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No, Earnshaw's theorem applies to statics. It doesn't apply to a dynamical equilibrium.


For the Apollo to orbit the Moon, a capture maneuver had to be performed at arrival, to change from the trans-lunar trajectory to an orbit around the Moon. This maneuver had to be performed in the opposite side of the Moon, without possibility of communications with the Earth. If a minimum energy trans-lunar trajectory was used, in the case of capture ...


The principle of conservation of energy is that energy is allowed to change forms. The gravitational energy being depleted due to friction (and presumably converted into heat in your rubbing analogy) is precisely this principle.


Conceptually the answer is simple- the heat energy created by the frictional effects associated with tides is offset by a loss of rotational energy, as the friction slows the rotation of the Earth. The impact on day-length is small, but will eventually cause the rotation to reduce to the point at which the day length equals the period of orbit of the moon.


Considering the interaction of the tidal bulge with the kinetic and potential energy compartments in the earth-moon system, how can we understand/rationalize these transfers of energies as obeying the conservation of energy? The moon creates a tidal bulge on the earth which drags across the ocean floor. Tidal friction between the flowing bulge and ...


Energy for tides comes from the Earth's rotation. Tidal drag is actually slowing Earth's rotation, making the days longer, but very gradually. Just as the Moon is tidally locked to Earth, Earth would eventually become tidally locked to the Moon, but it would take billions of years. As Earth spins much ...

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