Christine Plankenhorns age l2. of Williamsport, PA for her question:
What makes the noise of thunder?
The roaring thunder sounds like an explosion. And so it is. It is an explosion very like the one caused when a plane breaks the sound barrier. The air is piled up so fast that it bursts. This is caused by the flash of lightning that comes before the thunder.
Most fierce storms can produce lightning and thunder. The howling hurricane thunders and often the tornado. But most of the worlds thunder is made by ordinary thunderstorms. These small local storms are plentiful enough. Over the whole worlds about 4,000 of them occur every day. Right now the thunder is rolling its drums for some 1,800 thunderstorms scattered over the world.
A thunderstorm is a heaving mass of turbulent air; It is rarely bigger than 30 to 40 miles in width. It usually wears itself out in a path less than 100 miles long. But there is violent activity in the storm while it lasts.
This activity generates a great deal of electricity. In fact the cloud becomes overloaded with electricity.. It builds up until same of it must be discharged. This surplus electricity is discharged in the streak of lightning. In less than a second it branches zigzags or flashes across the glowering skies.
There may be but a few thousand amperes of electricity in a flash of lightning. Again there may be up to 100,000 amperes. A sizable thunderstorm could discharge 100 million volts of electricity in lightning.
That is the kind of electric power behind the lightning. No wonder it can crack the sound barrier. The current flashes through the damp air. The air tries to resist it. It forces it to zig‑zag. But the powerful current breaks a narrow path through the air. This path of air is made terrifically hot. It must expand but is held in by the cools heavy air around it. So in order to expand it must explode. The roaring thunder is the exploding hot air in the path of the searing lightning.
The eight of the lightning reaches you with the speed of light. The thunder must travel more slowly It comes with the speed of sound about 10100 feet a second. That is why you see the flash before you hear the roar. You can use this to check the distance of a thunderstorm. Count off the seconds between the flash and the roar. Allow five seconds for each mile of distance between you and the storm.
Sometimes the thunder rolls like drums.. This is caused as the noise echoes to and fro. When a cloud lights with distant sheet lightning. you often fail to hear the thunder. This is because the storm is too far away. The sound of the thunder has worn itself out before it reaches your ears.