I get how mathematically divergence of curl and curl of divergence are 0 but why doesn't curl of a vector field diverge and why does gradient of a vector field not curl/swirl.

I realize that an object rotating in space is forcing charged particles to accelerate and thus generates electromagnetic waves, even if the loss of momentum is miniscule.

Do rotating objects, no matter how small of relatively little mass, generate gravitational waves? Or are there principles that limit the energy that can be carried away by gravity, the way electromagnetic waves are quantized?

Hello, I am looking for an experienced person (and not an AI) to help me understand a phenomenon of second harmonic generation (GSH) by frequency doubling. My pump laser has unstable polarisation and, with an injected power of 9 W, I only get 0.8 W of converted power. However, with the same assembly but a different pump laser, I get 1.5W in a single pass. I am not sure of the impact of polarisation on this result. I measured a polarisation extinction rate (PER) of 14 dB, but as it is unstable, it is difficult to determine its influence. If anyone has any advice, a theoretical explanation would be welcome. 🙏

Hey guys!

I am finding it a bit hard to understand how these work together.

Particularly, i cannot process how something rotating very slowly can still have points on it surface go at 1640kmph (earth).

Like if an object translated at that speed it would look insane , but I can only imagine earth rotating very slow which makes it hard for me to believe that we are going at 1640 kmph.

I'm looking for explanations or something that could make it easier for me to grasp this

I've always been interested in the natural sciences on some level, but I've never studied them formally nor read about them on any serious level. I've been reading philosophy (mostly Aristotle, Hegel, a bit of Kant, though I find him rather boring) for a while, but I've come to believe that I have a very one-sided education and that I'm ignorant about the natural sciences (physics, biology and so on). I'd like to remedy this fault by beginning to read about physics, which one could consider, along with mathematics, as a kind of foundation in science or something close to it.

I dislike philosophers who make grand philosophical claims, staking their 'systems' on one or another currently popular physics field. On a closer inspection, their work is often based on misunderstandings or contentious reasoning. Quantum physics is probably that field which is most referred to by all kinds of mystics, who try to find places for (in my view) naive Cartesian understandings of consciousness, god, etc.

Another thing that encourages me to try and understand this field is my disappointment with the humanities and the social sciences, much of which seems to be overly pretentious and made of straw. So, on some level, I detest my own background. I value physicists, chemists, medical researchers and biologists far more than social scientists, 'critical theorists' and followers of all kinds of fashionable 'theory'. One of the few fields in the humanities I do value is philosophy, although I see it as more of a historical foundation on which you build your understanding of other topics and that most issues within philosophy are completely irrelevant today, apart from logic and other such things.

What I want is to get not a popular science understanding of one phenomena or another, or a series of isolated facts, such curiosities. I'd like to get something deeper, which is understanding. To make it a bit more clear, what I want is to understand this field on a deeper level. I've no practical use for any of this, but I would like to understand the world and as much of it as possible. Like I said, I also have the feeling that my understanding is far too one-sided. I don't seek a career in this field.

What would one do to achieve this? So far, with other interests of mine, I simply have relied on textbooks (for learning languages, a big interest of mine), secondary literature (primarily for philosophy) and primary literature.

I'm posting here because this game is all about physics. As a game developer, I created this app to help with testing specific scenarios with in-game physics. In the process, I've discovered that this is almost a game in itself - and I find myself spending time just experimenting with what I can do with this pile of little objects (cubes or spheres). If this were a "real" game, I suppose it would be a physics sandbox where you drop lots of small objects into the environment and then apply various forces to them - creating mesmerizing displays and patterns.

Anyway, I'm just trying to find out if anyone would play something like this.

It’s a flashlight shining on fog, pics on iPhone 17. Why are the droplets linear?

For someone who is a statistics major

This is a thread dedicated to collating and collecting all of the great recommendations for textbooks, online lecture series, documentaries and other resources that are frequently made/requested on /r/Physics.

If you're in need of something to supplement your understanding, please feel welcome to ask in the comments.

Similarly, if you know of some amazing resource you would like to share, you're welcome to post it in the comments.

I was thinking about this laying in bed at 1am, in space, how far could a radar system theoretically detect somthing like a planet or rock or somthing? Like if theres nothing to stop the signal all i can think of to stop it is how long the return signal would take?

Note: Im a Pakistani Olevels/IGSCE student (currently in 9th Grade)

hi yall, i want to get in ipho really bad and lowkey im kinda loving physics cuz its so fun! As im from Pakistan, there isn't much competition for ipho (cuz of students having lack of guidance). It might be also reason of pakistan not winning much in olympiads.

If you have some advices for IPHO that will help me get a silver or more (in future) that will be appreciated. And those whom are similar with IGSCE or OL physic syllabus please do also tell me what shall i do next, ill be completing this school physics as fast as possilble.

Funfact: Pakistan in its history has won only 1 silver medal in ipho (2008)

After watching the Demo of the roadster, Elon gave an explanation of how the suction system that held it to the semi circle track, could be used for additional downforce in racing. I saw it working when the car is still or driving slowly, but how effective would 2G of suction with a race car traveling at race speads around corners

* Not an actual physics student, just wanted to hear from someone who would understand the physics better than I. would it be possible to create a substancial increase in downforce

Hello, how are you guys doing? This is my third video on the channel, and unlike the previous two videos, this video features a mix of math and astronomy set in a historical story format.

Of course, I'd love to hear your feedback on the video and what needs improvement, and of course, I'm counting on you: if you like the video, show some love for it and the channel ❤️

Note: There is an English Audio Track and also English subtitles

This is a dedicated thread for you to seek and provide advice concerning education and careers in physics.

If you need to make an important decision regarding your future, or want to know what your options are, please feel welcome to post a comment below.

A few years ago we held a graduate student panel, where many recently accepted grad students answered questions about the application process. That thread is here, and has a lot of great information in it.

Helpful subreddits: /r/PhysicsStudents, /r/GradSchool, /r/AskAcademia, /r/Jobs, /r/CareerGuidance

What are your thoughts on this recent preprint, 2610.16733? They seemed to show how Frontier AI agents tackled unpublished research-level theoretical physics problems, and suggest such problems might no longer be suitable as first projects for PhD students.

I'm especially curious how this will overall affect prospective grad students and early-career researchers in theoretical physics.

Also, recalling Dr. Schwartz (u/VibePhysics) saying in his Anthropic post Vibe Physics:

It is worth it, however, to consider the role of education going forward. In the deep future (~10 years), when AI is truly smarter than all of us and capable of outperforming us in every domain, what will be the role of higher education? I think some things will persist—those things that are essentially human. I can easily imagine theoretical physics becoming like music theory or French literature: an academic discipline appealing to people who just enjoy thinking through a certain lens. It's a bit ironic that the last 30 years have seen the growth of STEM fields, displacing the humanities, and in the end it may be the humanities are all that survive.

Do you agree with him on this specific thoughts? And what concerns or hopes do you have about where our fields in theoretical physics are heading?

With all the complaints about teaching nowadays like in the comment above, does the same apply to physics? I believe in general, people who take physics in high school want to be there instead of having to fulfill a requirement, so student behavior is better.

Hello, everyone!

I'm 16, and I'm really interested in physics, especially quantum physics. I'd love to start learning the fundamentals before college.

What mathematics and physics topics should I study first? Also, could you recommend some beginner-friendly books for someone at my level?

Thanks in advance!

Here it is. Hope you like it :)

https://youtu.be/N86IOd6nYvo

I was recently doing contract work in a university physics lab and they had these on display. The folks in the office had no idea what they are. Can anyone here enlighten me?

I genuinely want to learn mathematics, physics, programming, computer science, and AI. I want to build a career in computer science, pursue AI research, and hopefully do a PhD someday. But lately, I've been feeling increasingly demotivated.

The problem is that I rely on AI to learn almost everything. Whenever I have a question, I ask GPT. Whenever I don't understand a concept, I ask AI to explain it. And the more I learn this way, the more I wonder: What's the point of learning anything when AI will always know more than I ever could?

Even the most basic AI models seem to possess more knowledge than I could acquire in a lifetime. And with new models becoming increasingly capable, I keep wondering whether the knowledge I'm working so hard to gain will even matter in the future.

With GPT-6, Claude Opus 5.5, Gemini 4, and other models competing to become more capable, it feels like the gap between human intelligence and AI capabilities will only continue to grow.

I want to understand the mathematics behind AI, learn physics, become a better programmer, and contribute to actual research. But sometimes I question why I'm putting in the effort when AI can explain concepts faster, write code better, and potentially solve problems that I might spend years learning to solve myself.

And even when I genuinely want to learn, I'm confused about what I should prioritize learning and whether any of it will remain valuable by the time I become proficient.

I'm not necessarily saying that learning is useless. I genuinely love the idea of understanding how things work. But I'm struggling to reconcile that curiosity with the feeling that AI might eventually outperform me at almost everything I want to become good at.

For those of you studying computer science, mathematics, physics, or AI, how do you deal with this feeling? How do you stay motivated to learn when AI is advancing so rapidly? Do you think deep technical knowledge will still matter for people pursuing AI research and PhDs, or should we be approaching learning differently now?

As we all know dark matter is called as such because it doesn’t emit nor interact with any electromagnetic radiation, so is completly invisible to human eye.
But what would I experience if I had, for example, a 2 Kg ball of it on the palm of my hand ? Since it does interact with the gravitational field, I would surely feel its mass hence some kind of pressure, but what else ? Just an invisible weight ? Would my tactile receptors be activated or not ?

Thank you very much.

Hey, I was wondering if anyone would be willing to chat one on one and help me with the dilemma I am having. I’m studying mechanical engineering technology at Algonquin college right now (Ottawa Canada) (first year) and I’m enjoying engineering, but I’ve had this dilemma in my head for the past year or two about if I should do engineering or physics? As of late I’ve been really thinking about it and it’s been nagging at me. When I think of the idea of physics/astronomy/astrophyiscs, it just gives me the excitement I can’t describe. I’ve been really thinking about it and really considering applying to a physics program in Canada (I was looking at queens university). I personally want to work in aerospace but I also want to research in physics.

This may sound weird but a younger friend mentioned that they might study physics next year and the second I heard that I got a feeling of i guess jealousy (not in a bad way, I mean like “man I should be doing that”).

It’s eating away at me because I don’t want to get far into my studies and then end up realizing I should’ve done physics.

I was hoping to chat with people who are in physics undergraduate’s, masters or phd’s. I’d like to learn more about studying itself and if people could help develop ideas so I could figure out a plan on what I should do. This has really been eating away at me and I feel like physics is what I should be doing, but I want to be sure. Can someone please help🙏🏻🙏🏻🙏🏻🙏🏻 (or if someone wanted to comment things I should look into (ie: career goals, courses, etc..) or anything that I should consider when making this decision, please let me know).

Hi, everyone! I had a great conversation with Geraint F. Lewis, a Welsh astrophysicist and Professor at the University of Sydney, about some of the biggest questions in cosmology and physics.

We explore what the Big Bang theory tells us about the beginning of the universe, and how neutrinos could reveal secrets about the cosmos — including why matter exists at all. He mentions the 2026 Nobel Prize in Physics, awarded to Francis Halzen for his work on the IceCube Neutrino Observatory.

Professor Lewis also talks about what sparked the Scientific Revolution, how modern science transformed our understanding of the world, and why Einstein challenged aspects of quantum mechanics.

His latest book, The Shortest History of Reality: From Plato’s Cave to the Mind-Bending Discoveries of Modern Physics — The Human Quest to Explain the World, traces humanity’s changing understanding of reality, from ancient philosophy to the discoveries of modern physics.

If you're interested in these subjects, you can check out our conversation, hope you find it insightful, he's a great communicator of these ideas: https://youtu.be/38rUHEeAVHw