For the first time, physicists have directly observed that “holes” within light can travel faster than the light surrounding them.
These features, called phase singularities or optical vortices, were predicted decades ago. Since the 1970s, scientists have suggested that, much like whirlpools in a river can move faster than the water itself, swirling gaps within a light wave could also outpace the beam they exist within.
Why the Discovery Does Not Break Relativity
This does not break relativity, since the vortices carry no mass, energy, or information—their apparent faster-than-light motion comes from the wave’s changing shape, not actual movement.
Observing this effect experimentally has been extremely challenging because it happens across incredibly tiny distances and timescales. Successfully capturing it marks a major breakthrough made possible through advanced electron microscopy.
“Our discovery uncovers fundamental laws of nature that apply universally to all wave systems,” explains Ido Kaminer. “These systems range from sound waves and fluid motion to advanced materials like superconductors.”
He adds that the breakthrough also introduces a powerful new technological capability: tracking the movement of fragile nanoscale phenomena inside materials. This is made possible through electron interferometry, a new imaging technique that significantly improves image clarity and detail.
Hidden Complexity Within Light
Although light may seem smooth and uniform to the human eye, it actually contains intricate structures that are difficult to detect. Like other systems governed by flow dynamics, light can develop disturbances known as optical vortices, a type of phase singularity.
Because light behaves as both a wave and a particle, these vortices form when the wave twists in a corkscrew-like pattern as it propagates. At the exact center of the twist, the wave cancels itself out, creating a point of zero brightness—essentially a dark “hole” within the light.
Mathematical models show that when two singularities exist within the same frame of reference, they naturally pull toward one another. As they get closer, they accelerate, reaching speeds that can appear to surpass the speed of light in a vacuum.
The researchers explain in their paper that when singularities with opposite charges move toward one another, their trajectories in spacetime must remain continuous at the point where they annihilate. As a result, their acceleration is driven to extreme, effectively unbounded speeds just before they disappear.
The Challenge of Capturing Vortex Dynamics in Light
This phenomenon occurs in other systems, but observing it in light is harder, as previous tools couldn’t keep up with the rapid formation and motion of optical vortices.
To overcome this obstacle, Ido Kaminer and his team captured the dynamics of optical vortices inside a two-dimensional material known as hexagonal boron nitride.
This material can sustain unusual waves called phonon polaritons—mixed excitations that combine light with atomic vibrations. Slower, confined waves create complex vortex-rich patterns, allowing researchers to track their motion precisely.
The second and most critical step was capturing these dynamics as they happened in real time. To achieve this, the team used a specialized ultrafast electron microscope with exceptional spatial and temporal precision, allowing them to record processes occurring within just three quadrillionths of a second.
The team repeated the experiment multiple times, introducing a slightly different delay in each run. By combining the hundreds of resulting images, they assembled a time-lapse sequence showing the vortices racing toward one another and ultimately annihilating. During this brief encounter, their speeds momentarily appeared to surpass the speed of light.
Toward More Complex Light Dynamics
Because the experiment was conducted in a two-dimensional setting, the researchers say the next goal is to expand the method into higher dimensions, where even more complex behaviors may emerge.
They also note that the advanced techniques developed for this work could help overcome several existing limitations in electron microscopy.
According to Ido Kaminer, these novel microscopy methods may open the door to exploring previously hidden ultrafast processes in physics, chemistry, and biology, offering an unprecedented glimpse into nature at its fastest and most elusive moments.
Read the original article on:sciencealert
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