I've had similar airplay flakiness. I can usually fix the issue by toggling AirPlay off and on, but I've also had to reset the Apple TV.

AirPlay on Apple TV 2 failing more often than it works
Liquid helium (and other similar fluids) can "climb up" the walls of their containers. Who does the work in this case, and what kind of energy does it use? I'm sure we can't make a perpetuum mobile out of this, so I guess some kind of energy must somehow be expended to make the fluid "climb up" the wall.
