What catches my attention in this photo, after the blue and white squares, is how the beams slowly bend away from center. I suppose knowing the size of those beams, and some trigonometry, would allow you estimate the location of the camera.

**Appreciation**category.

## Ceilings of Curvature

On a visit to the Lowline, I noticed an interesting application of mathematics above us.

The ceiling is a tiling of hexagons and equilateral triangles. But unlike a typical tiling of a flat bathroom floor, this tiling seems to create a curved surface! Here’s a closer look:

The underlying pattern is hexagonal, but when a hexagon is replaced with six small, hinged equilateral triangles, the surface gains the potential to curve.

It’s interesting to follow the “straight” line paths as they curve over the surface. And since this tiling is suspended from above, it’s interesting to think about what the surface would look like if it were lying on the ground. How “flat” would it be? Or a better question might be “How *far *from flat is it?”

## 02/17/2017 — Happy Permutation Day!

Today we celebrate a Permutation Day! I call days like today permutation days because the digits of the day and the month can be rearranged to form the year.

We can also consider today a Transposition Day, as we need only a single transposition (an exchange of two numbers) to turn the year into the day and date.

Celebrate Permutation Day by mixing things up! Try doing things in a different order today. Just remember, for some operations, order definitely matters!

## 01/27/2017 — Happy Permutation Day!

Today we celebrate the first Permutation Day of the year! I call days like today *permutation days* because the digits of the day and the month can be rearranged to form the year.

Celebrate Permutation Day by mixing things up! Try doing things in a different order today. Just remember, for some operations, order definitely matters!

## 12/06/2016 — Happy Permutation Day!

Today we celebrate the final Permutation Day of the year! I call days like today *permutation days* because the digits of the day and the month can be rearranged to form the year.

Celebrate Permutation Day by mixing things up! Try doing things in a different order today. Just remember, for some operations, order definitely matters!