As we humans grow older and wiser, it's not unusual to feel as if time were
whizzing by, quietly gathering speed with every year.
Mechanical engineer Adrian Bejan from Duke University now thinks he has
figured out why, and just like ageing, he suspects the experience is both
universal and inescapable.
Adhering to the physical laws of life and evolution, Bejan argues that as our
eyes fatigue and our brains grow slower, it is only natural to feel as though we
are losing time.
"People are often amazed at how much they remember from days that seemed to
last forever in their youth," he said.
"It's not that their experiences were much deeper or more meaningful, it's
just that they were being processed in rapid fire."
Anyone who has ever watched water come to boil knows intuitively that their
"sense of time" is only a perception. Far from being a reliable measurement,
it's more like a mental construct, constantly changing over time.
This essentially means that the seconds, minutes, and hours we keep in our
heads are inherently different to the ones we count on our clocks.
"The time that you perceive is not the same as the time perceived by
another," writes Bejan.
"Why? Because the young mind receives more images during one day than the
same mind in old age."
Put simply, an older brain takes longer to process the present. Just look at
any baby and you'll notice that their eyes dart about much faster than your own,
taking in the scene at a rapid pace.
"Said another way, if the lifespan is measured in terms of the number of
images perceived during life, then the frequency of mental images at young age
is greater than in old age," writes Bejan.