On Fri, Mar 10, 2006 at 09:43:37AM -0000, Kelvin Cracknell wrote:
> the method you discribed may be fast but you are still effectivly
> performing two moves at once... two face rotations and an orientation
Right, Rubik's cube allows for simultaneous movements along parallel
planes. On a 20x20x20 cube, we could theoretically perform 19 movements
simultaneously (if we had enough hands/fingers) since there are 19
parallel "cut planes" along any axis. 19 simultaneous movements could
be performed in the same time as 1 simple move, but would also require
exerting 19 times more force.
We do not normally think of a cube rotation (orientation as you call it)
as a move. One explanation is that it involves zero cut planes. The move
you describe can be described as two simultaneous movements without any
need for a cube rotation, i.e. r' for the first cut plane, and R for the
second cut plane, performed simultaneously.
I wouldn't say that methods involving such movements are "incorrectly
modelled", however. It is very practical in the description of those
methods to describe such movements as single moves rather than two
simultaneous moves. Edges last methods tend to keep corners fixed, and
move the edges around independently through the middle slices (using
"slice" moves). The other kinds of simultaneous movements that are
possible on a Rubik's cube (e.g. "anti-slice" moves) are not so common,
and I don't know of any standard metric that counts them as one move
(even though they are often just as easy to perform as other kinds of
simultaneous movement, e.g. r2'R as a simultaneous movement).
Ryan
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