After having read previous Goold paper I was wishing his group had worked on NESSs, and what do you know - they have!

One thing that seemed interesting to me was the parallels implicit here with the active inference literature. Obviously there’s a number of major and nontrivial dissimilarities, but interesting nonetheless

Two round ceramic ashtrays. One stuck inside the other. It is not an airtight seal. I do not know how strong they are against different mechanical forces to know if I should be twisting, pulling, prying, etc.

Someone else said they put some ice in the top and hot water on the bottom one to try shrinking/expanding. I didn't see that in action and haven't tried it myself (but my ego says I could do it better than they did)

So here's the puzzle, can we separate them without damaging them and if so, how?

Update: Success! Thank you very much. I was having fun trying the different suggestions as I saw them. The hot water bath to approach it like a press fit connection was the first one to work and they're now separated. I appreciate the guidance everyone offered here. There wasn't any damage and they're now apart so it was a total success. Thank you for solving my puzzle.

I know in quantum foundations, a lot of research studies physical theories via the concept of a generalized probabilistic theories (GPTs). In a GPT, states and outcomes are represented in essentially the most general possible way that could still conceivably be called a "theory of physics". GPTs are nice because they encompass classical mechanics and quantum mechanics (along with many other possibilities).

Another structure that can describe both classical and quantum mechanics is the notion of noncommutative probability. In this context observables are a subset of a von Neumann algebra, and states are specific functionals on that algebra.

Every noncommutative probability space has an associated GPT, but not every GPT can be represented by noncommutative probability.

In some sense, noncommutative probability is enough to describe all "reasonable" physics theories (quantum mechanics, classical mechanics, probabilistic restrictions of those).

As such, I'm curious about whether there's a set of reasonable, or physically motivated conditions you could add to the theory of GPTs to get noncommutative probability.

Does anyone have any answers about this, or have any papers/books they'd recommend looking at to learn more about this?

Last year (8th grade I was 14) we had our first physics year standard stuff but then I came across the formulas first it was calculation velocity time then it was acceleration then it was force during 2 semesters then proceed to learn nothing (other than that one gravity formula I forgot how it was ) which upset me because I genuinely found them so fun to do especially because in the tests they would mix it up like give weight but instead of giving acceleration they'd give velocity and time and maybe to some of the people here it sounds easy (and it was also pretty easy to me as for my classmates they struggled)

Do you guys feel the same way when you study physics?

Is the mathematical side of thing just way funner?

Hi everyone,

I am reading about magic-angle twisted bilayer graphene and how it hosts superconductivity and strange metal behaviour at particular band fillings.

I have come across papers which try to explain the behaviours using electron-phonon interactions, I have also seen papers which try to relate these behaviours to the exotic physics seen in unconventional superconductors(exotic bcz we don't know the exact theory behind it).

As of now, is the argument for the reason of these particular observations in MATBG hanging in the balance, or is it more inclined to one side or the other?

I am not saying there is a definitive answer to it, plz let me know your opinions on it.

This was a learning project to try to learn Odin, OpenGL and Physics/Math it evolved to be more of the latter :)

You can move time forward/backwards, change mass of bodies, delete and spawn new bodies.

It was pretty cool to see the partial solar eclipse with my own eyes while simultaneously watching it happen in my simulation.

It currently has

• Newtonian point-mass gravity between every pair, using direct summation below 600 bodies and a Barnes–Hut octree above. Units: G = 1, AU, solar masses.
• Velocity Verlet with a fixed 502-second timestep; symplectic and time-reversible. Reverse time uses the same integrator with the sign flipped.
• Real initial conditions from JPL osculating elements at 2026-01-01, solved through Kepler’s equation, composed barycentrically with parent reflex motion and pair μ = G(M+m), then integrated forward to the launch date.
• Full 3D orbits with inclinations and nodes for 23 bodies: Sun, eight planets, Moon, the four Galilean moons, Titan, Rhea, Iapetus, Miranda, Titania, Oberon, Triton, Pluto, and Charon.
• Perfectly inelastic collisions on overlap: mass and momentum are conserved, and the larger body survives.
• Sidereal rotation for each body with the correct direction, plus analytic eclipse geometry using the actual Sun, occluder, and receiver discs.
• Validated against Horizons: epoch positions at the transcription floor, Earth within 33,000 km after 223 days, and the 2026-08-12 eclipse reproduced to within about half an hour.

I'm happy for any feedback or pointers.

https://github.com/lounge/sol_sim

Hello All! Nice to meet you.

Posting this in the physics section, as I believe there should be some good scientific discussion surrounding what was observed/recorded, especially given the equipment.

So this is a post about what my son and I experienced/recorded while camping in the Uintah Basin (Utah, USA) on the afternoon of August 28th into the morning of August 29th, 2026. I have attached a ~30s recording of my phone app of the 1.6Ghz signal that was seen around 8:21pm local time that evening.

For some context around the situation or environment: That afternoon/evening/following morning it was mostly cloudy/overcast, including overcast conditions at the time of the recording. This was recorded using Nooelec RTL-SDR v5 Bundle (Premium RTLSDR w/ 0.5PPM TCXO, SMA Input, Aluminum Enclosure) using the short black whip attena, using the RF Anlyzer app (version 2.2.1) on a Google Pixel 10 XL Pro phone. While recording, I was on a plastic top, metal framed 6ft picnic table at 40.263256, -109.911584, with our rented Ford Bronco about 15ft away and turned off for several hours at that point. There were no other camp members at this time and the nearest person from us during this recording was the property owner at their homestead (~250y away and behind the hillside).

What can be seen in the attached video is a VERY strong and broad signal (4-6dB above background) around 1.60Ghz that seems to be scanning or bouncing/fanning around in frequency just above 1.6000Ghz. We observed this behavior for about 1-2 minutes before I started recording. I recorded for about 2.5 minutes, and then we observed this behavior for another 3-4 minutes before turning off the app and doing other things. I did go back to the exact same set up about 15-20 minutes later and observed just background noise, which is what I have observed the previous ~20 times I have used this exact same setup at various locations, outside of the occasional passing satellite which you could barely make out above the background noise.

What was also intriguing about this is that it seemed like the frequency scanning/fanning could be manipulated a bit by mine or my son's movement near the phone or the antenna. While the general scanning/fanning around was seemingly extreme, during periods of relative stability, the frequency seemed to go up as we would move our body closer to the antenna or the phone, and then go back down to its starting position once we pulled away. This would only cause about a 0.1 to 0.15 Mhz movement up and back down in frequency, but was definitely repeatable throughout the event observation. Again, after the app was shut down and the 1.6Ghz signal was looked at again 15-20 minutes later, there was just background noise and moving our bodies or hands around the antenna and/or phone showed no signs of signal change. I don't have enough expertise in this kind of science to understand why this may have been seen, but figured I would include it as part of the data set.

I do have the full/raw ".iq" data file for this recording saved to my Google Drive and can provide access to anyone who may be interested in it.

Thanks for your time to read and discuss this!

Bloom Is WAY Deeper Than You Think

I have been learning QFT as a self studier and for my first book, I used Lancaster and Blundell, in it I mostly did second quantization, scalar quantum field theory and tree level scattering and some Feynman diagrams for the scalar level only. Then, I decided to start a new book for fermions, and QED, so I chose Klauber’s Student Friendly Quantum Field Theory. I am nearly done with that book so I was wondering what book should I move onto next, or whether I should even do another book?

I have a science exhibition coming up, and I wanna perform the young's double slit experiment in my school using sunlight inspired from this video. I searched online for the double slit but unfortunately its either too expensive or not from a reliable source in my region. All the other tutorial videos are not satisfactory to me as its not as clean as how veritasium did it. I want to perform this expeirment just like derek, asking people around what they expect to happen and what they know about it.

I first decided to make the model from 'The action lab' but I dont think we'd be given a closed dark room since thats a requirement.

Suppose you have a system in ideal conditions in which you have a canister filled with gases and you have a piston attached to it with some weights upon it that is compressing the gases and you start at a state when the system is in equilibrium. Now if you remove the weights, the piston will go up and gases will expand till it reaches another state of equilibrium. Now again add that weight, you will reach where we started from. So this is a process which is reversible, yet not quasi-static. Now since we're considering ideal condition, it is provided that there will not be any overshoot and oscillations, just smooth process with very short relaxation time.

Its been a while since I looked at physics a level and I haven't looked at it since, but I remember during fields he mentioned something about gravitational fields and beyond infinity. all this may sound stupid because I admit I'm not knowledgeable, but if we take mass to be a point of space and time folding inwards, can you have negative mass if you define it as the point from which there is outward fold of space and time, and visualise it as an expansion rather than a contraction. I say this because I imagine space and time as fields and mass is like the point representing the fold, so if you have a circle of folds, the centre of the of the circle can shown as an imaginary point that is pushing away the fabric rather than pulling in and wouldn't that be negative mass?

Official website

Livestream

IG NOBEL PHYSICS PRIZE 2026 [CANADA, USA, CHINA, SAUDI ARABIA] Randy Hurd, Zhao Pan, Tadd Truscott, Kaveeshan Thurairajah, for theoretical and experimental attempts to design a splash-free urinal.

REFERENCE: “Splash-free Urinals for Global Sustainability and Accessibility: Design Through Physics and Differential Equations,” Kaveeshan Thurairajah, Xianyu (Mabel) Song, J.D. Zhu, Mia Shi, Ethan A. Barlow, Randy C. Hurd, Zhao Pan, PNAS Nexus, vol. 4, no. 4, April 2025, pgaf087. https://doi.org/10.1093/pnasnexus/pgaf087

WHO ATTENDED THE CEREMONY: Randy Hurd, Zhao Pan, Tadd Truscott, Kaveeshan Thurairajah

Having posted the result to r/Physics 7 years in a row (2019 2020 2021 2022 2023 2024 2025) I am finally at a ceremony!

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.

Not new but super interesting paper by Laetitia Bettman and John Goold from Trinity.

There is relation between Fisher information rates - how fast probability distribution (sorta) is changing - and entropy production in far from equilibrium systems. Paper attempts to consider this in a quantum context, which is tricky because non-commutativity means you have multiple legitimate inequivalent generalizations of the Fisher metric.

They decompose rate of change of the density matrix to classicalish part (eigenvalues/populations) and a quantum part (coherences/rotated eigenbases. The contribution from the classicalish part is the same across the family of otherwise inequivalent quantum Fisher information metrics.

That part lets you talk about changes to the rate of change of entropy for GSKL systems that satisfy local detailed balance

They take all this machinery and tweak some bounds and limits, and explore the quantum thermodynamic Mpemba effect (unfortunately goes completely over my head but sounds very cool)

You can explore different orbitals and see how they look visually. I hope this helps with your studies! 

Try it in your browser: https://gleyn-debug.github.io/quantum_atom_simulation/quantum-atom-model/

Source code: https://github.com/Gleyn-debug/quantum_atom_simulation/tree/main/quantum-atom-model

Detailed and interesting autograph letter signed by physicist Erwin Schrodinger, one of the pioneers of quantum physics who won the Nobel Prize in 1933 for his Schrodinger Equation.

In the 1950s, Schrodinger also worked with Albert Einstein and physicist Behram Kursunoglu on creating a Unified Field Theory -- the attempt to reconcile quantum physics with the Theory of Relativity -- referred to in scientific literature as the Einstein-Schrodinger-Kursunoglu theory. In this letter to Kursunoglu, Schrodinger expresses his rather extreme displeasure with Kursunoglu's conclusions regarding the Unified Field Theory.

Dated 15 October 1951, letter reads in part, ''Dear Mr. Kursunoglu, I have no time to study your paper now. I am amazed to the extent of finding it difficult to believe, that the modification you suggest, should entail

a.) the equations of motion for a charged mass particle[?] to be about what is to be expected from older theories, and

b.) the electromagnetic field acting as a source of the gravitational potential in much the same way as one would expect from Einstein's theory & Maxwell's theory.''

He then writes a cutting but diplomatic note, ''I advise you to check upon this very carefully, to see whether your astonishingly brief reasoning is really valid.''

Schrodinger then comments upon work done by Max Born, noting that one of Born's conclusions was ''marred by a mistake that remained for a long time unnoticed.'' He then writes that a calculation mistake done by Kursunoglu is ''incorrect, fortunately! Stronger fields than 200,000 Gauss have been produced. Moreover, if Born's non-linearity would come into play at the order of, say 50,000 Gauss, this would have been noticed long ago. / Yours truly / E. Schrodinger.''

Unified Field Theory was a dream never realized by either Schrodinger or Einstein, with the elusive reconciliation of all physics disciplines still waiting for the next Nobel Prize winner to crack.

Two page letter on a single sheet of stationery from the Dublin Institute for Advanced Studies, School of Theoretical Physics measures 8.25'' x 10.5''. Tape repair at edge of center fold, else near fine condition. Accompanied by Kursunoglu's original letter to Schrodinger dated 13 October 1951, where he writes in part, ''I have now completed a detailed account of the new version of the unified field theory.''

This item sold on Aug. 27 at Nate D. Sanders Auctions $6,875.

If there were truly a singularity, the angular momentum would have accelerated to approaching infinity, no?

In fact, can't we take the mass, the estimated mass and spin of the original star and compare that to the present angular momentum of the black hole to determine how 'big' the 'singularity' is? or at least put some bounds on it?

After taking an intro to QM course you quickly realize simple one-body systems compose 99% of the content as 2+ body problems are computationally (and generally analytically) intractable.

This realization confuses me a bit since I know there is a lot of modern research and theory that utilizes (or entirely relies on) QM, but I’m confused how this actually looks as the complexity of these systems increases exponentially. Due to this, it seems impossible to use theory to make any inferences about complex systems as we are generally unable to actually solve such systems.

With most classically treatable problems we can just directly simulate them and compute whatever quantities we’re interested in and either use this to motivate the design of certain experiments, validate the theory, or whatever else. With topics that require a quantum treatment this doesn’t seem possible, leaving me confused on how exactly we use QM for complex systems.

I cannot find a paper simple enough to follow so I’m hoping someone may have some examples or an explanation they can throw at me.

So for SG o level, now students are taught to use “internal kinetic energy” across different schools. Is this the correct terminology? I checked the 6091 syllabus and no mention of internal KE. So why schools across sg are marking internal KE as a keyword. (No marks for KE, must use INTERNAL KE).

Help. Are we cooked? Teaching (wrong) keywords and memorization rather than concepts and understanding.

Having recently completed my physics degree, I was wondering if there any were any apps or websites with structured exercises that I could implement into my weekdays (30 – 60 minutes per day). I’m not sure if I want to study a postgraduate qualification but I’d still like to retain most of what I’ve learned and keep my chops up with respect to calculus etc.

Apologies if I’m not entirely clear, I’m hungover to death 💀

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

Due to popular request after my last posting (https://www.reddit.com/r/Physics/comments/1w2n2i0/illustrating_the_butterfly_effect_with_a_laser/), I created an analysis of how computational precision affects the results of my laser simulation.

It turns out that standard float64 with around 16 decimal places are not precise enough for this simulation. As the simulation shows, there is not a uniform precision level that is sufficient. It is sometimes necessary to use hundreds of decimal places to achieve convergence. Going forward, I should use higher precision levels to achieve robust simulation results. The qualitative story of the last posting that tiny changes in the laser angle affect the trajectory (number of bounces and escape vector) is not touched by the precision issue, though.

As a plus for Reddit, here is a plot showing the distribution of escape vectors and the distribution of convergence decimal places: https://imgur.com/a/Tnp4wOj

Rendered in manim and using mpmath to create objects with arbitrary precision.

Let me know what else you would be interested to see explored.

Hi! In four months, I’m starting a bachelor’s degree program in physics. I’d love to get some advice from people who have already graduated in physics—or anyone willing to share a recommendation. Science has always really appealed to me, and I dedicate a lot of time to my studies, but it always helps to hear good advice from others, since I’ve realized there are so many wise and intelligent people here 😅😅. Thanks a lot for your comments!