Another corner of Pennsylvania

A few months ago I noticed the banner image of Mastodon user @emacsomancer@types.pl: I had two questions about this. First where is it from and is there more? @emacsomancer pointed me to the source Github repository and also to this magnificent hand-lettered interpretation of it by artist Michał "phoe" Herda, who is also an author of books...

Last week I received a widely circulated email that began: With tall apartment buildings being erected all around, we feel it is ever more important to preserve our community. I sent this reply. I have been a Spruce Hill homeowner for 16 years. I had to miss the June 26 meeting because I was out of the country. But I think the historic...

Looking at license plates the other day I noticed that if you have a four-digit number with digits , and , then will always be a multiple of . For example, and . Mathematically this is uninteresting. The proof is completely trivial. (Such a number is simply , and .) But I thought that if someone had pointed this out to me when I was eight...

Toph and I were discussing the story of Loki and Skaði, one of my favorites. (Previously.) The Æsir have killed Skaði's father, and owe her compensation. She has been sad since her father died, she says, and demands that the Æsir make her laugh. Loki rubs his hands together and says "Leave this to me!". He takes a rope, ties one end to a...

Like almost everyone except Alexander Grothendieck, I understand things better with examples. For instance, how do you explain that $$(f\circ g)^{-1} = g^{-1} \circ f^{-1}?$$ Oh, that's easy. Let be putting on your shoes and be taking off your shoes. And let be putting on your socks and be taking off your socks. Now is putting on your...