The Universe
The word Universe is derived from the old French word Univers. Today, it is perceived as the cosmos. It is commonly defined as the totality of existence and consists of millions of galaxies. Some galaxies are found in clusters into groups where as some appear to be scattered in the Space. Milkyway or Akash Ganga is our own galaxy that belongs to a cluster of 24 galaxies. Over a hundred billion Sparkling Stars appear to have been placed very closely from the earth. The Universe is infinite both in time and space.
In 1999 a Hubble Space Telescope project team of NASA determined the age of cosmos to be 12 billion years against the earlier belief between 10-15 billion years. According to the Microwave Anisotropy Probe launched by NASA, The exact age of the Universe is 13.7 billion years after the theoretical Big Bang. A rational analysis of the earthly and heavenly components and mysteries began in around 6th century BC. All these attempts Contributed significantly for the development of modern scientific theories.
In his book Almagest, Ptolemy a second century Gerco-Egyptian astronomer, presented his system of astronomy. He based his observations on a geo-centric universe and propounded that the Sun and other heavenly bodies revolved round the earth. Most men in the middle ages felt that they lived in a rigidly structured Universe centred round a static Earth. Thus, they strongly supported the System Propounded by Ptolemy.
But a more consistent and authentic system of Universe was propounded by Copernicus (1473-1543) in his famous work on the revolution of celestial bodies. He observed that the sun lies at the centre of the Universe and the stars at its circumference, the earth rotates on its Axis and completes one rotation in 24 hours, the Moon revolves round the earth where as the Earth and the planets revolve round the sun.
A Severe defect in the observation of Copernicus was that it failed to enlarge the limits of the Universe. The Universe still Continued to be believed as only a celestial body equated with the Solar system.
However astronomers like Galileo (1564-1642) and Scientists like Isaac Newton (1642-1727) widened the perception of the Universe in the 16th century and the 17th century. In the 19th century the British astronomer Sir Million Herschel (1738-1822) observed that the Universe was not limited to the Solar System, which was only a tiny part of a much bigger star system, called the Galaxy. He Propounded that the Universe is much vaster than the Solar system. In 1925, Edwin Powell Hubble (1889-1953), an American astronomer propounded that apart from the Milky way and the two other known galaxies, viz, the large magellanic cloud and the small magellanic cloud, there are millions of other galaxies in the Universe and each galaxy contains billions of stars. Hubble discovered that the Universe was actually expanding.
However, the ultimate fate of the Universe is not known. Recent data Suggest that the expansion speed of the Universe is not decreasing as originally expected rather, it is increasing. On the basis of experiments it can be ascertained that the Universe has an overall density that is very close to the critical value between re collapse and eternal expansion.
Hopefully, future astronomical observations and experiments will make new breakthroughs to solve the mysteries associated with the Universe. The innate human inquisitiveness and tireless pursuit of knowledge will certainly bring about revolutionary changes about our ideas of the Universe.
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