ELi5: Why does the time between lightning striking and when you hear the thunder correlate to how far the lightning landed?

Question

ELi5: Why does the time between lightning striking and when you hear the thunder correlate to how far the lightning landed?

In: Physics

Answer 1

Sound travels through different mediums at relatively constantly speeds. The same can be said for light. You see the lightning first because light travels faster than sound. How far ahead the light is tells you how far the lightning is. If it is a mile away, the thunder will arrive 5 seconds later