**Difficulty level:**★

### Video channels

There are a lot of great science channels, but I prefer more technical content:

- MinutePhysics: Henry Reich has a physics Master’s degree from Perimeter Institute
- PBS Space Time: Matt O’Dowd is an astrophysicist, and delves into some advanced topics
- Numberphile and Sixty Symbols: interviews of mathematicians and physicists on broad topics
- 3Blue1Brown: Grant Sanderson studied math(s) at Stanford

### People

- John Norton, philosophy and history of relativity. Others recommend the introductory “Einstein for everyone“, though I haven’t personally looked at this in detail yet

### Research

- arXiv (“archive”), free access pre-prints, particularly those in gr-qc (general relativity and quantum cosmology). People upload draft research papers here to share with the community while hoping a journal will accept them
*Living Reviews in Relativity*, a free online journal of review articles- “Golden Oldies“, reprints and English translations of classical relativity papers, reprinted in
*General Relativity and Gravitation* - General Relativity, Luca Bombelli, broad, terse, and technical compilation of references

#### Textbooks

There is much overlap between the different textbooks, and generally they are all good. Hence this list focuses on the *unique* strengths or topics of each book, and is a work in progress.

Introductory: I recommend Hartle’s book to start with, assuming you are a university-level physics student; it takes a “physics first” approach, getting straight into the good stuff, avoiding dry mathematical foundations which is still the bane of many traditional courses, only introducing maths as needed, with wide range of topics but clear introduction. Just one area of good coverage: tidal forces, Newtonian and relativistic.

Taylor & Wheeler’s *Exploring Black Holes* is even more introductory, requiring just high school calculus, though insight for expert readers also, a brilliant combination of top expert (Wheeler) and science educator (Taylor). metaphors “rain”, “hail”, “drips” for radial motion. The Lorentz boost from Schwarzschild to Gullstrand-Painlevé coordinates fascinated me, even though a flaw in the proof. Love the description of measurement by a “raindrop”, Schwarzschild *r* is the radial distance, length-contraction and coordinate interval precisely cancel.

Schutz is known for its precision. I recommend to come back later and clarify your understanding of basic concepts. As someone wrote, “If you really want to know what a tensor is…”

Intermediate:

Carroll (2004) is excellent, being precise yet readable

Treat Misner, Thorne & Wheeler (“MTW”) is the classic from its era, covering most as an encyclopedia, look up an entry, not read through (more so than other GR books). Since it is a “classic”, I take it as a guide to what is “standardly” known: if something is found in MTW, then it is a standard result

Reviews: Chris Hillman