There's this image of the sun going around on the internet like But there's a catch. The image was taken at night. How do you think that's possible? Oh, wait. Taken at night? Yes. On the surface of the Earth. And you can't pick it up with visible light. Is it like infrared or something else? Like No, we are not picking it up Oh, via light in any form. Not light. No, I don't know what else comes off the sun that we can detect for. You're on the right track. Okay. something from the sun that goes through the earth.

I don't know. I just Have you ever heard of nutrinos? I've heard of them. Yeah. Okay. This is made with a giant detector in Japan called Supercomio. Oh, cool. That detects these particles called nutrinos. This is an image made by detecting a bunch of neutrinos from the sun. People have often never even heard of nutrinos, but yeah, about 100 billion solar nutrinos are passing through your thumbnail every second. Crazy, which is wild. Okay, but pause. I want to tell you something crazy about how elusive nutrinos are. Like maybe the most elusive particles in physics. Guess how long it takes for light to get from

the center of the sun to the outside of the sun. Oh my god, can I guess? Yeah. Yeah, of course. I always want you to guess less than 30 seconds. That's a great guess. Yeah. Okay. So, if it were traveling straight, not interacting with anything, it would take about 2 seconds for light to get from the center of the sun. Order of magnitude, you're on. Nice. If it weren't interacting with anything, but the sun is extremely hot and dense, which means that there's a lot of matter for the light to interact with. So therefore, when light's produced in the core of the sun, to get to the outside

of the sun, it actually takes, you ready for this number? What? Hundreds of thousands of years. What? Yes. Seriously, hundreds of thousands of years. Because light is actually it's not going straight. It's like bumping into this hydrogen molecule, this helium molecule. Because in between all those interactions, it actually is going the speed of light. So like this, for example, the speed of light in water is not the speed of light. It's the speed of light in water. It's actually a little bit less because it interacts with water molecules along the way. Guess how long it takes nutrinos. How long? It's 2.3 seconds.

Oh my god. Because they interact with matter so little. So light interacts with matter quite a bit. So light takes hundreds of thousands of years to get to the surface and then it takes 8 minutes to get to us. 8 minutes to get us. The nutrinos we can see right now happen so much sooner than the light we're seeing like when it was created. Exactly. Yeah. So, if there was like a solar apocalypse or something crazy going on in the core of the sun, we would find out from nutrinos. So, they would be like our blinking solar apocalypse signal.

Nutrinos are known as the ghost particle because they'll just pass through a wall like a ghost. They'll pass through the entire Earth like it's nothing. So, you'd think this image of the sun maybe shouldn't be possible. So then, how is it possible for us to detect these particles, these ghost particles, if they're going straight through the sun essentially, and then they're going straight through the Earth? Like, why would you detect them in your particle detector? Well, you just need lots of them, like lots and lots of them, because they do interact. They just interact really infrequently. Guess how many nutrinos get detected in the supercomio detector every day?

Every day. 500,000. Good guess. It's 30. 30,000. 30. That's it. Whoa. Which is why the image is so blurry even though they spent 500 days detecting because you barely get any nutrinos. Do they have a effect reaction on us? In fact, every once in a while, just like in the detector, they'll like knock an electron. And really, yeah, they have very little mass. So, they're going to just kind of like boink the electron. They are going very fast. So they actually do have quite a bit of energy and it's happening right now. Like yeah, the picture that I showed you, this picture wasn't actually taken fully at night. It was actually taken over the course of about 500 days.

So it was night and day. It was actually taken deep underground. So it's about a kilometer underground. That's where the super commio detector is located. That's one of the other ways that you get enough detections in order to make an image. And it's still a pretty blurry image, but yeah. So there's trillions coming through every second, but they spend 500 days like absorbing nutrinos or whatever the term is for what they're doing. But this detector is really big. It's this giant cylindrical tank that's about 40 m by 40 m. All the pictures of it are when it's empty, but it gets filled with water. It's 50,000 tons of water. And then these light detectors all around in the water. So what happens is

the nutrino comes in, it kicks an electron that produces a flash of light in the water and then these light absorbing detectors will detect that very tiny flash of light and that's how you see a nutrino even though nutrinos are one of the most mysterious objects in the universe. So then what is a nutrino? Yeah, it's a like I said it's a subatomic particle. One thing that I didn't know is that not every particle interacts with all of the forces. So there are four fundamental forces. The electromagnetic force, gravity, electroeak force, and strong nuclear force. And nutrinos only interact with two. Gravity, and the electroeak. You don't really need to know that, but you have to know that.

I like knowing. Yeah. You like knowing it. Yeah. I like hearing about it in this context. So, nutrinos are basically the perfect particle for this because they're subatomic particles that barely interact with other mass because one, they themselves have very little mass. We actually don't even know their exact mass, but we do know it's at least 1 million times less than the mass of an electron. In fact, we thought that they were massless until 1998 when there was a discovery that nutrinos have a tiny amount of mass which won the Nobel Prize in 2015. Really? So these are like recent physics, super recent.

Some of the big unanswered questions about nutrinos is how massive are they really? Another is are nutrinos their own antiparticle? Oh, like for example, the antiparticle of the electron is the posetron. What is the antiparticle of a nutrino? We still don't know. Sounds exciting. Ah, are there new dimensions or forces that we can find using nutrinos? Maybe they're a ghost particle, but they're also they're kind of like your uncle as a ghost. Like kind of tapping your shoulder and being like there's still more to learn about the universe, but we're [clears throat] it's just lightly

tapping your shoulder for decades and maybe someday we're going to get to a place where we learn those answers. How is the scientific community reacting to that photo? And this photo is from the 1990s. Wow. Yeah, it's old. Levi, first physics video in 3 years. This is so exciting. Back physics girl. We're starting strong and doing nutrinos. This is a cool topic. Stopping for myself. But working from the bed as you have to with long co. Yeah. We're deciding to stop now after filming for about 15 minutes because you're already feeling your energy drop a little bit.

Yes. Yeah. I'm feeling a little dizzy. I'm feeling like as time is going on, you're asking questions and more I'm looking at you like what the languages he's speaking. Cut. But this is really cool that we get to uh film again. I know. I You have no [clears throat] idea how excited I am.