Physicists Are Unraveling the Mystery of the Arrow of Time

Time Mystery Fire

Scientists are unraveling the mystery of the arrow of time with important implications for physics, neuroscience, and biology. 

A new study by theoretical physicists has made progress toward identifying how particles and cells give rise to large-scale dynamics that we experience as the passage of time.

A central feature of how we experience the world is the flow of time from the past to the future. But it is a mystery precisely how this phenomenon, known as the arrow of time, arises from the microscopic interactions among particles and cells. Researchers at the CUNY Graduate Center Initiative for the Theoretical Sciences (ITS) are helping to unravel this enigma with the publication of a new paper in the journal Physical Review Letters. The findings could have important implications in a wide range of disciplines, including physics, neuroscience, and biology. 

Fundamentally, the arrow of time emerges from the second law of thermodynamics. This is the principle that microscopic arrangements of physical systems tend to increase in randomness, moving from order to disorder. The more disordered a system becomes, the more difficult it is for it to find its way back to an ordered state, and the stronger the arrow of time. In short, the universe’s propensity toward disorder is the fundamental reason why we experience time flowing in one 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?” said Christopher Lynn,  a postdoctoral fellow with the ITS program and the paper’s first author. “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.”

To begin answering these questions, the physicists explored how the arrow of time could be decomposed by observing specific parts of a system and the interactions between them. For example, the parts could be the neurons that function within a retina. Looking at a single moment, they showed that the arrow of time can be broken down into different pieces: those produced by parts working individually, in pairs, in triplets, or in more complicated configurations.

Armed with this method of decomposing the arrow of time, the scientists analyzed existing experiments on the response of neurons in a salamander retina to different movies. In one movie a single object moved randomly across the screen while another portrayed the full complexity of scenes found in nature. Across both movies, the team discovered that the arrow of time emerged from the simple interactions between pairs of neurons—not large, complicated groups. Surprisingly, the researchers also observed that the retina showed a stronger arrow of time when watching random motion than a natural scene. Lynn said this latter finding raises questions about how our internal perception of the arrow of time becomes aligned with the external world.

“These results may be of particular interest to neuroscience researchers,” said Lynn. “They could, for example, lead to answers about whether the arrow of time functions differently in brains that are neuroatypical.”

“Chris’ decomposition of local irreversibility—also known as the arrow of time—is an elegant, general framework that may provide a novel perspective for exploring many high-dimensional, nonequilibrium systems,” said David Schwab, the study’s principal investigator and a professor of Physics and Biology at the Graduate Center.

Reference: “Decomposing the local arrow of time in interacting systems” by Christopher W. Lynn, Caroline M. Holmes, William Bialek and David J. Schwab, Accepted, Physical Review Letters.

Authors in order: Christopher W. Lynn, Ph.D, postdoctoral fellow, CUNY Graduate Center; Caroline M. Holmes, Ph.D student, Princeton; William Bialek, Ph.D, Physics professor, CUNY Graduate Center; and David J. Schwab, Ph.D., Physics and Biology professor, CUNY Graduate Center

Funding sources: National Science Foundation,  National Institutes of Health, James S McDonnell Foundation, Simons Foundation, and Alfred P Sloan Foundation.

11 Comments on "Physicists Are Unraveling the Mystery of the Arrow of Time"

  1. … “Fundamentally, the arrow of time emerges from the second law of thermodynamics”…
    What, Who, When, HOw…..

  2. Neuro scientists better leave time to physicists,by this article I found out that they don’t know anything about time and they just coming up with sth totally different and crazy to even think of…

  3. This research needs to be reviewed by a writer who can tell whether the research is hokum or not.

  4. @xABBAAA thank you. I wonder how long it will take them to figure there is no time only entropy

  5. Well, Groucho Marx said “Time flies like an arrow. Fruit flies like a banana”

  6. As the profound old saying goes:. Time flies like an arrow. Fruit flies like a banana.

  7. Oh that’s what it was, a “local irreversibility”… So if they move to the next good they might become Benjamin Buttons… Sure. Makes sense. Lol

  8. Sir E. Danforth Reklaw, MD, PhD, FRCS | August 26, 2022 at 2:18 pm | Reply

    The recently published book, “Out of Time” by Sam Baron, Kristie Miller, and Jonathan Tallant – 2022 published by OUP (Oxford University Press), shows that time in the folk sense may not be an actual aspect of one’s reality giving rise to Agency, but rather may be a manifestation of “causation” as a metaphysical property, like colour, from which we construct the concept of agency. Deconstructing time, in the folk sense, does not have to mean the end of agency, because agency can be reconstructed by causation and our perception of the arrow of time remains intact. In cultures whose languages are read/written from right-to-left, the “arrow” of time is in part perceived with a right-to-left conceptualisation of its flow and directionality. This really must make us think about time, the arrow of time, and all of its ascribed properties to be a sensory perception, created in the brain as a manifestation of fitness for survival and reproduction, rather than something more “realistically perceived”. Agency, and everything about it, can be just as robust and amazing when built upon causation as it is when built from time in the folk sense.

  9. Time is not the product of the 2nd law of thermodynamics, is is a consequence of change or more accurately “motion”. If nothing changes (all things had zero motion) time would be meaningless and cease to manifest.

    Like does this author recognize there are bubbles of emergent complexity where order is increasing such as here on Earth– so does time not exist here??? Goodness.

  10. If what they say is true, while things are coming into being, and random particles are now behaving as organized biological systems, time would flow backwards which is not the case. Anabolism is not anti time, and catabolism is not by itself time but just one thing that happens during the passage of univector time.

  11. As a Physicist, based upon this “arrow of time” article and human mind extrapolation. There is circular “reasoning” which in and of itself is an excersize in futility. From the first atom and “how” it stays together to the 2nd law of thermodynamics where disorder moves on to further disorder to “dark matter” unseen yet measured Be nice and enjoy the wonder and beauty before you take the path to dark matter.

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