This intangible boundary between the knowable and the unknowable is, at present, roughly a thousand, trillion, trillion meters across — should you possess the means to measure it.
At the other end, in the deepest innards of every single speck of cosmos, is a scale of a hundred billion, trillion, trillionths of a meter. It represents the last meaningful physical scale within our present understanding of physics, a place where space-time itself gets choppy, uncertain, and decidedly problematic.
David C's Blog 