Why does time fly as you get older?

"An impression, already, that things are getting narrower. Don't puzzle too much. Don't turn around. Don't stop. Don't force the pace. For no visible reason, no reason. Speed has become necessity." -- Alain Robbe-Grillet, "Recollections of the Golden T

Remember what summer was like when you were a kid? The season seemed to span an eternity and Christmas might as well have been a million years in the future. But then you grew older. Summers passed in quick succession, Christmases and birthdays swept by like pages in a flip book. Everything seems to be speeding towards an unavoidable conclusion.

I used to think all of this was because our solar system is being swept steadily towards a black hole, but it turns out there are other theories out there. RadioLab's Robert Krulwich explores one theory in this NPR article from earlier in the week. The premise is that it all comes down to novelty. The brain expends more energy recording new experiences and sensations. This is why you so vividly remember that first kiss but not so much the 136th* and why your first day at a new job seems to last forever.

Then there's also the proportional argument. When you're 10 years old, a year is 10 percent of your life. At age 50, however, that same amount of time accounts for only 2 percent of your life. A single year is worth less in proportion to the rest of your lifespan.

My wife and I were discussing the NPR article and we got to wondering about another related possibility: perhaps it has to do with grasping. When we're younger, we live more in the moment, at one with all those new experiences sparking all around us. But as we get older, we have more past to obsess about and, in most cases, increasingly project our mind into the future with worry and longing. What will we own? What will we be? How will other people see us? The present may be the only moment that's real, but we can hardly perceive it anymore. We become a ghost strung between a dead past and an imagined future. If any Eckhart Tolle fans are reading that, add your own German accent for maximum effect.

There's still a part of me that clings to the black hole theory, but I like to take a little from both the Krulwich and the Tolle columns. Try to experience the present moment as best you can and never stop introducing yourself to new and wonderful things.

However, it wouldn't hurt to study up on black holes.

* If you haven't had your 136th kiss yet, here's a spoiler: it takes place up against the side of a GM Daewoo.

About the Author: Robert Lamb spent his childhood reading books and staring into the woods — first in Newfoundland, Canada and then in rural Tennessee. There was also a long stretch in which he was terrified of alien abduction. He earned a degree in creative writing. He taught high school and then attended journalism school. He wrote for the smallest of small-town newspapers before finally becoming a full-time science writer and podcaster. He’s currently a senior writer at HowStuffWorks and has co-hosted the science podcast Stuff to Blow Your Mind since its inception in 2010. In his spare time, he enjoys traveling with his wife Bonnie, discussing dinosaurs with his son Bastian and crafting the occasional work of fiction.