11 ms·

A 9-line summary of textbook physics

247 points by PrettyPebble 5y ago

deleted 5y ago
[deleted]
alasdair_ 5y ago
“ bosons, quarks and leptons – with their charges and properties make up everything.” The empty space between the bosons, quarks and leptons is not made up of any of these particles, yet the space ‘exists’ - without it, everything in the universe would just be a big clump.
- PrettyPebble 5y ago
  In general relativity, space is not a thing.
  - alasdair_ 5y ago
    I meant to thank you for this comment earlier - it’s led to a whole bunch of interesting stuff I did not know.
    - PrettyPebble 4y ago
      The 9 line summary is now also available as a preprint: https://www.motionmountain.net/9lines.pdf https://www.motionmountain.net/9lines.pdf
PrettyPebble 5y ago
Fun fact: all physics experiments ever made can be described by 9 lines, without any deviation between theory and observations. The 9 lines are sufficient to describe quantum physics and gravity. It seems that the 9 lines even contain all (update: natural) sciences, not only physics. Finding an exception to the 9 lines will make you famous. So will the discovery of a 10th line. Thousands of researchers work towards these dreams, but none succeeded yet. A few additional fun facts on https://www.motionmountain.net/9lines.html https://www.motionmountain.net/9lines.html
- criticaltinker 5y ago
  This is satire right? You might be getting downvotes because it’s not clear if you’re serious, and those claims seem quite ridiculous at face value.
  - not_kurt_godel 5y ago
    It's essentially paraphrased from the OP. Why OP is getting upvoted, I do not know.
  - PrettyPebble 5y ago
    What is ridiculous?
    - _Nat_ 5y ago
      The 9-lines thing. May've just drawn a circle and claimed that it describes all of science.
      - PrettyPebble 5y ago
        If the 9 lines are wrong, just show it... Thousands of scientists are trying the same since 50 years.
        _Nat_ 5y ago
        It's not that they're "wrong" so much as that they're incoherent and largely non-sense. Sorry if that seems harsh, just.. this looks like someone's having some sort of crisis. It's worrisome.
        PrettyPebble 5y ago
        No, it is fun! The scientists who are looking for exceptions to the standard model and to general relativity since 50 years are having a crisis at present, as often told. The 9 lines imply all equations of physics. Every Lagrangian of physics is included. The lines are also coherent: none contradicts another. They are complementary: the cover all observations and all fields of physics. No field of physics is left out. The lines are also correct: every calculation fits with observations withing measurement accuracy, since the standard model (with neutrino masses and PMNS mixing) and general relativity exist.
humanistbot 5y ago
Physics maybe, but all sciences? This is is some serious physics determinism --- obligatory XKCD: https://xkcd.com/435/ https://xkcd.com/435/
- PrettyPebble 5y ago
  You are right - The text should say all "natural sciences".
  - IgorPartola 5y ago
    The unnatural sciences are where the fun really begins.
    - PrettyPebble 5y ago
      True!
- MauranKilom 5y ago
  Funny enough, there's an even more related xkcd for this page: https://xkcd.com/2034/ https://xkcd.com/2034/
  - PrettyPebble 5y ago
    Good one!
- nayuki 5y ago
  > The nine lines contain physics, chemistry, material science, biology, medicine, geology, astronomy, engineering and computer science. I have doubts that these 9 lines describe computer science. As I interpret it, computer science is founded on pure mathematics and is not a physical or empirical science. Computer science deals with perfect abstract mathematical objects like numbers, sets, quantification, recursion, infinities, etc.
  - 5y ago
Reventlov 5y ago
I opened a volume of the books linked in the page, and found this: « Learning allows us to discover what kind of person we can be. Learning widens knowledge, improves intelligence and provides a sense of achievement. Therefore, learning from a book, especially one about nature, should be efficient and enjoyable. Avoid bad learning methods like the plague! Do not use a marker, a pen or a pencil to highlight or underline text on paper. It is a waste of time, provides false comfort and makes the text unreadable. And do not learn from a screen. In particular, never, ever, learn from the internet, from videos, from games or from a smartphone. Most of the internet, almost all videos and all games are poisons and drugs for the brain. Smartphones are dispensers of drugs that make people addicted and prevent learning. Nobody putting marks on paper or looking at a screen is learning efficiently or is enjoying doing so. » My sarcasm detector is broken, is that sarcasm ?
- irrational 5y ago
  Yeah, this is clearly BS. Recently I changed the turn switch on my car. How did I learn how to do that? From the Internet, specifically from watching videos. It was easily the most efficient way to learn.
- dr_dshiv 5y ago
  Which book?
  - Reventlov 5y ago
    I was interested in electromagnetism, so https://www.motionmountain.net/motionmountain-volume3.pdf https://www.motionmountain.net/motionmountain-volume3.pdf, in the « Advice for learners » section of the introduction. I reckon this is the same text in every volume.
    - dr_dshiv 5y ago
      Yeah, not sarcasm. But contradictory for a free online downloadable. I do like the next advice, to be able to say the ideas in your own words. Maybe the point (which seems very overstated) is that highlighting and videos create the sensation of knowing, but not necessarily the knowing.
MauranKilom 5y ago
> About 18 particles > About 25 numbers Excellent science here!
- rwoerz 5y ago
  Sounds like my tax declaration... where they ask for the number of my children.
- threatripper 5y ago
  You can't contradict this. Nature is perfect.
- BearOso 5y ago
  Observation is part of science, but we're also limited by it. There's a lot of deeper workings that we just can't get at yet, maybe ever.
- PrettyPebble 5y ago
  Improved the first. The second is ok.
- mhh__ 5y ago
  Obviously this won't help you find the particles but this seriously isn't far off capturing how shocking symmetry groups are as a tool for building theories in particle physics. The fact that you can reduce so much physics down to some invariance is very spooky.
  - PrettyPebble 5y ago
    Or just beautiful!
- 7373737373 5y ago
  https://math.ucr.edu/home/baez/constants.html https://math.ucr.edu/home/baez/constants.html the mass of the up quark the mass of the down quark the mass of the charmed quark the mass of the strange quark the mass of the top quark the mass of the bottom quark 4 numbers for the Kobayashi-Maskawa matrix the mass of the electron the mass of the electron neutrino the mass of the muon the mass of the mu neutrino the mass of the tau the mass of the tau neutrino 4 numbers for the Pontecorvo-Maki-Nakagawa-Sakata matrix the mass of the Higgs boson the expectation value of the Higgs field the U(1) coupling constant the SU(2) coupling constant the strong coupling constant the cosmological constant
mhh__ 5y ago
The 9 equations aspect is pretty pointless but the chapters on the right hand side could be ok. One of the things that makes physics different to most subjects is that we can make an explicit goal of being smug and rederiving the laws of physics from the simplest possible principles. I think the book seems to do this, but just summarizing like done on this webpage is a bit daft.
- ravi-delia 5y ago
  I think the way these are phrased do a better job expressing the "vibe", for lack of a better word, of our current understanding. That the particles and constants are declared by fiat, with behavior constrained by simpler laws, is an understanding I didn't come to until I took a QFT course. The physicist's God is as concerned with forbidding seemingly pointless things as the biologist's God is with beetles.
  - mhh__ 5y ago
    Vibe is not a bad word to use in these situations.
  - whimsicalism 5y ago
    It is interesting that we humans have so much difficulty breaking away from anthropomorphizing.
    - roywiggins 5y ago
      If large chunks of our brainpower are actually hardwired to think in terms of other humans¹, anthropomorphism might just be a strategy to recruit those hardwired systems into helping out with other tasks. ¹ this may not be true
    - ravi-delia 5y ago
      And yet the vibe persists! Presumably it's due to low-level patterns you subconsciously pick up on, but much of the much-discussed physicist-intuition comes from knowing how the universe "likes" do do things. There's a similar thing in math, with many of the greats having just a few tricks they used over and over to great effect in any number of fields. I guess we're used to dealing with people, so the pattern is expressed as a preference (which does double duty encoding that it's not an absolute law).
arcbyte 5y ago
I think the future of physics is in Energy Wave Theory. Maybe not that theory exactly, but a similar theory going back to the idea of some kind of ether in which waves propagate.
jkuria 5y ago
Social 'scientists'? Your turn :)
- humanistbot 5y ago
  The natural sciences, the so-called "hard sciences" are really the easy ones, because what they study doesn't have free will. The truly difficult sciences are of human behavior.
- smoyer 5y ago
  You're assuming free will isn't some complex-looking behavior driven by quantum uncertainty. In the multiverse, every social scientist has many clones who's studies refute their work!
  - marginalia_nu 5y ago
    Even if that is so, a quantum description of human behavior is fairly useless in terms of practical application. How does knowledge of the standard model cure the infirm, prevent crime, and so forth?
    - Itti 5y ago
      When we exhibit behaviors. Our context is derived from our visual/auditory field processing from birth. Those waves implant magnetic field signatures on our neurotransmitter morphologies. We are almost explicitly operational in quantum activity. Many if not all disabilities or health complications are resonant to your mind body homeostasis. Challenge the quantum spectral development process of a person you solve the aforementioned issues.
      - marginalia_nu 5y ago
        Right, but how is this fact in any way helpful in dealing with the phenomenal world?
        5y ago
la64710 5y ago
Why do the first chapters of all physics textbook ONLY talk about Greek philosophers and scientists and NEVER talk about contribution to Science from eastern civilization like India and China ? These civilizations have a very rich heritage and astounding contribution to many underlying scientific philosophies. Yet generation after generation of writers ignore them and it is sad to see that being true even today. It is time that this is changed.
- deadbeeves 5y ago
  Off the top of my head, I can name three things from either China or India that are science-related: the positional numbering system (and zero), the Chinese remainder theorem, and gunpowder. What am I missing that's very important yet rarely mentioned?
  - fooker 5y ago
    India: quite a bit of astronomy and geometry. Also logic, philosophy and linguistics if you want to include them in the science list. China: chemistry and metallurgy. Indian science took a weird turn towards metaphysics and mystical stuff once the priests started playing a fundamental role in education.
- PrettyPebble 5y ago
  The Indian number system is treated in detail. Indian mathematicians are mentioned and cited.
  - la64710 5y ago
    Good to know that , I did not go past the first few pages. Now some interesting contribution from India that I never heard of before https://www.manchester.ac.uk/discover/news/indians-predated-newton-discovery-by-250-years/ https://www.manchester.ac.uk/discover/news/indians-predated-... https://www.britannica.com/biography/Aryabhata-I https://www.britannica.com/biography/Aryabhata-I But I doubt that many conventional physics textbook will not even mention these and others. The writers are not to blame , but no doubt the ignorance is an unfortunate reality.
323 5y ago
I've read a few times that you can derive the Maxwell equations from knowing that U(1) exists, as this article implies, that every point in space has (among other things) the symmetry of a circle. But I've never seen this derivation. I assume it's either trivial or too complicated. Anyone has a link or thoughts on this?
- unicas 5y ago
  There are plenty of so called "derivations of Maxwell equations", however, I would not claim that they were based on U(1) necessarily. IMO ME are just the integrability conditions for any conserved quantity (continuity equation): take a generic three-form in R^4, then dJ=0 => J=dF. F has six components corresponding to two vectofields in R^3 which depend on the fourth coordinate and satisfy the div and curl relations as in ME ;)
  - hither_shores 5y ago
    U(1) symmetry (R also works in a classical setting: it's the Lie algebra that matters) is exactly how you get a "generic three-form" to drop out of the action.
- podiki 5y ago
  In short, if you impose a U(1) symmetry on your Lagrangian, you get electromagnetism. Basically you do the action of U(1) and enforce that the equation of motion does not change. That gives you the electromagnetic force (a photon). Putting in some of those keywords will find plenty of detailed notes online, like http://www.physics.usu.edu/torre/Classical_Field_Theory/Lectures/04_EM.pdf http://www.physics.usu.edu/torre/Classical_Field_Theory/Lect... or more quick overviews like https://mugndonut.wordpress.com/2018/03/31/symmetries-yield-conserved-quantities/ https://mugndonut.wordpress.com/2018/03/31/symmetries-yield-...
- gus_massa 5y ago
  I wrote an ELI25 explanation in a comment a few months ago, and I'll copy it here: In quantum mechanics the wave function Ψ is has complex values. If you multiply everything in the universe by -1, nothing changes because all the physical results use ΨΨ* (where * is the complex conjugation). You can also multiply everything by i or -i. Moreover by any other complex number of modulo 1 because ΨΨ* does not change. (The technical term for this is U(1) global gauge symmetry.) But you can be more ambitious and want to multiply each point of the universe by a different complex number of modulo 1. ΨΨ* does not change but the derivatives of Ψ change and they are also important. (When you use the same complex number everywhere, the derivatives is just a multiple of the original derivative. When you use a different number in each point, it changes.) The only way to fix the problem with the derivative is to add a new field A. When you and multiply each point of the universe by a different complex number of modulo 1, then A changes in a simple to calculate but not obvious way. The change in A fix the problem with the derivatives of Ψ. So now the equations of the universe with Ψ and A don't change when you make this change. (The technical term for this is U(1) local gauge symmetry.) When you write carefully how a universe like this look like, the new field A is electromagnetism. (Actually, you can get the electric field and magnetic field using the derivatives of A.) Too many more details in https://en.wikipedia.org/wiki/Quantum_electrodynamics#Mathematical_formulation https://en.wikipedia.org/wiki/Quantum_electrodynamics#Mathem... > I assume it's either trivial or too complicated. It's trivial once you have 3 or 4 years studding Physics, but you will never understand how it is related to the magnets in your refrigerator. [There are like 5 simplification steps between U(1) and magnets in the refrigerator. Each one makes sense, but I can't see all of them together in my head.]
graderjs 5y ago
s/nature/the simulation/g 1. Total compute capacity is limited and redistributes toward areas of high activity. 2. Processor speed is limited. 3. Mutations are sensibly constrained to prevent overflow. 4. Smallest addressable memory space. 5. No process is ever fully idle. 6. IPC is done using circles. 7. The kernel however operates at the level of spheres, and pointers to pointers to pointers to spheres. 8. There's roughly 18 niceness levels, but rumors are there are a couple more. 9. About 25 programmers worked on the project and at the end each one got to pick a nothing-up-my-sleeve number. Some say there are Easter eggs hidden there yet to be discovered.
- KineticLensman 5y ago
  Religion: "God did it" Simulation hypothesis: "God did it, with a computer"
  - qiskit 5y ago
    Simulation hypothesis: God did the first simulation with a computer, everything else is a simulation of a simulation.
    - kleene_op 5y ago
      Simulation hypothesis: It's simulations all the way down. No gods in sight.
- DangitBobby 5y ago
  It makes intuitive sense to me that computers are physically constrained in all of the ways (and more) that the universe itself is physically constrained. I don't know why the inclination is to take these fundamental constraints and then say "the universe is in a computer" instead of saying "the computer is in a universe".
gpvos 5y ago
> This pdf file is licensed under the Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 Germany Licence, whose full text can be found on the website creativecommons.org/licenses/by-nc-nd/3.0/de, with the additional restriction that reproduction, distribution and use, in whole or in part, in any product or service, be it commercial or not, is not allowed without the written consent of the copyright owner. The pdf file was and remains free for everybody to read, store and print for personal use, and to distribute electronically, but only in unmodified form and only at no charge. Doesn't that "additional restriction" negate the CC-BY-NC-ND license? What does it even mean?
- humanistbot 5y ago
  Yes it does.
gus_massa 5y ago
> Lines 1, 2 and 3, together, uniquely determine special and general relativity, cosmology, the Hilbert Lagrangian and Einstein's field equations, as told here. This is a huge exaggeration. For example 1 says "W=∫L" but L is never defined. The definition of L hides a lot of details, in particular that each point of the universe is equivalent, so there is translation invariance that using the Noether's theorem implies the conservation of momentum. There are many definitions of L, for example if you are analyzing bead that locked to a circular wire, it's usual to define L with a coordinate that follows the shape of the wire. There are also definitions of L in spherical coordinates, where each coordinate is different. Anyone with a Major in Physic has nightmares about the posibilites to define L. For example in 2 "v ≤ c" can be true in a stupid universe where the force is bounded and there is enough friction everywhere. Imagine a universe that is full of "water" or "aether" or other magical thing with magical friction. And for some reason the force is bounded, for example like the post says in 3 "F ≤ c4/4G" Also, I can't imagine how it is possible to rediscover all thermodynamics from "S ≥ k" in item 5.
- nimish 5y ago
  It's also wrong: the path must be a stationary point of the action, not minimal. In GR you maximize proper time to get geodesics.
- PrettyPebble 5y ago
  For deriving special and general relativity, see https://www.motionmountain.net/maximumforce.html https://www.motionmountain.net/maximumforce.html The page also cites the papers proving the statement.
  - user-the-name 5y ago
    That page has zero words about actually deriving anything.
    - PrettyPebble 5y ago
      See Physical Review D 104 (2021) 124079. Html page is updated.
amelius 5y ago
Exercise: derive from these 9 lines that we have 3 spatial dimensions and 1 time dimension.
- PrettyPebble 5y ago
  Number of dimensions is one of the 25 numbers of line 9. But reducing the nine lines to fewer lines is an open problem, indeed.
neonate 5y ago
https://web.archive.org/web/20220319135620/https://www.motionmountain.net/9lines.html https://web.archive.org/web/20220319135620/https://www.motio...
lazyant 5y ago
Can somebody with knowledge in biology and/or physics take a look at (one of) his book and comment if it's decent as in if the science is solid? I browsed https://www.motionmountain.net/motionmountain-volume5.pdf https://www.motionmountain.net/motionmountain-volume5.pdf and I'm intrigued (there are no reviews in Amazon).
- al2o3cr 5y ago
  I skimmed the first ~150 pages of that and I'd say it's exactly as cranky as you'd think for a 400-page-long self-published book about science. Real equations are introduced without defining any terms or notation and then quickly abandoned for discussion of other things. For instance, the QED Lagrangian is brought up on page 126 without defining any of the highly-specialized notation involved (the slashed partial derivatives) and then the discussion moves on from it without _doing_ anything with it. The QED Lagrangian gets only slightly more words than "the three lightbulb scams" (p114). The term "spinor" is used several times but defined exactly zero times. The truly "wat"-inducing parts are the "Challenges" sections, for instance the first one on p29. An example: "Challenge 12: Do birds have a navel?"
- ravi-delia 5y ago
  The earlier ones aren't terrible, but yeah they get real bad real fast. There are lot's of good introductory resources from people that know what they're talking about.
- 7373737373 5y ago
  They do seem nicely formatted
5350-uiop-1130 5y ago
nice. the funny thing is that each of those 9 lines probably requires at least 9 years to fully understand :)
- PrettyPebble 5y ago
  No - just a few weeks each, during your physics studies. And several lines can be learned in parallel.
emerged 5y ago
None of us can discount the possibility that the universe was fine tuned with a specific set of seed parameters which yields a specific trajectory including all of the narrative elements of one person or everyone’s lives. Most likely the big narrative payoff is somebody winning the claw game for once at the local sports bar. But which of us will it be for?
- panda-giddiness 5y ago
  When Sabine Hossenfelder wins from the toy crane, maybe I'll take superdeterminism seriously.
spekcular 5y ago
The author is a well-known crank. See post #10 here, for instance: https://www.physicsforums.com/threads/strand-model-published.973097/ https://www.physicsforums.com/threads/strand-model-published... Proceed with caution.
- PrettyPebble 5y ago
  No, I'm not. And reading the cited exchange is indeed useful to see this. The topic here was that physics can be summed up in 9 lines. Anonymous ad hominem arguments are worthless in this context - but obviously important to certain people.
- logicallee 5y ago
  I liked the original post at https://www.motionmountain.net/9lines.html https://www.motionmountain.net/9lines.html , except for a couple of words I point out below. After reading your comment I looked at the original post with a view to identifying its basic perspective. https://www.motionmountain.net/9lines.html https://www.motionmountain.net/9lines.html was clearly not written by a physicist, as it includes the line "The nine lines contain physics, chemistry, material science, biology, medicine, geology, astronomy, engineering and computer science. It appears that the nine lines contain all natural sciences!" which is not a physics type of statement. Obviously, physics contains everything, just the way "bits contain all software". Observing that doesn't make someone a programmer, in my opinion. Why stop at physics, chemistry, material science, biology, medicine, geology, astronomy, engineering and computer science (list provided). A physicist could correctly state: "Physics contains all aspects of chemistry, Earth science / Geology, Oceanography/ marine science, Meteorology, astronomy, biology, molecular interactions, physiological mechanisms, evolution, botany / plant science(s), Zoology, Ecology, etc." However, it is kind of like saying text comprises all of the words of Shakespeare. Well, sure, but that doesn't mean that you get Shakespearean criticism from writing a text editor. It's two different fields. The author has an interesting outsider view shown in https://www.motionmountain.net/9lines.html https://www.motionmountain.net/9lines.html However, the lines "Isn't this incredible?" and "Enjoy searching for answers." are sarcastic and disrespectful to the work actual physicists put into their discipline for decades and the author should be ashamed for this tone. If they want to be a physicist they should observe and learn from physicists at every opportunity. (I'm not one, by the way.) Ignoring the rude sarcasm, we can correctly summarize the document as "Physics governs everything. Period." It's not a physics document. It is (or rather ought to be) a tribute to physicists and the unbreakable laws of physics.
kabdib 5y ago
"F equals MA and you can't push a rope" will get you though cow-college freshman physics. Not murdering your lab partner helps, too. :-)
supernova87a 5y ago
I'm a former physics/astro person, and honestly I had never seen a factor like c^4 power in my life...
- sacrosancty 5y ago
  Huh? It appears in the basic relativistic energy/momentum equation at the bottom of here http://hyperphysics.phy-astr.gsu.edu/hbase/Relativ/relmom.html#c4 http://hyperphysics.phy-astr.gsu.edu/hbase/Relativ/relmom.ht...
  - supernova87a 5y ago
    I guess I must not have been a very good one, hah. Or I wasn't a high enough energy one, needing to see factors of momentum^2!

247 points by PrettyPebble 5y ago

deleted 5y ago

[deleted]

“ bosons, quarks and leptons – with their charges and properties make up everything.” The empty space between the bosons, quarks and leptons is not made up of any of these particles, yet the space ‘exists’ - without it, everything in the universe would just be a big clump.

PrettyPebble 5y ago
In general relativity, space is not a thing.
- alasdair_ 5y ago
  I meant to thank you for this comment earlier - it’s led to a whole bunch of interesting stuff I did not know.
  - PrettyPebble 4y ago
    The 9 line summary is now also available as a preprint: https://www.motionmountain.net/9lines.pdf https://www.motionmountain.net/9lines.pdf

PrettyPebble 5y ago

Fun fact: all physics experiments ever made can be described by 9 lines, without any deviation between theory and observations. The 9 lines are sufficient to describe quantum physics and gravity. It seems that the 9 lines even contain all (update: natural) sciences, not only physics. Finding an exception to the 9 lines will make you famous. So will the discovery of a 10th line. Thousands of researchers work towards these dreams, but none succeeded yet. A few additional fun facts on https://www.motionmountain.net/9lines.html https://www.motionmountain.net/9lines.html

criticaltinker 5y ago
This is satire right? You might be getting downvotes because it’s not clear if you’re serious, and those claims seem quite ridiculous at face value.
- not_kurt_godel 5y ago
  It's essentially paraphrased from the OP. Why OP is getting upvoted, I do not know.
- PrettyPebble 5y ago
  What is ridiculous?
  - _Nat_ 5y ago
    The 9-lines thing. May've just drawn a circle and claimed that it describes all of science.
    - PrettyPebble 5y ago
      If the 9 lines are wrong, just show it... Thousands of scientists are trying the same since 50 years.
      - _Nat_ 5y ago
        It's not that they're "wrong" so much as that they're incoherent and largely non-sense. Sorry if that seems harsh, just.. this looks like someone's having some sort of crisis. It's worrisome.
        PrettyPebble 5y ago
        No, it is fun! The scientists who are looking for exceptions to the standard model and to general relativity since 50 years are having a crisis at present, as often told. The 9 lines imply all equations of physics. Every Lagrangian of physics is included. The lines are also coherent: none contradicts another. They are complementary: the cover all observations and all fields of physics. No field of physics is left out. The lines are also correct: every calculation fits with observations withing measurement accuracy, since the standard model (with neutrino masses and PMNS mixing) and general relativity exist.

humanistbot 5y ago

Physics maybe, but all sciences? This is is some serious physics determinism --- obligatory XKCD: https://xkcd.com/435/ https://xkcd.com/435/

PrettyPebble 5y ago
You are right - The text should say all "natural sciences".
- IgorPartola 5y ago
  The unnatural sciences are where the fun really begins.
  - PrettyPebble 5y ago
    True!
MauranKilom 5y ago
Funny enough, there's an even more related xkcd for this page: https://xkcd.com/2034/ https://xkcd.com/2034/
- PrettyPebble 5y ago
  Good one!
nayuki 5y ago
> The nine lines contain physics, chemistry, material science, biology, medicine, geology, astronomy, engineering and computer science. I have doubts that these 9 lines describe computer science. As I interpret it, computer science is founded on pure mathematics and is not a physical or empirical science. Computer science deals with perfect abstract mathematical objects like numbers, sets, quantification, recursion, infinities, etc.
- 5y ago

Reventlov 5y ago

I opened a volume of the books linked in the page, and found this: « Learning allows us to discover what kind of person we can be. Learning widens knowledge, improves intelligence and provides a sense of achievement. Therefore, learning from a book, especially one about nature, should be efficient and enjoyable. Avoid bad learning methods like the plague! Do not use a marker, a pen or a pencil to highlight or underline text on paper. It is a waste of time, provides false comfort and makes the text unreadable. And do not learn from a screen. In particular, never, ever, learn from the internet, from videos, from games or from a smartphone. Most of the internet, almost all videos and all games are poisons and drugs for the brain. Smartphones are dispensers of drugs that make people addicted and prevent learning. Nobody putting marks on paper or looking at a screen is learning efficiently or is enjoying doing so. » My sarcasm detector is broken, is that sarcasm ?

irrational 5y ago
Yeah, this is clearly BS. Recently I changed the turn switch on my car. How did I learn how to do that? From the Internet, specifically from watching videos. It was easily the most efficient way to learn.
dr_dshiv 5y ago
Which book?
- Reventlov 5y ago
  I was interested in electromagnetism, so https://www.motionmountain.net/motionmountain-volume3.pdf https://www.motionmountain.net/motionmountain-volume3.pdf, in the « Advice for learners » section of the introduction. I reckon this is the same text in every volume.
  - dr_dshiv 5y ago
    Yeah, not sarcasm. But contradictory for a free online downloadable. I do like the next advice, to be able to say the ideas in your own words. Maybe the point (which seems very overstated) is that highlighting and videos create the sensation of knowing, but not necessarily the knowing.

MauranKilom 5y ago

> About 18 particles > About 25 numbers Excellent science here!

rwoerz 5y ago
Sounds like my tax declaration... where they ask for the number of my children.
threatripper 5y ago
You can't contradict this. Nature is perfect.
BearOso 5y ago
Observation is part of science, but we're also limited by it. There's a lot of deeper workings that we just can't get at yet, maybe ever.
PrettyPebble 5y ago
Improved the first. The second is ok.
mhh__ 5y ago
Obviously this won't help you find the particles but this seriously isn't far off capturing how shocking symmetry groups are as a tool for building theories in particle physics. The fact that you can reduce so much physics down to some invariance is very spooky.
- PrettyPebble 5y ago
  Or just beautiful!
7373737373 5y ago
https://math.ucr.edu/home/baez/constants.html https://math.ucr.edu/home/baez/constants.html the mass of the up quark the mass of the down quark the mass of the charmed quark the mass of the strange quark the mass of the top quark the mass of the bottom quark 4 numbers for the Kobayashi-Maskawa matrix the mass of the electron the mass of the electron neutrino the mass of the muon the mass of the mu neutrino the mass of the tau the mass of the tau neutrino 4 numbers for the Pontecorvo-Maki-Nakagawa-Sakata matrix the mass of the Higgs boson the expectation value of the Higgs field the U(1) coupling constant the SU(2) coupling constant the strong coupling constant the cosmological constant

mhh__ 5y ago

The 9 equations aspect is pretty pointless but the chapters on the right hand side could be ok. One of the things that makes physics different to most subjects is that we can make an explicit goal of being smug and rederiving the laws of physics from the simplest possible principles. I think the book seems to do this, but just summarizing like done on this webpage is a bit daft.

ravi-delia 5y ago
I think the way these are phrased do a better job expressing the "vibe", for lack of a better word, of our current understanding. That the particles and constants are declared by fiat, with behavior constrained by simpler laws, is an understanding I didn't come to until I took a QFT course. The physicist's God is as concerned with forbidding seemingly pointless things as the biologist's God is with beetles.
- mhh__ 5y ago
  Vibe is not a bad word to use in these situations.
- whimsicalism 5y ago
  It is interesting that we humans have so much difficulty breaking away from anthropomorphizing.
  - roywiggins 5y ago
    If large chunks of our brainpower are actually hardwired to think in terms of other humans¹, anthropomorphism might just be a strategy to recruit those hardwired systems into helping out with other tasks. ¹ this may not be true
  - ravi-delia 5y ago
    And yet the vibe persists! Presumably it's due to low-level patterns you subconsciously pick up on, but much of the much-discussed physicist-intuition comes from knowing how the universe "likes" do do things. There's a similar thing in math, with many of the greats having just a few tricks they used over and over to great effect in any number of fields. I guess we're used to dealing with people, so the pattern is expressed as a preference (which does double duty encoding that it's not an absolute law).

arcbyte 5y ago

I think the future of physics is in Energy Wave Theory. Maybe not that theory exactly, but a similar theory going back to the idea of some kind of ether in which waves propagate.

jkuria 5y ago

Social 'scientists'? Your turn :)

humanistbot 5y ago
The natural sciences, the so-called "hard sciences" are really the easy ones, because what they study doesn't have free will. The truly difficult sciences are of human behavior.
smoyer 5y ago
You're assuming free will isn't some complex-looking behavior driven by quantum uncertainty. In the multiverse, every social scientist has many clones who's studies refute their work!
- marginalia_nu 5y ago
  Even if that is so, a quantum description of human behavior is fairly useless in terms of practical application. How does knowledge of the standard model cure the infirm, prevent crime, and so forth?
  - Itti 5y ago
    When we exhibit behaviors. Our context is derived from our visual/auditory field processing from birth. Those waves implant magnetic field signatures on our neurotransmitter morphologies. We are almost explicitly operational in quantum activity. Many if not all disabilities or health complications are resonant to your mind body homeostasis. Challenge the quantum spectral development process of a person you solve the aforementioned issues.
    - marginalia_nu 5y ago
      Right, but how is this fact in any way helpful in dealing with the phenomenal world?
      - 5y ago

la64710 5y ago

Why do the first chapters of all physics textbook ONLY talk about Greek philosophers and scientists and NEVER talk about contribution to Science from eastern civilization like India and China ? These civilizations have a very rich heritage and astounding contribution to many underlying scientific philosophies. Yet generation after generation of writers ignore them and it is sad to see that being true even today. It is time that this is changed.

deadbeeves 5y ago
Off the top of my head, I can name three things from either China or India that are science-related: the positional numbering system (and zero), the Chinese remainder theorem, and gunpowder. What am I missing that's very important yet rarely mentioned?
- fooker 5y ago
  India: quite a bit of astronomy and geometry. Also logic, philosophy and linguistics if you want to include them in the science list. China: chemistry and metallurgy. Indian science took a weird turn towards metaphysics and mystical stuff once the priests started playing a fundamental role in education.
PrettyPebble 5y ago
The Indian number system is treated in detail. Indian mathematicians are mentioned and cited.
- la64710 5y ago
  Good to know that , I did not go past the first few pages. Now some interesting contribution from India that I never heard of before https://www.manchester.ac.uk/discover/news/indians-predated-newton-discovery-by-250-years/ https://www.manchester.ac.uk/discover/news/indians-predated-... https://www.britannica.com/biography/Aryabhata-I https://www.britannica.com/biography/Aryabhata-I But I doubt that many conventional physics textbook will not even mention these and others. The writers are not to blame , but no doubt the ignorance is an unfortunate reality.

323 5y ago

I've read a few times that you can derive the Maxwell equations from knowing that U(1) exists, as this article implies, that every point in space has (among other things) the symmetry of a circle. But I've never seen this derivation. I assume it's either trivial or too complicated. Anyone has a link or thoughts on this?

unicas 5y ago
There are plenty of so called "derivations of Maxwell equations", however, I would not claim that they were based on U(1) necessarily. IMO ME are just the integrability conditions for any conserved quantity (continuity equation): take a generic three-form in R^4, then dJ=0 => J=dF. F has six components corresponding to two vectofields in R^3 which depend on the fourth coordinate and satisfy the div and curl relations as in ME ;)
- hither_shores 5y ago
  U(1) symmetry (R also works in a classical setting: it's the Lie algebra that matters) is exactly how you get a "generic three-form" to drop out of the action.
podiki 5y ago
In short, if you impose a U(1) symmetry on your Lagrangian, you get electromagnetism. Basically you do the action of U(1) and enforce that the equation of motion does not change. That gives you the electromagnetic force (a photon). Putting in some of those keywords will find plenty of detailed notes online, like http://www.physics.usu.edu/torre/Classical_Field_Theory/Lectures/04_EM.pdf http://www.physics.usu.edu/torre/Classical_Field_Theory/Lect... or more quick overviews like https://mugndonut.wordpress.com/2018/03/31/symmetries-yield-conserved-quantities/ https://mugndonut.wordpress.com/2018/03/31/symmetries-yield-...
gus_massa 5y ago
I wrote an ELI25 explanation in a comment a few months ago, and I'll copy it here: In quantum mechanics the wave function Ψ is has complex values. If you multiply everything in the universe by -1, nothing changes because all the physical results use ΨΨ* (where * is the complex conjugation). You can also multiply everything by i or -i. Moreover by any other complex number of modulo 1 because ΨΨ* does not change. (The technical term for this is U(1) global gauge symmetry.) But you can be more ambitious and want to multiply each point of the universe by a different complex number of modulo 1. ΨΨ* does not change but the derivatives of Ψ change and they are also important. (When you use the same complex number everywhere, the derivatives is just a multiple of the original derivative. When you use a different number in each point, it changes.) The only way to fix the problem with the derivative is to add a new field A. When you and multiply each point of the universe by a different complex number of modulo 1, then A changes in a simple to calculate but not obvious way. The change in A fix the problem with the derivatives of Ψ. So now the equations of the universe with Ψ and A don't change when you make this change. (The technical term for this is U(1) local gauge symmetry.) When you write carefully how a universe like this look like, the new field A is electromagnetism. (Actually, you can get the electric field and magnetic field using the derivatives of A.) Too many more details in https://en.wikipedia.org/wiki/Quantum_electrodynamics#Mathematical_formulation https://en.wikipedia.org/wiki/Quantum_electrodynamics#Mathem... > I assume it's either trivial or too complicated. It's trivial once you have 3 or 4 years studding Physics, but you will never understand how it is related to the magnets in your refrigerator. [There are like 5 simplification steps between U(1) and magnets in the refrigerator. Each one makes sense, but I can't see all of them together in my head.]

graderjs 5y ago

s/nature/the simulation/g 1. Total compute capacity is limited and redistributes toward areas of high activity. 2. Processor speed is limited. 3. Mutations are sensibly constrained to prevent overflow. 4. Smallest addressable memory space. 5. No process is ever fully idle. 6. IPC is done using circles. 7. The kernel however operates at the level of spheres, and pointers to pointers to pointers to spheres. 8. There's roughly 18 niceness levels, but rumors are there are a couple more. 9. About 25 programmers worked on the project and at the end each one got to pick a nothing-up-my-sleeve number. Some say there are Easter eggs hidden there yet to be discovered.

KineticLensman 5y ago
Religion: "God did it" Simulation hypothesis: "God did it, with a computer"
- qiskit 5y ago
  Simulation hypothesis: God did the first simulation with a computer, everything else is a simulation of a simulation.
  - kleene_op 5y ago
    Simulation hypothesis: It's simulations all the way down. No gods in sight.
DangitBobby 5y ago
It makes intuitive sense to me that computers are physically constrained in all of the ways (and more) that the universe itself is physically constrained. I don't know why the inclination is to take these fundamental constraints and then say "the universe is in a computer" instead of saying "the computer is in a universe".

gpvos 5y ago

> This pdf file is licensed under the Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 Germany Licence, whose full text can be found on the website creativecommons.org/licenses/by-nc-nd/3.0/de, with the additional restriction that reproduction, distribution and use, in whole or in part, in any product or service, be it commercial or not, is not allowed without the written consent of the copyright owner. The pdf file was and remains free for everybody to read, store and print for personal use, and to distribute electronically, but only in unmodified form and only at no charge. Doesn't that "additional restriction" negate the CC-BY-NC-ND license? What does it even mean?

humanistbot 5y ago
Yes it does.

gus_massa 5y ago

> Lines 1, 2 and 3, together, uniquely determine special and general relativity, cosmology, the Hilbert Lagrangian and Einstein's field equations, as told here. This is a huge exaggeration. For example 1 says "W=∫L" but L is never defined. The definition of L hides a lot of details, in particular that each point of the universe is equivalent, so there is translation invariance that using the Noether's theorem implies the conservation of momentum. There are many definitions of L, for example if you are analyzing bead that locked to a circular wire, it's usual to define L with a coordinate that follows the shape of the wire. There are also definitions of L in spherical coordinates, where each coordinate is different. Anyone with a Major in Physic has nightmares about the posibilites to define L. For example in 2 "v ≤ c" can be true in a stupid universe where the force is bounded and there is enough friction everywhere. Imagine a universe that is full of "water" or "aether" or other magical thing with magical friction. And for some reason the force is bounded, for example like the post says in 3 "F ≤ c4/4G" Also, I can't imagine how it is possible to rediscover all thermodynamics from "S ≥ k" in item 5.

nimish 5y ago
It's also wrong: the path must be a stationary point of the action, not minimal. In GR you maximize proper time to get geodesics.
PrettyPebble 5y ago
For deriving special and general relativity, see https://www.motionmountain.net/maximumforce.html https://www.motionmountain.net/maximumforce.html The page also cites the papers proving the statement.
- user-the-name 5y ago
  That page has zero words about actually deriving anything.
  - PrettyPebble 5y ago
    See Physical Review D 104 (2021) 124079. Html page is updated.

amelius 5y ago

Exercise: derive from these 9 lines that we have 3 spatial dimensions and 1 time dimension.

PrettyPebble 5y ago
Number of dimensions is one of the 25 numbers of line 9. But reducing the nine lines to fewer lines is an open problem, indeed.

neonate 5y ago

https://web.archive.org/web/20220319135620/https://www.motionmountain.net/9lines.html https://web.archive.org/web/20220319135620/https://www.motio...

lazyant 5y ago

Can somebody with knowledge in biology and/or physics take a look at (one of) his book and comment if it's decent as in if the science is solid? I browsed https://www.motionmountain.net/motionmountain-volume5.pdf https://www.motionmountain.net/motionmountain-volume5.pdf and I'm intrigued (there are no reviews in Amazon).

al2o3cr 5y ago
I skimmed the first ~150 pages of that and I'd say it's exactly as cranky as you'd think for a 400-page-long self-published book about science. Real equations are introduced without defining any terms or notation and then quickly abandoned for discussion of other things. For instance, the QED Lagrangian is brought up on page 126 without defining any of the highly-specialized notation involved (the slashed partial derivatives) and then the discussion moves on from it without _doing_ anything with it. The QED Lagrangian gets only slightly more words than "the three lightbulb scams" (p114). The term "spinor" is used several times but defined exactly zero times. The truly "wat"-inducing parts are the "Challenges" sections, for instance the first one on p29. An example: "Challenge 12: Do birds have a navel?"
ravi-delia 5y ago
The earlier ones aren't terrible, but yeah they get real bad real fast. There are lot's of good introductory resources from people that know what they're talking about.
7373737373 5y ago
They do seem nicely formatted

5350-uiop-1130 5y ago

nice. the funny thing is that each of those 9 lines probably requires at least 9 years to fully understand :)

PrettyPebble 5y ago
No - just a few weeks each, during your physics studies. And several lines can be learned in parallel.

emerged 5y ago

None of us can discount the possibility that the universe was fine tuned with a specific set of seed parameters which yields a specific trajectory including all of the narrative elements of one person or everyone’s lives. Most likely the big narrative payoff is somebody winning the claw game for once at the local sports bar. But which of us will it be for?

panda-giddiness 5y ago
When Sabine Hossenfelder wins from the toy crane, maybe I'll take superdeterminism seriously.

spekcular 5y ago

The author is a well-known crank. See post #10 here, for instance: https://www.physicsforums.com/threads/strand-model-published.973097/ https://www.physicsforums.com/threads/strand-model-published... Proceed with caution.

PrettyPebble 5y ago
No, I'm not. And reading the cited exchange is indeed useful to see this. The topic here was that physics can be summed up in 9 lines. Anonymous ad hominem arguments are worthless in this context - but obviously important to certain people.
logicallee 5y ago
I liked the original post at https://www.motionmountain.net/9lines.html https://www.motionmountain.net/9lines.html , except for a couple of words I point out below. After reading your comment I looked at the original post with a view to identifying its basic perspective. https://www.motionmountain.net/9lines.html https://www.motionmountain.net/9lines.html was clearly not written by a physicist, as it includes the line "The nine lines contain physics, chemistry, material science, biology, medicine, geology, astronomy, engineering and computer science. It appears that the nine lines contain all natural sciences!" which is not a physics type of statement. Obviously, physics contains everything, just the way "bits contain all software". Observing that doesn't make someone a programmer, in my opinion. Why stop at physics, chemistry, material science, biology, medicine, geology, astronomy, engineering and computer science (list provided). A physicist could correctly state: "Physics contains all aspects of chemistry, Earth science / Geology, Oceanography/ marine science, Meteorology, astronomy, biology, molecular interactions, physiological mechanisms, evolution, botany / plant science(s), Zoology, Ecology, etc." However, it is kind of like saying text comprises all of the words of Shakespeare. Well, sure, but that doesn't mean that you get Shakespearean criticism from writing a text editor. It's two different fields. The author has an interesting outsider view shown in https://www.motionmountain.net/9lines.html https://www.motionmountain.net/9lines.html However, the lines "Isn't this incredible?" and "Enjoy searching for answers." are sarcastic and disrespectful to the work actual physicists put into their discipline for decades and the author should be ashamed for this tone. If they want to be a physicist they should observe and learn from physicists at every opportunity. (I'm not one, by the way.) Ignoring the rude sarcasm, we can correctly summarize the document as "Physics governs everything. Period." It's not a physics document. It is (or rather ought to be) a tribute to physicists and the unbreakable laws of physics.

kabdib 5y ago

"F equals MA and you can't push a rope" will get you though cow-college freshman physics. Not murdering your lab partner helps, too. :-)

supernova87a 5y ago

I'm a former physics/astro person, and honestly I had never seen a factor like c^4 power in my life...

sacrosancty 5y ago
Huh? It appears in the basic relativistic energy/momentum equation at the bottom of here http://hyperphysics.phy-astr.gsu.edu/hbase/Relativ/relmom.html#c4 http://hyperphysics.phy-astr.gsu.edu/hbase/Relativ/relmom.ht...
- supernova87a 5y ago
  I guess I must not have been a very good one, hah. Or I wasn't a high enough energy one, needing to see factors of momentum^2!