Can You See A Black Hole?

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Speaker 1: So if you could visit any place in the universe, where would you choose to go. I'd go to the top of Mount Everest to check out the view. What you would waste free teleportation to anywhere in the universe. I'm going to the top of Mount Everest. Yeah, I mean, how many people get to see that view of being at the top of Mount Everest? All right, Well, I'll have to remind you that this was a one way offer, So if you do that, you're gonna have to climb down by yourself. I'm not teleporting your bath. Great. Um, well, where would you go, Daniel? I would go somewhere near a black hole, like the black hole in the center of our galaxy. What would that look like? That's the point. Nobody really knows what a black hole looks like, and so I want to get close enough to figure it out. I want to go be a tourist at a black hole. You would you would take a picture? I went to see this black hole and all I got with this crazy T shirt and you got ripped your threads by gravitation. That's right, that's right. Yeah. Hi, I'm and I'm Daniel, and welcome to our podcast. Daniel and Jorge Explain the Universe, a production of I Heart Radio, in which we zoom around the universe and zoom inside your head and try to bring one inside the other. That's right. We try to taint a picture for you of all the amazing and incredible things out there in the universe to know about and to see. Because all these ideas are like exploding inside our minds, and we want to share that with you. We want to take them apart, bring them into pieces, send them down the Internet and little electronic bits, so they can reassemble inside your mind and you can also have that crazy, mind blown experience when you realize how insane the universe is. Right, And but I guess the question is are there things in the universe that we can't see? Definitely, there are lots of things in the universe we can't see. I mean, there are lots of things we can see only very slightly. There's things we can see very indirectly. Right, But there must also be things in the universe that we can't see at all. Right, Yeah, there things that we might never see. Yeah, I mean, imagine if the universe was filled with some sort of particle that didn't interact with our kind of matter at all. Right, so I had no it was like dark matter, but I had no mass for example. Um, then we couldn't interact with it at all, and we would never know it was there. There'd be no way to tell if it's there or not. Well to be on the podcast, we're going to talk about one such thing out there in the universe that that maybe we can or cannot see. Can you see a black hole? What would a black hole look like? And what technology do you need to use to detect it and to spot it? That's the topic of today's podcast. Yeah, Like if you were out learning in space and you saw one, and you took out your phone and took a picture, what would that picture look like? Yeah? Exactly what would your black hole selfie look like? Right just before you get shredded by the black hole and slurped up in by the universe? Is the biggest blender slash toilet? What would that awesome last Instagram post look like? And how many lights would you get? That's the that's the real question. Exactly it would be an infinitely dense like is there an option on Instagram to like things in different ways? Like thumbs up? Smile. Black hole. Yeah, so black holes are a fascinating thing, right. You hear about them a lot in science fiction, and they're also depicted often in movies. And I wonder sometimes the folks have that have to put these visuals together. You know, how much research have they done to figure out what would this thing actually look like? Um? Do they just like sketch in their minds what they think of black hole might be? Do they call up a physicist and say what would this look like? Um? Is a huge variety. If you just google, for example, black hole, do a Google image search for black hole, you get a big variety of results. Well, how many variations can there be? Isn't it just a black hole? Yeah? They're all just black right, very clever. No, Um, they all feature some black thing in the center, right that looks like a hole. And then it's what's around them that's interesting. And that's the clue for today's episode that what's around a black hole is the fascinating bit. Some of them have like distorted space, some of them have like gas being pulled around, some of have just like general mystical swirly stuff. Yeah, but I guess it kind of touches on this idea that you know, as humans we are, we like to see it to believe it, right, Like we need to see something to know that it exists. Yeah, we'd like to have the most direct evidence of something before we really think that it exists. And this applies in lots of cases, like you know, in solving a murder, right, you have to be basically you have to have a body to convict somebody of murder, right, no matter what evidence you have. If there's no body, you know, no court is going to send somebody to jail. In the same way, if you speculate, oh, maybe this thing exists out there in space and people want to know, all right, we'll show us one, right. I think that's totally reasonable. Yeah, in the sense it's theoretical until somebody sees it or touches it, right. Yeah. And it applies also the questions of like life. We can get indirect evidence for life on another planet based on what's going on in the atmosphere and changes in the methane rates to whatever. But still people are like, Okay, send something over there with the microscope, let's see it in Actually we want to see it to believe it, right, You're right. I think you're right. Like, if physicists came out with the news tomorrow, Hey, we have have some methane readings from planet the variations in the orbit of planet x y Z three thousand light years away, that tells it there's that there's life there. How many people do you think would believe it? How many people believe is this in general? Yeah, that's another question answer to zero? Um, I don't know. I think physics have a pretty good reputation because we don't We're pretty conservative about making claims. We don't make big, bold claims until we're pretty sure of them. But I think a lot of people would want to see it in anyway, even if you believed physicists, the next thing you would want them to do is like go check it out, Like let's build a bigger telescope, but let's send a ship there, or like I want to go, like what is on that planet? Right? Your curiosity would just demand to see this thing? Yeah? Is that? What is that? The last step in the physics handbook for how do the research is check it out? Check it out? Now, we do a lot of that actually in research, right is we try to visualize our data. We try to show. We try to look at what we're studying and show it in a clear way that that makes it obvious what it is we've learned or what it is we're trying to study. Even for example, you know, like the Higgs boson. You know, when we will look for the Higgs boson, we you could argue with what we're just looking for the Higgs field. It's this thing that fills space. But to prove that it exists, we needed to see it turn into the Higgs boson. We needed to actually identify this particle directly, even though all the theoretical indications suggested that it really had to exist and the universe didn't make sense without it. A lot to indirect knowledge. Until we actually produced the Higgs and could see it, then, you know, we couldn't really claim that we had that it was part of physics, right, even though it affects everything else you see the effects of it. It wasn't until you saw that that that that little particle turned into other particles that you were convinced that it would existed, right exactly. And now let me like get out of that chair and sit in the other chair and argue the complete opposite side of the story, which is that Daniel versus Daniel, all right, which is that's ridiculous because everything we see is indirect. I mean, what does it really mean to see something directly? Right? Does it mean the photons from it landed in your eyeball? You know, most of the stuff we see from space, the photons are not landing in your eyeball. That hit some telescope, and that telescope inverts them from radio into something else, and then you get a picture on your screen. The photons from that thing are not hitting your eyeball. Right, Yeah, but dear, like the sensor in that my telescope is acting as a proxy for your eye, right, Like, I know there's a photon that came from that star and that hits something on Earth, and I believe that the chip, the microchip registered it. Yeah, Okay, So you're saying, you're still seeing it even if there's some indirect proxy, right, if there's a step between you and it where some machine has translated the information from one kind of thing to another kind of thing, right, You're staying that's still seeing yeah, because and I think it has it has to be a photon related right, Like if you told me um, it's kind of harder to believe if it's just like the gravitational effect or you know, the the something else. You know, knowing that there's light coming from that thing makes me believe it more. I see, that's interesting. Has to be light time because for example, you know cosmic great particles, right, they hit detectors and we say, oh, we saw that particle, even if it wasn't a photon um And I would say everything is indirect. I mean every kind of information you get is indirect. I mean the folks who are listening to this right now, they're not actually listening to the sound waves that are coming out of my mouth. They're transformed into electrons and stored on a hard drive somewhere right and those sound waves are recreated except for the live studio audience I have here in front of me. There is that is that all the people who've who have made the pilgrimage to your house and you've trapped them in the basements to be a live audience. I have auditorium in my garage. I mean it's empty right now. Nobody came today. But that's where you're using the laugh track. Well, I would say that it's a pretty subtle distinction. It's hard to make a really solid point to distinguish between seeing things directly and seeing things indirectly, because in the end, I think everything is indirect at some level. Um, I mean, there's there's layers there, but some things are less indirect than others. But yeah, Well, the question was can we see a black hole? And so this touches on like if you can't see if you can't see a black hole, how do we know it exists? Yeah, exactly, And if you can't see it directly, what are you looking at? And the teaser is that black holes, while they're black, actually produce some of the brightest, the strongest radiation in the universe. But before we dig into that, we thought, let's find out what people around town think about seeing a black hole. Yeah, the usual Daniel went out into the streets and as people out there, complete rangers, if they could see a black hole. Here's what they had to say. Do you think it's possible to see a black hole? Maybe detect some radiations from them? Maybe, but I don't think the telescope would do. If I do know that, they are able to probably get pictures of black holes, but I'm not entirely sure. How cool. I don't know much about that, but I feel like, technically you want to say that you wouldn't be able because it's a black hole, so there would be no light, but it maybe in con ts with the rest next to it, it might be possible. Yes, yes you think so, Okay, great? I actually you don't know if it's possible to see it, but maybe you can feel it. You can feel it. Yeah, yeah, this is a really dumb answer. But like TV shows and movies, I think they depicted as if we can, but I really don't. I think it's just for like show, for all of that. So I don't think. What does it looks like on TV or in the movies. It's just like a void, like it's literally like a black hole. Yeah. Oh well, from my understanding based on my the books I reading, I think the black holes looks like just a hope about there's nothing can't see, just like the black daughter on the universe. Okay, black hole, I don't think we can't see with our bare eyes. What about with the telescope? Telescope, I don't think so, you know, right, the light, the light get sucked in. On the other hand, I suppose you can see the absence of in this case, absence of evidence of seven steps and something like that. So yeah, so maybe I changed my answer to yes. All right, a pretty good mix of opinions there. Yeah. People are really touched on the same issues that we were just raising, which is like, what does it mean to see a black hole? Right? One guy even switched his answer mid thought, right, yes, no, yes, yes, no. I like the person who just said yes, like, did they have to have they seen one? Did they have some proof that nobody else has. They spoke with a lot of confidence, you know, like, yeah, wow, that's uh. I'd like to be that certain about anything. I've been funny what they said, yes, how did you know? Or who told you? I know? If there were aliens that came here from a black hole, maybe they would have like felt like I had outed them right, accidentally stumbled across not at all? That would be ridiculous. What are you talking about? Snap? I have never seen a black hole or a green hole or a white hole. And that's how Daniel got fried by a laser gun. So let's dig into it. Let's think about what it's like to take a picture of a black hole. All right, Daniel, here's the question. Can you see a black hole directly? No? Podcast over? Um? No? The obviously the black hole it self is black. Right. And for for those of you who don't know a lot about black holes, remember they are very very dense objects, right, They enormously dense, so dense that they have really strong gravitational pull and the gravity is so strong that even light can't escape them. Right. So the general trope is that something that goes into a black hole, a light, a chair, a banana, a podcast host will never leave, right, which means that they appear black. Well, here's here's the present that confuses me. I thought a black hole was like a point, Like the thing that you can actually call the black hole is actually like an infinitesimal point, right, isn't it. Well that's a great question. We don't actually know what's going on inside the black hole. But let's break it down. The black hole itself, what we consider the edge of the black hole, something we call the event horizon, is the point where any closer the gravity is so strong and you'll never leave. Okay, So if you say, you're right to say that there is a singularity, a super duper dense blob of matter that's infinitely small. There would still be points even if you're not actually touching it where the gravity would be so strong and you could never leave. So there's like a circle of spear around it. We call the event horizon. And so what you would call a black hole then is basically anything inside of the event horizon. That's right, but it's important for people to know that we don't know what's going on inside the event horizon. General relativity tells us maybe it's a singularity. There's a super dense blob of matter there that's dense enough to cause this, uh, this gravitational hole, so that this to create this event horizon, but quantum mechanics tells us that's impossible because you can't have so much stuff in such a tiny isolated spot. So we don't know what's going on inside it. So generally, when we talk about the black hole, we mean seeing inside of the event horizon, or seeing this this object which is essentially like a black sphere, right, and and that can be of different sizes, right like between the event horizon and the actual middle of the black hole. That distance can vary, right, like you can have a little black hole, or you can have a huge, huge black hole. Right, yeah, exactly. You can have tiny, little, cute black holes or enormous black holes and they would look like different size black balls basically. And the difference is in the mass. Right, the more mass you have, the further away you can be from the black hole and still have enough gravitational pull that you can't ever escape. So the mass of the black hole determines the size of the event horizon. Okay, so if you call the black hole basically the event horizon, which is defined as the sphere at which from which no light escapes, then by definition you cannot see a black hole. That's right. By definition, you can't see it. But there's always a caveat in physics, right, And in this case, you know, black holes do give off a tiny little glow, all right, I mean they are black, right, nothing can leave them. They don't reflect any light because the photon hitting them get sucked in. But this clever guy named Stephen Hawking says that they do give off a very very little glow. It's called Hawking radiation. And so so what what is that? It means that at the edge of the event horizon. It's kind of leaking radiation, right, yeah, because remember that particles are always doing crazy stuff, and sometimes a particle very close to the event horizon will split into two particles momentarily. This is a normal thing for particles to do when they're going around their business. They split into two particles, and then they come back, like a photon might turn into an electron and positron and then back into a photon. So what can happen if it's very close to the event horizon is that one side gets bumped out of the event horizon while one side is in the event horizon if the photon is like right on the event horizon. So once I get sucked in and the other side leaks out, and that's called Hawking radiation. Wow. So the way you would see that is at the very kind of surface of this black sphere, you would see kind of as kind of a boiling, right it would. You could see kind of these particles just kind of popping out, Yeah, exactly. And the how how often happens depends on something of the temperature of the black hole. So Stephen Hawking was the first person to think about black hole thermodynamics I know you can have a hot black hole and a cool black hole. I know exactly. Um, you can have a spicy black hole in a mild black hole, and there's al sorts of different black holes. No, it's actually a really interesting question, sort of philosophically and physically, is how many properties can a black hole have? You know, what can you know about a black hole? But that's a whole other topics black hole. But but you should know that this hawking radiation is really really mild. Like you know, it's a few particles here and there. It's not something that you could reliably detect. It would be really hard to see that over the background of anything. But the point is that a black hole ifn even if you're looking straight at it, it wouldn't be perfectly black, right, Like you know how in a computer you can have zero value for black. If you look at a black hole, it would you would see just a little tiny glow, right, It wouldn't be a perfect black yeah, just a little tiny glow. I don't think it's I don't think it's possible to detect that with any sort of current technology. Um, but I think we should you know, for those listeners out there who are who are very knowledgeable black holes. I want to give a shout out to those folks. They do emit hawking radiation. But as you say, with today's technology, that's not detectable. Right. But if you were there and you had a perfect selfie camera, you would you would take a little bit of stuff there, Yeah, but you would have a hard time arguing that it came from the black hole because you might just be picking up random photons, right, So distinguishing radiation from the black hole from radio from something else nearby might be very difficult. That's that's why it's hard to see things that are very very soft, right, because they look like a lot of other stuff. Well, you could also see a black hole if it floated in front of something bright, like you would see like if it passed in front of a big sun, then you would see this little black circle, right, Yeah, exactly. And so one way to see a black hole is he include something else right for it to block something bright. Um, But that has to be just the right arrangement of stuff, right. You have to have something bright line up exactly with the black hole. And it's not like we have remote control where we can like say Hey, what would happen if I zoom this star over here? Or let me just like pan back and forth across the sky moving stars around until I noticed one of them disappearing. Right, you have to be in the right place at the right time and be looking for this kind of thing. Alright, So I guess the answer is no, you can't see a black hole directly. Yeah, I think the answer is no. The Comble caveats. Right, there is hawking radiation which maybe in the future we could detect and you could see it indirectly by seeing it block the things behind it. Okay, well let's get into this stuff that you can see from a black hole. But let's take a quick break. All right, we're talking about whether you can see a black hole, and the answer is no. It's it's called the black hole for a reason. It's black, that's right. But this is like the podcast of Caveats, because everything we say we're gonna have to have a qualifier and explain, and in this case, the qualifiers a pretty big one, Like, yes, you can't directly see the black hole because it doesn't give off photons, but it has a pretty big effect on the stuff near it, and that can turn out to be very easy to spot. Yeah, you're telling me that black holes are at the center of the brightest objects in the whole universe. Yeah. In fact, when people saw these things they saw they're called quaisar, they were so bright that they were puzzled. They were like, what could these things be? It was a big mystery because they knew these things were really far away sometimes, yet they were so bright here on Earth, which meant that they must be incredibly bright where they are. And people were really puzzled. They were like, what could be so bright? Right, it's not just like a bright star. You were telling me. These quasars are a thousand times brighter than the entire Milky Way galaxy. Yeah. And so what happens is that the black hole has a huge effect on the stuff near it. Right, So before you actually fall into their event horizon and disappear, it's not like it's a you can just hang out there and have a picnic. Right, It's a pretty intense gravitational experience. Stuff is being sucked in. You're like at the mouth of a vacuum cleaner, Yeah, exactly. And stuff is being really smushed and pulled. And so if you're like a big blob of gas, for example, near the event horizon a black hole, then you're being swirled in. This is called the accretion disc accreating means just like you know, adding, So the stuff that's about to fall into the black hole, and this stuff is getting squeezed. And what happens if you have a bunch of gas and you heat it up by squeezing it, right, is it? It's gonna emit radiation? Right, All that energy, the squeezing of it from the gravitational field gets turned into radiation off an X ray radiation. So it's not the black hole that's super bright, but it's just like all the stuff waiting in line to fall into the black hole that's making all the noise and the crazy light. Yeah, exactly exactly, And it's like the paparazzi surrounding a star celebrity or something, right, And but it's direct. It only happens because the black hole is there, right, the black holes having this effect on the gas. It's causing the gas to emit. And so you could say that you could even say that the gas is part of the black hole. Right, it's a totally arbitrary definition. To say the black hole ends at the event horizon. You can says the black hole you know, includes all the stuff in the accretion disc. It's like on deck to get sucked in. It's like the band. It's not just the band. It's the band and the roadies and the groupies exactly. That's right. It's part of a community, man, and it's a movement, not a not a band. Yeah, no, Man is an island even a black hole. Um. And but when this happens, when you get the right kind of stuff assembled near the black hole, it's incredibly bright. And so yeah, these quasars can be thousands of times brighter than in the entire galaxies. But but not every single black hole has one of these things. Oh, I see. So, so a quasar is just a black hole, but the right kind of stuff around it that that is glowing and exploding kind of it's kind of exploding, right or squeezing And yeah, it's definitely it's being squeezed and it's not happy or I guess it likes it. I don't know. And it's emitting a huge amount of radiation and the spectrum is really broad, you know, it's like X ray to radio it's on a lot to channels. And that's one of the things that puzzled people for a long time. It's like, what is doing this. It's such a crazy tense source. It's super far away, um. And you know, part of it the mystery was that, like the milk e Way doesn't have one of these things. We have a black hole in the center of our galaxy, but our galaxy doesn't have a quays are. It's not immediately incredible radiation. Yeah, whoa wait, so um, some black holes are just there and they're sucking stuff in, but they don't light up to the space around them. Yeah, because they don't have that stuff nearby that gets lit up. Right. It's like one in a hundred galaxies have a quasar have just the right assembly of stuff to get squeezed into met this crazy radiation. And how did we figure out that that's what was going on with these super bright objects. Well, you know, first we just didn't really believe the data. We were like, something must be wrong with these measurements because these things can't be so far away and so bright. Um. But you know, they checked and they double checked, and it turns out they were correct. Um. And then they started to believe that, like, okay, well, if these things really are super bright, what could they be. And then they noticed that they were coming from the you know, more accurate measurements their direction. They noticed they were coming from the centers of galaxies, and then they started to associate that with black holes. And then people build models. They're like, how could you get a black hole to give out this much radiation? And you know, somebody had the idea, maybe it's the stuff near it, and they started building simulations of it, and then they can reproduce the kind of thing that we're seeing in simulations, and that convinced them, Okay, we understand what we're seeing. What we're seeing is crazy radiation from the neighborhood of a black hole. Wow. Is it just the amount of stuff, Like if there's a lot of stuff around a black hole, then you'll get these quasars or is it some other strange factor. Yeah, it depends a little bit on the stuff too, Like rock doesn't, you know, give us as much radiation as gas, for example, So more gas and less dust you get more radiation. But it's the kind of thing that seemed to happen earlier in the universe, and that's not something we understand. Like a lot of these things are also really far away, because further away means older, right, the farther away something is the older the light is that's coming from it. And so for some reason we don't understand quasars aren't really being made anymore. There's sort of like something that happened earlier on in the party that is our universe and sort of out of fashion now it's like the eighties, right, grinding, flashy, but no now now a little now, a little silly looking to be honest, Yeah, exactly in hindsight, you know, kind of intense um and pretty awesome, but maybe not something wasn't doing any more. Yeah, so something the universe used to do a lot more of, you know, when he was younger, for reasons if we don't quite understand, but it must have to do with, you know, the distribution of gas and dust and galaxies and how that's grown up, and supernovas and the cycle of stars and it's all part of that really amazing story that that is the history of our universe. So some black holes, if by one in a hundred, you can definitely see because they have they become quasars with all this stuff around them exactly. And I would say that that's seeing a black hole because there's no other way to make these things. Like a quasar means a black hole is there, and so that's you know, it's the black hole sending you a big message like, Hey, I'm destroying everything around me. Pay tension. That sounds like like my daughter And on some days, did you just compare your daughter to a black hole? Beautiful unique, uh stellar stellar miracle. She sucks in knowledge, right, she's just like a black hole for information, right, that's what you meant. Yeah, yes, a galactic miracle. Really, she's an incredibly powerful force. But but but it's not seeing all the black holes because not all of them form quasars. That's right. Then there's some of the quasars that are even weirder than that weird quasar. Yeah weird. I mean quasar is already are kind of weird. But sometimes the quasar will do this thing. It will create a galactic jet. And so if you imagine, like the black holes at the center of galaxy and galaxies are usually flat, right, like not like a jet you right around in, but like a like a like a stream of stuff, not like a jet you right around in at all. Although if you are riding around in your private jet right now listening to this podcast, please send us a donation because that you have enough cash. Um, please give us a ride. We'll do a podcast from your jet, lighting cigars, from burning hundred dollar bills. Um. No, this is a like a jet of stuff. Like it's the stuff that comes out of the back of a jet engine. That's why it's called a jet, right, because it creates a jet of stuff. And so if you imagine a galaxy sort of like a cinnamon roll, because a big flat swirl, these jets shoot up away from the plane sort of like above and below. This is enormous stream of really really high velocity stuff getting shot out from the top and the bottom. It's almost like an escape valve, right, Like, they's so so intense and it's swirling that it just kind of all, let's lose in one direction. Yeah, And these things are huge. I mean, if you see pictures of galaxies with jets, the jets are like the size of the galaxy. These are not just like tiny little um valves, you know, whistling off at the end of the day. This is like a huge enormous um spew of stuff going like at relativistic speed. Right, and if they do this weird phenomenon, they're called something different. They're not called quasars anymore, right, Yeah, they have a they graduate have an even cooler name. They're called blaze ours. I don't know if that's a cooler name. Oh, blaze aren't much rather be a blazer and than aquaz than a quasar. Oh yeah, Quazar sounds sort of iffy. There's like a question. There's like a question you name about quasar. It's like what am I? Am? I a black hole? I'm not really sure I'm quazing. It sounds like a quantum star, you know, a quasar. A blazer. A blazer just sounds like a you know, bluzz or No, it sounds like the coolest thing you could wear to a faculty meeting, Like, Hey, I'm wearing my blaze in the eighties. Maybe in the eighties, Daniel, you'd buy your blazers with the giant shoulder pads. No. But the reason they're called blaze oers is that some of them are pointing right at the Earth. And if they point right at the Earth. The physics of it, the relativity of it enhances the brightness of that jet, like by huge factor. If it's pointing right at you, then relativity increases the intensity of it. And then they're just like ridunculously bright. Wow, much brighter than even quasars. Brighter than even quasars. Yeah, and it's fascinating because they're super bright, and we don't know, like why do some quasars have jets. You know, it must be related to the magnetic fields. That's why it gets like siphoned off. Um. And then we talked to another podcast episode about neutron stars that sometimes turn into pulsars that admit radiation along the pole. Must be something similar to that, some huge forces that are sliping off all this material and sending it up and down. But we really don't understand it. It's a huge mystory, But this is only like one inten Quasars have these jets. Yeah, now you're talking about a one inten out of one in a hundred black holes become these blazing, blazing saddles of bluzzy blasts, and that's see exactly. Blazars are rarer than quasars, which also makes them cooler, Like you've got lots of quasars at the party. When the blazar shows up, everybody pays attention, right, But I guess the point is that they these things only happen around black hole. So if you see a blazer or a quasar, then you know there is a black hole there, and you're you're kind of sort of practically seeing it. Exactly, it's very clear evidence that the black hole is there. So yeah, it's it's how direct is it? You know, the black holes creating this huge stream of radiation that's hitting a telescope which then gets downloaded to the internet and you whiz by it on your Twitter feed and see this picture for point oh two seconds. Um, have you then seen a black hole? I would say, yes, Well, it's kind of cool that the black is things in the universe are also the brightest. That's pretty cool. Yeah, exactly, exactly, the darkest, dankest things in the universe also create the brightest sources of radiation. There's some poetry there, and the universe always ends up being poetic, right, like in the like in the eighties, exactly, hot pants and poetry. That's what I remember from the eighties and hammertime. Oh wait, that was nineties. Sorry, that was the nineties. Sorry. Well, let's get into the other ways that you can see black holes quote unquote see. But first let's take a quick break, all right, I know, so what are other ways that we can see black holes? So we can't see the black holes themselves, and sometimes they're really super duper bright as quasars or blazers. But what about all the other black holes? How can we possibly see them or know they're there? Yeah, so I was thinking about this. I came up with three ways to see black holes today. But then there's a bonus way we'll talk about at the end. It's only going to be possible starting tomorrow. So way number one is actually the way that we discovered the black hole the center of our galaxy, the Milky Way, And that's again indirect in that it affects the stuff around it. So we're talking about quasars, how they squeeze gas and make them radiate. If you're not lucky enough to have the right kind of gas near your black hole to make a quasar, you can still have a big impact on the stars that are there. Just the gravity will change the orbit of those stars. So you can see it because if you see a lot of stars kind of going around something really really massive, then you know there must be a black hole there right exactly. And there's a team I think that U. C. L A that's been pointing a telescope at the center of the galaxy for a long time just to watch the orbit of these stars. And they see the stars moving around something invisible, something they don't see in a way that's consistent with something really really heavy being there. So we don't know that it's a black hole, but we know that there's some really dense blob of matter that's invisible right at the center of the galaxy. So that's pretty good evidence. And it's a black hole. And but invisible you mean like it doesn't shine like a star. It's not like a gigantal star. It's just something that's really massive but doesn't shine. Yeah. Actually, and remember it's also difficult to see the center of the galaxy. It's not like a clear view because all the gas and the dust between us and that you have to see these things in non visible frequencies of light, you know, like radio waves and X rays and stuff like that. Um, So even though you have like really seeing it directly. But yeah, they don't. This black hole doesn't give off radiation directly, right as we were saying, And it doesn't induce radiation and this stuff around it so effectively it looks like there's nothing there, but we know that it's having a gravitational effect on the stuff around it. So it's sort of like the way we see dark matter, right, we only see dark matter through gravity. We're pretty sure it's there um and not seeing it like, well you know it's it's um indirect evidence. But I would say everything is indirect. Yeah, Like I always thought it was pretty cool this idea that if our sun here in our Solar System suddenly turned into a black hole, like all that mass only compressed down into a black hole, Like things would kind of keep going the same way, would they Like, the planets would still orbit in exactly the same way they are now. And so even though you couldn't see anything bright in the middle of the Solar System, you could still say there's something there dark, yeah, black, and that has all that mass. That's true. It wouldn't change the orbit of the Earth, but it would have a pretty big effect on life on Earth, right, I mean things would get a little dark. Yeah, exactly. The gravitational pull of the Sun depends only and basically on the mass of the Sun. Doesn't actually matter what the distribution of the matter is um as long as the Sun's radius as smaller than the orbit of the Earth, it all averages out to be the same as just like one particle with the mass of the Sun at the center of the Sun. So if the right the Sun collapsed into a black hole, that wouldn't change the orbit of the Earth, right, things would just get a little chilly. Exactly. Likely you've thought about this scenario. You have specific plans for what to do if the Sun goes black hole. Yeah, I know, well it thinks it would be over. You would just see the black hole and you'd be like, all right, I've seen a black hole. You're like, I'm gonna call Daniel and Jorge and let them know their pod cast is now out of date. Alright, So tell me, what are the other two ways that we can see let holes. Well, another way is from gravitational waves. So folks might remember that we saw wiggles in space and time from black holes merging with each other. So this is two black holes spinning around each other, getting sucked in by each other's gravity. It's like I'm gonna eat you, know, I'm gonna eat you. Eventually they just like eat each other and become one super big black hole. And when that happens, it sends off these ripples in space and time. Right. Remember, we think about gravity not as a force, but as something that distorts space and time with mass, like a shock wave. Yeah, it's like a shock wave. And these things when they orbit each other and they and they emerge, it's a lot of acceleration that creates these wiggles in space and time. And we can see those with this awesome device called lego Um, which sees these ripples in space and time. They've seen like eleven merger so far. So yeah, but it sounds like a lot. But knowing how many black closed are in the universe, it's actually kind of a rare thing, right, yeah, exactly. But they can only search a very small volume of the universe so far. Right, Things that are sensitive that they're sensitive to that have to be pretty big black hole mergers, and they have to be near enough by that the black hole that the gravitational wave would have reached us for example. So you know they're upgrading and they're looking in a larger and larger volume all the time. But we wouldn't have these black hole merger events if you didn't have black holes. Right, So that's another like piece of evidence. The black holes are real, that they're out there. We've seen them in another way. I think it's cool to see things, you know, and we call this multi messenger see them with lights, see them with particles, see them with gravitational waves. It's like lots of different ways to probe the same thing, and you can ask different kinds of questions and if then, if then, if your model of what's going on is wrong, it's another way to figure that out, to get a clue as to what might actually be happening. Right, So you can't see the black holes, but you can see they're the shock waves of their crash. Yeah, exactly, all right, So what's the last kind of a way that we can see a black hole? And my last way is my favorite way, it's my fantasy way, right, which is what if what if we could see them more directly because we could create them in the lab? Right, So this is um, you know, I like to see things directly. We were talking earlier about like if you want to believe it, you got to see it. I think it's more than that, Like, if you want to believe it, you are got to be able to make it. You're gonna be able to reproduce it. Like is the Higgs boson real? Well, if so, we've got to be able to make it. Like, let's isolate the conditions needed to create it so we can really understand it and we can control its creation and you know, study it. So that's what we're trying to do with the Large change on collider. We're trying to create these really really tiny and super duper many cozy black holes so that we can understand how they're created and the radar wish they've created and what happens to them. Really, is that really a project, like a project make black holes? I know you have called kinds of projects like dark matter and antimatter and looking for particles, But is there actually like a team that's to make a black hole team? Yeah, Yeah, that's the that's the project. You have to understand Also that the large Hage on collider, we just do the same experiment over and over again, which is we smash protons together, and then there are different teams analyzing that data looking for different stuff. Because you can't control what happens when you smash two protons together. Basically, everything that can happen will eventually happen. You just gotta look to all the data see, oh, do we make any higgs is? Do we make any top corks? Do we make any dark matter? Do we make any black holes? So the black hole team is not doing anything different from the other folks in terms of the actual experiment that are not inducing black holes to be made, but they're looking through the data to see if there's evidence that black holes were made. Right, Well, I think we should get into the wisdom of making black holes here on Earth. Um maybe in another episode, but I let me just add a very quick reminded of folks who are out there who are worried. Uh. Number one, we're very confident this is safe that if these black holes are cre they would evaporate and then no danger to Earth. And if you are worried about it, there's a website you can check called has the hag On Collider destroy the World yet? Dot com? And we've promised to always keep it up to date, Are you sure? Yeah, if you check that website, then you know the world has not been destroyed. What if you're you know, credit card subscription ends or you're gonna send the whole universe into a panic. If you don't have Internet, there's nothing I can do for you, then you have bigger problems, all right. So that's that answers the question can you see a black hole? And it sounds like the answer is, you know, you can't see it directly, that's what it's called a black hole, But you can see all this stuff around it and the effect that it hasn't on everything around it. And I would say that seeing it indirectly in so many different ways, and understanding the physics of it pretty well, I would say that's seeing it. So I think we all understand what it means to see a black hole, but we might disagree about whether that is seeing it or not. Right, right, But taking a picture of it, like a photo from your phone, we're still pretty far away from that, right. Yeah. And you know there is a new telescope coming online called the event horizon telescope. Especially it's basically the patching together lots of different telescopes they're gonna trying to image the center of our galaxy and understand exactly where is the edge of the black hole, Where is that event horizon, where is all the stuff around it? And you know it can't see the black hole directly, but by studying in detail all the stuff that's around the black hole will get a lot more information about the black hole formation and the black hole physics and is the black hole spicy or is it mild? Right? All this kind of stuff we want to know about black holes? Cool, Well, do they have an Instagram account that I can follow so that you know when they finally post pictures I can see. I don't have any Internet, so I can't answer that question for great. So the world could have ended right now thanks to you guys, and we wouldn't know. But you should say tuned because the event Horizon Telescope is going to release their first ever results tomorrow. That's right, Wednesday, April tenth will be the date humanity first glimpses a black hole. Now, of course, we're not going to see the black hole directly. The event Horizon Telescope uses radio telescopes from all over the Earth and stitches that together to penetrate the gas near the galactic center and see all around the black hole. So what we're gonna get is we're gonna see the first image of the event horizon of a black hole, which means we're gonna learn the shape of a black hole. Is it a sphere, is it a square? Is it a donut? We're going to find out tomorrow. Laugh anticol reminder that there are still things in the universe out there that are complete mystery. You know, we haven't seen them, We definitely won't know what's inside of them. Yet they exist and we know they exist. It's pretty cool, yeah, And I think that's one of the jobs of physics is to like figure out ways to probe this stuff. How can we get some information from the universe. How can we ask questions and just the right way so we can get some understanding of what's going on out there, even when we can't see it directly, because that's the easy stuff, right right. Well, coming to you live from side of dog Hole. This has been the podcast Daniel and Jorgey explained the universe. Good luck everyone surviving the black hole apocalypse. Thanks for listening. See you next time if you still have a question. After listening to all these explanations, please drop us a line. We'd love to hear from you. You can find us at Facebook, Twitter, and Instagram at Daniel and Jorge That's one Word, or email us at Feedback at Daniel and Jorge dot com. Thanks for listening, and remember that Daniel and Jorge explained. The Universe is a production of I Heart Radio. 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