Is how fast time goes by a function of how old you are?

This interactive visualization by designer Maximilian Kiener makes that argument. It shows that the longer you live, the relative significance of any particular year of your life goes down.

So, for instance, for a 2-year-old, a single year is a full half of their young life. Every moment is a bigger part of the whole.

By 30, that's changed a lot. For an average 30-year-old, a single year is just 3.33 percent of their life.

By the time you're 60, the years have shrunk even more, to just 1.67 percent of your life.

So is there any reason to believe the scroll wheel is an apt metaphor for how we live?

Kiener says his idea for the visualization came courtesy of philosopher Paul Janet (1823–1899), who was cited in an 1886 article by William James in the Journal of Speculative Philosophy. In that article, Janet is quoted as writing:

Whoever counts many lustra in his memory need only question himself to find that the last of these, the past five years, have sped much more quickly than the preceding periods of equal amount. Let any one remember his last eight or ten school years: it is the space of a century. Compare with them the last eight or ten years of life: it is the space of an hour.

A formula similar to the one in the visualization follows.

So is the diminishing significance of each year the reason those summers in our 30s pass so much more quickly than the ones when we were 8? That's too hard to conclude — in the same article, James proposes that it's the monotony of routine, not the buildup of time, that makes time pass more quickly as we age. In other words, we've seen it all before. There's less novelty to distinguish one moment from the next.

Whatever the reason, the visualization shows one less arguable truth: Time often turns out to be simple math. And all those hours add up.

Thanks to Maria Popova's Explore for noting this slightly depressing visualization.