It's not cryptic. The video in post #1 makes the same exact point.

That's what I get for not watching silly videos till the end (the first part was silly -- I gave up).

PS -> I wanted to see the chick fall out of the box.

 

That's what I get for not watching silly videos till the end (the first part was silly -- I gave up).

OK, Never mind...

 

OK, Never mind...

Pretty much, yeah.

 

I remember reading somewhere that, in relativity theory due the effect on gravity by a rotating mass, if you had a large ring mass rotated at a sufficiently high speed, the center would have gravity cancelled, but I can't find any reference to that now.
Of course the amount of mass required, and the speed of rotation were way above anything that could be practically done.

One can locally (spatially or temporally) eliminate gravitation, people orbiting the earth are to all intents and purposes experiencing no gravity. Similarly, if one was in an elevator and the cable snapped and it fell freely, one would temporarily experience no gravity.

Einstein took this even further and said that such systems were experimentally indistinguishable (at least locally) from a genuine absence of gravitation, his so called principle of equivalence.

In a similar manner one can create gravity; acceleration feels like gravity, there is no difference, an experiment performed in a gravitational field yields identical results to experiments performed in an accelerated system (this is how Einstein inferred the bending of light around massive objects like stars).

 

people orbiting the earth are to all intents and purposes experiencing no gravity

No, if they were experiencing no gravity, they would fly off into space instead of orbiting. What they are experiencing is the same thing you would experience (briefly) if you jumped off a cliff. You are being accelerated by gravity, and therefore do not feel the force countering gravity that you do when standing on solid ground.