*Boooom!*
The speed that Luan and Cristina flew in the flying cloud surpassed the speed of sound as they traveled through the air. Upon reaching such speed, they ran over the sound waves generated by themselves. The effect was a big shock wave, which caused a big bang.
Sound travels through waves, using air as a propagation medium. Such waves, called "pressure waves", develop in the same way as when we throw a rock into a lake: a circular wave forms at the point where the rock hits the lake and moves away, expanding at a constant speed.
If we throw several stones at the same point at regular intervals, we will form concentric waves – this is what happens with a sound emitter such as an airplane. The propagation speed of these waves is what we call the speed of sound.
