Please… No More Loop Quantum Gravity…

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I was recently alerted to a video by my friend and colleague Brian Keating that claims Loop Quantum Gravity (LQG), string theory’s biggest competitor, has been disproven. I was somewhat surprised by this because I was pretty convinced it is for all practical purposes untestable -- much like string theory. I had a look at what he is talking about.
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[@SabineHossenfelder]

This video comes with a quiz which you can take here: quizwithit.com/start_thequiz/1727327385441x478164094322009800 You can now also create your own quizzes on my website! Just set up an account and a creator profile. ChatGPT will help you: Click on "Create Quiz With AI"

[@Thomas-gk42]

👏

[@osmosisjones4912]

it's finally completed: kzbin.info/www/bejne/oIOYfWBmZ9CcfLc

[@duelenigma7732]

Maybe like a particle, “observed” heavenly bodies behave differently.

[@user-bv1qy9ck2k]

Rovelli is not wrong, the problem is that we still do not understand that certain points of view have a very specific mission. The mission of string theory is to say everything that can be said about vacuum energy. LQG's mission is to say everything that can be said about the concept "bounce". They don't compete with each other and we still don't understand it...

[@henrythegreatamerican8136]

Let's be real. The main problem with Loop Quantum Gravity is how low IQ people like me see that phrase and immediately tune out. We need to think bigger like movie studios. Rename it to something like "Quantum Loop: The Fabric of Reality." And under that title come up with a cool tagline: “In a universe where time bends and space dances, the ultimate truth lies within the loops.” Imagine how many low IQ people like me would read something like that.

[@DataIsBeautifulOfficial]

If Loop Quantum Gravity had a dollar for every time it got disproven, it could fund a real experiment.

[@creativeb549]

lol hahaha

[@c.jishnu378]

Fr.

[@mm-yt8sf]

but if they knew they were getting these dollars they could propose an arbitrarily large experiment that would need more money than even that 🙂

[@lorn4867]

😂

[@wayneosborne2506]

😂

[@parrotraiser6541]

In short, physicists have tied themselves into knots with infinitesimally small strings. Have any passing topologists jumped into the fray?

[@andrasbiro3007]

Yes, but escaped through a loop-hole.

[@safestate8750]

Unfortunately knots are only possible in three dimensions, so this is impossible in string theory

[@parrotraiser6541]

@@safestate8750 Don't strings have all sorts of spare dimensions wrapped up in them?

[@violjohn]

What about point-free topology?

[@mandrakejake]

​@@safestate8750that is interesting and I will have to think about it..

[@glypheye]

There’s nothing wrong with conceiving/believing theories which prove themselves wrong eventually. The key is to not go down with the ship, so to speak. Ego’s cling to arguments. They may also cling to the notion that every facet of reality is testable.

[@ThomasPalm-w5y]

The Poisson spot is a famous example. Fresnel had a new theory for light, Poisson claied "that can't be true, it would lead to an absurd consequence", Arago went home and tested and fount the Poisson's thought example actually supported Fresnel's theory.

[@glypheye]

@@ThomasPalm-w5y Nice example, TY! It’s perhaps less jarring to simply be identified with the science of discovery itself rather than whether or not one becomes lucky enough to be entombed as a feature within which one’s theories proved correct and ground breaking….like Einstein being the right mind at the right time to become a bopped bobblehead on our favorite science informant’s countertop 😁

[@-danR]

There's something wrong with a theory that has too many theories. String Theories is/are just, in Trumpian terms, "the concept of a plan".

[@ShawnHCorey]

Except that they're not theories; they're hypotheses. They are not theories until proven.

[@drbuckley1]

@@ShawnHCorey I've pondered the difference between hypotheses and theories for a long time, and I'm not entirely of a mind with you on this. I think of hypotheses as predictions and theories as explanations. Same thing with laws and theories. Laws are mathematical and theories are intuitive.

[@BeautilAliceShaw-k6y]

While listening, it occurred to me, does anything move at the speed of light C? Do photons ever travel at this speed or do they just get really close to this speed? If the vacuum of space is not truly a vacuum then travelling at C is not truly achievable.

[@brunonikodemski2420]

I agree. As an electrical engineer, I have never measured "anything" at the speed of light.

[@EthelredHardrede-nz8yv]

@@brunonikodemski2420 You don't recognize a Plagiarizing Spam bot when you see one. Report it.

[@EthelredHardrede-nz8yv]

Plagiarizing Spambot. Please report them.

[@DrBrianKeating]

Don’t shoot the messenger- I’m just explaining what the paper authors told me and has been reported for years.

[@aidanclarke6106]

As Lee Smolin said in an interview : "Sabine makes no prisoners" 😂❤

[@MrPDTaylor]

You weren't just reporting when you made the claim that loop quantum gravity is disproven.

[@Toxicpoolofreekingmascul-lj4yd]

Physicist duel! Partice accelerators or space telescopes, choose your weapon.

[@SabineHossenfelder]

I'm not blaming you, I know that a lot of people have tried to spin it that way.

[@chrismcmullen4313]

We're all messengers of one sort or another. Youd have to ask the data brokers as to what statiscal relevance reaches the 'message' level. You dont have to have a college degree to estimate the risk zones for getting shot. Along with the more obvious ones poitics and trans matters might be on the rise. If you were to estimate the zones of lesser risk Sabine would be a good place to bet your money...

[@karoshi2]

So they claimed, it's testable, it has been tested, and it's not (entirely) correct (possibly). That's how science is improved. String theory on the other hand is not testable, which is why it didn't fail. Imho doesn't make it a winner in this battle.

[@Vastin]

If we're being strict about our scientific definitions, it makes String Theory not even a contender.

[@JosePineda-cy6om]

@Vastin exactly. As it's not even testable, in Kuhn's view, it's pre-scientific. It's still methodical, has interesting theoretical support, etc. But it's not even part of the paradigm yet. Feyerabend wouldn't even care about elegance or self coherence, only if its predictions are statistically more right than wrong- that's ultimately why he rejected astrology as science, way too low success rate (yeah, Feyerabend was a bit extreme as a science philosopher...)

[@nickrr5234]

Of course it's testable. For instance, if it can be shown that there are only 4 space-time dimensions, string theory is proven false. Whether we, as humans, are capable of testing it is another question, but whether or not a theory is scientific shouldn't be down to whether we are able to carry out the relevant tests.

[@4vR3n]

No, it is not testable. At least not in any meaningful sense. In that regard, religion is also testable , just that we will, conveniently so, never have the tool to test it.

[@Vastin]

@@nickrr5234 How do you disprove the existence of higher dimensions? You could prove that they DID exist, but you can only ever hypothesize that they don't.

[@carlbrenninkmeijer8925]

You lost me. That is not your fault.. !

[@SabineHossenfelder]

Sorry :/

[@GrahamChristie-jg8sw]

If someone comes up with an idea that has the possibility for explaining quantum gravity, how would you know it might have merit today?, Is it a popularity contest and people work on the popular thing to find proof, or wait 20/30 years and say well he/she was on the right track and apologies for putting them in the funny farm 20 years ago. Honestly how do you tell if something has a glimpse of merit.

[@SabineHossenfelder]

yes, very good point. It makes one wonder whether this is a good research direction to pursue at all, doesn't it?

[@garrett3955]

@@SabineHossenfelderthe sophons will stop us from making any scientific progress so we should just stop all research.

[@Don.Challenger]

Like a retraction, they should acknowledge and apologize -becoming angry then, but having nothing or less to show for it now.

Sort of like belief in a deity.

[@elinope4745]

You would be able to see it's merit with predictions that can be checked. Gravity alters the way that things move, so at a quantum level it changes interference patterns. Quantum gravity theories would not only have to explain this but also use the explanation to make predictions about the nature of these changes. Particles in accelerators gain mass with the energy, this alters their local gravity. The differences can be measured.

[@tim57243]

Sabine, I would like to hear what you have to say about Turok and Boyle's idea about explaining the Big Bang as being a mirror and having very little more than the Standard Model. No inflation. Gravity problems are decreased by having some large number of particle-free fields that somehow remove the singularities. Dark matter is right handed neutrinos.

[@peterthepumkineater]

Yes, I asked Sabine the same question last year but never got a reply. Now that she has at least acknowledged the question I'm somewhat more hopeful.

[@DrDeuteron]

Are they standard model right handed neutrinos, or some kind of Beyond Da SM right handed weak interaction thing? (That's always been my favorite...I don't want handedness in my unbroken symmetries).

[@tim57243]

@DrDeuteron Briefly, I don't know. Turok is sticking to the Standard Model as closely as he can. His left handed neutrinos are massless, which I gather the SM requires. I don't understand how the right handed neutrinos get their mass in his story, but then I don't understand either how electrons get their mass in the SM so that doesn't mean much.

[@Robocop-qe7le]

yet we know Einstein is not entirely correct don't we

[@Azariy0]

Damn, my respect for Einstein just went up a lot. The man (and whoever helped him) invented a lot of math explaining a lot of things, pushing physics really far in one leap. And now we're catching up to his theories and trying to go further. But it's just not the same, and we're struggling.

[@jayr526]

If only the aliens would bring Elvis and Einstein back.

[@thealienrobotanthropologist]

Einstein didn't invent any math. Lorenz with some contributions from Poincare invented the math and the physical explanation of special relativity. Riemann, Gauss, and minor contributions of a few others invented the math of General Relativity. Hilbert was the first to formulate the physical theory of Einstein field equations. Einstein contributed the two postulates of special relativity and the equivalence principal for general relativity. The attribution of credit is a surprisingly unreliable business. Newton is credited with wholesale inventing all of Newtonian mechanics out of nothing. His actual contribution was reinventing calculus (several people invented it in the past) and using it to create mathematical descriptions from the qualitative descriptions and limited formulae of motion, gravity, etc. created by others. Some of his other work was more completely original though.

[@BenGras]

The paper title.. Stringent Tests of Lorentz Invariance Violation from LHAASO Observations of GRB 221009A Is that first word (STRINGent) a little poke at string theory perhaps :-) ?

[@Thomas-gk42]

😅

[@SabineHossenfelder]

ha, hadn't thought of that!

[@Robocop-qe7le]

Well at least Smolin et al. proposed something when string theory was the only game in town.

[@dahlia695]

My unprovable theory beat up your unprovable theory

[@jayr526]

My unprovable theory, which I am still working on, gets the winner!

[@DanielHeinrich-vg8qr]

If Albert doesn't like it, it must be wrong

[@Don.Challenger]

Albert has the two brawny shoulders that most of the edifice of science stands on now. Science: "Albert is my rock." Who will replace him (that Hulk like figure) is for a far future day it seems.

[@ThomasL58]

Albert didn't like QM ("God doesn't play dice"), and formulated the EPR paradox that would supposedly disprove it. Alas, Aspect, Clauser and Zeilinger won the 2022 Nobel prize for experimentally proving that QM is right, and thus that Albert was wrong.

[@msromike123]

Never let measurements get in the way of your theories. It just means the model needs tweaking.

[@scotthammond3230]

Is this an existential problem that physics is painting itself into? Over the last 100 years all the easy fruit has been picked. The age of particle accelerators is coming to an end, with seemingly all the theoretical particles having been found or ruled out, with larger accelerator projects now only hoping to find something new rather than having specific targets. Novel experiments only chipping off exponentially smaller bits of the puzzle, etc etc.. when all the rank and file physicists realize the great dead end that is the big seemingly insurmountable problems, will they all start to leave the field? Then without all the talented minds working in the field, advancements will be fewer and farther between. Are we headed this way or not?

[@omardiaz6255]

I mean, in particle physiscs, maybe, although there are new non accelerator related experiments to test the standar model, like the dipole moment of a neutron, i belive, cant remember correclty. And the double beta decay

[@danieloberhofer9035]

"The end of physics" - isn't that what Heisenberg has been told by his professor when he started studying physics? (Could've been Schrödinger, I don't exactly remember the anecdote.)

[@CosmoPhiloPharmaco]

SkyDivePhil (Phil Halper) already responded to your argument with an interview from Rovelli himself.

[@notanemoprog]

BOOM

[@Mentaculus42]

Interesting youtube video, but Rovelli was rather “hand wavy” in his explanation and unconvincing.

[@notanemoprog]

@@Mentaculus42 Pertinent comments from that video: "imPyroHD 2 weeks ago to be honest, this is very subtle and im sure that not many theoretical physicists even fully grasp (in the context of LQG) what Rovelli is explaining here, so i wouldnt expect Keating or any experimentalist to get it. The problem is more so that they make confident claims when they dont actually understand the subject at hand PhilHalper1 2 weeks ago imPyroHD exactly, I don't have an issue with an experimentalist not understanding the details of the theory. But if hes going to declare it dead to the world and potentially ruin a lot of people careers then youd think he could just check if LQG makes this prediction. I remember loking into this more than 15 years ago and quickly found it did not. Why couldnt Brain do that?"

[@imPyroHD]

@@Mentaculus42 Because he was trying to simplify things that can only be explained through pages of maths, who are YOU to say he was unconvincing?

[@Mentaculus42]

@@imPyroHD He was “LITERALLY WAVING HIS HANDS” to try to describe what he was talking about!! You do not need “PAGES OF MATH” when a simple diagram/s will suffice. He is smart enough to know that this issue is very important to his argument, so to NOT BE PREPARED WITH THE NECESSARY VISUAL AIDS is a rather “unconvincing” tactic. It puts his argument in a bad light.

[@khachoang1719]

I hope that 5-30 years later, quantum is no longer a buzz word 😊

[@carmenmccauley585]

Oh same here Please!

[@mandrakejake]

When was 'Quantum Leap' on TV? 😄

[@ianstopher9111]

That would be a quantum leap forward in communication.

[@iridiumnext4126]

why are you saying this here ?

[@osmosisjones4912]

Why is the speed of light the speed of light . Maybe at least 2opposing forces pulling in space and speed of light is how it ends up

[@MrMichiel1983]

Something like that which has to do with scale; think of a box filled with moving perfectly bouncing particles. If we would increase the size of the system under the gas laws the particles would seem to slow down relative to that new scale (lower pressure given same number of particles in larger volume). However, if we were to increase their speed (or temperature) as well there would be no relative difference (in pressure) and the point particles would not "notice" the difference. Now we can't increase the speed of photons, so the gas law doesn't directly apply, but we can sort of translate to a concept of scalar relativity. We can assume that the absolute size of the box as well as the absolute speed of its particles are denoted by a single number to recover the behavior of a constant value for lightspeed as a ratio between those numbers. It's an analogy, but another way of saying it is that in our thought experiment lightspeed is rather similar to the number of particles which simply doesn't change when you resize the box. Now reality is a bit more technical but you can imagine that changing the fine-structure constant on par with a variable lightspeed would yield the same behavior as constant fine-structure and lightspeed values. So just like CPT symmetry, there are a few "knobs" in GR and QM that when we turn them in unison nothing much happens.

[@Ray_of_Light62]

Consider a Space where an electromagnetic wave is propagating. All the units of volume which are equipotential, doesn't matter how far they are from each other, are communicating among them at ANY speed, even superluminal speed. Next step in this way of seeing a field in Space - is to replace the "units of volume" with a mathematical entity characterised by few defining parameters, like the four quantum numbers defining all particles. At this stage, I found a number of logical contradictions which are hard to come by; as if a stronger Heisenberg's Principle made BOTH position AND momentum unknowable at ANY time. Either there are energy transitions which we can't see, or - more likely - I followed the wrong track. Either way, Space has a structure...

[@wangtoriojackson4315]

More like POOP Quantum Gravity lol amirite

[@jayr526]

LOOP around th we POOP in the POOL

[@Robocop-qe7le]

@@jayr526 you guys are string theorists lol

[@michaelsmith6420]

I think both loop QG and string theory are both excellent. Gives boys and girls something to do for much of their "adult" lives.

[@kostuek]

Let me guess - you seeded a tree and made babies which is what real adults need to do instead of playing with some theories?

[@kevinvallejo7047]

If people spent more time talking about their work instead of yelling at people who threaten their egos with valid questions, it would not be a physics conference.

[@friedmule5403]

FAST!! Build a larger collider, it must be able to confirm that, or at least the next one.

[@n3mo146]

Aber wenn's doch so schön melodisch von der Zuge geht: Schleifenquantengravitation-Theorie.......Als Nerd kriege ich da immer direkt Wallungen🤤

[@RFC3514]

2:28 - Ah, but he winked! That means he was joking. 😜

[@barryon8706]

Is there a testable theory of everything?

[@RoldanRR00]

You come up with the theory first and then test it because...science.

[@DrDeuteron]

why is your green quark yellow?

[@rreiter]

Imagine if after having tested almost everything, you found a contradiction. That would suck.

[@barryon8706]

@@DrDeuteron It's feeling a little strange.

[@wtfamousone9756]

@@rreiter You could get an idea of this feeling if you look into Gottlob Frege biography

[@Trailerpark-sodapop]

Katie let DAMION see his baby

[@jmcsquared18]

1:59 Holy moly what a collab.

[@chaossspy6723]

i love cats

[@philochristos]

So do I.

[@chaossspy6723]

@@philochristos so does everyone who's not a psychopath

[@quantisz4416]

I love Schrödinger's cat.

[@TheGiggleMasterP]

Sounds like a movie title 😅 "Quantum Loop: Gravity"

[@frankman2]

Looper? Gravity?

[@kiana5066]

what's all this junk of calling untested ideas "theory" and "believing" in one or the other and getting upset at the results of experiments? seriously, when did science become religion?

[@jayr526]

It looks like Satan is doing some relabeling.

[@xcq1]

5:06 Doesn't that mean that there should be some kind of duality, where if you go at speeds ludicrously close to the speed of light, some observers must see your "macroscopic reference frame" being influenced by quantum effects?

[@bobtimster62]

I was wondering about that as well.

[@Thomas-gk42]

I was waiting for this since I watched Brian Keatings vid some days ago! Outstanding summary again. So good that Sabine couldn´t resist, such a lovely smile.

[@SabineHossenfelder]

Thanks for your support, much appreciated!

[@yaldabaoth2]

2:06 When I see a list like that, I ask myself "who did what".

[@magicmulder]

They probably split a lot of data among them to check for certain properties.

[@osmosisjones4912]

Doesn't the fact light comes in waves means light can be slowed down

[@exscape]

It depends on what you mean. We already know light *effectively* slows down when moving through a medium. For example, light moving in optic fibre only moves at about 2/3 c, -- the inverse of the refractive index of glass of about 1.5 (or 3/2).

[@Lojdika]

When will there be a video on Nima Arkani's Amplituhedron theory?

[@makimomoo]

Well it failed because experiment said otherwise. So the theory was testable, which is a good thing. Unlike some theories where people have been bullshiting ad infinitum.

[@Maria-t1g3q]

Your channel is a source of joy and inspiration. Continue to delight us with your work.💫🚴🎄

[@RickLambert963]

Germany must really be poor. Where can I send a new shirt? E = mc^2 What value for energy? What value for mass? What value for the speed of light squared? The speed of light traveling through a vacuum may be expressed as: 186,282 miles per second. or 300,000 kilometers per second. or 983,571,056 feet per second. or 299,792,458 meters per second. "Today's scientists have substituted mathematics for experiments, and they wander off through equation after equation, and eventually build a structure which has no relation to reality." Nikola Tesla.

[@MassimoAngotzi]

Ok, now take your meds and go back to sleep.

[@RickLambert963]

@@MassimoAngotzi How very sociopathic of you. The system was designed by psychopaths. That's why it rewards psychopathy and promotes sociopathy. Since the so-called being of civilization, when the Sumerians popped up out of the desert with language, mathematics, the Flower of Life... The conqueror tells his story. That's history. A pack of lies told by psychopaths who weren't even there. WAKE UP ⏰️

[@RickLambert963]

​@@MassimoAngotziIf you can't solve Einstein’s energy-mass equivalency equation, you have absolutely no business speaking about engineering/physics. My aha moment came about 35 years ago. I was back engineering a seal and was calculating density to identify the specific material at the time. The CEO son, who was in university for engineering at the time, walked past my office wearing a t-shirt that had E = mc^2 printed on it.

[@olibertosoto5470]

What I'm getting is that were looking for theories that we can prove but can't find proof that they work.

[@keithmichael112]

Even as a layperson I don't click on videos pushing this(or mond)

[@OliviaMoore-y7q]

Thanks for the vivid emotions you bring to my day. Your videos are a real joy!🍎 0 😽!

[@Handelsbilanzdefizit]

Talk crazy stuff, no one understands. Call it science. If doubt araise, say you're a top notch expert, and critics don't understand the subject. That's mainly what Stringtheory, or Loop-Quantum-Gravity, is about.

[@oakpope]

Imagine all these bright people working on useful things, just imagine...

[@DrDeuteron]

many of them are.

[@eloyball]

Well, at least we were able to test something 😅 Unlike another certain thready theory...

[@nosuchthing8]

How's math working for you NOW

[@siddharthb2633]

Imagine doing your phd in loop quantum gravity.

[@timvw01]

What makes us think that gravity should come in quantums?

[@conscienceaginBlackadder]

Just the long running dogma of unified field, which hopes all the forces are the same sort of thing and will turn out to really be the same 1 force moonlighting in different ways

[@koktszfung]

If I understand it correctly, quantizing gravity is only one of the ways to make quantum mechanics compatible with gravity. The incompatibility arises since an object with quantum properties can be in a superposition of two states, each at a different position in space, yet gravity cannot be in a superposition in general relativity, so they are incompatible. Correct me if I am wrong since I don't know much about neither quantum mechanics nor relativity

[@Thomas-gk42]

@@koktszfung As far as I know you are totally correct. Just instead of quantizing gravity, the inconsistency also could be solved if we would understand QM better and what happens in a quantum measurement. That´s what Dr. Sabine´s passionated research is about (superdetermininsm).

[@Handelsbilanzdefizit]

I guess, space is an emergent phenomenon. Like entropy or time, that also needs many particles.

[@BackwardsJohnsCreations]

Omg perfect! Saw the first half of the video yesterday before I fell asleep again, very excited about sabines opinion on that.

[@koktszfung]

Albert is right once again

[@O4C209]

I don't know anything, but What if gravity is just the way we perceive the 4th dimension? So, it is no more quantum than length or width.

[@AshleyMooreAMS]

Length and width ARE quantum

[@markoszouganelis5755]

Thank you Sabine!

[@bobhillier921]

While listening, it occurred to me, does anything move at the speed of light C? Do photons ever travel at this speed or do they just get really close to this speed? If the vacuum of space is not truly a vacuum then travelling at C is not truly achievable.

[@shracc]

Gravity does travel at C, it is a bit faster than the light going through space because the universe isn't a perfect vacuum.

[@edwardlulofs444]

Can anyone tell me why gravity needs to be quantized? Since gravity is not a force, why quantize it? Wouldn’t quantum gravity imply quantized space-time?

[@conscienceaginBlackadder]

Just the long running dogma of unified field, which hopes all the forces are the same sort of thing and will turn out to really be the same 1 force moonlighting in different ways. I actually thought since cosmology articles in the 80s we already had quantised spacetime, with the Planck length and time. Is news to me from this vid, that the relativistic equations are supposed to hold for distances down to literally zero, I just thought it had to break down on scales as small as particles' uncertain positions.

[@MrBajaJunky]

It seems to be the way to go in order to get a microscopic theory when gravity becomes strong. Right now you get in trouble when you try to formulate quantum mechanics on a curved space-time while the energy of your quantum system effects the curvature itself. This is mainly because you can have superpositions of particles at different places which would also imply a superposition of curvatures. At least thats what I partly understand but I'm no expert on gravity.

[@januslast2003]

I think it also has to do with black holes, where something with a lot of gravitational effects has an impact on very small things covered in quantum theory. I think the whole issue comes down to how Einstein worked on quantum effects in Special Relativity paper, then turned his attention to very big things with General Relativity. But he couldn't extend the concepts in Special to General. He had to leave Special behind, and develop new concepts in General. He might have thought of them as separate worlds. For example, he didn't, initially, think black holes were predicted by his own math. Then after this was proven mathematically, didn't think black holes could exist in nature. He was also sure that Quantum Physics was wrong. So he might have hoped for a new and better theory of the very small, that was compatible with General. However, he (and his colleagues) failed in their attempts to develop one. Perhaps recognizing this failure, the current group of scientists are going the other way: start from Quantum Theory, extend it and hopefully end up with General. I think Einstein is right. We need to look at everything in Quantum Theory again and come up with something better. Something that will actually explain things like entanglement. And find hidden variables, even though Bell's Theorem (which rules them out) seems to have been proven experimentally.

[@edwardlulofs444]

@@MrBajaJunky I see. That makes sense. Curved space does seem more complicated than flat. Maybe I will just go to sleep for a hundred years and see if the math and physics can improve. I really relate to Dr Hossenfelder’s opinion that there needs to be more thinking and less guessing.

[@edwardlulofs444]

@@januslast2003 thanks. That makes sense. I gave up on physics 33 years ago and retired. I have never been more happy.

[@quantisz4416]

2:00 Plot twist: this paper has more collaborators than all the LQG advocates put together. 😆

[@D1N02]

Gravity isn't quantum. So trying to unify it with quantum is useless.

[@Thomas-gk42]

First sentence I agree. To unify it we must understand QM better than that ridiculous mainstream non locality

[@D1N02]

@@Thomas-gk42 locality is emergent

[@TheNorgesOption]

I disagree; it was great that they found a new place to look. It's not so great that someone just wasted an entire career, but now we do know more.

[@Thomas-gk42]

@@TheNorgesOption Well, Lee Smolin did a lot for physics and science, not only QLT

[@Thomas-gk42]

Lee Smolin was always a visioneer, I don't think he's bothered. He has a lot of respect for Sabine.

[@MCsCreations]

Very interesting indeed! Thanks, Sabine! 😊 Stay safe there with your family! 🖖😊

[@drgetwrekt869]

someone commented that the speed of light issue was a bug in early iterations of LQG tho. has this been resolved?

[@imPyroHD]

yes, Carlo Rovelli, one of the founders of LQG said that the theory is fully Lorentz invariant and that the idea its not is a misconception, so Sabine is just saying nonsense here

[@drgetwrekt869]

@@imPyroHD makes sense. I still dont like Rovelli because of his fake forced pacifism. But on a scientific level, he knows what hes talking about. so thats that at least

[@lolloboldo3761]

This is a false prediction of LQG in fact: the spectrum of the area operator (the thing that gives you the minimal area) is not a quantity that is observable in the theory, it is a middle step to reach another thing. It's obvious that experiments did not find this, since this is not even a property of the theory and this is known from at least 2004/2005. Sabine clearly does not know that since, as she stated, she stopped caring about LQG a long time ago. Nonetheless every single member of the LQG community does know that the discrete spectrum of the area is not a prediction of the theory.

[@dellamotta]

Please... No more Loop Quantum Gravity nor String Theory...

[@abcde_fz]

THE ONLY PERSON I'VE EVER HEARD PRONOUNCE ALBERT'S NAME PROPERLY. ---- Just an old kraut's opinion.

[@neilmcnasty]

How can Light have a constant speed, when we all know that it's speed changes depending upon which medium it propagate through? It would be more logical to say that Light itself does not have a speed, but rather a rate of induction, set by the medium of propagation. IOW: Light travels as fast as it is allowed to in any given medium. Meaning: If the medium has no resistance nor capacitance; Light would/could become instantaneous. Now light does no longer speed up after passing through a denser medium like glass and water, and no physical law is broken. Everything becomes simple and hyper-logical. Just like me stepping in to water, slowing down while wading knee deep, it is perfectly expected that I will return to my previous pace/speed as I step out of the water.

[@SmithsMobile]

Nope. Light always travels at speed c, even through different mediums. Take water for example, light gets bounced around and scattered as it travels through it with a net effect that it has to travel further through 1m of water than 1m of vacuum, thats why it appears to slow down but it doesn't.

[@neilmcnasty]

@@SmithsMobile Wouldn't that make shadows in glass and water almost impossible? If it bounces around a shadow would never be able to be sharp under water, yet it is. I can not make this make sense...It does not add up with my 30 years of lighting design, experimenting with various mediums, but I'm still intrigued... Is there anywhere I can find a scientific paper showing/explaining this phenomena?

[@SuperRedstoneman]

​@neilmcnasty there is a video of 3blue1brown about this, also light is an electromagnetic wave so the image of photons bouncing around in water is very incomplete. There is some scattering but a lot of it would just mean the material is a thick fog.

[@neilmcnasty]

@@SuperRedstoneman Thanks a lot for sharing your thoughts and being helpfull! I already subscribe to the channel, so I should be able to find it. 👍

[@yapdog]

0:50 😳Damn... Sabine puttin' the dude on blast🤣 Remind me to never publish my theory on AI quantum wormholes........

[@jimmyjames2022]

"Personally I don't understand why people waste time on this one way or another." But, umm, umm.... ☝🏻☝🏻☝🏻☝🏻

[@joependleton6293]

Quantum gravity & fractal space! Amazing 😯 oversight!

[@martf1061]

1:40 It's pretty much a " no brainer ". Of course that light and all electromagnetic phenomenons don't have constant velocity/speed. Some frequencies will slow down more rapidly than others. Just like sound, EMF's propagate at diferent rates, through diferent medium types.. Less dense = less distance of propagation

[@coscinaippogrifo]

Sabine, what is your favourite theory for unifying quantum physics and general relativity? I

[@anthonycongiano8890]

@0:30 sorry but the biggest proponent of Loop Quantum Gravity was Leslie Winkle. She even famously stated, "how will we raise the children?"

[@frankupton5821]

We should respect the LQGEMC2 communities.

[@guytech7310]

FYI: Gravity & the strong interaction are the same. Hidden in the Reid potential is gravity.

[@Magister_Sibrandus]

Light has color?

[@akash_menon]

The white colour we see has all the colours in it. Isaac Newton, 16th Centaury. Isaac Newton needs to make a comeback in a new birth.

[@Magister_Sibrandus]

@@akash_menon Color is not a property of light. What our eyes detect are certain wavelengths that our brains recodes into colors. Colors are not part of physical reality but are a mental construct. Rather than saying something like "according to this theory, colors have different speeds", Sabine should have said "according to this theory, wavelengths have different speeds".

[@KaiseruSoze]

LQG is background independent. It just hasn't quite seen how to discretize spacetime and be background independent.

[@trumanburbank6899]

Another great video. Are there any efforts to change the phrase, "the speed of light" in the context of "you know what I mean" to something like "the (maximum universal) speed of causality"?

[@alainterieur7583]

What about Planck length? Doesnt it already impose a minimum non-zero size?

[@hotbit7327]

Are you: pro-LQG - say No anti-LQG - say Yes 😅🤣pro-LQG / anti-LQG - Sabine at her best again!

[@surfcow]

"... have become very quiet". Sabine, slayer of bullshit.

[@ofskittlez]

If LQG were to be conclusively disproven, would that prove string theory? Or have any effect at all?

[@DamonNeri]

As energies increase, distances decrease and number of charges increase. Gravity one charge. Electromagnetism 2 charges. Hypercharge 3 charges. Grand unification four charges?

[@jayr526]

Isn't LQG part of a larger alphabetical group with confused ideas

[@lolloboldo3761]

This is a false prediction of LQG: the discrete spectrum of the area operator (the thing that gives you the minimal area) is not a quantity that is observable in the theory, it is a middle step to reach another thing. It's obvious that experiments did not find this, since this is not even a property of the theory and this is known from at least 2004/2005. The quantity associated to the *observable* "area quanta" is something that we still don't have, and on which people is still doing research. Every single member of the LQG community does know that the discrete spectrum of the area is not a prediction of the theory, and I am embarrassed by scientists that try to "disprove a theory" without even having studied that theory. Is like if I, a physicst, publish a paper saying i have disproven cancer, without having studied biology a single day of my life. Pure nonsensical stuff.

[@HobieH3]

Really? Is it mathematically possible to be LESS successful than string theory? Is there negative success?

[@johnkeck]

Excellent! Thank you for the lucid explanation, Sabine!

[@macdmacd7896]

news clip - P Diddy is experiencing quantum loop gravity

[@esc952]

Physics career advice..."Don't fuck with Einstein or bet against the sun rising."

[@Bapate-rh9be]

If loop quantum gravity is not provable - then how was it disproven?

[@winstongludovatz111]

I am betting on the demise of QM in its present form: not developed based on abstract principles (like SR and GR), underwent phases (old / new, with the old being ridiculous), interpretation of wave function not understood by inventors (first believed to be a charge density instead of probability density) , needs a classical system to be quantized (i.e. is a method to fix an incorrect theory), method of quantization not unique, operator ordering rules, Feynman path integrals have no mathematical definition. No reasonable interpretation of what the formalism means, which is the source of hilarious fantasies: parallel universes (and not just a few), retroactive causation from the future, handshakes and negotiations across time, we should replace space time by phase space or configuration space as the true space we live in. These fantasies and associated "philosophies" (wholeness, universal connection) are the true source of its popular appeal. We constantly hear how well it works because deep down the physicists themselves do not really believe in it.

[@SciD1]

It's all bs anyway. Nobody is explaining what gravity IS. All math does is describe its effects.

[@konstantinos777]

It will be very funny when you discover that you've been arguing for stuff that does not exist

[@davidrandell2224]

Gravity is simple Galilean relative motion. The earth’s surface is literally physically the floor of Einstein’s cabin- equivalence principle.’ Too simple for the modern brain.

[@MatthewWaltersHello]

Yay, let's continue down the endless bottomless rabbit hole of pursuing String theory, right Sabine ?

[@augustwest9727]

So I have a red shift question, it haunts my brain when I'm idle. I'm a Plumber and I'll be staring off into a random direction thinking about this. Finally someone asked a few weeks ago what i was doing I said "thinking about red shifts around a super massive black hole.". They were like..."what the F?", I said nevermind mind man". Anyways my problem is red shifts or maybe time dilation.... So: Lets say you have a very large Star orbiting a Suppermassive Blackhole (Sag. A) at (pick a random percentage i don't care) 40% the speed of light. Lets say that Stars entire life cycle is 10 million years. From the Stars perspective it will still live 10 million years and dies. But from our perspective here on Earth it should live longer then 10 million years. So shouldnt we see that light red shifted because the energy it produces and the energy we see must remain the same? And it would red shift due to the extra time we would see it from our local perspective? Anyways... Im a Plumber so feel free to tell me how idiotic this question is... But this haunts my mind when im idle and has for about a year...

[@andruss2001]

Thanks, Sabine! So where are we going? From jawdropping double slit experiment into infinity of evercompeting quantum theories?

[@سیروس.مریدی]

کوانتم شناخته شد۵،،کوانتم شناخته نشده ،،نمایانگر ،،پنهان از نظر،،،در مورد دوم تحقیق و فکر می کنیم ، شناخته شده ها مشخص ، پنجه در نبرد دوم می آندازیم..

[@Italianjedi7]

This is interesting. I recently started believing loop quantum gravity is correct because I very much like the concept of a growing block universe.

[@jeroenvandorp]

I wonder how Causal dynamical triangulation, the theory by Renate Loll et. al. holds up at this moment. IIUC there are similarities between QLG and CDT.

[@qjsharing2408]

I really appreciated Smolin's "Three Roads" book. We definitely need to stop packaging all the smartest physicists into an evermore narrow field that hasn't produced fruit.

[@richardkerner5817]

When I heard you saying "Personally I don't understand why people waste time on this one way or another", I felt that I cannot agree at all. Because if we admit that "time is money", even with low converting coefficient, than we can see that all these people promoting "one way or another", i.e. string theorists, loop-quantum gravity adepts or other quantum gravity inventors, most of them did quite well financially. Of course even a good university position connot make one really rich, but with nice living, decent salary, changing places to participate in countless congresses, colloquia and workshops around the world , you may call it quite a success. No one is living like Diogenes in his time.

[@hippophile]

Sab has a (hem) point. Some theories are just... well... loopy.