Daniel assumes thunder is the sound of clouds crashing together.

It isn't.

Thunder is the sound of air being ripped apart and snapping back. Lightning superheats the air in its channel to around 30,000 degrees Celsius -- five times hotter than the surface of the sun -- in a fraction of a second. The air explodes outward so fast it creates a shockwave. That shockwave is thunder.

The lightning itself is almost silent. The air around it is what screams.

This episode explains why close lightning cracks and distant lightning rumbles, why you always see the flash before you hear the sound, and how to use the gap between them to measure exactly how far away a storm is.

What you will find in this episode:

• What actually causes thunder -- and why it has nothing to do with clouds
• Why lightning is five times h ...