Time seems to run much faster when you’re older – and now a scientist has explained why.

We all remember those feelings as kids that the days would last forever. Particularly when sitting through boring classes at school – or even enjoying endless, lazy days on the beach. As we age, however, time apparently starts to rush by, and years suddenly feel about as long as some months. So why is it that time seems to go faster as we get older?

Well, one man who thinks that he has the answer to this question is Professor Adrian Bejan. He is Duke University’s J. A. Jones Distinguished Professor of Mechanical Engineering and specializes in thermodynamics, building what he has dubbed “constructal law.” This is a theory about how networks form in nature.

Bejan has actually had quite a varied career, too. A native of Romania, the professor showed enough artistic ability as a child that his mom and dad initially sent him to art school. And on top of that, Bejan is a talented basketball player who even got picked to represent the national team. But it seems that science is his greatest love, as he moved to the U.S. at 19 years of age to study on a scholarship.

Bejan’s eminence in engineering is striking too. For instance, the professor now has 650 peer-reviewed articles to his name – as well as no fewer than 30 books. And this prolific output goes alongside his 18 honorary doctorates. So when Bejan claimed in a March 2019 journal article to have the answer to time’s speeding up as we age, it seemed only right that we should listen.

The first question to answer is, though, what is time? Well, scientists have been thinking about this since the 1500s, when Galileo Galilei tackled the subject. To begin with, then, time was seen as something that could be measured using definite numbers. In classical physics, in fact, it was believed that the concept of time didn’t change from person to person.

In the early part of the 20th century, however, German genius Albert Einstein turned that understanding on its head. So he theorized that time is actually mixed in with space – in what he called “space-time.” And after this revelation, the idea of time existing separate from space as an absolute was no longer part of science.

Just one incredible outcome of this new thinking is the “twin paradox.” So it’s believed that if you took identical twins and sent one off to space in a very fast rocket, when that twin got back to Earth, they’d find that their sibling is much older. And to understand this so-called paradox, you need to apply Einstein’s theory of special relativity.

Naturally, then, the concept of special relativity plays a big part in why some days seem longer than others. On one occasion, for example, we could get a lot done in a single day and appear to have plenty of time in which to do it. And what’s more, we might even remember things better during these busy days than we do on the ones without much going on.

So Bejan’s article – “Why the Days Seem Shorter as We Get Older,” published in Eurepean Review – actually suggests a reason why this could be the case. According to the professor, then, it appears that we just get more done when we’re well rested. This is also why athletes rest before gameday, Bejan argues. It’ll give them more time to make that catch or score that touchdown, you see. And it could even be why youngsters feel that they have more time for exams if they have good sleeps the nights before.

Bejan also points out that understanding that rest affects perception of time’s passing is important for another reason. That’s because, he says, kids who stay up late using social media face a misrepresentation of time that can have bad outcomes. These can include mental illness and problems with their moods on top of tiredness from lack of sleep.

Bejan goes on to describe his theories in more depth in the article too. Reassuringly, then, Bejan details how, despite our perceptions of time differing, there is still absolute time in a sense. And in his paper, the professor calls this “clock time,” as it’s what clocks and watches measure. So no matter what you use to mark them off, there are always 24 hours in a day.

Yet clock time still doesn’t feel the same to each person. Bejan therefore calls the time each of us senses “mind time.” So while a clock might show an hour passing, different people will perceive that period differently. But is there a way to explain this apparent discrepancy? Well, the professor points out that, to find an answer, we need to first ask what time means to us.

For his part, Bejan believes that time is measured by changes in the things that we observe. So, he argues, we perceive reality by way of images that direct information to our brains. And as a result, we estimate alterations in time by how much these images differ. We therefore understand that time has passed because what we’re looking at has altered – not because the clock shows an hour has gone by.

Previously, experts believed these changes in time appeared to us as a smooth flow. But now scientists are challenging this idea. Bejan, for example, thinks that experiments show that we process what we see in chunks. In his opinion, then, this method resembles engineering’s “sample and hold” process. So, in other words, we hold onto images just long enough to be able to analyze them.

In June 2016 Michael H. Herzog, Thomas Kammer and Frank Scharnowski published a paper concerning this area of thought. In it, the scientists explained that our perception works a bit like the movies. Films seem to portray a smooth motion that doesn’t have breaks, after all. Yet we know that movies consist of thousands of individual frames. So, in regards to perception, perhaps the brain joins up the “frames” that we see in the same way.

We can actually find those “frames” if we examine how we create our pictures of the world too. Of course, we only see anything at all because our eyes are sensitive to the light that objects around us reflect. And our brains then interpret the signals that our eyes send and turn them into images.

But we don’t actually look at the world with a fixed gaze. In fact, our eyes dart from one part of a scene we’re looking at to another. These movements are called saccades, and, amazing as it sounds, we are nearly always completely unaware that we’re even making them – even though they can be quite big.

Image: John M Lund Photography Inc/Getty Images

Our eyes make saccades partly because they allow light to fall onto a retina’s center, which is called the fovea. The fovea is only tiny, but it’s responsible for seeing in high resolution. It’s especially useful when you require sharp vision, such as when reading or behind the wheel of a car.

In fact, the fovea uses about 50 percent of the optic nerve’s fibers to signal to the brain. And by darting the eye around a scene, we can make sure that those fibers are kept busy. This represents an efficient use of resources because the high-resolution part of the retina can be kept small. Believe it or not, the same adaptation also exists in several other species.

In between saccades, though, our gaze “fixes.” This just means that our eyes stop briefly so that they can allow the image to sink in. They do not rest completely, however; further movements that are much smaller than saccades keep the neurons of the brain stimulated.

The fixation period, as it’s called, also introduces an interesting paradox. So while we need fixation to perceive detail, our vision would actually wane if our eyes stayed still. This is because our neurons respond weakly to steady stimuli and strongly to changes. Consequently, if things at the edge of our vision don’t move, they disappear – although we don’t normally notice this happening.

Nevertheless, our eyes fixate as many as five times each second. This means that those rest periods can be as short as 200 milliseconds. The saccades themselves are brief as well. Yet the eyes can actually revolve through the equivalent of 900 degrees in a single second.

Which is all to say that these fixations represent the “chunks” that we see the world in. But how do they contribute to the feeling that time passes differently with age? Well, Bejan believes that this sensation comes about because the young see a greater number of images each day than older people.

Bejan’s paper pointed out that, in fact, people see more images when they’re younger because youngsters’ eyes are constantly moving. This, in turn, allows for more fixations. In the article, Bejan wrote, “This is evidenced by how often the eyes of infants move compared to adults. Because infants process images faster than adults, their eyes move more often, acquiring and integrating more information.”

On top of this, our brains grow bigger and more complicated with age. This means that the signals from our eyes that our brains turn into perceptions have to go further to get to the processing areas. So even though nerves transfer electricity quickly, it’s the sheer size of the network that creates a problem as we age.

Yet not only are the paths that the signals travel more complex, but they also become degraded with age too. And to make matters worse, the brain finds it harder to work with information as it gets older. The rapid work of a younger brain means that it can understand new stimuli that much quicker before moving on to the next one.

The outcome of quicker signaling and more rapid processing is that changes can be recognized faster by the young. And, as we saw, our “mind time” is marked not by the ticking of a clock, but by how many images we perceive. So if we perceive different mental images less often, time seems to move more quickly for us.

In the article, Bejan summarized his explanation by saying, “The present is different from the past because the mental viewing has changed, not because somebody’s clock rings.” He continued, “Days seemed to last longer in our youth because the younger mind receives more images during one day than the same mind in old age.”

There appears to be some experimental proof to support Bejan’s theory too. In 1987, for instance, James A. Sharpe and David H. Zackon measured saccade speeds on a range of ages and found that older people’s eyes don’t move as fast in some conditions. The researchers also noted that the time taken for older subjects to begin a saccade was extended and their movements became less accurate.

And in 1990 J. Myerson and his team provided evidence that thought processes slow down with age. As we get older, they argued, people lose information while working out complex problems. And this has the result of making it harder to find solutions. However, Bejan advised caution interpreting these results, as previous life experience may also have a role to play in this area.

So is there anything you can do about the feeling of time rushing by? Well, scientists have found that we actually look at things that surprise us for a longer amount of time. Consequently, doing something completely and utterly new could create fresh mental images that make the days seem to pass more slowly.

It’s also possible that when we do something that we’ve never done before, we can make memories that have a lot more detail. And this tends to make our recall of the event that we’re remembering take longer, rather than the event itself taking a long time. Experiments have shown exactly this process happening in people falling into a net.

In fact, people often say that time moves more slowly when they have an accident. So perhaps this is an outcome of simply having so much new information to process. After performing experiments in the ’60s, too, psychologist Robert Ornstein found that subjects thought they took longer to hear tapes with lots of sounds on them than they did tapes with fewer noises.

Elswhere, though, researchers have found that practicing mindfulness might also affect perceptions of time. In 2013, for instance, Robin S. S. Kramer, Ulrich W. Weger and Dinkar Sharma published a paper that claimed that people who meditated found that a task seemed to take longer than those who didn’t.

Other explanations for time’s speeding up do exist, though. One is that our “biological clocks” might change. As we age, then, lots of the mechanisms in our bodies become slower. For instance, our heart beats less often, we take fewer breaths and our metabolism isn’t as fast. So younger people simply experience more of all of these things than older people do. It could seem to them, therefore, that they are experiencing more time.

Alternately, adults simply might not notice the finer details of our worlds because they’re so used to seeing them. Yet for kids, the world is jam-packed with things that are strange. So perhaps the extra mental work that they do to make sense of all the new stuff makes it feel as though the days are longer.

It could also simply be a matter of “clock time” as well. The younger you are, then, the bigger proportion of your life each period of time actually takes. For example: two years represents half the life of a four-year-old. Yet by the time you reach 50, that same timespan only makes up 4 percent of your life.

Finally, in 1996 a psychologist from Virginia by the name of Peter Mangan came to an altogether different conclusion. He asked a selection of young and old people to guess how long three minutes was by counting off seconds. And it turned out that the older folks took way longer than three minutes to do it – whereas the youngsters were almost spot on.

Mangan was shocked because the older people he had tested – some of whom were in their 70s – were still working. The psychologist told the New Scientist, “I could not believe that these people, who were very concerned with the time, could be consistently so far over in their estimate.”

Consequently, Mangan guessed that the internal clock in the brain – the “mind time” in Bejan’s theory – slows down in old age. He noted that less dopamine was produced in areas of the brain that influence the clock as you get older. So, he argued, the reason time seems to go faster is that we produce less of this particular chemical.