I’m definitely not talking here about the actual length of your life as measured in “clock time”. I’m talking about the subjective time you spend on earth.

When I was young and school was out for the summer my mother used to take my brother and me to many places we loved (even though she didn’t like to drive). One of our favorites was the local zoo. I was entranced, and could spend hours watching the several enormous elephants, the many chattering monkeys, or one of the sleek tigers tearing a...