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Weak Interaction: The Four Fundamental Forces of Physics #2

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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 Like SciShow on Facebook: http://www.facebook.com/scishow Follow SciShow on Twitter: http://www.twitter.com/scishow References: http://hyperphysics.phy-astr.gsu.edu/hbase/forces/funfor.html#c4 http://hyperphysics.phy-astr.gsu.edu/hbase/forces/funfor.html#c5
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Text Comments (1448)
Abhishek Kumar (5 days ago)
Brother,,,I just wanted to compare all fundamental four forces,, i am 12th grade student,,,my question is straight...Mathematical representation of weak and strong nuclear force
DIANA CALDERON (12 days ago)
How long does the process of a carbon atom decaying take? Does it have to sit around for a while or does it change as soon as it interacts with a neutrino?
Avikash Nadan (1 month ago)
Elementary Particles like quarks, leptons, antiquarks, and antileptons are they inside Proton OR Nucleus? Anyone?
IThinkWithMy Dick (3 months ago)
So, does the weak interaction interact ONLY between a neutron & a neutrino? Or between ANY two particles consisting of quarks?
Manishchandra Dande (3 months ago)
You should probably make a video on the standard model of particle physics
Jonatan Åstrand-Ferris (4 months ago)
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)
OrphanPaper (4 months ago)
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
HINDU CODE (4 months ago)
the four fundamental forces have all ready been described in hinduism please read this kindle ebook https://www.amazon.in/dp/B07CWB47H1/
bsntwai mangang (4 months ago)
Awesome science!😁
tharak ram (4 months ago)
It's boring class😕😕 Use animation to make much more effective 😇😇
alejandro garcia (5 months ago)
thanks for the video the weak force is the force i understood the least
Alexander SHE (6 months ago)
you are taking too fast you idiot
Raymond Goins (6 months ago)
Hey yall Ive noticed that the 4 fundamental forces parallel the "4 Loves" that CS Lewis identified.  I hope y'all check that out (the book and the connection [and what it might mean])
dippycatcrochet (6 months ago)
is this beta plus or beta minus decay because it seems to be a mix of both and I'm so confused
jeno michael (7 months ago)
won't the electron and proton collide after formation
Shaun Mallawaarachchi (8 months ago)
Carbon 14 wouldnt be dating :,)
Jordan Fanapour (8 months ago)
Wait if neutrons have 2 down quarks, then why is it a neutral particle instead of a negative one.
Hugo Catt (7 months ago)
Jordan Fanapour it has an up quark (udd) u has a charge of +2/3 and d has -1/3 so makes it neutral
Mr. Anonymous (8 months ago)
electroweak force make a video on it
Drew O'Meara (9 months ago)
you are so awesome man, thank you for monk-level animation
Sky Leonidas (9 months ago)
wtf is mass then?
AwP (10 months ago)
Orenotter (10 months ago)
Wait... aren't electrons much more massive than neutrinos? Where does the mass come from?
Gabriel Pichorim (10 months ago)
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
Anjali Dutta (10 months ago)
Hey is this the mechanism behind beta particle decay?
Beckham Lee (11 months ago)
I don't understand ! ;-;
Alex Kim (11 months ago)
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!
Alex Kim (11 months ago)
what if a negatively charged boson approached a neutron (or a proton)?... or, does that not happen in nature (as far as we can detect as of yet?).
deepali panse (11 months ago)
Which software you use for editing ?
John Poole (11 months ago)
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?
@all (11 months ago)
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.
Akkeio Pather (11 months ago)
how does this relate to antimatter? what are the - electrons called quarks?
drania76 (11 months ago)
Neutrion means a small neutron in Italian. The term was first coined by Fermi.
mad cobra (1 year ago)
Does radioactive atoms need a neutrino to decay? They cant decay themselves?
Sir Sir (1 year ago)
So the weak force is the one reasonable for Transgenders!
Braeden Young (1 year ago)
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!?
Celarc Gaming (1 year ago)
"Quarks have 6 different flavors. Vanilla, chocolate, root beer....... sorry."
REME (1 year ago)
Great video. Thank you
NobleWood104 (1 year ago)
When does this happen, randomly? Does this happen in our bodies?
Joshua Mwaniki (1 year ago)
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?
Combat King 0 (1 year ago)
If you capture a lepton, will it give you it's pot of gold?
孙博一 (1 year ago)
at 2:41 , what does he meant by "there"? Does that means the weak force pulls W Boson into the neutron?
Lanre Logan (1 year ago)
You said the SNF helps keep quarks of protons and neutrons together, could've sworn it only holds the protons to other protons >.>
Anto Jude Geoffrey (1 year ago)
Where did the charge comes from? Kindly make a video about this. Because its confusing that no one could answer correctly.
Barchueetadonai (1 year ago)
If a neutrino gives up a W+ boson to become an electron, where does it get the extra mass from (electrons have much greater mass-energy than neutrinos as far as I know)?
Mgo Minasian (1 year ago)
what is the relationship with radioactivity and the weak force??
TechChat (1 year ago)
thanx for the help
This is how alchemy is made in Full Metal Alchemist LOL
Engineer Ahmed (1 year ago)
Wrong info given here. Neutron mass = electron mass + proton mass Clearly Neutron decays into electron proton pair
iosef 333 (1 year ago)
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.
Some Guy (1 year ago)
If one could prevent neutrinos from interacting with something, would that be a way to stop particle decay?
MikeRosoftJH (1 year ago)
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.
ahmedshinwari (1 year ago)
The video actually did not explain the weak forces much. So thumbs down.
mrgaiusbonus (1 year ago)
And the Z boson just sits back and watching the subatomic hanky panky? seriously what is its job?
MikeRosoftJH (1 year ago)
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.
Dr. Whis Grant (1 year ago)
Dr. Whis Grant (1 year ago)
Aryan Soni (1 year ago)
what if we do the carbon to nitrogen experiment with radioactive element would it still be radioactive ??
ibitedeadskunks (1 year ago)
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.
Sir Iodine (1 year ago)
How is a Neutrino and I similar? Both are constantly penetrating your mum
Bob Webster (1 year ago)
weak interaction In which Hank's countenance resembles that of Beverly Hofstadter's
The Primeval Void (1 year ago)
Wait, I have a question here. You're telling me that radioactivity and nuclear decay happens because neutrinos brush past atomic nuclei?
Mathias Fantoni (1 year ago)
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.
Jason Xu (1 year ago)
wait the carbon-14 and nitrogen-14 atom gifs were the same
Abdul Wadood (1 year ago)
need answer what happend to positron which changed into electron. why the number of electron is same in nitrogen as it was in carbon
sfruizmiranda (1 year ago)
what was the neutrino before losing the positive W boson?
sfruizmiranda (1 year ago)
how would the Z boson act?
Windsaw (1 year ago)
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.
How does the neutrino know to send a W Boson into an unstable nucleus and not any nucleus?
MikeRosoftJH (1 year ago)
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).
giannisniper96 (1 year ago)
protons don't decay that's one of the predictions of the standard model, at least not within the next 10^35 years
CroSs xD (1 year ago)
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.
ravenous (1 year ago)
From my understanding, its a very rare occurrence for a neutrino to actually hit the nucleus ?? Doesnt make sense to me but thats what i heard
ravenous (1 year ago)
Protons decay into neutrons through weak force ie. Neutrino making a W+ boson and changing a neutrons down quark into an up one making it a proton and the neutrino would turn into a positron
Novitatis Veritatis (2 years ago)
If I win the lottery, I'm donate $1M to this channel.
Christopher Minge (1 year ago)
DangerZone (2 years ago)
So quarks are like wiping your ass? One up, one down, and one to polish.
Toaster Strooder (1 year ago)
No, it's one up, one down, one charming, one strange, one on top, and one on bottom. Far simpler than the number 2!
quest0 (1 year ago)
Władca Wymiaru Polerowanie polega na wygładzaniu
Władca Wymiaru (1 year ago)
Nope. Polish znaczy polerować/szlifować. No i dawałem tylko pozdrowienia :\
quest0 (1 year ago)
Polish to czasownik wygładzać
Władca Wymiaru (1 year ago)
Greeting from Poland ! :\
Richard Le (2 years ago)
You forgot to mention that an electron antineutrino is also emitted from beta decay.
Mackenzie Stuart (2 years ago)
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?
Hermaeus Jackson (2 years ago)
This was the one force that i've really understood. This was a helpful video.
赵哲 (2 years ago)
in a supernova explosion protons+electrons makes neutrons, but here you add a w boson to a neutron to make protons. HOW IS THAT POSSIBLE?
Ghost7856 (2 years ago)
What if we threw a positron at the neutron instead?
ravenous (1 year ago)
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
Zvonimir Družianić (2 years ago)
I think we didn't throw electron here. The neutrino lost W+ and became an electron.
megan5815 (2 years ago)
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.
Dan Trivates (2 years ago)
So what about the Z Boson - what does it do? this video could have been a good 10 minutes
SaberTooth2251 (2 years ago)
sooo...two questions 1.) wouldn't this imply that a neutron is actually negatively charged? 2.) does this mean an electron is lighter than a neutrino?
Richard Le (2 years ago)
1. Down quarks have -1/3 charge and up quarks have +2/3 charge so overall, the neutron has neutral charge. (2/3-1/3-1/3=0) I'm not sure about 2 though.
YL Storage (2 years ago)
Fact: Electron is way way heavier than a neutrino Question: how does a neutrino gain so much mass after losing a w- boson thus turning into an electron?
opticnirvana (2 years ago)
How is the weak force a "force"? It doesn't seem to attract anything, just change a nucleon by changing one of its quarks.
MendMyWings 7 (2 years ago)
Have I been pronouncing quark wrong? Is it really pronounced like the first part of quarter? I'e been pronouncing it 'kwahk' x
Andrew Lopez (2 years ago)
I'm gonna have to watch the whole series again
Jack Kierath (2 years ago)
was wondering why a vid by the well known hank green was this low quality... its from 2012, not to say that this is bad, just that in comparison to his newer vids it is :P
Mikle Talalaevskiy (2 years ago)
Excuse me guys.You're telling me an atom can DECAY to a higher proton count? Do neutrons have higher change to just flip one of their quarks then protons have?
mdcourtney82 (1 year ago)
DoomMantia Is this where the electron gains its mass from compared to the neutrino? Does the W boson deduct mass?
ShotgunLlama (1 year ago)
Also it has the same total number of hadrons in its nucleus, and elements with low atomic numbers(like carbon) tend to be stable with roughly equal numbers of protons and neutrons.
DoomMantia (2 years ago)
Consider that the neutron has a slightly larger mass than the proton and it will sound less strange.
upwardstumbler (2 years ago)
what are quarks made up of?
Pedro Alves (2 years ago)
supposedly, it is indivisible, but who knows what we can find next?
michael einhorn (2 years ago)
fundamental particle no components
Aman Rubey (2 years ago)
you know physics as well as chem
Laura Rothman (2 years ago)
up down strange charm
Totally not a spam bot (2 years ago)
Then the electron flies out as beta radiation, and then is stopped by a few metres of air or some aluminum
King Hetzer (2 years ago)
Can you do a video on string theory
Aumedi Wibisana (2 years ago)
Is it possible for the weak foce to change the Proton into Neutron? if it is possible, How?.
Symbol Guy (3 months ago)
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 (1 year ago)
+ravenous cool thanks man
ravenous (1 year ago)
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
Veritosophy (1 year ago)
What is a boson? It looks like bosons can keep being given to up or down quarks, changing it's 'polarity'. Where does the energy go?
DoomMantia (2 years ago)
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.
xenn0ux (2 years ago)
It amazes me how scientists can come to such conclusions
Matthew Hugg (2 years ago)
You should hit the crew of you guys in the forest
Christopher Minge (1 year ago)
xd epic!!
Marta Ross (2 years ago)
I cant be the only one who think he looks like he has a love bite on his neck.
Herbert Miller (2 years ago)
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.
ravenous (1 year ago)
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
HalcyonSerenade (2 years ago)
+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.
spencer z (2 years ago)
Yes, exactly! It's just like planets orbiting around the sun. Even though they are attracted to the sun by gravitation, they only orbit due to centripetal force.
Herbert Miller (2 years ago)
+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.
Muzz Buzz (2 years ago)
+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.
ron enoch (2 years ago)
The game is keeping everything together, now there is a metaphor.
Girl in a Trance (2 years ago)
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!
Hans Nørløv (2 years ago)
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?
Rhyno Orhyon (2 years ago)
+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.
TheWyrdSmythe (2 years ago)
Aw... Ya mentioned it, but ya shoulda talked more about solar fusion -- the weak force is so important there!
Ben L (2 years ago)
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?
LeTtRrZ (2 years ago)
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.
Abdullah Ar Rafi (2 years ago)
Your videos are short and informative. Thanks for such helpful videos...
Christopher Minge (1 year ago)
u welcome :D
Lior A. (2 years ago)
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?
Lior A. (2 years ago)
+IamGrimalkin I didn't understand everything but I got my answer, thank you
IamGrimalkin (2 years ago)
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.
Jonny Jackson (2 years ago)
love this channel but don't need to see the same thirty second advert that precedes it each time I watch a video.
Jonny Jackson (2 years ago)
I love the channel not the adverts. Can live with the five second ones but not the same thirty second ad for each post.
Jonny Jackson (2 years ago)
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Super Suchti (2 years ago)
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Jonny Jackson (2 years ago)
+Super Suchti no, but I'll get one.
Super Suchti (2 years ago)
don't you have an AdBlocker? xD
Will You (2 years ago)
You will never see neutrino scattering off neutrons like that.

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