Hank continues our series on the four fundamental forces of physics by describing the weak interaction, which operates at an infinitesimally small scale to cause particle decay.
Watch the video on Strong Interaction: http://www.youtube.com/watch?v=Yv3EMq2Dgq8
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The weak force is not weak due to interaction distance, but due to the mass of the force carriers. For an introductory explanation by a man sporting a bad mustach, see https://www.youtube.com/watch?v=yOiABZM7wTU (Just after 8 min)
of course all this is only a observation of what happens when you add energy to a group of partials in an atomic accelerator and collided them , so its only the extemporaneous forces of the collusion they managed to capture and name according to the movement of a track left in a medium which is presumed to be but may not actually represent the fundamental forces which are repulsion and attraction a derivation of temperature and function of the excited state of a string which in compensating to the excitation internal bifurcates giving rise to wave functions which allowed through the action of that function balance in the creation of compensatory photon mass at varying levels of excitement,,,,,,flavors ???some one be on the hooker to long
I don't get how this is a force. Ok, it changes the identity of the particles involved in the process. Soo, shouldn't it be considered a reaction instead of a force? I mean if it is a force it should accelerate a particle, or (together with other forces) put it at a rest state, right? Before this video I used to think this was the force which prevents the electrons to collapse into the atom core by electromagnetic attraction
Hi Hank, thank you for making this wonderful video. If and when we can make particle detectors that are "quantum-ly fast" or sensitive enough to inspect the transformations of protons into neutrons and large mass quarks' transformation into down quarks, do you think we might observe other "ghost" particles, force carriers, or perhaps other unidentified subatomic elements we haven't observed yet? I ask this since quantum computing may be able to help us observe the sub-atomic world better in the near future and was wondering if you in academia-world heard of anything in the works. Thank you for your time! You have a new subscriber!
I understand that it is the Pauli exclusion principle "force" that supports a white dwarf star. That is, the electrons don't want to occupy the same quantum state and so resist the collapse of the white dwarf. So this appears to be a force that opposes gravity and prevents a white dwarf from collapsing. But which of the four forces is this?
Hank seems to have misinterpreted a Feynman Diagram of beta- decay, where the anti-neutrino's arrow is drawn in the opposite direction (as is convention for antiparticles). The weak decay happens spontaneously (without a coincidental neutrino) and a W- boson is emitted, which quickly decays into an electron and an electron anti-neutrino.
Wait - if the up quark has a poitive electrical charge, and the down quark has a negative electrical charge, and neutrons consist of one up and two down - then shouldn't the neutron be negativly charged!?
What If there are 2 up quarks and 1 down quark and the W boson interacts with the 1 down quark via the weak force? Would that mean all the quarks would face up? If so, what does this mean for the neutron/proton?
Extra: to make plutonium is as easy as hiting natural ocurring uranium (U-238) with a neutron, creates U-239 wich, as shown in this video, transforms 2 protons to 2 neutrons making plutonium-239, the one used in nuclear bombs. To get neutrons is as easy as, when an alpha particle hit beryllium or alluminium gives a neutron, so you encapsulate the uranium in a neutron reflector box (like tungsten carbide), put beryllium in wait and get it out, and chemically separate the plutonium, start the proces again. Warning, do not exposure too long or Pu-240 will be produced, wich is bad because it can fissile automaticly, starting a chain reaction.
Well, no; the video is misleading on this part. A radioactive nucleus spontaneously emits a W- boson, which then decays into an electron and an anti-neutrino; this is the beta- decay. In case of beta+ decay, it instead emits a W+ boson, which decays into a positron and a neutrino.
The Z boson is a heavy counterpart of the photon; in particular, it is its own antiparticle. It is involved in "neutral current" interactions which don't change the identity of the involved particles (but makes the particles exchange kinetic energy and momentum), such as scattering of neutrinos by matter.
Wait, so you have a neutrino VERY close to a neutron, which then becomes a proton and an electron after the exchange of W+. But proton being positively charged and have significant mass, and our electron being negatively charged, at that close distance wouldn't the electron be pulled in towards the proton? Note I am completely ignoring the remaining protons in the the nucleus for the sake of the example.
Great explanation. However, where do these neutrinos come from?
I only know about the electrons and positrons surrounding the nuclei of matter and antimatter. And that they move closer to the nuclei when loosing energy emitting photons.
The most common examples would be interactions where a neutrino acts on other particles. It has to be Z-Bosons since a neutrino only interacts weakly and has no charge.
For example a neutrino can knock an electron out of an atom. This transfer of momentum is transmitted by a Z-Boson.
Another example would be if a neutrino hits a deuterium atom, which splits the neutron from the proton. This way solar neutrinos are detected.
In general, Z-Boson interaction are relatively rare and except maybe in supernovae (my own speculation here) have little importance in the universe.
The video is rather confusing. It's not that the nucleus interacts with an incoming neutrino (such interactions do occur but are extremely rare); the nucleus spontaneously emits a W- boson which decays into an electron and an anti-neutrino (or, in case of a W+ boson, a positron and a neutrino).
ravenous Thanks for repeating what Hank said. It is a rare occurence for neutrinos to interact with the proton because in an atom, it is mostly empty space so a neutrino which moves very close to the speed of light can just pass by without interacting with anything.
neutrinos rarely interact with anything, because they have incredibly little mass (as I understand it) and fly around at near the speed of light. When they lose the W+, I would assume they lose mass, do does this mean that an electron has less mass that a neutrino? Does this mean protons has more mass than neutron?
Well neutrinos are neutral so a positron would make an antineutrino of that flavor and would basically be the same as a normal neutrino (neutral charge) but it would have a negative spin, basically the same interaction would occur :P (i should state neutrinos decay into w+, w-, and in rare rare cases Z bosons (they decay too though into w bosons)) so yeahhhh.. Long story short its the same thing XD
Normally I understand the complex science distilled into comprehensible topics for liberal arts majors like me. But not quantum mechanics. People start throwing around quarks and stuff that is apparently smaller than that (which is a thing I didn't know) and I just can't. Physics is something I'll just never understand.
What about the electroweak force? I know it’s the former unification of electromagnetism and the weak force, but while I know what each of those two do, what does the electroweak force? Or at least, what do we believe it used to do?
Veritosophy well bosons are just energy carriers, like photons, it doesnt create energy out of nowhere though its more like... Particle 1 with charge of one and particle 2 with charge of 1, particle 2 emits a "force carrier" carrying its charge and giving that charge to particle 1, making particle 1 with a charge of 2 and particle 2 with a charge of 0
Basically the same way, but the W boson would be negatively charged instead, thus changing the neutrino into a positron instead of an electron, and changing an up quark into a down quark instead of the other way around.
A variant of this is _electron capture_, where there's a passing electron instead of a passing neutrino; this electron turns into a neutrino the same way the neutrino turned into a positron in the previous case, and the rest is the same.
I have a very fundamental question. Electrons negatively charged, are attracted to the positively charged proton. Yet the electrons do not collide with the protons but orbit or form a shell around the nucleus of the atom. So that when one electron meets up with one proton we get a hydrogen atom.With the electron in its orbital around the the proton. What keeps electrons and protons apart? The naïve assumption would be that the electron would collide with and cancel out the electrical charge of the proton. Of course then we wouldn't be here.
2 words: spherical. harmonics. :P sure electromagnetic force has a role in it but its the spherical wave pattern that traps these electrons. Ever wonder about the octet rule? Now you know why that is, charge has very little to do with it, its alllll about trying to gain stability
+Banter King: Yes, that does exist. Nomenclature-wise, I'm not sure if "potential" is the right word for it, but as atoms are struck with photons, their electrons jump up in energy levels. When the electron falls back down, it releases a new photon, and this new photon's energy (wavelength) is determined by how many levels the electron fell when it was released. That makes it sound like the new photon would be identical to the first one, but it's not always that simple: the electron jumps energy levels very quickly after absorbing the photon, but doesn't always fall as quickly, only dropping a few energy levels at a time. A well-known example is phosphorescence: the glow of glow-in-the-dark materials. Electrons absorb ultraviolet radiation, but they fall in energy states slowly, emitting lower-energy greenish photons as they go.
I think there are several other concepts that could be described as "electromagnetic potential," but in terms of electrons "storing" and releasing energy, I think this idea most fits what you wanted. You can learn more (and more accurately) by looking up "energy levels" in the context of quantum mechanics. You can also look up "phosphorescence" and see where the related concepts take you.
+Muzz Buzz thank you for your clear explanation I have received several non- replies on my G+ page. it is fascinating to learn there's nothing more exotic then the same Force that pulled me to the side when my car makes a quick turn. I love the fact that learning more leads to more questions.
+Herbert Miller The answer is Centripetal force, the electrons are travelling so fast around the proton that even though electrostatic forces of attraction are pulling them together the angular velocity of the electron is trying to pull away, this is the centrifugal force. for the centripetal force it equals mv^2/r, so if the velocity is higher and the electrons are more excited they have to have a faster velocity. It's like saying why doesn't the satellites orbiting earth crash into Earth. Their sheer speed is what keeps them in orbit which is exactly the same with protons and electrons.
Now I understand the Florence + The Machine song, Strangeness and Charm, more than ever! The lyrics are pure genius!
Fascinating stuff! Kind of wishing I'd taken Physics at school now... But then it would have killed it for me... Best keep it as an outside hobby!
I have a question about this " neutrino delivers a positive charge " theory. Something seems to be missing. If I understand it correctly then neutrinos are everywhere and passes through all things. How come then that not all elements are radioactive, if all it takes is a random encounter with a neutrino? afaik carbon 12 and carbon 13 can't have this happen to them. Why not?
+Hans Nørløv The most obvious answer to your question would be "this is incredibly simplified for the masses to understand" But, here's the gist. Entropy. Nature as we know it, tends towards the least possible potential energy in a system. Let's take C-12 and C-14 as our examples. Let's bathe both of them in a bunch of neutrinos. The neutrinos hit the C-14, and, on average, convert one neutron into a proton, and turn it into some N-14. That's because the C-14 wasn't inherently stable. It had too many neutrons in the pile for the protons. But the C-12, on average, came out the same. This is because neutrinos changing things around would decrease entropy, not increase it. As it stands, with 12 neutrons, and 12 protons, you'd end up with, say, 5 neutrons, and 7 protons. This would cause yet another radioactive isotope, B-14, which would, due to (I can't remember which counterpart, but due to electrons, muons, or tau) would just decay into C-12 anyway.
Wow, when I first heard him listing the "flavours " of quarks at 0:52, for a second, I actually thought he was serious!
I also have a question: how do the bosons "know" that there's another particle nearby with which they can interact?
The way I'm thinking about this is a sort of weak nuclear field of energy potential. I think it's similar to the way an electron emits a photon when its velocity changes. The weak force is still very foreign to me, so don't quote me o this.
2:53 the W+ boson changes the negative quark in the neutron to a positive one, but can there be a situation where a boson changes the positive quark of a neutron to a negative one? making it have 3 down quarks? if it did happen, what would the neutron turn into?
Yes, positive (up) quarks can change into negative (down) quarks by absorbing a W+ or emitting a W-.
However, protons and neutrons have a net spin of 1/2 and you can't get three quarks of the same flavour to have that spin because of the Pauli exclusion principle. The version of the proton and neutrons with spin 3/2 are the Δ+ and Δ0 baryons respectively. You can also get the Δ++ baryon for three ups and the Δ- baryon for three downs. However, delta baryons are heavier than nucleons and can decay via the strong force, so they decay really fast.
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