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 primordial explosion happened after the Big Bang. 
( z1 explode :mod ( z2 primordial ) :time ( z3 after :op ( z4 event :name ( z5 name :op "Big" :op "Bang" ) ) ) )