Within trillionths of a second after the Big Bang, they have reasoned, the primordial explosion - many billions of degrees hot - must have created a universe that contained equal quantities of matter and antimatter.
The Big bang happened prior to the primordial explosion. 
( z1 bang :mod ( z2 big ) :time ( z3 prior :op ( z4 explode :mod ( z5 primordial ) ) ) )