Julian Barbour is a theoretical physicist and emeritus visiting professor of physics at the University of Oxford. He is well known for proposing that time does not actually exist. For decades, he has worked outside an academic environment. He financially supported himself for many years by translating Russian. Professor Barbour is author of the following books: The Discovery of Dynamics, The End of Time and The Janus Point.

In the video, we go over:
- Topos theory, set theory and Zermelo's beef with Boltzmann
- Algebraic varieties and monads in category theory
- Why physicists are wrong about the 2nd law of thermodynamics (because the universe is not a closed system)
- The real goal of the universe is complexity and variation, not entropy
- Hawking and Penrose's outrageous arguments
- Why we don't need wavefunctions, photons, bosons or gauge fields
- Why there is no quantum gravity
- Von Neumann's hilarious advice to Claude Shannon
- The intrinsic derivative
- Combining art and science

If we extrapolate the standard Hawking evaporation formula to a black hole with the mass of a proton, we get a lifetime far below the Planck time. However, this extrapolation is probably invalid because quantum-gravity effects should become important long before we reach such a regime.

Could this approach be useful, or would it make more sense to modify the Hawking temperature or emission spectrum instead?

Is it over for the MWI? Were there any objections made against their points?

https://www.youtube.com/shorts/YtwylcUMghQ

Quantum physics has a screw with no moving parts. A particle sits in a chain of traps. Slowly change how deep the traps are and how strongly they are coupled, then bring every setting back:

the Hamiltonian is exactly the same as before, yet the particle has moved on by one cell. As long as the cycle is slow and the energy gap stays open, the step does not depend on the exact shape of the cycle, only on how it winds around the one point where the gap closes. That whole number is a topological invariant, the Chern number: go around once and the particle moves one cell, go the other way and it moves back, miss the point and it goes nowhere.

This is a Thouless pump, and physicists have built it from light, with ultracold atoms held in overlapping laser patterns.

Hi there, I am an animation student who is deeply interested in physics on the side. Obviously I am still learning so my knowledge is limited, and I am also not from the field.

I wanted to bridge the gap between art and physics and be able to communicate it effectively, while making sure it’s accurate.

I’m trying to make tests on visualising quantum fluctuation but I am struggling, could anyone help me understand this area a bit more so I know how to approach it visually?

A while back, I did some research into what researchers and students in quantum tech actually need, including chatting with people working and studying in the field, some of whom were part of the IBM Global Quantum Qiskit Summer School 2026.

One thing that kept coming up was how hard it can be to keep track of who claimed what, where the evidence actually lives, and how different claims stack up against each other. There’s a heck of a lot going on in this space, and keeping tabs on it all is a job in itself.

So I decided to build something to help me make sense of it all.

Informaq Observer: https://informaq.observer

It's an interactive hypergraph mapping the quantum computing and technology landscape, linking claims to the papers they came from, along with the vendors, machines, algorithms, benchmarks and organisations involved. You can drill into a claim and follow it right back to the specific passage in the source.

A few things you can do with it:

• Look up a vendor, machine or algorithm and see what's been claimed about it.
• Compare claims and dig into the evidence behind them.
• Follow connections between papers, technologies and organisations.
• Find claims that are contested or where sources disagree.
• Travel back through time and see how the landscape has changed.

I've spent the last three months throwing a frankly ridiculous amount of research at LLMs to build up the graph. It's currently sitting at:

• 125,606 papers
• 47,832 claims
• 7,046 organisations
• 71 machines
• 457 contested claims

It's still very much a beta, so there'll be rough edges and things I've missed. AI-proposed claims go through review, and automatically approved ones are labelled as such. If you spot something dodgy, have ideas for making it more useful, or just want to have a poke around, I'd genuinely love to hear what you reckon.

This started as a tool to help me navigate the quantum computing rabbit hole, but hopefully it'll be useful to others too.

Keen to hear your thoughts!

https://informaq.observer

Hi everyone! 👋

I’m passionate about quantum physics and software development, and I’ve been consuming content on these topics for quite some time.

This curiosity led me to create a personal project: Genesis, a simulator that calculates atomic and subatomic physics in real-time on PC.

you can find it here: https://genesis.gemmi-e.com

github: https://github.com/Lightminedust/genesis-releases

Attempted to create short explainer

i am looking forward to start quantum mechanics from the very beginning. where shud I study from? i found richard feynman's book so interesting! what are your ideas over it?

Algorithm, hardware, number of correct digits, number of CPU/GPU threads, and wall-clock time.

I ask because there is no good modern figure on how fast these run and so I was hoping somebody here has a program on their computer to calculate it even if it's only for a few to a dozen digits. I am curious as to how fast it is now on modern hardware.

If this is the wrong sub point me to the right one please, thanks!

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I'm trying to understand the exact boundary between retrocausal interpretations of quantum mechanics and actual backward signaling.

Consider the simplest setup:

- At time T1, an observer records a local result R.

- Later, at time T2, an experimenter freely chooses a setting S, either 0 or 1.

- The observer at T1 has access only to R. They receive no later measurement outcome, post-selection information, or classical communication from T2.

For genuine backward signaling, the statistics available at T1 would have to depend on the later choice.

In other words:

P(R given S=0) would have to differ from P(R given S=1).

Equivalently, there would need to be nonzero mutual information between the later choice S and the earlier record R.

My understanding is that standard quantum mechanics prevents this through the no-signaling structure: an unconditioned operation performed on the other subsystem cannot change the earlier/local reduced state.

That's why delayed-choice experiments, entanglement swapping, weak measurements, post-selection and time-symmetric interpretations can produce unusual correlations without allowing the earlier observer to determine which later setting was chosen.

My question is:

Are there any mathematically consistent post-quantum, generalized probabilistic, retrocausal, or modified-causal frameworks in which a freely selected future setting can alter an earlier observable marginal, without conditioning on a later outcome?

If not, is there a theorem more general than the standard quantum no-signaling theorem that rules out this entire class of models?

I'm particularly interested in which assumptions would have to be relaxed for such an effect to become possible.

I'm not claiming backward signaling exists. I'm trying to determine whether the operational possibility is ruled out in general, or only within particular physical frameworks.

Talking about physics with a broad public doesn't always need to rely on high-technology equipment. Sometimes, an adapted jigsaw and grill skewers from the supermarket will go a long way to help scientists illustrate some aspects of their research.

It all started with a group meeting where Dr Duilio De Santis brought along a simple prop to visualise the problem on which he worked at the time: everyone wanted to try out the homemade chain of pendulums, overjoyed at the opportunity to swap data plots and visualisations for something that could be held in their hands, shaken and twisted ... find the linkLow-tech props for complex physics to read more

u/ethzurich #quantum #physics

I’m new to quantum physics so apologies if this post seems obvious or if I’ve just got it completely wrong. Also, I posted a version of this on AskPhysics, but it was taken down because it was deemed to be philosophy, not physics. Hoping it is okay to post here.

In GR, the theory of a block universe, while philosophical, seems fairly central to GR theory. The absence of a universal now and the fact that one person can experience now in one coordinate in the dimension of time while another person can experience the same now in a different future coordinate of time imposes on GR that each object in the universe not only has its own now but its own worldline of fixed, predetermined coordinates, just like the coordinates in three dimensional space. Our past, present and future all co-exist. In fact, the entire past, present and future of the universe is fixed and predetermined and unchangeable.
But the mainstream view in quantum theory seems to entirety contradict this block view of time. The microscopic quantum world proposes a non-deterministic probability worldline whose past, present and future consists of a wave function of probabilities that when measured collapses into a single particle. The wave function itself is spread across vast areas of space and its instantaneous collapse in all the space it occupies only makes sense if there exists a universal now. Changing the state of the universe everywhere at once implies a preferred now. Since particles are the foundation of all objects in the universe and the determination of a particle’s position is probabilistic, the worldline’s of all objects in the universe have to be probabilistic, according to this view of quantum theory. You can’t have a predetermined fixed block of time co-existing with a universe of probability determined events. If events are already determine, they aren’t random even if the result remains hidden from us.

Again, I’m aware that I’m describing (badly?) what I believe to be the Copenhagen view of quantum physics and that there is also the many worlds view which rejects the wave function collapse altogether.

I am in 10th grade and am EXTREMLY FASCINATED by quantum physics but I don't under stand the big words and math equations. So I came to the place where I think smaller words can be used XD

My understanding of quantum physics is that nothing is predictable and things can pop in and out of reality. BUT HOW? what is reality and how is time travel possible? what do we know? how can I learn more and still understand? I'm just a nerd trying to understand more about the fun science HELP ME PLEASE!

We discussed:

- The power of the Leech lattice to control all lower dimensions
- Peter Scholze, Grothendieck and Ramanujan's styles
- Category theory and contrahomology
- How modular forms show up everywhere
- The countless coincidences in string theory
- Unimodular lattices and Lorentzian lattices
- How to construct the Langlands dual group
- Vertex algebras, infinite-dimensional algebras and Kac-Moody algebras
- Elliptic curves
- Automorphic forms and hyperbolic reflection groups
- Analytic number theory vs algebraic number theory
- The first construction of the Monster group
- "The Book" of most beautiful proofs
- How to teach math
- Math as archaeology
- His current work
- Neutron stars, Terry Pratchett and more

Richard Borcherds is a British mathematician who made seminal contributions to lattices, modular forms, group theory, representation theory and infinite-dimensional algebras. He is well known for his proof of the monstrous moonshine conjecture using ideas from string theory, for which he was awarded the Fields Medal in 1998. He is currently Professor of Mathematics at UC Berkeley.

There seems to have been some recent progress in the last few years working on the Bohmian/relativity compatibility problem. Given that this is one of the major objections to Bohmian interpretations, im interested in the opinions of experts in the field as to the significance or insignificamce of these experiments. The last two are yet to be peer reviewed, but the first ones are.

2022 — Relativistic Bohmian trajectories of photons via weak measurements — Nature Communications
https://www.nature.com/articles/s41467-022-31608-6
2024 — Measurement-based Lorentz-covariant Bohmian trajectories of interacting photons — Physical Review A
https://journals.aps.org/pra/abstract/10.1103/PhysRevA.109.022229
2025 — Directly observing relativistic Bohmian mechanics — arXiv preprint
https://arxiv.org/abs/2509.11609
2026 — Observing relativistic trajectories of single photons — arXiv preprint
https://arxiv.org/abs/2608.26778

We say that a quantum particle’s state is described by a wavefunction, and that this wavefunction produces wave-like effects such as interference and diffraction.

But what is actually oscillating?

In a water wave, water moves. In sound, air pressure oscillates. In light, electric and magnetic fields oscillate.

So in a quantum matter wave, what exactly is the thing that “waves”? Is the wavefunction a real physical entity, or just a mathematical description of probabilities?

*** For the mods, I would appreciate your consideration with regard to this post. I do not think I am breaking any rules. I am not posting a hypothetical theory, nor is the main purpose of my post to give an interpretation. I am posting a truth about probability in the sphere of my profession and asking how/if it applies to Quantum theory. I also don't think this post fits in the other places suggested.

The book I am currently reading is Carlo Rovelli's The Equality of All Things, and he seems to state that the world is probabilistic, and part of the evidence he gives for this is how precisely their models predict reality. If I am incorrect in understanding this, or if this is a theory that is just uniquely his, please point that out; I will continue as if I understood him correctly and that most theories suggest the same thing. While I know little about quantum physics, I used to play and teach poker for a living, and so my questions are in line with what I've learned from those experiences. Poker is a game that can be mapped out quite precisely with probability; however, the fact that probability exists in the game of poker doesn't prove that the game is probabilistic; in fact, it's the opposite. For example, if I needed an ace of hearts to make a Royal Flush, and if there were 40 cards in the deck, I'd know that I'd have a 2.5% chance of getting the Royal. If I ran this out over a million simulations, this would work out almost perfectly. However, if I simply peeked at the top card, or had the dealer peek and signal me, I would know for sure whether I was making my Royal or not. I wouldn't need a crystal ball or magical ability either, just the willingness and skill to cheat (this has actually happened many times). In this sense, it is only my lack of information that makes the game appear probabilistic. The fact that I can model the game with probability with extreme precision only proves that I'm good at modeling from a place of ignorance. Yet many successful poker players don't understand this, and it's probably because probability works so well (it's also rather pointless to think about given their aims). My question is whether the same mistake is happening in Quantum physics. Is the predictive power of the equations the backbone for the theory that the world is probabilistic? If so, why isn't this a mistake in this case? Also, I assume (correct me if I'm wrong) there is an immense amount of unknown information; why is this not a concern when stating that the universe is ultimately (insert whatever word you prefer) probabilistic?

What papers, books, online courses, articles (preferably free to access) can teach me about Bohr's atomic or rather the wave-mechanical atomic model?

In the next to years I want to write my final seminar paper about the study and analysis of transit spectra.

In order to do that I want to build a deep and comprehensive understanding of the behaviour of electrons, atomic orbitals, the application of the Schrödinger equation, the different energy levels of electrons, how the come to be, absorption and emission of photons and so on so forth.

All of this goes waaaayy past what is taught in high school (I'm a sophomore). This puts me in a difficult spot, because I just don't possess the necessary prior knowledge to read the very deep scientific papers at the moment. I need literature, that explains the complex stuff in a way that I might understand, but does not simplify it. I'm not scared of the complexity of those topics - I desperately want to learn. Every source I find keeps telling me the same superficial infos :(((
Because of this I ask you for the best sources to help me learn this stuff :)
I'd be very thankful for any recommendations.

Do any theories speculate that for example eg our point of reference is that it is 2026, that is the time we exist in - for us there’s only forward.

But do theories exist that somewhere, the revolution is still ongoing eg it’s 1776 on another plane; on another it’s the height of the court of the Sun King in the 1680s still, and so on?

I’m interested in quantum computing and the foundations of quantum mechanics. Since Bell’s theorem and experimental results challenge local realism, I’m curious whether there is still any serious research exploring alternatives that preserve some aspects of Einstein’s ideas, such as locality, realism, or deterministic underlying models.

Are there any active researchers, theories, or research areas working on this today? I’d also appreciate recommendations for papers or topics to study.

I’m currently a sophomore high school. I am advanced for my age. I’m currently taking AP pre-calculus and I plan on taking physics next year, I saw a video on Photos as waves double slick experiment and it really peaked my interest. It put me down a rabbit hole and I find quantum mechanics very interesting and I would like to learn more. Is there any books you guys would recommend me as a beginner in the field? Or any videos, etc..

can anyone help me with this hw problem? i's used the rearranged Rydberg Equation a couple different ways, and some hail marry other equations to try to get the answer buy I cant figure it out.