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It's awesome! It helps a technical-minded layman like me understand (probably like 1%) more about astrophysics. By far the most informative while still being entertaining thing about physics I've ever seen. Pick any video and watch it, they're great.

What's your level of maths/physics? It could help everyone give you some pointers or references.

For example, if I'd claim that a ball of homogenous, initially unmoving, dust roughly the size of Earth needs only a few minutes to gravitationally collapse into a single body, would you:

- Be completely astounded and unable to prove or disprove this statement.

- Obtain a rough approximation after looking up some integrals or some old classical mechanics book you have lying around.

- Call my bluff and make it into a game of physics chicken.

- Make an N-body simulation and go for a coffee while it computes.

- Consider cases where matter pressure is and isn't equal to 0. Find the p = 0 as trivial.

- Something completely different. It's not like I wasn't just guessing and being slightly facetious. ;)

Probably something like 2, but I would have to think about it. I have about an undergrad level of understanding of astronomy, physics, and probably chemistry. I can do multivariable calculus...or at least I could 10 years ago. My math might be a little better than that when it comes to electromagnetic stuff because of my EE job, but maybe not. I feel confident in my ability to learn new maths. Like if you needed to use a tensor in an equation I could figure out what it is. But I have forgotten a lot more math than I know right now, and would need to relearn a lot. Right now I know 0 quantum mechanics.

OK, so here are my recommendations for quantum mechanics:

To start yourself on a gentle but not devoid of substance course in quantum mechanics, I can point you to this course on edx: Quantum Mechanics for Everyone (audited it, there are moments to gripe about, but it's not a bad place to start). If you prefer books, I remember Quantum Mechanics: The Theoretical Minimum (associated lecture series can be found here. Returning to Classical Mechanics will help you get used to Lagrange and Hamilton formalisms, important as QM and QFT don't exist without those two) by L. Susskind and A. Friedman rather fondly.

Going through those should be more than enough to make books like *Principles of Quantum Mechanics* by Shankar easy. That's the textbook my undergrad QM course used in conjunction with Sakurai and Landau-Lifshitz texts. The latter two are more in-depth and advanced, but they complement the course really well.

For special relativity refresher, I can recommend this course by Brian Greene. It's interactive, problem-based and feels complementary to most textbooks.

Immortal all-purpose recommendations would be Berkeley course in physics and Feynman's Lectures.

At first, I thought about editing my previous post, but since it's longer than that one…

After revisiting the texts from the Theoretical Minimum, I found this bit from a Classical Mechanics preface as a rather apt summary of the series:

- What became clear after a couple of quarters is that the students were not completely satisfied with the layperson’s courses I was teaching. They wanted more than the

*Scientific American*experience. A lot of them had a bit of background, a bit of physics, a rusty but not dead knowledge of calculus, and some experience at solving technical problems. They were ready to try their hand at learning the real thing—with equations. The result was a sequence of courses intended to bring these students to the forefront of modern physics and cosmology.

IMHO the authors accomplished their job. In the series so far you have gateways to branches of physics you could expand on through other books:

*Classical Mechanics* by J.R. Taylor

*Introduction to Quantum Mechanics* by D. J. Griffiths (of *Introduction to Electrodynamics* fame)

*Principles of Quantum Mechanics* by R. Shankar

*Diagrammatica: The Path to Feynman Diagrams* by M. Veltman (quantum field theory in a nutshell, which also happens to be a title of a different textbook that's intended for newcomers :P)

*Gravitation and Cosmology: principles and applications of the general theory of relativity* by S. Weinberg (disputable choice, but I liked the fact that a lot of the calculations were explicit. Starts with a differential geometry refresher, which may or may not be enough)

Most of those are either from my undergrad courses or ones that I picked up at random at the library and liked a lot.