Darkness can travel faster than the speed of light — without breaking Einstein’s relativity

A dark point inside a beam of light should not be much of a traveler. Yet in a new experiment, some of those points appeared to move faster than light itself, darting through a wave field before blinking out of existence.

The feat did not involve particles, signals, or any loophole in Einstein’s theory. What the team tracked were optical phase singularities, tiny places where the amplitude of a light wave falls to zero. They are points of complete darkness inside a structured field of light, and because they carry neither mass nor information, their apparent motion can exceed light speed without violating relativity.

That distinction is the heart of a study led by researchers at the Technion-Israel Institute of Technology and published in Nature. The work offers direct measurements of a strange prediction that physicists have discussed since the 1970s but had not been able to watch unfold in real time.

The experiment centered on hexagonal boron nitride, or hBN, a material supplied by Prof. Hanan Herzig Sheinfux of Bar-Ilan University. In hBN, light can couple to vibrations in the material and form hyperbolic phonon-polaritons, hybrid wave packets sometimes described as “light-sound” waves.

Those waves move far more slowly than light in a vacuum, more than 100 times slower in this setup. That slowdown gave the researchers a chance to examine events that would otherwise be too fast and too small to follow.

To do it, the team built a specialized system at the Technion’s Electron Microscopy Center, combining lasers, opto-mechanical components, and an ultrafast transmission electron microscope. The setup reached a spatial resolution of 20 nanometers and a temporal resolution of 3 femtoseconds, enough to resolve activity within a fraction of a single light-wave cycle.

The researchers reconstructed complex interference patterns across a 21 by 21 micrometer field of view and followed the field for hundreds of femtoseconds. In 285 phase-resolved frames, they tracked about 50 singularities per frame as the dark points formed, moved, approached one another, and disappeared.

“These dark points,” also known as vortices, are not little objects hiding in the wave. They are topological defects, marked by a phase winding of plus or minus 2π, which gives them positive or negative charge. Opposite charges can meet and annihilate each other, a behavior that has long invited comparisons to particle-antiparticle pairs.

One of the clearest events came when two oppositely charged singularities rushed toward each other. As they neared annihilation, their trajectories bent into a continuous space-time curve. According to the theory, that geometry forces a sharp acceleration just before the pair vanishes.

The experiment captured exactly that kind of behavior.

The researchers write that the singularities’ velocities can become formally divergent near creation and annihilation events. In practical terms, that means their apparent speeds can spike to extreme values as the wave field reshapes itself around the zero-amplitude point.

“This breakthrough provides us with a powerful technological tool,” said Prof. Ido Kaminer of the Technion’s Andrew and Erna Viterbi Faculty of Electrical and Computer Engineering. He said the approach could help scientists map delicate nanoscale phenomena in materials and study hidden processes in physics, chemistry and biology.

The point is not that something physical outran light. The point is that the moving location of darkness inside the field did.

That may sound like a trick of language, but it is an important physical distinction. Einstein’s speed limit applies to matter, energy, and information. These singularities are none of those. Their superluminal motion is a kinematic feature of the evolving phase landscape, not a signal racing from one place to another.

Physicists have often treated phase singularities as particle-like because they are stable, carry topological charge, and can be created or annihilated in pairs. Earlier work also showed that their spacing resembles the short-range order seen in liquids.

The new study confirmed that pattern. The measured distance correlations between singularities matched the well-known random-wave model and supported the view that, spatially at least, these defects behave a little like interacting particles.

But the velocity data told a more unusual story.

Instead of following an ordinary particle-like spread of speeds, the singularities showed a heavy-tailed velocity distribution. Extreme events were not rare outliers. The average velocity measured in the experiment was about 3.12 × 10^8 meters per second, roughly 1.04 times the speed of light in vacuum.

By the team’s analysis, 29 percent of the singularities in this system exceeded light speed. Under the same laser conditions in free space, theory suggested only 0.4 percent would do so.

That contrast came from the unusual properties of hBN. Because its phonon-polaritons have a slow group velocity, the distribution of possible singularity speeds broadens, making fast events much more likely to appear. In other words, the material did not break any rules, but it made this strange regime easier to catch.

The authors argue that the result matters beyond one optical material. Singularities and related topological defects appear across physics, from flux quanta in superconductors to vortices in fluids and superfluids, and dislocations in crystals. The underlying mathematics can carry over even when the systems themselves look very different.

This experiment, though, still comes with boundaries. It studied singularities in two-dimensional random Gaussian waves, not every kind of wave field. The fastest observable speeds were also limited by the microscope’s present spatial and temporal resolution.

Some regions in the data did not contain enough events to build reliable statistics. And moving from two-dimensional measurements to full three-dimensional near-field imaging remains a major technical hurdle.

Even so, the work gives physicists a way to watch a hidden layer of wave behavior with unusual clarity. It also opens room to test more complex topological states, study polaritons in other two-dimensional materials, and push techniques such as electron holography.

The immediate payoff is not faster-than-light technology. It is sharper measurement of ultrafast, nanoscale motion.

By resolving both phase and timing at deep sub-wavelength and sub-cycle scales, the method could improve the study of nanostructured optical materials, superconducting systems, and other platforms where singularities and topological defects shape behavior.

The paper also points to possible uses in probing exotic topological states, extending polariton studies to other two-dimensional materials, and improving electron holography and related interference methods.

Over time, the same analytical tools may also help electron microscopy tackle long-standing imaging problems such as fluctuating granularity in electron beams.

Research findings are available online in the journal Nature.

The original story "Darkness can travel faster than the speed of light — without breaking Einstein’s relativity" is published in The Brighter Side of News.

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