Physics is the art of predicting the future by modelling the world with mathematics.
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.
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:
- http://settheory.net/learnphysics and https://www.youtube.com/watch?v=5MKjPYuD60I&list=PLJcTRymdlUQPwx8qU4ln83huPx-6Y3XxH from settheory.net
- https://math.ucr.edu/home/baez/books.html by John Baez. Mentions:
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
Ciro Santilli is trying to change that: OurBigBook.com. - https://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.
The same also applies to early original papers of the field, as notably put forward by Ron Maimon.
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".
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.
2s/2p energy split, not predicted by the Dirac equation, but explained by quantum electrodynamics, which is one of the first great triumphs of that theory.
Initial experiment: Lamb-Retherford experiment.
- https://www.youtube.com/watch?v=jPKEuiUNJIk Lamb Shift by Dr. Nissar Ahmad (2020)
On the return from the train from the Shelter Island Conference in New York, Hans Bethe managed to do a non-relativistic calculation of the Lamb shift. He then published as The Electromagnetic Shift of Energy Levels by Hans Bethe (1947) which is still paywalled as of 2021, fuck me: https://journals.aps.org/pr/abstract/10.1103/PhysRev.72.339 by Physical review.
The Electromagnetic Shift of Energy Levels Freeman Dyson (1948) published on Physical review is apparently a relativistic analysis of the same: https://journals.aps.org/pr/abstract/10.1103/PhysRev.73.617 also paywalled as of 2021.
TODO how do the infinities show up, and how did people solve them?
https://www.mdpi.com/2624-8174/2/2/8/pdf History and Some Aspects of the Lamb Shift by G. Jordan Maclay (2019)
Mentions that he moved to the USA from the United Kingdom specifically because great experiments were being carried at Columbia University, which is where the Lamb-Retherford experiment was done, and that Isidor Isaac Rabi was the head at the time.
He then explains mass renormalization briefly: instead of calculating from scratch, you just compare the raw electron to the bound electron and take the difference. Both of those have infinities in them, but the difference between them cancels out those infinities.
Ahh, Hans is so old in that video, it is sad to see. He did live a lot tough. Mentions that the shift is of about 1000 MHz.
The following video: https://www.youtube.com/watch?v=vZvQg3bkV7s Hans Bethe - Calculating the Lamb shift.
Published as Fine Structure of the Hydrogen Atom by a Microwave Method by Willis Lamb and Robert Retherford (1947) on Physical review.
microwave technology was developed in World War II for radar, notably at the MIT Radiation Laboratory. Before that, people were using much higher frequencies such as the visible spectrum. But to detect small energy differences, you need to look into longer wavelengths.
This experiment was fundamental to the development of quantum electrodynamics. As mentioned at Genius: Richard Feynman and Modern Physics by James Gleick (1994) chapter "Shrinking the infinities", before the experiment, people already knew that trying to add electromagnetism to the Dirac equation led to infinities using previous methods, and something needed to change urgently. However for the first time now the theorists had one precise number to try and hack their formulas to reach, not just a philosophical debate about infinities, and this led to major breakthroughs. The same book also describes the experiment briefly as:
Willis Lamb had just shined a beam of microwaves onto a hot wisp of hydrogen blowing from an oven.
This one has open accesses as of 2021: https://journals.aps.org/pr/pdf/10.1103/PhysRev.72.241
It is two pages and a half long.
They were at Columbia University in the Columbia Radiation Laboratory. Robert was Willis' graduate student.
Previous less experiments had already hinted at this effect, but they were too imprecise to be sure.
- why the square: https://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: https://physics.stackexchange.com/questions/27847/why-is-there-a-frac-1-2-in-frac-1-2-mv2 on Physics Stack Exchange
- https://physics.stackexchange.com/questions/26797/why-does-work-equal-force-times-distance
- https://www.quora.com/Why-do-we-define-work-as-force-times-distance
- https://physics.stackexchange.com/questions/428525/why-does-work-depend-on-distance
- https://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:
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.This is also mentioned e.g. at Video 2. "The Quantum Experiment that ALMOST broke Locality by The Science Asylum (2019)".
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 Santilli
- https://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".
- https://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?
- https://www.ibm.com/blogs/research/2017/09/quantum-molecule/
- https://www.nature.com/articles/nature23879 "Hardware-efficient variational quantum eigensolver for small molecules and quantum magnets"
- https://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: http://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.
Not the usual bullshit you were expecting from the philosophy of Science, right?
Some notable quoters:
- Jacques Monod has the exact quote as presented here: https://pubmed.ncbi.nlm.nih.gov/22042272/, though presumably it was in French, TODO find the French version
- https://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
The natural sciences are not just a tool to predict the future.
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 1. "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:
Why doesn't my tiger doll close its eyes when we sleep?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.
The origin of a person who is defined as a philosopher, is one who finds that existence itself is exceedingly odd.
Nothing makes the fact that your life is an illusion clearer than animations of molecular biology processes. You just have no idea what is going on inside your own body right now!
And yet, we live, oblivious to all of it.
Amazing creators:
Drew Berry recommends having a look at clarafi.
Uses CC BY-SA, what a hero.
Goes along: if you could control your life multiple times to be perfect, you would eventually get tired of paradise, and you would go further and further into creating uncertain worlds with some suffering, until you would reach the current real world.
Very similar to The Matrix (1999) when Agent Smith talks about the failed Paradise Matrix shown at https://www.youtube.com/watch?v=9Qs3GlNZMhY:
Did you know that the first Matrix was designed to be a perfect human world where none suffered, where everyone would be happy? It was a disaster. No one would accept the program. Entire crops were lost. Some believed that we lacked the programming language to describe your "perfect world". But I believe that, as a species, human beings define their reality through misery and suffering. So the perfect world was a dream that your primitive cerebrum kept trying to wake up from.
From episode "Mortynight Run"
Look at this. You beat cancer, and then you went back to work at the carpet store? Booooh.
Figure 1. "xkcd 435: Fields arranged by purity." must again be cited.
The opposite of from first principles.
Basically the opposite of reductionism.
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: shttps://www.linkedin.com/in/ondřej-čertík-064b355b/ Man, big kudos to this dude.
This is quite in-depth, pretty good.
Cute simple paper-cut stop motion animations videos by Mithuna Yoganathan, a PhD in theoretical physics at the University of Cambridge: http://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.