Sometimes, under certain conditions, a small and relatively spherical piece of the atmosphere that surrounds us briefly ignites. Since this phenomenon is best seen at night and has no obvious natural explanation, it is not surprising that many myths have arisen around it. These balls of fire are called wandering lights, St. Elmo's lights, ghost lights, or fireballs. Previously, it was believed that they hang with our graves, dance along the banks of rivers, signal the approach of an earthquake and penetrate the cabins of aircraft. Even today we do not have a clear explanation of how they arise and what they do. But this does not mean that scientists have given up trying to figure it out. In June, the Chinese scholar Hui-Chun Wu proposed a compelling new explanation for this phenomenon,by publishing an article in Scientific Reports.
Some fireballs are a waste product of living organisms. For example, the decomposition of living matter in swampy areas (or even at mass graves in Polish forests) releases methane and phosphorus-containing gases such as hydrogen phosphate, which can suddenly ignite on contact with oxygen, resulting in a flickering spot of light suspended in air. Other fireballs are electrical in nature, flaring up inside the earth during earthquakes, when the collision of boulders releases a stream of electrons that rise to the surface, where they interact with the air, creating flashes of light. But some fireballs form in the atmosphere, usually during severe thunderstorms, and they are called fireballs.
Ball lightning can be of any color of the rainbow and in a wide variety of sizes - from the usual toy glass ball to the large fitballs that people sometimes sit on. They can form inside confined spaces, run down chimneys, and even penetrate closed windows. In addition to producing light, fireballs can generate discharges and often emit a hiss or buzz and a strong foul odor. Typically, fireball lasts only a few seconds and burns with the intensity of a bright household light bulb. The unpredictable and volatile nature of ball lightning makes it difficult to formulate a convincing theory to explain its nature, but reports of its oddities have been received for centuries and continue to arrive today.
For example, in the spring of 1963, the late astronomer Roger Jennison was on a night flight through thunderclouds and noticed the appearance of a burning ball the size of a basketball shortly after lightning struck the plane. According to him, this balloon "appeared from the side of the cockpit and flew down the aisle between the seats, maintaining a constant altitude and course all the way until it was visible." On another occasion, a resident of the United Kingdom said that she was at home “when a huge orange ball, similar to a grapefruit, but more orange and friable around the edges, flew in through a window that was closed and on which the curtains were also drawn. It flew horizontally at about shoulder height for about 10 seconds, after which there was a thunderclap just over my head, so strong that I fell off the chair."
The penetration of ball lightning into residential buildings and their ability to form inside aircraft turned out to be extremely difficult to explain. The explanations for how they form are even more varied than their physical characteristics. For example, according to various theories, ball lightning can be a cloud of incandescent silicon particles, a natural nuclear reaction, an epileptic hallucination caused by lightning, a miniature black hole, a compound of cellulose and other natural polymers, and a microwave-filled plasma bubble.
The microwave bubble hypothesis is the basis for the work of Wu, a scientist at Zhejiang University in Hangzhou, China. Scientists previously assumed that such bubbles could form under the influence of microwave radiation from thunderclouds or atmospheric masers, but Wu hypothesized that these microwaves come from a beam of electrons that accelerate almost to the speed of light when lightning strikes the ground. These electrons are accelerated to such speeds under the influence of the electric field, which occurs when the stream of electrons moves stepwise from the base of the cloud to the ground just before a bright flash of lightning. "At the tip of a flash of lightning that reaches the ground," writes Wu, "a beam of electrons moving at near-light speed can form, which in turn generates intense microwave radiation."
Regardless of the source, atmospheric microwaves generate plasma, charging the surrounding air. This radiation exerts enough pressure to form a bubble from the scattered plasma, which we call ball lightning. The microwaves that are trapped inside this bubble continue to generate plasma and thus maintain the bubble for its short life. Eventually, the ball lightning dies out because the radiation inside the bubble is scattered. Sometimes this bubble bursts, the microwaves are released outward, which leads to an explosion.
The presence of microwaves and plasma as components of ball lightning may explain some of its properties. For example, microwaves can penetrate window glass, so closed windows do not interfere with the appearance of ball lightning in the room. Microwaves can also produce a noticeable sound when they come into contact with the human inner ear, and the plasma they generate can in turn produce ozone from atmospheric oxygen, which has a pungent odor.
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What distinguishes ball lightning theory from other theories is that it explains how they appear inside airplanes. Electrons, tiny cousins of atoms, are able to pass through the metal skin of an aircraft body after they have reached near-light speeds outside of it, thanks to a flash of lightning. Then the electrons trapped inside the plane emit microwaves, which form ball lightning. The sequence of electrons-microwaves-plasma also explains the size of fireballs, since the length of the electron beam dispersed by a lightning strike corresponds to the typical diameter of the resulting microwave bubble - about 20-50 centimeters.
As is always the case with new scientific hypotheses, now you need to do a lot of work to confirm the assumption of W. It will take a lot of experiments to test the electron-microwave-plasma mechanism, as a result of which ball lightning is formed. Here it will be necessary to develop a methodology for generating ball lightning on demand, and then study the characteristics of electrons and microwaves.
According to Wu, if his hypothesis is confirmed, his theory will raise several important questions regarding the threats posed by fast electrons and microwave radiation that arise near people caught in a thunderstorm. Think about what happened last year in South Dakota. A video filmed by a witness to the incident shows a ball of light falling rapidly from the sky during a thunderstorm.