Atomic clock Updated +Created
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.
Quick presentation of the atomic clock at the National Physical Laboratory (2010)
Source. Their super accurate setup first does laser cooling on the caesium atoms.
History of quantum mechanics Updated +Created
The discovery of the photon was one of the major initiators of quantum mechanics.
Light was very well known to be a wave through diffraction experiments. So how could it also be a particle???
This was a key development for people to eventually notice that the electron is also a wave.
This process "started" in 1900 with Planck's law which was based on discrete energy packets being exchanged as exposed at On the Theory of the Energy Distribution Law of the Normal Spectrum by Max Planck (1900).
This ideas was reinforced by Einstein's explanation of the photoelectric effect in 1905 in terms of photon.
In the next big development was the Bohr model in 1913, which supposed non-classical physics new quantization rules for the electron which explained the hydrogen emission spectrum. The quantization rule used made use of the Planck constant, and so served an initial link between the emerging quantized nature of light, and that of the electron.
The final phase started in 1923, when Louis de Broglie proposed that in analogy to photons, electrons might also be waves, a statement made more precise through the de Broglie relations.
This event opened the floodgates, and soon matrix mechanics was published in quantum mechanical re-interpretation of kinematic and mechanical relations by Heisenberg (1925), as the first coherent formulation of quantum mechanics.
It was followed by the Schrödinger equation in 1926, which proposed an equivalent partial differential equation formulation to matrix mechanics, a mathematical formulation that was more familiar to physicists than the matrix ideas of Heisenberg.
Inward Bound by Abraham Pais (1988) summarizes his views of the main developments of the subjectit:
  • Planck's on the discovery of the quantum theory (1900);
  • Einstein's on the light-quantum (1905);
  • Bohr's on the hydrogen atom (1913);
  • Bose's on what came to be called quantum statistics (1924);
  • Heisenberg's on what came to be known as matrix mechanics (1925);
  • and Schroedinger's on wave mechanics (1926).
Lagrangian mechanics Updated +Created
Originally it was likely created to study constrained mechanical systems where you want to use some "custom convenient" variables to parametrize things instead of global x, y, z. Classical examples that you must have in mind include:
When doing lagrangian mechanics, we just lump together all generalized coordinates into a single vector that maps time to the full state:
where each component can be anything, either the x/y/z coordinates relative to the ground of different particles, or angles, or nay other crazy thing we want.
The Lagrangian is a function that maps:
to a real number.
Then, the stationary action principle says that the actual path taken obeys the Euler-Lagrange equation:
This produces a system of partial differential equations with:
  • equations
  • unknown functions
  • at most second order derivatives of . Those appear because of the chain rule on the second term.
The mixture of so many derivatives is a bit mind mending, so we can clarify them a bit further. At:
the is just identifying which argument of the Lagrangian we are differentiating by: the i-th according to the order of our definition of the Lagrangian. It is not the actual function, just a mnemonic.
Then at:
  • the part is just like the previous term, just identifies the argument with index ( because we have the non derivative arguments)
  • after the partial derivative is taken and returns a new function , then the multivariable chain rule comes in and expands everything into terms
However, people later noticed that the Lagrangian had some nice properties related to Lie group continuous symmetries.
Basically it seems that the easiest way to come up with new quantum field theory models is to first find the Lagrangian, and then derive the equations of motion from them.
For every continuous symmetry in the system (modelled by a Lie group), there is a corresponding conservation law: local symmetries of the Lagrangian imply conserved currents.
Genius: Richard Feynman and Modern Physics by James Gleick (1994) chapter "The Best Path" mentions that Richard Feynman didn't like the Lagrangian mechanics approach when he started university at MIT, because he felt it was too magical. The reason is that the Lagrangian approach basically starts from the principle that "nature minimizes the action across time globally". This implies that things that will happen in the future are also taken into consideration when deciding what has to happen before them! Much like the lifeguard in the lifegard problem making global decisions about the future. However, chapter "Least Action in Quantum Mechanics" comments that Feynman later notice that this was indeed necessary while developping Wheeler-Feynman absorber theory into quantum electrodynamics, because they felt that it would make more sense to consider things that way while playing with ideas such as positrons are electrons travelling back in time. This is in contrast with Hamiltonian mechanics, where the idea of time moving foward is more directly present, e.g. as in the Schrödinger equation.
Furthermore, given the symmetry, we can calculate the derived conservation law, and vice versa.
And partly due to the above observations, it was noticed that the easiest way to describe the fundamental laws of particle physics and make calculations with them is to first formulate their Lagrangian somehow: why do symmetries such as SU(3), SU(2) and U(1) matter in particle physics?s.
Bibliography:
Video 1.
Euler-Lagrange equation explained intuitively - Lagrangian Mechanics by Physics Videos by Eugene Khutoryansky (2018)
Source. Well, unsurprisingly, it is exactly what you can expect from an Eugene Khutoryansky video.
Luboš Motl Updated +Created
How to convince teachers to use CC BY-SA Updated +Created
A major difficulty of getting such this to work is that may university teachers want to retain closed copyright of their work because they:
Therefore the only way is to find teachers who are:
  • enlightened to use such licenses
  • forced by their organizations to use such licenses
The forced option therefore seems like a more bulk efficient starting point for searches.
No matter how much effort a single person puts into writing perfect tutorials, they will never beat 1000x people + an algorithm.
It is not simply a matter of how much time you have. The fundamental reason is that each person has a different background and different skills. Notably the young students have radically different understanding than that of the experienced teacher.
Therefore, those that refuse to contribute to such platforms, or at least license their content with open licenses, will inevitably have their work forgotten in favor of those that have contributed to the more open platform, which will eventually dominate everything.
Perhaps OurBigBook.com is not he killer platform that will make this happen. Perhaps the world is not yet ready for it. But Ciro believes that this will happen, sooner or later, inevitable, and he wants to give it a shot.
Also worth checking:
Figure 1. Source. Convincing academics that their tutorial are not always perfect is one of blocking points to the acceptance of solutions such as OurBigBook.com. To thrive in the competition of academia, those people are amazing at publishing novel results. Explaining to beginners however, not necessarily so.
Phase transition Updated +Created
TODO can anything interesting and deep be said about "why phase transition happens?" physics.stackexchange.com/questions/29128/what-causes-a-phase-transition on Physics Stack Exchange
Quantum algorithm Updated +Created
This is the true key question: what are the most important algorithms that would be accelerated by quantum computing?
Some candidates:
Do you have proper optimization or quantum chemistry algorithms that will make trillions?
Maybe there is some room for doubt because some applications might be way better in some implementations, but we should at least have a good general idea.
However, clear information on this really hard to come by, not sure why.
Ron Maimon Updated +Created
Ron Maimon is a male human theoretical physicist with an all but dissertation started in 1995 at Cornell University[ref][ref].
Figure 1.
Ron Maimon's Physics Stack Exchange profile picture
. Source.
Ron is mostly known for simultaneously:
Ron seems to share a few philosophies which Ciro greatly agrees with as part of Cirism, which together with his knowledge of physics, make Ciro greatly respect Ron. Such philosophies include:
However he also subscribes to some theories which Ciro Santilli considers conspiracy theories, e.g. his ideas about the Boston Marathon bombing that got him banned from Quora (a ban which Ciro strongly opposes due to freedom of speech concerns!), but the physics might be sound, Ciro Santilli does not know enough physics to judge, but it often feels that what he says makes sense.
chat.stackexchange.com/transcript/message/7104585#7104585 mentions that he was at Cornell University and did all but dissertation, but he mentions that he was still self-taught:
Eugene Seidel: On your personal info page you write that you are not a physics Ph.D. but does that mean you were a physics undergrad in college then went to grad school and finished ABD... or are you entirely self taught?
Ron Maimon: ABD. I am self- taught though, I only went to school for accreditation. I had a thesis worth of work at the time I left grad-school,
Eugene Seidel: ok thanks
Ron Maimon: I was just kind of sickened by academic stuff that was going on--- large extra dimensions were popular then.
Eric Walker: Anyway, thanks Ron -- I'll get back to you with more questions soon, I'm sure.
Ron Maimon: Also I was at Cornell, my advisor left for Cincinnatti, and I was not in very good standing there (I was kind of a jerk, as I still am). Some friends wanted to start a biotech company called "Gene Network Sciences", and I joined them.
This is corroborated e.g. at: web.archive.org/web/20201226171231/http://pages.physics.cornell.edu/~gtoombes/Student_Index.html (original pages.physics.cornell.edu/~gtoombes/Student_Index.html down as of 2023).
At youtu.be/ObXbKbpkSjQ?t=2454 from Video 1. "Ron Maimon interview with Jeff Meverson (2014)" he mentions his brother is a professor. At physics.stackexchange.com/questions/32382/could-we-build-a-supercomputer-out-of-wires-and-switches-instead-of-a-microchip confirms that his brother's name is "Gaby Maimon", so this neuroscience professor at the Rockerfeller University is likely him: www.rockefeller.edu/our-scientists/heads-of-laboratories/985-gaby-maimon/. Looks, age, location and research interest match.
Bibliography:
  • gmachine1729.livejournal.com/161418.html Ron Maimon answers about physics and math on Quora (part 1) by Sheng Li (2020) contains a selection of some amazing Ron Maimon posts
  • www.reddit.com/r/RonMaimon/ someone made a Reddit for him. Less than 100 users as of 2022, but has potential.
  • some Quora threads about him, oh the irony:
    • www.quora.com/Is-Ron-Maimon-actually-a-pioneer-or-a-jest
    • www.quora.com/Are-Ron-Maimons-answers-on-mathematics-physics-and-computer-science-factually-correct
    • www.quora.com/What-do-people-think-of-Ron-Maimons-paper-Computational-Theory-of-Biological-Function-I
    • www.quora.com/Who-is-Ron-Maimon/answer/Ron-Maimon
      I'm a physics grad school drop-out working in theoretical biology but I still do physics when I get a chance, but not right now because I am in a middle of a project to understand the properties of a certain virus as completely as possible.
      Also in a comment he explains something to a now deleted comment, presumably asking why he dropped out of grad school, and gives a lot more insight:
      It's a complicated boring story.
      I dropped out mainly to do biology with friends at a startup, because I figured out how you're supposed to do theory in biology, but also I truly believe it was next to impossible for me to get a degree without selling out, and I would rather be shot than write a paper with an idea I don't believe.
      My grad school phase was a disaster. I first worked for Eric Siggia, but I got away because he had me do something boring and safe, I figured I have only a limited number of years before I turn 30 and my brain rots, and I wasn't going to sell out and do second-rate stuff. I found a young guy at the department doing interesting things (Siggia was also doing interesting things, like RNA interactions, he just wouldn't assign any of them to ME), this was Philip Argyres, and got him to take me. Argyres wanted me to work on large-extra dimensions (this was 1998), but I made it clear to him that I would rather be boiled in oil. I worked a little bit on a crappy experimental setup that didn't work at all, because I didn't know enough about electromagnetic screening nor about how to set up experiment. But EVERYONE LOVED IT! This is also how I knew it was shit. Good work is when everyone hates it. But I learned Lifschitz's ideas for quantum electrodynamics in media from this project.
      Me and every competent young person in high-energy physics knew large extra dimensions was a fraud on the day it came out, and I had no intention of doing anything except killing the theory. Once Wikipedia appeared, I did my best to kill it by exposing it's charlatanry on the page for large extra dimension. That was in 2005 (after getting fired from the company), and from this point onward large-extra-dimensions lost steam. But I can't tell how much of this was my doing.
      Argyres liked N=2 theory, and we did something minor in N=2 SUSY models around 2000, but I was bogged down here, because I was trying to do Nicolai map for these, and it ALMOST worked for years, but it never quite worked. But I knew from the moduli interpretation and Seiberg-Witten solution that it must work. If I live long enough, I'll figure it out, I am still sure it isn't hard. But this was the link to statistical stochastic models, the work I was doing with Jennifer Schwarz, and I wanted to link up the two bodies of work (they naturally do through Nicolai map).
      But I had my own discovery, the first real discovery I made, in 1999, this thing that I called the mass-charge inequality, what Vafa and Motl called "the weakest-force principle" when they discovered it in 2006. It was swampland, and Vafa hadn't yet begun swampland. My advisor didn't believe my result was correct, because he saw me say many stupid things before this. So he wouldn't write it or develop it with me (but I had read about Veltman telling 'tHooft he couldn't publish the beta-function, I knew Argyres was wrong about this)
      Anyway, Argyres left for Cincinnatti in 2000, and I joined the company then. I was in the company until january 2005. Then they fired me, which was ok, by then it was a miserable hell-hole full of business types.
      I discovered Wikipedia, and started killing large extra dimensions. I wanted to finish my thesis, and some people agreed to help me do this, but I had told myself "no thesis until you get the Nicolai map sorted out" and I never did. I worked with Chris Henley a little bit, who wanted me to do some stuff for him, and I discovered an interesting model for high-Tc, but Henley said it was out of fasion, and nobody would care, even though I knew it was the key to the phenomenon (still unpublished, but soon).
      This was 2008-2009, and I became obsessed with cold fusion, so Henley dropped me, as I had clearly gone crazy. I developed the theory of cold fusion during the last weeks of working for Henley. Then I dropped out for good.
      Honestly, by the time I was gone, I realized that the internet would make a degree counterproductive, because I knew I had better internet writing skills than any of the old people, I was a Usenet person. Online, the degrees and accreditation were actually a hinderance. So by this point, I secretly preferred not to have a PhD, because I knew I was good at physics, and I could attack from the outside and win. It's not too hard if you know the technical material.
      The only problem is that I was unemployed and isolated in Ithaca for about 7 years after having gone through my first productive phase. But I developed the cold-fusion ideas in this period, I learned a lot of mathematics, and I developed a ton of biology ideas that are mostly unpublished, but will be published soon. It astonished people that I could have no degree and be unemployed and have such a sky-high ego. The reason is that I could evaluate my own stuff, and I liked it!
Backlinks:
Video 1.
Ron Maimon interview with Jeff Meverson (2014)
Source. Ripped from Jeff's "Quoracast": player.fm/series/quoracast-podcast/ron-maimon-truther Ron mentions he was an early-Usenet user. Key points:
Spin number of a field Updated +Created
Physics from Symmetry by Jakob Schwichtenberg (2015) chapter 3.9 "Elementary particles" has an amazing summary of the preceding chapters the spin value has a relation to the representations of the Lorentz group, which encodes the spacetime symmetry that each particle observes. These symmetries can be characterized by small integer numbers:
Uncertainty principle Updated +Created
The wave equation contains the entire state of a particle.
From mathematical formulation of quantum mechanics remember that the wave equation is a vector in Hilbert space.
And a single vector can be represented in many different ways in different basis, and two of those ways happen to be the position and the momentum representations.
More importantly, position and momentum are first and foremost operators associated with observables: the position operator and the momentum operator. And both of their eigenvalue sets form a basis of the Hilbert space according to the spectral theorem.
When you represent a wave equation as a function, you have to say what the variable of the function means. And depending on weather you say "it means position" or "it means momentum", the position and momentum operators will be written differently.
Furthermore, the position and momentum representations are equivalent: one is the Fourier transform of the other: position and momentum space. Remember that notably we can always take the Fourier transform of a function in due to Carleson's theorem.
Then the uncertainty principle follows immediately from a general property of the Fourier transform: en.wikipedia.org/w/index.php?title=Fourier_transform&oldid=961707157#Uncertainty_principle
In precise terms, the uncertainty principle talks about the standard deviation of two measures.
We can visualize the uncertainty principle more intuitively by thinking of a wave function that is a real flat top bump function with a flat top in 1D. We can then change the width of the support, but when we do that, the top goes higher to keep probability equal to 1. The momentum is 0 everywhere, except in the edges of the support. Then:
  • to localize the wave in space at position 0 to reduce the space uncertainty, we have to reduce the support. However, doing so makes the momentum variation on the edges more and more important, as the slope will go up and down faster (higher top, and less x space for descent), leading to a larger variance (note that average momentum is still 0, due to to symmetry of the bump function)
  • to localize the momentum as much as possible at 0, we can make the support wider and wider. This makes the bumps at the edges smaller and smaller. However, this also obviously delocalises the wave function more and more, increasing the variance of x