The term 'Cause of a Big Bang' can be summarized by two crossword solutions: SLAM (4 letters) and TNT (3 letters). SLAM stands for 'Symmetry-breaking, Lopsided, Amplification of Fluctuations', which is a theory that suggests that the universe began with a small fluctuation in the density of matter that was amplified by gravity. TNT stands for 'Theory of Nothing', which is a theory that suggests that the universe began from nothing, and that the Big Bang was caused by a quantum fluctuation.