existence. Water is a rare commodity in our solar system. There is no water on the sun or anywhere else in the solar system. Fortunately has an abundant supply of water on its surface. Hence, our planet is called the ‘Blue Planet’. Air - Our earth is surrounded by a huge blanket of air called atmosphere. It provides us the air we breathe. COMPOSITION OF THE ATMOSPHERE (1) Helium (2) Ozone (3) Argon (4) Carbon dioxide (5) Hydrogen are found in lesser quantities. (6) A part from these gases, tiny dust particles are also present in the air. Environment - Environment is our basic life support system. It provides the air we breath, the water we drink, the food we eat and the land where we live. . It is a combination of natural and human made phenomena. The natural environment refers to both biotic and abiotic: (1) Biotic: The world of living organisms. Example- plants and animals. (2) Abiotic: The world of non-living elements. Example- land.