@@nowster THE Neutrino: You clearly don’t know who you’re talking to, so let me clue you in. I am not in danger, Paul. I am the danger. A guy opens his door and gets shot and you think that of me? No. I am the one who knocks!
An excellent video on this very exciting topic. It was the first explanation of the neutrino oscillations I've heard that helped me to somehow grasp the idea of them switching flavour as we observe them.
The first bonus fact has greatly knocked me around. No acceleration in the massless photon I could appreciate, but how does a massive (even when tiny) particle have no need at all of acceleration?
When a neutrino is born, the way Standard Model describes it, is you have an event (a node in a Feynman diagram) with 3 operators working: annihilation of a W- boson and creation of 2 new particles: an electron (or tau or mu) and a neutrino. It's an instant event, and total momenta of outgoing particles must match momentum of original particle, so they are born with that momentum (and speed) they carry away. This is very similar to the case with photons that are also born with a certain momentum and speed.
Oh, thank you. But - and forgive my casting aside the Feynman diagrams - the photon borrows exclusively from space at the total expense of time, whereas the neutrino answers to the clock. I guess what I'm asking now is: how can the quintessentially temporal find the exemption necessary to by-pass acceleration?
@@TheyCallMeNewb it doesn't have to "by-pass acceleration", it's not a little ball that's born stationary (relative to what?) and then accelerates. Remember how in QFT particles are really waves, parts of quantum fields. One field loses a wave, another field gains a wave, and this wave evolves in time so it looks like it's moving with certain speed. How fast it moves depends on its shape and the governing law of its evolution. If it's born with proper shape, it already has the necessary speed / momentum, no need to accelerate.
I had availed myself of an idea the likes of which I perhaps shouldn't. We dabble in fields, and as such Heisenberg maybe channeled. The neutrino is characterized by a wave packet synonymous with among other things, the 'speed' that maybe measured. That really burgeons for me that whole 'wave/particle duality' component. The thinking is helped along by time tending to parse out the neutrinos by type in accord with respective speed. Updating schema; and thank you.
Three questions on neutrinos: 1. Why does the oscillation of masses not violate conservation of mass? Does this mean that different mass neutrinos travel at different speeds? 2. Is there a CMB equivalent in neutrinos? Have we/can we observe it? 3. All neutrinos are left handed. But they travel slower than the speed of light. If we travel faster then a neutrino will it appear right handed?
Since neutrinos travel slower than the speed of light, you can define a reference frame that travels faster than them. From that reference frame a left-handed neutrino would appear to be a right-handed neutrino. I'd be interested in a video on this.
Why would we need a video on this? When you see me run away from you sitting in your parked car, you see me carrying my phone in my left hand. Because I'm a lefty. But when you drive past me and look at me in the rear-view mirror, you see the image of right-handed person. You do the transformation in your head to know I'm left-handed. Because you know how mirrors work. Why would it be any different for sub-atomic particles?
@@jonwesick2844 That was believed when it was thought they moved at the speed of light. Your original comment is correct, though: neutrinos.fnal.gov/mysteries/handedness/. In the rest frame of the particle that decays to produce a neutrino, the new neutrino is left-handed. In other frames of reference it might not be.
@@XEinstein your @ me but I don’t know which part of my comment you’re replying to. It’s already implied in my comment that neutrinos are only left handed. Making them look right handed by looking at them in the rear view mirrors makes for a great hep-th paper but not a good RUclips video. Feel free to disagree. It’s just my opinion. But I explained it clearly, and you haven’t given me any reason to reconsider it.
Thank God someone finally answered the question of what we know about the mass of the neutrino. That 2011 experiment was supposed to have something of an answer on that, but then the FTL neutrinos stuff hit and drowned out anything to do with the actual mass of the neutrino because it wasn't attractive to most people. I'd argue for the possibility that their mass is actually infinitesimal or >0 and less than any measurable mass. It would make the people who insistented on massless neutrinos effectively correct and incorrect. Their speed would also be infinitesimally close to the speed of light, making decoherence impossible. Don't we measure the neutrinos from a supernova first because they travel unimpeded, and light has to make it through a bit of gas first?
I think we have a lower bound on the difference in the masses of two of the mass eigenstates. And therefore, a lower bound on the largest of the 3 masses?
I gave a genuine question for anyone who happens to know the answer. Background: The "speed of light" is short for "the speed of light in a vacuum". Light slows down in materials like glass and water, and it's possible to go faster than slowed-down light in a material, hence Chenerkov radiation. My question: While photons are slowed down in such a medium, do they experience the passage of time?
Hi, please can you do a comprehensive video about atomic orbitals, proton spin and quantum leap. I like the way you do such complicated topics in physics, so it'll be much of benefit if you discuss the aforementioned requests since they're mind spinning especially when read in articles 🤕
Really interesting video this time. They usually are of course. Thank you. So, if a photon experiences the entire timeline at the same time, using the speed estimate with 18 nines, how long have those big bang neutrinos been travelling (according to their perspective).
Ignoring universe inflation, I get the separation in time between a light photon created at 15 billion years ago and a neutrino to be close to a quarter of a second difference between them. Which would mean at the math I have, and I might have missed a decimal or two, 4.7 years, maybe? That's how old the neutrino would think it is since the birth of the universe... And that's using the 18 nines and a five... I'm more certain about that than the difference in arrival time, I'm kind of doing this from the top of my head and it's late at night, it's also a year later) apparently I also suffer from some time dilation)) I'm curious to find out why I got such a different number than the post above me, did I make a massive math mistake???
Because Neanderthals didn't go extinct. They evolved into physicists. A simple universe would imply that we exist just because we exist. By .making it complicated, such as Einstein and his relativity nonsense, it allows for the existence of a god - intelligent design - to make it all happen. As you can see, none of these Neanderthals want you to know the truth otherwise you wouldn't follow and obey their Lord Jesus Albert Einstein. F=ma. Mass and Acceleration. Space and Time. E=mc. Mass and Acceleration. Space and Time. Since mass is just energy with an Acceleration factor < c, Acceleration equals Acceleration. Energy equals Energy. The universe is defined by its Acceleration value. Everything is an energy field with one field being accelerated by another energy field. As you can see, the human race needs a god to justify their existence. By making the universe mysterious and difficult to understand, it allows for a supreme being to make it all happen.
So, how sure are we that photons travel at c? If the only clue to neutrino's mass is oscillation, then photon's lack of oscillation is not exactly a proof that it doesn't have, for example, the same mass as neutrino.
*Measuring Neutrino mass / energy / velocity* A strong electric field can separate a Hydrogen atom into proton and electron pushed into opposite directions due to opposite charges. A reverse field can push them into each other causing electron capture ? It turns a proton and electron into a neutron and neutrino. It may be easier to leverage conservation laws (of momentum and energy) to compute the mass, energy and momentum of neutrino than to measure it experimentally when it's already 1 light-second away from the lab.
If mass is given by a particle's interaction with a field, does it just ATTEMPT to go at the speed of light and sort of zig-zag back and forth with the field waves/particles along the way? Is that oscilation back and forth at light speed the timer that causes time dilation for objects traveling at different sub-light speeds?
@@thedeemon Thanks, I'll have to give that a good read. As for time dilation, (even if just for context for my odd comment) I had seen an example somewhere using a photon bouncing between two mirrors inside a spaceship would appear to an outside observer to have a zigzag path, the faster the craft, the longer each bounce in the zigzag and the longer/slower each would take at the speed of light. . . . . . here the image came to mind that other particles' "internal zigzags" being represented as a bunch of faynman diagrams chained together where the distances between each appear to stretch for an outside observer as the particle goes faster, slowing the rate of any particle decay or other interactions. (that's what was going on in my head, anyhow)
I really love these videos! Q: Can low-energy slow neutrinos be created ab initio, i.e. slow neutrinos that are slow without the need for decoherence or traveling a fantastic distance? Also, I presume that neutrinos created at the big bang slowed down a lot during the inflationary period. Can scientists estimate their number and account for the gravitational effects of that neutrino "residue"? Thanks again!
There's a conserved quantity called lepton number which more or less mandates that for every electron (muon and tau too but these are rare enough) there's an anti neutrino and vise versa for antiparticles. Unless this conservation law is massively broken at the dawn of time, there should only be as many (anti)neutrinos as there are electrons, which would hardly amount to any noticeable mass
@@bottlekruiser I hadn't thought of that. But antineutrino/electron and neutrino/positron creation would still result in "left over" neutrinos if the electrons and positrons annihilate and if a neutrino is its own antiparticle. What do you think?
@@tedlis517 heck you're right I totally didn't think of that They *could* have annihilated with each other too, but i bet the cross section of that is so small it might as well not happen A way to test that could be looking for em radiation in places where it's not supposed to be
OK so the neutrino form Andromeda arrived here 40 µs after the photon. But it would also be interesting to know how much time passed for the neutrino? 🤔
How ironclad is the case for neutrino oscillation requiring rest mass? Like are there alternative theories where neutrinos travel at C but still produce the observed oscillations? If so, how seriously are they taken?
As solid as special relativity. The fact that they oscillate requires that they have a speed less than c. Think of each flavor as a state. Each state will have several durations. All of those durations are defined by times. In order for the neutrino to be affected by time requires a speed less than c. I'm not an expert so I would do some reading up on it if you are really interested.
Yep - due to special relativity, the photon "sees" a cosmos that is "squeezed" to zero length in the direction from the source to a static observer. So if you ask the photon itself, it'd tell how it got created, traveled, and hit the observer all in the same instantaneous moment.
Yep! And they experience the events of their creation and annihilation simultaneously, too. It's weird being a photon. Even weirder to be a CMBR photon sailing uninterrupted for thirteen billion years through empty space, then all of a sudden some jerk puts a radio antenna in your path.
The most intuitive way to explain how or why a particle like a photon (or electron, etc) might behave as an uncertain location particle while also like a polarizable axial or helical wave ''packet'', given that everything in the universe from electrons to solar systems are in orbit with something else pulling them into polarizable axial or helical apparent waves depending on the orientation of their orbits as they travel thru space, is that they’re in orbit with an undetectable dark matter particle pulling them into polarizable axial or helical apparent waves as they travel. And given that we know we’re in a sea of undetectable dark matter but don’t know where it’s disbursed, we can imagine that they’re in orbit with an undetectable dark matter particle pulling them into polarizable axial or helical apparent waves as they travel where the speed of their orbit determines the wavelength and the diameter is the amplitude which would explain the double slit, uncertainty, etc. No?
Is the speed of neutrinos an inherent property? Is it possible to have slow neutrinos, or is it just impossible to detect them unless they have a lot of energy?
Anything not moving at the speed of light in a vacuum is stopped in some frame of reference (its own). Subluminal velocity is always relative. However, neutrinos are always produced moving very fast in the frame of reference of the particles that created them.
@@christosvoskresye is right when it comes to velocity being relative. You guessed correctly that slow neutrinos are very difficult to detect. But they're also relatively uncommon. Neutrinos carry "missing" momentum from certain quantum interactions. Because the typical magnitude of this missing momentum is large compared to the neutrino's tiny mass, their typical velocity is near the speed of light. Yes, as far as we know, the constants that define these interactions are fundamental properties of nature. Like the mass of an electron, speed of light, Plank's constant, etc.
I have a question: If you infer that neutrinos must have mass because they experience time (because they oscillate "change"), why shouldn't that same argument hold for light? A photon sent from a far away galaxy loses energy (redshift). So the photon "changes", too. Ergo: A photon experiences time and should have mass...
A photon has mass. You can argue that's how gravity can change its path, if you think gravity is a force (special vs general relativity). What a photon doesn't have is "rest mass". The stretching of space does steal energy from a photon, over very great distances, so its mass is also reduced, but its rest mass remains zero. This is an example of how a universe that is expanding (or contracting) does not perfectly conserve energy. This is all pop-science oversimplification, of course. The way I read this is, because different neutrino flavors have slightly different masses, they have slightly different wavelengths (everything is a wave as well as a particle). The difference in wavelengths means the probability of interacting with any superimposed component of the waves should vary over time, at very slightly different rates for the superimposed neutrino types. This is not pop-science as much as it is speculation. It would be interesting to read a reaction from someone who understands the math better.
the best test might be the supernova SN 1887A. neutrinos arrived on earth only slightly before the flash of light,. neutrinos sped through the body of the collapsing star while the photons diffused and were slightly delayed the light. neutrinos traveled slightly slower than light. Adjusting fir this proved that they do have mass and put an upper limit on their mass.
The wave length of light can change which does not affect the velocity. However because of the slight mass of the neutrino a change in the wave form must also imply a change in velocity, but completely undetectable by current technology.
Correct me if I'm wrong. But I think you're asking if different flavors (not "color") of neutrino have different mass states. Yes, if this were the case, it would have implications for their momentum and therefore velocity ("speed"). Check out their other video "How do neutrino oscillations work? | Even Bananas 10" about 4 minutes in. For some reason neutrino mass state does not correspond to neutrino flavor. Weird, huh? So no, I don't think they change speed.
We often hear about the result of something traveling near the speed of light. I.e. That 2.5 million lightyear journey going by in an instant from the perspective of the neutrino. What puzzles me is the experience of the neutrino during that time. For a more down to Earth example, let's say you're in a vehicle that is traveling a significant fraction of the speed of light in a large circle so that you can always keep a single landmark in sight. Ignoring things like the effects of g-forces liquifying your body, or boiling away from air friction, what would you see? Would that landmark appear normal until you stop, would you see it deteriorate rapidly as if watching a sped up video, just see a blur, or something else?
What do you mean by "you can always keep a single landmark in sight"? Is it in the center of the circle, or somewhere very far? If you ask "what would you see", it's best not to use Lorentz transformation, and just use the constant speed of light and Doppler effect. Imagine light spreading from the object at constant speed in waves, and you intercepting these waves. If you move towards the object, it will appear greatly blue-shifted. If you move left, it appears more to the left, and so on. Plus the object ages quickly, since you move through spacetime faster along the time direction than that object.
@@PhysicsPolice You may want to rename yourself, as your name suggests deep knowledge of physics, where there is very little. In this case, you can ignore acceleration and use piecewise linear path, with pieces having zero length in the limit.
@@PhysicsPolice This question does not require general relativity, as there is no gravity involved. Twin paradox does not require general relativity to explain. Again, you show little understanding of physics.
@@PhysicsPolice You're just repeating yourself. Special relativity deals with high speeds and acceleration just fine. In fact, a circular track is a famous example where special relativity is used. You can view the circular track as some funny gravitational field that points outward, and you sit still in your car, and the gravitational time dilation would be the same as from special relativity. But then you need to have the landmark rotate around you at superluminal speeds, which hardly gets you anywhere. Switching rapidly between inertial frames along the track gives immediatelly correct results. Momentarily comoving frame of reference does not have a wikipedia page, but it's still a thing. For twin paradox, it's quite obvious that gravity plays no role there. Obviously, the connection between gravity and general relativity escapes you, which leads us back to my first comment.
(1) Something travelling at or very near the speed of light e.g. a neutrino travels about one Planck length per Planck time. By definition. (2) Good question! I tried to find the answer, but unfortunately I'm out of my depth. I hope someone else can chime in... I'm curious now, too.
The duality that I see with Neutrinos having mass and, thereby, the effect on the momentum vs. if Neutrinos oscillate between having mass and not having mass. So a neutrino leaving a supernova or jet of a blazar can arrive at roughly the same time as the photons do, so 99.9999% of the time, the neutrino travels at the speed of light; therefore, photons do not pass inside a vacuum. Instead, the neutrino oscillates for a tiny fraction of a second and can change its form or interact with matter. I am basing that on neutrinos associated with the photons coming from a supernova or blazar. If either of those is traveling away or even toward us, that creates a momentum problem that doesn't exist if it oscillates. ------------------------------------------------------------- Here is my fundamental problem. A neutrino is created in the infall of matter produced in a supernova. How fast is it traveling relative to the matter that made it, and how fast is it traveling relative to us? To the matter that created it, the neutrino is traveling at 99.99999995% the speed of light. Now, how fast is the matter traveling away from us? Let us say the matter is traveling at 3% of the speed of light. Then, the neutrino relative to us would be traveling 3% + 00.00000005% the speed of light, or 3.00000005% the speed of light. Now we calculate when a neutrino should arrive at the earth vs. when a photon would arrive at the planet. Over extremely long distances, the time would change dramatically. That is vs. a neutrino that is traveling 99.999999995% the speed of light for a picosecond, five maybe ten times over a billion + lightyears. We wouldn't even notice the difference between the photons and neutrinos arriving.
I don't understand this now! Most basic particle physics tells us that individual lepton numbers are conserved no matter what, but now if suppose in a negative beta decay we get an electron and an anti electron neutrino, if here we consider the superposition, so does that mean that neutrino produced can be anyone among electron muon and tau? How does one then impose the lepton number conservation?
Based on the Fun Fact at the end, where the speed of light (photons) through a non-vacuum is less than the absolute vacuum velocity C, neutrinos keep chugging along at so close to C that for practical purposes it is C because of their non-interaction with matter. That implies that photons leaving Andromeda could arrive at Earth *after* the neutrinos due to their (photons) occasional and subtle interactions with the mass present in space (gas atoms/molecules, microscopic ice grains, dust grains, etc.) in exceedingly small quantities but which also sum to something more than insignificance due to the vast distances travelled, and also the electromagnetic fields that they interact with. Would that be so?
Follow-on: So, if neutrinos have a crazy-small amount of mass, then the focal point for an observer viewing a distant galaxy via an Einstein Ring would require a subtly different focal point using neutrinos compared to photons?
Nice. I have one question, is it possible that a neutrino and an anti neutrino ahnihilate each other? I know there're a lot of anti neutrino from beta decay and the sun bombard us with neutrinos, yes, I know it would be a very rare interaction, but would yiled a very specific radiation, we should be detecting it, right? Or it's so rare that they would hit one another?
I'VE ASKED THE FOLLOWING ON SEVERAL PHYSICS SITES, WITH NO LUCK: Photons always travel at c and express this regardless if you travel toward or away from the source. The energy difference is expressed in a frequency shift. DO NEUTRINOS TO THE SAME THING?
if they dont interact with other matter or else, are neutrinos then the only entity in the universe that travels on straight lines thru timepsace and therefore does the most accurate measuring of distances?
That’s mind blowing! If photons experience time as being none linear. Do they experience the past timeline of the universe, or the past and also the future? Could it somehow prove/disprove pre-determinism?
If a car is moving and it carries a broken clock that doesn't tick, does it prove anything about predeterminism? Time not ticking for photons is in a way similar to a broken clock, photon still moves through time in our reference frame.
Do neutrinos get absorbed (somewhere somehow) at the same rate as they are being created? If not, then that means that the number of neutrinos is growing constantly. => The sum of the mass of all neutrinos would also grow over time. Dark matter = gigantic clumps of ancient, cold, coalesced neutrinos? ;-)
I understand that it is necessary that a particle be massless to travel at lightspeed. i.e. If lightspeed, then massless. But, I have also heard the contrapositive: that is necessary that a particle travel at lightspeed if it is massless. i.e. If massless, then lightspeed. Why? Why is this contrapositive true? Is it true?
Yes, wavefunctions for massless particles are waves that travel at c. From relativistic wave equations we get that when m=0, k = w/c, and group velocity is equal to phase velocity v = w/k = c. en.wikipedia.org/wiki/Weyl_equation en.wikipedia.org/wiki/Group_velocity
This question could mean at least two different things. (1) Do neutrino flavors have different masses and therefore different velocities for a given momentum? Not quite. There are three neutrino mass states, Each with different likelihoods of interacting with matter as an electron neutrino, a muon neutrino or a tau neutrino. But it's not as simple as one flavor being heavier than another. (2) Do different neutrino-producing interactions result in different mean average momenta for the resulting neutrinos? Yes. And these different types of interactions produce a specific kind of neutrino. So when you detect a neutrino, it's momentum gives a small hint how it was produced.
There is something here I have never understood: light in a medium travels slower than the speed of light in a vacuum, and it can change frequency, depending on just what it resonates with in the medium. It seems that neutrinos moving slowing the speed of light and changing flavor is not sufficient proof they have mass as the same mechanism could be at play.
*facepalm* I hadn't thought of why they can't be traveling at the speed of light. Is decoherence just theoretical/hypothetical or can/has it been measured? I LOVE Jessica's accent 😍 (I could enjoy listening to her speak about neutrinos for hours ... or even physics in general ... or toothpaste, groceries, math, etc 😆)
The answer to the question "is X *just* theoretical?" depends on your beliefs. Models in physics tell us what is real, according to some theory. To believe a theory is to believe all its model's parts are real. The scientific method doesn't prove theories true. It's a process that allows us to find models closer and closer to the truth. You can believe the most time-tested, accurately measured theories, like QM or GR. Or not. That's up to you. If you believe in QM then decoherence is real. Every observation of the macroscopic world is consistent with decoherence. So yes, it's been observed, if you believe QM. I think you're asking can it be quantified. Yes, if you search for "quantifying decoherence" in the arXiv, you get plenty of results. Most are specific to one small regime because decoherence is complex and good methods of quantification it depend heavily on the system of study.
So, since it takes a photon no time to travel from the Sun to the Earth, to the photon the Sun and the Earth are in the same place. As are all other things in the Universe.
That's a good question and I had not thought of the Cosmic Neutrino Background as a thing before. There is good sources online including one on Wikipedia which states the CNB or CvB came into existence ONE SECOND after the BB. en.m.wikipedia.org/wiki/Big_Bang#Cosmic_microwave_background_radiation The CMB did not occur until temperature reduced enough to allow protons to bind with electrons to form hydrogen. This did not occur until 380,000 years later!! When electrons joined with protons they entered in a high level energy state and thus in a higher orbital. When transitioned to a lower energy state and thus lower electron orbital they released a photon. This began the CMB which has shifted red because of the expanding universe. So now guess which arrived first the neutrino or microwaves?
That's much like asking which arrives first, sound from 5 seconds ago or sounds from 1 second ago? Parts of the world are, say, 342 m away from you, and parts are 5 times that distance. The time when you hear a sound depends both on how far away the sound originated, and also when the sound was made. It's the same with neutrinos.
Hi Kristy (and fellow bananas, sorry had to type that :) ), It seems quite fundemental that nothing can be faster than the speed of light (in vacuum), c. Even neutrinos cannot beat that. But that is not what i am curious about. An observed phenomenon is Charenkov radiation. As i understand it, it is radiation by particles seemingly faster than the speed of light through a medium. Can neutrinos do this as well? Can they cause this kind of radiation? Or don't they interact?
Yes, you're right. We discuss briefly how T2K uses the SuperK Cherenkov detectors to study neutrinos in this episode: ruclips.net/video/QpnSmb37t00/видео.html
Neutrinos appear to have mass. Mass affect light’s speed. And cause light to bend. Could neutrinos be responsible for light’ bend when passing next to a start instead of gravity? Could density of neutrinos be responsible for light bending toward center of a black hole? Could neutrinos be responsible for speed of light as we observe it?
Can this hypothesis has possible evidence: Time can be explained relative to energy i.e., imagine at relativistic speed a region is created of the energy (potential) due to that less energy is transmitted for the observer outside the region. This indirectly explains that time can be rate at which observer observe the energy?????
If an observer where to travel at the same speed as a neutrino , would that neutrino be stationary relative to the observer ? In other words why are these particles associated with any particular speed ?
At those speeds if you could come up with a method to capture them, the deceleration may cause a pretty big energy release. Possibly better than solar panels, and working in storms.
The problem with this, as Dr. John Bacall of Princeton pointed out, is if this were true we wouldn't have been able to observe any neutrinos from Supernova 1987a...
Quantum spin is even-dimensional. Mathematically it is described as four dimensional with two degrees of freedom. Even dimensional spin is orientable, which means it remains the same chirality no matter how it is observed.
Another thought provoking video. Thanks! OK, so a Neutrino has mass. That means it can be deflected by gravity. Does their coherence get affected by travelling towards or away from a large mass? How does gravity affect the speed?
Actually the photon is not affected by light directly. It is space time that is changed by gravity. Thus there is the appearance that gravity is affecting the path that light takes.
@@michaeldeierhoi4096 I assume you meant that a photon is not affected by gravity. Well, you can apply the whole "gravity is an illusion" argument to massive particles, too.
@@michaeldeierhoi4096 Straw man. John said, "deflected by gravity" which indeed happens indirectly. Don't say "Actually" like you're correcting him when you're not. And no, there's not just the "appearance" that gravity is affecting the path that light takes. Gravity is *actually* affecting the path that light takes.
@@christosvoskresye Exactly. I suspect Michael is confusing Newtonian gravity with GR. Because photons have zero rest mass, they experience zero force from Newtonian gravity. But in GR the paths of all particles, regardless of their mass, are affected by "gravity" i.e. the metric tensor.
It sounds like you may be curious about how neutrinos interact with other neutrinos. We actually don't know the answer. The Standard Model predicts neutrino self-interactions at a level below current experimental capabilities to measure. I recommend you check out a paper called "Neutrino Self-Interactions: A White Paper" published this year.
If neutrinos don't need to accelerate, then that would make them massless like photons. Does that mean that they start out as massless, and then eventually run into a Higgs boson and then acquire mass briefly? Would that explain the neutrino's ethereal flavour changing and mass changing? It only interacts with the Higgs field briefly, during which time it: slows down, changes mass, changes flavour, etc. Then during the rest of the time it just travels along at the speed of light where it has no mass, has no flavour, passes through everything, etc.?
no, that doesn't make them massless. It just means a neutrino is born having a certain momentum and speed, all particles are also waves after all. Particle creation operators in QFT can produce particles with any given speed, no acceleration from zero is necessary.
@@whiteman2707 mathematically - a wave's group velocity is determined by its frequencies in time and space, and for non-zero mass case they are related such that the velocity is less than c. en.wikipedia.org/wiki/Klein%E2%80%93Gordon_equation Philosophically - why would it be born with speed c, why not anything else. It seems there's no good argument either way.
@@thedeemon Of course there is a good argument for why it should be born at c, rather than any other speed, because c is the speed of causality in the universe. Everything is going at c whether they are standing still in space, or standing still in time. Trignometrically, c is the hypotenuse of everything.
@@bbbl67 If "everything is going at c" it just makes any talks about any speed or acceleration rather meaningless. I don't think this is what we discuss here.
Does gravity bend the path of a Neutrino in a similar way that it bends light? This could account for an ability of a neutrino to travel faster than a photon because the photon travels further due to a gravitational path diversion yet the neutrino travels in a straight line. This could theoretically prove that faster than light speed travel for an object with mass is possible 🤔
no, it means they have less energy. same as the photons from the cosmic microwave background--they're still traveling at the speed of light, but their wavelength has been stretched out immensely by the expansion of the universe. (which is why, even though they started life as extremely high-energy gamma rays, they're now the cosmic *microwave* background.)
@@nemlehetkurvopica2454 nah, but he has a point, bc a neutrino theoretically DOES have a rest mass. i honestly don't know the answer, although it could be that their mass is so small that the slowdown is so small as to be imperceptible.
Can`t neutrinos travel at any speed as long as it is slower than light? For example, in Beta radiation, electrons and neutrinos (anti) can have any combination of energies, therefore different speeds for each combination.
A neutrino. Knock, knock. Who’s there?
There or somewhere? Did you collapse a wave function?
They don't even knock.
@@nowster THE Neutrino: You clearly don’t know who you’re talking to, so let me clue you in. I am not in danger, Paul. I am the danger. A guy opens his door and gets shot and you think that of me? No. I am the one who knocks!
@@thingsiplay Heisenberg.
People didn’t understand this joke.
I love how her excitement for this subject matter is so strong the pupils of her eyes feel no need to interact with her eyelids. It's great! :)
After watching tons of these videos, I now can follow them much more easily. Hard work pays off.
Thanks Doctor Duffy and Jessica, keep up the good work.
The Bonny Lass has a charming accent! Makes her easy to listen to.
Yay, it's Dr. Duffy! I learned something new and I hope to see more videos from you!
My favorite channel on RUclips
An excellent video on this very exciting topic. It was the first explanation of the neutrino oscillations I've heard that helped me to somehow grasp the idea of them switching flavour as we observe them.
I believe we observe them as one flavor. (They could be any flavor based on probability but when we observe them, they are a single flavor.)
@@shawn0fitz Wrong! There are 3 flavours and we observe them all!
😄 Fascinating and informative as always, thanks!
The first bonus fact has greatly knocked me around. No acceleration in the massless photon I could appreciate, but how does a massive (even when tiny) particle have no need at all of acceleration?
When a neutrino is born, the way Standard Model describes it, is you have an event (a node in a Feynman diagram) with 3 operators working: annihilation of a W- boson and creation of 2 new particles: an electron (or tau or mu) and a neutrino. It's an instant event, and total momenta of outgoing particles must match momentum of original particle, so they are born with that momentum (and speed) they carry away. This is very similar to the case with photons that are also born with a certain momentum and speed.
Oh, thank you. But - and forgive my casting aside the Feynman diagrams - the photon borrows exclusively from space at the total expense of time, whereas the neutrino answers to the clock. I guess what I'm asking now is: how can the quintessentially temporal find the exemption necessary to by-pass acceleration?
@@TheyCallMeNewb it doesn't have to "by-pass acceleration", it's not a little ball that's born stationary (relative to what?) and then accelerates. Remember how in QFT particles are really waves, parts of quantum fields. One field loses a wave, another field gains a wave, and this wave evolves in time so it looks like it's moving with certain speed. How fast it moves depends on its shape and the governing law of its evolution. If it's born with proper shape, it already has the necessary speed / momentum, no need to accelerate.
I had availed myself of an idea the likes of which I perhaps shouldn't. We dabble in fields, and as such Heisenberg maybe channeled. The neutrino is characterized by a wave packet synonymous with among other things, the 'speed' that maybe measured. That really burgeons for me that whole 'wave/particle duality' component. The thinking is helped along by time tending to parse out the neutrinos by type in accord with respective speed. Updating schema; and thank you.
Great video as always
Three questions on neutrinos:
1. Why does the oscillation of masses not violate conservation of mass? Does this mean that different mass neutrinos travel at different speeds?
2. Is there a CMB equivalent in neutrinos? Have we/can we observe it?
3. All neutrinos are left handed. But they travel slower than the speed of light. If we travel faster then a neutrino will it appear right handed?
Since neutrinos travel slower than the speed of light, you can define a reference frame that travels faster than them. From that reference frame a left-handed neutrino would appear to be a right-handed neutrino. I'd be interested in a video on this.
Why would we need a video on this? When you see me run away from you sitting in your parked car, you see me carrying my phone in my left hand. Because I'm a lefty. But when you drive past me and look at me in the rear-view mirror, you see the image of right-handed person. You do the transformation in your head to know I'm left-handed. Because you know how mirrors work. Why would it be any different for sub-atomic particles?
Maybe I'm wrong but neutrinos are only supposed to be left handed. This would violate that rule.
@@jonwesick2844 That was believed when it was thought they moved at the speed of light. Your original comment is correct, though: neutrinos.fnal.gov/mysteries/handedness/.
In the rest frame of the particle that decays to produce a neutrino, the new neutrino is left-handed. In other frames of reference it might not be.
@@PhysicsPolice because right handed neutrinos don't exist. A right handed neutrino might be the anti particle of left handed neutrinos though.
@@XEinstein your @ me but I don’t know which part of my comment you’re replying to. It’s already implied in my comment that neutrinos are only left handed. Making them look right handed by looking at them in the rear view mirrors makes for a great hep-th paper but not a good RUclips video. Feel free to disagree. It’s just my opinion. But I explained it clearly, and you haven’t given me any reason to reconsider it.
Very informative and nicely condensed
You misspelled "condescended" ;)
@@PhysicsPolice In some ways you are right ;)
Excellent and informative!
Love this series!!
Thank God someone finally answered the question of what we know about the mass of the neutrino. That 2011 experiment was supposed to have something of an answer on that, but then the FTL neutrinos stuff hit and drowned out anything to do with the actual mass of the neutrino because it wasn't attractive to most people.
I'd argue for the possibility that their mass is actually infinitesimal or >0 and less than any measurable mass. It would make the people who insistented on massless neutrinos effectively correct and incorrect. Their speed would also be infinitesimally close to the speed of light, making decoherence impossible.
Don't we measure the neutrinos from a supernova first because they travel unimpeded, and light has to make it through a bit of gas first?
I think we have a lower bound on the difference in the masses of two of the mass eigenstates.
And therefore, a lower bound on the largest of the 3 masses?
Can we talk about Dr. Turner's accent for a second? I love it.
Mind blown again... Thank you!
I gave a genuine question for anyone who happens to know the answer. Background: The "speed of light" is short for "the speed of light in a vacuum". Light slows down in materials like glass and water, and it's possible to go faster than slowed-down light in a material, hence Chenerkov radiation. My question: While photons are slowed down in such a medium, do they experience the passage of time?
Hi, please can you do a comprehensive video about atomic orbitals, proton spin and quantum leap. I like the way you do such complicated topics in physics, so it'll be much of benefit if you discuss the aforementioned requests since they're mind spinning especially when read in articles 🤕
Really interesting video this time. They usually are of course. Thank you. So, if a photon experiences the entire timeline at the same time, using the speed estimate with 18 nines, how long have those big bang neutrinos been travelling (according to their perspective).
My math is probably wrong, but I came up with about 16.5 years.
Ignoring universe inflation, I get the separation in time between a light photon created at 15 billion years ago and a neutrino to be close to a quarter of a second difference between them. Which would mean at the math I have, and I might have missed a decimal or two, 4.7 years, maybe? That's how old the neutrino would think it is since the birth of the universe... And that's using the 18 nines and a five... I'm more certain about that than the difference in arrival time, I'm kind of doing this from the top of my head and it's late at night, it's also a year later) apparently I also suffer from some time dilation)) I'm curious to find out why I got such a different number than the post above me, did I make a massive math mistake???
When a neutrino/photon is created, what causes it's direction path to travel this way or that?
How about a series of videos on different long baseline experiments 😇
That was delightful.
I'm digging Jessica, like on an existential level.
Jessica has good taste in art!
How many wavelengths long is a photon? Just one wavelength or multiple?
Why can't the universe just be simple and easily grasped?
Because Neanderthals didn't go extinct. They evolved into physicists. A simple universe would imply that we exist just because we exist. By .making it complicated, such as Einstein and his relativity nonsense, it allows for the existence of a god - intelligent design - to make it all happen.
As you can see, none of these Neanderthals want you to know the truth otherwise you wouldn't follow and obey their Lord Jesus Albert Einstein.
F=ma. Mass and Acceleration. Space and Time.
E=mc. Mass and Acceleration. Space and Time.
Since mass is just energy with an Acceleration factor < c, Acceleration equals Acceleration. Energy equals Energy.
The universe is defined by its Acceleration value. Everything is an energy field with one field being accelerated by another energy field.
As you can see, the human race needs a god to justify their existence. By making the universe mysterious and difficult to understand, it allows for a supreme being to make it all happen.
So, how sure are we that photons travel at c? If the only clue to neutrino's mass is oscillation, then photon's lack of oscillation is not exactly a proof that it doesn't have, for example, the same mass as neutrino.
Great video, thanks ladies.
*Measuring Neutrino mass / energy / velocity*
A strong electric field can separate a Hydrogen atom into proton and electron pushed into opposite directions due to opposite charges.
A reverse field can push them into each other causing electron capture ? It turns a proton and electron into a neutron and neutrino.
It may be easier to leverage conservation laws (of momentum and energy) to compute the mass, energy and momentum of neutrino than to measure it experimentally when it's already 1 light-second away from the lab.
If mass is given by a particle's interaction with a field, does it just ATTEMPT to go at the speed of light and sort of zig-zag back and forth with the field waves/particles along the way?
Is that oscilation back and forth at light speed the timer that causes time dilation for objects traveling at different sub-light speeds?
@@thedeemon Thanks, I'll have to give that a good read.
As for time dilation, (even if just for context for my odd comment) I had seen an example somewhere using a photon bouncing between two mirrors inside a spaceship would appear to an outside observer to have a zigzag path, the faster the craft, the longer each bounce in the zigzag and the longer/slower each would take at the speed of light. . .
. . . here the image came to mind that other particles' "internal zigzags" being represented as a bunch of faynman diagrams chained together where the distances between each appear to stretch for an outside observer as the particle goes faster, slowing the rate of any particle decay or other interactions.
(that's what was going on in my head, anyhow)
@@OldGamerNoob makes sense, yes
I really love these videos! Q: Can low-energy slow neutrinos be created ab initio, i.e. slow neutrinos that are slow without the need for decoherence or traveling a fantastic distance? Also, I presume that neutrinos created at the big bang slowed down a lot during the inflationary period. Can scientists estimate their number and account for the gravitational effects of that neutrino "residue"? Thanks again!
There's a conserved quantity called lepton number which more or less mandates that for every electron (muon and tau too but these are rare enough) there's an anti neutrino and vise versa for antiparticles. Unless this conservation law is massively broken at the dawn of time, there should only be as many (anti)neutrinos as there are electrons, which would hardly amount to any noticeable mass
@@bottlekruiser I hadn't thought of that. But antineutrino/electron and neutrino/positron creation would still result in "left over" neutrinos if the electrons and positrons annihilate and if a neutrino is its own antiparticle. What do you think?
@@tedlis517 heck you're right
I totally didn't think of that
They *could* have annihilated with each other too, but i bet the cross section of that is so small it might as well not happen
A way to test that could be looking for em radiation in places where it's not supposed to be
OK so the neutrino form Andromeda arrived here 40 µs after the photon. But it would also be interesting to know how much time passed for the neutrino? 🤔
40 microseconds?
Man I love Even Bananas.
How ironclad is the case for neutrino oscillation requiring rest mass? Like are there alternative theories where neutrinos travel at C but still produce the observed oscillations? If so, how seriously are they taken?
As solid as special relativity. The fact that they oscillate requires that they have a speed less than c. Think of each flavor as a state. Each state will have several durations. All of those durations are defined by times. In order for the neutrino to be affected by time requires a speed less than c. I'm not an expert so I would do some reading up on it if you are really interested.
It's like a signature that only gets read once both receive.
I have a question, due to length contraction wouldnt the "experience" of a photon be that its source and destination are also same place?
Yep - due to special relativity, the photon "sees" a cosmos that is "squeezed" to zero length in the direction from the source to a static observer. So if you ask the photon itself, it'd tell how it got created, traveled, and hit the observer all in the same instantaneous moment.
Yep! And they experience the events of their creation and annihilation simultaneously, too. It's weird being a photon. Even weirder to be a CMBR photon sailing uninterrupted for thirteen billion years through empty space, then all of a sudden some jerk puts a radio antenna in your path.
@@PhysicsPolice I guess that from the perspective of a photon we are the weird things in the universe bothering with time all the time
3:23 that's a lot of denial to german speakers
LOVE UR VIDS
The most intuitive way to explain how or why a particle like a photon (or electron, etc) might behave as an uncertain location particle while also like a polarizable axial or helical wave ''packet'', given that everything in the universe from electrons to solar systems are in orbit with something else pulling them into polarizable axial or helical apparent waves depending on the orientation of their orbits as they travel thru space, is that they’re in orbit with an undetectable dark matter particle pulling them into polarizable axial or helical apparent waves as they travel.
And given that we know we’re in a sea of undetectable dark matter but don’t know where it’s disbursed, we can imagine that they’re in orbit with an undetectable dark matter particle pulling them into polarizable axial or helical apparent waves as they travel where the speed of their orbit determines the wavelength and the diameter is the amplitude which would explain the double slit, uncertainty, etc. No?
Say, this was surprisingly accurate.
Is the speed of neutrinos an inherent property? Is it possible to have slow neutrinos, or is it just impossible to detect them unless they have a lot of energy?
Anything not moving at the speed of light in a vacuum is stopped in some frame of reference (its own). Subluminal velocity is always relative. However, neutrinos are always produced moving very fast in the frame of reference of the particles that created them.
@@christosvoskresye is right when it comes to velocity being relative. You guessed correctly that slow neutrinos are very difficult to detect.
But they're also relatively uncommon. Neutrinos carry "missing" momentum from certain quantum interactions. Because the typical magnitude of this missing momentum is large compared to the neutrino's tiny mass, their typical velocity is near the speed of light. Yes, as far as we know, the constants that define these interactions are fundamental properties of nature. Like the mass of an electron, speed of light, Plank's constant, etc.
Neutrinos are interesting little particles.
I have a question: If you infer that neutrinos must have mass because they experience time (because they oscillate "change"), why shouldn't that same argument hold for light? A photon sent from a far away galaxy loses energy (redshift). So the photon "changes", too. Ergo: A photon experiences time and should have mass...
That's not part of the narrative and discredits the foundations scientology was built upon.
A photon has mass. You can argue that's how gravity can change its path, if you think gravity is a force (special vs general relativity). What a photon doesn't have is "rest mass". The stretching of space does steal energy from a photon, over very great distances, so its mass is also reduced, but its rest mass remains zero. This is an example of how a universe that is expanding (or contracting) does not perfectly conserve energy. This is all pop-science oversimplification, of course.
The way I read this is, because different neutrino flavors have slightly different masses, they have slightly different wavelengths (everything is a wave as well as a particle). The difference in wavelengths means the probability of interacting with any superimposed component of the waves should vary over time, at very slightly different rates for the superimposed neutrino types. This is not pop-science as much as it is speculation. It would be interesting to read a reaction from someone who understands the math better.
the best test might be the supernova SN 1887A. neutrinos arrived on earth only slightly before the flash of light,. neutrinos sped through the body of the collapsing star while the photons diffused and were slightly delayed the light. neutrinos traveled slightly slower than light. Adjusting fir this proved that they do have mass and put
an upper limit on their mass.
You will definitely win a staring contest against anyone, even the sun!
Great video and well presented. You are a good narrator and your story line was interesting, engaging and informative. Well done!
they change wave length when they changes color. So can the wave length actually be speed then?
The wave length of light can change which does not affect the velocity. However because of the slight mass of the neutrino a change in the wave form must also imply a change in velocity, but completely undetectable by current technology.
Correct me if I'm wrong. But I think you're asking if different flavors (not "color") of neutrino have different mass states. Yes, if this were the case, it would have implications for their momentum and therefore velocity ("speed"). Check out their other video "How do neutrino oscillations work? | Even Bananas 10" about 4 minutes in. For some reason neutrino mass state does not correspond to neutrino flavor. Weird, huh?
So no, I don't think they change speed.
We often hear about the result of something traveling near the speed of light. I.e. That 2.5 million lightyear journey going by in an instant from the perspective of the neutrino. What puzzles me is the experience of the neutrino during that time.
For a more down to Earth example, let's say you're in a vehicle that is traveling a significant fraction of the speed of light in a large circle so that you can always keep a single landmark in sight. Ignoring things like the effects of g-forces liquifying your body, or boiling away from air friction, what would you see? Would that landmark appear normal until you stop, would you see it deteriorate rapidly as if watching a sped up video, just see a blur, or something else?
What do you mean by "you can always keep a single landmark in sight"? Is it in the center of the circle, or somewhere very far?
If you ask "what would you see", it's best not to use Lorentz transformation, and just use the constant speed of light and Doppler effect. Imagine light spreading from the object at constant speed in waves, and you intercepting these waves.
If you move towards the object, it will appear greatly blue-shifted. If you move left, it appears more to the left, and so on. Plus the object ages quickly, since you move through spacetime faster along the time direction than that object.
@@PhysicsPolice You may want to rename yourself, as your name suggests deep knowledge of physics, where there is very little.
In this case, you can ignore acceleration and use piecewise linear path, with pieces having zero length in the limit.
@@PhysicsPolice This question does not require general relativity, as there is no gravity involved.
Twin paradox does not require general relativity to explain.
Again, you show little understanding of physics.
@@PhysicsPolice You're just repeating yourself. Special relativity deals with high speeds and acceleration just fine. In fact, a circular track is a famous example where special relativity is used. You can view the circular track as some funny gravitational field that points outward, and you sit still in your car, and the gravitational time dilation would be the same as from special relativity. But then you need to have the landmark rotate around you at superluminal speeds, which hardly gets you anywhere. Switching rapidly between inertial frames along the track gives immediatelly correct results. Momentarily comoving frame of reference does not have a wikipedia page, but it's still a thing.
For twin paradox, it's quite obvious that gravity plays no role there.
Obviously, the connection between gravity and general relativity escapes you, which leads us back to my first comment.
I wonder, what distance (by our reference) neutrino can travel for plank time by neutrino's clock? And how often does it oscillates by its own clock?
(1) Something travelling at or very near the speed of light e.g. a neutrino travels about one Planck length per Planck time. By definition.
(2) Good question! I tried to find the answer, but unfortunately I'm out of my depth. I hope someone else can chime in... I'm curious now, too.
Excellent presentation, easy to follow/understand. Thank you both. Cheers
Great video
The duality that I see with Neutrinos having mass and, thereby, the effect on the momentum vs. if Neutrinos oscillate between having mass and not having mass. So a neutrino leaving a supernova or jet of a blazar can arrive at roughly the same time as the photons do, so 99.9999% of the time, the neutrino travels at the speed of light; therefore, photons do not pass inside a vacuum. Instead, the neutrino oscillates for a tiny fraction of a second and can change its form or interact with matter.
I am basing that on neutrinos associated with the photons coming from a supernova or blazar. If either of those is traveling away or even toward us, that creates a momentum problem that doesn't exist if it oscillates.
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Here is my fundamental problem. A neutrino is created in the infall of matter produced in a supernova. How fast is it traveling relative to the matter that made it, and how fast is it traveling relative to us?
To the matter that created it, the neutrino is traveling at 99.99999995% the speed of light. Now, how fast is the matter traveling away from us? Let us say the matter is traveling at 3% of the speed of light. Then, the neutrino relative to us would be traveling 3% + 00.00000005% the speed of light, or 3.00000005% the speed of light.
Now we calculate when a neutrino should arrive at the earth vs. when a photon would arrive at the planet. Over extremely long distances, the time would change dramatically.
That is vs. a neutrino that is traveling 99.999999995% the speed of light for a picosecond, five maybe ten times over a billion + lightyears. We wouldn't even notice the difference between the photons and neutrinos arriving.
I don't understand this now! Most basic particle physics tells us that individual lepton numbers are conserved no matter what, but now if suppose in a negative beta decay we get an electron and an anti electron neutrino, if here we consider the superposition, so does that mean that neutrino produced can be anyone among electron muon and tau? How does one then impose the lepton number conservation?
"a photon experiences all of the universe's timeline at once."
What weighs more, a pound of neutrinos or a pound of feathers?
Imagine a tornado of Neutrinos, then imagine what would happen if you stood in the middle of it. Right at the apex.
Based on the Fun Fact at the end, where the speed of light (photons) through a non-vacuum is less than the absolute vacuum velocity C, neutrinos keep chugging along at so close to C that for practical purposes it is C because of their non-interaction with matter. That implies that photons leaving Andromeda could arrive at Earth *after* the neutrinos due to their (photons) occasional and subtle interactions with the mass present in space (gas atoms/molecules, microscopic ice grains, dust grains, etc.) in exceedingly small quantities but which also sum to something more than insignificance due to the vast distances travelled, and also the electromagnetic fields that they interact with. Would that be so?
Follow-on: So, if neutrinos have a crazy-small amount of mass, then the focal point for an observer viewing a distant galaxy via an Einstein Ring would require a subtly different focal point using neutrinos compared to photons?
Nice. I have one question, is it possible that a neutrino and an anti neutrino ahnihilate each other? I know there're a lot of anti neutrino from beta decay and the sun bombard us with neutrinos, yes, I know it would be a very rare interaction, but would yiled a very specific radiation, we should be detecting it, right? Or it's so rare that they would hit one another?
Yes they should if they ever meet each other.
Has it been ruled out that neutrino oscillation is not externally induced? Such that it would not require them to be slower than C?
I'VE ASKED THE FOLLOWING ON SEVERAL PHYSICS SITES, WITH NO LUCK:
Photons always travel at c and express this regardless if you travel toward or away from the source. The energy difference is expressed in a frequency shift.
DO NEUTRINOS TO THE SAME THING?
if they dont interact with other matter or else, are neutrinos then the only entity in the universe that travels on straight lines thru timepsace and therefore does the most accurate measuring of distances?
That’s mind blowing! If photons experience time as being none linear. Do they experience the past timeline of the universe, or the past and also the future? Could it somehow prove/disprove pre-determinism?
If a car is moving and it carries a broken clock that doesn't tick, does it prove anything about predeterminism? Time not ticking for photons is in a way similar to a broken clock, photon still moves through time in our reference frame.
If photon traveling through space, encounters clouds of gas or dust, it will be slowed down, by a tiny bit, so could the neutrino get to Earth first?
Yes, this is very much possible. We discuss this idea when we examined supernovae in this episode: ruclips.net/video/fgjynaQxVNE/видео.html
Do neutrinos get absorbed (somewhere somehow) at the same rate as they are being created? If not, then that means that the number of neutrinos is growing constantly. => The sum of the mass of all neutrinos would also grow over time. Dark matter = gigantic clumps of ancient, cold, coalesced neutrinos? ;-)
So do neutrinos experience refraction travelling through matter?
Well, I think my brain exploded
Fascinating.
My question is: are they Neapolitan, and, which flavor order are they left-to-right in the half-gallon-sized carton?
I understand that it is necessary that a particle be massless to travel at lightspeed.
i.e. If lightspeed, then massless.
But, I have also heard the contrapositive: that is necessary that a particle travel at lightspeed if it is massless.
i.e. If massless, then lightspeed.
Why? Why is this contrapositive true? Is it true?
Yes, wavefunctions for massless particles are waves that travel at c. From relativistic wave equations we get that when m=0, k = w/c, and group velocity is equal to phase velocity v = w/k = c.
en.wikipedia.org/wiki/Weyl_equation
en.wikipedia.org/wiki/Group_velocity
Are the different flavours of neutrinos at the same speed?
No, but close
@@sunquake is that related to them being slightly different massif?
@@blueredbrick right
This question could mean at least two different things.
(1) Do neutrino flavors have different masses and therefore different velocities for a given momentum? Not quite. There are three neutrino mass states, Each with different likelihoods of interacting with matter as an electron neutrino, a muon neutrino or a tau neutrino. But it's not as simple as one flavor being heavier than another.
(2) Do different neutrino-producing interactions result in different mean average momenta for the resulting neutrinos? Yes. And these different types of interactions produce a specific kind of neutrino. So when you detect a neutrino, it's momentum gives a small hint how it was produced.
Next topic: neutrino mass hierarchy
Neutrino mixing angle
How is Nutrino Formed? How Photon get Pragnent?
Nutreemo is mostly fromed in space and other such places
Nutella is made in Italy.
@@christosvoskresye with no palm oil
There is something here I have never understood: light in a medium travels slower than the speed of light in a vacuum, and it can change frequency, depending on just what it resonates with in the medium. It seems that neutrinos moving slowing the speed of light and changing flavor is not sufficient proof they have mass as the same mechanism could be at play.
*facepalm* I hadn't thought of why they can't be traveling at the speed of light. Is decoherence just theoretical/hypothetical or can/has it been measured?
I LOVE Jessica's accent 😍 (I could enjoy listening to her speak about neutrinos for hours ... or even physics in general ... or toothpaste, groceries, math, etc 😆)
The answer to the question "is X *just* theoretical?" depends on your beliefs. Models in physics tell us what is real, according to some theory. To believe a theory is to believe all its model's parts are real. The scientific method doesn't prove theories true. It's a process that allows us to find models closer and closer to the truth. You can believe the most time-tested, accurately measured theories, like QM or GR. Or not. That's up to you. If you believe in QM then decoherence is real.
Every observation of the macroscopic world is consistent with decoherence. So yes, it's been observed, if you believe QM. I think you're asking can it be quantified. Yes, if you search for "quantifying decoherence" in the arXiv, you get plenty of results. Most are specific to one small regime because decoherence is complex and good methods of quantification it depend heavily on the system of study.
So, since it takes a photon no time to travel from the Sun to the Earth, to the photon the Sun and the Earth are in the same place. As are all other things in the Universe.
With gravity wave travelling at the speed of light, couldn’t the speed of neutrinos be measured during neutron star mergers ?
What arrives to us first, pre cosmic microwave background neutrinos or the cosmic microwave background?
Yes.
That's a good question and I had not thought of the Cosmic Neutrino Background as a thing before. There is good sources online including one on Wikipedia which states the CNB or CvB came into existence ONE SECOND after the BB. en.m.wikipedia.org/wiki/Big_Bang#Cosmic_microwave_background_radiation
The CMB did not occur until temperature reduced enough to allow protons to bind with electrons to form hydrogen. This did not occur until 380,000 years later!!
When electrons joined with protons they entered in a high level energy state and thus in a higher orbital. When transitioned to a lower energy state and thus lower electron orbital they released a photon. This began the CMB which has shifted red because of the expanding universe.
So now guess which arrived first the neutrino or microwaves?
That's much like asking which arrives first, sound from 5 seconds ago or sounds from 1 second ago? Parts of the world are, say, 342 m away from you, and parts are 5 times that distance. The time when you hear a sound depends both on how far away the sound originated, and also when the sound was made.
It's the same with neutrinos.
Hi Kristy (and fellow bananas, sorry had to type that :) ), It seems quite fundemental that nothing can be faster than the speed of light (in vacuum), c. Even neutrinos cannot beat that. But that is not what i am curious about. An observed phenomenon is Charenkov radiation. As i understand it, it is radiation by particles seemingly faster than the speed of light through a medium. Can neutrinos do this as well? Can they cause this kind of radiation? Or don't they interact?
Yes, you're right. We discuss briefly how T2K uses the SuperK Cherenkov detectors to study neutrinos in this episode: ruclips.net/video/QpnSmb37t00/видео.html
Neutrinos appear to have mass. Mass affect light’s speed. And cause light to bend. Could neutrinos be responsible for light’ bend when passing next to a start instead of gravity? Could density of neutrinos be responsible for light bending toward center of a black hole? Could neutrinos be responsible for speed of light as we observe it?
Neutrinos always travel at just below the speed of light regardless of their origin; what exactly provides the force to accelerate them?
Neutrinos can travel at arbitrary speed afaik since they have mass?
Can this hypothesis has possible evidence: Time can be explained relative to energy i.e., imagine at relativistic speed a region is created
of the energy (potential) due to that
less energy is transmitted for the observer outside the region. This indirectly explains that time can be rate at which observer observe the energy?????
A photon traveling from a distant star undergoes a red shift and a corresponding loss of energy. Does a neutrino undergo anything similar?
yes, the same process should apply
@@thedeemon how so? I don’t think it’s (Compton) wavelength changes. What is the corresponding effect?
@@Bdix1256 it's the way metric tensor affects wavelengths - it doesn't care whose wavelengths it elongates as it expands spacetime.
If an observer where to travel at the same speed as a neutrino , would that neutrino be stationary relative to the observer ? In other words why are these particles associated with any particular speed ?
At those speeds if you could come up with a method to capture them, the deceleration may cause a pretty big energy release. Possibly better than solar panels, and working in storms.
Zero mass times the speed of light squared equals zero energy.
The problem with this, as Dr. John Bacall of Princeton pointed out, is if this were true we wouldn't have been able to observe any neutrinos from Supernova 1987a...
Quantum spin is even-dimensional. Mathematically it is described as four dimensional with two degrees of freedom. Even dimensional spin is orientable, which means it remains the same chirality no matter how it is observed.
Another thought provoking video. Thanks!
OK, so a Neutrino has mass.
That means it can be deflected by gravity.
Does their coherence get affected by travelling towards or away from a large mass?
How does gravity affect the speed?
A photon is also deflected by gravity
Actually the photon is not affected by light directly. It is space time that is changed by gravity. Thus there is the appearance that gravity is affecting the path that light takes.
@@michaeldeierhoi4096 I assume you meant that a photon is not affected by gravity. Well, you can apply the whole "gravity is an illusion" argument to massive particles, too.
@@michaeldeierhoi4096 Straw man. John said, "deflected by gravity" which indeed happens indirectly. Don't say "Actually" like you're correcting him when you're not. And no, there's not just the "appearance" that gravity is affecting the path that light takes. Gravity is *actually* affecting the path that light takes.
@@christosvoskresye Exactly. I suspect Michael is confusing Newtonian gravity with GR. Because photons have zero rest mass, they experience zero force from Newtonian gravity. But in GR the paths of all particles, regardless of their mass, are affected by "gravity" i.e. the metric tensor.
How do we know how often neutrinos bump into each other?
Insurance records.
It sounds like you may be curious about how neutrinos interact with other neutrinos. We actually don't know the answer. The Standard Model predicts neutrino self-interactions at a level below current experimental capabilities to measure. I recommend you check out a paper called "Neutrino Self-Interactions: A White Paper" published this year.
If neutrinos don't need to accelerate, then that would make them massless like photons. Does that mean that they start out as massless, and then eventually run into a Higgs boson and then acquire mass briefly? Would that explain the neutrino's ethereal flavour changing and mass changing? It only interacts with the Higgs field briefly, during which time it: slows down, changes mass, changes flavour, etc. Then during the rest of the time it just travels along at the speed of light where it has no mass, has no flavour, passes through everything, etc.?
no, that doesn't make them massless. It just means a neutrino is born having a certain momentum and speed, all particles are also waves after all. Particle creation operators in QFT can produce particles with any given speed, no acceleration from zero is necessary.
@@thedeemon Yeah, but why would a particle get born at any other speed other than the speed of light?
@@whiteman2707 mathematically - a wave's group velocity is determined by its frequencies in time and space, and for non-zero mass case they are related such that the velocity is less than c. en.wikipedia.org/wiki/Klein%E2%80%93Gordon_equation
Philosophically - why would it be born with speed c, why not anything else. It seems there's no good argument either way.
@@thedeemon Of course there is a good argument for why it should be born at c, rather than any other speed, because c is the speed of causality in the universe. Everything is going at c whether they are standing still in space, or standing still in time. Trignometrically, c is the hypotenuse of everything.
@@bbbl67 If "everything is going at c" it just makes any talks about any speed or acceleration rather meaningless. I don't think this is what we discuss here.
Is that a kandinsky painting?
Does gravity bend the path of a Neutrino in a similar way that it bends light? This could account for an ability of a neutrino to travel faster than a photon because the photon travels further due to a gravitational path diversion yet the neutrino travels in a straight line. This could theoretically prove that faster than light speed travel for an object with mass is possible 🤔
Could neutrinos be the elusive gravity facilitating particle?
Does neutrino have a favor of direction to travel?
So, if a neutrino from the *big-bang* loses energy over time, doesn’t that mean that they’re moving more slowly?
no, it means they have less energy. same as the photons from the cosmic microwave background--they're still traveling at the speed of light, but their wavelength has been stretched out immensely by the expansion of the universe. (which is why, even though they started life as extremely high-energy gamma rays, they're now the cosmic *microwave* background.)
@@evilotis01 but less energy with same mass means less momentum, so lower speed is expected. (see Dirac equation and Klein-Gordon equation)
@@nemlehetkurvopica2454 nah, but he has a point, bc a neutrino theoretically DOES have a rest mass. i honestly don't know the answer, although it could be that their mass is so small that the slowdown is so small as to be imperceptible.
Can`t neutrinos travel at any speed as long as it is slower than light? For example, in Beta radiation, electrons and neutrinos (anti) can have any combination of energies, therefore different speeds for each combination.
pound for pound? Since you are talking mass would it not be dyne for dyne or newton for newton instead?
Are neutrinos a physical object?