Thunderstorms make noise because of lightning. When a flash of lightning occurs during a thunderstorm, it heats the air around it to an extremely high temperature, causing a rapid expansion of the air. This sudden heating and expansion create a shock wave that is heard as thunder.
Thunder is caused by lightning. When a flash of lightning tears through the sky, it very abruptly heats the air around it (we're talking about around 30,000°C, which is five times the surface temperature of the sun!). This heated air violently expands at very high speed, forming a sound shock wave that corresponds to the sound of thunder. In other words, the rumble we hear is nothing more than the air exploding and vibrating due to this sudden expansion caused by the intense heat of the lightning.
Lightning is a massive electric current that brutally heats the air around it. In a fraction of a second, this temperature rises to nearly 30,000 °C, about five times that of the surface of the sun. Rapidly heated, the air expands very quickly and creates a kind of shock wave. It's exactly like a supersonic explosion. This wave propagates in all directions and becomes the famous thunder that we hear during a storm. The more powerful and closer the lightning is, the more impressive the crack is.
The duration and intensity of thunder mainly depend on the shape and length of the lightning. If the lightning is straight and relatively short, you will hear a rather brief and quite loud noise all at once. But if the lightning zigzags or stretches over a long distance, the sound reaches your ears at different times, creating that longer rumble we all know. The intensity of the noise also changes depending on the distance: when the storm is very close, it cracks very loudly and sharply; but from afar, it transforms into a deep roll. The ambient air, its temperature, and humidity also influence the sound you hear, either amplifying or muffling the rumble.
Distance directly affects the way we hear thunder. The farther away a lightning strike occurs, the longer the sound takes to reach your ears. This is simply because light travels much faster than sound. Generally, you just need to count the seconds between the observed lightning and the sound heard: every three-second interval represents approximately one kilometer. So, the farther away you are, the more you hear the thunder as a deep, prolonged rumble, less distinct and sometimes downright muffled. Conversely, when the lightning strikes very close, the sound of the thunder will seem very loud, sharp, even explosive.
The way the sound of thunder reaches us can be modified by several easily identifiable environmental factors. Topography, for example, plays a significant role: if mountains or hills are around you, they can reflect the sound wave and create an echo effect that prolongs or amplifies the initial noise of thunder. The same principle applies to buildings in the city; facades and narrow streets also produce quite a bit of acoustic bouncing, which can sometimes enhance the sensation of intensity. The humidity of the air also has an influence; very humid air transmits sound better, which can help make thunder more distinct. Conversely, dry and warm air can muffle sounds quite quickly. The wind slightly modifies sound propagation: a favorable wind pushes the noise toward your ears, while a headwind disperses or significantly diminishes the sound. The same goes for the presence of natural obstacles like thick forests: dense vegetation partially absorbs sounds and can make the storm a bit quieter to your ears.
Did you know that a lightning bolt can measure several kilometers in length and only a few centimeters in width? Despite this visual slenderness, the energy released is impressive, producing the characteristic rumble of thunder.
There are several types of lightning, such as intra-cloud, cloud-to-ground, or cloud-to-air lightning. It is mainly the cloud-to-ground lightning that produces the thunderous and resounding noise we call thunder.
When you see a flash of lightning, you can easily estimate its distance by counting the seconds between the moment the flash appears and when you hear the thunder. Each interval of about 3 seconds corresponds to a distance of 1 kilometer.
A lightning bolt can carry an electric charge equivalent to that needed to power a 100-watt bulb for three months. No wonder the energy released by this discharge generates so much noise!
Animals often have a much more sensitive sense of hearing than humans. The loud and unpredictable sound of thunder, combined with atmospheric changes and the static electricity generated by the storm, can cause them stress and make them anxious or fearful.
Yes, you just need to count the number of seconds between the flash of lightning and the sound of thunder. By dividing that number by three, you can approximately determine the distance of the storm in kilometers.
This often results from a phenomenon called 'heat lightning,' which is common when a thunderstorm occurs far away. The sound is then dissipated before it reaches our ears, or it becomes too faint to be distinctly heard.
In general, ordinary thunder does not pose any particular danger to human hearing. However, if lightning strikes very close to a person (within a few dozen meters), the sound intensity can be very high and potentially cause temporary or, more rarely, permanent damage to hearing.
When lightning strikes, it creates a very extensive and irregular electrical channel. The sound generated comes simultaneously from different distances and various locations in the air, reaching your ears gradually. It is this time difference that gives the impression of thunder rumbling or rolling.
The light from a lightning strike travels about a million times faster than the sound of thunder. Therefore, we see the lightning almost instantly, but the sound of thunder takes about 3 seconds to cover a distance of 1 kilometer. Thus, the farther away the lightning is, the greater the delay between the lightning and the thunder.
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