So, I’m aware that tides are caused by the Moon’s gravity acting on the surface of the earth. That said, tidal forces move an obscene amount of matter from point A to point B and back to point A again. Where does that energy come from that doesn’t break the first law of thermodynamics? Followup question: If we harvest energy from the system using turbines or something similar, what effect does that have on the system?
In: Physics
The energy comes from kinetic energy in the earth’s rotation. A day 600 million years ago was 21 hours long.
The current slowdown is that a day gets shorter by 1.7 milliseconds per century, so it is not a lot on the time scale we are used to but a lot on earth’s geological time scale.
The same has occurred for the moon but faster because it is smaller then earth. The moon has slowed down so only one side point to earth. That mean the orbital time is the same as the rotational time. This is called today locking and why we can only see one side of the moon.
If left undisturbed earth would become today locked with the moon. It would take around 50 billion years and the rotation time for earth would be 47 current days.
The problem is that our sun will expand to a red giant in roughly 5 billion years. It will expand and might swallow the earth and the moon, Venus will certainly be swallowed. So if the earth and the moon survive the surfaces will have been remelted and the lightest molecule like water would be below away, So the earth will no longer support life.
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