The first is the moment of silence after the demonic Serpent spoke to Eve about the forbidden fruit but before her decision to eat it (Gn 3:4-6). Eve’s decision would affect every human being who would ever exist. Eve could have said no to the devil, refused to disobey and distrust God, and humanity would not have fallen—but she did not, and the Fall took place.
The second is the moment of silence after the angel Gabriel told Mary her child would be conceived by the Holy Spirit but before her consent (Lk 1:35-38). This is also a moment when a decision was being made which would affect every person who would ever exist. Mary could have said no to the Angel and the Incarnation would not have taken place—but she said yes and so the Redemption could occur.