How Does The Nucleus Hold Together?
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- čas přidán 14. 02. 2023
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Two protons next to each other in an atomic nucleus are repelling each other electromagnetically with enough force to lift a medium-sized labradoodle off the ground. Release this energy and you have, well, you have a nuclear explosion. Just as well there's an even stronger force than the electromagnetism holding our nuclei together. But it's not the strong force, as you might have imagined. At least not directly. Nuclei are held together by a quirk of nature, without which we would have no complex atoms, no chemistry, and certainly no labradoodles.
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This channel has 3 types of viewers: the .1% who actually fully understand what he's talking about, the people who maybe don't get it all but are learning from these videos, and the people who have no idea what any of this means but like the sound of Matt's voice and all these long words
4. People trying to fall asleep and use physics videos to to it. (For me it's "fall of civilizations", I'm somewhere between type 1 and type 2.)
Supercalifragilisticexpialidocious
Oh, you forget those people that think they understand the topic, but actually do not.
There's no way 0.1% of people fully understand this.
I am one of the second option: learning ;)
Until today, I never even noticed the distinction between the Strong Force and the Strong Nuclear Force. Thank you for once again teaching me something new.
Ya, I had not known they were different either. I had thought they were simply synonymous
Me too! and it's a really important distinction!
give them better names..
How are they different? I don't get what you're saying. There are only 4 fundamental forces. What you're saying is that there are 6.
@@stevenutter3614 They thought the two names meant the same thing, and didn't know the strong nuclear force is a by-product of the strong force, which is the actual fundamental force
My brain *finally seeing the bed after a 10h shift and a whole lot of extra chores*
Matt's voice; "quantum chromodynamics 😃"
Brain: wait
and then, this: czcams.com/video/FGzfikFU3rg/video.html
At least, for me.
This is the simplest, most digestible explanation I have read or watched to date, and yet I know I am going to need to watch it at least one more time.
Same here! One more thorough watch and I will be all ready and good to go for next week's forgetting! ;-)
I'll watch it through another time, think I remember it properly. Then in a couple of hours I'll realise a bit more of my brain has dribbled out onto the floor.
And just when you got It down, It'll change polarities.
preach it, brother
Nah. One watch is enough. This question bothered me for a while but it all fell into place neatly.
This channel is undoubtably one of the most underrated channels on all of CZcams. The quality, time, and the complexity of the topics along with the added work of delivering the information in a way that the 99% of us baboons are able to grasp these concepts. THIS is the way I wish university was taught and I am always so excited to see a new PBS Space Time video on my feed. Very thankful for PBS, Matt and team for putting together these incredible videos for FREE
Not disagreeing with anything else you're saying, but I hardly think a channel with almost 3 million subscribers can be called underrated.
@@Leyrann I do. With other science channels that can hardly be called factual half the time getting tens of millions of subs and views existing, a channel like this is def underrated.
@@bobmcbobbob1815 It demonstrates how simple-minded the majority of people are. Popularity is not quality.
The the best part of the CZcams-week seeing a new Space Time Upload. I dropped out of physics in College bc the math part (wich is like 85% as a freshman) was too hard for me back then.
With high-quality sources like Space Time I can learn about physics with little math and with fun and awe instead stress. I built my math skills over the years and even give private lessons, but I never went back to studying physics. I will stay a loyal subscriber to Space Time forever I guess 🖖
hello, im an actual baboon.
Did Yukawa eventually get the recognition he deserves? I had not heard of him despite years of reading up on this topic. So much to learn. Sounds like a really bright fella.
Yes! He won the Nobel Prize in Physics in 1949 for predicting the pi meson.
We physics students learn about him precisely as shown in this video, specifically Yukawa's potential
Think about it, Archimedes invented math as it can be applied by humanity, and its most you know he's a greek guy who said eureka in the bathtub
Decent particle physics textbooks always mention Yukawa's potential
@@Dr._K._Sol As now noted in the QA section of the following video, "Are Space And Time Real?", in case you missed that, Fensox. This was the first time I'd heard of him as well. Pretty amazing to accurately predict both the Weak and Strong forces way back then (and outside the "centers of science" of the time).
OMG, the chill I got when I realised that radioactive elements exist simply because the sub atomic particles are far away literally blew my mind. I don't understand this stuff like many of you will but it still blew my mind when I realised that heavy elements are unstable simply because of these virtual particle interactions.
Slight correction, every element has some degree of reactivity with the weak and strong nuclear forces,(radioactivity) it's just that far away subatomic structures have a better chance at reactivity.
second
So... if baryons are like dancers performing in a waltz (not my analogy lol), are unstable nuclides basically where 1 or more dancers are not participating in the waltz and instead awkwardly standing in the corner? lol
I do not believe you. I've seen/read HGTTG (many times), I know you're really hear to observe us humans!
theyre not virtual interactions unless ure an NPC with AI/chatgpt brain
Wow, thank you for this. You're visualization at around 12:00 was the first time I saw a graphical model of the strong force interaction that gelled in my limited mind. This is pretty big for me.
Same. This channel really does the most thorough explanations.
A lot of the time ill be listening and Ill imagine something first and then tab over to look how they visualized it.
Your*
I've heard that the strong force holds the nucleus together, but when I'd look for how, the answer was always "it's complicated". Described like this, it isn't complicated at all!
I agree. Stunning.
@@emmettobrian1874 I love these videos, but what's actually going on is still way more involved than what they show here..
For a decade, I never understood the idea of how an exchange of "a force-carrying particle" kept two particles together.
This video *finally* makes it clear to this non-physicist.
This channel does an incredible job of bringing knowledge to the world. Thank you PBS Space Time!
Animations here are GREAT. I realized a long time ago - well before CG animations were prevalent, that I learn by seeing.
An analogy to the strong nuclear force holding the nucleus together is that it is like the residual electromagnetic Van Der Waals forces that loosely bind electrically neutral molecules together into liquids. Even though molecules are electrically neutral, when they get close enough they can still feel an attraction due to the component electrons and nuclei.
Thank you for answering a question I forgot that I had: "Why is there a size limit to atomic nuclei?"
This video also clarified the Strong Force and Strong Nuclear Force much more for me, thank you!
There's a lot that I like about this episode, but I wasn't satisfied by the explanation for the size limit of the nucleus.
A large nucleus prevents a nucleon from directly interacting with a nucleon on the opposite side of the nucleus, but I don't see why that affects the atom's stability, since the nucleons are indirectly connected by a chain of direct interactions with other nucleons.
To make a chemical analogy: it doesn't matter that an atom at one end of a starch molecule can't directly interact with an atom at the other end, since they're connected by a chain of direct interactions with other atoms. Why doesn't this produce similar stability in nuclei?
@@mvmlego1212
The size limit for atoms comes about due to the strong nuclear force having a finite range while the electromagnetic force has infinite range.
A nucleon can only be attracted to a certain number of other nucleons, after which adding additional nucleons will not increase how strongly the nucleon is held in the nucleus. Every proton is always repelling every other proton, so for every proton added the force pushing the protons apart rises. This continues until the repulsion of the protons overcomes the strong nuclear force and the atom becomes unstable.
@@draenthor4621 And this also explains why heavier elements need more neutrons than protons to be stable.
@@draenthor4621 Thanks for the reply. How does every proton repel every other proton when there are other protons between them?
Imagine three protons arranged linearly, labelled A, B, and C, where B is in the middle. Protons A and B can repel one-another by exchanging force-carrying virtual particles (specifically, photons)--likewise with B and C. On the other hand, A and C have an obstacle in the middle. How can one get close enough to the other to spit out force-carrier?
I’ve always considered a virtual particle like a rogue wave. The sea in general has a relative wave heights. But once in a while, everything aligns to give you a much higher energy value at a localized point. Then, just as quickly as it was created, its energy is returned to the field, or the ocean, in the case of the wave.
I've always thought of 'virtual' particles like a temporary pulled thread in a really really really thick blanket..📜 So it's not a 'new' thread, it is 'borrowing' it's length & size ( or energy) from the already woven/ knitted 'uniform' structure.. So there is only so long / big it can get, before it is yanked back by the strength of the threads in the rest of the blanket..
😁.. ☮️♾️
@@claudiaarjangi4914 Nice image. Like it!
Like sand through a mesh screen. Always a few sand bits that are larger then the semi-perfect holes of the mesh. And just like that another sticks to it because it can’t get in the hole. And another and another. Rough waves.
Like sub nuclear constructive resonance
@@jackodd8284 I thought you were going to say Like sand through the hourglass, So are the days of our lives 😂.. ☮️
Thank you for mentioning scientists that many people don’t know. There are so many amazing and brilliant people in history! I love learning about all the people who have contributed to our knowledge today. 🎉❤
Nuclear Labradoodle is my new band name.
May I play drums?
Love it. Sounds like a punk band, tbh,
Only Baryonic Oscillating Drums
@@thankfuljosh that's sounds like a Danny Carey riff
u haven't met Nuclear Nadal
Space Time just keeps getting weirder and more mind-boggling, and I am so here for it.
That's what happens when you delve into modern physics. 😁
I love the history of physics, especially when you give credit to all the amazing people that might have been overlooked in the past. Great channel.
The greatest part of these videos is going down into the comments, explaining some question another viewer had and through that getting to *actually* understand what you just explained to them, too. Especially because other people come up with analogies you never would've thought of.
I didn't properly think about the strong force acting on ALL quarks before I put it in terms of "stealing a ball from another person and both of you are on boats".
This guy feels like your cool uncle that noticed you're by yourself in the corner reading science books at the family gathering, and comes sit with you to talk about his new special interest and get excited with you over quasars and atoms. I like him
"Discovered by the British" is also wrong. Although Cecil Powell received the recognition for the discovery, it was the Italian physicist Giuseppe Occhialini and his Brazilian student, Cesar Lattes, who designed and conducted the experiment that detected the pions. They just happened to be working under Powell, who of course financed everything.
As a Brazilian, I'm glad to see someone quoting Cesar Lattes
You, sir, are exceedingly ill informed. Education will help.
@cartoonvandal You're right, education does help. That's why I suggest you check the references after the first reading:
en.m.wikipedia.org/wiki/C%C3%A9sar_Lattes
This quote is a translation from scientific historian (R. A. Martins)
"Although he was the main researcher and the first author of the historical Nature article describing the pion, Cecil Powell alone was awarded the Nobel Prize for Physics in 1950 for "his development of the photographic method of studying nuclear processes and his discoveries regarding mesons made with this method". The reason for this apparent neglect is that the Nobel Committee policy until 1960 was to give the award to the research group head, only."
Who is today's Hideki Yukawa?
What is hiding in lonely research publications that is unappreciated today, and will prove to have been prescient in the future?
Always keep your mind open to new ideas.
Great production as always. Thanks!
Well if we could answer that then it would stop being an answer wouldn't it?
@@farfa2937 Bro it was a rhetorical question
Your point makes me think that there is room for Space Time to devote an episode to the unsung heroes of science... I am sad to see the Europeans getting acclaim more than those like the Japanese man revealed today as so very significant in the evolution of our thought.
@@Video2Webb The Yukawa potential is used all time. He is well known to all nuclear and particle physicists. and he has a Nobel Prize.
@@DrDeuteron Thank you for that information. I got the impression he had been passed by. Not published when he should have been. Glad to hear that he got recognized including by Nobel Prize judges.
Yukawa was a man ahead of his time, a true genius. Japan is following this strong tradition in low energy nuclear physics
I'm so happy to finally understand the basics of what mesons, boson, and even virtual particles! You made me realize why we went on the quest to discover quarks, and I can't wait to share this knowledge with my kids. One of your best episodes!!
Very serendipitous that you would post this the night before my Nuclear & Particle Physics exam! I had this exact question, plus you allowed me to take a break from revising while also being productive :)
Do well in the exam mate, we need you!
Best of luck to you on your exam! Hope you knock it out the ballpark!
Wait...so you took a mental break from studying for your N&P Physics exam, by watching a video with a N&P perspective? I predict with low Heisenberg Uncertainty that you are going to well at...pretty much whatever you set that mind of yours to.
@@ronjon7942 Haha, don't let my post deceive you, I'm pulling an all-nighter because my studying has been lackluster, and I've been on a break from Uni for a few years, so I'm trying to come back and finish my degree now! I have ADHD and despite (or because of?) the stimulants I am constantly at risk of getting derailed for hours at a time on random tangents, so this video helped me *not* do that, while also taking a break. I did end up getting a little derailed still, but I'm getting back on track, hopefully everything goes well :)
@capt.picard445 @R.T.and.J Thanks a lot! You're actually brightening my rather bleak all-nighter :)
give this guys a raise the designers are amazing kiss
Yes, more kissing on spacetime
The nucleus bonds together with a lot of fun activities like 'Beer Pong' , 'Darts' and the board game 'Who's uncertain now?'
And the nucleus becomes unstable every karaoke night.
@@Moon_Metty Karoke !!!
One of the few Space Time videos I could follow all the way through lol. The basics are communicated very well, well done.
Incredible episode. The fact I was able to understand any of this really says a lot about how well you explain it! Thanks for everything you do.
It becomes SOOO much more intuitive to visualize these events as waves. I just wish there was a way to animate waves that showed it
100% agree. I wish all of physics would move that way. The word "particle" is itself very misleading. Quantum particles are discrete and quantized, but so is a dog. There's nothing especially particle-like about them.
Actually, I have a new Theory that should explain the Strong Force, Weak Force and Entanglement. All starting with Waves. The question really becomes how to make waves stand still. All waves by definition move at Mach 1, while a Particle constructed from Waves move at less than Mach 1.
Well, I can only imagine there's a methodology to learning about this, just like in school we're introduced to the particle models one degree of complexity at a time. First you have atoms as these tiny balls that organize into molecules. Then you expand to the atom being made of a nucleus and an electrosphere populated by electrons. Then you add the concept of nuclear mass, the existence of neutrons, electron energy levels. One more degree and we get to the make-up of subatomic particles, and by that time the topic of wave functions and initial quantum physics are easier to digest because you're familiar with how the model is supposed to work
You don't need quantum chromodynamics to explain all the phenomena that we see, so there's no need to introduce such terms if you're not going to use them
@@WeBeGood06
Light is a wave.
@@WeBeGood06 The phenomena you're looking for is known as a soliton.
Between Matt and Sabine, I've learned enough about the quantum world to know I've learned next to nothing about the quantum world. I know just enough to be totally fascinated!
❤️❤️
eugene khutoryanski has a video that fully explains the strong force with animaitons
Biochemist here - my partner studied mathematics and economics in college so she doesn't understand what Matt is saying but she loves to use his videos to sleep because she says his voice is soothing. I don't understand all of the particle physics he discusses, but I learn about it pretty quickly given my background. Thank you, Matt. 🙂
Your presentations sometimes have me finishing some episodes with headaches but I always come back for more. No one explains things with the clarity you have routinely accomplished and I thank you for that.
Even though I never fully understand these videos, something about them is extremely relaxing
Why doesn’t a meson annihilate given it’s made of a quark/anti-quark pair? Is this different to matter/anti-matter annihilation somehow?
like an onium, onium is electron-positron pair that orbit each other before crashing. Even though it may seem annihilation is instantaneous but at sub-atomic scale 10^-12 second is quite a long duration for a thing to happen
Indeed, they are very short-lived. pi^0 is one of the shorter at ~10^-17 s half-life. Note that antimatter annihilation itself isn't instantaneous: an electron and positron for example "orbit" each other like a lightweight hydrogen atom; as the orbit decays, their wave functions, and therefore probability of annihilation, increase.
But wouldn’t annihilation photos be produced and able to be detected if this was actually happening?
@@ephraimparent5550 because the recombination of meson is faster than self annihilation, it can not be observe naturally. But some unstable nuclear in excited state can release gamma radiation, you can guess where it from right ?
@@ephraimparent5550 In this case the meson still owes an 'energy debt' from its creation. It is not a 'real' meson, but a virtual particle. The gamma rays produced are also virtual, they will be re-absorbed by the nucleus to leave the total energy change at zero, except under special circumstances.
I’m an Indian. Never heard of Bibs Chowdhuri & Debendra Mohan bose. Thanks for highlighting these unsung hero’s works.
I love that you take the time to research and mention people who weren't originally recognized for their discoveries.
this is possibly the best explanation of mesons and the binding mechanism at the nucleus
A great video and exactly what I want to see. More in-depth videos along these lines are a great way to go!
I am still confused. He says that during the meson exchange, energy and momentum exchange occurs which keeps hadrons binding together. How this happens?
@@ibrarkhan9878 Maybe it's like if i throw a boomerang & it starts returning & you catch it & the momentum pushes you towards me?
@@alwaysdisputin9930 It also makes sense.
The link between the short range of the strong force and the uncertainty principle was my biggest takeaway from this episode. Not sure if I'd never heard this before or if it just never clicked
Definitely. I always ever only heard that the strong force is just way stronger but falls off way faster, but with this explanation it just makes sense WHY.
it's actually a totally dated way to look at it, that went out of favor with Feynman Diagrams in 1948, (where nothing gets borrowed from nobody). While it works mathematically, the calculations took months to years, while Feynman diagrams took minutes, even seconds since some processes just required swapping letter s t to compute what was once considered a totally different process.
@@DrDeuteron there are virtual particles in Feynman Diagrams, so something is getting borrowed from somebody (this made me laugh out loud thank you!) and it makes sense intuitively to think that the higher the energy of the virtual particle, the shorter lived it will be, which results in a shorter range. If this isn't the right way to see it, I'll have to wait for a clearer picture but for now I really like this
@@DrDeuteron also how do Feynman Diagrams explain why the strong force is short range?
@@seionne85 they don't, and they don't work well in QCD since you need a gazillion of them, while in a meson-exchange theory they'll eventually yield infinity. Color confinement is an experimental observation.
It is clearer than other explanations from other videos or channel, great work !!!
I cannot put to words how much I appreciate these videos!! I always learn something new in a very enjoyable way. Kudos as always.
There is so much complexity down at the lowest levels of existence. Mind boggling. Thanks for the great video as always.
This was so dense! but yet amazingly well explained!
my favorite part of all these videos is how you tie in the word spacetime at the end. Always a higlight and lil chuckle. keep up the good work.
YES! I love when you guys do low level particle/quantum physics stuff so much. This is the only place where i actually feel like i understand the high level concepts surrounding these topics, your script writing is absolutely amazing :D
It is! Still I would have to watch more than once. If only YT enabled Creators to post their transcripts - accurate ones I mean. The CC thing is poor and hardly worth struggling with.
Incredible to realize how complex and deep the structure of our world when zoomed in, not only out
INSUFFICIENT DATA FOR MEANINGFUL ANSWER
As an Indian , I really appreciate all the indian scientists you have mentioned about.otherwise I would have never come to know about them. Thank you for spreading scientific knowledge. Tbh whenever I study chemistry I always have doubt about this particles and theories.
Even more advanced graphics during the very first seconds! Delicious. Thanks for great substance, as always! Greetings from Finland.
Can we have a moment of appreciation for how well these videos are produced - especially how good they sound? The sound design and mixing is perfect! Matt's pleasant voice helps a lot, but the sounds in the video are always balanced and never extraneous.
Thank you for such a clear explanation of the difference between the "strong force" and "strong nuclear force". I see this glossed over all of the time, or even mixed up. In any given instance, being a layperson on the matter, I sometimes struggle to know if I am seeing someone's oversight or error, or if my own understanding is flawed. This cleared up a lot.
Simple explanations usually only serve to confuse me. I need to get down and dirty with the math and, generally love doing so, in order to gain insights and/or understand how it all works. However, you explain these concepts so well that even without diving deeply into the math, I have lightbulb moments, or rather, I gain new insights that leave me with a better understanding and an excitement to learn more. As always, thank you for this excellent video and channel.
Thank you. It's a great and simple explanation of the strong force. People usually explain only the very surface of this force for some reason.
Mind blowing stuff. Easily one of my favorite episodes! I've wondered about this stuff for so long but I could never find a clear and understandable answer.
Really good video! Often, when people (textbooks) tell this story, it starts with Yukawa‘s mesons and then goes on to gluons and QCD etc. but never really gets back to what this all has to do with the original meson idea.
I read the book from Gerard 't Hoofd, nobel prize winner on this subject, but I didn't get much out of it. This video was immensely good at explaining mesons.
maybe it was the combbination of botth
my brain cant even process half information of this video but somehow i watch it to the end. Matt's style of explained things has just got me too good.
Neat! Usually, these particle physics videos go way over my head, and I don't feel like I get much out of them. This time, though, I don't know what it was, but by the end of this video, something clicked in my brain and (I think) I actually started to understand this stuff. I'll never be fluent in particle physics, but at least I've got a few key phrases in my vocabulary now. Well done!
A beautifully communicated overview, thank you! I think a nice detail to add is that baryons (and ultimately all hadrons) are far less orderly than we show them to be in diagrams. They are much more a quantum mess where there can be quark-antiquark pairs popping in and out in various configurations, and once two baryons are close these have a chance to "hop" between them without violation. A nice source of intuition is comparing the effective size of nucleons to their mean separation in a typical nucleus, which are both about 1-2 fm, i.e. nucleons in the nuclei of atoms are very close to each other relative to their size, so these tunneling effects make sense.
Do you have any extra details on the tugging explained between quarks of neighboring baryons at 11:50? Right now it feels like the causality of the situation is presented as there being some interaction between the quarks before the pion exchange, when the only substantial interaction they can feel from an outside baryon should be the pion exchange itself, dictated by the proximity of the nucleons and the soup of virtual mesons popping in and out. Any Coulomb interaction seems too minuscule to possibly count as the tug (~100 N disregarding shielding effects from oppositely charged quarks nearby vs. ~10000 N strong force at ~1 fm scale.)
Valentine's Day reminded me that you can remain in close proximity of something that repels you... for years, even... so long as the mortgage agreement is strong enough that neither of you can escape it unscathed.
More and more it feels, to me at least, that emergence is the most crucial concept to understanding the foundations of all science. It's insane how many emergent properties are derived from the most fundamental building blocks of all reality.
everything is an approximation
12:48 - 13:11 this alone blew my mind. It makes so much sense!
Nothing more attractive than a bit of Space Time!
I am so happy to see you do a video on this! Just the other week I was thinking I should message you guys to suggest this as a topic, because I thought it was odd you never covered in before, and I'm glad to see you guys thought the same thing.
11:10 and forward will cement itself in my brain forever, what a brilliant description and visual.
Thank you for helping people to discover our reality anew on a completely elementar levels! I feel astound every time finding out something new. You guys make the clearest channel in understaning of your scientific subject throughout all other channels I have found on youtube so far !
That whole meson exchange thing was beautifully illustrated. When that exchange occurs, are the two adjoining nucleons then entangled?
yes, but entangled how? Spin, orbit? no it's worse: nucleon don't even exist as protons or neutrons in a nucleus, they're a mixture of both.
I wonder/ed the samething. But I also wonder if being that the exchange happens via a virtual particle exchange would it break the entanglement? I have limited knowledge on all this so I don't even know if virtual particles can be entangled with how briefly they exist ect.
Thanks for this very interesting topic!
I was surprised that Japan had a physicist thinking of these problems. As per checking, they did have lots of physicists and even had a nuclear program during ww2.
Wow! This is the best video explaining the strong force. Fun fact. The planet killing weapon in the Enders game series “the little doctor” operates by dissolving the strong force of atoms so anything it touches just dissolves at the atomic level.
11:43 how does it feel a tug before the particles have been exchanged?
In this case there IS an exchange beforehand, virtual gluons have some, weak effect, enough to start things off. It allows the far stronger meson-interaction to take place.
It would be fun to see a video on what the universe would look like if this force had a slightly longer range and more massive atoms were able to form naturally.
Excellent explanation, especially of how the strong force works, thank you!
I still struggle to understand virtual particles terribly well, but thank you guys very much for these videos that put them into terms I can mentally engage with. I would very much enjoy more videos on QCD, the strong force, and virtual particles.
God be with you out there everybody! ✝️ :)
To learn virtual particles, learn second order perturbation theory in quantum mechanics, the second approximation to describing the energy levels of an atom. The calculation involves transitions to a virtual state, then back. This is exactly the same as quantum virtual particles, the virtual particles are just the virtual states in perturbation theory for a quantum field.
virtural particles have never been the input or output of any experiment.
@@toymaker3474 Every particle that is input to an experiment or taken out is virtual. Only if it escapes to infinity is it not virtual.
@@annaclarafenyo8185 so your saying all "particles" are virtural? because their is nothing special about particles used in experiments. i dont belive in particles because in reality we are dealing with fields buts that besides the nonsense of virtural particles.
@@toymaker3474 Both statements "all particles are virtual" and "all particles are real" have a grain of truth and a grain of falsehood. A particle that is emitted and absorbed is virtual, because it didn't get to infinity. Same thing if it hits something (like your eye) and scatters. So, since you aren't infinite in size and infinitely far away, when you observe something it's "virtual". But since you are practically infinite, it is also correct to say it's "real" (as an approximation). To be actually real, it has to reach infinity, and this assumes infinity is a flat spacetime. Our infinity has a cosmological horizon, so it gets murky.
In holographic AdS/CFT, you can also say "all particles are real", because the actual physics takes place at infinity on a holographic screen. This means that the virtual observations you make at finite distances are shadows of 'real' observations at infinity, but these are smeared out all over the holographic surface.
So both statements have some truth, it's hard to do physics without embracing logical positivism, and realizing that many statements are approximations, whose negation is also valid in another approximation.
When the meson is exchanged between proton and neutron, in my mind I still have the picture of two people sitting in two boats, throwing a heavy ball to each other and thus drifting away from each other. Can you maybe go into more detail how the exchange of a massive object can draw two objects together?
The exchange happens via attraction to each other, nothing is really being shot at one to the other. One releases the meson and the other attracts and "absorbs" it, this wouldn't be possible if it wasn't being paired in the moment I guess.
Two people throwing heavy balls to each other are not attracting anything to each other, they are not paired. Rather they are using action (throwing the ball) at the cost of reaction (drifting away from each other).
Because the meson is not being thrown, it's pulled over by the strong force.
Basically, one particle pulls on a quark of the other one, going so far as ripping that quark out. But because the strong force ALSO keeps the now damaged particle together MORE strongly, that ripping out can only happen when there is already a pair of quark+anti-quark ready to repair that rip and leave the damaged particle undamaged. And the anti-quark goes along with the ripped out quark, reaches the other particle and destroys the appropriate quark there.
In terms of a ball and two boats, unlike a ball being thrown this is more alike to pulling on a ball, the original owner pulls back on the ball so hard they rip another ball straight out of nothing, then the un-ball created by that insanity and the ball are pulled over to the other boat and the un-ball deletes the ball that was on that boat. Everbody still has exactly one ball, but inbetween there was a whole lot of pulling.
Arvin Ash on his channel illustrated this by people throwing boomerangs outward and they arrive inward on a curved path.
that's just a shortfall of the analogy, esp. in the "borrowed energy from time" version, which is passé. In the modern (post 1948),view virtual particle can what ever mass (include complex numbers) required to make it work...that means you can't even time order emission and absorption.
if i recall the quantum chromo dynamics video correctly the quarks held together by the strong force in groups of three.
it can be illustrated as a triangle of 3 balls connected by springs; the farther you pull one of the balls (quarks) away from the other two, the stronger the spring (gluons) pull back.
If you pull far enough the spring will naturally snap. BUT here's the catch: the amount of energy required to snap our gluon springs.........is the amount of energy required to create a meson, a pion.
so tldr: it is like two sets of 3 balls connected by springs on two boats. the balls from one boat pulls on the balls on the other boat to such a degree that it rips one of the balls loose.....which such a force that it spontanously creates a matter-antimatter pair! and the pulling starts again......
before the springs snap the boat drift closer together, then it snaps and they drift slightly apart before pulling on each other again.
Such an amazing and enlighting presentation from Matt
Excellent video. I finally got some questions answered that were foggy in my perception.
I feel bad for Yukawa’s hardships, but also inspired on how he kept pushing forward with his theory.
I’m left only with one question:
If we take the strong nuclear force as a quasi-force, would that make the weak nuclear force a “full” force? or what would be for that? also considering that the weak force uses more or less the same particles to interact.
A while ago I read Feynman’s book “QED”, and the brief introduction to QCD in the final chapter left me with a lot of questions (many of which this video addressed).
I’m curious, what would be the Feynman diagrams representing the high-amplitude interactions within a simple atom, say deuterium (or just the nucleus)? Is there something about the amplitudes of photon vs. gluon interactions between quarks that makes the nucleus stable?
yes: alpha_s = 1, while QED's alpha ~ 1/137.
Thanks for posting videos for the layfolk like me on these complicated and fascinating physics.
Huge respect for giving credit to physicists that are seldom mentioned.
Is there a known frequency that this exchange would occur at? They must be exchanging particles all the time in order to be bound together.
the lone (stable) nucleus is in a stationary state: nothing changes, ever. You can't take these analogies too...classically.
That may involve finding the Fourier transform of the universe... 🤔
@DrDeuteron I hold the opposite opinion, the lone stable nucleus is never static, it's a phenomenon. I would say the static interpretation is an approximation of the effect of this phenomenon disregarding the time axis.
Nuclear or particle interactions are on the order of 10^-12 to 10^-20 s or something like that, so a corresponding effective virtual particle rate would be reciprocal, give or take a constant term relating to the probability of production, the overall strength of the effect. It's not a meaningful measure of course; we can only ever observe statistical samplings of the process (as with bombardment with extremely fast and small particles, like ultrarelativistic electrons or other leptons), or the overall time-averaged result.
@@DrDeuteron could you elaborate?
Wait. (11:45) How does the quark get pulled towards the other in the first place? Doesn't the initial attraction of quark A to quark B need to be mediated by a particle? This feels like a chicken and egg problem.
exactly what i was wondering - hopefully someone can clear this up
My interpretation would be that this is a drastic simplification of the interaction, it's more likely that pions are being constantly generated through fluctuations in the fields, then annihilating back into the baryon, when two baryons are close enough these randomly generated pions can be interacted with via the strong force as doing so no longer violates charge neutrality (admittedly atm I can't explain how, however my suspicion would be that the pion introduces enough dof that gluons can be exchanged without destabilizing the baryons).
@@xxportalxx. That's also what I was guessing *could* be the case... but I hope Matt answers the question cuz I'd really like to know for sure.
@DrakiniteOfficial I mean the less (or maybe more?) interesting answer could be that this is just a model that goes along with some math that allows us to accurately describe these interactions, but has very little physical relevance. I.e. the interaction may be some amorphous complex wave interaction, which just so happens to be well modeled as this kind of 'particle exchange,' while these particles never exist as stand-alone objects being exchanged in reality (and therefore there could be fundamental conceptual holes in the model). Note: I am not saying the particles don't exist, just that they might not exist in the interaction.
There IS a gluon-based effect, but by itself it's too weak to do anything. Fortunately it can trigger a more powerful effect, meson exchange. It's something that's difficult to explain without simplification like this.
My wife and I replayed medium sized Labradoodle off the ground about 10x.. laughing so hard I nearly died.
We should change a basic measuring force in number of medium sized Labradoodles, being lifted off the ground
Thank you. ive been searching for this answer. This tied up a lot of loose ends.
Truly appreciate the historical context and physics history lessons woven in with the message.
One of the things that got me confused was the nuclear force isn't inverse square law since after electricity and gravity worked that way, I thought that others would be similar.
One of the densest video of this channel yet, I need to rewatch multiple times now.
Another really interesting video. Stuff gets real complicated, cool to learn about
One possibly related question that always intrigued me. Free neutrons have a half life of about 15 minutes, but they can be indefinitely stable in atomic nuclei. Why is that?
Certainly wait for someone more educated than me to give a proper answer because I am at the edges of my understanding, but the key is weirdly just that the down quark has more intrinsic mass than the up quark. Neutrons are of course 1 up, 2 down and Protons are 1 down, 2 up, and so the neutron is just very sliiiiightly heavier than the proton, that difference being overwhelmed in totality when you include the binding energy to make them "equal" as composite particles. Higher mass means a higher energy state, and we know what happens when there are two states and a way to go between them, the universe wants to get to the lower energy state. So in this sense, neutrons are fundamentally unstable.
The only thing stopping neutrons from just all spontaneously decaying to protons is that the decay path involves a down quark turning into an up quark and emitting a W- boson...which is a REALLY massive particle, it's about 80 times the mass of an ENTIRE proton. Since you generally can't just produce that amount of energy from nowhere, it means the neutron is at least meta-stable. It's not at it's lowest energy state technically, but there is a "wall" of much higher energy needed before you can get to that lower energy state.
So...neutrons shouldn't decay? Yes...ish. Enter quantum tunneling. I won't explain it since I think most people here are familiar, but suffice to say that there is a very very small chance for the interaction to just bypass that required energy barrier and appear on the other side, in effect pulling the energy out of nowhere to create the W- boson for a fraction of a fraction of a second and have it decay, creating that electron we all know and love in beta decay and leaving behind a brand-new bouncing baby proton.
So why don't neutrons decay within the nucleus? I think it's as simple as "The state of the atom with an extra proton is higher energy than the state of the atom with the neutron as is". There is still that energy barrier in place, but on the other side is a higher energy state, not a lower one. And thus there is no "incentive" for that interaction to happen. It's higher energy because protons are charged and thus add electromagnetic potential to the atom. And obviously beta decay of atoms still exists, so there are some atom configurations where this isn't true and we DO see neutrons decaying to protons in those cases.
Take everything I said with a grain of salt though since I am not a physicist and just a lay fan of physics.
The first reply here is a wonderfully technical explanation and quite correct. More generally, things change STATES. One 'thing' such as a neutron, can be in many STATES and they are not equal.
A ball, by itself, does not fall. Leave it out in space and it does nothing, it is stable. A *ball in the air above Earth* IS unstable and will fall. The two states are similar, both are balls, but are also different. And the ball above Earth can do many things, it can fall onto the top of a hill, or it can fall into a deep valley. The ball on the hill can further fall into the valley, but the ball in the valley cannot fall onto the hill.
A free neutron is a neutron in a high-energy state. It can 'fall' into being a proton, but can also fall (literally) into a nucleus, which is lie a deeper valley. Once inside the nucleus it's too 'deep' to fall into being a proton.
Some nuclei are 'higher than the proton state and these will beta decay. Some are 'deep' enough that an electron can fall in, merge with a proton, and form a neutron. ('electron capture'). It all depends which neutron STATE is lower energy.
question: how come the quark/antiquark pair in the meson don't annihilate?
I guess they don't have time to annihilate in that interaction?
They do, after a few nanoseconds. It's long enough to do their job in the nucleus.
E: It only works for the pi0 (u anti-u + d anti-d), which can indeed decay into photons. Pi+ and pi- decay through the weak force and live longer (nanoseconds instead of attoseconds)
good observation.
@@basseenergie ah, i see. thank you!
They don't annihilate because they are different types of quarks. For example u and anti-d in the case of a pion.
I love Matt and PBS SpaceTime. I actually can comprehend what is being explained, usually in one watching, two if I have distractions around me. I love Physics, Astro and Particle, and find both fascinating and somehow, they make sense. Might be my weird brain; I am Autistic, and I see everything from a whole different perspective than most people do, and these sciences are just like me, a very different perspective from the mundane daily [so-called] reality.
This video rly helped me finally understand chromodynamics and mesons thank you spacetime ! You have made me smarter
Forgive me for not initially mentioning Bibha Chowdhuri and Debendra Mohan Bose along with Hideki Yukawa.
It's amazing to me that twice this research went all but unnoticed.
I am very grateful that we now know the story of their discoveries.
This will have been true throughout the evolution of "life". Discoveries and advances being made ahead of their time, being useless/counter-productive/ridiculed until necessary supporting progress being made for those advancements to find their place in the lineage.
It's one of the worst aspects of "free-market economics", that if something has no value in-the-moment, it has no value.
it's less amazing when you consider that the people involved were all non-white :-/
Wow! Phenomenal! Really great explanation of how baryons and mesons come from quarks, and how the colour/strong force works on nuclear scales. I've never had any intuition as to the strong force, and the explanation of why it is so short range is really interesting as well!
I wonder, since the Meson's mass limits the range of the strong nuclear force, and the photon's lack of mass lets electromagnetism work over large distances, does that mean the graviton, if it exists, must be massless?
It does. ANY infinite range force must have a massless carrier, conversely any limited rang force is either bound (Like gluons) or has a massive particle that determines its range. You can tell almost everything about a force's particle based on how the force acts.
Makes you wonder just how many physicists (and academic papers) are out there who’ve made significant discoveries/contributions to the field without ever being acknowledged or even known
Much better than the last few episodes, well done.
My favorite bit of technobabble from Star Trek is the Heisenberg Compensator in the transporters. It compensates for that pesky uncertainty principle to allow macro transportation.
I am the one who transports
What annoys me is that it's not actually needed, at least not in the way people think.
Great video, as always!
But I don't agree that "the quark is pulled out of the nucleon" and that creates a pair of quark-antiquark 🤔. For a quark to be "pulled" they'd have to exchange a gluon, which is exactly what you said it couldn't happen. I believe a better way of saying it is that the pair is created inside the nucleus and that is what make the meson in the first place. Of course, these are all virtual processes so the temporal order doesn't actually play any role.
EDIT - Another way of explaining it is by a parallel to superconductivity.
Finally an intuitive explanation for the nuclear decay despite having the strongest fundamental force between them. Thank you Matt 😌😌😌
Thanks for this explanation!
I knew this mechanism earlier but without all the details. Thank you for more detailed explanation. I always wonder why fermions always create matter and bosons carry force. It aplays not only to fundamental particles of standard model but also complex ones like hadrons --- 2 quarks gives meson that is boson and it behaves as force carrier; 3 gives fermion that builds all matter. Or is it just coincidence? It won't apply to heavier things. As some nucleus are bosons but they are diffidently matter.
definitely matter