Lightning illuminates the sky during a storm because it is a phenomenon of electrical discharges that occur between positive and negative electrical charges in the clouds, or between a cloud and the ground.
A lightning bolt is mainly a huge electric discharge that occurs between two differently charged areas within a cloud, or between a cloud and the ground. Imagine a big cumulonimbus (it's the large dark cloud that signals a storm): inside, ice and water particles violently collide due to very intense air movements. These collisions create electrical charges, positive at the top of the cloud and negative at its lower part. When the difference in charges becomes too great, a kind of massive short circuit occurs: the lightning appears. It abruptly restores the electrical balance. All of this lasts only a few fractions of a second, although sometimes several rapid discharges follow one another, giving the impression of a flickering lightning bolt.
During a storm, intense air currents stir clouds and particles of water and ice, causing friction. This friction strips negatively charged particles (the electrons) from certain elements to accumulate elsewhere. The result: a huge electrical imbalance is created between two areas of the cloud or between the cloud and the ground. At some point, the difference becomes so strong that the air (usually an insulator) can no longer hold back the electricity. Then, bam! A lightning bolt occurs, abruptly releasing this energy in the form of an electrical discharge. This discharge instantly heats the air to about 30,000 degrees Celsius (!), literally causing it to explode and emit an intense bluish white light. This dazzling flash is precisely what we notice in the sky at the moment of the lightning strike.
A lightning bolt appears super bright because it releases an enormous amount of energy in the blink of an eye. Essentially, it's like a huge electric discharge, sometimes reaching tens of thousands of amperes, which suddenly heats the surrounding air. This abrupt heating brings the air to a temperature close to 30,000 degrees Celsius, hotter than the surface of the Sun (just that!). This extreme heat causes an intense emission of visible light, giving the lightning its particularly brilliant appearance. Our eyes, accustomed to the low light of a cloudy sky during a storm, then see the contrast with the suddenly intensified lightning, further enhancing this impression of brightness. The lightning is also powerful enough to illuminate the nearby clouds and environment, visually amplifying the phenomenon and making it visible even several kilometers around.
When a lightning bolt crosses the sky, the light it emits immediately spreads in all directions. This phenomenon is due to the scattering and reflection of light on the particles and water droplets present in the clouds. Like an immense natural flash, the lightning illuminates both the inside of the clouds and the surroundings, creating this spectacular effect of a fully lit sky. The clouds act somewhat like gigantic reflective screens, bouncing and scattering light over a wide area. The more clouds and particles there are, the more intense and vast the light effect seems. That’s why a single lightning strike, even if brief, can illuminate the entire city or surrounding landscape in a fraction of a second.
The brightness of lightning depends on a few key elements. First, the amount of electrical energy exchanged during the discharge: the higher it is, the more intense the light. The thickness and length of the lightning channel also play an essential role. A wide and long lightning bolt releases more energy, creating a more spectacular flash. The humidity level of the air and the presence of suspended particles (such as dust or pollution) also influence light diffusion, sometimes making the lightning appear even brighter to the observer. Finally, the distance from which one observes makes all the difference: the closer you are, the brighter the lightning will seem, logically.
Some lightning bolts, called 'sprites' or red lightning, appear above storm clouds at altitudes exceeding 50 kilometers and last only a few milliseconds. Very rare and difficult to observe, they continue to intrigue researchers.
Research has shown that lightning activity could help naturally fertilize soils by allowing the formation of nitrogen oxides, which then fall to the ground in the form of nitrates that are beneficial to plants.
Every second, about 50 to 100 lightning strikes hit the Earth somewhere in the world, totaling around 1.4 billion strikes per year.
The phenomenon known as 'fulgurite' occurs when lightning strikes sand. The extreme heat generated by the impact is capable of melting the sand, thereby creating very spectacular natural vitrified tubes.
Yes, lightning can take different forms. There are intra-cloud lightning (within the storm cloud itself), inter-cloud lightning (between multiple clouds), and cloud-to-ground lightning, which are the most visible and bright discharges for the observer on the ground.
When a lightning strike occurs, the temperature of the surrounding air can reach about 30,000 degrees Celsius, which is five times hotter than the surface of the sun. This extreme temperature explains the intense brightness observed during lightning strikes.
It is currently impossible to know precisely where and when a lightning strike will occur. However, it is known that lightning has a preference for the highest points or tall conductive objects, such as trees or buildings equipped with lightning rods.
A typical lightning bolt lasts less than a second, often only between 30 and 100 milliseconds. However, it appears longer to the naked eye due to its intense brightness and the rapid succession of multiple bright discharges.
Thunder is the result of the extremely rapid expansion of air heated by the electric discharge of lightning. This powerful expansion creates a sound wave, audible in the form of a detonation called thunder.
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