Lightning lights up the sky in a dramatic flash, but scientists still don’t fully understand how it starts.
Now, researchers at the Institute of Science and Technology Austria (ISTA) have developed a remarkable new way to study one of nature’s most powerful forces—by trapping and charging a single microscopic particle of dust with lasers.
Using what are known as “optical tweezers,” Ph.D. student Andrea Stöllner and her colleagues can catch and hold an incredibly small particle in mid-air using nothing but light.
These particles, called aerosols, are tiny liquid or solid bits that float through the air around us. Some are visible, like pollen.
Others, such as viruses or fine dust, are far too small to see. In clouds, aerosols act as the building blocks of ice crystals, which play an important role in thunderstorms and lightning.
Inside the lab, two green laser beams travel through a maze of mirrors mounted on a special anti-vibration table.
This heavy table absorbs the slightest movements from the surrounding environment, creating perfect stillness for the experiment. When the beams meet inside a small container, they form a “trap” that can capture a single transparent silica particle and hold it perfectly steady in space.
The first time Stöllner successfully trapped a particle was an unforgettable moment. The tiny speck glowed green as it hovered in place, held entirely by the force of the lasers.
Back then, it only stayed trapped for a few minutes. After years of careful adjustments and refinements, the team can now hold a particle in place for weeks at a time.
At first, the goal was simple: trap a particle and measure its electric charge under different humidity conditions. But the researchers soon discovered something unexpected. The lasers weren’t just holding the particle in place—they were also charging it.
This happens through a process called a “two-photon effect.” Lasers are made of tiny packets of light known as photons.
When two photons hit the particle at the same time, they can knock an electron out of it.
Because electrons are negatively charged, losing one leaves the particle slightly more positive. As this continues, the particle becomes more and more positively charged. By carefully adjusting the laser power, the researchers can control how quickly the charge builds up.
Even more fascinating, they observed the particle occasionally releasing its charge in sudden bursts—tiny electrical discharges. This behavior closely resembles what scientists suspect happens inside storm clouds.
High above our heads, ice crystals and ice pellets collide inside thunderclouds. During these collisions, they transfer electric charges to each other.
Over time, these charges build up across the cloud until a powerful electrical imbalance forms. That imbalance is what eventually leads to a lightning strike. However, one big mystery remains: how does the very first spark begin?
Some theories suggest that it happens right at the surface of charged ice crystals. Others propose that cosmic rays from space might trigger the process. But according to current knowledge, the electrical field inside a typical cloud may be too weak to produce lightning on its own.
This is where the ISTA research could make a difference. By studying how a single particle becomes charged and how it suddenly discharges, the scientists can explore whether tiny, almost invisible electrical sparks might be happening on the smallest scales inside clouds.
These micro-events might be the missing link between slow charge buildup and the dramatic lightning bolt we see from the ground.
Although the silica particles used in the lab are much smaller than real ice crystals in clouds, they act as excellent models. By understanding these microscopic interactions, researchers hope to unlock the larger mystery of lightning formation.
For Stöllner and her team, the excitement isn’t just about solving a scientific puzzle. It’s about watching a tiny floating particle of dust, held in place by light, and realizing it might hold the secret to one of the most powerful and beautiful forces in nature.
Source: KSR.
