Physics (like all well done science) is the art of predicting the future by modelling the world with mathematics.

And predicting the future is the first step towards controlling it, i.e.: engineering.

Ciro Santilli doesn't know physics. He writes about it partly to start playing with some scientific content for: OurBigBook.com, partly because this stuff is just amazingly beautiful.

Ciro's main intellectual physics fetishes are to learn quantum electrodynamics (understanding the point of Lie groups being a subpart of that) and condensed matter physics.

Every science is Physics in disguise, but the number of objects in the real world is so large that we can't solve the real equations in practice.

Luckily, due to emergence, we can use uglier higher level approximations of the world to solve many problems, with the complex limits of applicability of those approximations.

Therefore, such higher level approximations are highly specialized, and given different names such as:

As of 2019, all known physics can be described by two theories:

Unifying those two into the theory of everything one of the major goals of modern physics.

The approach many courses take to physics, specially "modern Physics" is really bad, this is how it should be taught:

- start by describing experiments that the previous best theory did not explain, see also: Section "Physics education needs more focus on understanding experiments and their history"
- then, give the final formula for the next best theory
- then, give all the important final implications of that formula, and how it amazingly describes the experiments. In particular this means: doing physics means calculating a number
- then, give some mathematical intuition on the formulas, and how the main equation could have been derived
- finally, then and only then, start deriving the outcomes of the main formula in detail

This is likely because at some point, experiments get more and more complicated, and so people are tempted to say "this is the truth" instead of "this is why we think this is the truth", which is much harder.

But we can't be lazy, there is no replacement to the why.

Related:

- settheory.net/learnphysics and www.youtube.com/watch?v=5MKjPYuD60I&list=PLJcTRymdlUQPwx8qU4ln83huPx-6Y3XxH from settheory.net
- math.ucr.edu/home/baez/books.html by John Baez. Mentions:Ciro Santilli is trying to change that: OurBigBook.com.
This webpage doesn't have lots of links to websites. Websites just don't have the sort of in-depth material you need to learn technical subjects like advanced math and physics — at least, not yet. To learn this stuff, you need to read lots of books

- web.archive.org/web/20210324182549/http://jakobschwichtenberg.com/one-thing/ by Jakob Schwichtenberg

This is the only way to truly understand and appreciate the subject.

Understanding the experiments gets intimately entangled with basically learning the history of physics, which is extremely beneficial as also highlighted by Ron Maimon, related: there is value in tutorials written by early pioneers of the field.

"How we know" is a basically more fundamental point than "what we know" in the natural sciences.

In the Surely You're Joking, Mr. Feynman chapter O Americano, Outra Vez! Richard Feynman describes his experience teaching in Brazil in the early 1950s, and how everything was memorized, without any explanation of the experiments or that the theory has some relationship to the real world!

Although things have improved considerably since in Brazil, Ciro still feels that some areas of physics are still taught without enough experiments described upfront. Notably, ironically, quantum field theory, which is where Feynman himself worked.

Feynman gave huge importance to understanding and explaining experiments, as can also be seen on Richard Feynman Quantum Electrodynamics Lecture at University of Auckland (1979).

Everyone is beginner when the field is new, and there is value in tutorials written by beginners.

For example, Ciro Santilli felt it shocking how direct and satisfying Richard Feynman's scientific vulgarization of quantum electrodynamics were, e.g. at: Richard Feynman Quantum Electrodynamics Lecture at University of Auckland (1979), and that if he had just assumed minimal knowledge of mathematics, he was about to give a full satisfactory picture in just a few hours.

Other supporters of this:

- Ron Maimon: the same also applies to early original papers of the field, not just tutorials
- Dean Kamen: quick mention at: fi.edu/en/awards/laureates/dean-kamen, but a better longer mention on Dreamer (2020), nearby section from trailer: youtu.be/Cj2VKVJKf1I?t=16

In Physics, in order to test a theory, you must be able to extract a number from it.

It does not matter how, if it is exact, or numerical, or a message from God: a number has to come out of the formulas in the end, and you have to compare it with the experimental data.

Many theoretical physicists seem to forget this in their lectures, see also: Section "How to teach and learn physics".

Nature is a black box, right?

You don't need to understand the from first principles derivation of every single phenomena.

And most important of all: you should not start learning phenomena by reading the from first principles derivation.

Instead, you should see what happens in experiments, and how matches some known formula (which hopefully has been derived from first principles).

Only open the boxes (understand from first principles derivation) if the need is felt!

E.g.:

- you don't need to understand everything about why SQUID devices have their specific I-V curve curve. You have to first of all learn what the I-V curve would be in an experiment!
- you don't need to understand the fine details of how cavity magnetrons work. What you need to understand first is what kind of microwave you get from what kind of input (DC current), and how that compares to other sources of microwaves
- lasers: same

Physics is all about predicting the future. If you can predict the future with an end result, that's already predicting the future, and valid.

Videos should be found/made for all of those: videos of all key physics experiments

- speed of light experiment
- basically all experiments listed under Section "Quantum mechanics experiment" such as:
- Davisson-Germer experiment

This shows that viewing electromagnetism as gauge theory does have experimentally observable consequences. TODO understand what that means.

In more understandable terms, it shows that the magnetic vector potential matters where the magnetic field is 0.

Classic theory predicts that the output frequency must be the same as the input one since the electromagnetic wave makes the electron vibrate with same frequency as itself, which then irradiates further waves.

But the output waves are longer because photons are discrete and energy is proportional to frequency:

The formula is exactly that of two relativistic billiard balls colliding.

Therefore this is evidence that photons exist and have momentum.

No matter how hight the wave intensity, if it the frequency is small, no photons are removed from the material.

This is different from classic waves where energy is proportional to intensity, and coherent with the existence of photons and the Planck-Einstein relation.

- why the square: physics.stackexchange.com/questions/535/why-does-kinetic-energy-increase-quadratically-not-linearly-with-speed on Physics Stack Exchange. Ron Maimon's answer is great, as it relies only on the following staring points:He also offers a symmetry argument considering the case of potential energy.
- why the half: physics.stackexchange.com/questions/27847/why-is-there-a-frac-1-2-in-frac-1-2-mv2 on Physics Stack Exchange

- physics.stackexchange.com/questions/26797/why-does-work-equal-force-times-distance
- www.quora.com/Why-do-we-define-work-as-force-times-distance
- physics.stackexchange.com/questions/428525/why-does-work-depend-on-distance
- physics.stackexchange.com/questions/79523/why-does-the-amount-of-energy-transferred-depend-on-distance-rather-than-time

Experiment and theory are like the yin and yang: opposites, but one cannot exist without the other.

Quantum Field Theory lecture notes by David Tong (2007) puts it well:This is also mentioned e.g. at Video 2. "The Quantum Experiment that ALMOST broke Locality by The Science Asylum (2019)".

In classical physics, the primary reason for introducing the concept of the field is to construct laws of Nature that are local. The old laws of Coulomb and Newton involve "action at a distance". This means that the force felt by an electron (or planet) changes immediately if a distant proton (or star) moves. This situation is philosophically unsatisfactory. More importantly, it is also experimentally wrong. The field theories of Maxwell and Einstein remedy the situation, with all interactions mediated in a local fashion by the field.

In simple terms, if you believe in the Schrödinger equation and its modern probabilistic interpretation as described in the Schrödinger picture, then at first it seem that there is no strict causality to the outcome of experiments.

People have then tried to recover that by assuming that there is some inner sate beyond the Schrödinger equation, but these ideas are refuted by Bell test experiments, unless we give up the principle of locality, which feels more important, especially in special relativity, where faster-than-light implies time travel, which breaks causality even more dramatically.

The de Broglie-Bohm theory is a deterministic but non-local formulation of quantum mechanics.

If something does a quantum jump, what causes it to decide doing so at a particular time and not another? It is expected that a continuous cause would have continuous effects.

This concern was raised immediately by Rutherford while reviewing the Bohr model in 1913 as mentioned in The Quantum Story by Jim Baggott (2011) page 32.

Good reading list: Abraham Pais Prize for History of Physics.

Computational physics is a good way to get valuable intuition about the key equations of physics, and train your numerical analysis skills:

- classical mechanics
- "Real-time heat equation OpenGL visualization with interactive mouse cursor using relaxation method" under the best articles by Ciro Santillis

- phet.colorado.edu PhET simulations from University of Colorado Boulder

Other child sections:

Ah, the jewel of computational physics.

Also known as an ab initio method: no experimental measurement is taken as input, QED is all you need.

But since QED is thought to fully describe all relevant aspects molecules, it could be called "the" ab initio method.

For one, if we were able to predict protein molecule interactions, our understanding of molecular biology technologies would be solved.

No more ultra expensive and complicated X-ray crystallography or cryogenic electron microscopy.

And the fact that quantum computers are one of the most promising advances to this field, is also very very exciting: Section "Quantum algorithm".

- www.youtube.com/watch?v=NtnsHtYYKf0 "Mercury and Relativity - Periodic Table of Videos" by a

TODO what's the largest molecule done on a classical computer?

- www.ibm.com/blogs/research/2017/09/quantum-molecule/
- www.nature.com/articles/nature23879 "Hardware-efficient variational quantum eigensolver for small molecules and quantum magnets"
- www.sciencemag.org/news/2017/09/quantum-computer-simulates-largest-molecule-yet-sparking-hope-future-drug-discoveries

Sponsored by National Academy of Sciences, located in Long Island.

Some photos at: www.nasonline.org/about-nas/history/archives/milestones-in-NAS-history/shelter-island-conference-photos.html on the website of National Academy of Sciences, therefore canon.

This is where Isidor Rabi exposed experiments carried out on the anomalous magnetic dipole moment and Willis Lamb presented his work on the Lamb shift.

It was a very private and intimate conference, that gathered the best physicists of the area, one is reminded of the style of the Solvay Conference.

QED and the men who made it: Dyson, Feynman, Schwinger, and Tomonaga by Silvan Schweber (1994) chapter 4.1 this conference was soon compared to the First Solvay Conference (1911), which set in motion the development of non-relativistic quantum mechanics.

Followup to the Shelter Island Conference, this is where Julian Schwinger and Richard Feynman exposed their theories to explain the experiments of the previous conference.

Julian made a formal presentation that took until the afternoon and bored everyone to death, though the mathematics avoided much questioning.

Feynman then presented his revolutionary approach, which he was unable to prove basic properties of, but which gave correct results, and people were not very happy.

The most important ones are:

- theory of everything. We are certain that our base equations are wrong, but we don't know how to fix them :-)
- full explanation of high-temperature superconductivity. Superconductivity already has a gazillion applications, and doing it in higher temperatures would add a gazillion more, and maybe this theoretical explanation would help us find new high temperature superconducting materials more effectively
- fractional quantum Hall effect 5/2

Other super important ones:

- neutrino mass measurement and explanation

The only one on GitHub. In RST and renders to HTML with image formulas.

Too "direct formula overload" at first look.

By the creator of SymPy, who works at Los Alamos National Laboratory and has a PhD in chemical physics: swww.linkedin.com/in/ondřej-čertík-064b355b/ Man, big kudos to this dude.

This is quite in-depth, pretty good.

Unrelated to the Khan Academy.

Cute simple paper-cut stop motion animations videos by Mithuna Yoganathan, a PhD in theoretical physics at the University of Cambridge: www.damtp.cam.ac.uk/person/my332.

This has the seeds of direct good intuition, but often stops a bit too short. Worth a look though, there is value in them for beginners.

Very practical, low-cost experiments.

Falls a bit too much on the basic side of the the missing link between basic and advanced.

This is very promising.

TODO find teacher name, all seem to be made by the same cute dude from UCSB.

Does have some gems worth looking at. But generally always too superficial as can be expected from any self-sufficient YouTubber.

The strongest are:

- early 20th century: Annalen der Physik: God OG physics journal of the early 20th century, before the Nazis fucked German science back to the Middle Ages
- 20s/30s: Nature started picking up strong
- 40s/50s: American journals started to come in strong after all the genius Jews escaped from Germany, notably Physical Review Letters

List of the sub-journals at: journals.aps.org/browse

As indicated by its name, the journal contains mostly short letters sent to the editor, often 2 or 3 pages long, which allows for a faster publication cycle and dissemination of new results. This is notably useful for experimental physics.

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