Date: 11 June 1981 0323-EDT (Thursday) From: Dan Hoey at CMU-10A To: Cube-Lovers at MIT-MC Subject: Re: edge "flip" anyone... Message-Id: <11Jun81 032344 DH51@CMU-10A> Does anyone know of a way to flip two edges without changing anything else, ie interchange the FR and FB edges, keeping their same orientation. The term "flip" generally means "change orientation" (of an edge). I take it you mean "exchange" (or, acceptably, "interchange"). This is provably not possible, because an exchange is an odd permutation. I will send you the two messages which deal with what can be done with a cube. (Anyone else who wants a copy, request of Hoey@CMU-10A rather than the list.) If you don't know what an even (or odd) permutation is, or how it acts, any elementary algebra text should help. If you try and fail, drop me a line and I'll try to help. If not, how about one that will interchange FR and FB edges without disturbing the top layer, but can mess up the bottom?? There is no FB edge. I'd guess you mean UR and UB, for which RU'R' UUFFBB DDFFBB RUR' suffices.