What causes Thunder?

Lightning does.In an instant, a bolt of lightning can heat the air around it up to  60,000 F . The heated air expands violently,  like an explosion. As the air expands it also cools quickly and starts to contract. This quick expansion and contraction air create the shock waves we hear as thunder.


Think of popping a balloon. When you blow it up, you are putting the air under pressure . Why? Because air molecules in the ballon are packed more tightly than they are in the air around it. The rubber keeps the air inside balloons from spreading out. When the balloon breaks, the air expands rapidly like the air superheated by lightning. The molecules from inside the balloon push against those on the outside creating shock wave that you hear as a pop". up. sound.