Scientists see darkness inside light for the first time, and it moves even faster

Scientists have recorded dark spots inside a light wave that seem to be moving much faster than light itself. Even though they appear to be in a quicker motion, they carry no energy or information, and hence, nothing really happens. These dark spots inside a complex light wave are formed when some points go completely dark, because the wave cancels itself out. So there is no light, only darkness. Scientists have known about them for a long time. A study published in Nature states that they have been filmed for the first time. Researchers at the Technion-Israel Institute of Technology collaborated with others from Harvard, Stanford, MIT and other institutions to track these dark points. An electron microscope that can capture events lasting just three femtoseconds, or three quadrillionths of a second, was used to see them passing through a special material. Their work confirmed a long-held belief that what we believe to be darkness can outrun the light surrounding it.

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Known as phase singularities, they appear at the exact point where a light wave’s amplitude drops to zero, leaving its phase undefined. The light vanishes into darkness, while the surrounding phase wraps smoothly through a full 360° rotation around the void. These dark points come in two types, based on the spin direction of the phase. One has a positive charge, the other a negative. They can only disappear if they meet each other. As they move closer, they speed up, and right before they collide and vanish, their speed is expected to shoot toward infinity. This extreme behaviour had been theorised before, but it hadn’t been directly measured until now.

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Watching dark points inside light

“Phase singularities do not carry energy or information and thus can ‘move’ superluminally without breaking causality,” the authors write. What we think is faster than light, is just “a pure kinematic property of the evolving phase landscape.” But witnessing these dark points needs special conditions. Scientists identified hexagonal boron nitride, a two-dimensional crystal that supports a special class of light-matter waves called hyperbolic phonon polaritons, as the ideal material. Inside it, the waves travel more than 100 times slower than light in a vacuum, and this is what sends the dark points racing. The spacing of dark points matched existing theories, as they mirrored the distance patterns found among molecules in a liquid.