1) What start the Half hour – Jesus off the Mercy and the coming of the Angel of Rev. Ch 10
2) The silent is because —– no Revelation from the Throne ,—- Jesus is off the Mercy Seat
3) Ends when the Angel of Rev 8:3 offers “ALL” the prayers (The Beast and  24 elders with golden vials full of odours, which are the prayers of saints, Rev 5:8 “plus” the Bride on Earth) during the Half hour silence.