Furthermore, isn't the tidal forces from the moon at least part of the reason that the earth's core is *still* spinning?
The reason I bring this up is because, to our knowledge, Venus never had a moon.
Nope. Actually the moon's tidal effects act to
reduce the spin rate. Since the Earth spins faster than the moon orbits, the tidal bulge that the moon raises on the earth leads the moon slightly in its orbit. The moon pulls on this bulge and thus causes a drag that acts to slow the earth's rotation. This rate is about 2x10
-5 seconds per year.
This is for the earth at large, but the Earth's core's rotation rate is almost identical (
1° per million years according to this study), so if the core has a similar tidal bulge then the effect would still be that of a spining-down.
A moon
can cause the planets rotation to speed up, however, if the orbital period is faster than the rotation period, like in the case of Mars' moon Phobos. Phobos is much too small to have any significant tidal effect on Mars, though.
