The world around us is mostly electromagnetism. youtu.be/Sj_GSBaUE1o?si=rn65… When you touch something, the electrons in your hand repel the electrons in the thing. That’s why your hand doesn’t go through the thing. Also, the fact that you have a hand in the first place, is due to the chemical bonds that hold the atoms in your hand together. And what is chemistry, but the study of how atoms interact electromagnetically? Then there are the more evidently electromagnetic things. Electricity, magnets, lightning, computers, your brain, all that stuff. And then we’ve got light, radio waves, X-rays, microwaves, all of which are the flopping around of the electromagnetic field, whatever that is! Actually, just about everything in our world is electromagnetic. Sure, there’s a bit of gravity in there too, to keep us from floating away. And yeah, the strong nuclear force is sometimes unleashed, but it usually remains locked in the nuclei, only passively participating in our lives by giving matter 99% of its mass (you’d only weigh a pound or two if not for the strong nuclear force). And also, our existence is graced ever so gently by the weak nuclear force, but that’s really just part of what electromagnetism could have been, if not for the Higgs field. So when you look around, almost all of the world around you, and all of the ways in which you see and sense it, is a manifestation of electromagnetism. But wait… what is going on here? Have you ever been in a dream, and there’s something obviously unusual about the situation, but you just don’t think to question it? For some reason, you just go with it? But then you wake up and realize, wow, I can’t believe I didn’t realize how weird that was! Hey. I’m not saying you’re in a dream. But. Why is electromagnetism a thing? … To most people, that sounds like one of those big questions that we’ll have never have an answer for, like “why are we here” and “what is the purpose of life” and “how do you pronounce gif”. So, maybe the reason people don’t often ask why electromagnetism is a thing, is that they don’t dare to believe that a satisfying answer might exist. You can’t just go tapping into the source code of reality to figure out why electromagnetism is a thing, right? Wrong. An answer does exist. Electromagnetism can be derived from just one symmetry principle, along with a few observations about the nature of space and time, energy and momentum. Those who have studied physics in depth will know that local U(1) symmetry blossoms into electromagnetism, and they will all agree that this is one of the most beautiful concepts ever. It hits you like a spiritual epiphany, and once you see it, you can never unsee it. It changes your view of the world at a fundamental level. This is one of the greatest joys in life. So, I wanted to make a video for grad students (and ambitious undergrads) who are studying physics, or are physics-adjacent, that shows how electromagnetism arises from local U(1) symmetry. There are videos out there already which sort of describe the concept, and talk around it, without really getting into detail. And that’s fine. But let’s really get into it, ok? Let’s examine the topic with the intensity it deserves :) Even though the video is like 3 hours long (hard to make it shorter while doing the topic justice), I hope that the video format can make it an efficient learning experience, relative to how long it usually takes to learn physics. And you have the ability to skip around, or pause it and come back later, so think of it as a video textbook. It might be a bit much to watch all in one sitting, frankly. But it’ll be there for you when you need it, and I hope it’ll be a helpful learning resource for you, on your journey to understand the nature of things. As always, I’d love to hear your thoughts! What did you enjoy about it, what could have been done better, what topics would you like to explore next? #physics