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So you want to learn physics (second edition, 2021)

susanrigetti.com

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Re: So you want to learn physics (second edition, 2021)

#51

Post by [deleted] »

gmueckl wrote: post #29
somenameforme wrote: post #19

Earlier quoted context omitted.

I'd disagree and have done exactly that. I started with a reasonable basis in physics, but self studying through an entire course dramatically expanded my understanding. For an example of what I mean this [1] is Feynman's lecture on conservation of energy. It's something every schoolkid learns -- I'm fairly sure I saw my first pendulum from the nose demo in middle school, yet Feynman will take this and make you compl…

Conservation of energy is simply the invariance of a system to translation in time: the system shows the same time evolution from a well defined starting state regardless of whether that state exists at a time t or a time t+t' with an arbitrary t'. This is one application of Noether's theorem. This is an example of a topic that unstructured self study would likely skip. But it is included in every properly structured…

[deleted]

Re: So you want to learn physics (second edition, 2021)

#52

Post by Xmd5a »

not-a-llm wrote: post #37
gmueckl wrote: post #29

Earlier quoted context omitted.

Conservation of energy is simply the invariance of a system to translation in time: the system shows the same time evolution from a well defined starting state regardless of whether that state exists at a time t or a time t+t' with an arbitrary t'. This is one application of Noether's theorem. This is an example of a topic that unstructured self study would likely skip. But it is included in every properly structured…

Noeter theorem and energy get complicated in General Relativity, because there is no global time translation symmetry https://curtjaimungal.substack.com/p/what-is-energy-actually Ignoring that, saying "energy must exist because of Noether and time-translation" doesn't really tell what energy actually is, not a very satisfactory response

> Why is this conserved? Because ∇ᵤ(Tᵘᵥξᵥ) = (∇ᵤ Tᵘᵥ)ξᵥ + Tᵘᵥ(∇ᵤ ξᵥ).

Interesting.

> This is an example of a topic that unstructured self study would likely skip.

I'm not studying physics – could you take a look at some unstructured reflexions I wrote a couple weeks ago?

https://news.ycombinator.com/item?id=48699125

Re: So you want to learn physics (second edition, 2021)

#53

Post by BrandoElFollito »

gmueckl wrote: post #29
somenameforme wrote: post #19

Earlier quoted context omitted.

I'd disagree and have done exactly that. I started with a reasonable basis in physics, but self studying through an entire course dramatically expanded my understanding. For an example of what I mean this [1] is Feynman's lecture on conservation of energy. It's something every schoolkid learns -- I'm fairly sure I saw my first pendulum from the nose demo in middle school, yet Feynman will take this and make you compl…

Conservation of energy is simply the invariance of a system to translation in time: the system shows the same time evolution from a well defined starting state regardless of whether that state exists at a time t or a time t+t' with an arbitrary t'. This is one application of Noether's theorem. This is an example of a topic that unstructured self study would likely skip. But it is included in every properly structured…

Noether theorem is one of the nicest ones to derive (together with Maxwell equations). There is such an elegance to go from the axions to the result.

I still have a trauma associated with this, though, because it popped out in one exam and I could see the pages in my notes where it was derived but they were quite blank.

Re: So you want to learn physics (second edition, 2021)

#54

Post by felooboolooomba »

potbelly83 wrote: post #7

I have no idea why these sorts of posts are popular. Past college you're not going to learn physics by trying to self-study an entire university course. The best way to learn is just to pick a small part of physics you'd like to learn (preferably related to your job), i.e. how GPS work or some fluid mechanics etc... Then learn the physics you need for that. Knowledge accumulation can't be organized in a straight line…

We don't see things as they are, we see them as we are.

https://en.wikipedia.org/wiki/False_consensus_effect

Re: So you want to learn physics (second edition, 2021)

#55

Post by pmontra »

Ono-Sendai wrote: post #33
somenameforme wrote: post #19

Earlier quoted context omitted.

I'd disagree and have done exactly that. I started with a reasonable basis in physics, but self studying through an entire course dramatically expanded my understanding. For an example of what I mean this [1] is Feynman's lecture on conservation of energy. It's something every schoolkid learns -- I'm fairly sure I saw my first pendulum from the nose demo in middle school, yet Feynman will take this and make you compl…

energy = frequency of angular rotation in the complex plane of a wavefunction.

This is new to me (thanks, I'll investigate) and it's the kind of things the books of Physics at University (Computer Science) was full of, completely detached from real world experience. Then there was the book of exercises to prepare for the exams. Sometimes finding the right way to go from theory to calculations was a puzzle in its own. I guess that they were almost the very same books they used at the Physics department and teachers are really interested only in students that can master the subject by themselves with no help. I had one of those students at high school. He was reading university books by 16 and he is a professor now.

Luckily the books of Physics at high school started from practical experience and then showed the equations. So, my advice to somebody willing to learn physics, with plenty of time, no ambition to become a researcher is: go through high school books to get the gist of the subject, then go deeper with one of those university books.

Re: So you want to learn physics (second edition, 2021)

#59

Post by npalli »

How does one know whether they actually learnt physics this way. Seems a lot of reading and structure, that's great. Not convinced about whether there is a change in understanding. Typical university/college classes have assignments, quizzes, exams etc.. don't see the equivalent.

Re: So you want to learn physics (second edition, 2021)

#60

Post by ndriscoll »

npalli wrote: post #59

How does one know whether they actually learnt physics this way. Seems a lot of reading and structure, that's great. Not convinced about whether there is a change in understanding. Typical university/college classes have assignments, quizzes, exams etc.. don't see the equivalent.

The post explicitly calls out that solution manuals are available and that one should do most/all problems. For highly mathematical topics you can also do derivations (or proofs in math) yourself before reading the one in the book.
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