For writers, there is no more bleak and dismal an emptiness than silence -- unsolicited, unnatural silence that "thwarts what struggles to come into being," as Tillie Olsen wrote in 1965, "but cannot".
The writer-dreaded silence is not the fundamentally necessary grief-silence or healing-silence, or learning-silence -- not Keats' agonie ennuyeuse. It's a miserable, uninvited guest in our brains; a Dante's hellion whose visits achieve nothing, produce nothing and leave nothing behind. During those silent times writers languish in mute despair as the "writing dies over and over again" inside of us and the pages of our history turn, blank after blank.
So when you see a writer writing furiously through the day or well into the night, don't disturb her. Let her enjoy a moment of your silence -- and be glad that she's not suffering through her own.