Among scientists (specially physicists), there has been a discussion for a long time about how much of a science is cosmology. The difficulty earlier (before 1920s) was the absence of any observations and the stronghold of mythology. Even broad observed features were highly ambiguous. Only in the twentieth century was it realized that what were thought of as nebulae were really distant galaxies. In 1927, Hubble observed faraway galaxies and their velocities and formulated Hubble's law which says, 'The farther a galaxy is, the faster it is running away from us'. This gave rise to the model of the expanding universe now known as the 'Big Bang'. Almost forty years later, in 1965, the cosmic microwave background radiation (CMBR) was discovered accidentally. The non-uniformity or anisotropy of CMBR was discovered only in 1992. It is only in the last two
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