From: roger.broadie@iclweb.com (Roger Broadie) To: "Nichael Cramer" Cc: Subject: Re: 4x4x4 solution Date: Thu, 2 Oct 1997 23:12:39 +0100 > From: Nichael Cramer > To: Roger Broadie > Cc: Cube-Lovers@ai.mit.edu > Subject: Re: 4x4x4 solution > Date: 2 October 1997 4:26 > > As one of the folks who advocated rotating a center slice, let me > explain my (admittedly non-optimal) process for getting out of this > fix and perhaps you can explain where my reasoning is wrong. >[followed by a procedure in which a quarter turn of a centre slice is followed, first, by a 3-cycle of edges on the top to restore the two swapped pieces, second, by a 3-cycle of edges to restore the other displaced edges, and, third, by restoring the displaced centres] I absolutely agree with your reasoning. A quarter turn of a central slice must be at the heart of any procedure to perform an edge swap, because it is the only way to change the parity of the edges. That was what I said in my first post on 1 October 1997. In my second post I was trying to look at the effect of that quarter turn of the central slice on the centre pieces, and show that, as they had been subjected to an even permutation by reason of the centre-slice turn, the centre pieces could not have undergone an invisible swap of a single pair of centre pieces. Having made a single quarter turn of the central slice, all the other edge and centre pieces can be restored with processes of even parity, like your two 3-cycles. Roger Broadie ------------------------------ End of Cube-Lovers Digest *************************