Dark Side of the moon-Tidal effect

When I was a child, my grand mother used to tell me, look at the moon, there is an old women who is weaving and I was like...'wow.. that's true'. Actually this image of old women  changes with region. In many places people think of a face of a man (fig. 01)  and a rabbit for many others places. It is only because the creative nature of humans. It changes from place to place.I used to stare at that old women frequently.

 

FIG. 01

As I go to higher standards of school, I was taught that moon is a celestial body which revolves around the earth with a period of  27 earth days. I also rotates around the axis which passes through its center and takes 29 days to do it. wait a minute....if moon rotates around its  axis then how it is possible that the old women doesn't go to opposite side of and a new face replace it. It was a kind of fascinating observation. then I started to find the reason behind it and I found.

                      The key thing is its orbital time period (27 days) and its period (29 days). This means moon takes approximately same time as it rotates around its axis and to revolve around earth. That's why only one side of the moon  faces earth. 

                      Let me make you more comfortable with the explanation. Take two balls,one as earth,BALL E and other as moon,BALL M. In the BALL M, mark a point,and make this point to face BALL E.Now try rotate the BALL M and simultaneously revolve it around the BALL E. Try to make their time period same. This is a very good method to understand what's going on. You can also understand it with following animation video.

                 

This phenomenon is not just  unique for earth-moon system. This has been observed in many planet-satellite system of solar system.for example Pluto-charon.This is called spin-orbit resonance phenomenon. Tidal torques from the planet and internal friction in the satellite is explained as the cause behind this.

Question is what would happen if this kind of phenomenon doesn't occur.From Newton's gravitational law we know that the part of moon which is nearer to planet will face more gravitational pull than the part away from the planet. So if moon doesn't show spin-orbit resonance, then all the parts of moon will face squeezing and expanding simultaneously. This will cause moon to be unstable.Sometimes it will break it apart. Saturn's ring are thought as debris of an ancient moon which was wrecked by Saturn's strong gravity.Now-a-days its moon ENCELADUS is being the victim of the tidal effect.( figure below)