Some more thoughts on the Can-A-Plane-Take-Off-From-A-Conveyer-Belt Conundrum (I considered just updating the original post, but this issue is too damned important):
o I like Anders' summation of the conveyer belt as no more consequential then a gremlin spinning the wheels of a plane hovering above the conveyer belt.
o The jet engines are exerting a force on the plane to move it forward, and that force is not being transferred or dissipated anywhere, unless you believe that the freely spinning wheels are transferring it to the conveyer belt, which I can't buy. So according to my rudimentary understanding of mechanics, the plane has to move forward.
o Alternate Scenario #1: Imagine a giant hovering in midair and pushing the plane forward with the same amount of force as its engines (which are turned off). Would the plane move forward? If so, how is this different from if the jet engines are supplying that force?
o Alternative Scenario #2: You're standing on a miniature version of the conveyer belt, wearing well-oiled roller skates and a jetpack which thrusts horizontally. Assuming you have superhuman balance, would you move forward, or would you just stand still while the skates and the treadmill spun furiously?