From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.io/gmane.science.mathematics.categories/6197 Path: news.gmane.org!not-for-mail From: Vaughan Pratt Newsgroups: gmane.science.mathematics.categories Subject: Re: Illusion and Forthrightness in Wikipedia Date: Sun, 19 Sep 2010 15:07:00 -0700 Message-ID: References: Reply-To: Vaughan Pratt NNTP-Posting-Host: lo.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Trace: dough.gmane.org 1284998532 16429 80.91.229.12 (20 Sep 2010 16:02:12 GMT) X-Complaints-To: usenet@dough.gmane.org NNTP-Posting-Date: Mon, 20 Sep 2010 16:02:12 +0000 (UTC) To: categories Original-X-From: majordomo@mlist.mta.ca Mon Sep 20 18:02:11 2010 Return-path: Envelope-to: gsmc-categories@m.gmane.org Original-Received: from smtpx.mta.ca ([138.73.1.138]) by lo.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1Oxiok-0001NC-NO for gsmc-categories@m.gmane.org; Mon, 20 Sep 2010 18:02:11 +0200 Original-Received: from mlist.mta.ca ([138.73.1.63]:49530) by smtpx.mta.ca with esmtp (Exim 4.71) (envelope-from ) id 1Oxinq-0004rl-Hx; Mon, 20 Sep 2010 13:01:14 -0300 Original-Received: from majordomo by mlist.mta.ca with local (Exim 4.71) (envelope-from ) id 1Oxinj-0005QH-UT for categories-list@mlist.mta.ca; Mon, 20 Sep 2010 13:01:08 -0300 In-Reply-To: Precedence: bulk Xref: news.gmane.org gmane.science.mathematics.categories:6197 Archived-At: On 9/17/2010 11:58 PM, Fred E.J. Linton wrote: > Is it really informative to hide the fact that the color illustration > (at top) for the (3,7)-torus knot*is* using the parametrization that > the text displays, while the b/w (2,3)-torus knot (displayed next) is > using rather a*different* style of parametrization, whose details are > ... well, you see what I'm after? And if I change it, who next will > change it away again? At first I thought there must have been some race condition here, until=20 I transformed all times including those on Fred's email header into UTC=20 (Universal Coordinated Time). The relevant events in chronological=20 order are then 01:52, 14 September: User Selinger "clarified that images don't agree=20 with formula," by pointing out in the Wikipedia article that "Other=20 parametrizations are also possible, because knots are defined up to=20 continuous deformation. The illustrations on this page are derived from=20 various different parametrizations." 20:29, 17 September: User Vaughan Pratt "illustrated point about=20 different parametrizations" by appending to Peter's second sentence ": for example (leaving z unchanged) the (3,8)-torus knot uses r =3D=20 cos(q=CF=86) + 4 for a smoother effect while the (2,3)-torus knot avoids=20 inflexion points altogether by taking x + iy =3D r e^{p=CF=86i} =E2=88=92= 3 e^{=E2=88=92=CF=86i}=20 where r =3D cos(q=CF=86) =E2=88=92 4." 06:58, 18 September: Fred posted to the categories list as above, namely=20 that the 14 September edit was insufficient and that the (2,3)-torus=20 knot is using a different *style* of parametrization. Now Wikipedia edits are seen essentially instantaneously by all users.=20 Hence Fred must have based his complaint on the state of the article=20 10.5 hours before his post to this list, without checking whether the=20 current version still had that defect (e.g. by refreshing the page). Since x + iy =3D re^{p=CF=86i} =E2=88=92 3e^{=E2=88=92=CF=86i} is merely = the Euler-De Moivre=20 abbreviation for x =3D r cos(p=CF=86i) - 3 cos(=E2=88=92=CF=86i), y =3D r= sin(p=CF=86i) - 3=20 sin(=E2=88=92=CF=86i), I wouldn't call this a change in *style* from the = original=20 parametrization of x =3D r cos(p=CF=86i), y =3D r sin(p=CF=86i). (Now th= at I think of=20 it, the abbreviation is not short enough to offset the loss of clarity=20 so I unabbreviated it just now. All these changes can be tracked with=20 the article's history page, accessed via the History tab at the top.) Fred's variable-ellipse representation of the "aflective"=20 (inflexion-point-free) trefoil that he posted to this list the other day=20 is certainly a change in style, regardless of whether it's equivalent to=20 some version of the original style. But his claim that his is *the*=20 representation is called into question by the above parametrization,=20 which can be seen at http://boole.stanford.edu/Trefoil.jpg (actually I=20 changed it very slightly by decreasing "- 4" to "- 4.3", increasing "-=20 3" to "- 2.93", and rotating the figure 90 degrees clockwise, for a=20 closer match to the figure, but perhaps the figure should be changed=20 instead). But whether the Wikipedia figure is a better match to my parametrization=20 or to Fred's is I would say moot given that there is no need to change=20 parametrization *style* to get an aflective trefoil, as should be clear=20 from http://boole.stanford.edu/Trefoil.jpg . Even more puzzling to me is that prior to Fred's posting to this list on=20 this topic he had sent me 32 emails regarding his problem of drawing a=20 trefoil-shaped logo in Postscript, and I'd answered him 25 times, to his=20 complete satisfaction I thought. That he then turned to the categories=20 list for further help with trefoils would seem to indicate that I'd been=20 less helpful than I thought. I guess I can justify whatever he found=20 unhelpful with the observation that with free consulting you get what=20 you pay for. Vaughan Pratt [For admin and other information see: http://www.mta.ca/~cat-dist/ ]