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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It's very easy to understand why electromagnetic force and gravity are inversely proportional to the distance squared. There is also the London dispersion force, which is inversely proportional to the sixth power of the distance due to being based on fluctuations in charge distribution. I always wondered why the weak interaction has such a short range. Is it due to the short life of the W and Z bosons?
That was "the best" explanation of the "weak force" I have ever heard. But it leaves a question.
Is it appropriate to call it a force? For example, does it, applied over time, create a change in momentum? Or should it be called an interaction, but not a "force"?
I don't get one thing... It wasn't mentioned in the video but it still has to do with this topic. More specifically, I don't understand why there is a electron anti-neutrino in beta decay. In the equation it makes sense because we need an anti-lepton to make the equation correct but I don't get where its coming from. Is it another part of the electron neutrino which gets 'emitted'? Or anything else?
It all sounds like crap to me.
I'm not convinced that there are any such beasts as protons and neutrons -
they are just mixtures of quarks - whatever they are.
So the nucleus of an atom is a mixture of quarks & by the principles of quantum physics they
can be in more than one location at the same time.
Therefore - you can't say that - " there's a proton and there's a neutron."
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.
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