Theoretically, how can you remove friction between surfaces with air? I know that if there was a way to compress and control air (think air bender) then it can be used to remove friction between two surfaces. A person could just skate on their feet by focusing this compressed air between their feet and ground (kind of like an ice bender creating ice floor to skate).
I want to understand though, what underlying physics makes this possible? I'm guessing it is a combination of pressurized air filling-in/smoothing the roughness on ground, and thereby the reduction of friction.
Or is my initial hypothesis incorrect, and skating is impossible even if we could overcome the issue of controlling wind?
 A: You are describing an ideal scenario of two perfectly flat surfaces.
I have seen in real life with a basically perfectly polished flat granite stone on a perfectly polished granite table. With the stone on the table, you could not to the death of you push it down to touch. It would always hover slightly above the table without contact. It thus experienced a friction as low as I have ever seen - basically zero friction, or at only some miniscule fluid friction with the air - and would slide smoothly when pushed gently with a constant speed without slowing down. In fact, a corner of the stone was broken of from one evening when they had closed down the lab and left the stone on the table - it looked stationary but actually was slightly moving. And after several hours, it fell off the table. There was no friction to stop it.
The reason for the hovering is that the air in the gab between the two surface has nowhere to escape to. A moving air particle in the gab would leave behind a vacuum that immediately would suck in the neighbour air particle, thus never allowing for the air to disappear and for the surfaces to get any closer.
This works as long as the established vacuum is stronger than some treshold value of pressure on the surfaces. When you overcome this, then the air will finally be squeezed out and the surface will meet. And they will never be separated again, since that would create yet again a vacuum holding them strongly together.
