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For the first time, an experiment has confirmed that the laws of thermodynamics hold true even at the quantum level – which means that even in the quantum world, you can’t unspill that glass of milk. The reason time runs the way it does in our everyday lives is because of the second law of thermodynamics, which states that over time all systems become more disordered, or increase in entropy. And that process is irreversible, which is why time only moves forward. But theoretical physicists had predicted that on the quantum level, the process might go both ways.

That’s because when you start dealing with really, really small particles, the laws of physics – such as the Schrödinger equation – are 'time-symmetric' or reversible. "In theory, forward and backward microscopic processes are indistinguishable," writes Lisa Zyga for Phys.org. Now physicists led by the Federal University of ABC in Brazil have performed an experiment that confirms that those theories don’t match up with the reality, with thermodynamic processes remaining irreversible even in quantum systems. But they still don’t understand why that’s the case.

"Our experiment shows the irreversible nature of quantum dynamics, but does not pinpoint, experimentally, what causes it at the microscopic level, what determines the onset of the arrow of time," one of the researchers, Mauro Paternostro from Queen's University in Ireland, told Phys.org. "Addressing it would clarify the ultimate reason for its emergence."

Read the full article here.

http://www.sciencealert.com/physicists-confirm-that-time-moves-forward-even-in-the-quantum-world