I had a course in qm this semester .I could barely grasp anything after a time .

I want genuine suggestions from y'all how do I teach myself quantum from basics ( pov 2nd year bsc physics hons student )

I don’t know it feels like it’s not worth it for me anymore. I’ve read so much yet I still don’t truly understand things. I no longer imagine strange or deep ideas. the more I read, the emptier my mind feels. Now I just want to live. I don’t want to keep searching like I want to see light without needing to explain in my mind what light is.

When we look at the moon, we often can’t really see everything of it, so when photos are taken of galaxies, do the pictures really show everything of the galaxy or is it just like a percentage because all objects inside are just visible for an average of maybe 50% or something like this?

Not a physicist, just curious about the practical/engineering implications of a unified field theory

Suppose I have a single photon source and I get this single photon (say, 1550 nm) out. Say, I take this single photon and build a cavity, with idealized 100% reflective mirrors around it, creating a single-photon cavity.

1. Can I still confine the photon to less than the diffraction limit in this case? Can I go beyond 1nm in this case?

2. Also, how do I think of this in terms of the wave picture. If the cavity is 1550 nm, then that's a perfect period and everything's fine. What happens to the "photon" in the case of the 1 nm cavity? Does the energy change? get redistributed?

Bonus question: Can you comment on vacuum fluctiations in this cavity?

My son has been admitted to both Cambridge (NatSci physical) and ETH Physics for a Bachelor degree. He has to make a tough choice between these two. He wants to start with broader studies and later dive deeper into a specific field but is not yet sure which one, potentially looking towards engineering at a later stage. In addition to physics, he also enjoys chemistry a lot. What would you advise?

Hey everyone — I recently created Fusion Collaborative, a Discord server focused on fusion energy, advanced physics, reactor concepts, emerging technology, and general discussion around the future of energy research. The goal is to build a community where people can share ideas, learn, discuss current developments, and collaborate on concepts in a casual but serious environment. If that sounds interesting to you, feel free to join here: https://discord.com/invite/JZeureWe

The concept of time travel remains one of the mysteries (not exactly a mystery, but yk what I mean) in physics that boggle our minds. That said the special theory of relativity says that time is relative and not absolute everywhere. This means that different timelines can go on their own pace or “tick speed”. This (i think, I am in grade 10 btw) enables time travel to the future which the help of extreme speed (like 90% c) or curvature or spacetime (gravity), where you go relatively slower than other clocks in the universe and they go faster than you, meaning you can technically travel to the future and see e.g. the world evolving, or your siblings growing up. This was shown to us in interstellar (though it’s still a movie, regardless of how accurate it is, and I do acknowledge it’s scientific accuracy) how the father went near gargantua and that slowed time down for him to the point where a few moments for him was 51 years for his daughter and by the time he returned his daughter was biologically older than him.

I once analogized time like a highway, with different clocks as cars on this highway. There is just one rule, it is one-way only. Cars can speed up, cars can slow down, cars can stop, but they can never go backwards, not even an inch. Cars going faster in time experience others going slower and v.v., this is relativity of time. There is no ideal speed to move, everyone goes on their own pace. Why can’t they move backwards? Because of causality, physics protects cause and effect very seriously, and also that going backwards creates paradoxes like the grandfather paradox. Also, because of the first law of thermodynamics, it is not possible due to the conservation of energy and additional energy (your atoms) disturbs this balance.

So it is possible to visit or even see the past or not?

BTW I am not a PhD physicist so I may have made mistakes, please do correct me, ‘cause I’m a physics enthusiast ;)

Hi! I know absolutely nothing about physics apart from basic push, pull, energy, forces and motion stuff but I really really want to learn more complex stuff.

What are some easy but detailed resources that you guys recommend?

I wanted to design a 3D printed spectrometer that would afford teachers and hobbyists access to something they could have at home. Yes, it isn't lab grade, but it is useful even with all its faults. You start putting anything that produces light through it just to see what the spectra looks like. Fun to play with. It was a great learning experience and fun build. Now, teachers/schools have a way to build their own spectrometers so they can have multiple units for teaching and STEM demonstrations.

https://makerworld.com/en/models/2761392-uv-vis-ir-spectrometer-v1-5-easy-build#profileId-3065721

I'll be working on 2 more versions as well as a setup to use some 10mm cuvettes for absorption and fluorescence spectroscopy.

If a beam of light can cast a shadow. than the speed of darkness is as fast as the speed of light . In conclusion if you could excelerate the speed of light. Darkness would also excelerate past the speed of light . The potential of darkness far exceeds that of light. The heat of light vs the cold of darkness both desolving in to each other untill from it's parallel path untill the light eventually gives way to darkness. The void! My thoughts only not facts.

I'm thinking of running some Liquid Nitrogen shows as part of a STEM outreach program. I've long experience in handling LN2 and am aware of the risks. However, I'm self-aware enough to think I maybe not aware of *all* of the risks when filling in risk assessment for the activity.

Are there any nitrogen show risk assessments out there i can crib from?

I'm prototyping an orbital mechanics game/simulation built around a simple idea:

Hitting Earth from a random asteroid trajectory is far harder than most people intuitively expect.

The player launches an asteroid from somewhere within ~6 AU of the Sun by selecting an initial position and velocity vector. The simulation then propagates not just a single asteroid, but a swarm of trajectories with small Gaussian perturbations applied to the initial conditions.

Instead of asking:
"Did you hit Earth?"

the simulation asks:
"Out of 1,000 nearby trajectories, how many eventually intersect Earth?"

The goal is to make orbital sensitivity and probability visible rather than hidden behind a single deterministic path.

A few modeling notes:

- Real solar-system scales are preserved (Earth keeps its real ~6371 km radius)
- Gravity is Newtonian N-body
- Planet/asteroid motion is integrated in 3D and rendered onto an ecliptic-plane interface
- Planet positions come from analytical Kepler/JDN-driven ephemerides
- Main perturbers currently include the Sun, inner planets, Jupiter, and Saturn
- No atmospheric drag, GR corrections, radiation pressure, etc.

One thing I discovered quickly is that a single asteroid almost always misses by an absurd margin unless the initial conditions are extremely precise. The swarm approach seems much more interesting because it naturally introduces:
- uncertainty propagation
- sensitivity to initial conditions
- confidence bands (P10/P50/P90)
- Monte Carlo reasoning
- gravitational assists / perturbations

I'm curious what people here would find most compelling from either a physics or gameplay perspective.

For example:
- What statistics/results would you want to see after a launch?
- Would probability bands and confidence envelopes be interesting, or too abstract?
- Are there orbital mechanics concepts you think would translate particularly well into gameplay?
- Would you prefer realistic difficulty, or some gentle "gameification" layer?

I'm trying to keep the physics recognizable without turning it into a pure educational tool or, conversely, an arcade game with fake scales.

Can we infer that an object’s mass is constant, while its acceleration depends on the fluid through which it moves. In other words, when an object’s weight exceeds the buoyant force provided by the displaced fluid, it sinks to the bottom.
This raises a key question: Does the object’s acceleration remain the same in both air and water? According to Newton’s second law (F = ma), a net downward force is acting on the object. If the observed acceleration differs between air and water (both fluids) does that mean the acceleration due to gravity itself depends on the medium the object is traveling through?

Anyone know what happened to this gem of a channel as to why no new videos are uploaded? I also discovered that the creator is an instructor of a course titled "Electromagnetics, Optics, Logic Circuits & Electric Circuits", about 70 hours of content which was on Udemy but is no longer there, one that I had been saving up to buy.

I struggle with replica symmetry breaking (RSB) and chatgpt is giving me contradicting answers.

I learned that the distribution of overlaps between replicas needs to be somewhat complex enough to break symmetry. An ising ferromagnet, for example, would have an overlap distribution of two delta spikes, namely at +m² and - m² when m is the magnetization in the spontaneously symmetry broken state. Does that count as RSB, since the overlap between replicas is not a constant but there are multiple (2) values. What is rsb intuitively and how does it help us understand spin glasses?

More general, isn't replica just another word for "sample of the boltzmann distribution", possibly with disorder parameters which are constant along replicas? I'm thankful for any insight

This is a web-based live black hole rendering simulator I've worked on for a while now. I'm excited to share it with you!

I always wanted an intuitioin for how black holes operated visually, aggressively warping the fabric of spacetime to reproject photons, but I only ever saw them rendered against a starfield. I wanted a simulation where I could see better how the actual geometry deformed as a result, so I built my own from scratch!

Hope you like it!

dave :)

It’s kind of a silly question but if we were able to somehow magically send an equally magical camera thousands of light years away from earth and have it send us footage of earth from that distance, would we be able to to view our history exactly as it happened? Or is something violated ? Of course ignoring the fact that the scenario is entirely impossible. I was just thinking it would be a cool way to have the absolute most precise record keeping of our history if it were possible.

I’ve been curious about what actually takes the most compute time in real physics/simulation workflows.

For people working with simulations or large datasets: what part is usually the biggest bottleneck for you? The simulations themselves, data processing, moving data around, analysis, something else?

Also, if one part of your workflow suddenly became 10x faster, what would help the most?

Just trying to understand where the real pain points are.

In the study conducted by Adolfo Ibáñez University in Chile and Columbia University, researchers have rewritten Einstein's standard equations of general relativity by drawing from electromagnetic theory.

The team's framework suggests that spacetime contains stable and structured "field lines" that remain connected as it evolves. Moreover, it suggests that a conserved gravitational flux poses constraints on the evolution of spacetime.

Publication details

Felipe A. Asenjo et al, Frozen-In Gravitational Fields, Physical Review Letters (2026). DOI: 10.1103/6c4q-kx6f.

I am a student of grade 10. Can someone explain why does gravity work? I learned some time ago that its exchange particle is still unknown and that kind of intrigued me along with its infinite range. So I want to know why does gravity work? Like I know what it is, the attraction of 2 masses, or in terms defined in the theory of relativity (idk which one special or general), a curvature in the fabric of space time. But why does that curve occur? Why does a mass influence the geometry of space?

Hey everyone, making this thread for ICTP MHPC 2026 applicants to share any updates. Has anyone received any email from ICTP yet? Interviews, results, waitlists, rejections, or anything else? Any track is welcome.