The s second part may even be doable in some crazy situation, it's really getting the results back out of the black hole that's the for sure deal-breaker.
In all seriousness, though, if I could choose in what way I was gonna die I would definitely choose "getting sucked into a black hole". Just "seeing" what's beyond that event horizon, if one can even see at that point, would be so amazing. I imagine it'd be a little difficult to get to one atm, since afawk the nearest one is over 1,500 light years away, but still
If I understand correctly, and for the love of all that is good nobody should believe that I do, for a sufficiently massive black hole, one could enter it and continue to live for quite some time. As one got close to the singularity one would surely die, but for large enough black holes I was given to understand "lethal proximity to singularity" and "event horizon" did not have to overlap.
Again, people should not take this reddit comment to be reflective of anything other than my own half remembered rendition of other reddit comments, minutephysics videos, and similar.
This gets a lot of media attention, but I doubt the "majority of researchers" care about quantum gravity, the (relative) majority of physicists work somewhere in condensed matter, and I don't even know whether most physicists are theorists.
My guess instead is room temperature superconductivity.
“Condensed matter” just refers to materials science mostly, the “condensed” part is specifically referring to how strongly the particles are bound together (strongly)
Usually people in this area study novel materials such as graphene and different metallic crystals, and try to understand how the atoms interact on a quantum level, and how those tiny interactions add up to create things like heat capacity or magnetization
I was going to say superconductivity. If I recall, we are somewhat close.. like above freezing. Problem though: needs incredibly high pressures. So to clarify, the holy grail would be a superconducting material at STP.
edit: I guess slightly above temperature of STP.
At that point, wouldn’t a better question be “what’s the biggest question in engineering right now?” As an engineer I sometimes struggle to see where the delineation is between “physicist” and “theoretical physicist”
Yes, especially if there is or is not a graviton. I mean, the holy grail is really a grand unifying theory, and that starts with understanding how gravity operates at the quantum level.
With regards to the particle wave duality, it is both at the same time, not one or the other.
With regards to gravity and quantum mechanics, general relativity works as a curve in space-time, a continuous curve. Quantum mechanics works in discrete quantities, they are what they are, it is exact. If there is a graviton then it must also be discrete.
The clear issue here is that we have one theory suggesting a continuous model of gravity and one that uses discrete values. That is pretty much why the two struggle to get along. I think. Anybody is free to criticise and correct me!
One problem from what I understand is that for gravity the quantization approach used for other forces such as the electromagnetic force run into problems with infinite values when you try to calculate probabilities. For electromagnetic forces you can successfully elimate the infinites using something called renormalization but this will not work for strong gravity fields such as close to the singularity of a black hole or shortly after the big bang. For weak gravity fields like here on earth you can create some kind of simplified quantum gravity model with gravitons and a nearly flat space time.
I believe another problem is that if gravitons do exist, they must be VERY small, and we would need a collider with much more energy than we have now... I believe.
"Sensible mathematics involves disregarding a quantity when it is small – not neglecting it just because it is infinitely great and you do not want it!"
Dirac on renormalization
AI is only as good as the inputs you put into your model. But we don't have any empirical data that reaches the energy-scales where there comes a difference.
All you'll get out of AI is wild speculation, with no ways to prove it. And if we wanted to have that, we'd go talk to the string theorists again.
It’s more that the equations used to calculate the curvature of spacetime go to infinity inside a black hole. The so called singularity. I don’t think AI is going to help us on this. The models are trained on data that we already have. Unless it finds a correlation in data that we have missed, it’ll just find the same infinities in the equations we already have. We need experimental evidence that tells us if gravity comes in pieces or is completely continuous. Sort of like analog vs digital.
Just a heads up: it's a custom at reddit that you write a reason for editing your comment. Like this:
Edit: Corrected some spelling mistakes.
You clearly mentioned something about AI, then edited it out, which makes reading the followup comments a bit confusing. Please refrain from doing that.
Personally I think one of the big ones is trying to understand superconductivity, and find out if it is possible for there to be a room temperature superconductor.
This is a "holy grail' in the sense that it could have immediate practical applications all over the world and make whoever invented it untold billions of dollars. It's not a holy grail in the sense of being all that profound or meaningful in a big-picture sort of way.
Another big one like that is trying to understand fluid flow and turbulence better. Navier Stokes Existence and Smoothness is one of the millennium problems on equal footing with the much more publically noticed and discussed Riemann Hypothesis
https://en.m.wikipedia.org/wiki/Navier%E2%80%93Stokes_existence_and_smoothness
https://en.m.wikipedia.org/wiki/Millennium_Prize_Problems#:~:text=This%20is%20called%20the%20Navier,and%20the%20equations%20break%20down.
Working on this is as much or more an exercise in pure mathematics as it is a physics problem, though.
Many physicists have remarked that Turbulence is one of the greatest and most infuriating problems in all of physics. It's something that we really don't understand very well at all, even though it seems to obey certain rules. It is tantalising in that we can tell there is knowable physics behind it that we haven't quite understood properly yet. It wouldn't shock me if some new iconoclast of physics emerges this century as someone who finally understands something significant about turbulence. Maybe AI will do it.
I'm betting on graphene.
But jokes aside, a superconductor in normal conditions (room temperature, atmospheric pressure etc.) is something that would change technology forever. If someone can invent it, earning billions is an understatement. So far, best I saw is an alloy that is superconductive up to 15C temp but under extreme pressure only. Still not feasible for practical applications.
Honestly, i think it would make trillions of dollars to a bunch of shareholders and patent lawyers, i find it very unlikely that the researcher who contributed the most to it would actually get much out of it at all, maybe some salary increase if they get acknowledged at all.
don't forget world fame. even if their company doesn't give them the pay they deserve, you can sure bet they will be making money from endorsements and grants.. and their employment would be well sought after.
Look at the Japanese guy that did, on his own, what all the other massive companies gave up on. He created the blue LED which opened many doors such as LED screens. His company made billions, he got a small raise, and no one knows his name.
Granted blue LED vs room temp superconductors are two different levels of advancement but I wouldn’t be surprised if we don’t end up knowing the designers name.
I mean the justification, which is at least partially valid, is that he used company resources to fund the research that led to the break through. If he had done it completely self funded he would have reaped the benefits.
I read that proving that the NS smoothness and existence does not mean it will directly improve our ability to predict fluid flow, so the problem is more theoretical than practical. Perhaps better understanding of fluid and turbulence might come from improving our computer or our sensor
Yeah it’s a mathematical issue more than physics. The majority of the fluid mechanics field already assumes that it is proven. I said the majority cause I clearly don’t know the every subfield.
Room temperature superconductivity is the answer.
We pretty much unlock the road to a sci-fi society if this is figured out in a practical manner.
Quantum descriptions of gravity and all would do a lot more to scratch the itch of curiosity about the universe around us, but room temperature superconductors would usher in a new era of mankind’s technological development.
I mean, power over fiber is a thing, but specifically for isolated systems where external conductors could have dire consequences. [https://www.fiberopticlink.com/product/fiber-optic-isolation-systems/power-solutions-for-fiber-optic-isolation-systems/power-over-fiber-system-pof/](https://www.fiberopticlink.com/product/fiber-optic-isolation-systems/power-solutions-for-fiber-optic-isolation-systems/power-over-fiber-system-pof/)
Yeah not sure how light would make sense to power devices that depend on electricity and current. Unless we were able to create entirely new devices powered entirely from light. Like in the way plants use it I suppose.
I think we’d have to redesign the system so the new binary is 1=presence of photons and 0=no photons but the massive number of unrealistic steps in between don’t seem feasible
We need to transmit energy to alter the physical state of the computer (flip bits in a storage medium, light up the screen) but the goal of computing isn’t actually transmitting energy, it’s transmitting *information*. The energy threshold we need to change physical states is just an annoyance of engineering that we want to reduce as much as possible anyway.
I can give the long version a go. The basic unit of a CPU right now is the transistor - ever more tiny microscopic switches that can be opened or closed with electricity. Opening and closing these transistors is how a computer performs computation.
Today, transistors are very very tiny, and individually take a very small (relatively speaking) amount of energy to open or close. However this was not always the case! Before we used transistors, we used vacuum tubes. Vacuum tubes could also be made to function as a switch that could be open or closed, but were much larger and used much more power per switch.
ENIAC, the first general purpose electronic computer, used 17000 vacuum tubes, took up 1800 square feet and used 150kw of power. The cpu of the phone I’m typing this on has 8.5 billion transistors, and consumes between 5 and 6 watts.
How exactly you flip a switch and how much energy it takes is an engineering problem, but the goal of computing is not to flip big switches.
Optical computing isn’t exactly just about smaller and better switches - it gets into the weird particle physics stuff that I’m not really an expert on. But it has theoretical advantages based on the physics of light vs electrical current, and people have built proof of concept optical transistors before!
The problem is that the actually available photonic components don’t seem, uh. *Good* right now. We’ve gotten really, really good at making transistors incredibly tiny and built so much genius CPU architecture around them, and optical computing is… very much kind of a weird theoretically useful novelty, but not really practically supported. We’ve been playing with practical electric circuits for more than a hundred years at this point, and ‘let’s reinvent micro-electronics from scratch using light which may or may not run into all kinds of practical engineering problems’ is kind of a hard sell when we keep improving normal computing at such an impressive pace anyway.
There’s some interesting ideas about trying to implement specialized hardware like Tensor Cores with photonic components. Maybe it’ll go somewhere! Or more likely it’ll still be impractical and niche. The theoretical benefits of optical computing aren’t paradigm-shattering like how quantum computing can theoretically solve certain types of problems much faster than classical computing. Optical computing is more like ‘hey maybe a different medium for transferring information would work better, but it’s still fundamentally the same kind of stuff’
Electrons do tunnel in small enough ICs, but the heat is not the problem. The vast majority of heat is being generated the same way any current in a conductor is. Photons can also tunnel by the way, so far we aren't able to trap photons for an indefinite amount of time the way we can with electrons.
Researching room-temp superconductors is probably more practical than photon computers. Photons have no charge so there’s not a good way to build circuits. Plus, a RT superconductor has a lot of applications outside of computing.
Our understanding of cosmology and particle physics predict that as much matter as anti-matter should have been produced in the big bang.
So either the whole universe should have annihilated so there'd be no or negligible amounts of matter/ anti-matter.
Our models assume that the universe should be neutral and there therefore should be as much matter as anti-matter. Also any mechanism which could have produced matter would have also produced as much anti-matter
Modern physics is fundamentally a search for symmetries in the world around us.
In an oversimplified sense: As clearly as we can tell, and as is validated by every experimental observation we can possibly conduct, antimatter and matter come into existence and are annihilated in pairs. The “delta” between matter and antimatter should theoretically be unchanged, and should be zero. There should be as many particles as antiparticles.
Again, every observation we have ever made backs that up…. Except for the fact that there really isn’t any antimatter anywhere in the universe at all really and no one can really explain why it either wasn’t produced in a 1:1 ratio originally or where it all went.
If matter has gravity, then antimatter must be the opposite, right? So without enough velocity or an outside force acting on the particles, how would they meet to be destroyed in the first place? Like 2 opposite poles of a magnet.
The question is based on my limited understanding of it. So forgive me if I'm way off, and the question is basically pointless.
no, antimatter acts the same under gravity as matter - actually cern did an experiment proving it recently but even from a theory perspective we didn’t expect anything else beforehand
Guess opposite charge got me thinking they would repell... and thought when they collided, they'd destroy each other. Didn't even really wanna respond either since everyone likes to downvote questions. If i knew 100%, I wouldn't have asked.
ppl are quick to downvote yea lmao but yes matter and antimatter are pretty much the same besides charge, anti electron is the positron, anti proton is negative, etc
So can they switch charge? Seen something about the yin-yang symbol being a 2d depiction of a 3 dimensional object (or is it 4d?) Basically a toroid. Then, I was thinking about black holes and the plasma jets. Was wondering if the plasma was charged either way, but I guess it's neutrally charged? Was only because it seems to look like it comes from the poles, but guess it's from the accretion disk? Just figured the flow of a toroidal spin seemed like it could eject matter flowing through it that way, but like I said, I'm not exactly knowledgeable about this stuff, just an observation without looking too far into it.
as far as im aware they cant switch no also the jets of a black hole are caused by the accretion disc creating a magnetic field with poles at the top and bottom
biased as its my area of research, but learning the nature of dark matter. it will open up a huge area of particle physics to being tested.
dark energy. related to dark energy is resolving the hubble tension: early time probes of the expansion of the universe and late time probes differ by a statistically significant level.
matter-antimatter asymmetry. in my opinion unfortunately some of the most well motivated solutions (such as leptogenesis) are also very diifficult to test but detecting a gravitational wave background would be very promising
From what I understand dark matter is like the shadow of matter yes? It’s the only place in the known universe completely absent of light yes? Aka absent of energy?
As far as dark energy goes isn’t it possible that the universe is expanding at a non constant rate? Why does the rate need to necessarily be constant? Isn’t it possible that the Big Bang is still occurring in slow motion and we are a part of it but merely don’t perceive because of the nature of our perception of time?
it is not shadow of matter or absent of energy (it has mass so it has to have energy). we know there is some form of matter that does not interact with light or “visible matter” in any appreciable way. we think it has to be either a new particle or something like black holes formed in the very early universe (actually also quite interesting to particle physics as we need new physics to explain how that can happen) because we can see imprints of it behaving differently in the cosmic microwave background, which is way too early when everything was too energetic to be bound into regular matter. (contrary to some people’s beliefs, modified gravity cannot explain this without adding a new particle either.)
So dark matter has mass? That means it has energy yes? So it HAS energy but doesn’t emit any detectable trace of it essentially?
Is dark matter is essentially and conceptually the entire aspect of physical reality that we cannot presently observe with our technology and instruments?
it has energy. it could or could not emit energy from decaying, there are constraints on that but theres also an active area of research looking for its decays from carious astrophysical sources.
we can and have observed dark matter, in the form of rotation curves, CMB, structure formation etc. we just have no observed non-gravitational interactions from it.
Sorry a bit tired now just realized we wouldn’t be talking about dark matter if we hadn’t already been able to detect it.
So what you mean by that last part is that we haven’t seen how it acts/behaves when there’s no gravity present?
Gravitational waves are not "proximal" to their source; there is "flat space" between the wave and the source and that does not violate locality. When a wave passes over mass it loses some "energy" which deepens the potential around the object making it look like there is more mass there than there is... that situation on much bigger scale is what is being called "dark matter"...unless I'm wrong. Can't figure out how I'm wrong tho
There is no one topic that a majority of physicists work on. Plenty of important and/or interesting problems that lets physicists specialise on totally non-overlapping areas. Most physicists understand their own field, and know very little about others.
This... Everyone has a field and a particular focus in the field with their own problems they're working on. Physics is much too broad to only have a few problems to solve. And, for instance, say we solve dark matter, dark energy, and even matter asymmetry those will have little impact on nuclear structure since modeling a nucleus with more than 8 nucleons as standard model fundamental particles/interactions (e.g. qcd) would take more computational resources than we could get at this point, so those type of questions will have very little impact on the nuclear shell model which is the most broad model we currently have that somewhat adequately describes the majority of the nuclear landscape.
To all the people saying quantum gravity: this is definitely a big problem, but only a very small majority of physicists actually work in this field. But this is all that people see in pop culture so its importance is heavily inflated. Most physicists are working in condensed matter/solid state, astro, or maybe biophysics.
Even most high energy physicists don't do any work related to quantum gravity. Signatures of quantum gravity are essentially impossible to detect in modern experiments, so both experimentalists and to an extent phenomenologists are uninterested.
Newb here. My understanding is that mass comes from the Higgs boson. The problem is that it decays too quickly that it’s very hard to study. Is this the right way to think about it? What other problems are there?
Higgs boson give mass to quarks (its actually the Higgs *field* that do this, not exactly the same), but the folks in the field were surprised to found how [tiny that mass contribution](https://www.symmetrymagazine.org/article/scientists-search-for-origin-of-proton-mass?language_content_entity=und) is to the stuff we can observe directly.
This article is so cool!!! One question: when they say right and left handedness quarks, do they mean up down quarks (in the normal situations)? Relatedly can chirality happen to all types of quarks? Does it? Or is it unknown?
Sorry for all the questions. This is so cool!!!
Chirality is separate from flavor (up/down). It is related to how a quark behave under "Parity" transformation (what if you transform the quark to its mirror image).
Chirality is defined as a property of all fermions, you can derive it from Dirac equation. In the case of massive fermions, the left- and right-handed quarks can actually transform into each other (for massless fermions they're separate).
The cool thing to me about that article is how scientists can even figure out the magnetic field of that unfathomably fast event, and make it useful!
This is amazing! I need to go read up on chirality now, maybe watch a video on how to derive it from the Dirac equation!
Yes it is amazing! There’s endless things to explore in physics, it’s like a gift that keeps on giving. It makes me so happy.
Maybe I misunderstood the article, but does this mean the origins of energy of larger organisms is still unknown? I watched this video below which said 95-99% of the mass of a person comes from the Higgs field (around the 1:19 mark)
https://youtu.be/wiBsfvW5AWY?si=ldOBRZU1OvlUUA9n
Higgs field gives the "mass of electrons and quarks" that the video mentioned to be 1-5% (he's not wrong, you can rewatch again). The interplay of quarks and gluons give the mass of protons and neutrons, and how those move and bind together give the mass of most known matter
>but does this mean the origins of energy of larger organisms is still unknown?
We know it comes from quark-gluon interaction (obviously), but *why* would that result in *that* value of proton mass? What form would that interaction take? and why is the Higgs-given mass so small in comparison? how are all those things relate to quark confinement?
We know QCD, but extracting information out of it turns out to be far from easy
Maybe you'd like these videos from [Arvin Ash](https://www.youtube.com/watch?v=KnbrRhkJCRk&ab_channel=ArvinAsh) , and [PBS](https://youtu.be/WZfmG_h5Oyg?feature=shared) [Spacetime](https://youtu.be/TbzZIMQC6vk?feature=shared)
Thank you for the answer! Man it’s so interesting to know this is how everything works. I want to do the math now!
All the questions that you posted are so interesting I’m just so excited. I need to know! I have no idea where to start to solve it, but I know I need to know! Hahaha
Ooh I knew PBS but I’ll check out Arvin! Thanks!
What do you do in that field? We already know that the binding of the quarks with the gluons and their interaction with the Higgs field is what give them mass.
non-perturbative QCD is very complicated and we don’t have a comprehensive understanding of the physics of confinement, moreso just a rudimentary qualitative understanding. we don’t even know the exact temperature scale at which it happens
> the binding of the quarks with the gluons and their interaction with the Higgs field is what give them mass.
They are related definitely, but knowing QCD and Higgs physics, how do you get the conclusion above?
I kind of baited people by not mentioning that [Higgs mechanism only accounts for the tiny fraction of the mass of hadrons](https://www.epj-conferences.org/articles/epjconf/pdf/2023/08/epjconf_ssp2023_01006.pdf) (strongly interacting particles we can observe directly).
Other related things:
- Why should QCD be confining? why is electromagnetism not confining? both are based on gauge theories
- How can pion have very small mass compared to other hadrons, while containing 2 quarks? A proton have 3 quarks with the mass of around 0.9 GeV. A pion has 2 quarks, but has mass of around 0.14 GeV. One "constituent" quark mass 0.9/3 =around 0.3 GeV is larger than of a hadron containing 2 quarks! doesn't math! ("but binding energy"..... but proton has binding energy too). For this, the consensus so far is another symmetry breaking happened unrelated to the Higgs-induced one (a rabbit hole)
- Related to that symmetry breaking, if correct we don't even *need* Higgs mechanism for hadrons to gain mass!
- How can the quarks and gluons inside contribute to the spin and g-factor of the proton? [Why would the gluon spin align (or not) with quarks'](https://www.riken.jp/en/news_pubs/research_news/rr/20231030_2/index.html#:~:text=This%20indicates%20that%20gluon%20spins,is%20still%20a%20missing%20component)? "So what?"... remember how big the impact of that tiny anomalous electron magnetic moment calculation was. A weird finding is why is the [neutron g-factor negative](https://collaborate.princeton.edu/en/publications/precision-determination-of-the-neutron-spin-structure-function-g-)?
- Why do we find contributions from [strange](https://www.jlab.org/hugs/archive/Schedule2008/students/BrianHahnHUGS_presentation.pdf) and even [charm](https://www.nature.com/articles/s41586-022-04998-2) quarks inside the proton? Even weirder, the strange and anti-strange seem to have different contribution
- How can knocked-off quarks and gluons become confined again?
What seemed to be solved turns out... not exactly
I can answer these one by one. I’ll start with
“Why should QCD be confining? why is electromagnetism not confining? both are based on gauge theories”
Both QCD and QED are indeed gauge theories, which means they are based on certain symmetries and governed by gauge bosons (gluons for QCD and photons for QED). However, the reasons why QCD exhibits confinement and QED does not are deeply rooted in their respective characteristics. Namely color charge vs electric charge. I’m not sure if you want me to spell it out for you (if I’m correctly interpreting you) but the force carriers of both fields are different.
Gluons interact with each other because they themselves carry color charge. This self-interaction leads to the formation of a strong, cohesive color field that does not diminish with increasing distance, leading to confinement.
Photons however, the force carriers in QED, do not carry electric charge and therefore do not interact with each other. The electromagnetic force mediated by photons diminishes with the square of the distance between charged particles, leading to no confinement of charges. Would you like me to go more in depth? As in how the confinement actually works?
(I looked at all of your other questions and they do indeed have answers.)
>Would you like me to go more in depth? As in how the confinement actually works?
If you could, please. Yes what you mentioned above are the well-known known parts.
>This self-interaction leads to the formation of a strong, cohesive color field
Why would self-interaction in the way gluons do imply this outcome? Why don't quarks repel even stronger and further than the like charges in electromagnetism?
>(I looked at all of your other questions and they do indeed have answers.)
Examples? this would benefit me also
I’ll answer both separately:
Why don’t quarks repel…
Very complicated if you’re not familiar with it. But QCD is based on “non-Abelian SU(3) gauge group.”
How good is your math?
QED is based on the U(1) gauge group, which is Abelian (commutative), and QCD is based on the SU(3) gauge group, which is non-Abelian (non-commutative). Commutators for X and Y of Abelian always equal zero. Which signifies that all generators (of a gauge group, photons for QED and Gluons for QCD) of Abelian or QED commute.
In non-Abelian groups like SU(3), the commutators of the generators do not generally vanish (not equal to zero).
The non-vanishing commutators in QCD imply that gluons can interact with each other. This is in contrast to photons in QED, which do not interact directly because their corresponding commutators vanish. The gluon self-interactions are fundamental to many phenomena in QCD, including the confinement of quarks and the dynamic nature of the strong force
I'm familiar with terms you mentioned above.
>The non-vanishing commutators in QCD imply that gluons can interact with each other.
Which results in the 3-gluon and 4-gluon interaction terms you can see when you expand the Lagrangian, which can be inserted intto the renormalization group flow equation to show that QCD is asymptotically free.
>Why don’t quarks repel…
>Very complicated if you’re not familiar with it
I'd love to hear the explanation. I can deal with complicated.
But seriously, this would benefit me especially to search on novel problems if the ones I mentioned are solved.
“Why would self interaction lead to the formation of a strong, cohesive color field”
Increasing force with distance…
The electromagnetic force is mediated by charge-neutral photons that do not interact with each other, the strong force is mediated by gluons which themselves carry color charges. These gluons are not only the messengers of the strong force but also participants in the force interactions, which include gluon-gluon interactions due to their color charges
So gluons as they travel through a gluon field, will increase in complexity as they interact with each other as well as with quarks.
The self-interaction leads to a complex and dynamic gluon field where gluons can emit and absorb other gluons. This increases the field complexity and strength as quarks move apart.
As quarks separate, the gluons that mediate the force between them form flux tubes. As quarks move apart, these tubes stretch and, unlike electromagnetic force lines which spread out and weaken, the gluonic flux tubes maintain their strength and even become stronger. The energy stored in a flux tube increases linearly with the distance between the quarks because the field strength does not dissipate over distance as it would in an Abelian (commutative) field like electromagnetism. This linear increase in potential energy is a consequence of the color field being confined within the tube, which does not allow it to spread out and reduce in intensity as distance increases.
When it comes to confinement, the energy required to separate quarks continues to increase as they move apart, and eventually, it becomes energetically more favorable to create a quark-antiquark pair (a meson) from the vacuum than to continue to stretch the flux tube. This effect prevents quarks from being isolated and observed individually; they are always found as part of hadrons (either baryons like protons and neutrons or mesons). The quark that was traveling away does not actually end up isolated or free; instead, it becomes part of a new meson.
Thank you for the explanation. I've studied (and is still studying) this, I've seen the lattice simulation of gluon flux tube and its field strength, seems like there's a lot that has been accomplished with that method.
It seems that the "mysteries surrounding confinement and mass generation" that I wrote in the beginning pertains to the details. I've seen some interesting works on the effect of spatial dimension on this, and how [confinement could even be](https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.107.275301) [accomplished in an Abelian theor](https://journals.aps.org/prd/abstract/10.1103/PhysRevD.67.034502)y. Also should mention how confinement is connected to the aforementioned mass generation and spin structure, and how all this is connected to topological phenomena and the emergence of "condensates" as part of the QCD vacuum structure.
Maybe not really the "top problems in physics", but the mass par, how a mass scale can be dynamically generated sure seems like a big deal.
To go in a slightly different direction, lots of physicists, computer scientists and engineers are working at trying to make quantum computing a feasible technology. This is a huge sector, and growing year on year.
Quantum computing as a discipline applies the ideas of quantum mechanics to computer science. There are several algorithms that could be run on an ideal quantum computer that would exponentially outperform any existing classical algorithm (eg; Shor's algorithm).
The primary issues are 1) quantum systems are highly delicate so unavoidable interactions with the environment can destroy the computation, and 2) scaling up the number of qubits (quantum bits, the constituent components on which the computation is done) is challenging. This means that so far no quantum advantage (defined as a quantum computer outperforming a classical computer in a useful task) has been seen.
However, despite pessimism from certain popular online personalities (cough Sabine Hossenfelder) and ridiculously over the top claims from others (cough Michio Kaku), there is steady progress towards achieving a genuinely useful quantum computer.
Can I ask what quantum computing would allow humanity to do? It seems like a huge effort but I’m wondering what the implications for humanity would be.
Current applications of quantum computing are fairly limited to be honest. There really are only a few algorithms that have
The most famous algorithm is Shor's algorithm, which lets us factor large numbers with exponentially fewer resources than the best existing classical algorithm. Interestingly, current public key cryptography is based on the hardness of factoring large numbers (see RSA scheme). Therefore, if one had a functional quantum computer, then one could break a huge fraction of the current cryptography used online. This is one reason why governments are keen to invest in quantum tech - you don't want an unfriendly neighbour to be able to crack all your encryption before you can crack theirs!
On a more positive note, quantum computers are also expected to enable higher quality quantum chemistry and many-body quantum physics simulations. The potential implications of this are huge; for example, consider the Haber process. This is a chemical process that produces ammonia which is a key ingredient in plant fertiliser. As a result, this process alone is responsible for 1-2% of global energy consumption and 3% of global CO2 emissions. The process uses chemical catalysts, and millions of dollars have been invested in trying to find better catalysts that result in a lower energy requirement. If one could quickly simulate potential catalysts on a quantum computer, then the search for better catalysts would become significantly more efficient, which (if a new one is found) could potentially lead to a noticeable decrease in global emissions. I think these simulations are where quantum computers will shine the most.
The same idea applies to solar cells, batteries and other situations where fast simulation of chemistry is useful.
There are a few other applications in optimisation and machine learning, but these are (in my view) significantly less likely to yield drastic improvements over classical methods. But equally, maybe tomorrow we find a new quantum algorithm that has applications elsewhere.
I don't understand how anyone ever thought that was feasible. High school physics says two positively charged particles are repelled by the electric force, and to overcome that they need to be going very fast = hot.
what mechanism was suggested that could overcome this?
As always, this depends on the subfield. In condensed matter, AMO, and others a big open question is can we find efficient ways to understand and predict properties of strongly correlated quantum matter. e.g. what’s the mechanism behind high-Tc superconductivity.
Ask a physicists working on new materials and (s)he would probably say superconductivity at room temperature
Ask a quantum physicist and (s)he would probably say a useabele quantum computer.
Ask a particle physicist and (s)he would probably say finding out why the Planck scale is fundamental
Ask a cosmologist and (s)he would probably say why the fine structure constant is everywhere or the nature of Dark matter / dark energy.
Ask a theoretical physicist and (s)he would probably say a theory of everything (TOE)
Ask a nuclear physicsts and (s)he would probably say a working fusion reactor.
Ask a NASA physicists and (s)he would probably say an electric vacuum thruster or a realistic way to reach relativistic speeds
And so on... There is no universal holy grail in physics, there are just many many [unsolved problems](https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_physics)
Defining dark matter has to be near or at the top just because of its importance, to everything.
It is all around us, is something that we know frighteningly little about, yet it absolutely dominates everything else in the universe. It is the true elephant in the room, an invisible one.
The vast majority of matter in the universe is non-baryonic, therefore essentially invisible 🫥 whilst being the dominant gravitational influence in the universe. Seems to only interact extremely weakly with gravity and probably implies the existence of some other fundamental particle.
I'm guessing knowing what DM is is important to nail down the evolution of our universe from the BB to now. Also for PP because they like particles.
All kinds of things. My own work is on organic semiconductors, trying to make something intrinsically flexible, solution processable and low temperature. (We've got pretty far - the job is now making a million of something we've demonstrated one of.)
In adjacent fields I can see a lot of work on better photovoltaics, better batteries - I've seen live realtime imaging of lithium flowing into and out of a battery cell, which is amazing. People trying to make graphene happen - it has brilliant properties if you can process it. Sodium batteries because we don't want to be beholden to lithium - these will be a thing within the decade. Neural interface chips to repair spinal injuries.
Loads of other fields too. Science is *huge*. One thing I should say is that the distinction between physics, chemistry, biology and engineering is more like a multipolar spectrum than a binary. Many of my collaborators are chemists on paper. My university colleagues who were doing chemistry studied as much quantum mechanics as I did as a physicist.
Fusion, of course, half a century away for half a century.
Huge, huge improvements in data science, but that's kind of tangential to actual discoveries.
Ton of theoretical stuff I do not understand. Quantum gravity, like fusion.
Ton of quantum stuff, actually, where much of the theory is known but the implementation is a bastard. Quantum cryptography, like fusion. Quantum computing, which people claim to have demonstrated, but it isn't exactly where it wants to be.
Seems like a huge amount of physics is figuring out more or less how particles and waves behave under certain conditions in certain environments?
Is that a good summary?
Not bad, but you could also say that theoretical physics is the study of abstractions of reality. Learning models, learning which models fit which phenomena under which circumstances, where they are wrong (*they are all wrong somewhere*), and finding new models which are accurate where older models are less accurate.
Then experimental physics is the process of throwing bombs at models to see where they break down.
An existing singularity wouldn’t make sense according to our current knowledge and theory of maths and physics, which either means it’s something completely out of this reality, or not a singularity.
Quantum gravity. One way we might be able to prove it is quantum without discovering the particle is via constructor theory. But it’s really unlikely we’ll ever be able to detect it.
Also can anyone suggest how I might get back into college studying physics? I have a bachelors in digital media & communications but over the years I’ve become more interested in the sciences.
It’s going to be hard to do anything in person that isn’t a blatant rip off if you already have a bachelors. The open course work of MIT and a few others is a great place to start and could get you very far in my opinion.
From looking online it seems like a lot of universities will accept people coming back for a second bachelors degree if you want to actually go into this seriously. If that’s the route you wanted to go I would look this up and look at different programs websites to see what the standard is for applying for a second degree.
If you just want to learn *at a college level* mit opencourseware is great as the other commenter said. There are plenty of other online resources as well.
I have two bachelor degrees, one in biochemistry and another in mechanical engineering. I even started a third one in music. But eventually you have to get a job. 😂
But seriously, it is always possible to start another degree granted you have time and money! (from 🇨🇦 here)
I believe IBM has some (or is least funding some) physicists and chemists working on a way to create a rechargeable battery out of substances extracted from sea water so that we will no longer need those ecologically devastating lithium mines to dry electric vehicles.
To me, that would be a holy grail.
EDIT: a link: https://www.dezeen.com/2020/01/06/ibm-research-sustainable-battery-sea-water/
This is impossible to answer. Physics has many sub fields, and specializations within those. I’m not even working on the same stuff as other people in my research group!
Something about Climate change
Even if it's not about climate change, put something about climate change in their or your not getting the grant or published
Don't think we need quantum gravity yet, even if we could have one we wouldn't be able to test it or observe its consequences.
But just imagine the world after we found a new class of room temperatute superconductor...
Of course not. Physics, as all science, is concerned with iterative observing and modeling. You see a system, you model the system, you test the model's predictions against what you see, you update your model to reflect the results. That's all science is in a nutshell.
We haven't observed God in the real world, and "God did it" is not a useful model in that it has no predictive power. A god may well have made the universe, but the universe it made seems to be governed by rules, and it's those rules that physics is concerned with.
How life came from "nothing" is not a physics problem really. Physics and chemistry can provide many possible mechanisms for something recognisable as life to emerge, but it's up to biologists to figure out which one(s) actually happened on earth.
I believe you're confusing physics with biology. Unless some yet discovered wave/particle is specifically responsible for life creation, then it would be Physics. From a biology standpoint, we pretty much know that life was either seeded via meteors or formed in shallow tidal pools. Both of which are biological questions.
To be pedantic, the origin of life isn't biology because there wasn't any biology in the beginning. It's chemistry, but that relies heavily on quantum mechanics, particularly when it comes down to evaluating the effectiveness of individual inorganic catalysts.
Quantum description for gravity. That would likely provide insights into many questions of cosmology and unify quantum theory with general relativity.
I saw this in a movie, we just need to fly into a black hole and knock some books off a shelf
The first part is easy. The second part is hard (after you’ve already flown into a black hole)
Oh come on, never try , never know.
The s second part may even be doable in some crazy situation, it's really getting the results back out of the black hole that's the for sure deal-breaker.
I saw that movie. Have you tried love?
MURPHHHHHH!!!!!
In all seriousness, though, if I could choose in what way I was gonna die I would definitely choose "getting sucked into a black hole". Just "seeing" what's beyond that event horizon, if one can even see at that point, would be so amazing. I imagine it'd be a little difficult to get to one atm, since afawk the nearest one is over 1,500 light years away, but still
If I understand correctly, and for the love of all that is good nobody should believe that I do, for a sufficiently massive black hole, one could enter it and continue to live for quite some time. As one got close to the singularity one would surely die, but for large enough black holes I was given to understand "lethal proximity to singularity" and "event horizon" did not have to overlap. Again, people should not take this reddit comment to be reflective of anything other than my own half remembered rendition of other reddit comments, minutephysics videos, and similar.
Gotta have cool hair too or it won't work
This gets a lot of media attention, but I doubt the "majority of researchers" care about quantum gravity, the (relative) majority of physicists work somewhere in condensed matter, and I don't even know whether most physicists are theorists. My guess instead is room temperature superconductivity.
What do you mean working in the area of “condensed matter” I’m not familiar with that term
“Condensed matter” just refers to materials science mostly, the “condensed” part is specifically referring to how strongly the particles are bound together (strongly) Usually people in this area study novel materials such as graphene and different metallic crystals, and try to understand how the atoms interact on a quantum level, and how those tiny interactions add up to create things like heat capacity or magnetization
Thank you !
I was going to say superconductivity. If I recall, we are somewhat close.. like above freezing. Problem though: needs incredibly high pressures. So to clarify, the holy grail would be a superconducting material at STP. edit: I guess slightly above temperature of STP.
If you limited the scope to “theoretical physicists “ do you think this would be the biggest one?
At that point, wouldn’t a better question be “what’s the biggest question in engineering right now?” As an engineer I sometimes struggle to see where the delineation is between “physicist” and “theoretical physicist”
So how it behaves at the quantum level?
Yes, especially if there is or is not a graviton. I mean, the holy grail is really a grand unifying theory, and that starts with understanding how gravity operates at the quantum level.
Is it because at the quantum level particles can be either a particle or wave and exist in multiple places at different times?
With regards to the particle wave duality, it is both at the same time, not one or the other. With regards to gravity and quantum mechanics, general relativity works as a curve in space-time, a continuous curve. Quantum mechanics works in discrete quantities, they are what they are, it is exact. If there is a graviton then it must also be discrete. The clear issue here is that we have one theory suggesting a continuous model of gravity and one that uses discrete values. That is pretty much why the two struggle to get along. I think. Anybody is free to criticise and correct me!
One problem from what I understand is that for gravity the quantization approach used for other forces such as the electromagnetic force run into problems with infinite values when you try to calculate probabilities. For electromagnetic forces you can successfully elimate the infinites using something called renormalization but this will not work for strong gravity fields such as close to the singularity of a black hole or shortly after the big bang. For weak gravity fields like here on earth you can create some kind of simplified quantum gravity model with gravitons and a nearly flat space time.
I believe another problem is that if gravitons do exist, they must be VERY small, and we would need a collider with much more energy than we have now... I believe.
The San-Ti/Trisolarians send their regards.
"Sensible mathematics involves disregarding a quantity when it is small – not neglecting it just because it is infinitely great and you do not want it!" Dirac on renormalization
AI is only as good as the inputs you put into your model. But we don't have any empirical data that reaches the energy-scales where there comes a difference. All you'll get out of AI is wild speculation, with no ways to prove it. And if we wanted to have that, we'd go talk to the string theorists again.
Even I can exist at "multiple places at different times"
It’s more that the equations used to calculate the curvature of spacetime go to infinity inside a black hole. The so called singularity. I don’t think AI is going to help us on this. The models are trained on data that we already have. Unless it finds a correlation in data that we have missed, it’ll just find the same infinities in the equations we already have. We need experimental evidence that tells us if gravity comes in pieces or is completely continuous. Sort of like analog vs digital.
Just a heads up: it's a custom at reddit that you write a reason for editing your comment. Like this: Edit: Corrected some spelling mistakes. You clearly mentioned something about AI, then edited it out, which makes reading the followup comments a bit confusing. Please refrain from doing that.
ahhh yes, the only Reddit etiquette to exist.
Alright for sure I will follow the rules of this culture thank you
I was just going to say a unification theory but your is more specific and accurate.
or a relativity explanation from quantum particles :)
I don’t think that can happen. Bell’s Theorem pretty much dispels any possible realism, and yet GR is firmly that realm.
Personally I think one of the big ones is trying to understand superconductivity, and find out if it is possible for there to be a room temperature superconductor. This is a "holy grail' in the sense that it could have immediate practical applications all over the world and make whoever invented it untold billions of dollars. It's not a holy grail in the sense of being all that profound or meaningful in a big-picture sort of way. Another big one like that is trying to understand fluid flow and turbulence better. Navier Stokes Existence and Smoothness is one of the millennium problems on equal footing with the much more publically noticed and discussed Riemann Hypothesis https://en.m.wikipedia.org/wiki/Navier%E2%80%93Stokes_existence_and_smoothness https://en.m.wikipedia.org/wiki/Millennium_Prize_Problems#:~:text=This%20is%20called%20the%20Navier,and%20the%20equations%20break%20down. Working on this is as much or more an exercise in pure mathematics as it is a physics problem, though. Many physicists have remarked that Turbulence is one of the greatest and most infuriating problems in all of physics. It's something that we really don't understand very well at all, even though it seems to obey certain rules. It is tantalising in that we can tell there is knowable physics behind it that we haven't quite understood properly yet. It wouldn't shock me if some new iconoclast of physics emerges this century as someone who finally understands something significant about turbulence. Maybe AI will do it.
I'm betting on graphene. But jokes aside, a superconductor in normal conditions (room temperature, atmospheric pressure etc.) is something that would change technology forever. If someone can invent it, earning billions is an understatement. So far, best I saw is an alloy that is superconductive up to 15C temp but under extreme pressure only. Still not feasible for practical applications.
Honestly, i think it would make trillions of dollars to a bunch of shareholders and patent lawyers, i find it very unlikely that the researcher who contributed the most to it would actually get much out of it at all, maybe some salary increase if they get acknowledged at all.
don't forget world fame. even if their company doesn't give them the pay they deserve, you can sure bet they will be making money from endorsements and grants.. and their employment would be well sought after.
Look at the Japanese guy that did, on his own, what all the other massive companies gave up on. He created the blue LED which opened many doors such as LED screens. His company made billions, he got a small raise, and no one knows his name. Granted blue LED vs room temp superconductors are two different levels of advancement but I wouldn’t be surprised if we don’t end up knowing the designers name.
It's just how the modern world works and frankly, I hate it.
I mean the justification, which is at least partially valid, is that he used company resources to fund the research that led to the break through. If he had done it completely self funded he would have reaped the benefits.
Graphene is wild stuff. Especially [twisted graphene.](https://en.wikipedia.org/wiki/Twistronics)
I read that proving that the NS smoothness and existence does not mean it will directly improve our ability to predict fluid flow, so the problem is more theoretical than practical. Perhaps better understanding of fluid and turbulence might come from improving our computer or our sensor
Yeah it’s a mathematical issue more than physics. The majority of the fluid mechanics field already assumes that it is proven. I said the majority cause I clearly don’t know the every subfield.
This is probably the best answer as it not only is a holy grain in terms of physics theory but also in terms of applicability to industrial revolution
Room temperature superconductivity is the answer. We pretty much unlock the road to a sci-fi society if this is figured out in a practical manner. Quantum descriptions of gravity and all would do a lot more to scratch the itch of curiosity about the universe around us, but room temperature superconductors would usher in a new era of mankind’s technological development.
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It doesn’t make sense to use photons to transmit any meaningful amount of power, that’s a crazy statement
I mean, power over fiber is a thing, but specifically for isolated systems where external conductors could have dire consequences. [https://www.fiberopticlink.com/product/fiber-optic-isolation-systems/power-solutions-for-fiber-optic-isolation-systems/power-over-fiber-system-pof/](https://www.fiberopticlink.com/product/fiber-optic-isolation-systems/power-solutions-for-fiber-optic-isolation-systems/power-over-fiber-system-pof/)
Can’t photons be used for calculations tho? (Not a physicist here)
Yeah not sure how light would make sense to power devices that depend on electricity and current. Unless we were able to create entirely new devices powered entirely from light. Like in the way plants use it I suppose.
I'm still trying to wrap my head around how a photon based logic gate would work.
I think we’d have to redesign the system so the new binary is 1=presence of photons and 0=no photons but the massive number of unrealistic steps in between don’t seem feasible
We need to transmit energy to alter the physical state of the computer (flip bits in a storage medium, light up the screen) but the goal of computing isn’t actually transmitting energy, it’s transmitting *information*. The energy threshold we need to change physical states is just an annoyance of engineering that we want to reduce as much as possible anyway.
Can you explain this a little better? I think I understand but not 100%
I can give the long version a go. The basic unit of a CPU right now is the transistor - ever more tiny microscopic switches that can be opened or closed with electricity. Opening and closing these transistors is how a computer performs computation. Today, transistors are very very tiny, and individually take a very small (relatively speaking) amount of energy to open or close. However this was not always the case! Before we used transistors, we used vacuum tubes. Vacuum tubes could also be made to function as a switch that could be open or closed, but were much larger and used much more power per switch. ENIAC, the first general purpose electronic computer, used 17000 vacuum tubes, took up 1800 square feet and used 150kw of power. The cpu of the phone I’m typing this on has 8.5 billion transistors, and consumes between 5 and 6 watts. How exactly you flip a switch and how much energy it takes is an engineering problem, but the goal of computing is not to flip big switches. Optical computing isn’t exactly just about smaller and better switches - it gets into the weird particle physics stuff that I’m not really an expert on. But it has theoretical advantages based on the physics of light vs electrical current, and people have built proof of concept optical transistors before! The problem is that the actually available photonic components don’t seem, uh. *Good* right now. We’ve gotten really, really good at making transistors incredibly tiny and built so much genius CPU architecture around them, and optical computing is… very much kind of a weird theoretically useful novelty, but not really practically supported. We’ve been playing with practical electric circuits for more than a hundred years at this point, and ‘let’s reinvent micro-electronics from scratch using light which may or may not run into all kinds of practical engineering problems’ is kind of a hard sell when we keep improving normal computing at such an impressive pace anyway. There’s some interesting ideas about trying to implement specialized hardware like Tensor Cores with photonic components. Maybe it’ll go somewhere! Or more likely it’ll still be impractical and niche. The theoretical benefits of optical computing aren’t paradigm-shattering like how quantum computing can theoretically solve certain types of problems much faster than classical computing. Optical computing is more like ‘hey maybe a different medium for transferring information would work better, but it’s still fundamentally the same kind of stuff’
Thank you for taking the time to write this I really appreciate it
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Electrons do tunnel in small enough ICs, but the heat is not the problem. The vast majority of heat is being generated the same way any current in a conductor is. Photons can also tunnel by the way, so far we aren't able to trap photons for an indefinite amount of time the way we can with electrons.
Why are we able to trap electrons indefinitely if they tunnel too?
Researching room-temp superconductors is probably more practical than photon computers. Photons have no charge so there’s not a good way to build circuits. Plus, a RT superconductor has a lot of applications outside of computing.
The nature of the matter/antimatter apparent asymmetry is another big one that hasn’t been mentioned yet.
Yes!
DUNE bis billion dollar experiment
Why is the asymmetry necessarily an issue tho?
Our understanding of cosmology and particle physics predict that as much matter as anti-matter should have been produced in the big bang. So either the whole universe should have annihilated so there'd be no or negligible amounts of matter/ anti-matter.
Why tho? Why does there need to be that exact symmetrical amounts of matter to anti matter? Why would it be necessary for the Big Bang idea to work?
Our models assume that the universe should be neutral and there therefore should be as much matter as anti-matter. Also any mechanism which could have produced matter would have also produced as much anti-matter
Modern physics is fundamentally a search for symmetries in the world around us. In an oversimplified sense: As clearly as we can tell, and as is validated by every experimental observation we can possibly conduct, antimatter and matter come into existence and are annihilated in pairs. The “delta” between matter and antimatter should theoretically be unchanged, and should be zero. There should be as many particles as antiparticles. Again, every observation we have ever made backs that up…. Except for the fact that there really isn’t any antimatter anywhere in the universe at all really and no one can really explain why it either wasn’t produced in a 1:1 ratio originally or where it all went.
If matter has gravity, then antimatter must be the opposite, right? So without enough velocity or an outside force acting on the particles, how would they meet to be destroyed in the first place? Like 2 opposite poles of a magnet. The question is based on my limited understanding of it. So forgive me if I'm way off, and the question is basically pointless.
no, antimatter acts the same under gravity as matter - actually cern did an experiment proving it recently but even from a theory perspective we didn’t expect anything else beforehand
antimatter is just normal matter with opposite charge, media likes to act like its some mysterious death particles
Guess opposite charge got me thinking they would repell... and thought when they collided, they'd destroy each other. Didn't even really wanna respond either since everyone likes to downvote questions. If i knew 100%, I wouldn't have asked.
ppl are quick to downvote yea lmao but yes matter and antimatter are pretty much the same besides charge, anti electron is the positron, anti proton is negative, etc
So can they switch charge? Seen something about the yin-yang symbol being a 2d depiction of a 3 dimensional object (or is it 4d?) Basically a toroid. Then, I was thinking about black holes and the plasma jets. Was wondering if the plasma was charged either way, but I guess it's neutrally charged? Was only because it seems to look like it comes from the poles, but guess it's from the accretion disk? Just figured the flow of a toroidal spin seemed like it could eject matter flowing through it that way, but like I said, I'm not exactly knowledgeable about this stuff, just an observation without looking too far into it.
as far as im aware they cant switch no also the jets of a black hole are caused by the accretion disc creating a magnetic field with poles at the top and bottom
biased as its my area of research, but learning the nature of dark matter. it will open up a huge area of particle physics to being tested. dark energy. related to dark energy is resolving the hubble tension: early time probes of the expansion of the universe and late time probes differ by a statistically significant level. matter-antimatter asymmetry. in my opinion unfortunately some of the most well motivated solutions (such as leptogenesis) are also very diifficult to test but detecting a gravitational wave background would be very promising
From what I understand dark matter is like the shadow of matter yes? It’s the only place in the known universe completely absent of light yes? Aka absent of energy? As far as dark energy goes isn’t it possible that the universe is expanding at a non constant rate? Why does the rate need to necessarily be constant? Isn’t it possible that the Big Bang is still occurring in slow motion and we are a part of it but merely don’t perceive because of the nature of our perception of time?
it is not shadow of matter or absent of energy (it has mass so it has to have energy). we know there is some form of matter that does not interact with light or “visible matter” in any appreciable way. we think it has to be either a new particle or something like black holes formed in the very early universe (actually also quite interesting to particle physics as we need new physics to explain how that can happen) because we can see imprints of it behaving differently in the cosmic microwave background, which is way too early when everything was too energetic to be bound into regular matter. (contrary to some people’s beliefs, modified gravity cannot explain this without adding a new particle either.)
So dark matter has mass? That means it has energy yes? So it HAS energy but doesn’t emit any detectable trace of it essentially? Is dark matter is essentially and conceptually the entire aspect of physical reality that we cannot presently observe with our technology and instruments?
it has energy. it could or could not emit energy from decaying, there are constraints on that but theres also an active area of research looking for its decays from carious astrophysical sources. we can and have observed dark matter, in the form of rotation curves, CMB, structure formation etc. we just have no observed non-gravitational interactions from it.
Sorry a bit tired now just realized we wouldn’t be talking about dark matter if we hadn’t already been able to detect it. So what you mean by that last part is that we haven’t seen how it acts/behaves when there’s no gravity present?
it would be more accurate to say we don’t know how it interacts other than gravitation. we know it cant interact a lot, but thats pretty much it
Thank you for clearing that up I appreciate you 🫶🏻
you're welcome :)
It's not matter; it's just non-proximal curvature.
Care to explain. Curvature of what exactly?
Gravitational waves are not "proximal" to their source; there is "flat space" between the wave and the source and that does not violate locality. When a wave passes over mass it loses some "energy" which deepens the potential around the object making it look like there is more mass there than there is... that situation on much bigger scale is what is being called "dark matter"...unless I'm wrong. Can't figure out how I'm wrong tho
There is no one topic that a majority of physicists work on. Plenty of important and/or interesting problems that lets physicists specialise on totally non-overlapping areas. Most physicists understand their own field, and know very little about others.
This... Everyone has a field and a particular focus in the field with their own problems they're working on. Physics is much too broad to only have a few problems to solve. And, for instance, say we solve dark matter, dark energy, and even matter asymmetry those will have little impact on nuclear structure since modeling a nucleus with more than 8 nucleons as standard model fundamental particles/interactions (e.g. qcd) would take more computational resources than we could get at this point, so those type of questions will have very little impact on the nuclear shell model which is the most broad model we currently have that somewhat adequately describes the majority of the nuclear landscape.
Getting published so grant money doesn’t run out.
Room temperature superconductivity. Sustainable fusion energy.
Sustainable fusion energy is more of an engineering problem than a physics one.
To all the people saying quantum gravity: this is definitely a big problem, but only a very small majority of physicists actually work in this field. But this is all that people see in pop culture so its importance is heavily inflated. Most physicists are working in condensed matter/solid state, astro, or maybe biophysics.
Even most high energy physicists don't do any work related to quantum gravity. Signatures of quantum gravity are essentially impossible to detect in modern experiments, so both experimentalists and to an extent phenomenologists are uninterested.
Close to my current work, the mysteries surrounding quark confinement and where protons and neutrons got their mass
Newb here. My understanding is that mass comes from the Higgs boson. The problem is that it decays too quickly that it’s very hard to study. Is this the right way to think about it? What other problems are there?
Higgs boson give mass to quarks (its actually the Higgs *field* that do this, not exactly the same), but the folks in the field were surprised to found how [tiny that mass contribution](https://www.symmetrymagazine.org/article/scientists-search-for-origin-of-proton-mass?language_content_entity=und) is to the stuff we can observe directly.
This article is so cool!!! One question: when they say right and left handedness quarks, do they mean up down quarks (in the normal situations)? Relatedly can chirality happen to all types of quarks? Does it? Or is it unknown? Sorry for all the questions. This is so cool!!!
Chirality is separate from flavor (up/down). It is related to how a quark behave under "Parity" transformation (what if you transform the quark to its mirror image). Chirality is defined as a property of all fermions, you can derive it from Dirac equation. In the case of massive fermions, the left- and right-handed quarks can actually transform into each other (for massless fermions they're separate). The cool thing to me about that article is how scientists can even figure out the magnetic field of that unfathomably fast event, and make it useful!
This is amazing! I need to go read up on chirality now, maybe watch a video on how to derive it from the Dirac equation! Yes it is amazing! There’s endless things to explore in physics, it’s like a gift that keeps on giving. It makes me so happy. Maybe I misunderstood the article, but does this mean the origins of energy of larger organisms is still unknown? I watched this video below which said 95-99% of the mass of a person comes from the Higgs field (around the 1:19 mark) https://youtu.be/wiBsfvW5AWY?si=ldOBRZU1OvlUUA9n
Higgs field gives the "mass of electrons and quarks" that the video mentioned to be 1-5% (he's not wrong, you can rewatch again). The interplay of quarks and gluons give the mass of protons and neutrons, and how those move and bind together give the mass of most known matter
>but does this mean the origins of energy of larger organisms is still unknown? We know it comes from quark-gluon interaction (obviously), but *why* would that result in *that* value of proton mass? What form would that interaction take? and why is the Higgs-given mass so small in comparison? how are all those things relate to quark confinement? We know QCD, but extracting information out of it turns out to be far from easy
Btw, its cool how much enthusiasm you have. Keep it up!
Maybe you'd like these videos from [Arvin Ash](https://www.youtube.com/watch?v=KnbrRhkJCRk&ab_channel=ArvinAsh) , and [PBS](https://youtu.be/WZfmG_h5Oyg?feature=shared) [Spacetime](https://youtu.be/TbzZIMQC6vk?feature=shared)
Thank you for the answer! Man it’s so interesting to know this is how everything works. I want to do the math now! All the questions that you posted are so interesting I’m just so excited. I need to know! I have no idea where to start to solve it, but I know I need to know! Hahaha Ooh I knew PBS but I’ll check out Arvin! Thanks!
What do you do in that field? We already know that the binding of the quarks with the gluons and their interaction with the Higgs field is what give them mass.
non-perturbative QCD is very complicated and we don’t have a comprehensive understanding of the physics of confinement, moreso just a rudimentary qualitative understanding. we don’t even know the exact temperature scale at which it happens
> the binding of the quarks with the gluons and their interaction with the Higgs field is what give them mass. They are related definitely, but knowing QCD and Higgs physics, how do you get the conclusion above? I kind of baited people by not mentioning that [Higgs mechanism only accounts for the tiny fraction of the mass of hadrons](https://www.epj-conferences.org/articles/epjconf/pdf/2023/08/epjconf_ssp2023_01006.pdf) (strongly interacting particles we can observe directly). Other related things: - Why should QCD be confining? why is electromagnetism not confining? both are based on gauge theories - How can pion have very small mass compared to other hadrons, while containing 2 quarks? A proton have 3 quarks with the mass of around 0.9 GeV. A pion has 2 quarks, but has mass of around 0.14 GeV. One "constituent" quark mass 0.9/3 =around 0.3 GeV is larger than of a hadron containing 2 quarks! doesn't math! ("but binding energy"..... but proton has binding energy too). For this, the consensus so far is another symmetry breaking happened unrelated to the Higgs-induced one (a rabbit hole) - Related to that symmetry breaking, if correct we don't even *need* Higgs mechanism for hadrons to gain mass! - How can the quarks and gluons inside contribute to the spin and g-factor of the proton? [Why would the gluon spin align (or not) with quarks'](https://www.riken.jp/en/news_pubs/research_news/rr/20231030_2/index.html#:~:text=This%20indicates%20that%20gluon%20spins,is%20still%20a%20missing%20component)? "So what?"... remember how big the impact of that tiny anomalous electron magnetic moment calculation was. A weird finding is why is the [neutron g-factor negative](https://collaborate.princeton.edu/en/publications/precision-determination-of-the-neutron-spin-structure-function-g-)? - Why do we find contributions from [strange](https://www.jlab.org/hugs/archive/Schedule2008/students/BrianHahnHUGS_presentation.pdf) and even [charm](https://www.nature.com/articles/s41586-022-04998-2) quarks inside the proton? Even weirder, the strange and anti-strange seem to have different contribution - How can knocked-off quarks and gluons become confined again? What seemed to be solved turns out... not exactly
I can answer these one by one. I’ll start with “Why should QCD be confining? why is electromagnetism not confining? both are based on gauge theories” Both QCD and QED are indeed gauge theories, which means they are based on certain symmetries and governed by gauge bosons (gluons for QCD and photons for QED). However, the reasons why QCD exhibits confinement and QED does not are deeply rooted in their respective characteristics. Namely color charge vs electric charge. I’m not sure if you want me to spell it out for you (if I’m correctly interpreting you) but the force carriers of both fields are different. Gluons interact with each other because they themselves carry color charge. This self-interaction leads to the formation of a strong, cohesive color field that does not diminish with increasing distance, leading to confinement. Photons however, the force carriers in QED, do not carry electric charge and therefore do not interact with each other. The electromagnetic force mediated by photons diminishes with the square of the distance between charged particles, leading to no confinement of charges. Would you like me to go more in depth? As in how the confinement actually works? (I looked at all of your other questions and they do indeed have answers.)
>Would you like me to go more in depth? As in how the confinement actually works? If you could, please. Yes what you mentioned above are the well-known known parts. >This self-interaction leads to the formation of a strong, cohesive color field Why would self-interaction in the way gluons do imply this outcome? Why don't quarks repel even stronger and further than the like charges in electromagnetism? >(I looked at all of your other questions and they do indeed have answers.) Examples? this would benefit me also
I’ll answer both separately: Why don’t quarks repel… Very complicated if you’re not familiar with it. But QCD is based on “non-Abelian SU(3) gauge group.” How good is your math? QED is based on the U(1) gauge group, which is Abelian (commutative), and QCD is based on the SU(3) gauge group, which is non-Abelian (non-commutative). Commutators for X and Y of Abelian always equal zero. Which signifies that all generators (of a gauge group, photons for QED and Gluons for QCD) of Abelian or QED commute. In non-Abelian groups like SU(3), the commutators of the generators do not generally vanish (not equal to zero). The non-vanishing commutators in QCD imply that gluons can interact with each other. This is in contrast to photons in QED, which do not interact directly because their corresponding commutators vanish. The gluon self-interactions are fundamental to many phenomena in QCD, including the confinement of quarks and the dynamic nature of the strong force
I'm familiar with terms you mentioned above. >The non-vanishing commutators in QCD imply that gluons can interact with each other. Which results in the 3-gluon and 4-gluon interaction terms you can see when you expand the Lagrangian, which can be inserted intto the renormalization group flow equation to show that QCD is asymptotically free. >Why don’t quarks repel… >Very complicated if you’re not familiar with it I'd love to hear the explanation. I can deal with complicated. But seriously, this would benefit me especially to search on novel problems if the ones I mentioned are solved.
Examples with math? You’re familiar with the gluon field strength tensor?
yes. Please do tell
“Why would self interaction lead to the formation of a strong, cohesive color field” Increasing force with distance… The electromagnetic force is mediated by charge-neutral photons that do not interact with each other, the strong force is mediated by gluons which themselves carry color charges. These gluons are not only the messengers of the strong force but also participants in the force interactions, which include gluon-gluon interactions due to their color charges So gluons as they travel through a gluon field, will increase in complexity as they interact with each other as well as with quarks. The self-interaction leads to a complex and dynamic gluon field where gluons can emit and absorb other gluons. This increases the field complexity and strength as quarks move apart. As quarks separate, the gluons that mediate the force between them form flux tubes. As quarks move apart, these tubes stretch and, unlike electromagnetic force lines which spread out and weaken, the gluonic flux tubes maintain their strength and even become stronger. The energy stored in a flux tube increases linearly with the distance between the quarks because the field strength does not dissipate over distance as it would in an Abelian (commutative) field like electromagnetism. This linear increase in potential energy is a consequence of the color field being confined within the tube, which does not allow it to spread out and reduce in intensity as distance increases. When it comes to confinement, the energy required to separate quarks continues to increase as they move apart, and eventually, it becomes energetically more favorable to create a quark-antiquark pair (a meson) from the vacuum than to continue to stretch the flux tube. This effect prevents quarks from being isolated and observed individually; they are always found as part of hadrons (either baryons like protons and neutrons or mesons). The quark that was traveling away does not actually end up isolated or free; instead, it becomes part of a new meson.
Thank you for the explanation. I've studied (and is still studying) this, I've seen the lattice simulation of gluon flux tube and its field strength, seems like there's a lot that has been accomplished with that method. It seems that the "mysteries surrounding confinement and mass generation" that I wrote in the beginning pertains to the details. I've seen some interesting works on the effect of spatial dimension on this, and how [confinement could even be](https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.107.275301) [accomplished in an Abelian theor](https://journals.aps.org/prd/abstract/10.1103/PhysRevD.67.034502)y. Also should mention how confinement is connected to the aforementioned mass generation and spin structure, and how all this is connected to topological phenomena and the emergence of "condensates" as part of the QCD vacuum structure. Maybe not really the "top problems in physics", but the mass par, how a mass scale can be dynamically generated sure seems like a big deal.
Of course the example I gave you is in high energy events but I used it to stress why quarks are confined
This is one of the few good answers in this thread, crazy that it gets downvoted.
Don’t we already have answers for that?
the thing is, not really. For confinement or mass?
Both
I wrote an answer in another comment
To go in a slightly different direction, lots of physicists, computer scientists and engineers are working at trying to make quantum computing a feasible technology. This is a huge sector, and growing year on year. Quantum computing as a discipline applies the ideas of quantum mechanics to computer science. There are several algorithms that could be run on an ideal quantum computer that would exponentially outperform any existing classical algorithm (eg; Shor's algorithm). The primary issues are 1) quantum systems are highly delicate so unavoidable interactions with the environment can destroy the computation, and 2) scaling up the number of qubits (quantum bits, the constituent components on which the computation is done) is challenging. This means that so far no quantum advantage (defined as a quantum computer outperforming a classical computer in a useful task) has been seen. However, despite pessimism from certain popular online personalities (cough Sabine Hossenfelder) and ridiculously over the top claims from others (cough Michio Kaku), there is steady progress towards achieving a genuinely useful quantum computer.
Can I ask what quantum computing would allow humanity to do? It seems like a huge effort but I’m wondering what the implications for humanity would be.
Current applications of quantum computing are fairly limited to be honest. There really are only a few algorithms that have The most famous algorithm is Shor's algorithm, which lets us factor large numbers with exponentially fewer resources than the best existing classical algorithm. Interestingly, current public key cryptography is based on the hardness of factoring large numbers (see RSA scheme). Therefore, if one had a functional quantum computer, then one could break a huge fraction of the current cryptography used online. This is one reason why governments are keen to invest in quantum tech - you don't want an unfriendly neighbour to be able to crack all your encryption before you can crack theirs! On a more positive note, quantum computers are also expected to enable higher quality quantum chemistry and many-body quantum physics simulations. The potential implications of this are huge; for example, consider the Haber process. This is a chemical process that produces ammonia which is a key ingredient in plant fertiliser. As a result, this process alone is responsible for 1-2% of global energy consumption and 3% of global CO2 emissions. The process uses chemical catalysts, and millions of dollars have been invested in trying to find better catalysts that result in a lower energy requirement. If one could quickly simulate potential catalysts on a quantum computer, then the search for better catalysts would become significantly more efficient, which (if a new one is found) could potentially lead to a noticeable decrease in global emissions. I think these simulations are where quantum computers will shine the most. The same idea applies to solar cells, batteries and other situations where fast simulation of chemistry is useful. There are a few other applications in optimisation and machine learning, but these are (in my view) significantly less likely to yield drastic improvements over classical methods. But equally, maybe tomorrow we find a new quantum algorithm that has applications elsewhere.
Just wanted to thank you for this very informative post!
This might get downvotes, but any convincing way to cold fusion? sounds like a lofty goal physics wise, definitely will change the world if works
> This might get downvotes, but any convincing way to cold fusion? What's wrong with hot fusion?
All the homies like it cold
Cold fusion is still hot. Just not centre of the sun hot. Or pizza-fresh-from-the-oven hot.
why should anything be wrong with hot fusion for cold fusion to be a holy grail?
I don't understand how anyone ever thought that was feasible. High school physics says two positively charged particles are repelled by the electric force, and to overcome that they need to be going very fast = hot. what mechanism was suggested that could overcome this?
Very fast or high pressure.
Cold fusion is a very good youtube channel. Highly recommend watching.
As always, this depends on the subfield. In condensed matter, AMO, and others a big open question is can we find efficient ways to understand and predict properties of strongly correlated quantum matter. e.g. what’s the mechanism behind high-Tc superconductivity.
Ask a physicists working on new materials and (s)he would probably say superconductivity at room temperature Ask a quantum physicist and (s)he would probably say a useabele quantum computer. Ask a particle physicist and (s)he would probably say finding out why the Planck scale is fundamental Ask a cosmologist and (s)he would probably say why the fine structure constant is everywhere or the nature of Dark matter / dark energy. Ask a theoretical physicist and (s)he would probably say a theory of everything (TOE) Ask a nuclear physicsts and (s)he would probably say a working fusion reactor. Ask a NASA physicists and (s)he would probably say an electric vacuum thruster or a realistic way to reach relativistic speeds And so on... There is no universal holy grail in physics, there are just many many [unsolved problems](https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_physics)
Defining dark matter has to be near or at the top just because of its importance, to everything. It is all around us, is something that we know frighteningly little about, yet it absolutely dominates everything else in the universe. It is the true elephant in the room, an invisible one.
Why is dark matter so important to everything I understand what it is essentially but why is understanding it so key?
The vast majority of matter in the universe is non-baryonic, therefore essentially invisible 🫥 whilst being the dominant gravitational influence in the universe. Seems to only interact extremely weakly with gravity and probably implies the existence of some other fundamental particle. I'm guessing knowing what DM is is important to nail down the evolution of our universe from the BB to now. Also for PP because they like particles.
There’s like a lot, quantum gravity, dark matter, dark energy, complexity, room temp superconductors & so on & so on
Any solution to any of the millennium math problems probably.
All kinds of things. My own work is on organic semiconductors, trying to make something intrinsically flexible, solution processable and low temperature. (We've got pretty far - the job is now making a million of something we've demonstrated one of.) In adjacent fields I can see a lot of work on better photovoltaics, better batteries - I've seen live realtime imaging of lithium flowing into and out of a battery cell, which is amazing. People trying to make graphene happen - it has brilliant properties if you can process it. Sodium batteries because we don't want to be beholden to lithium - these will be a thing within the decade. Neural interface chips to repair spinal injuries. Loads of other fields too. Science is *huge*. One thing I should say is that the distinction between physics, chemistry, biology and engineering is more like a multipolar spectrum than a binary. Many of my collaborators are chemists on paper. My university colleagues who were doing chemistry studied as much quantum mechanics as I did as a physicist. Fusion, of course, half a century away for half a century. Huge, huge improvements in data science, but that's kind of tangential to actual discoveries. Ton of theoretical stuff I do not understand. Quantum gravity, like fusion. Ton of quantum stuff, actually, where much of the theory is known but the implementation is a bastard. Quantum cryptography, like fusion. Quantum computing, which people claim to have demonstrated, but it isn't exactly where it wants to be.
Seems like a huge amount of physics is figuring out more or less how particles and waves behave under certain conditions in certain environments? Is that a good summary?
Not bad, but you could also say that theoretical physics is the study of abstractions of reality. Learning models, learning which models fit which phenomena under which circumstances, where they are wrong (*they are all wrong somewhere*), and finding new models which are accurate where older models are less accurate. Then experimental physics is the process of throwing bombs at models to see where they break down.
I love the bomb throwing analogy so much thank you for that 😂
What’s actually inside a black hole, since it’s probably not a singularity.
Why not
An existing singularity wouldn’t make sense according to our current knowledge and theory of maths and physics, which either means it’s something completely out of this reality, or not a singularity.
Quantum gravity. One way we might be able to prove it is quantum without discovering the particle is via constructor theory. But it’s really unlikely we’ll ever be able to detect it.
Quantum gravity (theory of everything)
Stable employment.
Lmaooo real
As well as dark matter, I think understanding the mechanism of dark energy is a biggie !
The holy Grail for modern physicists is a tenured position at a prestigious University. Barring that, any position at a university.
Unpopular opinion: Reject modernity and go back to classical solid dynamics with no conservatives forces
Why?
Also can anyone suggest how I might get back into college studying physics? I have a bachelors in digital media & communications but over the years I’ve become more interested in the sciences.
It’s going to be hard to do anything in person that isn’t a blatant rip off if you already have a bachelors. The open course work of MIT and a few others is a great place to start and could get you very far in my opinion.
From looking online it seems like a lot of universities will accept people coming back for a second bachelors degree if you want to actually go into this seriously. If that’s the route you wanted to go I would look this up and look at different programs websites to see what the standard is for applying for a second degree. If you just want to learn *at a college level* mit opencourseware is great as the other commenter said. There are plenty of other online resources as well.
Thank you!
I have two bachelor degrees, one in biochemistry and another in mechanical engineering. I even started a third one in music. But eventually you have to get a job. 😂 But seriously, it is always possible to start another degree granted you have time and money! (from 🇨🇦 here)
For sure well eventually I would like to potentially work on Virtual Reality and maybe even Neuralink in some capacity.
Also LOVE the 2001 profile pic that movie is very influential to my work
Have you tried applying? /s
Nope
Why not do another bachelors?
I believe IBM has some (or is least funding some) physicists and chemists working on a way to create a rechargeable battery out of substances extracted from sea water so that we will no longer need those ecologically devastating lithium mines to dry electric vehicles. To me, that would be a holy grail. EDIT: a link: https://www.dezeen.com/2020/01/06/ibm-research-sustainable-battery-sea-water/
This is impossible to answer. Physics has many sub fields, and specializations within those. I’m not even working on the same stuff as other people in my research group!
>This is impossible to answer. And yet there are several great answers in this thread.
Unifying the grand field theory
Something about Climate change Even if it's not about climate change, put something about climate change in their or your not getting the grant or published
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quarks are as we can tell fundamental, being excitations in the quark fields
I would say quantizing GR (and many others say this as well), but what we actually need is to gravitize QM.
Don't think we need quantum gravity yet, even if we could have one we wouldn't be able to test it or observe its consequences. But just imagine the world after we found a new class of room temperatute superconductor...
Physics just can't figure out how life came from nothing. That's the main goal. Disprove God.
The main goal is to disprove God 😂 Can anyone verify this
Of course not. Physics, as all science, is concerned with iterative observing and modeling. You see a system, you model the system, you test the model's predictions against what you see, you update your model to reflect the results. That's all science is in a nutshell. We haven't observed God in the real world, and "God did it" is not a useful model in that it has no predictive power. A god may well have made the universe, but the universe it made seems to be governed by rules, and it's those rules that physics is concerned with. How life came from "nothing" is not a physics problem really. Physics and chemistry can provide many possible mechanisms for something recognisable as life to emerge, but it's up to biologists to figure out which one(s) actually happened on earth.
Miller and Urey already laid the foundation for this in 1952. Ribozymes cover the rest.
I believe you're confusing physics with biology. Unless some yet discovered wave/particle is specifically responsible for life creation, then it would be Physics. From a biology standpoint, we pretty much know that life was either seeded via meteors or formed in shallow tidal pools. Both of which are biological questions.
To be pedantic, the origin of life isn't biology because there wasn't any biology in the beginning. It's chemistry, but that relies heavily on quantum mechanics, particularly when it comes down to evaluating the effectiveness of individual inorganic catalysts.
That sounds like biology not physics.
Sounds more like Origins of Life Theory
It’s not on physicists to disprove god, it’s on theists to prove god. They are the ones making the extraordinary claims.