(at 2:32...) Wait a minute... if a shock wave can travel through a gaseous medium at "faster than the speed of sound" (2:14). then can shock waves travel upstream through the choked flow in the throat of a De Laval nozzle? And if so, doesn't that seriously undermine the premise that "downstream state information can not flow upstream faster than the speed of sound, so the flow characteristics of a C-D nozzle in choked flow are determined solely by upstream conditions"? OK.. I get it that the shock wave wouldn't carry information about the "unshocked" downstream state, only about itself - and that these would be highly random, disordered, chaotic conditions. And I'll bet that a later module here (maybe later in this module), you'll explain how shockwaves can be disruptive, possibly even destructive phenomena if they occur within C-D nozzles or scramjets. I'll just sit back and watch for that... Still, it's a bit puzzling to think of a "sound" travelling faster than sound....
