In summer, there are often lightning and thunder (lightning). When the electric fields between the positive and negative charges in the rain cloud differ significantly, these two types of charges will neutralize and cause lightning. That phenomenon is called lightning discharge. When lightning strikes, there is a flash of intense bright light. Furthermore, the lightning path produces very high temperatures, causing the surrounding air to expand, causing intense explosions suddenly. The flash is lightning, and the explosion is the sound of thunder.
Lightning and thunder arise in the presence of lightning, but why do we see lightning first and then hear the thunder? That’s because the speed of light is much faster than the speed of sound. Light travels through the air at a speed of 300,000 km / s, which equates to 7.5 cycles of equatorial circumference in a second. The sound speed in the air is only 340 m / s, only one-tenth of the speed of light. Since the lightning occurred to the ground, the time was only one-tenth of a second, but with that distance, the thunder had to travel a quite long time. Based on that, we can use the time from seeing lightning to hearing thunder to work out how far away the discharge is.
There are times when only lightning can be heard, but no thunder is heard; it is because the thundercloud is too far away from us, or the sound of thunder cannot be heard enough. As the energy of sound traveling through the air gradually decreases, we cannot hear it in the end.
There will be a corresponding thunder once there is lightning, but why are there times when only a flash of lightning is seen, and thunder’s sound lasts for a while before it stops?
This is because the flash is very long; there are flashes of up to 2 – 3 km, even 10 km. Because lightning is separated from us at different distances, the time it takes for thunder to reach our ears before and after is also different. On the other hand, lightning usually does not arise once and finishes, but it arises several times in a blink of an eye. So when the thunder of the first flash has not ended, the second and third lightning has passed. These thunderstorms are mixed to make thunder resounding forever.
When rain encounters the ground, structures, high mountains, or clouds, the sound is reflected, causing echoes. The time these responses reach our ears also varies greatly, thus causing thunder to resonate. Sometimes due to many reasons, the thunder resounds forever, lasting about a minute.