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Shows up when trying to solve 2D wave equation on a circular domain in polar coordinates with separation of variables, where we have to decompose the initial condition in termes of a fourier-Bessel series, exactly like the Fourier series appears when solving the wave equation in linear coordinates.
For the same fundamental reasons, also appears when calculating the Schrödinger equation solution for the hydrogen atom.
Genius: Richard Feynman and Modern Physics by James Gleick (1994) by 
Ciro Santilli 40 Updated 2025-07-16
Ciro Santilli 40 Updated 2025-07-16It has some overlap with Surely You're Joking, Mr. Feynman, which it likely takes as primary sources of some stories.
However, while Surely goes into a lot of detail of each event, this book paints a more cohesive and global picture of things.
In terms of hard physics/mathematics, this book takes the approach of spending a few paragraphs in some chapters describing in high level terms some of the key ideas, which is a good compromise. It does sometime fall into the sin of to talk about something without giving the real name to not scare off the audience, but it does give a lot of names, notably it talks a lot about Lagrangian mechanics. And it goes into more details than Surely in any case.
Amazing talk by Richard Feynman that describes his experiences at Los Alamos National Laboratory while developing the first nuclear weapons.
Transcript: calteches.library.caltech.edu/34/3/FeynmanLosAlamos.htm Also included full text into Surely You're Joking, Mr. Feynman.
- www.youtube.com/watch?v=uY-u1qyRM5w&t=2881s describes the computing aspects. Particularly interesting is the quote about how they used the typist secretary pool to emulate the IBM machines and debug their programs before the machines had arrived. This is exactly analogous to what is done in 2020 in the semiconductor industry, where slower models are used to estimate how future algorithms will run in future hardware.
Los Alamos From Below by Richard Feynman (1975)
Source. Space-Time Approach to Quantum Electrodynamic by Richard Feynman (1949) by Ciro Santilli 40 Updated 2025-07-16
Ciro Santilli 40 Updated 2025-07-16The first key paper to his approach to quantum electrodynamics apparently.
Published on Physical Review 76.769.
quoteinvestigator.com/2017/09/25/progress/ on Quote Investigator says it appeared in 1948. Can't easily check, but will believe it for now.
Biography of Enrico Fermi by fellow physicist, free rent on the on the Internet Archive: archive.org/details/enricofermiphysi0000segr
The World Of Enrico Fermi by Harvard Project Physics (1970) by Ciro Santilli 40 Updated 2025-07-16
Ciro Santilli 40 Updated 2025-07-16Without me, my stack is useless. Without my stack, I am useless. I must fire my requests true. I must shoot straighter than my hackers who are trying to kill me. I must shoot him before he shoots me. I will ...My stack is human, even as I am human, because it is my life. Thus, I will learn it as a brother. I will learn its weaknesses, its strength, its parts, its accessories, its ORMs and its asset bundlers. I will keep my stack clean and ready, even as I am clean and ready. We will become part of each other. We will ...
Explanation: this is an allusion to the Rifleman's Creed. This particular version talks about the website stack chosen for a website, i.e. the libraries used.
Ciro Santilli has always felt that choosing a stack is an almost religious choice. It is perhaps part of why the prayer style of the original Rifleman's Creed resonates with the web stack choice.
It is very hard to know how things are going go, the ups and downs, before putting big hours into it.
And once you start, it is hard, though not impossible, to move away.
Examples:
- html/min.html: minimal valid HTML document. It is insane however.
- html/min-sane.html: minimal sane HTML document. There are smaller valid ones, but they are insane.
- html/img.html
- html/img-broken.html: stackoverflow.com/questions/22051573/how-to-hide-image-broken-icon-using-only-css-html
- html/img-load-lazy.html: stackoverflow.com/questions/2321907/how-do-you-make-images-load-lazily-only-when-they-are-in-the-viewport/57389607#57389607
- html/iframe.html. Uses: html/iframe2.html, html/hello.txt and html/hello
- forms
- YouTube embeds
- css/code-block.html
- css/img-table-vertical-center.html
- css/viewport-height.html: a div that is a tall as the viewport, and does not generate a toplevel scrollbar
- css/responsive-image-max-height.html: here we try to create an image that is never wider than the screen. If the screen is less wide than the image, then the image scales down proportionally. Otherwise, the image has a user determined fixed by the CSS or the HTML
heightproperty. Related:TODO I'm unable to do this....... stackoverflow.com/questions/69964332/how-to-set-the-default-height-of-responsive-images-when-screen-is-wide-and-have The objective was to implement: github.com/ourbigbook/ourbigbook/issues/168 - css/top-navigation.html
Pinned article: Introduction to the OurBigBook Project
Welcome to the OurBigBook Project! Our goal is to create the perfect publishing platform for STEM subjects, and get university-level students to write the best free STEM tutorials ever.
Everyone is welcome to create an account and play with the site: ourbigbook.com/go/register. We belive that students themselves can write amazing tutorials, but teachers are welcome too. You can write about anything you want, it doesn't have to be STEM or even educational. Silly test content is very welcome and you won't be penalized in any way. Just keep it legal!
Intro to OurBigBook
. Source. We have two killer features:
- topics: topics group articles by different users with the same title, e.g. here is the topic for the "Fundamental Theorem of Calculus" ourbigbook.com/go/topic/fundamental-theorem-of-calculusArticles of different users are sorted by upvote within each article page. This feature is a bit like:
- a Wikipedia where each user can have their own version of each article
- a Q&A website like Stack Overflow, where multiple people can give their views on a given topic, and the best ones are sorted by upvote. Except you don't need to wait for someone to ask first, and any topic goes, no matter how narrow or broad
This feature makes it possible for readers to find better explanations of any topic created by other writers. And it allows writers to create an explanation in a place that readers might actually find it.
Figure 1. Screenshot of the "Derivative" topic page. View it live at: ourbigbook.com/go/topic/derivativeVideo 2. OurBigBook Web topics demo. Source. - local editing: you can store all your personal knowledge base content locally in a plaintext markup format that can be edited locally and published either:This way you can be sure that even if OurBigBook.com were to go down one day (which we have no plans to do as it is quite cheap to host!), your content will still be perfectly readable as a static site.
- to OurBigBook.com to get awesome multi-user features like topics and likes
- as HTML files to a static website, which you can host yourself for free on many external providers like GitHub Pages, and remain in full control
Figure 3. Visual Studio Code extension installation.
Figure 4. Visual Studio Code extension tree navigation.
Figure 5. Web editor. You can also edit articles on the Web editor without installing anything locally.Video 3. Edit locally and publish demo. Source. This shows editing OurBigBook Markup and publishing it using the Visual Studio Code extension.Video 4. OurBigBook Visual Studio Code extension editing and navigation demo. Source. 
- Infinitely deep tables of contents:
All our software is open source and hosted at: github.com/ourbigbook/ourbigbook
Further documentation can be found at: docs.ourbigbook.com
Feel free to reach our to us for any help or suggestions: docs.ourbigbook.com/#contact