Eventually, Bill Moore of EVWorld.com fame, asked, “Okay, someone explain the physics here. Newton’s 3rd law of action/reaction. Air being forced into umbrella is dispersed into a wider surface area then if he simply pointed the blower behind him?”
I was hoping that some smart person like Bill Moore would come along and notice that the laws of physics, specifically, Newton’s 3rd law of motion (for every action there is an equal and opposite reaction) makes this impossible; it’s staged.
Given this set-up, the guy would be actually be moving backward, because the thrust in reverse would be greater than forward. If he threw away the umbrella and aimed the leaf blower behind him, there would be some (extremely small) forward thrust.
Think about the jet engine. The airplane is propelled forward because mass is being shot out the back.