"Savart" may refer to a couple of different things depending on the context, but it is most commonly associated with the "Savart wheel," which is an instrument used in physics and acoustics. The Savart wheel is a device used to produce and analyze sound waves. It consists of a rotating disc with holes at regular intervals. When air is passed through these holes as the disc spins, it generates a series of tones.
"Welsh units" typically refer to a system of measurement that was historically used in Wales, particularly in agriculture and land measurement. However, the term is not widely recognized in contemporary discussions surrounding units of measurement, as most places have standardized their measurements to metric or imperial systems.
Post's lattice, also known as Post's lattice of recursively enumerable sets, is a mathematical structure in the field of computability theory and recursive function theory. It specifically deals with the relationships between different degrees of unsolvability of decision problems. 1. **Definition**: In the context of computability, a set \( A \) is called recursively enumerable (r.e.
Sednoids refers to a group of trans-Neptunian objects (TNOs) that have orbits significantly influenced by the gravitational pull of a distant, yet-to-be-identified planet, often referred to as "Planet Nine" or "Planet X." The name is derived from the first known member of this group, Sedna, which was discovered in 2003 and has a highly elliptical orbit that takes it far beyond the typical Kuiper Belt.
Tarski's high school algebra problem refers to a challenge posed by mathematician Alfred Tarski regarding the foundations of algebra and the nature of mathematical understanding, particularly at the high school level. Tarski was interested in the formalization of mathematics and the nature of reasoning within mathematical systems. Though Tarski's problem itself isn't typically described in precise terms, it typically revolves around the idea of analyzing the logical and structural aspects of algebraic reasoning that high school students engage in.
Diffuse interstellar bands (DIBs) are a set of absorption lines observed in the spectra of stars that are located behind interstellar dust clouds. These absorption features are seen in the ultraviolet, visible, and near-infrared portions of the electromagnetic spectrum. They are believed to arise from the presence of large, complex molecules or species that exist in the interstellar medium, though their precise nature has not yet been conclusively identified.
EPIC 204376071 is a star cataloged in the Kepler Input Catalog, and is particularly notable for being the host star of an exoplanet discovered by the Kepler space telescope. This star is located in the constellation Cygnus and is part of the Kepler field of view, which was monitored for transiting exoplanets.
Przybylski's Star, also known as HD 101065, is a peculiar and intriguing star located in the constellation Centaurus. It has garnered attention because it exhibits unusual elemental abundances, notably high levels of certain rare elements, including technetium and zirconium. This has led astronomers to study it more closely, as these elements are typically considered products of nuclear processes in stars, suggesting that Przybylski's Star may have a complex evolutionary history.
The Abundance Conjecture is a concept within the field of number theory, focusing on the behavior of certain algebraic integers. Specifically, it deals with the distribution of prime numbers and the density of subsets of integers with specific properties. While the conjecture has been discussed in various contexts, it is often associated with the idea that among the integers, there exists a rich abundance of those that exhibit certain arithmetic properties, such as being prime or having a specific number of divisors.
I can't believe there isn't a YouTube video comparing various substances for each flammability and instability ratings, this would be a huge hit.
TODO what it means to solve an Ising model in general?
stanford.edu/~jeffjar/statmech/lec4.html gives some good notions:
Oxford Instruments by Ciro Santilli 40 Updated 2025-07-16
They are pioneers in making superconducting magnets, physicist from the university taking obsolete equipment from the uni to his garage and making a startup kind of situation. This was particularly notable for this time and place.
They became a major supplier for magnetic resonance imaging applications.
Planck's law by Ciro Santilli 40 Updated 2025-07-16
Used to explain the black-body radiation experiment.
The Quantum Story by Jim Baggott (2011) page 9 mentions that Planck apparently immediately recognized that Planck constant was a new fundamental physical constant, and could have potential applications in the definition of the system of units (TODO where was that published):
Planck wrote that the constants offered: 'the possibility of establishing units of length, mass, time and temperature which are independent of specific bodies or materials and which necessarily maintain their meaning for all time and for all civilizations, even those which are extraterrestrial and nonhuman, constants which therefore can be called "fundamental physical units of measurement".'
This was a visionary insight, and was finally realized in the 2019 redefinition of the SI base units.
Video 1.
Quantum Mechanics 2 - Photons by ViaScience (2012)
Source. Contains a good explanation of how discretization + energy increases with frequency explains the black-body radiation experiment curve: you need more and more energy for small wavelengths, each time higher above the average energy available.
Maser by Ciro Santilli 40 Updated 2025-07-16
Video 1.
Principles of the Optical Maser by Bell Labs
. Source. Date: 1963.
Basically, energy supply has to be modulated rather quickly, because we spend a lot sometimes, and very little other times.
Even not turning it off quickly enough is a problem, as it starts to generate free radicals which fuck you up.
If control came from the nucleus, it has no way to address different mitochondria. But it might be that only one of the mitochondria needs the change. If the nucleus tells all mitochondria to stop producing when only one is full, the others are going to say: "nope, I'm not full, continue producing!" and the one that need to stop will have its signal overridden by the others.

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