Advanced quantum mechanics by Freeman Dyson (1951) Updated +Created
Lecture notes that were apparently very popular at Cornell University. In this period he was actively synthesizing the revolutionary bullshit Richard Feynman and Julian Schwinger were writing and making it understandable to the more general physicist audience, so it might be a good reading.
We shall not develop straightaway a correct theory including many particles. Instead we follow the historical development. We try to make a relativistic quantum theory of one particle, find out how far we can go and where we get into trouble.
Oh yes, see also: Dirac equation vs quantum electrodynamics.
Computer security researcher Updated +Created
Ciro Santilli found out that he likes computer security researchers and vice versa.
It's a bit the same reason why he likes physicists: you can't bullshit with security.
You can't just talk nice and hope for people to belive you.
You can't not try to break things and just keep everyone happy in their false illusion of safety.
You can't do a half job.
If you do any of that, you will get your ass handed to you in a little gift bag.
David Tong Updated +Created
A charismatic, perfect-English-accent (Received Pronunciation) physicist from University of Cambridge, specializing in quantum field theory.
He has done several "vulgarization" lectures, some of which could be better called undergrad appetizers rather, a notable example being Video "Quantum Fields: The Real Building Blocks of the Universe by David Tong (2017)" for the prestigious Royal Institution, but remains a hardcore researcher: scholar.google.com/citations?hl=en&user=felFiY4AAAAJ&view_op=list_works&sortby=pubdate. Lots of open access publications BTW, so kudos.
The amount of lecture notes on his website looks really impressive: www.damtp.cam.ac.uk/user/tong/teaching.html, he looks like a good educator.
David has also shown some interest in applications of high energy mathematical ideas to condensed matter, e.g. links between the renormalization group and phase transition phenomena. TODO there was a YouTube video about that, find it and link here.
Ciro Santilli wonders if his family is of East Asian, origin and if he can still speak any east asian languages. "Tong" is of course a transcription of several major Chinese surnames and from looks he could be mixed blood, but as mentioned at www.ancestry.co.uk/name-origin?surname=tong it can also be an English "metonymic occupational name for a maker or user of tongs". After staring at his picture for a while Ciro is going with the maker of tongs theory initially.
Don't be a pussy Updated +Created
!!! Survivorship bias alert !!!
quoteinvestigator.com/2018/05/07/overcome/
If you want to do something, but you are afraid to do it, then that is likely what you should do.
quoteinvestigator.com/2013/11/08/not-bend/
Don't bend; don't water it down; don't try to make it logical; don't edit your own soul according to the fashion. Rather, follow your most intense obsessions mercilessly.
www.goodreads.com/quotes/50458-whatever-you-re-meant-to-do-do-it-now-the-conditions Doris Lessing:
Whatever you're meant to do, do it now. The conditions are always impossible.
For example, when Ciro Santilli was deciding what to do in university, he wanted mostly to do pure physics.
But because he was afraid he was going to die poor and unemployed because of that, he picked engineering instead.
That was a mistake.
His family was not even poor. He was young and did not have a family to support. His father even told him: "do whatever the fuck you want, we support your decision".
But he was a coward.
It was also in part because a physicist uncle which he respected suggested that as an engineer Ciro might be able to make useful contributions to tooling required by physics. When Roberto Salmeron died in 2020, Ciro's friends shared this 2013 video interview with the late professor, where he explains he first went to the University of São Paulo to study engineering (like Ciro), but then fell for his passion for physics (like Ciro?), his first task being to build a Geiger counter, thus explaining the likely origin of the uncle's theory. But who knows, maybe he was right. Maybe Ciro's OurBigBook.com will become huge and help a lot of people, and it might not have had Ciro not done engineering and learnt programming. Destiny operates in weird ways sometimes.
Furthermore, while in University, Ciro learnt about the molecular Sciences Course of the University of São Paulo, a fantastic sounding full time course that any student could transfer to called that teaches various natural sciences topics which Ciro loves (Mathematics, Physics, Chemistry, Biology) and which students from the entire university can apply to transfer to only after joining the university, with the guarantee that they can go back to their original courses if they didn't adapt to the new course.
But did Ciro do it? Nope, he remained an even larger coward.
Had he studied more sciences, he might have been happier, and might have had greater achievements later in life, in particular when he went to École Polytechnique.
Maybe not, but now this doubt will never leave his mind until the final day.
Similar thoughts crossed his mind when he started his campaign for freedom of speech in China, but this time he had learnt the lesson, and went for it, and it felt very good.
If you have a day job, but also have a dream, and want to keep the day job for a reason, try to reserve the time of the day that your brain works best before or after work for your dream: do one cool thing every day.
Companies can help you grow because you see real problems from within them, but their end goal is to consume you as much as possible. Don't let that happen. Invest part of what you gain, in yourself. www.outsideonline.com/outdoor-adventure/paradox-going-outside/ The Paradox of Going Outside by James Somers (2012) puts it incredibly well:
I work, for instance, as a Web developer. It's a very good job. Our office is a block south of Union Square, a 12-minute commute from my apartment. We're served breakfast every morning. Our kitchen is stocked with "provisions" of organic beef jerky, coconut water, craft beers, chips, and two restaurant-class espresso machines. We have two ping pong tables and buckets of 3-star ping pong balls. (A new office manager bought "1-stars" once and some of the guys protested by crushing them.) We work on 4-cored Apple Mac computers with dual monitors. We have an unmolested hour for lunch, 10-minute breaks in the morning and afternoon, and a "do not disturb" policy past the working hours. We even have a specific email address where employees can ask for free things: genuine maple syrup, hot chocolate, a $900 chair, a new keyboard. Most of the programmers make six figures, and many of those have only three or four years of experience.
It's impossible to say so without sounding like the spokesperson for Entitlement itself but working there is still sort of soul-crushing. It's soul-crushing in the way that any job that doesn't command your full passionate attention must be. What happens is that I will be in my chair in the early afternoon and I will accidentally step out of myself and all I'll see is time passing, nine-hour parcels of healthy consciousness forever being packed away as the user experience of clerical workers or consumers or whoever gets marginally better; and I'll end up thinking that this enterprise of mine is not so much creative but bureaucratic, that what I've gotten good at is reading the instruction manuals of other people, finding my way around their insignificant warrens. And in those moments the whole business will seem to me like kind of a tragic waste.
Other quotes:
  • Healthy Disregard For The Impossible
    is a phrase Sergey Brin uses. The Google Story claims he picked that up from academia, and quotes this from a september 2003 talk in an Israeli elite high school.
  • quoteinvestigator.com/2014/05/29/find-love/
    Find What You Love and Let It Kill You
  • Cute boy things by Caroline Ellison:
    if you are a boy with the confidence to advocate for unconventional ideas and take actions based on them you are valid
  • How can I be as great by Justine Musk:
    rock the boat
  • From the 1922 poem Portuguese Sea by famous Portuguese poet Fernando Pessoa, which gets drilled into the head of every Brazilian high school student:
    He who wants to pass beyond the Bojador
    Must go beyond pain.
    Quem quer passar além do Bojador
    Tem que passar além da dor.
  • Translation of a poem by Muhammad Iqbal TODO date:
    Said one gazelle to another, "I will Take shelter in the harem from now on; For there are hunters at large in the wild, And there is no peace here for a gazelle. From fear of hunters I want to be free. O how I long for some security."
    His friend replied, "Live dangerously, my Wise friend, if it is life you truly seek. Like a sword of fine mettle hurl yourself Upon the whetting-stone; stay sharp thereby. For danger brings out what is best in you: It is the touchstone of all that is true."
    One is reminded of As iron sharpens iron, so one person sharpens another.
  • "NPC life" as a way to refer to a soul crushing job
    • twitter.com/0xTenkito/status/1775167216641548732, a cryptocurrency investor says:
      If my portfolio goes to 0 and I lose everything, I will continue with my normal life, in a 9-5 job, and I will try to invest again as soon as I get a financial cushion again.
      I have nothing to lose, I can always live the standard NPC life, but to escape from it you have to take risks and take risks.
      However there is one thing to lose, if you do safer investments and don't lose everything, then you might be able to retire earlier.
    • archive.ph/mlaLK
Don't be a pussy. Be a Based God
Figure 1.
Dilbert "A small brain irrationally puts more weight on a small loss than on a huge opportunity" cartoon (2000)
Source.
Figure 2.
Jake Likes Onions "Slowly" cartoon
. Source. This is what trying to reach a dream part time feels like. The cartoon reads: "The tiger pursues its prey. Slowly. The human pursues its life goals. Slowly. Very slowly.".
Video 1.
Excerpt from the documentary film "Steve Jobs: Secrets of Life" (1994)
Source.
When you grow up you tend to get told that the world is the way it is and your life is just to live your life inside the world. Try not to bash into the walls too much. Try to have a nice family life, have fun, save a little money. That's a very limited life. Life can be much broader once you discover one simple fact: Everything around you that you call life was made up by people that were no smarter than you. And you can change it, you can influence it... Once you learn that, you'll never be the same again.
Of course, survivorship bias alert!
Video 2.
What Would You Do If Money Were No Object by Alan Watts
. Source. Sample transcription: genius.com/Alan-watts-what-if-money-was-no-object-annotated:
What do you desire? What makes you itch? What sort of a situation would you like?
Let's suppose, I do this often in vocational guidance of students, they come to me and say, well, "we're getting out of college and we have the faintest idea what we want to do". So I always ask the question, "what would you like to do if money were no object? How would you really enjoy spending your life?"
Well, it's so amazing as a result of our kind of educational system, crowds of students say well, we'd like to be painters, we'd like to be poets, we'd like to be writers, but as everybody knows you can't earn any money that way. Or another person says well, I'd like to live an out-of-doors life and ride horses. I said you want to teach in a riding school?
Let's go through with it. What do you want to do? When we finally got down to something, which the individual says he really wants to do, I will say to him, you do that and forget the money, because, if you say that getting the money is the most important thing, you will spend your life completely wasting your time. You'll be doing things you don't like doing in order to go on living, that is to go on doing things you don't like doing, which is stupid. Better to have a short life that is full of what you like doing than a long life spent in a miserable way.
And after all, if you do really like what you're doing, it doesn't matter what it is, you can eventually turn it - you could eventually become a master of it. It's the only way to become a master of something, to be really with it. And then you'll be able to get a good fee for whatever it is. So don't worry too much. That's everybody is - somebody is interested in everything, anything you can be interested in, you will find others will.
But it's absolutely stupid to spend your time doing things you don't like, in order to go on spending things you don't like, doing things you don't like and to teach our children to follow in the same track. See what we are doing, is we're bringing up children and educating to live the same sort of lives we are living. In order that they may justify themselves and find satisfaction in life by bringing up their children to bring up their children to do the same thing, so it's all retch and no vomit. It never gets there. And so, therefore, it's so important to consider this question: What do I desire?
Video 3. . Source.
That's the way I live my life, I give it my all. I think that a person should really make up his mind what he wants to do, and when did made up, he cannot fail at it. The basic rule to sucess I think, is when the going gets tough, that is a positive signal to keep chargin'.
Closely echoes Video 2. "What Would You Do If Money Were No Object by Alan Watts". Survivorship bias? Maybe. Beautiful? Unquestionably. So glad he was allowed to upload it officially to YouTube.
Video 4.
Your Life is Your life by Charles Bukowski
. Source.
Charles Bukowski is one of the most hardcore don't be a pussy people ever. It's almost scary. Far beyond Ciro level.
thebestamericanpoetry.typepad.com/the_best_american_poetry/2008/11/the-laughing-he.html
your life is your life
don't let it be clubbed into dank submission.
be on the watch.
there are ways out.
there is light somewhere.
it may not be much light but
it beats the darkness.
be on the watch.
the gods will offer you chances.
know them.
take them.
you can't beat death but
you can beat death in life, sometimes.
and the more often you learn to do it,
the more light there will be.
your life is your life.
know it while you have it.
you are marvelous
the Gods wait to delight
in you.
www.goodreads.com/quotes/39207-if-you-re-going-to-try-go-all-the-way-otherwise
If you're going to try, go all the way. Otherwise, don't even start. This could mean losing girlfriends, wives, relatives and maybe even your mind. It could mean not eating for three or four days. It could mean freezing on a park bench. It could mean jail. It could mean derision. It could mean mockery--isolation. Isolation is the gift. All the others are a test of your endurance, of how much you really want to do it. And, you'll do it, despite rejection and the worst odds. And it will be better than anything else you can imagine. If you're going to try, go all the way. There is no other feeling like that. You will be alone with the Gods, and the nights will flame with fire. You will ride life straight to perfect laughter. It's the only good fight there is.
I have one of two choices - stay in the post office and go crazy... or stay out here and play at writer and starve. I have decided to starve.
Figure 3.
Bukowski kissing his typewriter.
Like Ciro Santilli and his computer!
Video 5.
All adults are bored scene from an Edward Teller, An Early Time
. Source.
Up to the time that I met Klug ([a mathematiciam]), I was sure that all grown ups were people to be pitied. They had to work, they were tired, they were bored with what they were doing. I heard both my parents often complain. Klug was the first man whom I met who most obviously enoyed what he was doing.
But to be fair, being a fucking "genius" might be a requirement to escape that fate!
Figure 4.
Modern Sisyphus by Sephko
. Source.
Video 6.
"I just stopped thinking" scene from Malcolm in the Middle S05E21 "Reese Joins The Army"
. Source. Working in most big companies can feel like this sometimes. We need stronger AI (AGI?) to help wipe out this boredom. A anti-AGI blues moment for you.
Figure 5.
Do epic shit meme
. Source.
Do epic shit
Unless you are too tired, or it costs too much money, in which case, Do affordable shit, and make time for naps
Encyclopedia Britannica Updated +Created
Ciro Santilli is old enough to remember his parents whispering its name with a respectful tone.
Genius: Richard Feynman and Modern Physics by James Gleick (1994) mentions several times how Richard Feynman was a reader of the encyclopedia. E.g. in youtu.be/ivxkd98mDvc?t=50 Richard's sister also talks about it.
Then the Internet came along and killed it.
The motivation model for collaborators was simple: to get famous. To be able to be selected contribute an article meant that you knew something or two! There was some physicist Ciro read the biography of who was really glad to be able to write an article on the encyclopedia after having worshiped it for so long, TODO find the reference.
While this is somewhat a part of Wikipedia motivation, it is much less so because there is no single article authorship. This is something OurBigBook.com aims to improve.
Greek alphabet Updated +Created
Unfortunately, physicists and mathematicians keep using Greek letters in their formulas, so we just have to learn them.
A helpful way to remember is to learn a bit of their history/pronunciation: Section "Historical correspondence between Latin and Greek".
To learn the greek letters if you have a base latin alphabet, you must learn the sound of each letter, and which Latin letters they correspond to.
Symbols that look like Greek letters but are not Greek letters:
Is Ciro Santilli crazy (he is, but for this point specifically), or do many/most Greek letters represent the mouth position used in the pronunciation of the letter?
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).
Julian Schwinger Updated +Created
Extremely precocious, borderline child prodigy, he was reading Dirac at 13-14 from the library.
He started working at night and sleeping during the moring/early afternoon while he was at university.
He was the type of guy that was so good that he didn't really have to follow the university rules very much. He would get into trouble for not following some stupid requirement, but he was so good that they would just let him get away with it.
Besides quantum electrodynamics, Julian worked on radar at the Rad Lab during World War II, unlike most other top physicists who went to Los Alamos Laboratory to work on the atomic bomb, and he made important contributions there on calculating the best shape of the parts and so on.
He was known for being very formal mathematically and sometimes hard to understand, in stark contrast to Feynman which was much more lose and understandable, especially after Freeman Dyson translated him to the masses.
However, QED and the men who made it: Dyson, Feynman, Schwinger, and Tomonaga by Silvan Schweber (1994) does emphacise that he was actually also very practical in the sense that he always aimed to obtain definite numbers out of his calculations, and that was not only the case for the Lamb shift.
Luboš Motl Updated +Created
Matrix mechanics Updated +Created
Published by Werner Heisenberg in 1925-07-25 as quantum mechanical re-interpretation of kinematic and mechanical relations by Heisenberg (1925), it offered the first general formulation of quantum mechanics.
It is apparently more closely related to the ladder operator method, which is a more algebraic than the more analytical Schrödinger equation.
It appears that this formulation makes the importance of the Poisson bracket clear, and explains why physicists are so obsessed with talking about position and momentum space. This point of view also apparently makes it clearer that quantum mechanics can be seen as a generalization of classical mechanics through the Hamiltonian.
QED and the men who made it: Dyson, Feynman, Schwinger, and Tomonaga by Silvan Schweber (1994) mentions however that relativistic quantum mechanics broke that analogy, because some 2x2 matrix had a different form, TODO find that again.
Inward Bound by Abraham Pais (1988) chapter 12 "Quantum mechanics, an essay" part (c) "A chronology" has some ultra brief, but worthwhile mentions of matrix mechanics and the commutator.
Nabla symbol Updated +Created
As if Greek letters weren't enough, physicists and mathematicians also like to make up tons of symbols, some of which look like the could actually be Greek letters!
Nabla is one of those: it was completely made up in modern times, and just happens to look like an inverted upper case delta to make things even more confusing!
Nabla means "harp" in Greek, which looks like the symbol.
Nu (letter) Updated +Created
Why would physicists use a letter such that:
  • the upper case version looks exactly like an upper case N. At least that is the correct pronunciation/name/historical successor of .
  • the lower case version looks exactly like a lower case V
Why? Why?????????
Existing data sources Updated +Created
Some possible/not possible sources that could be used to manually bootstrap content:
Lecture note upload website:
Exams uploads:
Oxford Instruments Updated +Created
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.
Paul Dirac Updated +Created
Eccentric nerdy slow speaking physicist mostly based in University of Cambridge.
Created the Dirac equation, what else do you need to know?!
QED and the men who made it: Dyson, Feynman, Schwinger, and Tomonaga by Silvan Schweber (1994) chapter 1.3 "P.A.M. Dirac and the Birth of Quantum Electrodynamics" quotes Dirac saying how being at high school during World War I was an advantage, since all slightly older boys were being sent to war, and so the younger kids were made advance as fast as they could through subjects. Exactly the type of thing Ciro Santilli wants to achieve with OurBigBook.com, but without the need for a world war hopefully.
Dirac was a staunch atheist having said during the Fifth Solvay Conference (1927)[ref]:
If we are honest - and scientists have to be - we must admit that religion is a jumble of false assertions, with no basis in reality. The very idea of God is a product of the human imagination. It is quite understandable why primitive people, who were so much more exposed to the overpowering forces of nature than we are today, should have personified these forces in fear and trembling. But nowadays, when we understand so many natural processes, we have no need for such solutions. I can't for the life of me see how the postulate of an Almighty God helps us in any way. What I do see is that this assumption leads to such unproductive questions as why God allows so much misery and injustice, the exploitation of the poor by the rich and all the other horrors He might have prevented. If religion is still being taught, it is by no means because its ideas still convince us, but simply because some of us want to keep the lower classes quiet. Quiet people are much easier to govern than clamorous and dissatisfied ones. They are also much easier to exploit. Religion is a kind of opium that allows a nation to lull itself into wishful dreams and so forget the injustices that are being perpetrated against the people. Hence the close alliance between those two great political forces, the State and the Church. Both need the illusion that a kindly God rewards - in heaven if not on earth - all those who have not risen up against injustice, who have done their duty quietly and uncomplainingly. That is precisely why the honest assertion that God is a mere product of the human imagination is branded as the worst of all mortal sins.
Video 1.
Paul Dirac and the religion of mathematical beauty by Royal Society (2013)
Source.
Pick few good bets and invest enough on them Updated +Created
Poor countries don't have a lot of money.
Therefore, you have to pick a few key the next big thing deep tech bets, and invest on those enough.
These have to be few, because your country is poor, and so you can't invest on everything.
Therefore, the bets have to be well selected, because it is useless to make several insufficient investments: you have to pick a few ones, and put enough time and money into each one of them for them to stand any chance. These bets should be made and reevaluated on 5/10 year horizons.
The key things that you have to select are:
  • which poor students you will bet on educating. Since you can't give amazing education to everyone, you have to select the most promising poor students somehow, and give those free amazing learning conditions: free gifted education
  • which ares to focus on. Ciro believes that molecular biology technologies and quantum computing would be good bets. Focusing on the previous next big things, e.g. classic computers, is always a losing bet on average
And then you only tax those companies heavily when the start to bring in real money. These are startups remember! You only need 5 unicorns a year to call it a success. And countries should not be greedy and invest through equity, but rather recoup their investment through taxation alone.
Ciro's second removed uncle, who was a physicist at the University of Campinas, one of the best universities in the country, told him an anecdote. He had moved from fusion energy research to solar cell research. At some point, there was a research lab that needed 10 million to buy a machinery critical for their experiment. They asked and asked, and finally the government gave them only 2 million. So in the end they spent those 2 million in random ways, but of course did not achieve their research goal and no money came out of it.
He also explained how as a result of the insufficient investments, he felt clearly that some of the semiconductor production facilities related to solar power he saw simply were not able to control the production process adequately to produce consistent silicon. As a result, everything failed sooner or later as people found more and more bugs that they did not have the time to solve.
Another key investment is enticing back experienced exchange-students who have learnt new techniques to be heads of laboratory/founders to back in your country.
A fantastic initiative from Brazil for example is BRASA, which aims to put together Brazilian exchange students to make a difference back in Brazil.
Do not try to forbid external companies from selling in your country. Instead, fund your own companies to be able to fight the external market off. And if they can't, let them die and pick a different bet. Video "How Taiwan Created TSMC by Asianometry (2020)" has a good mention. Protectionism is something that Brazil notably tried to do, and look at what it led, not a single international success.
Why do symmetries such as SU(3), SU(2) and U(1) matter in particle physics? Updated +Created
Physicists love to talk about that stuff, but no one ever has the guts to explain it into enough detail to show its beauty!!!
Perhaps the wisest thing is to just focus entirely on the part to start with, which is the quantum electrodynamics one, which is the simplest and most useful and historically first one to come around.
Perhaps the best explanation is that if you assume those internal symmetries, then you can systematically make "obvious" educated guesses at the interacting part of the Standard Model Lagrangian, which is the fundamental part of the Standard Model. See e.g.:
One bit underlying reason is: Noether's theorem.
Notably, axelmaas.blogspot.com/2010/08/global-and-local-symmetries.html gives a good overview:
A local symmetry transformation is much more complicated to visualize. Take a rectangular grid of the billiard balls from the last post, say ten times ten. Each ball is spherical symmetric, and thus invariant under a rotation. The system now has a global and a local symmetry. A global symmetry transformation would rotate each ball by the same amount in the same direction, leaving the system unchanged. A local symmetry transformation would rotate each ball about a different amount and around a different axis, still leaving the system to the eye unchanged. The system has also an additional global symmetry. Moving the whole grid to the left or to the right leaves the grid unchanged. However, no such local symmetry exists: Moving only one ball will destroy the grid's structure.
Such global and local symmetries play an important role in physics. The global symmetries are found to be associated with properties of particles, e. g., whether they are matter or antimatter, whether they carry electric charge, and so on. Local symmetries are found to be associated with forces. In fact, all the fundamental forces of nature are associated with very special local symmetries. For example, the weak force is actually associated in a very intricate way with local rotations of a four-dimensional sphere. The reason is that, invisible to the eye, everything charged under the weak force can be characterized by a arrow pointing from the center to the surface of such a four-dimensional sphere. This arrow can be rotated in a certain way and at every individual point, without changing anything which can be measured. It is thus a local symmetry. This will become more clearer over time, as at the moment of first encounter this appears to be very strange indeed.
so it seems that that's why they are so key: local symmetries map to the forces themselves!!!
axelmaas.blogspot.com/2010/09/symmetries-of-standard-model.html then goes over all symmetries of the Standard Model uber quickly, including the global ones.