Computerizin
Celestial sphere I saw this picture on Wikipedia the other day. , via Wikimedia Commons" href="https://commons.wikimedia.org/wiki/File:Meteor_shower_in_the_Chilean_Desert_(annotated)_(potw2227b).jpg"> ESO/P. Horalek , CC BY 4.0 , via Wikimedia Commons It struck me that the ecliptic is almost vertical in this picture, super close to the zenith. I've always lived in the 51°N-53°N range where the…
Meeting points I grew up in a small town (an ex-shtetl, actually) and lived very close to all of my friends. We had a few classic meet-up points and we'd sometimes discuss the "best" meeting point: the most fair place to meet given our individual starting points. This exact scenario came up again recently, so I decided to attack it head on this time. I had an inkling that there wouldn't…
Simplest Estimate of Minimum Size of Bomb In Part 1 I covered the first few sections of the Los Alamos Primer: energy release, cross-sections, and why ordinary uranium can't sustain a chain reaction. This post picks up where we left off - figuring out how big a lump of fissile material needs to be before it goes critical. We will model neutron transport as a diffusion process and solve for the…
Background In my last post we worked through a probability problem under heavy duress. Three points chosen uniformly at random from a unit disk - what's the probability their circumcircle fits inside? After pages of Jacobians, angular integrals, and trig identities, I arrived at P = 2 / 5 . But I ended the post with some uncertainty: You wonder if you actually got the right answer. It was a nice…
Trouble in the alley You're walking alone through a dark alley in the middle of the night [1] when a hooded figure stops you. They tell you: "Solve the following mathematical problem right now OR I WILL SHOOT YOU DEAD.". They give you a piece of paper with the problem statement. Three points are chosen independently and uniformly at random from the interior of a unit circle. What is the…
In logic puzzles, lies can be more useful than truth. That sounds backwards. In everyday life lies obscure things. In formal logic, though, a false statement can be much more constraining than a true one. Knights and Knaves puzzles are a neat playground for seeing this happen in real time. I'm writing this as someone who enjoys these puzzles, not as a logician - corrections welcome. The rules…
Mounting a WSL2 disk If you used WSL2 and wrote some code, here’s how to get your files back on Linux. What you're dealing with WSL2 isn’t the lightweight syscall translation layer that WSL1 used. Instead, it runs a full Linux kernel in a lightweight VM using Microsoft's hypervisor. This means your Linux distro’s files live inside a VHDX disk image, not directly on the Windows filesystem. This…
KDE Top Bar and Emacs I ran into a mildly annoying issue with KDE’s taskbar. I keep a few apps pinned - Firefox, Emacs, Teams, and others - and the order matters because I switch between them using keyboard shortcuts like Meta+1, Meta+2, etc. KDE couldn’t reliably decide whether it should treat emacs and emacsclient as the same application. As a result, pressing Meta+2 might: Launch a new Emacs…
Part 1 I recently watched a lecture on how nuclear weapons are designed . It mentioned a few reading recommendations for anyone wanting to learn more, and one of those was The Los Alamos Primer . The primer itself is interesting for several reasons: it’s pretty old (mid 1940s old) and it’s based on five lectures Robert Serber gave in early 1943. If you open it up, you’ll see it’s very direct and…