Chat programs that don't have a proper web-only operation and force you to have a mobile phone, e.g. WhatsApp.
Heck, even Signal, which is supposed to be super secure and good for your privacy, forces you to disclose your freaking cell phone to all contacts! lifehacker.com/how-to-use-signal-without-revealing-your-private-phone-1818996580
What is my phone breaks? What if I don't want to have a fucking phone? What if I move countries and have to change the fucking number? Also evil but less because done by all: chat programs that can't send you an email if you don't see the message in X minutes.
European Union, time to force those evil companies to use support open standards like XMPP?
The solution to "how to prevent spam" is simple: your ID is a public key that you own the private key for. If you start getting spammed, generate a new public key, and send it to all contacts, and dump the previous ID.
Email by Ciro Santilli 40 Updated 2025-07-16
Ciro Santilli's email can be found by cloning one of his repositories on GitHub. It is also given at: Section "How to contact Ciro Santilli".
Their reference markup is incredibly overengineered, convoluted, and underdocumented, it is unbelivable!
Use the reference:
This is a fact.{{sfn|Schweber|1994|p=487}}
Define the reference:
===Sources===
{{refbegin|2|indent=yes}}
*{{Cite book|author-link=Silvan S. Schweber |title=QED and the Men Who Made It: Dyson, Feynman, Schwinger, and Tomonaga|last=Schweber|first=Silvan S.|location=Princeton|publisher=University Press|year=1994 |isbn=978-0-691-03327-3 |url=https://archive.org/details/qedmenwhomadeitd0000schw/page/492 |url-access=registration}}
{{refend}}
sfn is magic and matches the the author last name and date from the Cite, it is documented at: en.wikipedia.org/wiki/Template:Sfn
Unforutunately, if there are multiple duplicate Cites inline in the article, it will complain that there are multiple definitions, and you have to first factor out the article by replacing all those existing Cite with sfn, and keeping just one Cite at the bottom. What a pain...
You can also link to a specific page of the book, e.g. if it is a book is on Internet Archive Open Library with:
{{sfn|Murray|1997|p=[https://archive.org/details/supermenstory00murr/page/86 86]}}
For multiple pages should use pp= instead of p=. Does not seem to make much difference on the rendered output besides showing p. vs pp., but so be it:
{{sfn|Murray|1997|pp=[https://archive.org/details/supermenstory00murr/page/86 86-87]}}
Lorentz force by Ciro Santilli 40 Updated 2025-07-16
Equation 1.
Lorentz force
.
A little suspicious that it bears the name of Lorentz, who is famous for special relativity, isn't it? See: Maxwell's equations require special relativity.
For numerical algorithms and to get a more low level understanding of the equations, we can expand all terms to the simpler and more explicit form:
Coulomb's law by Ciro Santilli 40 Updated 2025-07-16
Static case of Maxwell's law for electricity only.
The "static" part is important: if this law were true for moving charges, we would be able to transmit information instantly at infinite distances. This is basically where the idea of field comes in.
Video 1.
Coulomb's Law experiment with torsion balance with a mirror on the balance to amplify rotations by uclaphysics (2010)
Source.
Video 1.
Understanding Electromagnetic Radiation! by Learn Engineering (2019)
Source. Shows animations of a dipole antenna which illustrates well how radiation is emitted from moving charges and travels at the speed of light.
Hall effect by Ciro Santilli 40 Updated 2025-07-16
The voltage changes perpendicular to the current when magnetic field is applied.
Figure 1.
Hall effect experimental diagram
. Source. The Hall effect refers to the produced voltage , AKA on this setup.
An intuitive video is:
The key formula for it is:
where:
Applications:
Other more precise non-classical versions:

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!
We have two killer features:
  1. 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-calculus
    Articles 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/derivative
  2. 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.
    Figure 5. . 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.
  3. https://raw.githubusercontent.com/ourbigbook/ourbigbook-media/master/feature/x/hilbert-space-arrow.png
  4. Infinitely deep tables of contents:
    Figure 6.
    Dynamic article tree with infinitely deep table of contents
    .
    Descendant pages can also show up as toplevel e.g.: ourbigbook.com/cirosantilli/chordate-subclade
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