Thunder, the booming sound you hear during thunderstorms, happens because of the complex processes triggered by lightning. Let’s delve into the science behind thunders and discover the fascinating elements that make it happen.
Thunder Formation
The creation of thunder is closely tied to the lightning discharge process. When a lightning bolt connects with the ground, it initiates a second stroke that travels back from the ground to the clouds, following the same channel as the first strike. This return stroke further elevates the temperature of the surrounding air, reaching around 27,000 degrees Celsius (48,632 degrees Fahrenheit).
The rapid increase in temperature leads to a significant rise in air pressure, reaching levels 10 to 100 times higher than normal atmospheric pressure. The heated air explosively expands outward, compressing the surrounding air and creating a shockwave. This shockwave manifests as a booming burst of noise in every direction, constituting the audible phenomenon we identify as thunder.
Thermal Dynamics of Thunder
The temperature inside a lightning channel undergoes a rapid transformation during its 50 microseconds of existence. It rises sharply from 20,000 K to 30,000 K, creating a shock wave that expands outward faster than sound. This shock wave, akin to those from explosions or supersonic aircraft, leads to sound pressure levels in thunder ranging from 165 to 180 dB, occasionally exceeding 200 dB.
Different Types of Thunder
Research categorizes thunder sounds based on loudness, duration, and pitch. Claps, loud with higher pitches, last 0.2 to 2 seconds. Peals exhibit changing loudness and pitch, while rolls are irregular mixtures. Rumbles, less loud and lasting over 30 seconds, have a low pitch.
Additionally, Inversion thunder occurs during lightning strikes between clouds and the ground in temperature inversion conditions. This intensifies thunder sounds due to greater acoustic energy concentration in the near-ground layer. Cloud-to-ground lightning involves return strokes, with later strokes possessing greater acoustic energy.
Auditory Perception of Thunder
To understand the sound of thunder, it’s crucial to recognize that lightning is usually close to vertical, following the shortest route dictated by the electrical forces. The shock waves produced by lightning reach the observer’s ear in a sequence. The thunder generated by the closest lightning channels is heard first, followed by the thunder from more distant portions of the channel.
The Study of Thunder
Brontology, the scientific study of thunder, has evolved over centuries. Early theories attributed thunder to deities, while ancient Greek philosophers linked it to natural causes like wind and air movements within clouds. In the mid-19th century, a prevalent theory suggested that lightning-induced vacuums collapsed, generating thunder. Later, a consensus emerged, emphasizing the role of a shock wave resulting from the sudden thermal expansion of plasma in the lightning channel.
Consequences of Thunder
Thunder’s shock wave isn’t merely a sonic spectacle; it can cause property damage and internal contusions to those nearby. The sheer force of thunder can rupture eardrums, resulting in permanent hearing impairment or temporary deafness.
Thunder Fun Facts
- To estimate the proximity of lightning, count the seconds between the flash and the thunderclap, with each second representing approximately 300 meters.
- Thunder is not exclusive to thunderstorms; it can occasionally be heard during snowfall as well.
- In April 1885, five lightning bolts struck the Washington Monument during a thunderstorm, yet no thunder was ever heard.
FAQs
Q : Is thunder always accompanied by lightning?
A : Yes, thunder and lightning are closely related phenomena. Thunder is the sound produced by the rapid expansion and contraction of air due to the heat generated by lightning.
Q : Can you hear thunder from space?
A : No, sound waves require a medium (such as air) to travel through. Since space is a vacuum devoid of air, sound cannot travel through it.
Q : Can thunder ever be completely silent?
A : Thunder is a result of sound wave propagation, and for it to be perceived, there needs to be a medium through which sound can travel. In the vacuum of space, for example, there would be no medium for thunder to travel, so it would not be audible.
