We think of childhood as a time of stability, and adulthood as changing and uncertain. But whenever I visit my niece and nephew, this attitude is revealed as false nostalgia. Every visit, my niece and nephew walk differently, pronounce \"R\"s differently, attend a new school, are taller, play with different toys, have new wardrobes, converse with me at a higher level of consciousness. I must enjoy any likable phrasing or mannerism quickly, since next visit my niece and nephew will be new versions. What do adults know of mutability? Occasionally we switch gyms or jobs or towns, but children change their whole costume of body and mind on a regular schedule, cycling through identities faster than birthdays. Our unit of aging is the decade, theirs is the month. Humans age faster, the younger they are.