Compressibility is a property of materials that describes their ability to change volume under pressure. Specifically, it refers to the measure of how much a given volume of a substance decreases when subjected to an increase in pressure. This property is particularly significant in the study of gases, but it can also apply to liquids and solids to varying extents.
In thermodynamics, conjugate variables are pairs of physical quantities that are related to each other in a specific way, typically in the context of work and energy interactions in a thermodynamic system. Conjugate variables often arise in the context of the first and second laws of thermodynamics and are fundamental to understanding the relationships between different forms of energy and the processes that occur in thermodynamic systems.
Pierre Duhem (1861-1916) was a French physicist, philosopher of science, and historian of science, known for his contributions to the philosophy of science, particularly in the areas of thermodynamics and the philosophy of physics. He is best known for formulating the Duhem-Quine problem, which highlights the complexity of testing scientific theories due to the interconnectedness of hypotheses and auxiliary assumptions.
Latent internal energy refers to the energy stored within a substance that is associated with changes in its phase or state, such as during melting, freezing, vaporization, or condensation. This type of energy is not immediately observable as a change in temperature since it is involved in breaking or forming intermolecular bonds rather than increasing the kinetic energy of the particles.
Thermodynamic activity is a measure of the "effective concentration" of a species in a solution, taking into account interactions between particles. It provides a way to understand how the presence of other components in a mixture influences the behavior of a specific component compared to an ideal situation, where components behave independently. In ideal solutions, the activity (\(a\)) of a species is equal to its molar concentration (\(C\)).
The Volume Correction Factor (VCF) is a coefficient used to adjust the volume of a substance, often liquids, to account for changes in temperature and pressure. The volume of liquids can change significantly with variations in temperature, and since many measurements (like those in the oil and gas industries) require accurate volume readings for billing and inventory purposes, it's essential to correct for these variations.
Johannes Diderik van der Waals (1837–1923) was a Dutch physicist and thermodynamicist best known for his work on the behavior of gases and liquids. He is particularly renowned for formulating the van der Waals equation of state, which describes how real gases deviate from the ideal gas law by incorporating the effects of molecular attraction and the volume occupied by gas molecules.
Bought 2021-11, light brown, size EUR 44.5, 190$, waterproof: www.timberland.co.uk/shop/en/tbl-uk/larchmont-chukka-for-men-in-brown-a12es210
Ciro's Edict #7 Email verification and reCAPTCHA signup protection by 
Ciro Santilli 40 Updated 2025-07-16
Ciro Santilli 40 Updated 2025-07-16Added this basic but fundamental protection layer to the website.
The email setup will of course be reused when notifications are eventually implemented.
Some smart people just brought up to my attention that OurBigBook.com is a bit like: roamresearch.com/ and other graph knowledges. I feel ashemed for not having seen this software and its alternatives before. I was so focused on the "book aspect" of it that I didn't search much in there. I couldn't find an immediate project killer superset from the options in that area, but maybe one exists. We'll see.
And do 5 big queries instead of hundreds of smaller ones.
For example, a README.ciro document that references another document saying:needs to fetch "speed-of-light" from the ID database (previously populated e.g. by preparsing light.ciro:to decide that it should display as "Speed of light" (the title rather than the ID).
The \x[speed-of-light] is fast.= Light
== Speed of lightPreviously, I was doing a separate fetch for each
\x[] as they were needed, leading to hundreds of them at different times.Now I refactored things so that I do very few database queries, but large ones that fetch everything during parsing. And then at render time they are all ready in cache.
This will be fundamental for the live preview on the browser, where the roundtrip to server would make it impossible
Never trust an experiment that is not supported by a good theory by Ciro Santilli 40 Updated 2025-07-16
Ciro Santilli 40 Updated 2025-07-16Not the usual bullshit you were expecting from the philosophy of Science, right?
Some notable quoters:
- Jacques Monod has the exact quote as presented here: pubmed.ncbi.nlm.nih.gov/22042272/, though presumably it was in French, TODO find the French version
- youtu.be/AYC5lE0b8os?t=41 A Computational Whole-Cell Model Predicts Genotype From Phenotype- Markus Covert by "Calit2ube" (2013), see also: Section "Whole cell simulation"
- the book Genius: Richard Feynman and Modern Physics by James Gleick (1994) mentions a few incidents of this involving Feynman, see e.g. chapter "New Particles, New Language" where he and fellow theorist Hans Bethe immediately spot problems with experimentalists' data in suspicious results
Richard Feynman Quantum Electrodynamics Lecture at University of Auckland (1979) by Ciro Santilli 40 Updated 2025-07-16
Ciro Santilli 40 Updated 2025-07-166 hour lecture, where he tries to explain it to an audience that does not know any modern physics. This is a noble effort.
Part of The Douglas Robb Memorial Lectures lecture series.
Feynman apparently also made a book adaptation: QED: The Strange Theory of Light and Matter. That book is basically word by word the same as the presentation, including the diagrams.
According to www.feynman.com/science/qed-lectures-in-new-zealand/ the official upload is at www.vega.org.uk/video/subseries/8 and Vega does show up as a watermark on the video (though it is too pixilated to guess without knowing it), a project that has been discontinued and has has a non-permissive license. Newbs.
4 parts:This talk has the merit of being very experiment oriented on part 2, big kudos: how to teach and learn physics
- Part 1: is saying "photons exist"
- Part 2: is amazing, and describes how photons move as a sum of all possible paths, not sure if it is relativistic at all though, and suggests that something is minimized in that calculation (the action)
- Part 3: is where he hopelessly tries to explain the crucial part of how electrons join the picture in a similar manner to how photons do.He does make the link to light, saying that there is a function which gives the amplitude for a photon going from A to B, where A and B are spacetime events.And then he mentions that there is a similar function for an electron to go from A to B, but says that that function is too complicated, and gives no intuition unlike the photon one.He does not mention it, but P and E are the so called propagators.This is likely the path integral formulation of QED.On Quantum Mechanical View of Reality by Richard Feynman (1983) he mentions that is a Bessel function, without giving further detail.And also mentions that:where
mis basically a scale factor.
such that both are very similar. And that something similar holds for many other particles.And then, when you draw a Feynman diagram, e.g. electron emits photon and both are detected at given positions, you sum over all the possibilities, each amplitude is given by:summed over all possible Spacetime points.This is basically well said at: youtu.be/rZvgGekvHes?t=3349 from Quantum Mechanical View of Reality by Richard Feynman (1983).TODO: how do electron velocities affect where they are likely to end up? suggests the probability only depends on the spacetime points.Also, this clarifies why computations in QED are so insane: you have to sum over every possible point in space!!! TODO but then how do we calculate anything at all in practice? - Part 4: known problems with QED and thoughts on QCD. Boring.
Richard Feynman Quantum Electrodynamics Lecture at University of Auckland (1979) uploaded by Trev M (2015)
Source. Single upload version. Let's use this one for the timestamps I guess.- youtu.be/Alj6q4Y0TNE?t=2217: photomultiplier tube
- youtu.be/Alj6q4Y0TNE?t=2410: local hidden-variable theory
- youtu.be/Alj6q4Y0TNE?t=6444: mirror experiment shown at en.wikipedia.org/w/index.php?title=Quantum_electrodynamics&oldid=991301352#Probability_amplitudes
- youtu.be/Alj6q4Y0TNE?t=7309: mirror experiment with a diffraction grating pattern painted black leads to reflection at a weird angle
- youtu.be/Alj6q4Y0TNE?t=7627: detector under water to explain refraction
- youtu.be/Alj6q4Y0TNE?t=8050: explains biconvex spherical lens in terms of minimal times
- youtu.be/Alj6q4Y0TNE?t=8402: mentions that for events in a series, you multiply the complex number of each step
- youtu.be/Alj6q4Y0TNE?t=9270: mentions that the up to this point, ignored:but it should not be too hard to add those
- amplitude shrinks down with distance
- photon polarization
- youtu.be/Alj6q4Y0TNE?t=11697: finally starts electron interaction. First point is to add time of event detection.
- youtu.be/Alj6q4Y0TNE?t=13704: electron between plates, and mentions the word action, without giving a clear enough idea of what it is unfortunately
- youtu.be/Alj6q4Y0TNE?t=14467: mentions positrons going back in time, but does not clarify it well enough
- youtu.be/Alj6q4Y0TNE?t=16614: on the fourth part, half is about frontiers in quantum electrodynamics, and half full blown theory of everything. The QED part goes into renormalization and the large number of parameters of the Standard Model
The natural sciences are not just a tool to predict the future.
They are a reminder that the lives that we live daily are mere illusions, religious concepts such as Maya and Samsara come to mind.
We as individuals perceive nothing about the materials that we touch every day really work, nor more importantly how our brain and cell work.
Everything is magic out of our control.
The natural sciences allow us peek, with huge concentrated effort, into tiny little bits a little of those unknowns, and blow our minds as we notice that we don't know anything.
For all practical purposes in life, there is a huge macro micro gap. We are only able to directly perceive and influence the macro events. And through those we try to affect micro events. Because for good or bad, micro events reflect in the macro world.
It is as if we live in a different plane of existence above molecules, and below galaxies. The hierarchy of Figure "xkcd 435: Fields arranged by purity" puts that nicely into perspective, shame it only starts at the economical level, not going up to astronomy.
The great beauty of science is that it allows us to puncture through some of the layers of reality, either up or down, away from our daily experience.
And the great beauty of artificial intelligence research is that it allows to peer deeper into exactly our layer of existence.
Every one or two weeks Ciro Santilli remembers that he and everything he touches are just a bunch of atoms, and that is an amazing feeling. This is Ciro's preferred source of Great doubt. Another concept that comes to mind is when you see it, you'll shit bricks.
Perhaps, the feeling of physics and the illusion of life reaches its peak in molecular biology.
Just look at your fucking hand right now.
Do you have any idea of each of the cells in it work? Isn't is at least 100 times more complex than the materials of the table you hand is currently resting on?
This is the non-science fiction version of the lotus-Eater Machine.
Alan Watts's "Philosopher" talk mentions related ideas:
The origin of a person who is defined as a philosopher, is one who finds that existence itself is exceedingly odd.
The toddler of a friend of Ciro Santilli's wife asked her mum:Our perception of the macroscopic world is so magic that children have to learn the difference between living and non-living things.
James Somers put it very well as well in his article I should have loved biology by James Somers, this quote was brought to Ciro's attention by Bert Hubert's website[ref].The same applies to other natural sciences.
I should have loved biology but I found it to be a lifeless recitation of names: the Golgi apparatus and the Krebs cycle; mitosis, meiosis; DNA, RNA, mRNA, tRNA.In the textbooks, astonishing facts were presented without astonishment. Someone probably told me that every cell in my body has the same DNA. But no one shook me by the shoulders, saying how crazy that was. I needed Lewis Thomas, who wrote in The Medusa and the Snail:For the real amazement, if you wish to be amazed, is this process. You start out as a single cell derived from the coupling of a sperm and an egg; this divides in two, then four, then eight, and so on, and at a certain stage there emerges a single cell which has as all its progeny the human brain. The mere existence of such a cell should be one of the great astonishments of the earth. People ought to be walking around all day, all through their waking hours calling to each other in endless wonderment, talking of nothing except that cell.
Alan Watts' "Philosopher" talk (1973)
Source. Lecture given at UCLA on 1973-02-21. Some key quotes from the talk:The origin of a person who is defined as a philosopher, is one who finds that existence itself is exceedingly odd.
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