🔊 THUNDER: WHY IT RUMBLES
PAGE 1 OF 5, LIGHT THEN SOUND
BOOM!
THUNDER IS LIGHTNING'S SOUND
Every thunder clap starts with a lightning bolt. The bolt superheats the thin air along its path to about 30,000°C in microseconds. That is roughly five times hotter than the Sun's visible surface. The air does not stay hot. It expands outward explosively, pushing neighbouring air aside like a fast punch. That sudden push creates a shockwave, and shockwaves are what we hear as thunder. Without lightning there would be no thunder. The flash and the boom are two sides of the same storm event.
👁️ SEE FIRST
Light travels about 300,000 km per second. Sound in air travels only about 343 m per second. That is why you always see the flash before you hear the boom.
BOOM!
FLASH
⚡ Lightning heats a narrow channel of air so fast the heat has no time to spread away gently.
💡 Your eyes receive the flash almost instantly because light is incredibly fast.
💡 Your eyes receive the flash almost instantly because light is incredibly fast.
DELAY
⏱️ Count seconds from flash to thunder. Three seconds is about one kilometre to the bolt.
🏃 A short delay means the storm is still dangerously close to you.
🏃 A short delay means the storm is still dangerously close to you.