November 2016 - mathfun@mailman.xmission.com

Re: [math-fun] Sorry to be so uniformly dense,
by Dan Asimov 06 Nov '16

06 Nov '16

The center of mass has to be invariant under symmetries, and both mass distributions have symmetry group equal to the symmetric group on the vertices. Taking the n-simplex to be the convex hull of the standard basis of R^(n+1): {(x_j) in R^(n+1) | Sum x_j = 1, 0 <= x_j <= 1} , there is only one point invariant under its symmetries, i.e., permutations of coordinates, namely x_j = 1/(n+1) all j. —Dan ----- From: Bill Gosper <billgosper(a)gmail.com> Sent: Nov 6, 2016 12:41 PM but is it obvious why the center of mass of such a simplex is the center of mass of unit masses at its vertices? -----

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[math-fun] Sorry to be so uniformly dense,
by Bill Gosper 06 Nov '16

06 Nov '16

but is it obvious why the center of mass of such a simplex is the center of mass of unit masses at its vertices? --rwg

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[math-fun] Dump time zones in favor of UTC everywhere?
by Dan Asimov 06 Nov '16

06 Nov '16

James Gleick argues that we should: http://www.nytimes.com/2016/11/06/opinion/sunday/time-to-dump-time-zones.ht…. —Dan

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Re: [math-fun] Sorta math, sorta fun
by Dan Asimov 05 Nov '16

05 Nov '16

Nice! Which reminds me of a puzzle made up by my father when he was a kid: If the centipede a pint and the quadruped a quart, how much did the precipice? —Dan -----Original Message----- >From: David Wilson <davidwwilson(a)comcast.net> >Sent: Nov 5, 2016 11:14 AM >To: 'math-fun' <math-fun(a)mailman.xmission.com> >Subject: [math-fun] Sorta math, sorta fun > >An English cat name One-Two-Three challenged a French cat named >Un-Deux-Trois to a swimming race across the English Channel. Which cat won? > >Spoiler below.. >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >One-Two-Three won the race, because the Un-Deux-Trois cat sank. > > > >_______________________________________________ >math-fun mailing list >math-fun(a)mailman.xmission.com >https://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun

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[math-fun] Sorta math, sorta fun
by David Wilson 05 Nov '16

05 Nov '16

An English cat name One-Two-Three challenged a French cat named Un-Deux-Trois to a swimming race across the English Channel. Which cat won? Spoiler below.. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > One-Two-Three won the race, because the Un-Deux-Trois cat sank.

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[math-fun] Not particularly math, possibly fun, particularly particles
by Mike Speciner 05 Nov '16

05 Nov '16

https://ms0.github.io/gas.html

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[math-fun] Online Godel sentence?
by James Propp 04 Nov '16

04 Nov '16

I've heard it asserted that a Godel sentence, expressed in Peano arithmetic, would be long enough to fill a book. Sure, nobody would want to write such a book, but a computer could be programmed to do the job! Has anyone done this? Is there a Godel sentence on the web that I could include a link to in my next blog post? Thanks, Jim Propp

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