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To anyone interested in learning physics, I suggest reading https://www.susanrigetti.com/physics

Do not try to learn anything from the submitted article, it promotes a, shall we say, "non-traditional" view of physics that is unlikely to be helpful.




I wouldn't call all of it "non-traditional" (though some of it is). Either way, the author is being very sloppy with his "proofs", so it's hard to learn anything from the article unless you already know the details.


(5) (the minimum value of entropy) seems to come from an extremely hand-wavy argument on page 5 here:

https://arxiv.org/abs/2307.09914

It appears to be an example of argument by italics. I’m not convinced that it has any real content — it seems to be trying to say that the author thinks all systems are either being observed or they aren’t, and that there are therefore at least two microstates.

I think this is entirely missing the point and is mostly wrong. Even in the highly classical case of a gas, you have a box full of gas, with n particles and some volume V, etc. Those parameters form the macro state. Now you count microstates, take the log, and get the entropy. But nowhere in the count is a set of states where the gas is observed and a set where it isn’t. If you have a box of gas with n particle, etc, it’s implied that the gas exists!

So I don’t buy it. I’ll stick with S >= 0.


You're right, I was only looking at line (5) briefly and thought he was talking about the minimum change of entropy.

S ≥ k ln2 is incorrect, as you say. A system whose state is fully known has no entropy. One can either see this through counting the number of microstates (which is 1) or by applying Shannon's definition of entropy to the trivial probability distribution which is 1 for precisely one state.


> (the minimum value of entropy) seems to come from an extremely hand-wavy argument

So does the "maximum force" argument, which is given in this paper:

https://arxiv.org/abs/physics/0309118

It is, to say the least, not generally accepted as a valid argument.


Wow, there’s not a whole lot argument at all in there.

Maximum power seems especially odd — power is extensive. If you have two maximum power systems, don’t you end up with double the power?


> power is extensive

So is force. Two maximum force systems should also end up with double the force.


True, but “force” as used in that paper is so vague I gave up. Force is applied somewhere, and it makes very little sense to add up forces in different places. Although if you ignore GR and add up forces everywhere, you get F=0 (Newton’s third law), which is well below the supposed maximum. And trying to decide whether the net internal force of a system (0) is an extensive property is a bit silly :)

Admittedly, power has much the the same problem. Saying that P <= P_max is some sort of physical law requires a lot more explanation of what it would mean than the paper even tries to give it.


Your link points to texts for 9 years of full-time learning.


You can skip the areas you've already learned, but other than that, that's physics. It's not something you can learn in a weekend.


Humans, arguably some of the smartest and most capable who've ever lived, have worked tirelessly over 400 years to produce the corpus. I don't think you can really learn it all in 9 years - I think a normal bright person will take 20 and even then only have real intuition about parts of it. Most of the modern young wunderkinds of physics are ridiculously good symbol manipulators, and pay little to no attention to intuition.


Well do you want to learn it or not? There's no royal road.


just start with the Feynman undergraduate lectures (listed). The easy-mode of that is "Six Easy Pieces" (read it on kindle) which are the easiest 6 lectures.

At some point you'll need math, I recommend https://www.amazon.com/No-bullshit-guide-linear-algebra/dp/0... (I actually started here), and for calculus, "No BS Guide to Math/Physics" by the same author. These books both include a review of high school math (i.e. trig) which i needed. For DiffEq I currently recommend Logan's "A First Course in Differential Equations", this is where I am now and I found this the most gentle after trying several textbooks recommended from r/math. Context: I am an adult with an engineering degree from 20 yrs ago.


Reminds me of a machine learning article that recommended starting studies with the following https://webspace.science.uu.nl/~gadda001/goodtheorist/


Given how heavily mathematical physics is this isn't surprising. Some mathematical concepts themselves can take a couple of months to learn to a sufficient level, especially if you include the prerequisites.


Might actually teach physics then


There is a full textbook behind the article, for what is worth (haven’t read it myself, so no opinion on it): https://www.motionmountain.net


Just skimmed the EM section: I didn't catch anything egregiously wrong, per se (but again, I only skimmed it), but it's mostly fluff, and the actual physics content that does it exist is targeted at wildly different levels. For instance the author goes from "an electric field is like a tiny arrow attached to every point in space" (day 1 of intro physics for non-physics majors) in chapter 1 to assuming the reader knows what covariant derivatives are (advanced undergraduate) in chapter 2. I would strongly recommend against using these books.


I think a really important point that Susan doesn't go over is her course needs to be paired with something like Anki or you'll forget so much by the time you're all the way through.




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