As we get older, it becomes obvious that life really does feel like it goes by in the blink of an eye. While languid childhood summers felt long and eventful enough to be their own Netflix series, scenes from adulthood may seem more like improv shows you felt obligated to attend. You liked it, but what really happened — and is it over already?
Numerous researchers have attempted to explain why this perplexing feeling persists. In a paper published Monday in European Review, Duke University professor Adrian Bejan, Ph.D. attempts to explain the perception of rapidly passing time with his knowledge of physics.
Bejan is an award-winning mechanical engineer known for conceiving a theory in physics called “constructal theory.” This theory is a way of accounting for all things in nature — life, evolution, design, and performance — in the context of the spontaneous creation made possible by the flow of time. In his new study, Bejan examines time as we experience it through the lens of this theory, using previously published research from other experts to back him up.
“Days become shorter, and so do the years — we all have stories of this kind from the long days of childhood to the days, months, and years that now pass in a blur,” Bejan tells Inverse. “I asked myself, what is the physical basis for the impression that some days are slower than others? Why do we tend to focus on the unusual, not on the ever-present?”
To answer these questions, he examined the building blocks of our experience of time. He reasons that time is represented by changes in stimuli, like visual images, and that our minds perceive reality by processing these images, one after the other. Scientists have established that we take in the world as a seamless stream of ongoing perceptions. And we sense that time changes when the images we perceive change too. He writes: “the time arrow in physics is the goal-oriented sequence of changes in flow configuration, the direction dictated by the constructal law.”
According to this framework, time seems to move quickly because our perception of “clock time” that rules our days (actual minutes, hours, days, and years) is misaligned with “mental-image time” — our ever-increasing number of visual observations.
This misalignment, Bejan argues, is strengthened as we age because we experience a slowdown in image processing speeds. For physical reasons, older people process fewer images in the same amount of time than younger people, so time appears to pass more quickly.
“The rate at which changes in mental images are perceived decreases with age because of several physical features that change with age — saccades frequency, body size, pathways degradation,” Bejan explains.
Saccades are the rapid eye movements that happen between moments of “fixation” — that is, moments of focus in the same direction. It’s like rapidly moving your camera around in between shots of the same scene. Our eyes do this because in the time between successive saccades, we try to take in all of the other things going on in the world to absorb more information. But fatigue and age interfere with saccades, making it difficult to transfer information.
In short, youthful days seem longer because the young mind receives more images during the day compared to an older brain. Bejan points out that, in adulthood, the moments that seem most like “slower” youthful days are those that are full of productivity and events. Those are the days where we attain more memories that stick.
“Productive days happen when the body and mind are rested, after periods of regular sleep; when in the morning you look in the mirror and you see a younger you, not a tired you,” Bejan says.
In the future, it’s possible that younger people will start to experience this rapid passing of time sooner. Studies show that social media causes people to experience time distortion — time spent on Facebook, for example, seems demonstrably longer than the amount of time that’s actually spent on Facebook.
To understanding the passage of time, we have to understand how humans perceive the passing of time. If we’re mindful of it, maybe things will seem less like a blur.
Why does it feel that the time passes faster as we get older? What is the physical basis for the impression that some days are slower than others? Why do we tend to focus on the unusual (the surprise), not on the ever present? This article unveils the physics basis for these common observations. The reason is that the measurable ‘clock time’ is not the same as the time perceived by the human mind. The ‘mind time’ is a sequence of images, i.e. reflections of nature that are fed by stimuli from sensory organs. The rate at which changes in mental images are perceived decreases with age, because of several physical features that change with age: saccades frequency, body size, pathways degradation, etc. The misalignment between mental-image time and clock time serves to unite the voluminous observations of this phenomenon in the literature with the constructal law of evolution of flow architecture, as physics.