A self-respecting universe couldn’t have a hope of ever producing a bacterium if it hadn’t opened up to a scale of at least half a micrometer. And, in truth, for anything like a microorganism to exist, the casually connected universe had to become much, much larger. Sizeable enough for its innards to begin to feel their mutual gravitational attractions across a mammoth range of distances, from 109 meters to at least 1021 meters. Enough for it to have a chance of brewing the stars and elements — ingredients that would, in turn, feed their novelty back to a microscopic scale, unleashing a blizzard of chemistry and complexification that would eventually build something akin to a single-celled living thing.

In other words, the real question is: How big a universe is needed to allow you to be sitting here reading these words?

Actually, 63 orders of magnitude might be a little more than is absolutely necessary. After all, the cosmos has been churning out stars and planets since well before our solar system came along, back to a time when we might drop a couple powers of ten in the scale of the cosmic horizon. But we don’t yet know whether anything quite like us has happened before, so the only thing we can say with certainty is that — in our very specific case — 63 is, and will always be, the magic number.