Cosmic Microwave Background Radiation. For basics wiki link can be looked into. The points for discussions are, 1. How come it is same from all the directions? Ideally if some light is arriving from a given source, then it is expected to arrive as a wavefront covering maximum the hemisphere only. The text answers that BB was everywhere, in every direction. Is it not the dilution of a theory? Moreover universe at that time (recombination era) was very young, and new spacetime much much larger than that got added afterwards. So where is the question of BB happening everywhere. 2. Is it ok to expect that there may be an object in universe where CMBR is only arriving in some portion of it (say half)? 3. What is the most saner alternative explanation for CMBR? If at all.