In physics, a famous paradox that hangs by a thread of light
(PHYSorg.com Physics)

Imagine a metal bar that has been heated at one end. Instead of the heat gradually spreading over its entire length, the bar eventually becomes hot again at the place where it was originally. The fact that, paradoxically, a complex system returns to its original state instead of evolving toward equilibrium has drawn the attention of physicists for more than 60 years. Thanks to a series of advances in optical fibres, much richer and complete than before, our French-Italian team of researchers has just taken a crucial step in better understanding this phenomenon.