Thunder arrives after lightning because light travels far faster than sound through air.

The longer version

Light reaches your eyes almost instantly over a few kilometres, while a pressure wave needs several seconds to cover the same ground through air. The flash and the bang are produced together when a lightning channel superheats air, which expands violently and sends out a shock that decays into ordinary thunder.

Counting the gap gives a rough distance, since the wave covers roughly a third of a kilometre each second. A long rumble means the channel was extended: parts of it sat much farther away, so their arrival times smear out. A sharp crack overhead means the strike was close.

Where this entry sits

Sound and Music gathers facts about how vibrations move through air and water, how ears turn them into meaning, and how instruments and notation shape what listeners hear. Expect echoes, pitch, volume, acoustics, and the odd silence in between. The full list sits on the Sound and Music page, where every entry is listed in order.

← Entry 3 Entry 5 →

More From Sound and Music

Eight more entries

An echo is simply a sound wave bouncing off a hard surface and returning to the listener.

A room with soft furnishings produces fewer echoes than an empty room with bare walls.

The human ear collects sound with a funnel of cartilage and skin called the pinna.

Tiny hair cells inside the cochlea convert vibrations into electrical signals the brain can read.

Loud sounds can damage hearing permanently by harming the delicate hair cells in the inner ear.

The eardrum is a thin membrane that vibrates when incoming pressure waves strike it.

Pitch depends mainly on frequency, so faster vibrations are heard as higher notes.

Volume depends mainly on amplitude, so larger vibrations are heard as louder sound.

Read

Try Another Subject

Three collections