· All the matter in the unversed was originally concentrated lump called primeval atom.
· Big bang was an explosion that occurred 15 billion years ago, leading to the formation of galaxies of stars and other heavenly bodies.
· Since then, all the galaxies have been flying away from one another causing expansion of the universe.
STAR
· Clumps of dust and gas in a nebula come together due to gravity and form stars.
· Stars are made of hot burning gases.
· They emit light of their own and are very large and very hot.
· Light takes about 4.3years to reach us from the next nearest star proximal centaury.