[thulldud]

OK, I remember the concept now. The energy to boost the moon into higher orbit is supplied by the earth's rotation, which is slowing down. It is a simple transer of energy, not magic. So now some genius needs to answer the question -- will tapping the tidal energy increase or diminish this effect?

Offhand, I would expect that it would reduce the tidal effect on the moon, since you would be bleeding the energy pipeline like this:

Earth's angular momentum -> seawater bulge -> Moon

Earth's angular momentum -> turbine -> seawater bulge -> Moon

The tidal effect on Earth (slowing its rotation) would be much less affected. Earth would still be slowed by the tides, but less of that energy would be transmitted to the Moon because the tidal bulges can't rise as fast as before.

Of course, the difference probably would not be measurable by any instruments in existence today.

[non-anonymous]

Read my post #74.

Ideally, tides make the Earth look like an ellipse, with the major axis pointing directly at the moon. The Earth's rotation causes the material in the bulge to rotate away from this axis, and the tidal effect affects the non-bulge material moving into the axis. Therefore, you get a "standing wave" which is directly below and ahead of the moon, which exerts more force on the Moon because it is closer.

It's the internal friction and angular momentum of the material in the Earth which causes this lag. An all-water planet should have less lag than an all-rock one, simply because material can more easily flow into the bulge. By that analogy, if you restricted the movement of the water, it would be less "fluid", and increase the overall tidal lag, therefore increasing the overall effect.

A lot of orbital/rotational energy goes into internal heating of both Earth and Moon.