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Why is sugar not transparent? Because light that penetrates a piece of sugar is scattered, altered and deflected in a highly complicated way. However, as a research team from TU Wien (Vienna) and Utrecht University (Netherlands) has now been able to show, there is a class of very special light waves for which this does not apply: for any specific disordered medium—such as the sugar cube you may just have put in your coffee—tailor-made light beams can be constructed that are practically not changed by this medium, but only attenuated. The light beam penetrates the medium, and a light pattern...

(The University of Queensland) =============================================================== Like watching a movie in reverse, physicists have just demonstrated a new technique for the time-reversal of a wave of optical light. That doesn't mean that they have actually reversed the flow of time; rather, they have found a way to induce an optical wave to retrace a forward path in reverse, returning to its point of origin. It's the first time that time reversal of optical waves has been achieved with full control over all of the degrees of freedom of light simultaneously. This would be a massive achievement in and of itself, but...