Marolf is a genius. I learned a ton of math from taking this class with him (this class will be Phys100A in the future). Great homework: difficult and time consuming, but similar to tests, and really forces you to learn the material. Super thankful that I took this class, especially for the sections about solving PDEs, expansions, and operators.

Took this in Fall 2020. Prof. Marolf is comprehensive in his lectures, but his handwriting can be struggling. 2 midterms and 1 finals. They are all easy and related to the HW and lecture. He gives extra credit at the end of the class. He is nice, patient, and creative. He sometimes incorporates student questions into the next lecture. Take him.

In the fall of 2020, the class was P/F. The exams weren't really all that bad because they cover about the same content (almost exactly at times) as the homework and the notes are all right as well. The part that detracts from the course, however, is that the professor goes on tangents at times and doesn't fully explain ideas, but I'd recommend.

Best physics professor ever. He is very passionate about lectures and the lectures are very inspiring - I really enjoy the "fancy math". I have never thought physics is something "interesting" until taking PHYS 20 with him. His HW is reasonable and exams are highly related to HW and his lectures.