The Cosmos or the Universe consists of millions of galaxies. A Galaxy is a huge congregation of stars which are held together by the force of  gravity. Most of the galaxies appear to be scattered in the space in a  random manner, but there are many galaxies which remain clustered into groups. Our own Galaxy called The Milky Way or Akash Ganga, which appears to have river of bright flowing through the sky, belongs to cluster of some 24 Galaxies called the "local group". The Milky Way is made up of over a hundred billion sparkling stars, which, though quite distant from one another, seem from the earth as having been placed close together. The two other galaxies are the Large Magellanic Cloud and the  Small Magellanic Cloud, Named after Magellan, who discovered them.

The Universe is infinite, both in time and space. Its age was formerly believed to be between 10-15 billion years, however in 1999, a NASA's Hubble Space Telescope project Team determined the age of cosmos to be 12 billion years.

1. The Sun and the stars are motionless;

2. the Sun lies at the center of the universe and the stars at its circumference;

3. the Earth rotates on its axis taking 24 hours to complete  one rotation; and

4. the Earth and the planets revolve around the sun; and moon revolves around the Earth.

Later Galileo, too, with his newly invented telescope demonstrated the validity of the Copernican system through his studies of the phases of Venus and the moons of Jupiter that Earth did revolved around the sun. He discovered many new stars and proved that sensory appearances could be deceptive and that our own limitations of perceptions and reason that place boundaries around the universe.

Isaac Newton demonstrated that forces of gravitation linked all material bodies in an immense universe and showed that these bodies moved in accordance with strict mathematical laws.

The perception of universe was further widened in the 19th century when British astronomer, Hershel, came out with his observation that the universe was not limited to the Solar System, but it is much waster that that. The solar system was only a small part of the much bigger star system, called the Galaxy.

The vision of the Universe got further expanded in the 20th century when, in 1925, an American astronomer, Hubble, made a connection that apart from the milky way and the other two known galaxies, viz., Large Magellanic Cloud and the  Small Magellanic Cloud, there were other galaxies in the universe whose number ran in millions, each galaxy containing billions of stars. And each star is like our sun, the center of solar system.

Thus gone are the days of a finite two-sphere geocentric system of universe in which the earth occupied a key position. The Earth is just a planet of the solar system and there are millions and billions of such systems existing in the skies, some of which have been discovered, while many others remain unobserved. Efforts are continuing to unfold the miseries of the universe, several new galaxies have been discovered, but many million others remain undetected so far.