The flow of time from the past to the future is a central feature of how we
experience the world. But precisely how this phenomenon, known as the arrow
of time, arises from the microscopic interactions among particles and cells
is a mystery—one that researchers at the CUNY Graduate Center Initiative for
the Theoretical Sciences (ITS) are helping to unravel with the publication
of a new paper in the journal Physical Review Letters. The findings could
have important implications in a variety of disciplines, including physics,
neuroscience, and biology.
Fundamentally, the arrow of time arises from the second law of
thermodynamics: 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 tendency 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, the paper's
first author and a postdoctoral fellow with the ITS program. "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 researchers explored how the arrow
of time could be decomposed by observing specific parts of a system and the
interactions between them. The parts, for example, 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 way of decomposing the arrow of time, the researchers
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, researchers found that the arrow of
time emerged from the simple interactions between pairs of neurons—not
large, complicated groups. Surprisingly, the team 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, a professor of Physics and Biology at the Graduate Center and the
study's principal investigator.
Reference:
Decomposing the local arrow of time in interacting systems, Physical Review
Letters (2022).
journals.aps.org/prl/accepted/ … 6a8ee4316350b055c80c , On Arxiv:
arxiv.org/abs/2112.14721v1
Tags:
Physics