"Observing a 'moment of silence' in American public life is typically a way of accommodating prayer, or of filling the void left by its absence. Our busy society demonstrates its respect by ceasing activity and noise and holding still. Silence is our response when words fail us."
We see these kinds of moments take place on 9/11 every year at the times two towers fell and sometimes we see these pauses at sporting events or at public celebrations on national holidays.
In the same article entitled "Be Still," the editors point us to the Synod of Bishops on the Bible that met in Rome in October. The bishops task was to focus on how God's word should be received in the context of liturgy. The Synod resulted in 55 propositions to the bishop of Rome including "a call for wider 'use of silence' during the liturgy" particularly after the Word is preached.
They go on to say that "this silence... is an important part of the process of receiving, absorbing, and responding to God’s word." And the editorial is careful to remind us that this silence not simply be for the sake of one's own mind; it is to give us time to reflect on how to turn what we have heard into action, to bear fruit. They suggest that our liturgical moment of silence should be modeled on the stunned questioning of the Jews of the diaspora at Pentecost who simply said, "What should we do?"
This is probably where the silence of a church liturgy differs from the silence of an American liturgy. Typically, the moment of silence observed in public life is an external token of appreciation or respect for a deceased person, perhaps including a momentary reflection on one's own mortality. For the church, however, the moment of silence is an internal reckoning with the living Christ.