This class was extremely difficult I would recogmend not taking it with him. This class is also technically skippable. If you must take this class take it with a diffrent professor.
He is a great guy, funny, and lectures well. But his exams can be astronomically difficult.

Regan is a cool guy, I like him a lot and he clearly cares about the welfare of his students, but fuck this class is hard. I'm a CS major, I don't care about physics, and I really don't want to spend the amount of time required to do well in this class on physics. It's probably a good take if you will do physics upper divs, but it's not for me.

Regan doesn’t know the material, and doesn’t want you to know it either. 17 is supposed to be an introduction to atomic phenomena and some elements of quantum mechanics. He refuses to make a class that is in itself supposed to be easy actually digestible, by including as much content as possible, and presenting it as superficially as he can. He mentioned geometric algebra (cause I cannot use the word “taught”), only to not use it again in the remainder of the course. He usually starts using some physical concepts under the umbrella of “I’ll make it clear later” and then forgets to define it properly until everyone is utterly confused. He spent an entire lecture talking about fermion and boson statistics, which required attention to the effects of spin-coupling. He used the word “spin” about 30 times that entire lecture, without defining spin once. The first question he was asked after the class was “What is spin?” He went out of his way to give the most rigid, abstract, confusing, and mind-boggling presentation of one feature (the turning of a playing card), instead of defining it for the means of a lower division class. The student was visibly confused. They were speechless. Regan smirked and moved on. He didn’t even ask the student if it made sense. He just moved on. That happened to me too. He just doesn’t know the material profoundly enough to actually answer questions, or teach for that matter. And he enjoys confusing his students. Otherwise, he would not smirk so visibly when someone doesn’t know something.
His homework is unreasonably difficult. He always taught the concepts needed for 80% of an assignment the day it was due. Since his lectures lacked any conceptual insight and were nothing but regurgitations of formulas, the assignments felt demoralizingly difficult. And the grading was harsh and lazy. His homework problems had a lot of subsections, and if you had one typo for one, your score for that problem started from 75%. It didn’t matter if everything but your answer for one subsection out of say 5 was perfect, you still got a 75% for the problem.
His exams require literal memorization of problems, instead of conceptual understanding. Preparing for exams was a witch hunt of “What could Regan decide to test us on?” He didn’t teach what a blade in geometric algebra was. He briefly described it in some typed lecture notes on his website. We got that on our exam. And he shamed us publicly for not knowing it in the lecture notes.
Regan is too concerned with trash talking other physicists to actually do his job. He builds his personality on the hate he has for the textbook, the constants in physics, or different historical concepts. No human being should build a personality on what they hate. That is not just counterproductive, but harmful. As a physics major, I want to be encouraged by my professor’s love for physics, not their hate for what they perceive to be “stupid.”
Don’t take his class. Just don’t. As a physics major in college you deserve a professor that is knowledgeable, passionate, and sincere. Regan is none of those things.

Grading: I got an A without really understanding anything and get about the average on every midterm/final. Still very confused about that curve. The averages were around 55-65%.

Prof: Take Regan if you really understood 1B, if not, you're kind of screwed. You also have to understand the readings that were supposed to be done each week and took about ~2 hours each for me. He makes the assumption you know all that information going into lecture. Which is great if you do because then he teaches very well at that high conceptual level. If not, then you'll be in week 10 and see him write Maxwell's equations every lecture and still have no idea what they mean.

Regan: cool funny guy
tests: crazy hard
homework: ALOT
hbar: stupid human constant
don: enlightened
the curve: GNARLY

fr fr tho, prof is super dope, funny and knowledgeable. He teaches QM with his own twist, which was weird at first but later it kind of grows on you.

This class for most of the quarter was quite difficult and had me questioning my major. There were two midterms, a final, and a bunch of homework. The homework was very doable and Regan would almost always extend the deadline. The midterms were difficult but overall I would say they were fair. The final was also fair in my opinion. Some tips for future people taking this class: 1) Don't freak out if you start off the quarter not knowing wtf is going on in the class. The first lecture petrified me and I didn't think it would get better from there, but it does. 2) KNOW THE HOMEWORK. It seems that Regan really liked pulling questions from the homework to put on the midterms/final. If you really know the homework and the ideas that were covered then you will do fine on the exams. 3) Don't freak out if you do poorly on the first (or maybe second) midterms. Since Regan curves, as long as you stay near the average you should do fine. I was below average by a lot on the first midterm, around average on the second midterm, but I crushed the final, so I ended up with an A-. For me, Regan's lectures weren't that helpful, but they were entertaining. I found myself mostly self-studying for the course. Overall, study the homework/textbook really hard and don't freak out and you should do fine.

Lemme tell you a thing or two about Chris Regan.

First of all, full disclosure I love Regan and the way he teaches this class. He probably teaches it the best out of what I've heard since I heard Paul Hamilton spent nearly half of the quarter on review in Fall. If Regan did that I think I would lose my mind. I will say, his homework was a lot, and his office hours seemed shitty since he would just go on rants. If you have homework questions, definitely find a friend or pray you have a good TA like we did.

If your goal is to do minimal work and get this class over with, maybe wait for someone other than Regan. However, if your goal is to learn and be excited to go to class then DEFINITELY TAKE IT WITH REGAN.

Some specifics:
- he spent one week on review (which I liked since I wanted to learn new shit).
- He baited us by teaching us geometric algebra, and it will seem wacky at first but its properties give INSANE intuition for Pauli spin algebra.
- He also taught way out of the book with the Dirac equation, which was fucking sick.
- lastly, his exams were super fair. Even if the homework might have been rough at times, he yoinked problems straight from the work and practice exams up to just legit changing numbers on some of em.
- most importantly, I was actually excited to go to class every day and I always felt like I was learning something new.

TLDR: teaches well, hw rough, but ez exam and curve make up for it.

Notorious for a reason. Ask around the department and they can provide you a thorough synopsis. His class is the only one I've ever happily and excitedly attended.
Iconic and difficult professor, worth it for the experience IMO

Modern physics was a cool experience! Regan definitely added his flavor to the course, which made the first 3 weeks feel a little rocky because the material taught didn't run very parallel with the textbook, but by week 9 it all came together and wrapped up super nicely. Side-note: He has a mad passion for physics, which made each lecture that much more enjoyable. The lectures are spent motivating and deriving some of the main ideas/equations that are relevant to whatever is being discussed that day. Something that i thought was awesome is Regan provided typed-up lecture notes on BruinLearn(also recorded lectures), so throughout the quarter I felt free to sit and tune-into a lecture, without feeling the need to write down everything as he lectures. Also, having a thorough understanding of the homework problems is important, as he tends to pick similar problems for the exams, so with that said, re-working old problem-sets is a great way to prepare for exams. Doing a lot problems/exercises in general is the other secret!! - solve as many problems as possible(solve them honestly!), it'll help a ton(this is probably general advice for physics/math, but it helped a lot in this course). Another thing with hw, he almost always extends the deadline, which was super nice. The exams are curved, so staying near/above the average is what really counts(obviously you want to work and shoot for the stars, but keep this in mind if things don't go so well). I was around avg on the first midterm(54%), nicely above avg on the second midterm, and did well on final. SO even if that first midterm doesn't go so well, just learn from it, figure out what went wrong and keep at it. Tbh, this class does require a lot of work, but the effort is worth it! Goodluck !!

Definitely a challenging course that demands a lot of effort and time. Lecture notes are very helpful. This class is rather unique in that we spend considerable time thinking about definition of momentum and questioning and parameterizing the framework of classical mechanics as well as the postulates of quantum mechanics. I enjoyed the historical view and the general freedom to question assumptions. However, there are considerable downsides: I really, really don't appreciate his attitude. The professor seems to lack the ability to read the room and comes off really poorly when it comes to explaining concepts or ideas you aren't familiar with. At least from what I was seeing, he contributes toward an unhealthy learning environment, not in terms of class content or fluidity of information, but an unspoken shame towards students who aren't quickly proficient and a suppression of basic, clarifying questions that some students may be afraid to ask. I would recommend utilizing a good teacher's assistant, tutor, or friends/other students in the class, especially with this particular professor. Thing is, he seems like a nice person, and doesn't necessarily intend to come off this way.