  During the last century many observations have been made to peep into the
dark matter in the universe and many astonishing behaviors of Galaxy clusters
have been found which do not fit to any theories formulated before. However,
Optical Spectroscopic observation has been initially used to measure the
rotational velocity of the Andromeda Galaxy as a function of distance found in
contrast to the Law of Gravitation.Due to the expansion of space,
electromagnetic radiation emitted in the distant Universe is redshifted on its
path towards us which can be used to determine the distances of astronomical
objects.
