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Ask HN: How to self-study physics?

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Re: Ask HN: How to self-study physics?

#91

Post by davidivadavid »

ukj wrote: post #88
petermcneeley wrote: post #84

Earlier quoted context omitted.

"I'd suggest not actually trying to simulate physical systems on a computer" I cannot disagree enough with this statement. I am double major in Physics and CS. There are two kinds of physics, Math and Physics. Most of what you learn in uni physics is Math. But the Math is only one (outdated) description of the nature of physical law. Leonard Susskind himself has said on multiple occasions that the equations of physic…

I am to really glad to hear commentary like this coming from physicists. (read: glad to see others siding with my biases). Ceteris paribus there is one significant distinction between Mathematics and Computer Science: state. The Mathematical Universe is immutable/stateless/timeless. The Computational Universe is mutable/stateful/time-bound. The observer effect in physics can be trivially expressed and evaluated as a…

It seems likely that anything that can be expressed in "any programming language" is isomorphic to something that exists in math and can be expressed in that language (automata theory, type theory, category theory, pick your poison).

Re: Ask HN: How to self-study physics?

#92

Post by rguzman »

scottlocklin wrote: post #74

For the love of God, don't use Feynman lectures to learn physics. That's something you read after you know physics, for relaxation and conceptual stuff. Resnick & Halliday is a much better freshman/sophomore book. Susskind's "theoretical minimum" is actually pretty good. http://theoreticalminimum.com/courses Fowler gives a pretty conventional undergraduate physics curriculum (adding Feynman in there somehow). If it w…

context: former theoretical physics grad student, dropped out ABD to start a company.

this comment is right on the money on several fronts:

- the Feynman lectures are great after you already understand some of the mechanics of "doing" physics and have some other exposure to the topics, Halliday & Resnick is a better place to start on any one topic

- with infinite time, i'd always follow the approach of learning the math first and then the physics, the book by Boas is pretty good for self study of the minimum necessary math

- there's no real reason to follow a traditional grad school curriculum ala Fowler unless you need to pass quals in a traditional grad school setting

- simulating physical systems on computers is a pretty good exercise, but very time-consuming, avoid if you already spend a lot of time in front of computers

and some thoughts of my own:

- "get a strong foundation in Physics" is a bit too vague to be a useful goal, some examples of potentially better goals: "be able to pass a classical mechanics qual in the allotted time", "be able to write down the standard model and explain it", "be able to grok N papers from the X section of arxiv per week", "be able to write down toy classical field theories and calculate their predictions", ...

- if you are looking to avoid computers, try supplementing your reading with simple experiments either by buying educational kits or by hacking together things

- the books by David Griffiths (esp the E&M one) are awesome

- try to follow curiosity instead of a program: trying to answer "how do superconducting materials work?" for yourself is better than "follow the grad intro to condensed matter that's available online"

- use the physics stackexchange and other forums: asking and answering questions can be very helpful

Re: Ask HN: How to self-study physics?

#93

Post by petermcneeley »

supdatecron wrote: post #90
petermcneeley wrote: post #84

Earlier quoted context omitted.

"I'd suggest not actually trying to simulate physical systems on a computer" I cannot disagree enough with this statement. I am double major in Physics and CS. There are two kinds of physics, Math and Physics. Most of what you learn in uni physics is Math. But the Math is only one (outdated) description of the nature of physical law. Leonard Susskind himself has said on multiple occasions that the equations of physic…

> Most of what you learn in uni physics is Math. But the Math is only one (outdated) description of the nature of physical law. Is this the lack of additional parameters for the equations? All of my physics problems (only took a couple courses) were like "what if this spherical horse rolled down a hill at 34 degree decline" but failed to include friction, atmosphere. Just gravity. It always felt fake to me. Perhaps t…

By outdated what I more mean is that I think if the greats of the ~1800 had modern computers they would probably not use mathematics in its current form to study physics. There already has been on transition of this kind. Newton used Geometry to study physics whereas today we use Math which more has its roots in symbolic logic.

Re: Ask HN: How to self-study physics?

#94

Post by QuesnayJr »

orbifold wrote: post #60

There are a few themes that physics revolves around: 1. Action Principle: A lot of problems in mechanics can be boiled down to writing down the correct Lagrangian. 2. Statistical physics, this teaches you about to think in terms of "Zustandssummen" and is the starting point for deriving lots of interesting laws like black body radiation. 3. Field (Gauge) Theory, turns out you can write down and derive interesting Lag…

I think this is a good list. I think if you are interested in physics just for intellectual breadth, and not to become a physicist, it makes sense to focus on "big picture" ideas. Analytical mechanics and Noether's theorem are appealing big picture ideas.

Re: Ask HN: How to self-study physics?

#95

Post by topaz0 »

I'm a current PhD student in physics. Here's a bit of an oddball idea, that might be complementary. Read, sit with, and understand this paper: https://journals.aps.org/pr/abstract/10.1103/PhysRev.106.620

I say this because -- It motivates and sketches statistical mechanics, which I expect is the most interesting topic to you given your specialty. -- It elegantly makes a point that I think is very important about physics: that physics is _almost entirely_ mathematical. The remainder is just about constraining the math to reflect the possibilities that seem to be actually realizable in nature.

Of course there's a lot more to physics than is described here, and you'll want to study the particular phenomena that emerge -- that's the whole point. But I think that given your background, setting this perspective will allow you to ask the right questions when you approach a new topic, and allow you to go out of the normal order.

One more note about the nature of doing/understanding physics: a huge part of it is taking the right limit. Reasonably complicated systems described in the language of some theory are generally intractable to analyze exactly, or to draw general conclusions from, so you need to throw something away to make progress. Figuring out the right limit is the same as figuring out what details you can throw away while preserving the core phenomenon you're interested in.

Re: Ask HN: How to self-study physics?

#96

Post by brummm »

I think the guide is ok, but I actually believe some of the things that are in the graduate section should be in the undergraduate section.

One thing that is important: Everything starts with classical mechanics. Newtownian phsyics is the base for everything and you will never advance without knowing this really well. That said, in my undergrad mechanics class in my first term as a physics student, we started out with classical Newtonian mechanics and then quickly moved on to the Lagrangian and Hamiltonian formulations of classical mechanics. I don't see why that should be something reserved for graduate classes.

Further, since you're not a math or physics student, I assume you will quickly reach the limits of your math education. Things that are required for properly understanding the theoretical foundations even just mechanics are:

- n-dimensional calculus (think Tensors, Gradients, divergences, Laplacians, etc.)

- complex numbers and functions

- basic knowledge of differential equations and ways to solve them

- things like Fourier transforms and things like Vector spaces, groups and symmetries

- basic statistics knowledge of course

- linear algebra

Second, like some people have already mentioned: Just reading a book will not teach you physics. Actually solving the problem in whatever resources you're using will, though. They take much, much longer than just reading a book, however.

Re: Ask HN: How to self-study physics?

#97

Post by andrepd »

petermcneeley wrote: post #84
scottlocklin wrote: post #74

For the love of God, don't use Feynman lectures to learn physics. That's something you read after you know physics, for relaxation and conceptual stuff. Resnick & Halliday is a much better freshman/sophomore book. Susskind's "theoretical minimum" is actually pretty good. http://theoreticalminimum.com/courses Fowler gives a pretty conventional undergraduate physics curriculum (adding Feynman in there somehow). If it w…

"I'd suggest not actually trying to simulate physical systems on a computer" I cannot disagree enough with this statement. I am double major in Physics and CS. There are two kinds of physics, Math and Physics. Most of what you learn in uni physics is Math. But the Math is only one (outdated) description of the nature of physical law. Leonard Susskind himself has said on multiple occasions that the equations of physic…

And I cannot disagree enough with your comment.

>There are two kinds of physics, Math and Physics. Most of what you learn in uni physics is Math. But the Math is only one (outdated) description of the nature of physical law.

Lord knows what you mean by this. By "math physics" do you mean theoretical, and by "physics physics" the experimental part? Even then, this doesn't make any sense. Every physics course teaches theory and experiment. Particularly, what do you mean by "Math is only one outdated description of the nature of physical law"? I'm very curious, maybe I'm missing something.

>Leonard Susskind himself has said on multiple occasions that the equations of physics are at most highschool math however the solutions are sometimes phd+ level.

So? Again, I don't see what you're trying to imply with this. Seems a perfectly correct observation.

>To me Physics is the study of the relationship between state. Mostly this state is finite and the laws governing its evolution are simple and local. A computer is the best tool to discover the solutions to this evolving state.

This to my opinion is, for a lack of a better word, "hipsterism". Physics is the science that studies the universe at the most fundamental level/low level. That's it. "State"? "This state is finite"? What do you mean by "this state is finite"? I struggle to see what this is trying to describe (there are infinite degrees of freedom in many theories throughout physics).

Re: Ask HN: How to self-study physics?

#99

Post by PascLeRasc »

Fiveh2751 wrote: post #79

I dunno but I think I once came across a reddit post about a user who asked how they can understand the bits and bites of electronics and they were reffered to a book which I don't really know its title and its what I currently looking for. I need some help to remember this book.

It was probably "The Art of Electronics". It's a fantastic book and absolutely worth buying.

Re: Ask HN: How to self-study physics?

#100

Post by andrepd »

ukj wrote: post #88
petermcneeley wrote: post #84

Earlier quoted context omitted.

"I'd suggest not actually trying to simulate physical systems on a computer" I cannot disagree enough with this statement. I am double major in Physics and CS. There are two kinds of physics, Math and Physics. Most of what you learn in uni physics is Math. But the Math is only one (outdated) description of the nature of physical law. Leonard Susskind himself has said on multiple occasions that the equations of physic…

I am to really glad to hear commentary like this coming from physicists. (read: glad to see others siding with my biases). Ceteris paribus there is one significant distinction between Mathematics and Computer Science: state. The Mathematical Universe is immutable/stateless/timeless. The Computational Universe is mutable/stateful/time-bound. The observer effect in physics can be trivially expressed and evaluated as a…

>The observer effect in physics can be trivially expressed and evaluated as a mutating getter in any programming language.

>It cannot be expressed in any Mathematical grammar.

What on earth are you trying to say...? There is a whole mathematical treatment of quantum mechanics, measurement effect included (several treatments). More to the point, any algorithm can be formalised in e.g. a Turing machine, or any other equivalent universal model of computation. So there's literally nothing in "computer science" that you cannot express in mathematics.

This reeks of Dunning-Kruger: you don't even know enough about what you're talking about to realise how badly little sense you're making. I strongly suggest you familiarise yourself with a topic before opining about it. I'll be hard-pressed to believe you ever opened a physics textbook in your life after high school. Why then do you feel the need to talk blindly about it? I never opened a book about aeronautics in my life, therefore I would never presume to lecture anybody about plane-building... That would just be arrogance.

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