Physicists Succeed In Reversing Time

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Reversing time impossible? That was so ‘five minutes’ ago! Until recently, it has been safe to assume that time only moves forward. But apparently, this rule doesn’t apply to quantum systems. Physicists have been studying a phenomenon that seems to reverse the arrow of time, the idea that natural processes run forward but not in reverse, dictated by the second law of thermodynamics. You read that right; scientists have just succeeded in reversing time.

The law states that entropy tends to increase over time and explains why glass is easy to shatter but nearly impossible to put back together. The new result reveals that “the arrow of time is not an absolute concept, but a relative concept,” study co-author Eric Lutz explains.

Lutz and his team were able to reverse the arrow of time for two quantum particles because they were correlated, meaning that their properties were linked in a way that doesn’t hold true for larger objects. The results mean that the particles share information, which holds a physical significance in thermodynamics.

“There’s order in the form of correlations,” physicist David Jennings of the University of Oxford noted, arguing that this order “is like fuel” that can be consumed to drive heat to flow in reverse.

The experimenters manipulated molecules of chloroform, which are made of carbon, hydrogen and chlorine atoms. The researchers prepared the molecules so that the temperature was greater for the hydrogen nucleus than for the carbon. When the two nuclei’s energy states were uncorrelated, the heat flowed normally, from hot hydrogen to cold carbon. When the two had strong quantum correlations, the heat flowed backward.

“It’s not that it’s contradicting any laws of physics,” Vlatko Vedral, a physicist at the University of Oxford notes. It’s simply that the second law of thermodynamics assumes that there are no such correlations.