Chinese researchers have proposed a simple yet powerful theory to explain one of physics’ oldest puzzles: why time only moves forward and why travelling to the past remains impossible.
Physicist Cai Qingyu and his team at Hainan University in southern China have developed a fresh explanation at the quantum level for why we cannot unscramble an egg or grow younger, even though the laws of physics perfectly allow time to go backwards.
Unlike earlier theories, their framework does not rely on observations, measurements or external disturbances, the scientists explained in a study published this month by the peer-reviewed journal Annals of Physics.
Instead, it shows that time’s arrow can emerge naturally from how quantum parts become interconnected, a process built into the fabric of microscopic physics itself, they reported.
In the cinema classic Back to the Future, Emmett “Doc” Brown, played by Christopher Lloyd (left), transported Michael J. Fox as Marty McFly to 1985 in a modified DeLorean sports car. Photo: Universal Pictures
In the late 1800s, Austrian physicist Ludwig Boltzmann proposed that time moves forward because isolated systems tend to evolve from order to disorder – an idea known as entropy – rather than the other way round.