NEW YORK — Every second we’re alive, we’re moving through time. How people perceive the “flow of time” is from the past to the present to the future, moving in one direction like an arrow. Scientists from the CUNY Graduate Center Initiative for the Theoretical Sciences say this phenomenon arises from microscopic interactions among particles and cells, but how this actually takes place is still unclear. Now, a new study is helping to unravel this mystery and explain our perception of time.
Researchers note that the “arrow of time” is a concept from the second law of thermodynamics. The principle states that microscopic arrangements of physical systems move from order to disorder, increasing in randomness over time.
As the disorder increases, it becomes more and more difficult for the system to return to an ordered state — making the arrow of time even stronger. Simply put, the universe’s natural tendency to move towards a chaotic state is the fundamental reason humans perceive time to be flowing in one constant direction.
“The two questions our team had were, if we looked at a particular system, would we be able to quantify the strength of its arrow of time, and would we be able to sort out how it emerges from the micro scale, where cells and neurons interact, to the whole system?” explains first author Christopher Lynn, a postdoctoral fellow with the ITS program, in a media release. “Our findings provide the first step toward understanding how the arrow of time that we experience in daily life emerges from these more microscopic details.”
Neurons in your eye help explain our perception of time
The researchers studied time’s arrow by observing specific parts of a single system and the microscopic interactions taking place within it. Specifically, the team examined the neurons that function within the retina of an eye. While deconstructing a single moment in time, the study authors found that they could break down the arrow of time into different pieces — those produced by parts working individually, in pairs, in triplets, or in more complex configurations.
After breaking down the arrow, researchers analyzed existing experiments on how neurons in a salamander’s retina respond to different videos. In one video, a single object moved in random directions across the screen. In the other, the salamander watched a complex nature scene.
While viewing both movies, the study found that the arrow of time emerged from the simple interactions between pairs of neurons — not larger and more complicated groups. Interestingly, the retina displayed a stronger arrow of time while watching the more complex nature scene, instead of just a single object moving around.
Lynn believes this raises questions about how our internal perception of time aligns with the real world.
“These results may be of particular interest to neuroscience researchers,” Lynn concludes. “They could, for example, lead to answers about whether the arrow of time functions differently in brains that are neuroatypical.”
The findings are published in the journal Physical Review Letters.