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On chapter 18 of "The Feynman Lectures on Physics Volume II: Mainly Electromagnetism and Matter", Richard Feynman presents a table which he says has "all that was known of fundamental classical physics, that is, the physics that was known by 1905." And he adds "Here it is all, in one table. With these equations we can understand the complete realm of physics." Even though this sounds too reductionist to me, I think it is quite interesting and I was wondering whether it is possible to imagine and create a second table, containing the most fundamental equations of all current Physics. I understand that a mere list of formulas is useless if one doesn't get the underling concepts. But, even for aesthetic reasons, what I am trying to do is just to ask: What would a more or less brief list of the supposedly most fundamental equations of Classical and Modern Physics look like?

Classical Physics according to Feynman.

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closed as too broad by DarenW, Bernhard, ACuriousMind, Brandon Enright, Kyle Kanos Aug 12 '14 at 20:39

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • $\begingroup$ Related: physics.stackexchange.com/q/62117/2451 and physics.stackexchange.com/q/53324/2451 $\endgroup$ – Qmechanic Aug 12 '14 at 12:51
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    $\begingroup$ First, let me say that I agree with you that Feynman's statement is a little too reductionist. Second, open-ended and (to some extent) opinion-based questions like this tend to get closed quickly on this site, although I can sympathize with this one. Third, there is a big problem with this question, which Feynman smartly avoided by introducing a (chronological) cut-off: We are aware that our current physical theories are not the whole story and it is therefore impossible to present 'the fundamental equations of modern physics'... $\endgroup$ – Danu Aug 12 '14 at 12:51
  • $\begingroup$ What one can try to do is to summarize, as succinctly as possible, QFT and GR (including the Standard Model(s) of particle physics & cosmology), two broad theoretical frameworks which seem to cover nearly everything we know about quite accurately, although - once again - I think it is quite ridiculous that a reasonably small number of equations could represent all of physics. $\endgroup$ – Danu Aug 12 '14 at 12:53
  • $\begingroup$ ...That all being said, I think it could be very interesting to write down the Lagrangians that lie at the basis of all our current theories. in one spot $\endgroup$ – Danu Aug 12 '14 at 12:55
  • $\begingroup$ It would be interesting to see all the Lagrangians that lie at the basis of all our current theories. How do they look like? $\endgroup$ – roy Aug 12 '14 at 13:49
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Well.. since you want a lagrangian....

I found the lagrangian of the standard model of physics. Since the standard model is the theory with combines all fundamental forces but gravity, then it describes a big part of physics.

If you want general relativity as well, you can include Einstein Field Equations.

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  • $\begingroup$ Adding two Lagrangians from two independent theories does not form the Lagrangian for a better theory, though. $\endgroup$ – CuriousOne Aug 13 '14 at 18:57
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The CERN standard model Lagrangian T-shirt!

The CERN standard model (SM) Lagrangian T-shirt (by John Ellis, I think) -- it is not precise but captures all the essential details. This should make @roy happy. Recall that the SM doesn't include GR.

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  • $\begingroup$ This may perhaps be (partially) a joke answer, but I do think omitting GR is a serious offense... Please edit! $\endgroup$ – Danu Aug 12 '14 at 15:58
  • $\begingroup$ Wait... where is the rest of the standard model Lagrangian? The last time I looked at it, if filled almost a whole page! Me thinks somebody was lazy or didn't have a screen printing process with enough resolution. $\endgroup$ – CuriousOne Aug 12 '14 at 19:29
  • $\begingroup$ @CuriousOne This is not the full SM Lagrangian but shows the important couplings. Line 1: Gauge Boson KE; Line 2: Fermion KE; Line 3: Yukawa couplings and Line 4: The Higgs boson KE and potential. Finally, SM doesn't include GR. $\endgroup$ – suresh Aug 12 '14 at 23:59
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    $\begingroup$ "I have discovered a truly marvelous equation of motion for the universe but this T-shirt is too small to contain..." $\endgroup$ – CuriousOne Aug 13 '14 at 18:54

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