Daniel and Kelly’s Extraordinary Universe - Do neutrinos get redshifted?

Episode Date: June 27, 2024

Daniel and Jorge talk about what happens to neutrinos as the Universe expands.See omnystudio.com/listener for privacy information.

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hey daniel is it true that everything gets stretched out as the universe expands that's what the physics tells us so far yeah So is that why I feel so tired all the time? Because I'm getting stretched thin. You know, I think physics is always your first scapegoat, isn't it? But this time it's kind of true, right? I mean, each day, my gym gets a little bit further from my house, right? So it is making it harder to stay in shape.

I mean, physics is telling you that the universe is getting stretched out, but it's not physics's fault. Don't blame the messenger. Well, he could have kept quiet. Maybe we wouldn't have noticed. And that's the end of the podcast. Physics keeps quiet. That's a bit of a stretch, though.

Hi, I'm Jorge. I'm a cartoonist and the author of Oliver's Great Big Universe. Hi, I'm Daniel. I'm a particle physicist and a professor at UC Irvine. and I want to hear the message from physics, whether it's good news or bad news. Really? You want to know if like the Earth is about to blow up or if a supernova is about to engulf us in flames?

I definitely want to know that, but that's not bad news. It's bad news for me and for the human race, unless you know something we don't know, Daniel. No, I'm thinking much bigger. You know, cosmic bad news is stuff like, oh, the universe is inaccessible to you or there's lots of dimensions to the, the universe we can never see or the universe will never be understood.

That's the kind of philosophically cosmic bad news I'm afraid of. Oh, my goodness. Really? That keeps you up at night? Absolutely. Yeah. This whole project of physics is based on the assumption that the universe follows laws and that we can figure them out somehow with our tiny little brains. Who knows if that's even true? Well, so what's the physics version of a horror movie? Just some scientists coming up and telling you, you're never going to know anything

no no the physics horror movie is the aliens arrive they explain the universe to us and we just can't get it we're like huh what try again and it just never works or the aliens come

and then you ask them what are the secrets of the universe and they go I'm not going to tell you see you later no exactly they won't serve man But anyways, welcome to our podcast, Daniel and Jorge Explain the Universe, a production of IHeartRadio.

In which we dive bravely into the task of explaining the universe whether or not it is explainable or understandable. We think it's at least worth trying to make sense of everything that's happening out there in the cosmos, from tiny little particles screaming through space nearly the speed of light to massive black holes, gobbling up everything that they can. All the way from the tiniest particles to the largest phenomena, we try our best to understand the universe to wrangle it into some mathematical sense and to explain all of that to you.

That's right. We ponder the entire universe and we wonder what it would be like to be out there in space traveling the far reaches of the cosmos, maybe getting stretched out by relativity or by the expansion of the universe and hopefully expanding and stretching your mind in the process. The whole project of understanding the universe means fitting it into your skull.

means making it makes sense. The first step of that is to figure out what the laws are of physics. What are the rules that everything is following? And then thinking about whether that clicks together. What happens when I apply those rules over here or over there? Are they really universal? How does that connect with this other idea I have? A lot of physics is just trying to stick these puzzle pieces together.

Right, right. So then the engineers can be like, hey, can we break that rule? Can we push the limit there? What's going to happen if we try? The bridge is going to collapse. That's what's going to happen. And that's why I'm glad I'm not an engineer. Because you're not building bridges.

You're just burning them. I'm burning mathematical bridges. But when I make a mistake, nobody dies. Oh, really? It seems kind of dangerous to be near a particle collider. I mean, there's a lot of security around those. Yeah, that's true. And that's why we rely on accelerator physicists to build and operate those things.

Maybe that's why they don't allow me down there. Yeah, probably not. But we aren't doing our best to develop the most universal laws of physics we can, ones that apply to everything under the sun, including all the different kinds of particles that come to us from the sun. Yeah, because the sun is constantly spewing out not just a lot of light and warmth and energy for us to enjoy and to use, but also it's also spewing out a ton of other things, particles and lots of different kinds of radiation, right?

That's right. All the stars out there in the universe. are pumping out photons, but also a solar wind made of all different kinds of particles, protons, neutrinos. And we talk a lot about what happens to those photons as they move through an expanding universe from galaxies, moving away from us at very high recession velocities. But we don't as often apply those same questions, those same rules, to the other particles being emitted by those stars.

So today on the podcast, we'll be tagling the question. Can neutrinos get red shifted? Now, Daniel, when you talk about the solar wind, do you say wind in the sense of like a nice, breezy summer wind or do you mean it like a fart? Like the sun breaks wind? Kind of neither of those. Are those the only two options available?

Can I get an option C, please? Nobody's ever out there in space. Like, hmm, I'd like some more solar wind, please. I'm overheating. That's never happened. Yeah. It's not refreshing out there in space. No, I guess it'll cook you.

Yeah, I guess if I have to pick between those two, solar wind is more like a fart because it's kind of unpleasant and dangerous and you want to be as far away from it as possible. Right. Yeah. It's stinky as well. You know, people joke about what space smells like and it is partially due to the solar wind, but it's also just due to trace other particles.

that are out there that, like, adhere to the outside of a spacesuit on a spacewalk, which then volatilize as you come back inside. People say it smells like barbecue out there in space. Whoa. And not just because they're cooking in that radiation. Yeah, that's right. Now, if your farts smelled like barbecue, then, I don't know, I guess you'd be more popular at parties. If you fart on the space station, you would not be popular up there.

It's a pretty close environment. But it must happen. Hmm. Sounds like a podcast episode, Daniel. Sounds like a question for Zach and Kelly, since they're an expert in everything unpleasant in space. I'll ask her next time she's on. There you go.

There you go. What are the physics of farts in space? Like how quickly would it dissipate? Or like if you're out there and you smell without a helmet, would you die first or would you smell the fart first? Or could a really stinky fart cause an international incident on the space station, which leads to World War III in the end of humanity? You've heard of the butterfly effect?

now we're talking about the space fart effect Wow, geez, it's a dangerous place, space Now bring this back to neutrinos Is it like in space no one can hear you fart or What if your farts were all neutrinos? Here we go, I'm bringing us back to the topic Oh, you're trying to bring it, all right, all right Do neutrinos smell bad also or do they have a neutral smell?

Yeah, another question is whether neutrinos have a color and whether you could consider them being red-shifted or blue-shifted. All right. I can tell you're trying to get us back on track here. This is a physics podcast, not a fart podcast after all. But farts are physical. Dang it, sorry. Are you trying to ignore part of the physical universe?

I retract that comment, and I respectfully request we get back on track. So, yeah, are neutrinos farts of the sun? That's the question today, right? The question is whether neutrinos can get redshifted the way we know that photons can. Oh, right, right. All right, all right. Yeah, it's an interesting question.

Can a neutrino get redshifted? Because, you know, the word redshifted we usually apply to light, not neutrinos. Yeah, that's right. But if these laws are universal, if the same rules apply to everything, then you can ask the question, and this is what some listeners have asked me,

whether the same rules apply to neutrinos from distant stars as they do to photons from those stars. Does that mean that the rules also apply to farts? Can fars get redshift? All right, all right. Well, as usually, we're wondering how many people at there had thought about neutrinos and whether or not they can get red shifted. Thanks very much to everybody who answers questions for this session. recommend of the podcast. If you'd like to hear your voice for a future episode, please don't be shy. Write to me to questions at danielandhorpe.com. So think about it for a minute. Do you think

neutrinos can get redshifted? Here's what people had to say. No, they're not in the electromagnetic spectrum. I think yes, neutrinos have like a proton, a waveform and if there's an accelerating body coming from there, they can really shift it, I think. I assume this is to do with quantum mechanics and how particles have a frequency. Redshift, that just means the frequency gets stretched, I think. So I guess, yeah, it can happen. I don't know how or why. I don't see why not, but I know the problem with them is that they're just so hard to see.

They seem to pass through just about everything. And I know there's a few different kinds, so I guess, yes, they could. but how would you detect that, I'm not sure. All right. Well, some pretty interesting answers, sort of in the range of, why not? Who knows? Yeah, some people saying, yeah, they're a particle like everything else. Other people saying, no, that only applies to photons and things in the electromagnetic spectrum.

All right. Well, let's dig into it, Daniel. Let's recap, first of all, what is a neutrino? Neutrinos are some of the weirdest and most fast. fascinating particles in the universe because they're sort of like an extreme example of what the universe can do you know most of the particles we're familiar with corks and electrons feel a bunch of forces corks feel the strong force and the electromagnetic force and the weak force electrons feel only the electromagnetic force and the weak force they don't feel the strong force they're neutral in the strong force neutrinos are like one step further they're saying hey i'm going to be neutral also in electromagnetism i'm going to only feel the weak force. So we have examples of particles that feel all three quantum forces, the quarks, an example of particles that feel two of the quantum forces. Electrons feel electromagnetism and the weak force. And then an example of a particle feels only one of

those forces, just the weakest one, the weak force. So neutrinos are particles that are out there in the universe that we can just barely sense, barely interact with, because the only way they interact with us is through the weakest force we know about. Right, right, but they can still exist, right? Like they're still made out of a real energy in this universe so you can make them. They just sort of ignore us and won't talk to us in the ways that most other particles talk to us. Yeah, exactly. And remember that all of these particles are just ripples in fields and these fields are all on top of each other.

The way to think about these interactions is whether the fields can transfer energy back and forth. The neutrino fields couple very, very weakly to all these other fields. So it's sort of like having another universe on top of us that we can just bear. interact with. Even if all sorts of crazy stuff is going on, even if there's huge numbers of them and enormous amounts of mass and energy and velocity, we just barely sense it. So it's almost like having a parallel universe right on top of us. And you know, the even more extreme would be dark matter. Dark matter we think might be a particle that feels none of these forces. And so it's on top of us, but we only sense it gravitationally. So neutrino is like almost the extreme

limit of that. But you're right. They are energy. They're part of our universe. and they even have mass. We know the neutrinos are not like photons and other massive particles. There is a little bit of stuff to them, an incredibly tiny amount of stuff to these neutrinos. And now do neutrinos feel gravity? Do we know that?

Everything with energy feels gravity. Absolutely. Gravity is universal. You can't have energy and not feel gravity. Because remember gravity... But have we seen that? Have we seen neutrinos like a bend by the path of massive things?

Oh, yeah, great question. We can't observe neutrinos well enough to see their path bending, but we know something about the mass of neutrinos and the number of neutrinos, and that affects the overall curvature of space and time. And we can see their impact in the early universe and its curvature. So we know the neutrinos have energy, and that energy does contribute to the curvature of space time. Yeah.

But we haven't seen one bent to gravity, have we? We have not seen them move an occurred path, no. But we know that their energy contributes to, the curvature. Interesting. And is there sort of a perspective on why some fields or why some particles interact with some forces and not others? Or is just sort of how the universe was made or how these particles turned out to be?

You know, like is there, is it like a parameter in the equations that is just kind of random or what? Yeah, it's a great question. Is there an explanation or is it just descriptive? Currently, it's mostly descriptive. Like we say that quarks have a strong charge and electrons don't because we see that electrons ignore colored fields. We say that neutrinos don't have an electric charge because we see that they don't get accelerated by electric fields. So that's sort of what we mean by that.

It's just a description of what we see in these particles do. We do notice a bunch of patterns. Like all the quarks have the same kinds of charges and electrons and muons and tau's all have the same electric charge and this kind of stuff. So there are definitely some patterns and some structure there, but we definitely do not understand it. It's just descriptive. It might be explained by some future theory physics that tells us what all these particles are made out of, some quiz bits and whatnots that have fundamental pieces to them. And when you put them together in certain ways or they interact or oscillate in certain ways, you get the particles that we see with their various properties. But currently we can't explain it.

We're sort of at the stage of the periodic table 150 years ago where we see all these elements with these different. properties, but we don't understand why they have that nature. And you mentioned there's sort of like ghostly particles, but I feel like that maybe understates because there's a huge amount of neutrinos going through us right now, right? There's like bazillions of them going through our bodies as we speak. Yeah, that's right. Neutrinos hardly interact with us, but there's no shortage of them because the sun produces an incredible number of neutrinos.

Every fusion reaction produces neutrinos. And it also produces photons, but those photons are mostly absorbed by the sun. Like the sun is opaque to most of the photons it produces. So those photons are reabsorbed by the sun and it generally heats it up. People talk about the photons we see on Earth as having been produced infusion. Technically, that's not really accurate. The photons produced infusion heat up the sun and then the sun glows as a black body or because its atmosphere is hot.

Those are the photons we see. But the neutrinos are different. The sun is transparent to neutrinos, the way basically everything is transparent to neutrinos. So if a neutrino is made at the heart of the sun, it flies out and goes through the earth, and we can observe it directly from that fusion process. And there's a huge number of them passing through our bodies. And it's like a billion neutrinos per square centimeter per second. Yeah, it's huge. And none of them are interacting with us, or are they a little bit, maybe a little bit dangerous?

like are some of them maybe knocking on some of my DNA maybe some of them are definitely interacting with you but it's a tiny tiny number to give you a sense of it like we have many fewer muons passing through our body every second like one per square centimeter per minute but every single one of those is interacting with your body like when a muon hits your body it's like a tiny bullet it's hitting those atoms and it's depositing energy mostly they're not doing damage they don't hit anything important and you're fine because they're just these tiny bullet but every single muon does interact with your body. But for neutrinos, most of them do not interact with you.

So for scale, the neutrinos were discovered in an enormous tank underground. We're talking about like thousands and thousands and thousands of liters of liquid run for a year to see like one neutrino bounce off of one of those particles. So neutrino interactions with our kind of matter are extraordinarily rare. So yes, they are interacting with us because it's a huge number, but it's a tiny, tiny fraction. of the neutrinos that are created and a tiny overall number of interactions compared to like the muons and other particles that are interacting with you.

Now, are these the ones that you can see in some science museums where they have like a little chamber of water vapor and you see the traces? Are these neutrinos or am I thinking of something else? Those are mostly muons. Yeah, cloud chambers which you can see in science museums and you can actually build at home in your garage without too much trouble. I got an email from a listener who was inspired by a comment I made a year ago and she and her son built a cloud chamber in her garage and they saw muon tracks so those are mostly muons neutrinos you would need to build an enormous underground chamber of like xenon or something in order to see one neutrino and you wouldn't see a track you'd see the neutrino bumping into a normal particle and you'd see the

recoil of that particle you can never really see a track of neutrinos because that would require multiple interactions of the same neutrino which would be astronomically unlikely you only ever see like one interaction one push from a neutrino muons go through the roof of your garage. Oh, yeah, muons can go through rock also. You can see muons when you're underground. That's why they build the neutrino detectors so deep underground to shield themselves from all the muons,

which can penetrate through meters and meters of rock. Now, neutrinos are not just ghostly, but they're super duper fast, right? Because they're so low mass. They're going almost at the speed of light all the time. Yeah, neutrinos have a tiny, tiny mass, much smaller than even electrons, which means when they're produced,

If they have even a tiny smidge of energy, they're basically going at the speed of light, very, very close to the speed of light. Can you slow them down? Like, could you ever hold a neutrino in your hand? Yeah, you could slow neutrinos down because they do have mass. They can exist at zero velocity, unlike photons. Photons, there is nothing to them if they have no velocity because they are just velocity. But if you slow a neutrino down, it has mass, right? Mass means rest energy.

So you can be in the same reference frame as a neutrino. you could like catch up to a neutrino and look at it or equivalently you could slow a neutrino down and hold it in your hand, yeah. Pretty cool. All right, well now the question is do neutrinos get redshifted as the universe expands? And so let's get into what red shifting is.

Can it happen for neutrinos and does it make them smell like farts? Or maybe not. Maybe we won't get to that in time. But let's give it a try. We'll dig into that. But first, let's take a quick break. December 29th, 1975, LaGuardia Airport.

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All right, we're talking about neutrinas and whether they can get redshifted as the universe expands. So those are all a pretty interesting concept there in one sentence. Let's start with red shifting. What is red shifting? In a sentence, red shifting is when a wave gets a longer frequency because it's being emitted by something that's moving away from you. So all waves have frequency like sound waves. The sounds you're hearing from us have certain frequencies. You have low frequencies and higher frequencies and all that kind of stuff.

We can describe sound as waves and we can measure the number of times the wave waves per second. That's its frequency, which is inversely proportional to its wavelength. So longer wavelengths, lower frequency. It sounded like you're trying to hit like a high C and a low C there, Daniel. That's sort of like a very low C and a less low C. That's all I'm capable of. That was my falsetto. A low and less low.

You can't do falsetto? That was my falsetto. Oh, that was your false. I think you can do better. I'm going to rely on our sound editor here. Corey, can you make this sound like a high sea? Just get a helium balloon there. You don't need special effects.

Chipmunk, Daniel, yeah. I think I've seen a video of you had Morgan Freeman, red shifting his voice or blue shifting his voice with a helium balloon. That's amazing. So red shifting is, and whenever any kind of wave gets stretched, out basically, right? It becomes a lower frequency, which means bigger wavelengths. Yeah, and shift there just tells us that we're changing something. And red shift means we're changing it to be more red. And red is on the long wavelength, low frequency end of the visible

spectrum. So when we say we're getting longer wavelengths or lower frequency, we talk about red shifting. And the opposite is blue shifting. If you're making something higher frequency or shorter wavelengths, you're making it bluer. So red shifting just means you're extending the wavelength, you're lowering the frequency. Right, right. Although I have to say, I feel like you're kind of cheating a little bit here because I don't think I've ever heard anyone used to phrase red shifting or blue shifting when it comes to anything except light waves.

Like nobody ever says, can you give me a blue shifted C note or a redshifted, you know, D note? You know what I mean? Yeah, that's true. We apply red shifting mostly to astronomical objects and mostly aspirational objects and mostly astronomical stuff we see with photons so that's why it's applied there but you know if a police car is passing by you as it's driving towards you the wavelengths are shortened and as it's driving away from you the wavelengths are lengthened and so you could call that blue shifting and red shifting in that case we call it the doppler effect right yeah exactly the doppler effect

nobody calls it the red shifting or blue shift but police cars have red and blue lights so maybe somehow i don't know dot yeah yeah yeah i figure if i create it I'm just trying to throw a bunch of random ideas at you to distract you from the fact that you're right about this. Well, I think what you're trying to get at is that, you know, anything with a wave, it can get stretched out or it can get shortened, right? Like anything, a sound wave, an ocean wave, anything like that can increase or decrease in frequency. And for light, that usually means that it's changing color,

which is where the name red shifting and blue shift. shifting come from. That's right. And because we're normally applying it to astronomical stuff, you know, light from distant galaxies. If that distant galaxy is moving away from us, for example, we say that it's red shifted and the light from that galaxy looks redder than if that galaxy had not been moving away from us. And if an object in the sky like Andromeda is moving towards us, its light gets blue shifted. And you're right that it applies to the wavelength of the light and also applies to the color of the light as we see it, if it's in the visible spectrum. And it tells us something about the energy of that light, because for light, the wavelength is very closely

connected to the energy. Like redder light is lower energy, and blue or light is higher energy. Right. And this red shifting and blue shifting of light out there in the universe happens, not just because things are moving away from us or towards us, but also because the universe is expanding, right? Yeah, and these are actually two different ways to talk about the same phenomena. You can get confused and think, oh, there's two red shifts happening, one that the universe is expanding and it makes all wavelengths longer than the other, the galaxies are moving away from us faster and faster, and the Doppler shift is making their light redder. Those are actually two different ways to think about the same phenomenon. What's happening there is that your description

depends on your frame of reference. If you think about the whole universe in a single frame, like we're at the center and everything is moving away from us, you're measuring the velocity of those galaxies relative to us, then you can use the Doppler story to describe what's happening. But instead, Instead, in a more general relativity sense, you say, well, you can't really put everything into a frame because the universe is expanding and space is curved between here and other galaxies. What you really have to do is imagine every galaxy in its own frame and space increasing between them. And in that picture, there is really no relative velocity because every galaxy has no velocity in its own frame. So what happens to the photons as they go from galaxy to galaxy is the expanding space between them is doing the work of expansion. It's a good example of how you can build physics in lots of different ways.

You can start from a few different axioms and end up with a different description of the same physical process. Right. But it is two separate effects, isn't it? Like one is just from its motion and the other one is from the expanding of the universe. No, it's two descriptions of the same thing. Like in the expansion of the universe model, there is no relative velocity. In fact, that's more accurate because you can't really talk about relative velocity across the whole universe. That's also why you ended with sort of nonsense.

sense answers like those galaxies are moving away from us faster than the speed of light because you're making measurements across two different frames where space is curved between them. Right, but I feel like there are sort of two effects there that can maybe add or subtract, right? Like if there's a galaxy really far away from us that's maybe spinning, for example, then sometimes they'll be moving away from us and sometimes it'll be moving towards us. So there'll be a shifting of the light because of that. But then also it's really far away, which means. that on top of that, there's going to be some sort of redshifting due to the long distances

getting longer and longer. You can add more layers to it, certainly. Like, you can add not just the fact that these galaxies are moving away from us or equivalently that space is expanding between us, but that also within those frames, there is some motion relative to the frame itself. So as you say, galaxies are spinning. And that spinning is what we call peculiar motion relative to the frame of the galaxy, which is moving with the center of mass of the galaxy.

And you're right that moving relative to the center mass of the galaxy can cause an additional redshift or blue shift. So that really is a separate effect. The rotation of the galaxy does add another contribution to red shifting and blue shifting. And we can see that in distant galaxies and we can use it to help measure their rotation. Right. So there are two effects, right? The expansion of the universe and the recession velocity of an entire galaxy are two equivalent ways of talking about one effect. The rotation of a galaxy does add another effect, yes.

You're right that there are multiple contributions to the redshift, the motion and the spin. But if you're thinking in the relative velocity point of view, they're both just contributing to the relative velocity. So it's two contributions to one redshift effect, not two different effects. So how do we measure all of this red shifting that's going on in the light of the universe? Yeah, it's really tricky because you can't stop the galaxies, right? Or like go to the galaxy and measure like it's light that you would measure if you were right there next to it. So you have to sort of imagine what light you think the galaxy was emitting in its own frame and then compare that to what we're seeing.

Fortunately, galaxies are filled with objects we pretty much understand, stars, et cetera, and those are following physics that we pretty much understand. So we have a pretty good way to predict the light we think a galaxy should be emitting and then we can compare it to the light we're seeing from the galaxy and we can tell that it's shifted. And specifically, the frequency of the light from these galaxies has a few, specific handles in it, like a fingerprint, where we can tell that it's been shifted along. Like we know that atoms tend to emit light at very specific narrow frequency ranges that correspond to the energy levels of the atoms. As an electron jumps down one energy level around

hydrogen, for example, it tends to emit a photon with the specific energy of the gap between those energy levels. And so if we see light from a distant galaxy and it has a huge spike close to that energy level but a little bit shifted, we can say oh, that's probably from hydrogen. It's just shifted a certain amount in the red or in the blue. So these like standard candles help us understand how

the light is shifted from these distant galaxies. Right. It kind of goes to that idea that stars have a sort of fingerprint to them, like the light they emit have a very specific pattern of them in the frequency spectrum that you can sort of identify what's in the star or what it's supposed to have.

And so if you see that fingerprint kind of it's mirrored, then you know that it's redshifted, right? But then I think you can also just generally tell, right? Because the light from the things around us is mostly, you know, a certain color. But I imagine that as you look out into the universe and things are further away from us, things just look redder. Yeah, but that's how we can tell the distance to things by measuring the redshift. Because there's a correlation between how far away things are and how quickly away from us

they're moving. Then you can use the redshift. as a measure of distance. Now you have to calibrate that as we have a whole episode about the cosmic distance ladder to calibrate these things. But generally, things that are farther away are moving away from us faster.

So if you measure the redshift of an object, you can tell how far away it is or how old that light is. But there can also be a lot of uncertainty on those measurements because the wider, the spectrum you measure, like the more of these fingerprints, the more of these atomic lines,

these spikes that you identify, the more accurately you can measure. this redshift. This is why, for example, when you point multiple telescopes at different frequencies at the same galaxy, you can get a better measurement for its redshift. Like James Webb recently saw some galaxies that were like crazy weird far away. Those numbers came from the redshift numbers, which were pretty uncertain because James Webb didn't have a chance to do a broader spectrum and Hubble hadn't looked at it yet in a different spectrum. And so that's why sometimes when you follow up with more measurements, you can get more

handles on the light from that galaxy and that revises the redshift measurement which tells you how far away this thing really is right but I guess what I'm saying is that that's kind of if you want to get really granular and know exactly how much the red shifting is but I wonder and I'm asking if there's a kind of a general effect that anyone could affect with their naked eye you know most of the stars that we see at night are in our galaxy so I imagine they're not very redshifted so all the light we see from our stars look white or yellowish but if you were to look at the rest of the sky that the things are not stars and generally the light we'll see

from that is redder. Yeah, that's exactly right. And that was Hubble's experience, right? He looked up in the night sky, he saw a bunch of stars, but he also saw these smudges that people thought, oh, those are just like clouds or nebula or whatever within our galaxy. But then by calculating the redshift and by understanding the relationship between redshift and distance, he was like, oh my gosh, look, these things are redshift. That means they're super duper far away.

There are actually other galaxies. So the Redshift gives us that like third dimension to the night sky. Rather than just seeing like a screen, it gives us the ability to project that into the third dimension and understand the depth of the night sky. Right. Or I wonder if you just put on like infrared glasses, right? Or use an infrared camera, you'll sort of see more of the rest of the universe, right? Yeah, exactly.

And that's why James Webb, for example, is an infrared telescope. They're like, let's focus on the deepest, reddest light in the universe. universe because that's from the most distant objects the things we're seeing from the early universe. That's why you build infrared telescopes, exactly. Right, right. And if you get really mad, then you'll be seen red until you'll be opening your eyes up to more of the universe. No, no, not a valid theory. Yeah. I mean, if somebody farts really badly at your astronomy party, that can make you see red also, yeah. Yeah, yeah. Or in your space station.

The universe, the cosmos will open up to you. December 29th, 1975, LaGuardia Airport. The holiday rush, parents hauling luggage, kids gripping their new Christmas toys. Then, at 6.33 p.m., everything changed. There's been a bombing at the TWA terminal. Apparently, the explosion actually impelled metal glass. The injured were being loaded into ambulances, just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged, and it was here to stay.

Terrorism. Law and order, criminal justice system is back. In season two, we're turning our focus to a threat that hides in plain sight. That's harder to predict and even harder to stop. Listen to the new season of Law and Order Criminal Justice System on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. A foot washed up a shoe with some bones in it. They had no idea who it was. Most everything was burned up pretty good from the fire that not a whole lot was salvageable. These are the coldest of cold cases, but everything is about to change.

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Listen to America's Crime Lab on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. I had this, like, overwhelming sensation that I had to call it right then. And I just hit call. Said, you know, hey, I'm Jacob Schick. I'm the CEO of One Tribe Foundation,

and I just wanted to call on and let her know there's a lot of people battling some of the very same things you're battling. And there is help out there. The Good Stuff podcast Season 2 takes a deep look into One Tribe Foundation, a non-profit fighting suicide in the veteran community. September is National Suicide Prevention Month, so join host Jacob and Ashley Schick as they bring you to the front lines of One Tribe's mission.

I was married to a combat army veteran, and he actually took his own life to suicide. One Tribe saved my life twice. There's a lot of love that flows through this place, and it's sincere. Now it's a personal mission. Don't have to go to any more funerals, you know. I got blown up on a lot of. a React mission. I ended up having amputation below the knee of my right leg and a traumatic

brain injury because I landed on my head. Welcome to Season 2 of the Good Stuff. Listen to the Good Stuff podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. Hola, it's HoneyGerman and my podcast, Grasasas Come Again, is back. This season, we're going even deeper into the world of music and entertainment with raw and honest conversations with some of your favorite Latin artists and celebrities. You didn't have to audition? No, I didn't audition. I haven't auditioned in, like, over 25 years. Oh, wow. That's a real G-talk right there.

Oh, yeah. We've got some of the biggest actors, musicians, content creators, and culture shifters, sharing their real stories of failure and success. You were destined to be a start. We talk all about what's viral and trending with a little bit of chisement, a lot of laughs, and those amazing Vibras you've come to expect.

And, of course, we'll explore deeper topics dealing with identity, struggles, and all the issues affecting our Latin community. You feel like you get a little whitewash because you have to do the code switching? I won't say whitewash because at the end of the day, you know, I'm me. Yeah? But the whole pretending and cold, you know, it takes a toll on you.

Listen to the new season of Grasasas Come Again as part of My Cultura Podcast Network on the IHartRadio app, Apple Podcast, or wherever you get your podcast. Well, now the main question we're asking here today is whether neutrinos can be redshifted, which, again, I feel like it's a little bit of a cheat here because it depends on whether you only apply the word redshifting to light, which is kind of what some of our listeners brought up. So maybe let's settle that right now, Daniel. Are you expanding the definition of redshifting to things that are not light?

I see. That's a fair question. I hadn't even thought about that. To me, redshifting applies to all sorts of waves. even the Doppler effect. Like when that police siren is coming at me, I think of that sound as blue shifted. I see how blue there implies something about visual light,

but to me it's a more general meaning and just that it's changing the frequency. Right. But I mean, like if an ocean wave got, you know, a higher frequency, you wouldn't say it got redshifted, like nobody would understand you. If it got a higher frequency,

I would say it got blue shifted. Yeah, I think that's pretty cool. Blue shifting ocean waves. Awesome. I'm going to start saying that everywhere now. It wouldn't get bluer, right? Or like, you know, a high C note isn't bluer than a low C note. It's sort of a subtle thing.

But some of our listeners did say that the answer is that it cannot because neutrinos are not light, so therefore they can't be redshifted. I see that. That's a fair point. I take blue to just mean it's changing in that direction of the frequency. You could extend that argument even further and say, like, well, that only applies to visible light because invisible light isn't getting bluer or redder, even if it's frequency is shifting. So what's the answer here for the people who said neutrinos can be redshifted

because they're not light? I think we should consider red shifting, blue shifting more generally to refer to changing the frequency of the waves. Okay, so just for today, we're going to go against what most people consider the English language. I think that's the accepted meaning of red shifting and blue shifting. And I think we're just going to consider the question of whether the wavelength of a neutrino can change as the universe expands. So according to Wikipedia, which is just just looked up. In physics, a red shift is an increase in the wavelength and corresponding decrease in the frequency and energy

of electromagnetic radiation such as light. So, hmm, that's interesting. So even Wikipedia disagrees with you, Daniel. Yeah, interesting, yeah. Some subtle wrinkles in the definitions here. Okay, so then officially, according to Wikipedia, and, you know, most humans who speak English. English. The answer to our question is no, neutrinos can get redshifted.

If you define redshifting to only apply to photons, then yes. Yeah. If you disregard language, then anything can be anything. But basically, I'm saying the listener who said the answer is no because neutrinas are not light, then they are partly right. Yeah, they're partly right according to that definition. I'm surprised to have to make the argument to you that like, you know, language can be evocative of broader themes and deeper ideas that we find patterns of across the universe and across phenomena. But, you know, to me, I think the interesting part of the question is like...

You mean, you're surprised that you have to be clear about what you call things in physics? You're surprised by that at this point, five years in? Yeah, I should have learned that. Should have learned that. Well, okay, so let's just say the answer is no. Neutrinos cannot get redshifted because I think even Wikipedia agrees that it applies to light only.

but it's still an interesting question to ask whether neutrinos that are traveling out there in space do their wavelengths get stretched out by the expansion of the universe? Do they get shifted to longer or shorter wavelengths? Yeah, do their wavelengths get stretched or squeezed as the universe expands? So let's tackle that question. I agree, that is an interesting question, yes.

Okay, so then it happens to light because the universe is expanding, right? So as it's traveling, it's having to travel through more space as it goes along. Is that why it stretches? Just because it's sitting in space and space is being stretched, its frequency gets stretched. Yeah, it's the second one. Space itself is getting stretched out. And radiation gets stretched out differently than like matter does.

You know, electrons sitting in space, you stretch out the space. You still have one electron. And now you have more space. So you have less matter per volume, right? Things get diluted in a certain way. The same thing happens to radiation. one photon in that volume, but that photon's energy also decreases because the wavelength of that photon also changes.

Right. So then the question is, do neutrinos have a frequency or a wavelength? Yeah. So in this sense, you can think of all particles as ripples in some field, right? And those ripples have frequencies. Like we talked to Matt Strassler about this recently. And you can imagine electrons as having like a standing wave, which is an oscillation in a field and a traveling wave, which is like the motion of the electron.

Through that field, photons only have a traveling wave because they have no mass. Wait, there's two kinds of waves. A traveling wave and a standing wave? What's the difference? Like, do electrons have both waves? Yeah, the electron field can do both. The electron field can just oscillate in place in a certain way. And that's what a stationary electron is.

That's why electrons have mass. An electron field can also ripple in a direction, right? That's a traveling wave. Don't think of it as two waves. It's the same wave. It's just that electrons you can see standing still, in which case they're just doing the standing wave thing. Or you can see them moving, in which case it's also a traveling wave. But that depends on your frame of reference, right?

Now, for photons, you can't see them standing still because there's no frame of reference in which they're at rest. They're always traveling waves. When things have a standing wave, are those waves actually rippling or are they more like probability waves? These are ripples in a field, which some people think is a physical thing, right? And so these should be thought of as like actual oscillations in a physical quantity. People think the field is real and it's out there. That's sort of a question of philosophy. This is separate from like wave functions and probabilities, which are in an abstract probability space.

These are ripples in real space of what we think is a real physical thing. Whether or not it's actually happening, whether you can observe it and what happens when you take measurements, et cetera, there's a whole other question in philosophy. But we think these are physical ripples. of a field, it's actually oscillating. And so they're different than the quantum probability waves, right? Yes. Okay.

Now, what does it mean that an electron is rippling in place? Like, it's jiggling, it's energy is increasing and decreasing and pulsating, or what does it mean? If it's standing still, because it's not moving. Well, as we talked about with Matt Strassel, you can think about the wave is sort of like the way you think about a string oscillating, right? A guitar string can oscillate in place as a standing wave. What's happening there is it's oscillating between. kinetic and potential energy right it gets distorted has more potential energy and then it comes

back and has kinetic energy and it sloshes back into potential energy so the same way the electron field could oscillate between having kinetic and potential energy so the value the field is changing at some values that has more potential energy some values that has less potential energy but more kinetic energy so that energy is conserved within the field it's just oscillating back and forth between kinetic and potential energy the way like a ball inside a glass can roll around If you ignore friction, it could roll around forever. It's like oscillating within the glass. Or I guess I'm imagining like a balloon sitting in space.

It's maybe squashing and stretching in different directions, right? That means it's energy is going between the potential energy and kinetic energy as it squeezes and compresses. But then how is that different than traveling waves? In order to do this special trick of oscillating in place, you have to have mass. Mass is the thing that allows you to do that. That's really what mass is. is the ability to store energy in one location within the field.

Because remember that mass is just like a measurement of internal stored energy. But some fields can't do that. Like the photon field doesn't have any mass. There's something the electron field can do that the photon field cannot do. But the photon field and the electron fields can both have traveling waves, which is like a wave moving through space. You have an oscillation here and then the oscillation is over there. And the oscillation is further along.

So it's sort of like that energy is moving through the field rather than just staying in place. Okay, now let's say for an electron doesn't mean that the electron is physically like going up and down as it moves or as it's moving in a straight line, it's somehow undulating. What exactly is a traveling wave for a particle like the electron? Yeah, well, it sounds like you're trying to hold in your mind simultaneously. The picture of an electron is a little particle that has a definite location and you're trying to marry that with the idea of a wave. But instead, just think about the electron as a fluctuation in the wave. And as we talked about recently when you think about like how photons ripple, photons are not undulating, they're not

moving side to side. What's changing along a straight line is the value of the field along that line. A field's pointing in one direction and then another direction and then a third direction because the photon field is actually a vector. It's not just a number, it's a direction. So for the electron, again, moving along a straight line as an electron moves, what's changing is the value of the electron field along that line. It doesn't like wiggle sideways in any way, except Sometimes when we draw this on paper, we draw sideways wiggles to indicate the value of the field. But in a physical sense, there's no sideways undulation. It's just like the numbers of the electron field are changing.

The electron field is not as complicated as the photon field because it's a fermion and not a spin one boson like the photon is, which is a full vector. Well, I'm just following what you said, which is that, you know, like an electron has a standing wave, like a standing ripple. And then it has a traveling wave. but you can also imagine a standing wave that's moving in a constant speed in a straight line that doesn't need a traveling wave or is the traveling wave

basically a moving standing wave? Yeah, that's what a traveling wave is. And it maintains its shape, right? One of the cool things by particles is as they move to the universe, they maintain their energy. They don't like diffuse and spread out, right? Because it's a minimum oscillation of this quantum field

so it can't go down to a lower value. You can't have like a half an electron then a quarter electron. So this shape maintains itself as it moves through the electron field. So then I wonder if maybe the question you're really asking here today is whether the standing wave of a neutrino

gets stretched out as the universe expands. Like you don't even need a neutrino to be moving. You can just have a neutrino standing in space out there. And as the universe expands, does the neutrino standing wave also expand? Like are those two the same question? They're not quite the same question because now you're talking about particles at rest and because the neutrino field and the electron field

and everything else that has mass has a specific frequency at which it can oscillate that isn't affected as the universe expands what is directly affected by the expansion of the universe is not the frequency but the wavelength that's always stretched out for all particles for photons which only have a traveling wave the wavelength and the frequency have a very simple relationship longer wavelength lower frequency. For electrons, which also have mass, it works in the same direction, but the relationship is more complicated because of the mass part. The mass part isn't affected directly by the wavelength, but the expansion still influences the overall frequency and that frequency is also affected by the mass part. So as the universe expands, it stretches out the wavelength, which does

in the end lower the electrons frequency, but the math is a little bit different. There's a minimum frequency for the electrons that they can't lose because they still have mass. This effect really only changes how particles move through the universe, not how much mass they have. All right. So then if we're asking the question, do neutrinos change wave lines as the universe expands? What exactly does that mean? Does that mean that its standing wave gets stretched or its traveling wave gets stretched?

But then you just said that it's traveling wave, it's just its standing wave moving in a straight line. So I guess I'm confused what you mean by a neutrino's. wavelength getting stretched by this expansion. There's two different kinds of things that these fields can do, right? They can oscillate in place some of them and they can also oscillate in a traveling wave motion.

And so for those who you want to know more about the technical details of that, go back and check out our episodes at Matt Strassler about exactly what that means. For the purposes of today's episode, we just need to think about the motion of those particles, the traveling waves and the frequency of those particles as they're moving.

And for photons, for example, we know that they get stretched out. If you see something being emitted from a high velocity object, or if the universe is expanding between you and them, really the same effect described in two ways. And so the question today is like, does that also apply to neutrinos, which we know are generated by stars far away and fly to us across space?

Does the expansion of space also affect them? And the answer is yes, absolutely. Their wavelength is also shifted as they move through space. Because everything is just a ripple in these fields. And other than the mass ripple, which controlled by some fundamental properties of the field, the velocity of it reflects the energy of that particle, and that decreases as space expands. So what does that mean for a particle like the neutrino?

Is it going to look different, or is it going to end up looking or being a different particle when it reaches the other side of the universe? Yeah, it means that it has less energy, right? It doesn't change its fundamental nature. It still has the same mass, just like an electron will always have the same mass. It still looks the same. It still looks the same, but it has less energy. the same way a photon does, right? When a photon gets red shifted, it has less energy than it did before.

When the universe expands, photons lose energy, which is sort of fascinating. Then violates our intuition that, like, energy should be conserved. But it isn't for photons, right? Photons get lower energy. We have a great example of that, which is the cosmic microwave background radiation, which is very, very red photons. They're down in the microwave. But when they were emitted back in the very early universe, they were very high energy because they were emitted from a super duper hot bright gas and as the universe is expanded they've been stretched out to very low energy

so the same thing happens to neutrinos and electrons and every other particle moving through the universe as the universe expands or equivalently again if you're emitted from something moving at high speed away from you and those particles are red shifted to lower energy same mass but lower kinetic energy so wait wait are you just basically saying that the expansion of the universe

slows down neutrinos? Yes, absolutely it does. And it's a really interesting point because photons don't get slower, right? They just get lower energy at the same velocity because photons are always moving at the speed of light. But neutrinos have mass. And so as they get lower energy, they do get slower.

They're basically always traveling at almost the speed of light anyway because their mass is so small. But yes, technically they do get slower as their wavelength gets longer. Right, right. So then what's the difference between neutrino that I detect from the sun, which is really close to us, and a neutrino that is emitted by a sun really far away

that gets to us after billions of years and it's been going through expanding space. When it gets to me, and I compare it to the neutrino from our sun, do they look the same? It's just that one of them is going faster than the other, or are they going to look different? Well, each individual neutrino will not look different, but the spectrum of them will.

So if you measure the energy of all the neutrinos from the sun, you make a graph of that. It's going to have some distribution. And then if you measure the energies of neutrinos from distant stars, stars that are really far away from us where the universe is expanded between us and them, those will have a lower energy distribution. Exactly the same way it is for photons. Photons from distant stars are shifted down lower in energy.

Neutrino energy distribution should also be shifted down. So they'll just be slower. Yeah. So, I mean, basically you can ask this question of anything, any particle, it doesn't have to be neutrinos. Yeah. So like an electron that is shot at us from really far away, by the time it gets to us, it's going to be going at a slower speed. Yeah, or as we say colder or redder, but yeah, fundamentally it's a lower velocity.

Right. I mean, you can say smellier or two. But I think in a practical sense, you would just say it's slower. Yeah, it's definitely slower. It's less kinetic energy. Ah. Wait, so that means like if I was Superman or if I was shot out of a cannon from a, uh, from a, uh, space station in orbit around Earth

and I was flying through space nothing gets in my way no does nothing I would still slow down eventually to a standstill depends on what you mean by standstill because there's no absolute velocity in space right and I think that this slowdown is a relative effect

so you would asymptotically approach zero velocity relative to some observer but yes things do get slowed down as the universe expands yeah like initially I would see planets whizzing by me but then eventually at the end of the universe planets would not be whizzing by me

that would be going slower relative to them yeah and remember that this is a relative effect right one person will see a photon redshifted somebody else see that same photon not redshifted so this is a frame dependent effect right but it's basically as I just described like initially things will be whizzing by me but eventually things will be going by me slower

I'm not 100% sure about the thrust of Superman here but if he only has initial velocity and that he's coasting. Forget I said Superman. That's why I shifted to a canon. Like if I get shot out of a cannon. Now, does that mean that our whole episode here today, instead of calling it, can neutrinos be redshifted?

If they, we could have just called it, do things in space get slowed down by the expansion of the universe? In the end series, yes. Except for photons. Photons get redshifted, but they don't get slowed down because they have no mass. They're always traveling at the speed of light. Right.

But light is not a thing. basically does anything with MAZ things matter and get slowed down as the universe expands and it seems like the answer is yes. The answer is yes, but it's very difficult to see because in order to detect that, to do the experiment I mentioned, you'd need to have a source of neutrinos with very specific energies.

And because we see so few neutrinos, it's so difficult to pin them down to observe them, we can't actually do the experiment that I talked about earlier, like looking at the distribution of energies of neutrinos from a distant star. And also, stars don't emit neutrinos at very specific energies the way they do photons, right? And so we don't have like spectral lines of neutrinos that we can use to measure these red shifts. But the only thing we can do is look for the cosmic neutrino background, which is similar to the cosmic microwave background.

We think there were a bunch of neutrinos created in the early universe, very high speed, very high energy, and the expansion of space has cooled them all down to much slower moving neutrinos, still nearly the speed of light, but much slower moving. If we can measure the cosmic neutrino background and basically measure their velocity, their energy distribution, that would be direct evidence of seeing particles slowed down by the expansion of the universe or redshifted neutrinos, but we haven't seen that yet.

I wonder if there's maybe an easier experiment you can do. Can you look at other particles that are getting to us from far away? Can we just tell that they're somehow slower than the particles that are being sent to us from closer sources? or is there no such thing? It's difficult because we're talking about particles and particles don't make it through the universe the same way photons do.

So it's harder to attribute individual particles to specific extragalactic sources. We're talking about like electrons or protons from another galaxy. We have very small number of those. Those are very high energy cosmic rays and we have lots of questions about what's even making those.

So no, we don't have a good sample of electrons or protons from other galaxies to do that kind of experiment with. would you even need to do the experiment just because that's what relativity says it's going to happen, right? Things are going to slow down as you move through expanding space. And we already know that a lot of relativity is true. So why wouldn't it work for this case? Yeah, we have no reason to think it wouldn't, but it's always a good idea to double check because there could be a surprise. It could be one of those things where like, yeah, that's totally

going to be boring, go out and do it, yawn, yawn, yon, oh my gosh, what? And the universe tells us something new. So we strongly suspect and believe that this is what's happening, but you always got to check this stuff. Right, right. You're saying it's a good idea to shoot Jorge out of a canon space. Good idea, bad idea, I don't know, but we could learn a lot. Yeah, yeah.

Although it would be hard because, you know, to make it a perfect experiment, as I'm flying through space, I can't eject any matter because it would ruin the experiment, right? Mm-hmm. Yeah, so if you farting, yeah, you spoil the experiment. I see where you're going with that. Just trying to bring it back around or down, as the case may be. So if we do an experiment, the person can fart, right? That's right.

You've got to hold it in. Hold it in. Hold it in for billions of years. Hold it in for physics, man. I feel like that just describes my job here in the podcast. Holding it in or not hold it in. Hold it in. I don't think you've been holding it in.

You've been letting it all out in this episode. Are you saying I've been... I've been stinking it up, what you're saying, with fart jokes. You're like, you said it, Jorge, not me. No comment. All right, well, I guess just to recap, the question we started asking, can neutrinos get redshifted? Right off the gate, the answers no,

because I think most people would agree red shifting only applies to electromagnetic light, as some of our listeners pointed out. Where most people notably doesn't include me, but yes, go ahead. Oh, that's why it's most. But if you ask the question, does the wavelength of the neutrino get stretched out by expanding universe? And the answer is yes. In fact, it happens to all particles with mass, right? And really what that means doesn't mean that it somehow changes the neutrina.

It just means that it slows down. Yeah. So really, the question is, do particles get slowed down by the expansion of the universe? and you're saying the answer is yes because that's what relativity tells us yeah all particles have their wavelength extended when the universe expands for photons that doesn't mean a change in the velocity

but for particles with mass it does all right well it was a circuitous path but we got here now what happens to a fart with the expansion of the universe it also slows down right it slows down but the stink is invariant like mass it's a fundamental quality of the fart

something the fart field can do Each individual particle, its stinkingness does not decrease because its nature doesn't change. I prefer to think about farts with waves as they sort of passed over you rather than think about the individual fart particles than where they came from. Sticking in your nose. Yeah, nobody wants to think about that. Exactly. Yeah. All right.

Well, I think another lesson about how crazy this universe is and how big it is and how the effects of it getting even bigger, what's that going to do to everything in it. That's right. and our intuition for what happens to photons sometimes does apply to other particles, though because they have mass, they follow slightly different rules. All right, we hope you enjoyed that. Thanks for joining us. See you next time. For more science and curiosity, come find us on social media where we answer questions and post videos.

We're on Twitter, Discord, Insta, and now TikTok. Thanks for listening, and remember that Daniel and Jorge explain the universe, is a production of iHeartRadio. For more podcasts from IHeartRadio, visit the IHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows. Every case that is a cold case that has DNA.

Right now in a backlog will be identified in our lifetime. On the new podcast, America's Crime Lab, every case has a story to tell. And the DNA holds the truth. He never thought he was going to get caught. And I just looked at my computer screen. I was just like, ah, gotcha. This technology's already solving so many cases.

Listen to America's Crime Lab on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Hi, it's Honey German, and I'm back with season two of my podcast. Grasias, come again. We got you when it comes to the latest in music and entertainment with interviews with some of your favorite Latin artists and celebrities. You didn't have to audition? No, I didn't audition. I haven't auditioned in like over 25 years. Oh, wow.

That's a real G-talk right there. Oh, yeah. We'll talk about all that's viral and trending with a little bit of cheesement and a whole lot of laughs. And of course, the great Vibras you've come to expect. Listen to the new season of Dresses Come Again on the I-HeartRadio app, Apple Podcast, or wherever you get your podcast. I'm Dr. Scott Barry Kaufman, host of the Psychology Podcast.

Here's a clip from an upcoming conversation about how to be a better you. When you think about emotion regulation, you're not going to choose an adaptive strategy which is more effortful to use unless you think there's a good outcome. Avoidance is easier. Ignoring is easier.

Denials easier. Complex problem solving takes effort. Listen to the psychology podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. This is an IHeart podcast.