The Supermassive Podcast - What the heck are neutrinos?

Episode Date: June 23, 2026

Is this the toughest subject we’ve ever tackled? Izzie certainly thinks so and it’s even making Dr Becky and Dr Robert's brains hurt. Helping them to make sense of these ‘weird and interesting�� particles are Dr Kirsty Duffy at the University of Oxford and Director of the Paris Astrophysics Institute, Professor Kumiko Kotera. For ad-free listening and to view Izzie's trajectory to becoming a better astronomer, join The Supermassive Club. Every member helps keep the show running, so thank you!Send us your astronomy attempts, questions (and nonsense!) to [e-mail], on Instagram at @supermassivepod or post in The Supermassive Club.The Supermassive Podcast is a Boffin Media production. The producers are Izzie Clarke and Richard Hollingham. Hosted on Acast. See acast.com/privacy for more information.

Becky, I thought this was your moment to get a Nobel Prize and be like, yes, actually I've solved it, you know. Maybe neutrinos are the godfacts called us subtly doing their thing. We're building something crazy. Physics is not broken. Hello and welcome to the Supermassive podcast from the Royal Astronomical Society with me, science journalist Izzy Clark and astrophysicist Dr. Becky Smethurst. This month we're exploring the most mysterious podcast. particle in space neutrinos, these tiny subatomic particles are everywhere. Roughly 100 trillion neutrinos pass harmlessly through your body every single second.

So what exactly are they? And what can they tell us about space? Now, this is a safe space, right? Sure. Because I have a confession. I've held off from suggesting this topic for so long because neutrino. because neutrinos confuse me. They blow my mind. I don't really understand what's going on.

We've held off for six years and here we are. You were just like, we're not going to chat about neutrinos because I am an ostrich and Monteverarmerabed at the start about neutrinos. Yes, basically. I'm just like, I'll just wait until someone else suggests that maybe we should cover this. It's fair.

They are weird. They are very weird. Yeah, they're the most, I think they're the... You know, when people think of particles, you picture like these little, you know, just sort of like... spheres of things just making up atoms and being like, you know, actually it is a fuzzy cloud when you get to like A level

and you're like, those electron bottom, you're like, I can just about handle that. Neutrinos, no. It's the numbers. That's like what you just said, roughly 100 trillion neutrinos passing to us every second. No, no. I refuse.

It's one of those things where if you're lying in bed at night and you can't sleep and you start to think about it, you're just like, no, this is not helping. Not helping. So I think I will be learning. along with everyone else. But hopefully Dr. Robert Massey, the deputy director of the Royal Astronomical Society,

can help too. Robert, let's start with the basics. What are neutrinos? Yeah, well, neutrinos are the tiniest in the quantum sense of particles imaginable. Now, I say in the quantum sense, because actually when you get down to these very small scales, concepts like the size of things

don't make quite so much sense. Particles can be thought of a sort of smearing out over a region of space, a very, very tiny one. but they have no electric charge, so they're neutral, and that's why they're called neutrinos. And they're so light, again, in the kind of quantum sense, that we haven't been able to measure their mass, although we know they've got a mass, but it's no more than a millionth of the mass of an electron. Electrons are the regular particles going, you know, that atoms have, essentially, they're negatively charged, that the nucleus of an atom is positively charged, so every atom has electrons.

They're also elementary particles, which means you can't divide them into anything smaller, and they come in three flavors. This is very particle physics speak, electron, muon and torn neutrinos, and that's lining up with the so-called standard model of particles, where there's three families of particles. And they barely react with anything in an amazingly unreactive sense. These things go through you in vast numbers, as you say, and they really don't do anything at all most of the time.

So that makes them ridiculously difficult to detect. And to give you an idea of how weakly interactive they are, if you had a block of lead light year thick now that's quite hard to do to begin with but if you had a block of lead light year thick and you fired a beamer neutrinos through them half of them would make it out the other side so they're going through this vast region of space

through dense metal and even so half of them would make it out that's how weakly interactive they are I wonder if there's even that much lead in the universe I doubt's it yeah exactly probably did not have enough stars to make a block of lead like year thick oh I just had a thought while you were chatting there

Robert as well, like where the name neutrino comes from, because I didn't know the history. And they were theorized by Powley in like 1930. And he was like, oh, we should call them the neutrons if they exist. And then in 1932, James Chadwick was like, no, I have discovered the actual neutron. So that name went. And so then when neutrinos were actually discovered, they took the name that Fermi gave them, who's an Italian physicist. Hence, neutrino, it means like little neutral one, which is so adorable. And now I'm like, yay, neutrinos. I've now like anthropomorphized neutrinos. They are my favorite pod.

I'm more interested in this subject now. Okay, well, thanks for that, Robert. So let's get into this a little bit more. I want to understand where do neutrinos come from? Why are there so many of them? And what can they tell us about space? I spoke with Dr. Kirstie Duffy, a particle physicist working at the University of Oxford

and the Queens College. She does a lot of research based on experiments at Fermilab, a particle accelerator lab, specialising in neutrinos in the US. My first question was about the mass of a neutrino. Turns out that is not the easiest place to start. It's a much more complicated question that I think maybe you meant to ask. According to the standard model, all subatomic particles are point-like,

which means they have no size. But the reason we say neutrinos are small is we have an analogy of size to how likely they are to interact, which is by analogy to like the cross-action area of a ball, if you throw a ball at someone, it's more likely to hit them if it's bigger than if it's smaller. If you take that sort of an analogy, if an electron was the size of like a large beach ball that's sort of a meter across, then a neutrino would be about the size of a grain of sand. Oh, this, see, that is helpful context, yes, thank you. And do we know that? Do we know their mass because I think it's a bit up in the air, right? Yeah, we do not know their mass. We know

they have mass, which is very interesting in itself because that actually is not in the standard model of particle physics. So the fact that they have mass proves that our best model of the universe is not quite right, which for someone like me is very exciting. But the reason we know they have mass is they do this thing called neutrino oscillation, where there are three types of neutrinos, and they've been observed to change from one type to another. And we call it oscillation, actually, because you see them go to a different type and then back again. So if you make a muon neutrino, after some amount of time,

if you measured it again, you'd likely measure an electron or a town neutrino, which are the two other types. But if you waited long enough, you might then measure a muon neutrino again. And the reason that happens is very complicated quantum mechanics, but it relies on them having different masses. And so we know that at least two of them have to have masses that aren't zero.

because otherwise they wouldn't be different. We also have some measurements where people have tried to measure the neutrino mass and basically not manage to measure it. So we have upper limits, but we do not know what the masses are. Other than this upper limit tells us it's much, much smaller than any of the other particles, which is also weird and interesting. This whole episode is just they're weird and interesting. Accept it, move on.

So where do they come from? And why are there so many of them? So they are created in nuclear decays often. So any kind of beta decay will create a neutrino. There are also similar decays of other particles that will produce neutrinos. The reason there are so many of them is because it turns out beta decays are just incredibly common. Almost every element is unstable and a lot of them decay via beta decay. So we get neutrinos produced in bananas because they're full of potassium, which is unstable to beta decay.

But we also get huge amounts. I mean, most of the neutrinos that are passing through us at the moment are coming from the sun because the chains by which the sun fuses hydrogen nuclei into helium and powers itself. There are a couple of different methods that happens, but all of them involve at some point there being some sort of beta decay that produces a neutrino. What exactly can they tell us about space? Because obviously they're around us all the time, right? So why are they so specifically interesting when it comes to talking about space?

Oh, there are lots of reasons. Okay, so first of all, we are being bombarded all the time with neutrinos from the sun. And that is just kind of cool and interesting. The thing that is most interesting about neutrinos from space, I think is neutrinos from supernovae. When a supernova happens, actually 99% of the energy is carried away in neutrinos, not in light or in other matter. So this is when supernova at the end of a star's life, we get the bigger stars, more massive stars even, we get this like massive explosion. Exactly. And we think of that massive explosion being either the sort of light that you see or the fireball in space exploding. But what you don't see is that most of that explosion is just trillions of neutrinos coming out in all directions.

And the neutrinos from a supernova will make it to Earth before the light does. I was hoping you would talk about this because this needs explaining because we say this on the podcast all the time. Nothing travels faster than the speed of light. So then in come these neutrinos before the light of a supernova. So what's going on there? Right. It's okay. Neutrinos still do not travel faster than the speed of light.

Yeah. Okay. Great. Physics is not broken. But it's about how they make their way out of the supernova. So if you imagine a neutrino or a photon, a particle of light, both created sort of right in the middle of this exploding star. In order to make it to Earth, they have to get out of that exploding star first. And the photons actually interact quite strongly electromagnetically.

And there's a lot of particles in there that they can interact with. And so they don't really get to just travel out in a straight line. They'll travel a little bit. They'll interact with something. They'll travel a little bit further. They'll bounce off something else. They'll scatter. And so while the photon, every time it's traveling,

traveling at the speed of light, it's continually being sort of knocked back and scattered and it's not coming out in a straight line. Whereas a neutrino, the only thing we know about neutrinos, that's not true. The main thing we know about neutrinos is that they almost never interact. So a neutrino will just head straight out of the supernova and come straight to Earth. So once the light and the neutrino have left the supernova, the light travels faster, but the neutrino has a head start because it makes it out faster. A good analogy I heard is like if me and Usain Bolt go shopping. I think we can agree that

Usain Bolt is faster than I am, but he's going to get mobbed by people in the shop asking for autographs and wanted to take photos with him. So while I am slower than Usain Bolt, I will pay for my shopping and leave the shop before he does. Okay. And it's very similar with neutrinos and light. That is so helpful.

Thank you. It's not just supernova, right? What about Black Coles? Because obviously that's a, you know, we talk about them being as part of that these really kind of violent events in space. What can they tell us about black holes? So, well, I mean, the first thing actually,

it comes back to the supernova is a lot of black holes are formed at the end of a star's life after a supernova. And so, you know, I think there's a lot we don't know about what exactly causes a star to turn into a black hole and how that process works. If we could see the neutrinos from a supernova, if we watch the neutrino signal come in from a supernova, and it suddenly cut off.

that would be the sign of a black hole forming because nothing can escape the event horizon of a black hole. So all of your neutrinos would be streaming out of your supernova and then suddenly when the black hole forms, they wouldn't be able to leave it anymore. And it would be a sign of the birth of a black hole, which would be incredible to see. Wow, that's amazing.

So if we track that back, does that mean if you got that signal and then it suddenly stopped, then you could technically point. your telescopes to where they need to be. And then you're like, okay, this is that switch point of something going from supernova to a black coal. Yes, exactly.

Oh my gosh. That's amazing. And there is, there's a worldwide network of neutrino detectors called snooze, the supernova early warning system that exists to try and warm astronomers where a supernova is starting to point the telescopes. So we could see the start of the supernova and then also the end and maybe the form of of a black hole. I will say when we're talking about all this, we have measured neutrinos from one supernova ever. It was in 1987 and we measured about 12 of them. So we're really excited about

all the stuff we could do. We've never actually really done it. We're planning a new generation of neutrino detectors that should be turning on around the end of the decade and both of them has supernovae as one of their main focuses. So at the moment, the neutrino community is just really hoping that a supernova doesn't happen in the next four years. Okay, Becky, so a lot of the time I've seen scientists say that we've discovered three types of neutrinos so far. So are neutrinos potentially the answer to this missing mass of the universe? And as a little recap slash scare moment for listeners,

95% of the universe's mass is missing. We don't have time to go down that rabbit. bit whole. We have made a full episode about that. We have. Yeah, go check that one out. So could neutrinos help to unravel that mystery? Oh, sadly not. No. So, yeah, I know. Sadly, this was, um, it was like the hot topic of research at the end of like the 70s and early 80s because it was, it was the leading candidate for dark matter for a long time, neutrinos. So dark matter being this matter that we, we know is there from our observations of the universe, but it doesn't interact with light in any way. So the

electromagnetic force. So we as an emit, reflect, absorb any form of light. So, you know, we just have no way of observing it unless through gravitational waves. Maybe people are hoping in the future. But again, that's another episode as well. But neutrinos, as we've famously heard many times throughout this episode now, they barely interact with anything. So this is why they were thought to be a leading candidate for Darmata for a long time. The problem is because they're so light, they travel at close to the speed of light, which means they have a lot of energy. Yeah.

And so they really resist getting like bound together by gravity, right? There's always enough energy for them to escape them being like clumped together. So they don't they don't help to make structure in the universe, right? So they don't clump things together. Instead it smooths things out, right? It gives particles energy to escape. gravitational wells and things like this. And that's not what we see in the observable universe, right?

The observable universe is very clumpy. When we look out, we see, you know, lots of galaxies, lots of islands of universe. And when we plot their positions and we sort of keep zooming out and zooming out to look at that map of the positions of galaxies, we see that they make this sort of web-like structure, right? That's sort of like filaments and voids and all the matter is clumps together in galaxies and along these.

these filaments. And so in simulations that managed to recreate that structure that we've observed, they're the ones that have cold dark matter. So matter with not as much energy that can clump together. Unlike neutrinos, which have been dubbed hot dark matter. Okay. Which is why for anybody in the know at the beginning of that question, they would have liked the pun that I put in there that was like,

it was the hot topic of research at the end of the 17th and start of the start of the 80s because it was hot dark matter. So people have considered this and basically the answer is no, probably not. Even if we do find different flavors of neutrinos in the future, they're going to be very weakly interacting. They're going to be probably very light and therefore like to be class as a neutrino in the first place. So they're probably not going to be dark matter candidates.

Becky, I thought this was your moment to get a Nobel Prize and be like, yes, actually I've solved it, you know, this is it. I'm sure people in the 70s and 80s went. through that exact same roller coaster emotions. And there was something that you mentioned at the end of last episode that scientists have used Nucinos to create an image of the sun. So can you talk us through what that is and how did they do that? Yeah, this is one of my favourite stories.

So it's a picture of the sun taken at nighttime. Okay. Which like that thing came for a second. So it's taken looking down through the earth. So like you've got to turn around and look through the earth back at the sun. night time, right? And it's done using neutrinos. So it was done back in the 90s using the neutrino detector super cameo kande in Japan. It's a thousand meters underground, buried like under a mountain. And it has this like cylindrical tank that's about 40 meters wide and about 40 meters high.

And it's filled with 50,000 tons of water. Like it's an insane thing when you think about it, right? And it has to be that big because the majority of neutrinos are, are just going to pass through this detector, completely unimpeded, right? But in the very rare case that the neutrinos do like collide with an atom in the water, they generate these very brief, like tiny flashes of light, which you can then detect with one of the 13,000 light sensitive detectors that like are, you know, around the outside of this tank. If you've ever seen a picture of it, they're absolutely crazy.

They're like these big, almost like they look a bit kind of, of like lenses, like these big golden yellow like ball lens things on the side of the tank. I was just going to say, I would recommend people go and find a image of this because it looks beautiful and slightly nuts and kind of very futuristic. Exactly. Yeah, which is why filmmakers like absolutely love it, right? Because there's nothing else like it on earth, right? You'll see it in everything now that I've pointed it out.

You're like, oh, it's super gay. But what happens in Super Gay, right, is that they, for this, to get this picture of the sun that we were talking about, they detect around about 30 neutrinos a day that pass through the detector of the trillions and trillions and trillions that pass through, right? It's a tiny, tiny fraction. I was going to say it's really not that much in the grand scheme of how many neutrinos are like bombarding us. It's vanishingly small, yeah. And about 10 of those 30 that they detect are made in the sun. deep inside the sun from nuclear fusion. And they escaped the surface far quicker

than the light does that's produced, the energy that's produced in nuclear fusion. So if you spend a really long time collecting enough neutrinos from the sun over many, many nights, eventually you can build up a picture of, where is the sun, right? Because you can strangulate from where the light was detected,

which direction the neutrino came from. And so you literally collect enough neutrinos from the same direction. to be like, oh, there is the sun. And you can get a picture of what the sun looks like taken at nighttime in neutrinos and what's going on deep inside the sun, which is really cool,

but also probably one of those like things where there'll be particle physicists that care about what's going on in the sun who really care about those neutrinos. And then a lot of particle physicists who are like, can we please remove the noise of the sun from our detector?

And it is that thing to, if you look at this image, it's not how you think, think of an image of the sun, right? It is kind of square by square. It's a big blob. It's a blob. It's a blob.

But it's when you get into the process of it, it's very cool. So that's just something I bear in mind when people go and look for that image. Yeah, yeah. And there's one more thing as well, because in my research for this episode, there's many things that made my brain hurt. And I saw this sentence that said, some scientists think neutrinos might be why all anti-matter, the antiparticles of all matter, disappeared after the big bang,

leaving us with a universe made of matter. Please explain. This is a big one. I'm out. Yeah, this is the stuff that keeps you wing. This is a really big one, right? This is current, like, cutting edge research now that you're getting into. So pivoting from, we just talked about dark matter.

Very, very different thing now is antimatter. So we've observed antimatter before. we know that like it definitely exists because we can point to something that like this, this is antimatter, you know, unlike dark matter where we have observations if we think it exists, but we can't point to anything that is definitely it yet. So every normal matter particle has an identical particle with the same mass, the same spin, but it has a different charge. So for example, like an electron, right, that we find in atoms, they're negatively charged. But they do have their antimatter particle called the positron, which is the same.

same except for the fact that it is positively charged. And, you know, these are made during, like, you know, natural, like, radioactive decay processes. So we see it happening all the time. You know, there's positrons in bananas, for example, because of how much potassium they have in them. So if you want to be like, where is the antimatter point at a banana in your fruit bowl? So it is like, you know, this is something that we can definitely say this definitely exists. And when antimatter meets normal matter, it turns to pure energy. So you remember E equals MC squared from Einstein?

Like, you know, this is what unlocks the energy from fusion. Matter is just stored energy. Basically releases everything that is stored. Yeah. If everybody remembers Angels and Demons, the Dan Brown book, right? This was like the main plot point if that whole thing was like an antimatter bomb, right? Oh, I think Pip's outside of my door crying. She showed me out.

Anyway. She loved Angels and Demons. She just loved Angels and demons, exactly. And so there's nothing special about normal matter or, antimatter. They're equal in every single way, right? And our particle physics models that we have predicts they should be made in equal quantities when you think about like, you know, big bang nucleosynthesis of like what gets spit out, you know, as things are created. And yet, somehow we ended up in a universe dominated by normal matter. Otherwise, we would not be here. We would just

be pure energy because of annihilation. Like the percentage of antimatter in the universe is effectively zero. Like it's not any sort of like reasonable percentage that you could put into a number, right? So what we think happened to explain this is that if in the early universe there was an ever slight imbalance. So for example, for every billion anti-matter particles there are, there are a billion and one normal matter particles, like one more, right? Yeah. In that kind of ratio. Then the billion would annihilate each other and you'd just be left with one normal matter particle. And then that's enough to like create everything. It's not just one, but like that happened multiple times, right?

Why this happened, though, we're still not sure. And there's lots of ideas to explain it, and a lot of them have neutrinos as the culprit, right? And the reason why is because we know that they can switch between what kind of neutrino they are. So what we call it like a flavor of neutrino. So there's electron neutrinos. There's muon neutrinos.

There's tau neutrinos. And they get slightly heavier as you get out towards tau neutrinos. we think. And if in this switching, this oscillation, as we call it, there is perhaps a tiny chance that maybe something goes like, I want to say wrong with the switch, but something doesn't happen as we'd expect it to do and that you maybe get maybe an anti-neutrino forming instead so that you get this imbalance, even if it's a vanishingly small chance, there's trillions and trillions and trillions and trillions and trillions of neutrinos out there, it could still give you the asymmetry that you need to have a universe dominated by normal matter.

So this is why I was saying this is the cutting edge of research. People are still like actively working on these hypotheses to explain this imbalance. People are looking at what's called charge parity violations and there was some interesting results from CERN recently as well that they might have found something like this

but like it's still so fresh this kind of area of research. It's not something that's really been figured out yet. Okay. And now that means just we're just going to have to keep coming back to this isn't it? Yeah, not only a neutrino is keeping you up at night, now you realize that the reason we might all be here in the first place.

With me for life. Yeah, I mean, I love the idea that these particles that dominate the universe in a sense, but also are impossible or near impossible to detect, might actually be the reason for our existence. You know, we talk about the Higgs boson being the god particle. Maybe neutrinos are the god particle, just subtly doing their thing.

Just, you know, in the early universe, making sure that we existed. I mean, that's just, that's mind-boggling. And I think, Izzy, I'm with you on this one. It's, yeah, there's a lot about neutrinos that when you think about them, I just, yeah, really so conceptually different from the world we think we live in. And yet, there they are. Yeah, this abatomic can of worms.

Love it. I mean, it's mad, isn't it? Trillions of them going through our bodies every second. Yeah, absolutely bonkers. What is it? 99%. center of the energy of a supernova is neutrinos in the explosion, and yet there they are. We barely detect them. It's just utterly crazy.

And on that, we now need to go to a break because I need time to compute. Thank you. There are a few ways that we can detect neutrinos. I mentioned earlier about the detectors underground at the Super K Observatory, but to capture like the rarest high-energy neutrinos, scientists are turning to radio astronomy, another. Enigma. Is he your thing is neutrinos? My thing is radio astronomy. Okay. We're doing well. They make it work and I don't question them. So when an ultra-high energy neutrino interacts with the Earth's crust or atmosphere,

it generates a cascade of secondary particles. So other things that the interaction makes. And the shower emits a detectable radio pulse. Dr. Camico Cotera is the director of the Institute of Astroenus. Physique de Paris. Are we doing that in French? Yes. Okay. And also is the first woman in that role, actually. And she coordinates Grand, the giant radio array for neutrino detection. It's set in the Gobi Desert and this array captures these radio pulses, which researchers can trace back to explosive events in space. Camico Guterra calls herself a neutrino hunter. I love that and explains to producer Richard Hollingham why she's interested in these messengers from the violent universe.

I believe that space is a very poetic place. It's just full of sparkling objects that emit light that burst. It's not something that is supposed to threaten us and not empty, dark and anxiety-inducing. But you call it the violent universe, and why is that? So indeed, when we look at the night sky, We believe the universe to be a very serene and peaceful place with all these stars shining peacefully.

But it is populated by massive stars ending their lives bursting in supernovae. You can have even more massive stars collapsing and producing jets that are visible from the outskirts of the universe. You have these extremely violent events happening. that emit outbursts of energy, and in this sense it is violent. But it is so far away, and it's a bit like a firework, really.

And we want to understand how these events happen physically. So if we observe a neutrino on Earth, if we just track them back, we're going to see immediately their sources. And this is a great way of doing astronomy, because whenever you have a burst inside violent objects, you're going to accelerate particles. These neutrinos will get a large fraction of the energy of these accelerated particles,

and they're going to fly to us directly without being bent or anything. If we detect these very high-energy neutrinos, we can get an understanding on what's going on in these objects, what happened to accelerated particles inside these events. So it's a bit like you're a problem, being the inside of the sources, which you can't do with light necessarily, because light before it escapes, is transformed and neutrinos just go straight and traverse everything, right? So they're almost a record of what's going on at these violent events?

Yes, definitely. It's really a record of the motion of the matter and how energy was transformed. So if they're so promising in terms of a way of seeing, what's going on. I shouldn't really use the word seeing because it's not light. How difficult is it to detect them? It is very difficult because neutrinos just go through everything, so it's difficult to catch them. And at very high energies, the energies that we're hunting, they're so rare that you need to build a detector with a huge surface of collection to have a chance of getting something. So today, we are. are trying to build a detector that is going to detect neutrinos at a billion times the energy

of neutrinos produced by the sun. And to do this, we're building something crazy. So we're building a detector made of radio antennas that are already installed in the Gopi Desert in China. Very simple radio antennas. Very similar to what you have on the top of your cars and that are going to detect signals in the FM band. So literally like an old car from the 1990s or something when FM radio was a big thing? Yeah, just like the radio you're listening to, yes. So in this frequency band, definitely. So our plan is to build tens of thousands of radio antennas in desertic areas.

So we've started already in the Gopi Desert. We have 65 of them operating and that I've already detected not neutrinos, but atomic nuclei producing radio emission so that we've shown already that this method of detection using radio antennas what's going to be efficient and good enough to do neutrino hunting. And I guess you're doing it in a desert because you literally don't want any people in cars with FM radios anywhere near? Absolutely. wherever you go in principle, even the most remote desert in Kobe or in the Pampa in Argentina, you always have lots of radio noise made by cars passing by electric lines or things like this.

And if you're in a city, it's just impossible to detect these little signals made by neutrinos. So you do need to be in the most remote places ever. I mean, and so, yeah, one good way of checking whether it's a good place that you're installing your antennas in, is that you go by, so usually you drive in desertic regions in unpaved roads and for hours. And you have an antenna in the back of your car, you just, and before even taking the antenna out and taking some measurements, you can just switch on the radio of your car. And if you hear some broadcasting, it's just not a good place. And if you don't hear anything, you're like, okay, let's, let's try it. And so the new project is in Argentina. And how ambitious is that?

That you're going for neutrinos this time, are you, with this? Yes, we are. So this year was just amazing because we did detect for the first time particles from space with radio antennas alone. It was just amazing to do it and to show that it was functional. because this was successful, we are going to the next scale to detect not just atomic nuclei, but neutrinos that we're after. And this is going to be in Argentina so that we can also cover both hemispheres,

so one in the northern hemisphere and one in the southern hemisphere. And we have a great supportive community also in Argentina. We're going to the Anders and the Pampa in Argentina. and we're going to install over 70 kilometres of mountain a thousand radio antennas in order to hunt these ultra-high energy neutrinos. Are they going to be in a mass or a line of them? What's it going to look like? So it's going to be 24 stations with 24 antennas in each station.

So these are spots on the side of the mountain at a kilometer elevation, so 1,000 meter high, and surrounded by sparse antennas, 15 of them located farther out. So you have a little cluster of 24 antennas and 15 antennas farther out, and 24 of them over 70 kilometers. Wow. So what's the potential of this then? I mean, we've heard a lot about gravitational waves, for example, as opening up at this sort of new view of the universe. What's the potential of this sort of detection and being able to spot neutrinos? I think it's the same kind of potential as gravitational waves. We're going to open a new window on what's going on in the universe. Just like we started understanding what masses were at play with gravitational waves,

we're going to understand what energy is at play with neutrinos inside these violent objects. So it's going to be a sheer revolution. And this is where I think astronomy is heading. So not just astronomy through light, but astronomy with neutrinos, with gravitational waves, with light, with cosmic particles. And we need to put everything together. It's not going to be just one messenger alone. This is a new big thing happening today in astronomy

that whenever something is detected, everybody gets the information. And we're all pointing into that direction and trying to combine all these messengers together. And that's also in terms of collective human effort, especially today, it's very promising and enjoyable to see everybody getting together for a common goal, which is to understand the sky. Thank you to Kamika Katera, and her book, The Violent Universe, is out now. I was just going to say that everything about that job right,

Neutrino Hunter, based at a large facility in the... Gobi Desert. I mean, this is like a, this is a Bond movie, isn't it? Yeah, or like at the next contact or something. Exactly. She's like Joan Foster, but instead of aliens, it's new trinos. Yeah, it's like, goby desert. Then Argentina, you're like, okay, fine.

Cool. I mean, that's so badass. Yeah, very badass, very badass. I've also seen Katera's book. I'm not read it yet, but it looks very cool. That could be one for Space Book Club is if we do it next month. Yeah, that's true. Let's add it to the list.

And it's the list. This is the supermassive podcast from the Royal Astronomical Society with me, astrophysist, Dr. Becky Smiththurst, and science journalist Izzy Clark. Okay, so it's safe to say that everyone went to town on the questions that were sent in for this episode. So thank you for that. Let's ease in, Robert, with this one from listening to Ginger Hulk, who asks, how many neutrinos have passed through my body while I've been listening to this episode. Let's go for a full episode. But on average, our episodes are about 50 minutes.

That long. Yeah, it depends on the idiot. We have a lot to say, Becky. Ginger Hulk, it's a crazy large number. You know, as Becky said at the start, 100 trillion or 100 million million neutrinos passed through an average-sized person every second. So the typical episode is supermassive.

If we go with 50 minutes, number 3,000 seconds, that means 300 quadrillion or 300,000 million million neutrinos coming through you in that time. And the other thing, to remember about that is that virtually none of those will interact with you in any sense. I was doing some reading around this and you get the occasional reaction where, say, a chlorine atom, one of the things we have in small amounts in our body would be turned into radioactive argon. But chances are, over your whole lifetime, it wouldn't happen.

So you have these enormous numbers of things going through you and over your entire lifetime, they do nothing to you. I mean, this is why neutrinos are nuts, right? You know, this flux of stuff. don't do anything at all. Fast numbers, nothing ams. It must frustrate neutrino hunters so much. Like, I'm frustrated as a black hole physicist and it's like, oh, we'll never know what's beyond the event horizon. They must be like, I'm hunting them, that there's literally hundreds of trillion spassing through me all the time.

I know where they are. I just can't get at them. And I'm going to detect two. Let me go to the most remote parts of the world to literally try and find it. And then look through the earth. You're waiting for you know, look at what's coming up through the earth. I mean, they're dedicated if nothing else. Yeah. And Becky, listener Jason Jansari, has asked if you can explain superposition to a non-physicist.

I will try, Jason. I like to think of it as two things being true at the same time, which I feel like is something that as humans, we do experience a lot. Like, you can be happy and sad at the same time. Like both things can be true, right? you can be both excited and scared, or I always think about it when I'm like, oh, if I'm waiting for like big news, like that I'm not in control of, like, for example, like if I'm waiting for the results of an exam, for example, like, you know, you're waiting to get in to find out if you got into university or something, right? You're existing in a state where two futures are possible at once before you get the results, right? There's like the pass or the fail you get in or you don't get in. and it's only when you know you get the results that you you know you find out which future

becomes certain right and so i mean the one that's used a lot is flipping a coin just because we're so we're so familiar with flipping coins it's the one example i can give you while if you flip a coin while the flip is going on if i then asked you is the coin heads or tails like it would you'd be like well both yeah but also neither right it's always always almost like a question that you can't, like it doesn't make sense to ask the question right. So both are true at once. The coin is both heads and tails while it is being flipped until it lands, right? So that's what superposition is. Superposition is that state where both and yet neither are true at the same time. So it's the same as true for a particle. A particle can be in two states

or even two places at once if you really want to get the quantum mechanics of it all. You know, a particle can be both heads or tails, using our coin example. But it's only when you observe that particle that you force an answer, that you force the coin to land, you force a reality, really, is that you collapse the superposition and then it becomes like a specific, you know, sort of position or charge or spin or whatever it is. And this is actually what's responsible for the neutrino oscillation that I was talking about before. So this idea that it can flip between, is it an electron neutrino?

is it a Muon neutrino or is it a tau neutrino, right? People like to explain that it's kind of like it's kind of like playing a chord on a piano, like you're playing like three notes at once, and it's only when you detect a neutrino that you hear only one note. Yeah. And so the superposition is the fact that it is sort of a superposition of all three of those different types of neutrinos, and then you force it to take one flavour by observing it.

So it is a very strange concept, and I hope to a non-physicist. I've managed it. Maybe not by the end. We got into a little bit more physics, but hopefully Jason that answered your question. And Robert, Adam Reeves wants to know how are we able to take images with neutrinos

and what is the future of this? So we've already covered this a little bit, but yeah, tell us more. This is a great question, Adam. And the answer is that you need a lot of neutrinos to build up a picture of anything. Just as you need a lot of photons of life, you think about the image you make with the detector,

you know, your mobile phone image has vast numbers of photons coming in conveniently that actually react with the sensor and they get turned into electrical charge and your phone assembles an image from that. The problem with neutrinos is that it's really hard to do it because they don't interact. So it takes an incredibly long time. And that standout astronomy example is the one Becky mentioned earlier, an image of the sun released in 1998.

You can Google the astronomy picture of the day for that, just three years after that going in the early days of the web. And that was made from 500 days of neutrino detections with the, you know, with Super Cameo Kandi. So anything else is going to be incredibly hard because those sources are weaker, they're further, well, they're not necessarily weaker, but they're much further away from us.

And even the supernova that went off in the Large Magillian Cloud in 1987, that was the nearest supernova for hundreds of years, that only led to 25 neutrinos being detected at the time. 25. I thought it would be so much more. Yeah, it was mad. Well, I mean, there were vast numbers that came through it. But those 25 were detected.

So because of the timing, The interesting thing about that is they actually reached us before the light did because the explosion only reached the kind of surface of the star of the eruption three hours after that. So, or three hours after the neutrinos left. So we saw the neutrinas were an advance warning in a sense. I'm not sure that it enabled people to see the supernova at that point because there were a lot of coincidences and the images appeared more at the same time. But that was the kind of timing when it was worked back. I don't doubt that today we'd find many, many more. neutrinos, but it might be 250, right? So you think about assembling an image with 250 dots.

It's not going to be brilliant and it's going to be pretty low resolution. You know, you're going to be looking at some little dot in the sky. The best you can get probably, I suppose, in the future is you can think about making maps of the sky if you look at sources and that kind of thing. So, and we have found them from other galaxies and that kind of thing. But again, it's just a spot in the sky. You know, we detect five neutrinos, say, from this particular external galaxy and think that's the source. So for the future, it's going to be about finding those from supernova centers of other galaxies. And some of those are high energy, as Becky mentioned earlier on.

And therefore, you get a different effect. And you can trace the way their track goes through the detector, if there are any more interactions. It gives you some idea of where they came from. But it's quite a long way from being a really good image. And, you know, as I said, you're quite often talking about a single neutrino being detected. And then everybody goes crazy. Great. You know, a single neutrino detected from another galaxy.

And that's a standout observation that allows people to write lots of papers. So it's quite unlike the rest of astronomy in that sense. Well, I think you're making the high redshift people feel better. The people who study like the most distant galaxies in the universe with JWST, where they're like, we have a tiny little red dot. I mean, they get millions of photons, don't they at least? Well, yeah, but that's the thing. It's like it might look like a tiny red dot in the image,

but at least they have an image from all those photons, right? At least it's not just one neutrino. Those poor neutrino hunters. But can someone needs to check in on them? Are they okay? But can I ask? So because take that event from 1987, you've got that influx of, okay, 25 new tuners being detected. But I suppose is that a surge compared to what the baseline level is?

So even though, okay, it's not loads, but it's more than it would be if there wasn't an event, right? So that's kind of what they can, they're offsetting it against, I suppose. It's like an early warning system. So those 25 neutrinos had it. I don't think it quite worked like that at that time. But there is the idea now that if you see that sort of surge, you would then get and you had an idea where it was coming from in the sky. Because you know that there might be a matter of hours between the two detections,

you could swing your telescope in the direction of where the surge came from and hope to catch the very early stages of the supernova. So that would be great because usually with supernovae, what happens is we see them after the event. We think, oh, people are, studying in galaxy. They take an image of the galaxy and say it all there as a supernova and it's not probably not going to be when it just goes off. So this is another way of trying to get an early warning of that and trying to see these events very, very early on.

I mean, by early warning, by the way, I don't mean early warning of something that would be bad for us because these are all very, very far away. But it's just getting a bit of a hint that something big is about to happen and being able to see it happening. It's a fun early warning for astronomers, right? There's a lot of people that are on sort of almost on call for supernova. going off. But like, I mean, the timeline usually is like if you can get it a few hours after the supernova went, you know, that's, that's course for celebration. There's a lot of things about supernova models that are really uncertain because we don't have that, like we were

watching it the exact moment. And this all leads into things like getting the cosmic distance ladder and the crisis and cosmology, the Hubble Tension, all this stuff we've talked about on the podcast before as well. But in terms of like numbers, like, you know what I said before, like superk detects like 30 neutrinos a day. And so if you, if you, get 25 within a little, you know, flash of a moment, you know, you're going to notice that over the background. And like Robert said, if it ends up being 250 rather than 25 next time one of these things goes off close to us, that you could have noticed that, you know, especially if neutrino detectors all around the world spot it as well, that would be really helpful

because it would be slight time delays. The triangulation would be even stronger and we'd have a really good idea, like, where the supernova was going off in the next couple of hours. And especially with the Rubin telescope coming online very soon as well, you know, we would hopefully have, like, some telescope in the right place in the world at night time. So hopefully point in this thing, as long as it's like not, like, you know, looking up to the North Pole, the summer solstice or something, you know, but at the same time, like, I think it's one of those things that we should have the kit to be able to actually probably follow up on. If it happens.

If it happens. things are so rare, you know, so yeah, that's the problem. But equally, I'm just thinking of, like, someone who's probably got telescope time and like, yes, finally, my little thing will get some sort of data. Then it's like, bam, supernova, like, nope, sorry, got to go. I don't think you'd be mad. I think you'd be on every single paper that they got published. Your 8 index would go through the roof.

And also, we're in an era now with, you know, not just Vera Rubin, but also robotic telescopes that weren't around in the same way 40 years ago. So that's a difference, right? So very quickly these things can be pointed into position. It's not about having a telescope operator and argue the people who've got time on the telescope to say, we want some of your time that you've spent months and applying for. You can just say, point this thing, grab the data. And that's what's really nice about it, I think.

Yeah, and like things in space even have that too. Like, you know, like JDBST Hubble, they all have like directors discretionary time and things like this, where if something like this goes, they drop what they're doing and it's all hands on. I'd like to be in the room when that happens, please. Right, well, thank you to everyone who sent in questions. And if you've got a question for us, please send them in. We love reading them. You can email podcast at rias.ac.ac.uk.

Drop us a message on Instagram at supermassive pod. I'll often put on a story and you can just put it in the comments there. Or join the Supermassive Club and post on the forum and join the book club. There's a little link for membership down there and you get no ads, is lovely. So shall we finish with some stargazing? Robert, what can we see in the July night skies? Yeah, so July is obviously holiday time for many of us and it's very much time for the summer constellations, but it does still mean being up fairly late until the end of the month. You know, you're looking at sort of 11 o'clock in the evening in the UK. It's better if you're

further south because they don't have the same swings in the length of night and day that we do if you're further from the equator. But if you make the effort, you start to get, this is the time when you start to get to see the summer triangle, the brilliant dominant, I say, asterism, big pattern in the sky, the three bright stars of Vega, Deneb and Outer. And if there's no moon in the sky, then you've got the wonderful, the glorious Milky Way stretching across the inside view of our galaxy. And, you know, always a really nice thing to see in late summer and early autumn as it stretches up from the southern horizon right across the sky.

And if you look down to that southern bit, you'll see Scorpius and Sagittarius. And they are zodiacal constellations. So there are bits of the planet and the sun and the moon move. through, but also they mark the direction of the centre of our galaxy, and that means that they're really packed with stars. So it's really impossible to list all the objects that you can see in that direction. But I would say, pick up a pair of binoculars and have a look. I mean, there are things like Messia 24, which is the Sagittarius Star Cloud, so a huge concentration of stars, the small Sagittarius Star Cloud, I should say, and Messier 11, the Wild Duck cluster in Aquila

a bit higher up. And you could do things like you could experiment with smart telescopes to image those kind of things, which some of them even do automated wide views now to capture the whole sky. And we've seen, with that, I've seen some brilliant time lapses. So a guy, I know filmmaker Daniel Taylor took a time lapse of the Milky Way rising over the sea at Kukmehaven in Sussex. Now, you need a certain amount of stamina because it took him six hours to do it. So I don't think he was sleeping that night. He was doing it from, I think, about 11 o'clock at night through till 5 in the morning.

But we do see a lot of those beautiful images this time of year. And if you've got a telescope, then you can see things like the ring nebulae. Lyra, which is a planetary nebula, so the remnant of a dying star, and the big globular cluster Messier 13, which is a bit nearby in Hercules. And another good target is Albireo, which is a blue, yellow double star, that even binoculars show well. And it's known because it's very wide. They're not, I don't think the two stars are physically associated.

It's just that coincidentally in that direction, the same direction as each other, but one might be further away. But they are, they do have this lovely color contrast. And that in astronomy is always a nice thing to see when you look at stars and you think, that's obviously blue and that's obviously golden. So I very much recommend that. And solar system-wise, we're not blessed with planets right now. They're not, they're either out of view or they're just an inconvenient time of night.

So we have got Venus in the evening sky, really, really dominant, very, very bright object after sunset, getting closer to the Earth. And Saturn is visible after midnight, but again, you have to stay up quite late for that. And I'd also say it's still worth looking out for sunspots. Again, all the caveats about doing that with safety, making sure you've got a telescope with a safe filter, etc, etc. But they're there. And finally, look out for those noctilucent clouds. The weird weather phenomenon that somehow is the transition between astronomy and meteorology because they're so high up in the atmosphere. They're almost as high as meteors and they're made of ice crystals really high up.

And they light up the northern sky in the middle of the night. It's completely ethereal. You look north and you think, what are these glowing clouds doing in the middle of the night? So do look for those. Do take some pictures and let's see how people enjoy it. I also have to thank you for your recommendation last month of seeing the conjunction of Venus and Jupiter. It was so clear here, wasn't it for it? It was so good. So I was in Devon with mates and I was like,

oh, it's the eighth. Hang on, let me go out. And like everyone, all of my mates had gone to bed. And I was like, read just about to change into PJ. So I was like, no, it's today. So I walked out. And it was just after sunset. And it was literally just,

over the house's opposite house. Really clear sky, so bright. It was gorgeous. But then I tried to get a little bit into a darker area, but it was near someone's house. And they just had these two really loud Alsatians. And I set them up and I was like, hang on, I can't stand by this field and set up someone's dogs.

So it was peaceful until the Alsatians. And I feared for my life. Did you get any pictures, is it? Yeah, yeah, yeah, only on my phone. but actually it was good enough and then you could see. I see say it's so bright. Venus and Jupiter are the brightest things in the night sky after the moon, right? So it is fine. And it was so dark as well.

So then I could see Castor and Pollux as well. Just like, and they were almost in a line. It was just like just one of those moments. You're like, oh God, I need to leave London, don't I? I need to see the night sky far more than I do. You sounded so much like you were from London. I need to leave London, doesn't I? God,

I love that. Well, I think that is it for today. We'll have our usual Q&A in a few weeks' time and then we'll have another main episode on its way. Hello, but we're like, on its way because we haven't decided what it is yet. Contact us. If you try some astronomy at home,

it's at Supermassivepod on Instagram or email your questions to podcast at r.org. And me and Robert will try and cover them in a future episode. Until next time though everybody, happy stargazing.