Atomic clock by Ciro Santilli 40 Updated 2025-07-16
Video 1.
How an atomic clock works, and its use in the global positioning system (GPS) by EngineerGuy (2012)
Source. Shows how conceptually an atomic clock is based on a feedback loop of two hyperfine structure states of caesium atoms (non-radioactive caesium-133 as clarified by the Wikipedia page). Like a quartz clock, it also relies on the piezoelectricity of quartz, but unlike the quartz clock, the quartz is not shaped like a tuning fork, and has a much larger resonating frequency of about 7 MHz. The feedback is completed by producing photons that resonate at the right frequency to excite the caesium.
Video 2.
Inside the HP 5061A Cesium Clock by CuriousMarc (2020)
Source.
A similar model was used in the Hafele-Keating experiment to test special relativity on two planes flying in opposite directions. Miniaturization was key.
Contains a disposable tube with 6g of Caesium. You boil it, so when it runs out, you change the tube, 40k USD. Their tube is made by Agilent Technologies, so a replacement since that opened in 1999, and the original machine is from the 60s.
Detection is done with an electron multiplier.
youtu.be/eOti3kKWX-c?t=1166 They compare it with their 100 dollar GPS disciplined oscillator, since GPS satellites have atomic clocks in them.
Video 3. Source. Their super accurate setup first does laser cooling on the caesium atoms.
Eli Benderski by Ciro Santilli 40 Updated 2025-07-16
Amazing systems programming tutorials. Whenever you Google a hard topic, his blog comes up.
Also has many great contributions on Stack Overflow: stackoverflow.com/users/8206/eli-bendersky
As of 2016, Eli worked at Google (reference). TODO before that, I had found his earlier info previously but lost it.
Eli focuses mostly on compiler toolchains.
Gas chromatography by Ciro Santilli 40 Updated 2025-07-16
This technique is crazy! It allows to both:
  • separate gaseous mixtures
  • identify gaseous compounds
You actually see discrete peaks at different minute counts on the other end.
It is based on how much the gas interacts with the column.
Detection is usually done burning the sample to ionize it when it comes out, and then you measure the current produced.
The procedure remind you a bit of gel electrophoresis, except that it is in gaseous phase.
Video 2.
How I invented the electron capture detector interview with James Lovelock by Web of Stories (2001)
Source. He mentions how scientists had to make their own tools during the 40s/60s. Then how gas chromatography was invented at the National Institute for Medical Research and gained a Nobel Prize. Lovelock came in improving the detection part of things.
Eligius pool by Ciro Santilli 40 Updated 2025-07-16
Created by Luke Dashjr.
The pool is named after Saint Eligius, patron of miners[ref]
Eligius also means to "choose" or "chosen" in Latin: en.wiktionary.org/wiki/Eligius, same root as "to elect" in modern English presumably.
Figure 1.
Saint Eligius by Petrus Christus
. Source. Eligius pool is named after Saint Eligius, patron of goldsmiths and miners[ref]
Silvano Martello is an Italian actor, director, and playwright, known for his work in theater and film. He may not be widely known in mainstream cinema, but he has contributed significantly to the performing arts, particularly in Italy.
Process psychology is a theoretical perspective within psychology that emphasizes the dynamic, unfolding processes of mental activities and interactions over static traits or states. Rather than focusing solely on fixed characteristics, process psychology examines how psychological phenomena change over time, how people's behaviors and thoughts develop, and how interactions within environments shape individuals. The key aspects of process psychology include: 1. **Dynamic Interactions**: It focuses on how individuals interact with their environments, including social contexts, cultural influences, and situational factors.
Grand Unified Theory by Ciro Santilli 40 Updated 2025-07-16
Appears to be an unsolved physics problem. TODO why? Don't they all fit into the Standard Model already? So why is strong force less unified with electroweak, than electromagnetic + weak is unified in electroweak?
The Bernoulli scheme, often referenced in the context of probability theory and stochastic processes, generally refers to a specific sequence of independent Bernoulli trials. Each trial has two possible outcomes, often labeled as "success" (often represented as 1) and "failure" (represented as 0), with a fixed probability of success \( p \) for each trial and a probability of failure \( 1 - p \).
Confusion and diffusion are terms that can have various meanings based on context, including psychology, literature, and general usage. Here are brief explanations of both concepts in a few different contexts: ### Confusion 1. **Psychology**: In a psychological context, confusion refers to a state where an individual has difficulty understanding or making sense of information, often resulting in uncertainty or indecision. This can arise from cognitive overload, conflicting information, or emotional distress.
The Higgs field is a fundamental field in particle physics, associated with the Higgs boson, and plays a crucial role in the Standard Model of particle physics. Classically, the Higgs field can be understood as a scalar field that permeates all of space. Here's an overview of its key characteristics: 1. **Scalar Field**: The Higgs field is a scalar field, meaning it is characterized by a single value at every point in space and time.
Curie's principle, formulated by the French physicist Pierre Curie, states that "when a physical phenomenon exhibits symmetry, the causes of that phenomenon must also exhibit the same symmetry." In other words, if a system has a certain symmetry, any effects or changes resulting from that system should also respect that symmetry. This principle is particularly relevant in fields such as crystallography, material science, and physics in general, helping to predict how materials will behave under various conditions.

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 2.
    You can publish local OurBigBook lightweight markup files to either https://OurBigBook.com or as a static website
    .
    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.
  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