The energy to bring about the tides id drained from....? What is losing energy.? Is this a perpetual machine?

Question

Thank you.... but I need more info... If the moon loses kinetic energy then surely it will coming closer to the earth?????

Answer 1

The source of this energy is the spinning motion of the earth (not gravitational or orbital kinetic energy, although of course gravity is the agent by which the process occurs).

The two tidal bulges on opposite sides of the earth act like two jaws of a wrench lightly gripping a rotating shaft and causing it to slow down with the energy being converted to heat and radiation. This is causing the day to gradually lengthen and if the only source of the tidal force were the moon, the end result would be that the length of the day would eventually slow down to match the length of the month (that is, the same side of the earth would always face the moon) and at that point there would be no more tides or tidal friction.

Part of the lost rotational energy of the earth goes into slightly accelerating the moon and pushing it gradually into a higher orbit. This is easily understood if you think of the wrench analogy. (In other words if the wrench gripping the shaft is allowed to move, part of the rotational energy will be transferred to the wrench (i.e. the moon) instead of being dissipated entirely as heat).

Answer 2

Tidal energy is supplied by the kinetic energy of the moon and earth orbiting each other. Since both bodies are fairly massive, they have a lot of kinetic energy. The moon moves farther away from the earth very slowly because of the energy lost from "tidal friction".

This is not a "perpetual machine" since eventually all the energy that creates the tides will be gone when the moon is far enough away a few billion years from now.

Answer 3

The tides are caused by the moon's gravitational pull on the oceans, so they move as the earth spins round. The vast amount of energy involved in this attractive force means it would only run out when, after billions or trillions of years, the moon stopped orbiting the earth and crashed into it. Long before this, the sun would flare up into a red giant and destroy earth.