• March 24, 2014 at 8:26 pm

    The Big Bang theory depends on two major assumptions: the universality of physical laws and the cosmological principle. The cosmological principle states that on large scales the Universe is homogeneous and isotropic.

    <span style=”line-height: 1.5em;”>These ideas were initially taken as postulates, but today there are efforts to test each of them. For example, the first assumption has been tested by observations showing that largest possible deviation of the fine structure constant over much of the age of the Universe is of order 10−5.[35] Also, general relativity has passed stringent tests on the scale of the Solar System and binary stars.[notes 2]</span>

    If the large-scale Universe appears isotropic as viewed from Earth, the cosmological principle can be derived from the simpler Copernican principle, which states that there is no preferred (or special) observer or vantage point. To this end, the cosmological principle has been confirmed to a level of 10−5 via observations of the CMB.[notes 3][citation needed] The Universe has been measured to be homogeneous on the largest scales at the 10% level.[36]