Time seems to flow inexorably in one direction, from past to future, a process we witness in everyday events like a broken glass that never reassembles itself. However, recent discoveries by physicists at the Technical University of Darmstadt challenge this perception by revealing a surprising phenomenon. Under certain conditions, the motion of molecules in materials like glass and plastic can be reversed in time.
The research, led by Till Böhmer and Professor Thomas Blochowicz from the Institute for Condensed Matter Physics, has been published in the prestigious journal Nature Physics. This study effectively measures what the scientists refer to as “material time,” an internal clock that ticks independently from conventional timekeeping.
This breakthrough was achieved by utilizing ultra-sensitive video cameras to record the minute fluctuations of molecules within the materials. By shining a laser on a glass sample, the scattered light formed a random pattern of bright and dark spots, reflecting the molecular movements over time. Using statistical analysis, the researchers calculated how the pattern changed and determined the pace at which the material’s internal clock ticks.
Remarkably, these molecular fluctuations proved to be time-reversible when viewed in terms of material time. This means that if the internal clock of the material were to run backward, the movements of the molecules would appear unchanged, akin to watching a pendulum’s motion played in reverse.
However, this discovery does not imply that the aging of materials can be reversed. Rather, it confirms the validity of the material time concept, which captures the irreversible part of material aging. The concept of material time was proposed around 50 years ago, but this is the first time it has been measured. While this internal clock represents the passage of time for the material itself, not all movements within the material contribute to its aging.
To illustrate, the researchers use a metaphor: like children playing in the back seat of a moving car who do not affect the car’s motion, some molecular movements do not impact the aging process. Only the movements relative to the material time contribute to aging.
The implications of this discovery extend beyond glass and plastic. The researchers tested their hypothesis on various disordered materials and even conducted computer simulations, all of which produced consistent results. This suggests that the principles observed may apply more broadly across different types of materials.
While this study provides profound insights into the molecular dynamics and aging of materials, it also raises numerous questions for future research. For instance, how is the reversibility of material time related to the general reversibility of physical laws? How do different materials exhibit different internal clocks? These are questions the Darmstadt team is eager to explore further.
The scientific community is excitedly anticipating further revelations that could reshape our understanding of material science, the aging process, and even the fundamental nature of time itself.