INTRODUCTION

The word Universe is derived from French word “Univers”, which means “All turned into one”.  The Universe is everything that we can perceive.  In 1927, the Belgian priest Georges Lemaitre proposed that the Universe began with the explosion of a Primeval atom, which he called this as “BIG BANG THEORY”, his proposal came after observing the Red shift in distant nebulas.  The Red shift, in simple means, the displacement of spectrum lines towards the red end of the visible light.  Years later, Edwin Hubble found experimental evidence to help justify Lemaitre’s theory.  He found that distant galaxies in every direction are going away from us with speeds proportional to their distance.  Finally, the big bang theory received its strongest confirmation when Radiation was discovered in 1964 by Arno Penzias and Robert Wilson, who later won the Nobel prize for this discovery. 

    The Universe is the vast and infinite space having millions of galaxies.  It is estimated that the age of our universe is between 15 and 20 billion years old.  The three most common elements in the universe are: 1. Hydrogen 2. Helium and 3. Oxygen.  However, Hydrogen comprises around 90 percent of all matter in the universe.  About 70 percent of the universe has dark energy and 25 percent consists of dark matter.  It is only 5 percent of the universe is visible to us. 

The Origin of the Earth

Our solar system is a small part of the system of stars collectively called Milky way.  It consists of more that thousands million of stars.  Like other stars, the Sun with its solar system is revolving around the centre of the Milky way, there are several theories which explain the formation of the solar system, in which earth is a part.  These theories can be broadly classified under two groups called Catastrophic and Non catastrophic theories. 

The catastrophic theories like

Planetesimal Hypothesis of Chamberlin

Binary star Hypothesis of Russell and Littleton

Super Novae Hypothesis of Hoyle

Tidal Hypothesis of James Jeans

     The Non-catastrophic Hypothesis like
 Gaseous Hypothesis of Immanuel Kant
 Nebular Hypothesis of Laplace.