From cbmvax!uunet!CUVMA.BITNET!LOJBAN Fri Mar 13 12:44:32 1992 Return-Path: Received: by snark.thyrsus.com (/\==/\ Smail3.1.21.1 #21.19) id ; Fri, 13 Mar 92 12:44 EST Received: by cbmvax.cbm.commodore.com (5.57/UUCP-Project/Commodore 2/8/91) id AA01585; Fri, 13 Mar 92 12:05:55 EST Received: from pucc.Princeton.EDU by relay2.UU.NET with SMTP (5.61/UUNET-internet-primary) id AA18098; Fri, 13 Mar 92 09:25:04 -0500 Message-Id: <9203131425.AA18098@relay2.UU.NET> Received: from PUCC.PRINCETON.EDU by pucc.Princeton.EDU (IBM VM SMTP V2R2) with BSMTP id 1774; Fri, 13 Mar 92 09:09:55 EST Received: by PUCC (Mailer R2.08 PTF011) id 9313; Fri, 13 Mar 92 09:08:12 EST Date: Fri, 13 Mar 1992 09:07:17 -0500 Reply-To: "Mark E. Shoulson" Sender: Lojban list From: "Mark E. Shoulson" Subject: Necker Cube X-To: lojban@cuvmb.cc.columbia.edu To: John Cowan , Eric Raymond , Eric Tiedemann In-Reply-To: Ivan A Derzhanski's message of Fri, 13 Mar 1992 08:41:32 GMT Status: RO I write, after drawing an ambiguous picture: > Well, you get the picture. Those two spots where the two squares intersect > are ambiguous, in that you don't know which line is in front, and that > means you don't know which square is in front. If you draw it so you can > tell, but with the disambiguation in an impossible fashion, you get the > famous irrational cube (q.v. various Escher prints. _Belvedere_ is a good > example, as the guy in the dungeon is holding an irrational cube and > there's a picture of a Necker Cube on the floor with the key intersections > circled). To which Ivan responds: >Haud a wee. If I remember correctly, the cube in _Belvedere_ is not >an ambiguous one, because you can tell which line is which, only they >go in a way that makes it impossible for the cube to exist in real >life, like so: [picture of irrational cube] Yes, Ivan, the cube the guy is holding isn't ambiguous, just impossible. But that wasn't the one I said was ambiguous. On the ground in _Belvedere_, in front of the dungeon window there's a scrap of paper on which is drawn the Necker cube, all ambiguous, with the interesection points circled. 'Course, the building in _Belvedere_ is irrational, too. ~mark, the Escher fan.