Big try at gravity wheel

[TinselKoala]

But that silly Floating Point got you, too. One of yours seems to have floated away.

...fusing 600 million tons of hydrogen into 596 tons of helium. 

That's even better than Rossi is doing!

[lumen]

The useful work that can be extracted from gravity here on earth is in tidal power harvesting.  The relative movement of the moon cyclically pulls on the enormous volume and mass of the seas.  Harvesting the tides would only very slightly slow down the rotation of the moon around the earth.

I'm not sure about this, but if the moon rotates prograde and slower than the earths rotation, then wouldn't any additional connection of energy from the earth to the moon tend to accelerate the moon while slowing the earths rotation?

[MarkE]

It slows them relative to each other.  In terms of an external reference like the sun or some distant point in the cosmos, the earth will be seen to slow but only by a small fraction of the percentage that the moon slows.

[Marsing]

The useful work that can be extracted from gravity here on earth is in tidal power harvesting.  The relative movement of the moon cyclically pulls on the enormous volume and mass of the seas.  Harvesting the tides would only very slightly slow down the rotation of the moon around the earth.

sounds good, you have admitted that there is usefull energy from gravity.   

[lumen]

It slows them relative to each other.  In terms of an external reference like the sun or some distant point in the cosmos, the earth will be seen to slow but only by a small fraction of the percentage that the moon slows.

They would slow relative to each other seems correct.

From an external point, the earth's rotation would slow and the moon would accelerate as is already the case. I believe the moon's orbit radius in constantly increasing already from the tidal drag pulling the moon faster.  (slower from earth's view point)