On December 25, a research team led by physicist Cai Qingyu at the University of Hainan (China) gave an explanation for why humans cannot go back to the past.
The research published in the prestigious scientific journal Annals of Physics argues that times shift the one-way direction of time is not due to external impact, but is naturally formed from the internal structure of the micro-world.
For more than a century, the question of why time is only moving forward has been a headache for physicists.
Since the late 19th century, physicist Ludwig Boltzmann has proposed the concept of entropy, saying that time passes because physical systems always tend to shift from a state of order to chaos. This argument helps explain many familiar phenomena in life, such as a broken cup cannot be repaired on its own or humans cannot be reborn.
However, the paradox arises when the fundamental equations of physics - from Newton's laws to Schrödinger's equations in quantum mechanics - all allow time to be reversed.
Mathematically, if x is equal to 0, these equations are still correct. That poses a major conflict between theory and reality, as the world around us clearly operates in only one direction of time.
To explain this contradiction, many previous theories pointed to the cause lying in the external environment. In that approach, already fragile quantum states are disrupted when interacting with the surrounding environment - a phenomenon known as quantum disconnection. Time therefore becomes irreversible.
However, the research team led by physicist Cai Qingyu at the University of Hainan (China) chose a different approach. Instead of looking at the external impact, they studied a completely closed quantum system that had no environmental impact.
The results show that when the particles in the system interact with each other, they form bonds called quantum correlations. Once they appear, these correlations will be locked and cannot be deleted. The team has demonstrated with a Mathematical theoretical method that no operation that can completely disrupt these bonds.
That means that in a closed quantum system, the amount of information shared between particles always increases over time and this process is impossible. It is the continuous increase of internal correlations that has created a one-way direction for time.
Professor Sun Changpu, Chinese Academy of Sciences, assessed this study as an important step forward in connecting quantum physics with the familiar laws of the macro world.
However, the authors are also cautious about saying that the results are currently only at the theoretical model and need more experimental research to verify in the future.
