Lightning and thunder. Two peas in a pod, always traveling together to create misery and annoyance for the lot of us (not to mention a certain amount of awe – it’s tough not to feel overwhelmed during a lightning storm). But why do these two things always seem to come together? What magical process pairs them together? This can seem especially mystifying if you’re watching a thunderstorm but hear no thunder.
The fact is that lightning is the originator of thunder. You can’t have lightning without thunder. The process by which lightning is created always generates a certain amount of thunder. Let’s look at that process.
– It begins with the water cycle. The sun heats the land and the oceans, and in doing so turns water to vapor. That vapor rises into the air.
– As the vapor hits the atmosphere the temperature begins to drop, and the gas begins to turn back into a liquid. This combined with ice crystals causes the formation of clouds, and can lead to rain in sufficient amounts.
– Though there is some debate over the issue, during this process the clouds can begin to acquire a charge. How this happens is something of a mystery, though it usually involves the interaction of the ice crystals in the clouds and the falling water droplets. This interaction can lead to incredible electrostatic build up, which results in lightning that can either strike other elements in the sky or bolt down to the ground.
And thus begins a thunderstorm, and soon after the lightning begins falling you’ll hear thunder. Why is that?
It’s fairly simple, actually. Think back to science class. What happens to air when it’s heated? It begins to expand. Imagine how much the air would expand when a bolt of lightning, carrying thousands of volts of electricity, passes through it. This is exactly what happens, as the air becomes superheated in a matter of seconds and expands so violently that it triggers a small shock wave. This sudden boom is thunder, and can be heard some distance away. Unfortunately thunder always comes after a lightning strike, so it’s not a warning sign that lightning is coming, just that MORE lightning is coming.
So why can’t you always hear thunder when you see lightning? That, too, is fairly simple: the lightning storm is just too far away. Lightning strikes can be seen from miles away. Thunder, on the other hand, is a fairly immediate effect that travels in waves, and those sound waves will dissipate rather rapidly as they travel over space. If you’re too far away you’ll never hear the thunder.