I *belive* in what many of you wrote about the cause of the Earth-Moon
synchronization because I know that your contributions are based on
experience with reading and teaching the subject. But I am not totally
persuaded because I am not able to follow the details of the involved
logic. So I turned to Interactive Physics. It clearly tells me that
synchronization without tidal forces is possible. It is a spectacular
show; try it if you have this software tool. Here is what I did.
1) Normal Earth Moon simulation with realistic distances and realistic
masses using "planetary" gravity. Circles are bigger than they would
be if the proportionality could be respected. But this is not relevant;
each object is a point, as far as calculations are concerned. This is
just a warmup; nothing unusual. At time zero my moon is at the 3
o'clock position and i give it a vertical velocity of 1023 m/s. A
small initial velocity, downward, is given to Earth to make sure
that the linear momentum of the system is zero in the frame of my
screen. In this way circles do not drift out of my view.
2) Now comes the fun part. Moon is represented by two circles, left and
right (at the initial 3 o'clock position). Each of these circles is
an object whose mass is one half of Moon. Five rods are used to turn
this double-circled moon into a rigid body. The initial velocity of
this rigid moon is the same as for the single circle moon. This is
accomplished by assigning the initial vertical speed of 1023 m/s to
each half-moon. The half-moons are separated by a distance which is
only slightly larger, say 10%, than the sum of the two radii.
3) Watching this system to rotate, and to spin, is very instructive. Try
it, you will like it. Timing steps of my simulation were 200 seconds
but you can start with 2000 seconds to speed it up. The result will
be nearly the same. Tracking one out of 50 frames is appropriate to
start with; then change it as needed. I suggest you make one half-moon
slightly larger, or smaller, than another. This is only for displaying,
each half-moon is treated as a point object.Two sizes will help you
recognize interesting details, including very frustrated tendency
toward synchronization.
A "tidal torque", yes, but no traditional tides. That is how I see it.