system
Given the following post, respond as if you're commenting on Reddit:
human
Why is the sound barrier an aerodynamic problem?

Vibrations we pick up as sound can only move so quickly through a fluid (air). Fair enough. But why does aerodynamics get so tricky at that same speed? Why is it difficult for physical objects to exceed? Why did transonic speed cause such odd control difficulties for old aircraft? Why is the sound barrier a barrier for more than just sound?
gpt
Remember that the speed of sound isn't just the speed of waves, but the maximum speed at which any sort of information can be transmitted through the medium. This means that when flying at a subsonic speed, the air at the front of the wing "knows" (i.e. is capable of reacting to) what is happening to the air a bit further behind it, because the information (via sound waves) is able to arrive a bit earlier than the plane does. This allows everything to run more smoothly, in a certain sense. The air has a chance to move a bit to prepare for the plane to pass through.

On the other hand, when going supersonic, the air doesn't "know" that there's a plane coming until its too late and the plane is here - it can't, in principle, get advanced warning from the air nearby, and so you'd expect the equations to be completely different.