Tuesday, May 22, 2012

Included Middle

Filed under: General,Geometry — m759 @ 2:01 PM


"In logic, the law of excluded middle (or the principle of excluded middle) is the third of the so-called three classic laws of thought. It states that for any proposition, either that proposition is true, or its negation is.

The law is also known as the law (or principleof the excluded third (or of the excluded middle), or, in Latinprincipium tertii exclusi. Yet another Latin designation for this law is tertium non datur: 'no third (possibility) is given.'"

"Clowns to the left of me, jokers to the right"

 — Songwriter who died on January 4, 2011.

Online NY Times  on the date of the songwriter's death—

"A version of this review appeared in print
on January 4, 2011, on page C6 of the New York edition." 


"The philosopher Hubert Dreyfus and his former student
Sean Dorrance Kelly have a story to tell, and it is not
a pretty tale for us moderns. Ours is an age of nihilism,
they say, meaning not so much that we have nothing
in which to believe, but that we don’t know how to choose
among the various things to which we might commit
ourselves. Looking down from their perches at Berkeley
and Harvard, they see the 'human indecision that
plagues us all.'"

For an application of the excluded-middle law, see
Non-Euclidean Blocks and Deep Play.

Violators of the law may have trouble* distinguishing
between "Euclidean" and "non-Euclidean" phenomena
because their definition of the latter is too narrow,
based only on examples that are historically well known.

See the Non-Euclidean Blocks  footnote.

* Followers  of the excluded-middle law will avoid such
trouble by noting that "non-Euclidean" should mean
simply "not  Euclidean in some  way "— not  necessarily
in a way contradicting Euclid's parallel postulate.

But see Wikipedia's defense of the standard, illogical,
usage of the phrase "non-Euclidean."


Tertium Datur

Froebel's Third Gift

"Here I am, stuck in the middle with you."

Thursday, June 9, 2011

Page 679

Filed under: General,Geometry — Tags: — m759 @ 9:00 PM

Click to enlarge.


Good question. See also

Chern died on the evening of Friday, Dec. 3, 2004 (Chinese time).
From the morning of that day (also Chinese time)—
i.e. , the evening of the preceding day heresome poetry.

Friday, March 4, 2011

Ageometretos Medeis Eisito*

Filed under: General,Geometry — m759 @ 7:11 PM

Your mission, should you choose to accept it…

IMAGE- Future Bead Game Master Joseph Knecht's mission to a Benedictine monastery

See also "Mapping Music" from Harvard Magazine , Jan.-Feb. 2007—

"Life inside an orbifold is a non-Euclidean world"

— as well as the cover story "The Shape of Music" from Princeton Alumni Weekly ,
Feb. 9, 2011, and "Bead Game" + music in this  journal (click, then scroll down).
Those impressed by the phrase "non-Euclidean" may also enjoy
Non-Euclidean Blocks and Pilate Goes to Kindergarten.

The "Bead Game" + music search above includes, notably, a passage describing a
sort of non-Euclidean abacus in the classic 1943 story "Mimsy Were the Borogoves."
For a visually related experience, see the video "Chord Geometries Demo: Chopin
on a Mobius Strip" at a music.princeton.edu web page.

* Motto of the American Mathematical Society, said to be also the motto of Plato's Academy.

Saturday, July 24, 2010

Playing with Blocks

Filed under: General,Geometry — Tags: — m759 @ 12:00 PM

"Many of the finite simple groups can be described as symmetries of finite geometries, and it remains a hot topic in group theory to expand our knowledge of the Classification of Finite Simple Groups using finite geometry."

Finite geometry page at the Centre for the Mathematics of
   Symmetry and Computation at the University of Western Australia
   (Alice Devillers, John Bamberg, Gordon Royle)

For such symmetries, see Robert A. WIlson's recent book The Finite Simple Groups.

The finite simple groups are often described as the "building blocks" of finite group theory.

At least some of these building blocks have their own building blocks. See Non-Euclidean Blocks.

For instance, a set of 24 such blocks (or, more simply, 24 unit squares) appears in the Miracle Octad Generator (MOG) of R.T. Curtis, used in the study of the finite simple group M24.

(The octads  of the MOG illustrate yet another sort of mathematical blocks— those of a block design.)

Thursday, July 22, 2010

Pilate Goes to Kindergarten, continued

Filed under: General,Geometry — m759 @ 2:02 PM

Barnes & Noble has an informative new review today of the recent Galois book Duel at Dawn.

It begins…

"In 1820, the Hungarian noble Farkas Bolyai wrote an impassioned cautionary letter to his son Janos:

'I know this way to the very end. I have traversed this bottomless night, which extinguished all light and joy in my life… It can deprive you of your leisure, your health, your peace of mind, and your entire happiness… I turned back when I saw that no man can reach the bottom of this night. I turned back unconsoled, pitying myself and all mankind. Learn from my example…'

Bolyai wasn't warning his son off gambling, or poetry, or a poorly chosen love affair. He was trying to keep him away from non-Euclidean geometry."

For a less dark view (obtained by simply redefining "non-Euclidean" in a more logical way*) see Non-Euclidean Blocks and Finite Geometry and Physical Space.

* Finite  geometry is not  Euclidean geometry— and is, therefore, non-Euclidean
  in the strictest sense (though not according to popular usage), simply because
  Euclidean  geometry has infinitely many points, and a finite  geometry does not.
  (This more logical definition of "non-Euclidean" seems to be shared by
  at least one other person.)

  And some  finite geometries are non-Euclidean in the popular-usage sense,
  related to Euclid's parallel postulate.

  The seven-point Fano plane has, for instance, been called
  "a non-Euclidean geometry" not because it is finite
  (though that reason would suffice), but because it has no parallel lines.

  (See the finite geometry page at the Centre for the Mathematics
   of Symmetry and Computation at the University of Western Australia.)

Friday, February 19, 2010

Mimzy vs. Mimsy

Filed under: General,Geometry — Tags: — m759 @ 11:00 AM


Deep Play:

Mimzy vs. Mimsy

From a 2007 film, "The Last Mimzy," based on
the classic 1943 story by Lewis Padgett
  "Mimsy Were the Borogoves"–


As the above mandala pictures show,
the film incorporates many New Age fashions.

The original story does not.

A more realistic version of the story
might replace the mandalas with
the following illustrations–

The Eightfold Cube and a related page from a 1906 edition of 'Paradise of Childhood'

Click to enlarge.

For a commentary, see "Non-Euclidean Blocks."

(Here "non-Euclidean" means simply
other than  Euclidean. It does not imply any
  violation of Euclid's parallel postulate.)

Saturday, December 12, 2009

For Sinatra’s Birthday

Filed under: General,Geometry — m759 @ 2:02 PM

Today's previous entry quoted a review by Edward Rothstein of Jung's The Red Book. The entry you are now reading quotes a review by Jim Holt of a notable book by Rothstein:

The Golden Book

Rothstein's 'Emblems of Mind,' 1995, cover illustrations by Pinturicchio from Vatican

Cover illustration— Arithmetic and Music,
Borgia Apartments, The Vatican

Jim Holt reviewing Edward Rothstein's Emblems of Mind: The Inner Life of Music and Mathematics in The New Yorker of June 5, 1995:


"The fugues of Bach, the symphonies of Haydn, the sonatas of Mozart: these were explorations of ideal form, unprofaned by extramusical associations. Such 'absolute music,' as it came to be called, had sloughed off its motley cultural trappings. It had got in touch with its essence. Which is why, as Walter Pater famously put it, 'all art constantly aspires towards the condition of music.'

The only art that can rival music for sheer etheriality is mathematics. A century or so after the advent of absolute music, mathematics also succeeded in detaching itself from the world. The decisive event was the invention of strange, non-Euclidean geometries, which put paid to the notion that the mathematician was exclusively, or even primarily, concerned with the scientific universe. 'Pure' mathematics came to be seen by those who practiced it as a free invention of the imagination, gloriously indifferent to practical affairs– a quest for beauty as well as truth."

Related material: Hardy's Apology, Non-Euclidean Blocks, and The Story Theory of Truth.

See also Holt on music and emotion:


"Music does model… our emotional life… although
  the methods by which it does so are 'puzzling.'"

Also puzzling: 2010 AMS Notices.

Thursday, October 22, 2009

Chinese Cubes

Filed under: General,Geometry — m759 @ 12:00 AM

From the Bulletin of the American Mathematical Society, Jan. 26, 2005:

What is known about unit cubes
by Chuanming Zong, Peking University

Abstract: Unit cubes, from any point of view, are among the simplest and the most important objects in n-dimensional Euclidean space. In fact, as one will see from this survey, they are not simple at all….

From Log24, now:

What is known about the 4×4×4 cube
by Steven H. Cullinane, unaffiliated

Abstract: The 4×4×4 cube, from one point of view, is among the simplest and the most important objects in n-dimensional binary space. In fact, as one will see from the links below, it is not simple at all.

Solomon’s Cube

The Klein Correspondence, Penrose Space-Time, and a Finite Model

Non-Euclidean Blocks

Geometry of the I Ching

Related material:

Monday’s entry Just Say NO and a poem by Stevens,

The Well Dressed Man with a Beard.”

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