CURRENT MOON
phases of the moon
EyeLovePi

Sam Harris, on Paying Attention

Source:  Waking Up: A Guide to Spirituality Without Religion, p. 3.

Comments

Four-Part Compound of Thin Parallelopipeds

I made this using Stella 4d:  Polyhedron Navigator. You may try this program for free at…

Comments

Quadrilaterals with Perpendicular Diagonals

I just learned these things are officially called orthodiagonal quadrilaterals. I’ve been calling them Qw⊥Ds (pronounced “quids”) for years, have studied their properties, and have even tested students’ knowledge of Qw⊥D esoterica.

orthodiagonal quadrilateralsObviously, on grounds of symmetry alone, it is easy to determine that Qw⊥Ds include all squares. With congruent triangles, it is also possible to prove that all…

View On WordPress

Comments

More Polyhedra, Including Some Compounds, from the Stellation-Series of the Tetrakis Cube

Tetrakishexa stellation

The next one is a compound of eight off-center pyramids. By this point, I had gone so far into the stellation-series (a search I began when preparing the post before this one) that I had lost count.

compound of eight off-center pyramids

View On WordPress

Comments

Two Compounds of Dipyramids from the Stellation-Series of the Tetrakis Cube

Two #Compounds of #Dipyramids from the #Stellation-Series of the Tetrakis Cube #polyhedra #geometry #mathematics

The 16th stellation of the tetrakis cube, the dual of the truncated octahedron, is a compound of three elongated octahedra, or square dipyramids:

Tetrakishexa

The 65th stellation of this same polyhedron is of another compound of dipyramids, but these are triangular dipyramids with obtuse faces, and there are four of them:

Tetrakishexa stellation 4

I generated both of these images with Stella 4d:  Polyhedron Navigator, available right

View On WordPress

Comments

Two Dodecahedra with Varying Rotation-Types Shows On Their Faces

The images shown on the faces of these dodecahedra appeared in the last post, and were made using Geometer’s Sketchpad and MS-Paint.

DodecaAssembling the polyhedral images and creating these rotating .gif files required another program, Stella 4d, which is available at http://www.software3d.com/Stella.php.

Dodeca2

View On WordPress

Comments
Comments

The Many Wars of the United States of America, in Our Brief History: a Timeline

Because it was, in some ways, a precursor to the American Revolutionary War, this timeline begins with the pre-American-independence French and Indian War. American independence was formally declared during the Revolutionary War, in 1776.

war1Light blue areas are for pre-American involvement in wars which ultimately ended in some form of victory for the USA, with dark blue areas representing American…

View On WordPress

Comments

This #SpaceStation for #Geometricians Has, as Outer Hulls, Twelve #Trapezoids, and Six #Parallelograms with One Square Window / Docking Port Each.

I can’t think of any good reasons for geometricans not to have their own space station, and I know what we’d do there:  we’d work on geometry (also known informally as “playing with shapes”).

Comments

Where Are This Blog’s Readers?

More hits come to this blog from inside the USA than any other country. Considering that I live here, that isn’t surprising. However, my international readers do outnumber what are confusingly called “Americans,” at 54.7% to 43.7% of hits to this blog.

1

When the hits from outside the U.S.A. are considered at as a set, a slim majority of that set is held by six nations, each with over 1,000 hits.…

View On WordPress

Comments
+ Load More Posts