Physicists have discovered something that moves faster than light: the darkness inside it

For the first time, physicists have observed that ‘holes’ in light can travel faster than light itself.

They are known as phase singularities or optical vortices, and since the 1970s, scientists have predicted that just as riverbanks can move faster than the water flowing around them, eddies in light waves can propel the light embedded within them.

This does not violate relativity, which states that nothing can travel faster than the speed of light. That’s because vortices carry no mass, energy, or information, and their motion is based on the evolving geometry of the wave pattern rather than any physical motion through space.

However, this phenomenon has been difficult to capture in action because it occurs on extremely small scales of space and time. The achievement is a triumph of electron microscopy.

“Our discovery reveals universal laws of nature shared by all types of waves, from sound waves and fluid flow to complex systems such as superconductors,” says Ido Kaminer, a physicist at the Technion Israel Institute of Technology.

“This breakthrough provides us with a powerful technical tool: the ability to map the motion of delicate nanoscale phenomena in materials, revealed through a new method (electron interferometry) that increases image sharpness.”

Even though the same light appears to our eyes, there are many things going on in it that we cannot easily perceive. Light can be subject to disturbances similar to those seen in other systems dominated by flow dynamics, including a type of phase singularity scientists call optical vortices.

Light can behave as both a particle and a wave; An optical vortex forms when the wave rotates as it travels, like a corkscrew. At the very center of that twist, the light cancels itself out, leaving a point of zero intensity—a sort of dark “hole” in the light.

It is understood mathematically that two eccentricities in the reference frame will be drawn together, gaining speed as they approach, reaching an apparent velocity greater than the speed of light in a vacuum.

“As oppositely-charged singularities approach each other, their paths in spacetime must form a continuous curve at the point of annihilation, forcing their acceleration to infinite velocities before annihilation,” the researchers explain in their paper.

This has been observed in other systems, but studying how this scenario might play out in the light field is somewhat difficult. Much work has been done to study it in physics laboratories, but observations of optical vortices have been limited by the inability of technology to keep up with the speed at which vortex formation, motion, and collision unfold.

To overcome these limitations, Kaminer and his colleagues recorded the behavior of optical vortices in a two-dimensional material called hexagonal boron nitride.

This material supports unusual light waves called phonon polaritons—hybrids of light and molecular vibrations—that move much more slowly than light alone and can be tightly confined. This creates complex interference patterns filled with multiple vortices, allowing researchers to track their motion in detail.

The second, important part was capturing those dynamics in real time. The team deployed a special high-speed electron microscope with unprecedented spatial and temporal resolution, recording events over 3 quadrillionths of a second.

Related: Gamma-ray bursts can travel faster than light because they seem to go backwards in time

They ran the experiment several times, each time recording with a slight delay compared to the previous run. By stacking together the hundreds of images thus generated, the researchers created a timelapse of the vortices as they hurtled and destroyed each other, their speeds briefly reaching superluminal speeds in the process.

The experiment took place in a two-dimensional context. The next step, the researchers say, is to try to extend their work to higher dimensions to observe more complex behavior. They also say that the techniques they have developed could help address the current limitations of electron microscopy.

“We believe these innovative microscopy techniques will enable the study of hidden processes in physics, chemistry and biology,” says Kaminer, “revealing for the first time how nature behaves at its fastest and most elusive moments.”

Research has been published in Nature.

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