Chinese Scientists Propose Quantum Explanation for Arrow of Time

According to the researchers, time in everyday experience consistently flows in a single direction—from the past toward the future—a phenomenon commonly referred to as the arrow of time. However, when physicists examine the fundamental equations governing classical mechanics, electromagnetism, and quantum theory, they find that these laws are largely time-symmetric, functioning equally well when time is mathematically reversed.

This raises a fundamental question: if the laws of physics do not favor a particular direction of time, why is human experience of time strictly one-way?

Traditionally, this question has been addressed through thermodynamics. In the 19th century, physicist Ludwig Boltzmann linked the arrow of time to entropy, often described as a measure of disorder.

According to the second law of thermodynamics, entropy in an isolated system tends to increase over time, explaining everyday irreversible processes such as ice melting, gases expanding, and complex systems breaking down rather than spontaneously organizing themselves. While this framework accounts for macroscopic irreversibility, it does not fully explain why the perception of time itself appears inherently directional.

The new proposal shifts the focus to the quantum level, where particles and systems interact in highly interconnected ways. In a study conducted by a team at Hainan University in China, researchers argue that the direction of time may emerge naturally from the internal evolution of quantum systems.

At this scale, systems do not exist in isolation but continuously interact, exchange information, and become increasingly entangled.

As these quantum correlations deepen, reversing the system’s evolution becomes progressively more difficult—even if such reversal remains theoretically allowed by the underlying equations. From this perspective, irreversibility is not imposed externally but arises from the system’s internal structure and dynamics.

The researchers suggest that as quantum components interact, information about their previous states becomes effectively inaccessible, creating a natural distinction between “before” and “after.” This gradual loss of retrievable information gives rise to the observable direction of time.

Importantly, the team emphasizes that their approach does not contradict thermodynamics or Einstein’s theories of relativity. Entropy remains central at macroscopic scales, while relativity continues to accurately describe the behavior of time at high velocities and in strong gravitational fields. Instead, the new framework complements these theories by addressing how temporal directionality emerges at the microscopic level.

By explaining the arrow of time as a consequence of quantum interactions rather than measurement, observation, or finely tuned initial conditions alone, the proposed theory offers a deeper understanding of how time’s direction arises—helping to bridge the gap between fundamental physical laws and everyday experience.