Quote:
Originally Posted by mithrandir
If the die is not rotating once per orbit, it can not always show the 6 face to all observers on the ground.
Suppose the die was not rotating, so one of the faces always pointed at say SXDF-XCLJ0218-0510 - the most distant known galaxy as at May 10 2010. From earth it would appear to be tumbling.
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This is precisely why I said earlier that this is a composite of motions. There is a spin, but it is an
apparent spin. This is actually a 'Parallel Transfer' of a body, within a geodesic, around a central mass; like a race track within a gravitational field where the outer wheels must cover a greater distance than the inside wheels; there is a consequence. The Moons spin comes as a direct relationship between it's orbital velocity and the field. The Tidal Lock is probably a feature of how the two fields (Moon and Earth) interact together.
The spin of the Die is attributed to it's orbit around the Earth, but the reason why the Die will always face the Earth (if positioned that way and left untouched) comes down to General Relativity...you see the space and time in which the Die is positioned within the geodesic pathway contains conservation of angular momentum (all laws actually) BUT, the geodesic is a curved path around the Earth, so the space spins around the Earth, not the Die (the space is bent to conform with the filed curvature)...this also means that the 6 face is being compressed and the outside face (opposite to the 6) is being stretched...the gravitational field is trying to turn it into a pie wedge. As the Die orbits the Earth the space which it occupies is rotated in sync with the curvature, so the Die isn't spinning, the space and time which the Die occupies is being warped, the net affect being tidal forces acting upon the Die and a change to the Die's orientation without any effort at all. This is also why satellite moons get crushed in orbit around gas giants to form rings of dust.
A Tidal Lock seems to be both a conservation tendency and a warping issue.
So is the Moon spinning???
I believe it has an apparent spin, but it is also stationary within the gravitational field.