There's also a degree of physical deterioration as we age that might also affect our judgement of time, according to Adrian Bejan, a professor of mechanical engineering at Duke University in Durham, North Carolina. He has tried to explain the puzzle of our perception of time through the lens of a theory he developed in 1996 on the "physics of life" that has become known as "constructal law".

"The biggest source of input to our brain is through vision, from the retina to the brain," says Bejan. "Through the optical nerve the brain receives snapshots, like the frames of a movie. The brain develops in infancy and is used to receiving lots of these screenshots. In adulthood the body is much bigger. The travel distance between the retina and the brain has doubled in size, the pathways of transmission have become more complex with more branches. And in addition with age, we experience degradation."

This, he says, means the rate at which we receive "mental images" from the stimuli of our sensory organs decreases with age. This creates the sensation of compressed time in our minds as we are receiving few mental images in one unit of clock time as adults compared with when we are children.