Jim Fowler
@kisonecat.com
kisonecat.github.io/triangle-cen... lets you view a ton of triangle centers from faculty.evansville.edu/ck6/encyclop... all at once
September 17, 2025 at 11:59 PM
kisonecat.github.io/triangle-cen... lets you view a ton of triangle centers from faculty.evansville.edu/ck6/encyclop... all at once
My local movie theater is a member of NATO
July 30, 2025 at 2:53 PM
My local movie theater is a member of NATO
July 30, 2025 at 2:50 PM
"infinite possibilities" is a wonderfully optimistic tagline for apples
June 24, 2025 at 6:55 PM
"infinite possibilities" is a wonderfully optimistic tagline for apples
So the weight of the cars causes slight indentations where the wheels sit?
June 6, 2025 at 12:11 AM
So the weight of the cars causes slight indentations where the wheels sit?
high protein? i want high dimensional!
March 27, 2025 at 2:18 PM
high protein? i want high dimensional!
the Galilean moons of Jupiter! but as a cell phone camera image taken through a telescope.
February 26, 2025 at 1:40 PM
the Galilean moons of Jupiter! but as a cell phone camera image taken through a telescope.
Cat finds perfect spot
February 23, 2025 at 3:55 PM
Cat finds perfect spot
This piece of art in my house is called "the scream"
February 9, 2025 at 5:24 PM
This piece of art in my house is called "the scream"
Here's the third page from Born and Jordan's "Zur Quantenmechanik" in 𝘡. 𝘗𝘩𝘺𝘴𝘪𝘬 34, 858–888 (1925) introducing matrix mechanics.
Just 100 years ago, linear algebra was so unknown that the paper takes time to explain how to multiply matrices. And now matrices are everywhere!
Just 100 years ago, linear algebra was so unknown that the paper takes time to explain how to multiply matrices. And now matrices are everywhere!
![# Kapitel I. Matrizenrechnung
## § 1. Elementare Operationen. Funktionen
Wir rechnen mit quadratischen unendlichen Matrizen¹, die wir hier mit fetten Buchstaben bezeichnen wollen, während schwache Buchstaben stets gewöhnliche Zahlen bedeuten sollen:
\[
a = (a(n, m)) =
\begin{pmatrix}
a(0,0) & a(0,1) & a(0,2) & \cdots \\
a(1,0) & a(1,1) & a(1,2) & \cdots \\
a(2,0) & a(2,1) & a(2,2) & \cdots \\
\vdots & \vdots & \vdots & \ddots
\end{pmatrix}
\]
Gleichheit zweier Matrizen bedeutet Gleichheit entsprechender Komponenten:
\[
a = b \quad \text{heißt} \quad a(n, m) = b(n, m). \quad (1)
\]
Addition wird definiert durch Addition entsprechender Komponenten:
\[
a = b + c \quad \text{heißt} \quad a(n, m) = b(n, m) + c(n, m). \quad (2)
\]
Die Multiplikation wird definiert durch die aus der Determinantentheorie bekannte Regel „Zeilen mal Kolonnen“:
\[
a = b \cdot c \quad \text{heißt} \quad a(n, m) = \sum_{k=0}^{\infty} b(n, k) \cdot c(k, m). \quad (3)
\]
Potenzen sind durch wiederholte Multiplikation zu definieren. Es gilt das **assoziative Gesetz** für die Multiplikation und das **distributive Gesetz** für die Verbindung von Addition und Multiplikation:
\[
(a b) c = a (b c). \quad (4)
\]
\[
a (b + c) = a b + a c. \quad (5)
\]](https://cdn.bsky.app/img/feed_thumbnail/plain/did:plc:ldgfeud6f74qowuyfb4eksli/bafkreia5g7u3i6tzce5zd3xlq2bsqr3xq7iecz4kndufwanror26az7udy@jpeg)
February 1, 2025 at 7:47 PM
Here's the third page from Born and Jordan's "Zur Quantenmechanik" in 𝘡. 𝘗𝘩𝘺𝘴𝘪𝘬 34, 858–888 (1925) introducing matrix mechanics.
Just 100 years ago, linear algebra was so unknown that the paper takes time to explain how to multiply matrices. And now matrices are everywhere!
Just 100 years ago, linear algebra was so unknown that the paper takes time to explain how to multiply matrices. And now matrices are everywhere!
Here is a graph showing birthrate of Kilo's in Kilo/Hour.
February 1, 2025 at 3:30 PM
Here is a graph showing birthrate of Kilo's in Kilo/Hour.
I was excited to misread this as OULIPO soda -- a refreshing way to pursue constrained writing!
December 15, 2024 at 5:18 PM
I was excited to misread this as OULIPO soda -- a refreshing way to pursue constrained writing!
@adriansdigitalbasement.com since flexing the control board kept my furnace going... I just put a clamp on the PCB!
December 11, 2024 at 7:29 PM
@adriansdigitalbasement.com since flexing the control board kept my furnace going... I just put a clamp on the PCB!
I saw these dice at ISAC at UChicago; despite being super old (from Roman Egypt!) the dots on each face are displayed like today's dice, and the opposite sides sum to seven -- but the handedness of the dice aren't consistent!
December 2, 2024 at 2:31 PM
I saw these dice at ISAC at UChicago; despite being super old (from Roman Egypt!) the dots on each face are displayed like today's dice, and the opposite sides sum to seven -- but the handedness of the dice aren't consistent!
PSL ≅ Pumpkin Spice Latte ≅ Projective Special Linear
every year I hope Starbucks will emphasize more hyperbolic geometry
every year I hope Starbucks will emphasize more hyperbolic geometry
October 21, 2024 at 2:09 PM
PSL ≅ Pumpkin Spice Latte ≅ Projective Special Linear
every year I hope Starbucks will emphasize more hyperbolic geometry
every year I hope Starbucks will emphasize more hyperbolic geometry
10¢ is the same width as 45¢
October 21, 2024 at 2:01 PM
10¢ is the same width as 45¢
the diameter of a dime is 9 inches / √163
October 21, 2024 at 2:00 PM
the diameter of a dime is 9 inches / √163
Two great facts about 163.
October 21, 2024 at 1:59 PM
Two great facts about 163.