i dare not to change that stable number 30

For every question answered two more questions arise.

Einstein " The more I know the more I realise how little I know."@@malcolmabram2957

In another 40 years they'll have an even bigger detector, a more tweaked theory, and still no evidence of proton decay.

When you say you're a bit bewildered by the tweakings of theories, do you mean you think it would make more sense to conclude that those theories have been experimentally ruled out? Or is it the ways that people have tried to tweak them that doesn't make sense to you?

There are many new theories. Tons of them. What they are trying to solve is the nature of dark matter and energy. They are trying to understand why there are quarks and leptons. They are trying to understand why there appear to be a finite number of forces (different people, counting different ways, come up with numbers in the range of 4 - 6 or so). They try to bring gravity into the picture, which is currently not true. They try to understand the nature of matter and energy shortly after the Big Bang. In short, they try to extend our understanding of the laws of nature. We don't understand them all. We've made great progress in the last century, but there is a lot of the way to go.

Sabine’s point (that I happen to agree with) is that these “new theories” aren’t theories at all, because they aren’t a response to observation, but instead are an attempt to create a “more mathematically beautiful” theory than the SM. The reason is that an hypothesis is a response to an observation, and that in explaining the observation it can make predictions about things not yet observed. Think about how GR explained the orbit of Mercury, and the same equations also predicted that light would bend around a gravitational field, which was confirmed during the 1919 Total Solar Eclipse. Various “New Physics” theories aren’t explaining observations that the SM can’t, because SM works great. Rather they are trying to guess what we’ll observe at higher energy levels (or longer timescales) than we can currently generate. This is backwards from the way science usually works. What’s great about this is that when their predictions fail, the theorists can generate another theory and claim that they’re doing science because they moved on when their ideas were falsified. Current results at LHC aren’t too promising for new physics, either. To date, nothing has been unequivocally observed that isn’t handled by SM. But the quest for proton decay will provide grant proposals and publications for a few more years, at least, so there’s that.

@@drdon5205 Thanks for that rather elaborate reply!

@@TheGotoGeek You are mischaracterizing the history. General Relativity was devised as a theory on aesthetic grounds. Only later did it answer the problem of the precession of the orbit of Mercury. In fact, Einstein first miscalculated this problem and only fixed it later. The theory was most certainly not devised to solve this issue. And, on the SM, again I would disagree. The SM does a great job on many things, but there are many questions it doesn't answer. These new theories are all attempts to extend the SM, not on aesthetic grounds, but because those questions need answers. It is true that some theorists use aesthetics to guide their thinking, but what would you have them do? Consult tarot cards? The goal is admirable and you have to try >>something.

GR isn't an aesthetic argument, it resolves an inconsistency. A falling object appears to be accelerating but a falling accelerometer reads zero.

Thanks for the info! Althought I'm pretty certain how this is (not) going to turn out and 3 Sigma is... well, 3 Sigma, it seens like pretty cool research.

U speak weird

99.7% of all results should fall within +/- 3 Sigma. Anything outside of that range has a .3% of occurring randomly and may not violate any theories or models. This is why it's important that science tends to go for the 6 sigma with only 3.4 events out of a million that it was a fluke, which for the most part probably means your result implies that your hypothesis (current working theory) needs reworking. To put that into perspective, 3 sigma has 66,807 "flukes" per million. Not a lot, but it's enough to worry people that your data may not actually be outside of current theory. You can see why 6 is the gold standard.

@@frankn254 I Agree.

All I could think about, frankly.

I am not sure funny defines it but yeah, it was something.

There are as many opinions on the subject as there are physicists. She's just one of them, and she's not always right.

She speaks truth. After Einstein years nothing much is achieved in Physics. All the work is derivative of work done by Einstein and other greats like Schrodinger, Dirac etc.

yep

The standard model isn't just flat out wrong (the observable universe didn't match the predicted model so they invented unfalsifiable dark matter to rectify. Unscientific!) but it is DESIGNED to be wrong. Human physics was subverted 100 years ago and the why was likely to stop us reaching the stars as a species. If youre a budding physicist. Go back and study pre 1927 classical physics and disregard modern falsehoods like the SM.

Well, there's actually nothing to refute in her claims. They're not saying anything in conflict with each other. Standard model predicts, that protons do not decay. And this is actually what we are observing. But there are physicists who don't like some properties of the standard model, so they're trying to create new theories that address those properties of standard model that they don't like. These new theories make predictions such as the fact that protons do decay. This much is said even in this video, even in videos by Sabine Hossenfelder. The only difference is, if this experiment doesn't find the proton decay, these guys will just apply for funding of building an even larger experiment, because the current experiment can only find proton decay if it happens after certain long value, but this experiment (and in fact no experiment) will not rule out the chance that proton decay occurs but it's even more rare. This is called a black swan problem. No matter how many white swans you have seen without ever observing even a one black swan, you can't rule out the existence of a black swan and say all swans are white. Same way, particle physicists cannot rule out, that proton decay might be occurring in ranges they have not yet experimented with. They can only rule out that it occurs in the ranges that they have experimented with. And this is what they could keep doing very hypothetically infinitely long. We didn't detect anything in this range? Doesn't matter, let's look for it at even larger scale. Sabine thinks, this is waste of money and you're not going to find new science this way, because if Standard Model is right and there's really no proton decay, then it doesn't matter how large of an experiment you build, you will never detect any proton decay. So now we have to come back to the question, if standard model doesn't predict proton decay, why do physicists even try to look for it? Because they want to see if their theories, that are addressing some things they don't like about standard model, are correct. But is there actually any good reason to invest money into these new theories? Sabine argues, that no, because these new theories are not really necessary to explain any observation that we have made so far. There are things that the standard model actually can't explain very well, but most physicists are not even trying to address those problems, they instead focus on what kind of numbers they have to plug into equations so that the models make good predictions. In case of standard model, they have to put numbers, that have precision of many decimal places and it's not a simple 1 or a 0. So they are creating mathematical models, where there would be nice round values, which looks better on the paper, but actually doesn't describe any currently observed and unexplained phenomenon. So it's a waste of time and money, argues Sabine. These guys argue, that well, they're looking for something and if they find it, it would be a great shift if physics and if not, no harm done. They don't necessarily agree, that money or time should be the limiting factor on what science experiments will be carried out. We should ideally do all experiments possible, they would probably argue. But of course we have finite resources, so.... But imagine you're a particle physicist and your livelihood depends on being able to perform some experiments, but you have no idea what kind of experiments to perform, because standard model is already covered by experiments and there's no low hanging fruit within the realm of properly addressing issues in the standard model, so it would be hard to get funding for that. You see how these physicists are motivated to keep working on easier problems that will get money.

That would be a great idea, Sabine is incredibly brave to poke the Big Physics bear and Don is someone who could sympathetically argue the inside view in a way that would be comprehensible to the rest of us. These two presenters are giants of making Physics accessible.

interested in this as well. a lot of the 'rules' sound like an awful lot of arbitration, but that just might be the way they name them tbh

My basic understanding comes down to this: Conservation laws are the results of symmetries, as we all know from the very famous Noether's theorem. The theory of strong interactions and it's gauge symmetries are QCD, and QCD of course describes the behavior of quarks and gluons. The equations of QCD are invariant under a global gauge transformation, which gives rise to a conserved quantity. These conserved quantities are simply added degrees of freedom that we assign a name to because we know it is an intrinsic property that is conserved. We assign these names like charm or strangeness or baryon number. In the case of charm and strangeness, these values are conserved in strong interactions (nuclear) but not weak interactions (decay). All of these conserved quantities just give rise to more degrees of freedom, which we call quantum numbers. Other examples of such quantum numbers are mass, electric charge, lepton number, spin, isospin, hypercharge, flavor, parity, helicity, color charge, principle quantum number, magnetic quantum number, total angular momentum, etc etc. Many of these can be broken down into further subcategories. If you ask me, it's a bit confusing and out of hand, but when you take them in one by one they all seem decently well justified. However, I've only got a basic understanding of such things. I am not a nuclear nor particle physicist, just a hobbyist. I hope this helps though. It is worth noting that QCD in particular is quite tricky. The strong force has such a large magnitude that non-perturbative effects may have a major impact on it, so there are many theories that depend on these effects. I've heard of chiral symmetry breaking but unfortunately my knowledge of QCD is pretty limited and I don't understand this enough to explain it. For some more information about this type of thing, look into sphaleron processes. These come from electroweak interactions which have been shown to violate other conserved nuclear quantities, as stated above. Pretty interesting stuff!

When it comes to quarks, there are 2 types of particles. Baryons (which have an odd number of quarks), and Mesons (which have an even number of quarks) (This means that, in general, the Baryon Number of a Baryon is actually [#Quarks - #Antiquarks]/3. So if you had a pentaquark composed of 5 quarks, the baryon number would be 5/3. But for any Meson, which has an even number of quarks, this number is defined to be zero. However, particles with 4-5 or more quarks are exotic particles with extremely short half-lives, so they only show up in particle accelerators. Same thing with single quarks, which we don’t see in nature due to a phenomenon known as color confinement, which arises because of how strong the Strong Force is on small scales. Thus we typically talk about particles containing 2-3 quarks in most scenarios) Anyway, each quark has a spin of +/- 1/2, which leads to why the numerical parity of quarks (even/odd) matters. With an odd number of quarks, you get a half-integer spin (1/2, 3/2, etc…), whereas with an even number of quarks, you get integer spin (0, 1, 2, etc.) As it turns out, this has a huge effect on the way particles behave. You might be familiar with something called the Pauli Exclusion Principle from Chemistry class, which decides how electrons fill the electron orbitals of an atom - each electron takes up a different slot among the possible electron states for that atom. This is precisely because electrons have half-integer spin (they are not composed of quarks, but every fundamental particle will have either integer spin or half-integer spin) Particles with half-integer spin are called Fermions, and follow something called Fermi-Dirac statistics. This is basically a generalization of Pauli’s principle, and it says that 2 Fermions in the same system cannot have the same set of quantum numbers (e.g. with electrons, we have n = 1, 2, 3, …; L = orbital shape = 0, 1, 2, …; m_L = orbital orientation = 0, +/-1, +/-2, …, +/-L; and m_s = spin = +/- 1/2). This tendency for Fermions to “spread out” among all possible quantum states has a huge effect on their observed behavior On the other hand, particles with integer spins are called Bosons. Most of the time we tend to talk about the fundamental Bosons, which are not composed of smaller particles. These are exactly the force-carrying particles in the Standard Model (Photons for Electromagnetism, Gluons for the Strong Force, W and Z Bosons for the Weak Force, and yes… the Higgs Boson, which is how the fundamental particles obtain mass - but it’s not actually a “graviton” for the Gravitational Force, which is outside the standard model) Anyway, we can also talk about composite Bosons as well - anything with an even number of quarks (Meson) will also be a Boson. Ultimately, Bosons follow a completely different set of behavior known as Bose-Einstein statistics. The basic idea is that you can have as many Bosons as you want in the same quantum state, and they are perfectly happy. For instance, this is what allows LASERs (Light Amplification by Stimulated Emission of Radiation - in this case, “radiation” refers to Gamma Radiation, aka Photons) to work. Lasers emit a beam of photons that all have the same exact amount of energy (and therefore the same wavelength), so you obtain an extremely coherent beam of light that is all a single color (unlike a lightbulb in your house, which will actually emit a range of wavelengths across the visible spectrum, but our eyes only see the average color, such as white/yellow/etc. depending on how the bulb is designed) (I believe LASERs operate by what one might call reverse-spectroscopy. Basically, find an atom/molecule that emits a spectral line of the wavelength you want - which occurs via an electron level transition that emits a photon of the required quantum energy - then find a way to make that specific transition happen consistently and repeatedly within a macroscopic amount of that substance) So that’s it. Baryons are Fermions (odd quarks = half-integer spin), whereas Mesons are Bosons (even quarks = integer spin). This gives us some idea at an “intuition” level as to why Baryon Number might be conserved (However, arbitrary Fermions and Bosons are not necessarily conserved. Though it seems like this happens when 2 or more Fermions create a composite Boson - 1/2 + 1/2 = 1 - which would not happen with a possible Proton decay into a smaller particle, for example)

@@Muhahahahaz But was is there to stop let's say... a Proton and a Neutron to change into 3 pions? we have 3 up and 3 down quarks in each system and the second system has less mass.... But the baryon number (which is not a property of fundamental particles) isn't the same.... I also find it fascinating that the standard model predicted the existence of the Higgs Boson to explain how particles obtain mass but as far as I know the other properties of fundamental particles (spin and charge?) are not explained through other particles.

@@Muhahahahaz Technically, a pentaquark would consist of four quarks and one anti-quark; so the baryon number is still 1. With five quarks it wouldn't have been possible for the particle to be color-neutral.

The day has only 24 hours and at some point we need to stop and ask where we should be better be spending our research time and money. Do we just keep on building bigger tanks of water?

@@spaceman4286 The one thing we don't know much about is neutrinos. And Fermilab is not a tank of water. And the other experiments were not designed to specifically look for proton decay. And for neutrinos, yes we are probably going to keep building bigger tanks of 'whatever' because they are the biggest unknown right now.

I don't know about the rest, but concerning point 3) she talked about it. Basically, there is no need to ask for why things are, some things just are and there is no way to really "explain" it, like constants of nature. Knowing why things are the way they are is only useful if it helps make predictions, as long as we can predict with perfect accuracy what a blackbox is doing we don't really need to invest the huge amounts of work and ressources figuring out how that blackbox internally works, if such an explaination even exist. I'm not a physicists, but it really seems like particle physicists are sort of just randomly making theories and then try figuring out how to create the observations that require their theories.

@@JohnDoe-jp4em the vast VAST majority of times people in history have said "some things just are and there is no explaining _why_ they are", 100 years later someone had found the explanation as to why they are. "Oh why do chemicals react the way they do? Idk, they just are! We can describe the patterns pretty well, though, so that's good enough" until oh hey there are these things called electrons and they explain how chemicals interact. Until we figure out all of it, yes _all_ of it, it's worth keeping investigating. And that's a pursuit that will never end, because that's what science is about. Pursuing knowledge and answers. As for "sort of just randomly making theories", they aren't randomly making them, they are looking at existing patterns and asking themselves why this part of physics follows different patterns than this other kind of physics, and asking mathematicians "hey do these patterns ring a bell? Is there any logical relationship between pattern X and pattern Y?" And when mathematicians go "oh actually there is! They're both aspects of a bigger pattern, XYZ", physicists go "okay that's certainly a possibility worth exploring!" and they look for pattern Z and then don't find it, and go "hmm, okay, that was wrong, strange how we get X and Y in the universe but not Z, I wonder why" and so on. That's worked for physicists before, and it's actually exactly how the quark model was discovered, and honestly it's the best way we know of to come up with deeper explanations.

@@ericvilas Without knowing that electrons and orbitals exist you would have an extremely hard time predicting chemical reactions. The only way you could predict something would be to record what happened and did the exact same thing again. Yeah it would be cool if we knew absolutely everything but that's both not possible and an extremely wasteful goal to pursue. It's not worthwile to dumb billions of dollars into experiments that are a shot in the dark whether they will even turn up anything useful or just "guess we need to look harder". Prioritization needs to happen, there is a finite amount of money and workforces available and it's not smart to use a large chunk of it to try to randomly guess theories that are not even required to explain an existing observation. It seems kinda true that particle physics is not really productive when despite access to the most expensive toys in science there are no new major advances in 11 years.

But then it's not really the proton decaying, but the whole atom (atomic nucleus) decaying.

Baryon number is not conserved even in the standard model, it is violated non-perturbatively by an SU(2) Instanton. This process is impossible to practically observe, but it does happen eventually. Only B-L (Baryon minus Lepton number) is preserved in the SM.

Except this video is wrong, his first statement is incorrect, and he should know better.

@@annaclarafenyo8185 Which statement? 🤔

@@annaclarafenyo8185 Are you referring to the 1H segment before the intro? When someone says "You know, hydrogen is all around the Universe since forever!" you don't automatically question "define all H isotopes, all around and Universe". C'mon, even chatbots from 1997 were smarter than this...

"Serius" research? No thanks to the quality of education in your country.

@@johngrey5806 God forbid someone not being an English native! Aliás, aposto que meu latim enferrujado que aprendi há 30 anos é melhor que seu inglês nativo.

Except in this case, Fermilab constructed the "bigger" test setup for a completely different purpose, and is piggybacking the proton decay experiment on to of it. Assuming she approves of the main use of the equipment, this is the type of thing she'd probably approve of. I would like to see Sabine debating her problem with "big science" with someone who disagrees with her, not least because I want to hear what she says we should be doing instead.

@@EnglishMike Yeah, I'm glad DUNE had other purposes and that proton decay _might_ be a side effect they can look for. As far as Sabine is concerned, I treat her like Neal deGrasse Tyson and respect their expertise in their own fields but when they talk about something outside of that I look for experts in the field they are discussing for verification.

The proton in a nucleus undergoing beta decay can take energy from the environment to turn into a heavier neutron. Proton decay refers to spontaneous decay without input of energy.

I'm sure he just simplified the description in the video because that wasn't the main point (and the 3-quark model is pretty much any physicist's first-approximation to describing a proton), but I would love it if he made a video discussing the quark/gluon sea inside of protons and neutrons. PBS spacetime recently made a video discussing this in some detail.

Essentially it would have to decay into something that's not a baryon. I don't believe it happens.

Quantization is a commonly misunderstood concept. (Quantum Physics is one of the many, many, maybe even majority of things in science that is very poorly named.) To the best of our ability to tell, the universe _is_ analog, not quantized. Certain things are quantized, not because the nature of reality is somehow digital or quantum, but because certain things in very specific situations are. For example, a free electron can have any kinetic energy, no quantization needed. An electron _bound in a hydrogen atom_ on the other hand, can only have certain very specific, quantized energy states. It's loosely analogous to a guitar string. Free, on its own, the string can move however it wants. _Mounted on a guitar_ on the other hand, it is constrained at both ends, and can therefore only vibrate at the frequencies dictated by those constraints-by the tuning tension and the current fret it's being held against. Since light is created by the change in energy state of charged particles (mostly electrons), and electrons are mostly bound in atoms (it's a very specific state, but an overwhelmingly common one, heh), it's very _common_ for a given photon to have an energy/wavelength of very specific values... but it's not _necessary._ If you want to know more, especially about the sizes of particles, I'd highly recommend Dr. Sean Carroll's "Big Ideas" series. It's basically a crash course in the whole of what's firmly "known" in fundamental physics that he made during lockdown, covering basically everything we know about how the universe works at a level somewhere in between normal layperson pop-sci communication, and what you'd learn studying it in university. It includes this topic, but I don't know that I'd recommend just watching that one episode, as there's a lot of context you might be missing. _Unfortunately_ this is one of those topics that might be a little _too_ involved for Dr. Lincoln's style of video. I'm not sure if it can be covered in 10-20 minutes... but maybe. He's very good at breaking complex stuff into bite-sized chunks, after all! In short, though, to even begin talking about it, you have to get very specific about what you _mean_ by "size" at that scale. If what you mean is functional, viable assumptions to be able to do theoretical work, then we can pretty safely assume in almost all circumstances that electrons are point particles. If what you mean is what we can actually _measure_ (in principle), then interactions between the method of measurement and the particle become highly non-trivial. Meaning as you narrow in closer and closer to the levels of probing energy that are capable of _resolving_ something as small as an electron, your probe also has enough energy to _change_ it, to create a sea of virtual particles near it that make it "fuzzy" in a sense; not in the sense of the image through a lense that's not focused right being "blurry", rather the electron _itself_ ceases to even _have_ a well-defined "size". Not coincidentally, this uncertainty in its determinable, measurable size fits nice and neatly into what is predicted by the Uncertainty Principle. Actually, in a way, it _is_ sort of like resolving images... though not through a normal lens, by being out of focus, but rather through a telescope, by being at the diffraction limit. We're not _there_ yet, with electrons... but we have placed constraints on their size. IIRC, our current constraint says that electrons can be _no bigger_ than about 10^-18 meters, or an attometer.

Any particle which exists at a point would have unbound momentum.

Light is a 2 dimensional wavelet as it can only oscillate in a single plane & is locked at the speed of light. The size of its existence in a plane is dictated by its wavelength.

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Nothing like spending money to see if a particle decays that has a longer life than the universe so it can't even affect us anyways...

It can, improving the knowledge on particle physics is crucial for better understanding of how matter works, and discovering new ways of using it properties. (We can see it clearly on how our understanding on quantum electrodynamics improved chemistry and semicondutor/computer sciences). Science isn't a waste, it's an investment.

I reckon that such a reaction would be difficult to observe. Because I don't really have a box of anti-neutrons in my backyard. How do you make anti-neutrons anyway? In high-energy nuclear reactions. It follows that the resulting particles will usually propagate at a speed close to the speed of light. Plus, how do you control the movement of particles? With electromagnetic fields. But there's a difficulty that anti-neutrons are electrically neutral (though neutrons - and it follows that also anti-neutrons - are known to have magnetic properties due to being composed of quarks). Finally, what's the average lifetime of a free neutron? Almost 15 minutes (that's nearly an eternity in particle physics). So good luck holding an anti-neutron for a period of a number of minutes without it annihilating with ordinary matter.

Wait, isn't a neutron it's own antiparticle???

@@xochitlpauli5622 It's not. Protons and neutrons consist of quarks; antiprotons and antineutrons consist of antiquarks. (There do exist baryons [as opposed to antibaryons] with charge -1, but they consist of three quarks with charge -1/3 and are unstable. There also exist unstable baryons with charge +2, consisting of three quarks with charge 2/3.)

Yes

@@rodocar2736 Do you have a link to a paper about this observation? Because I tried to search for it, but only found searches for neutron-antineutron oscillations.

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Big.

Why would you want to monitor vacuum? Wouldn't monitoring somewhere with actual protons be more productive?

You need a medium for the decay products to interact with to detect a result. I’m guessing the because of Argon’s atomic density it’s a “bigger” target chance for a decay product to run into and interact with.

Probably because it was mostly designed for studying neutrinos, looking for proton decay is just something it happens to be able to do

Yes, I hear it is even approved by the ADA - The Awesome Don Association.

That requires additional energy.

I suppose its partly a tradeoff certainty-of-find vs chance-of-finding.

@@-dennis3755 yeah. I guess. I still feel like we could and should do better in deciding what experiments to do and which not to do. But Fermilab looks overall promising to me. Let's see.

The likelihood is that it won't find anything. It will only cost a lot of money.

It is no longer considered spontaneous decay. What you describe happens in beta plus decay of atoms, where the proton takes energy from the interaction with the surrounding protons and neutrons.

Did Sabine criticize experiments that attempt to falsify the Standard Model? I thought she criticizes theoretical physicists whose theories are either (1) unfalsifiable or (2) uglified after earlier, more elegant versions were falsified.

@@brothermine2292 kzfaq.info/get/bejne/ottkoKtkrdPbYqM.html

@@brothermine2292 She also talked about things like that I dont remember for sure but maybe exactly on the proton decay problem too. They just move the time it takes for a proton to decay longer and longer in those theories.

@@brothermine2292 She criticized that particle physicists create theories, then create experiments afterwards to create the observations that require that theory. And if the observations don't happen, the theory gets adjusted to require an even larger experiment to falsify. In that way those theories aren't really falsifiable, because scientists spend their time crafting theories that are always outside of the capabilities for falsification. Theories that might be true, but don't predict anything better than other theories and are too expensive and time consuming to falsify are kinda worthless, because you can create an infinite amount of theories like that which are all equally valid.

Not at all - gets me everytime!

He is very funny.

Up quark has a charge of +2/3. Down quark has a charge of -1/3. The W boson has a plus or minus charge. In the case of neutron decay, d (-1/3) -> u(+2/3) + W(-1). The W then decays into and electron and antimatter electron neutrino. The opposite can be true, too. Shove an electron into an up quark and it can become a down quark. That takes energy, which is given by gravity as it squeezes the star.

these questions don't have simple answers. This might partially answer one or two of your questions: kzfaq.info/get/bejne/q5Zlia5h1bnHZ30.html

@@drdon5205 What happens to the charge of the electron?

@@MusicalRaichu I started to read it, and quickly found more questions. A google search for answers produced more questions. I think it will take the rest of my life to understand the answers to my questions, but I'm afraid I may not live that long.

Since electrons have mass their movement can be restricted by gravity, something a neutron star has so much of that it can overcome Electron Degenerate Pressure (electrons not wanting to be in the same place at once) This means multiple electrons can exist in the same place at the same time inside a neutron star. The electrons are still 'there' however they are no longer individually taking up any volume as they do in normal matter. The space a neutron star takes up is just the volume of protons but their charge is being canceled out by a cloud of super positioned electrons. In all honesty it is better to think of a neutron as an exotic atom between a proton and a electron in essentially all scenarios. Quark theory is great and all but its more math than actual physics 🙃

The conservation of baryon number is only approximate. That is, there are situations in which it does not hold. It does not arise from an underlying symmetry following Noether's theorem.

@@michaelsommers2356 The baryon number conservation symmetry is U(1)_V (see www.damtp.cam.ac.uk/user/tong/gaugetheory/gt.pdf, page 244).

@@drdon5205 That's not what I have read elsewhere, such as www.slac.stanford.edu/econf/C1307292/docs/IntensityFrontier/BaryonNo-13.pdf

@@michaelsommers2356 An excellent reference, but the first pages say lots of "If baryon number is an approximate symmetry," suggesting that there is some question. In addition, a (very, very) quick perusal of the paper suggests that it is pointing out that the symmetry could be broken in different theories. In short, isn't the paper trying to motivate extensions of the SM in which baryon conservation is broken? If so, then we'd see baryon number violating decays, which we don't. That said, we do look, essentially to find out if the "If" of this paper is real. This was kind of the point of the video. One thing on which I am sure we would agree is that theorists are clever and can often develop theories which violate symmetries that are incorporated in existing theory. Finding those violations is an excellent way to find clues about new physics.

Because Grand Unified Theories imply that leptons and quarks are connected, meaning that the only true conserved quantity has to be the difference between lepton and baryon number (B-L).

yes! that's called beta plus decay, it happens all the time

Neutrons are stable in a nucleus but unstable by themselves, so in principle it could have a big influence

@@neut9270 Yes and no. It happens in some nuclei, but not all, so far as we've seen. Would it happen in Iron-56, for example?

This confused me too. In PET scanning (positron emission tomography), the positrons come from protons in a radioisotope nucleus emitting a positron (and a neutrino) and turning into a neutron. This is beta+ decay. It was otherwise a great video, but how this situation is different should have been addressed.

@@stevendzik7312 I think they are talking about proton decay wih no external energy input. Beta+ decay requires energy input as the results have more mass.

You can. We do. And they don't. Baryon number is 100%conserved in all observed decays. I believe that is actually the original reason for its introduction. It was observed to be conserved. Though now, as far as I understand, it is based on some symmetry of the model.

That particular class of proton decay requires the hypothetical X boson to allow violation of the baryon number, converting a quark into the positron, which involves no neutrino emission.

@@tonywells6990 sure it doesn't require the hypothetical Y boson. Or Z boson?

@@yzfool6639 Y do you ask?

Well, this particular decay would also violate Lepton Number conservation Leptons are Fermions (“ordinary matter”) that do not interact with the Strong Force (like Quarks do). In other words, Leptons consist of Electrons (and its heavier cousins, the Muon and the Tau/Tauon), as well as the Neutrinos (which come in corresponding Electron, Muon, and Tau flavors - e.g., the Electron Neutrino). This is a total of six particles Each of these particles also has an associated anti-particle: Anti-Electron (aka Positron), Electron Anti-Neutrino, etc. We define Lepton Number = #Leptons - #AntiLeptons. For instance, with Neutron Decay, we have: Neutron --> Proton + Electron + Electron Anti-Neutrino On the left, we have Lepton Number = 0, whereas on the right, we have Lepton Number = 1 - 1 = 0 (the Electron is a Lepton, and the Electron Anti-Neutrino is an Anti-Lepton) Basically, anytime an Electron shows up, you have to have an Anti-Neutrino as well (and if a Positron shows up, there must be a regular Neutrino)

This means that in order to balance your decay equation, we would need to add 3 more particles to the right side: 2 Electron Neutrinos (for the 2 Positrons), as well as 1 Electron Anti-Neutrino (for the Electron) The Neutrinos have an extremely small (but non-zero) mass, so I think you’d still be good on mass/energy conservation. However, I am not a Physicist, so I would have no idea how to explain why this decay does not happen :)

Okay, so I think I found more info… In the Standard Model, we need to conserve both Baryon Number (B) and Lepton Number (L) However, in many Non-Standard Models, if we allow B to break, then Theoretical Physicists have decided that B - L is still most likely conserved. (Though there are other options) So if you lose a Baryon, then you must also lose a (net) Lepton. This requires L to also break, so let’s ignore my previous comment about balancing L for this model In your case, we have B - L = 1 - 0 = 1 for the left side (Proton) On the right, we would have L = 1 - 2 = -1 (one Electron minus two Positrons), which gives B - L = 0 - (-1) = +1 So actually, if we are looking at Non-Standard Models that only conserve B - L, then we don’t need any Neutrinos But ultimately, there are many “correct” ways that a Proton could decay, depending on the theoretical model. Ultimately, Physicists investigate the decay modes that seem most promising based on educated guesses as to what a Nonstandard Theory might look like :)

@@Muhahahahaz I can’t begin to thank you for the detailed information! This is a topic I haven’t heard of or seen anywhere other than here :) I plan to go down a rabbit hole with this topic relatively soon, again I’m not a physicist, just an enthusiast, what we call the “natural” world is just fascinating to how just how unintuitive it actually is. Edit: grammar- I always find something after posting lol

Not any I can find.

It's expected to come out "soon," where soon is kind of unspecified.

A lot. But not an unfathomable amount. IIRC, we only have enough detections at the moment for a 3-sigma result. That means that there's a 99.7% chance that the detections are genuinely of proton decay and a 0.3% chance that we're detecting something else, or random noise. Typically in fundamental physics, we don't consider something "discovered" until it passes the 5-sigma threshold (99.99994% vs 0.00006%). Also, only one facility has made the 3-sigma detections, and a discovery requires that at least two independent projects get to 5-sigma. So... it's a ways off, yet; we'd need at least one more completely independent facility to make at least 5,000 times more detections than the first facility currently boasts, but that's not outside the realm of achievability at all. More, and bigger, facilities are under construction right now to try to do just that. In other words, the detections are promising and intriguing enough to compel people to throw a lot more money at it to find out if it's real or not, where before, only modest amounts of money were thrown at the hypothetical possibility. Essentially, proton decay, today, is pretty much where the Higgs Boson was in 1995. Getting a confirmed result, positive or negative, by sometime in the 2040's, is therefore worth hoping for.

You can look for more information on other neutrino detectors, they all face this same problem of trying to distinguish one event from another.

@@martinklein9489 Yeah, but from what I think it says in the video, proton decay is even more rare. How many do they expect to find in an hour or ... a year? Let's hope the scientist on duty wasn't blinking or having a smoke break when it finally happens.

There is no highest possible temperature. Temperature is just a name for movement we don't keep track of. Absolute zero exists because the state of non-movement exists. Well, the concept exists, anyway; the reality, because of the uncertainty principle, not so much. You can get arbitrarily close to it, and as you do, some very strange and wonderful things start to happen as isolated quantum states become increasingly macroscopic. But there is no upper-limit on movement. Of course, the speed of light is an upper limit on velocity, but because of Special Relativity, it isn't an upper limit on kinetic energy (which we call thermal energy when we are talking about a large number of particles we aren't individually tracking). At a certain point, of course, a particle has _so much_ energy that we think it collapses into a black hole, which corresponds to the Planck Temperature of 10^32 Kelvin, but we don't really have any idea what actually happens at those extremes. The Planck units are just an extrapolation of the units we currently use to describe reality to the points at which our current best theories _about_ that reality obviously and clearly stops being meaningful or sensible... but the chance that our current theory is close enough to true reality for those extrapolations to hold _that_ far away from what we've actually measured and tested, is basically zero.

Since no mass can travel faster than light, & temperature is just a measure of atoms\molecules colliding into each other the limit would be to the equation Vrms = (3RT/M)^(1/2). substitute Vrms for c (speed of light) and fill in the other variables M = molecular mass, R = Ideal Gas constant that should give a basic estimate of max temperature.

@@guytech7310 no, that’s only for ideal gasses. There kind of is a maximum temperature but I don’t want to write a few paragraphs explaining it. I think you can find and explaination on the pbs spacetime channel in the episode about plank units.

@@bathhatingcat8626 My comment was a simple explaination, not an exact answer. Since temperature is related to the velocity of the material, and the max. speed of any particle is c (really less c), there is a max limit to temperature.

@@guytech7310 using T = μ c^2 / 3 R means you’re estimate is off by around 16 orders of magnitude since the true max temperature is about 10^31.

They look for a better model because, even if the current model contains no inconsistencies, it doesn't explain everything. It says nothing about quantum gravity, for instance. It doesn't say what dark matter is.

It's a model. That's the simple answer. It's a simplification of what we can observe. As long as we don't know the full extent to which every known phenomena works we can't be sure of anything. In the same way Newton's theories work, they break down at a certain point.

It's a philosophical question. Sabine Hossenfelder is an instrumentalist; I guess most particle phycisists are realists.

Sabine's take in what Particle Physicists do nowadays is to me the most concise and close to the truth. The field has gotten so big that now it feeds itself, and different thinking is not encouraged: kzfaq.info/get/bejne/ottkoKtkrdPbYqM.html

@@michaelsommers2356 We saw that in large scale GR doesn't work and we assumed that is because we are missing matter but we shouldn't rule out GR is wrong too.

The baryon number in proton proton collisions is strictly positive(+1 for each proton), so you have to produce more baryons than anti-baryons.

@@narfwhals7843 And how is that accomplished? What end products are produced as a result of the collision?

Hello wonderful person!

3) What if there are negative barion numbers?

@@TheBiggreenpig There are -antineutrons and antiprotons for example have negative baryon numbers. This allows pair production and annihilation.

I don't think so. A bigger machine incorporates more events, that's the key. At some point you have considered enough events to make a decision. So far the detectors have not been of a size to make a decision. So bigger than what we have, but only because we have not gone big enough for proof.

@@fps079 Isn't this an ever extensible argument? We can always claim "Well its not big enough that's why", couldn't we?

both super-kamiokande and dune have multiple scientific goals, they are neutrino detectors that can also search for proton decay for the same price

@@fps079 - but there is nothing in our theories saying protons does decay, no is there? First you need an observation that can better be explained by proton decay, than not. Then you check. You don't start postulating that "if protons decay then cool". Its the same as saying "we've not looked for ghosts on the back-side of Jupiter, we should build a billion dollar probe to check". And when it doesn't find it, just say "we've not looked for ghosts on the back-side of Saturn, we should build a multi-billion dollar probe to check".

@@neut9270 - which is fine, as long as the other science is based on something other than hunting for ghosts.