Speculation as to why an hour is so long for a child, and so short for a grownup.
Let’s suppose that every time your age doubles, you live one “lifetime” which feels just as long as all the previous ones. This would mean, for example, that the years between ages 10 and 20 feel just as long as the years between ages 20 and 40. It makes sense to me — a 20-yeard-old probably feels as different from his 10-year-old self as a 40-year-old does looking back to age 20.
...And in the end it makes me wonder about parenting. A lot of people talk as if the goal of parenting is to produce a healthy and productive adult. Surely this is important: adulthood sure seems long and important. But I can’t help but wonder whether it’s more important to give your offspring a happy childhood than to prepare them for a happy adulthood. After all, by age 18 you’ve already lived about five and a half of your eight lifetimes!