UniverseUniverse is said to be the whole of space along with all the starts, planets, and other forms of matter and energy it contains. We inhabit the planet Earth which is only a small part of our Solar System. Our planet is also referred to as the World in comman parlance. Sun is only a star and there are countless stars in the Universe.
In simple terms, the Universe is comprised of matter, energy and life.
The Changing Concept
The concept of Universe has been changing with the change of time. It was first conceived of as and orderly unit. That is why the system of the Universe was called COSMOS.
The first institutional effort to explore the Universe was initiated in AD 140 by Claudius Ptolemy. He was a Graeco - Egyptian atronomer.
He propounded the theory - The Earth is the centre of the Universe and the Sun and other heavenly bodies revolve around it. However, he proved wrong later.
There were many theories, mainly in religious scriptures, are found even before Ptolemy's theory. In one of the Upanishads, there is a story of a Teacher and his disciple. The disciple asked,"why it is so that the sun sets and rises again?" The teacher replied,"The Sun neither rises nor sets, it is the Earth that moves." (One can read Upanishads in English translated by Max Muler, a German Indologist). It was just speculative wisdom of ancient India, which was found true later in 14th 15th and 16th centuries by western astronomers independently through empirical studies.
Polish astronomer Copernicus argued in 1543 that the Sun, and not the Earth, was the centre of the Universe. His meaning of Universe was still our Solar System. However, there is a theory in Vedas that tells us about Brahmand which means the whole space (Our Solar system, and outer space including stars, milky way et all) and everything inside it. This Brahmand is equivalent to the present day meaning of the Universe, which was never created, and was existed in Brahma, who simply brought it out, and ultimately the Universe will return to that position in Brahma, and again will come out of Brahma. This cycle of the Universe is to continue everlastingly, says this theory.
It was in 1805, when we came to know through empirical studies that the Universe was not confined to the solar system. This contribution was made by a British astronomer Herschel through telescopic studies of the space. The findings suggested that the solar system itself was only a part of a much vaster star system called galaxy.
In the earlier dacaded of 20th century it was believed that there was only one galaxy. However, in 1925, the American astronomer Edwin P Hubble (1889 - 1953) suggested that the Universe was consited of millions of galaxies like the Milky Way. He proved in 1929 that these galaxies are flying away from each other and that the farther they are, the faster they fly. It meant that the Universe is expanding. It is also on the assumption that matter is in a state of rapid expansion.
How was the shape of the Universe
According the earliest theories in Vedas, it was like Egg, and perhaps for this reason it was called Brahmand.
However, today, it is generally assumed that our universe started out as a superdense ball.
We do not know how exactly this universe began. According to the Vedas it never bagan and will never end. It is everlasting with the forms altered.
It was never been created out of nothing, because nothing could be created out of nothing. There always existed something. There has never been a time when nothing existed and there will never be a time when nothing will exist. Therefore, the question of beginning of the Universe is ruled out. One can only accept that there might be a time when the Universe might have a shape of superdense ball. However, that cannot be the point of beginning.
The Big Bang Theory
A Belgian astronomer - priest, Abbe Georges Lemaitre explained the theorey of expansion of this superdense ball which is known as the Big bang theory. Billions of years ago, the cosmic matter or the universe, was in extremely compressed state, from which expansion started by a primordial explosion. It cast its fragments far out into space, where they are still travelling.
According to Dr Sandage, such an explosion occurred some 12 billion years ago, and the expansion is likely to go on for 29 billion years more, when gravitation will halt further expansion. He says, from then on, all matter will begin to contract or collapse upon itself in a process of implosion. The process of implosion will go on for another 41 billion years to return again to a superdense state, and then it will explode once again. More and more scientists are in favour of this theory.
The Continuous creation theory
Two astronomers, Thomas Gold and Hermann Bondi, advanced this theory and got support from other important astronomers like Fred Hoyle. This theory says that galaxies recede from one another but their spatial density remains constant. It meant, as old galaxies move apart new galaxies are being formed in the vacancies. These new galaxies are formed from new matter which is being continuously created to replace old matter that is being dispersed.
The Pulsating or Oscillating Universe theory is being advocated by many including Dr Alan Sandage. According to this theory the universe expands and contracts alternately between periods running into tens of billions of years.
Universe in Hindu mythology