The professor drops a lot of formulas throughout the class. While he often does not give explanations as to where they come from, he will explain them in his office hours. Reused questions from the homework for midterms and questions from the midterms for the final. Going to class is essential.

This class took away any doubt I had about majoring in physics. Regan started off at a hundred miles an hour with geometric algebra and stat mech but backed off quite a bit after the first midterm. The first 3-4 weeks were absolutely terrifying, especially since his lectures moved incredibly quickly. Don't try to take notes during lecture unless you already have some understanding of what he's talking about - he complained a lot about the textbook but ended up following it pretty closely, so try to at least skim the section before lecture. The class slowed down a lot after midterm 1 when we got into the background and very basics of quantum, which was by far the easier part of the class.
He assigned a lot of homework but was very forgiving with deadlines and his exams were very fair. Learn the homework well and you should be fine for the exams, many of the problems were similar or identical to ones we had already seen. Also, don't expect to get much homework/content help from office hours - Regan would always start off trying to answer questions but would quickly get distracted and go off on tangents about his own interests. This ended up being my favorite part of the class and I would highly recommend going, he brought up so many little things that made me even more interested in physics. He has a thing against the cross product as well as hbar and other "fundamental" constants like c and the Boltzmann constant and prefers to describe everything in terms of frequencies but he won't force that on you in exams. In summary - Regan is a little crazy and makes you feel like you have no idea what's happening but taking it with him is absolutely worth the extra effort, at least it was for me.

cool guy, take him if u want to learn, don't if u just want it easy.

most importantly, what I like about this professor is that he teaches well. He tests the concepts he emphasises on, and it is relatively easy to get an A in his classes without obsessing over them like most try-hards do
(yeah I mean the Knudsers.. who spend all their day in the physics building)

He is easily readable. You can tell what he will test you on by how big his smile is when he teaches the concept. Focus on the topics that bring out his ( inspiring but lowkey cringy) enthusiasm .... and you ll get the A

Professor Regan knows his stuff, and that's an understatement. He clearly has an extraordinary grasp of quantum mechanics and does his best to impart that to students. There's two downsides to this, though. The first is that it makes it hard for him to realize that students may have some difficulty with the concepts. They might be second nature to him, but they're entirely new to us. Yet he assumes that we are as comfortable as he is, and races through topics like the goddamn Road Runner getting away from Wile E. Coyote. The other problem, though (and this is arguably the worse of the two), is that Regan's self-perceived mastery of physics makes him an insufferable asshole. Just absolutely so far up his own ass, he's basically wearing his head as a beret.

With that said, I will reiterate that Regan is very knowledgeable, and he does at least try to share that with his students. Sometimes he goes a bit too far and too fast, but it's clear he is making an effort, which I appreciate. And it works. I do feel like I have learned a good amount in this class, that I may not have if he had not focused on the fundamentals like he did. In addition, his exams are insanely difficult and nearly impossible to finish in the allotted time, but he seems to be fair about grading and curving them, so the end result isn't too bad. Moral of the story then: really smart guy, raging asshole, medium teacher overall.

cool guy, take him if u want to learn, don't if u just want it easy.

most importantly, what I like about this professor is that he teaches well. He tests the concepts he emphasises on, and it is relatively easy to get an A in his classes without obsessing over them like most try-hards do
(yeah I mean the Knudsers.. who spend all their day in the physics building)

He is easily readable. You can tell what he will test you on by how big his smile is when he teaches the concept. Focus on the topics that bring out his ( inspiring but lowkey cringy) enthusiasm .... and you ll get the A

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.