Daniel and Jorge Explain the UniverseDaniel and Jorge talk about whether black holes can be blocked or can block other objects.
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Hey or Hey. Are you a fan of Pokemon cards?
M Oh yeah, a little bit. My son used to play them.
My son also, though I think he mostly collected and traded them, I don't think he ever actually played with them. M.
Yeah, I think that happens a lot, although I did play with him for a few times. It's a pretty interesting game.
And do you have any of those cards with like super awesome powers?
Yeah, they have pretty good names, like flame Body.
My personal favorite is the card that can do a black hole eclipse.
Although that sounds kind of like a random combination of words from physics that they just kind of put together.
I think that's the same way that physicists name things though.
Ah, so you admit it. It's all random.
We just type the words into an online random number generator and that's what we go with. M.
Maybe they have a bunch of physicists working for Pokemon just in case that the whole physics caurer doesn't work out. You have a promising career working for Pokemon.
That's always been my backup plan.
Hi.
I am Hoorham and cartoonist and the co author of Frequently Asked Questions about the Universe.
Hi. I'm Daniel. I'm a particle physicist and a professor at UC Irvine, and I probably have hundreds of dollars worth of Pokemon cards somewhere in the closets of my home.
Are they wrapped in individual plastic though, to keep them in mint condition. Otherwise, I'm not sure they're worth that much.
They have definitely been prepared as an investment in the future.
That's how you plan to pay for your son's college education.
I think that's how my son plans to pay for his retirement. Yeah.
Wow, if it's worth that much, maybe they should conveniently disappear from your closet.
Only if I could find them in my son's closet. I think that's part of his security plan.
Oh yes, it's such a mess. It's like a black hole in itself. But anyways, Welcome to our podcast, Daniel and Jorge Explain the Universe, a production of iHeartRadio.
In which we try to clean up the mess that is this universe and all of it's crazy, confusing glory. We dig right into everything that doesn't make sense, everything that should make sense, and things that might never make sense. We talk about the biggest questions at the heart of philosophical inquiries about the nature of our universe, and we talk about practical stuff like how things around you actually work. We dive into all of these questions and try to explain to you what scientists do and do not know about.
Them because it is a pretty fun universe full of interesting and amazing characters, not all of them with superpowers like Pokemon characters, but there are a lot of interesting objects out there in the universe with seemingly super powerful powers.
And it is our belief, or at least our hope, that the universe does make sense, that it's following some set of rules, and that if we dig into it hard enough, if we use our brains, we come up with a clever set of experiments, we can figure out what those rules are. That in the end, there isn't magic in the unit, but that everything can be explained with science. I'm not sure the same can be said about Pokemon powers.
Wait, are you saying that Pokemon aren't physically accurate there? How do you know, Daniel, I'm not sure we have to suspend disbelief. But I did do a bit of research into what the black hole eclipse move is for the Pokemon character, and here's the official description. The user gathers dark energy with its Z power and forms a black hole that sucks the opponent up.
Mmmmm.
Interesting. That seems like a bit of a dangerous weapon there, because once you start the black hole. I guess can you turn it off or is there a Z switch for it?
It depends on what your Z power can do. If you can tap into dark energy and expand or contract space, then hey, you have got a lot of options.
Well, there is the idea that maybe there are unknown forces in the universe we haven't discovered. Maybe the Z force is one of them.
And if I discovered an unknown force and called it the Z force, would you be impressed with my naming?
I guess, I mean, try out any of the other letters in the alphabet. First.
The Z force makes me think it's related to the Z boson, which we know is a very feeble boson. It carries the weak force, probably not capable of making black holes.
So there is technically a Z force in the universe right now, like the force made by a Z boson is technically a Z force.
Yeah, that's right, though I'm not sure you can use it to gather any dark energy and throw your opponent into a black hole. But hey, best of luck to you.
How do you know, Daniel? Have you tried?
I haven't tried, but I'm going to write a grant proposal to the Pokemon Science Foundation to see if I can get some funds to try it out.
Yeah, the PSF, they fund a lot of work out here. But technically, in a multiverse, isn't it possible that there are Pokemon characters out there?
I mean, if you say in a multiverse, isn't it possible? Then I suppose almost anything is possible, because in some theories of the multiverse there are universes with other laws of physics, which basically allows almost anything to happen.
Wow, there you go, it's official here in the podcast, Daniel thing. Pokemon are real.
They are a really good investment in my son's.
Future and a real possibility. But it is interesting. How did you end up googling Pokemon powers online? What's going on there? Daniel?
No, I was googling black hole eclipse, of course, in preparation for today's episode. And the top hit was not black holes or eclipses or anything scientific. The top like ten hits were all about Pokemon.
I think that tells you a little bit about the priority of the Internet. But it is interesting. What do you think is going on inside the head of those Pokemon creators, artists and writers when they come up with these things?
Right?
Because they used to work dark energy. They must know a little bit of something about physics.
Well, you know, I think as they make more and more Pokemon characters, that have to be more and more powerful or as my son would say, totally op. And so they want to come up with something really dramatics, something really crazy. And I guess black holes are on the top of the list of like aspirational powers as to whether you could make a black hole using dark energy. You know, we don't really know what dark energy is at all. We just know that it's accelerating the expansion of space and separating the black holes from each other. So if anything, it's keeping black holes from getting bigger.
Well, I guess my question is what kind of energy car does the attack youse dark energy cars? Is there such a thing?
If there isn't such a thing, then there should be Pokemon Science Foundation. Please fund that.
There should be a science type Pokemon. You know there's like a water type, fire type. I mean, there should be like a physics type.
We've exhausted my knowledge of Pokemon. Now I have nothing else to contribute to this conversation.
I went a little op on you. Yeah, all overpowered you. But it is an interesting name. To give a power to a fictional character. But it kind of makes you think, is it actually possible for something like that to happen?
And we know that crazy things happen out there in the universe. We are constantly surprised by what's going on in the hearts of other galaxies and even in between galaxies, and so you should never say never.
So today on the podcast, we'll be asking the quoestquestion. Can a black hole be eclipsed? And can you use it to suck up your enemies? Is the question that a lot of kids are probably asking, and maybe some physicists.
Please, if you do have the Z power to manipulate dark energy to create black holes, don't do it. You might win the battle and then destroy the planet.
Although they'll give you a Nobel prize, though, wouldn't they.
In the five minutes between the creation of your black hole and the destruction of the Earth. I'm not sure the Swedish Academy acts that fast.
I don't know.
I've seen you talk, Daniel. You'll sacrifice anything for science.
If you have such a Z power, create a black hole out in the depths of space where we can study it.
Please, I guess if you have that kind of power you can afford to go out into space.
Right, Maybe you also have the X power and the WY power right right?
Although I thought the why power was physicist superpower or is that the philosophers?
It's the four year old's power? Why? Why? Why? Why?
Yes, it's an interminable source of energy. It's an interesting question, and as usual, we were wondering how many people out there had thought about this question whether a black hole can be eclipsed.
So thanks very much to everybody who volunteers to answer these questions in advance. We're very grateful to you, and we hope that you enjoy hearing your voice on the podcast. If any of you out there would like to participate, please don't be shy. Write to me two questions at Danielandhorgey dot com.
So think about it for a second. Do you think a black hole can be eclipsed? Here's what people had to.
Say, assuming the definition of eclipse is for one body to obscure another body from a given dvantage point. Sure, I don't see why a black hole could not be eclipsed by another celestial body.
I thought that might be how we discovered them or something I guess a black hole can be eclipsed.
I mean normally, an eclipse is when the light from something is blocked by something else in space. So as a black hole doesn't have any light amissing from it, I wouldn't have thought it could be eclipsed as such. But I guess if you get something massive enough in front of it, in between us and it, then it would be eclipsed.
I don't see why not. As long as something subjectively larger than them is between them and the observer, it would eclipse. The black hole might have to be subjectively larger than the disk around it to really have a shot at it.
Well, the concept of eclipse, the way I understand it, is that light from a star is blocked from Earth's view by an intervening body. So since black holes do not emit light, I don't think they can be eclipsed.
I don't think so because I believe when a black hole's mass passes before a gravity you see lensing effects. And I don't know I've I ever heard of one being eclipsed before.
Yes, I think they can do if there is a planet or star closer to us in the right alignment with the.
Black hole.
Yes, I think they can be eclipsed.
Yes, I think it can in the sense that is coming in front of something else. But like instead of blocking the light like the moon, we block the Sun's light, I think it would just absorb the light of whatever is behind it.
But it could also have this.
Gravitational lensing effect where the light of the objects that aren't directly behind it kind of get curved due to the black hole and we perceive it in that way. So that's kind of the black hole version of an eclipse.
Yes, they can be eclipsed.
Let's say instead of our Sun, it will be a black hole like we heard our podcast Danielle and Hoorhea. We would need to be at a safe distance from it and we can safely go around it. And if we have the moon, that would be between us and the black hole. I don't see why not the moon connect the sight of the black hole?
All right? A wide range of answers here. Somebody said, why.
Not always a good answer when we're talking about physics at the universe.
Why not? There's the multiverse, Doctor Strange says, anything can happen in the multiverse.
Or do you think they were taking it as a proposal like, hey, should we make a black hole eclipse? Why not? Let's go right now. I'm up for it.
I guess it made me think, what do you mean by eclipse, like in terms of attention or in terms of blocking its light? But it's a black hole.
Yeah, it's a good question. And I noticed that there was like two different interpretations of eclipse there, one the black hole being eclipsed like something blocking light from a black hole, and the other of the black hole doing the eclipsing, like passing in front of something else that makes light. So there's sort of two possibilities there.
Interesting, and I guess we're going to argue about which one is more correct. For the next hour, we're going to talk about both possibilities. Of course, we're going to do the quantum superposition. We're going to do the forwards and the backwards. All right, Well, let's start with the basics here at Daniel. What is a black hole?
First of all, so we don't really know what a black hole is in the actual universe, and we don't actually even really know if black holes exist as described by the theory. We have this concept in general relativity that if you get enough stuff together, its gravity will overcome any sort of internal strength, any power of the material to resist being compressed. The gravity will eventually get so strong that it will just squeeze it down further and further and further. And as it gets denser and denser, the gravity gets stronger and stronger, and you get this crazy runaway effect where gravity essentially becomes infinitely strong in a tiny little dot, this singularity at a point in space where you have not infinite mass, but infinite density because gravity has compressed some blob of stuff down to a very very small distance. And because it's compressed it so far, it means that you can get pretty close to a lot of mass, which means the even nearby it would be very strong, so strong that we think that it curves space so much that light cannot even escape it. So if these things are real, if they're out there in the universe, then whatever falls into this black hole you will never see again because light from it cannot escape.
Would you say it's an actual hole in space, Daniel? You know, if you define a hole as something that you can fall into, then it's technically it is. That's why it's called a hole. Right.
If you accept the general relativity view of it, it's kind of a hole because it makes a portion of space that's cut off from the rest of the universe. It's like a little sub universe, and once you enter that sub universe, you really are cut off from the rest of it. I mean, inside the black hole, you can still see the rest of the universe. Light from the rest of the universe can still reach you, so you can see out from it, but nobody can see into it. Right, So in that sense, it's a hole in space.
Right, Although that's assuming your eyeball is still in one piece when you're inside of a black hole.
Right, Yeah, precisely, assuming that you survive long enough to look out into the black hole. And black holes can come in all sorts of sizes. You can make a black hole in theory out of a pretty small amount of mass as long as you squeeze it down to a small enough radius. You can also make black holes out of enormous masses. Some of the things out there that we think our black holes probably have millions or billion times the mass of our sun. Those black holes are really really big, and if you fall into one of those, the gravity at the outskirts of the black hole is not actually that strong. I mean, it's strong enough to suck up light, but it's not so strong to like tear you apart to spaghettify you. So you might be able to survive the very first few moments of falling into a really really big black hole.
Yeah, and then you could take a selfie, although you can never send that selfie to anyone.
Hey, selfies are just for yourself, right, That's.
Why they're called selfie. Ironically, that is the opposite purpose of a selfie.
This should be called that everyone else's.
But it is interesting what you said about black holes having a size, because it's it's like a hole in space, but it does have volume, right, Like, it does occupy three dimensional space. In fact, it's a sphere in space, right, I mean it just kind of distorted space, but it does sort of occupy a certain you know, length with in height.
Yeah, if you say black hole, you're probably imagining like a circle on the ground, a two dimensional object that things can like fall into and disappear like in cartoon shoe's. But as you say, there are three dimensional objects. So the simplest black hole, one that isn't spinning, would be a perfect sphere and you can fall into it from any direction. If you're looking at a perfect sphere that's perfectly black, it's always just going to look like a circle to you because there's no texture to us, so you can't sort of like tell how much curvature it has. But actually, if you look at a black hole, you don't even really just see a black sphere. It looks even bigger than it actually is because the paths of light around the black hole are really really weird. Like if somebody was very close to the edge of the black hole on the back side of it and turned on a flashlight, you could see it on the other side of the black hole because the light from that flashlight would curve around the black hole, bent by its incredible gravity to your eyeballs. So if you're near a black hole, if you're just looking at it, you can actually see the entire surface of the black hole right in front of you. You can see the front and the back.
Right though it just looks black, right.
Yeah, it just looks like a bigger black circle than it actually is. It's like puffed up, yeah, like puffed up, because in the vicinity of a black hole, space is curved and when space is curved, you can't trust your eyes to be just showing you what is there. You're seeing now an image of what is there, and then image can be distorted, just like if you're in a funhouse mirror and it's not flat and what you're seeing isn't reality. The same is true near a black hole. Light doesn't travel in straight lines anymore, and so what you see is an image just generated by the physical stuff that's there, but it's not a fully faithful image of what's actually out there.
It's a little bit mind bending because a black hole is sort of like a sphere right, sort of has a surface, but it's not really a surface because it's not solid. It's just kind of like the edge of the hole. So it's like a three dimensional edge of a hole. It's the surface of a black hole.
Yeah, and what you call the edge of a black hole is a little bit arbitrary. We usually use the location of the event horizon, the point past which light and particles and nothing can escape, to mark the edge of the black hole. But there's nothing there at the edge. It's sort of like a calculation we do to say where it is, and you can't actually even tell where the event horizon is until the end of the universe. The definition of the event horizon is any particle past this point never escapes. But it's not always easy to tell exactly what can escape and what can't, and so you can't actually know in any moment where the event horizon is. You have to sort of like wait to the end of time and then say, particles that got closer than this, none of them escaped. So here was the event horizon.
Right, because to actually like falling to the hole that sort of almost sort of never happens, right, because time gets so distorted around the black hole that it basically, as you said, happens never.
Yeah. And also there's just like nothing there at the event horizon. It's not like a surface you land on. It's just a point of no return. It's like if you got into your car and you drove too far away from a gas station so that you didn't have enough gas to get to the next gas station. Nothing would happen at that moment when you had gone too far. You would only realize it later like, oops, we forgot to get gas and now we're stranded. The moment when you've crossed that threshold where you're now too far away from the nearest gas station you don't have enough fuel to get one. No warning light necessarily goes off, and the same is true for the event horizon. It just feels like the rest of space. You pass through it, and unbeknownst to you, you are now trapped inside the black hole.
Right.
Although you know, if you're flying that close to a black hole, you can't claim not to have seen it because it's going to look pretty big to you flying close to a black hole, right.
Oh yeah, it's definitely irresponsible space flight, and the same way like you should know if you're about to run out of gas and somebody should be paying attention to.
It, or at least there should be a warning alarm on your space black hole ahead, use your Z powers now. But as you said, it does sort of occupy space because it is an object, although it doesn't have less solid surface. And it's also like moving around in space, right, black holes can move around in space. Even though there are holes in space, they can move around in space. It's like a moving hole.
Yeah, well, there are a thing, right. They are made out of mass and so like everything else, they have a location and then they can have a velocity, but you know, the velocity of the black hole is relative. Just like everything else. If you are moving towards a black hole, you could also say the black hole is moving towards you. There is no difference in the physics of the universe in those two pictures, and so black holes, like everything else, can have location and velocity.
Yeah, there could be one moving towards us right now.
Right almost definitely, because we know that there's a super massive black hole at the heart of the Andromeda Galaxy which is coming for us. Right The Andromeda Galaxy is going to collide with the Milky Way in a few billion years, and so the black holes at the heart of each galaxy are moving towards the other galaxy. So yeah, black hole are headed our way.
Better get working on that Z force, Daniel. We're counting on you.
I only have the P force, the physics force. Other people have to work on the Z force, or I could be the W force for whiteson.
There you go. I guess the Andromeda black hole, that's something we don't want to catch, although if you find a good container for it, I guess, yeah, maybe you do. All right, Well, let's talk about whether or not a black hole can be involved in an eclipse, whether it can eclipse other things, or whether you can eclipse a black hole. But first, let's take a quick break.
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All right, we're talking about the physics of Pokemon, right, that's the title of the episode.
That's right, Pokemon characters use physics on each other.
I feel like that would be a pretty viral title to put on this episode.
What do you think the physics of Pokemon? It might be viral. It would also be totally misleading, but I guess that's how everything goes viral.
But we could do a whole episode on this right, just pick a bunch of Pokemon cars and we'll break down the physics of their superpowers.
Yeah' go like this, Yeah that's totally made up. Yeah that's where Yeah that's ridiculous.
But could it happened? Aren't there books about the physics of Star Trek and Star Wars.
In a multiverse where Pokemon is real?
We are talking about the powers of one specific Pokemon. Which Pokemon has this power? Daniel did? Did you look up the name?
Well, according to my research, it says any non mega evolved non primal Pokemon can use black hole e clip if it knows a damaging dark type move and holds darkenium z and if it's trainer whereas a z ring. So if that made sense to you, please explain it to me.
Wow, there's a lot of preconditions there, so any Pokemon that checks those boxes can use it.
Yeah, apparently any non mega evolved non primal Pokemon. I don't know if there's a lot of them or just one.
You should have interviewed an expert. But anyways, we're asking the question of whether or not you can actually eclipse a black hole or I guess involve a black hole in an eclipse. And you said, Daniel, there's two possibilities here. You can either eclipse a black hole or have the black hole eclipse something else. And so I guess, first of all, Daniel, what's the legal definition of an eclipse?
So, an eclipse is a fun astronomical situation where two things fall along the same line, your line of sight. So you're looking out into the universe and you can imagine a line between your eyeball and some object. If something else passes along that line, then it has eclipsed whatever you were looking at. So if you're looking at the Sun not recommended, and the Moon passes in front of it, then that's a solar eclipse.
Right.
The Moon is eclipsing the Sun because it's passing along the line between your eyeball and the Sun.
Mmm.
Interesting, So if it technically, if I put my thumb in front of me and block out the Sun, I'm creating a solar eclipse. That's what you're saying.
Uh, yeah, I mean your thumb is not an astronomical object.
Have you seen my sun? It's pretty stellar.
It's been a while. So assuming you've upgraded it with your Z powers, then the or his thumb can perform an eclipse. One of my favorite things though about solar eclipses is that they're possible, right, Like, the Moon can block the Sun in the sky, which requires not just that the Moon goes in front of the Sun, but that the Moon is the same size or bigger than the Sun in the sky. The amazing thing is that the Moon and the Sun are just about the same size in our sky, like they can eclipse each other just which is a total cosmic coincidence. The Moon could have been bigger, or it could have been further, or it could have been closer. They don't have to be the same apparent size in the sky, and yet they are.
Yeah, it's a pretty wild coincidence. Although it is also a function of where we are right now, right, because eventually the Moon is going to move further away from Earth and so it'll looks smaller than the Sun.
Yeah, exactly, it gets smaller and smaller every year.
And before like maybe in prehistoric times or millions of years ago, the Moon looked bigger than the Sun during a solar eclipse.
Yeah, And the Sun is also growing in size as it gets older, right, and pushing out more of its layers further and further so the Sun is getting bigger and the moon is getting smaller, And it's a really valuable lesson about coincidences. You know, sometimes we see coincidences out there in the universe and we go, ooh, there must be an explanation for that. It can't be by chance, But sometimes it is. Right, we don't think there's a reason that the moon and the Sun happen to appear to be the same size in our sky, but it seems like a huge coincidence. But sometimes they just happen.
Yeah, And I guess the coincidence is that they're almost the same size and from our point of view in the sky. But it's sort of not a coincidence that it just happens to fly in front of the Sun, right, Because the Moon is you know, spinning around the Earth all the time, and we're spinning around the Sun all the time, and so technically the moon kind of sits everywhere at any point in the sky at some point eventually, right, So it's not a coincidence that it just happens to fly in front of the Sun.
That's right. And most of the things in the Solar system are in the same plane, and so it's possible for them to line up. If the Moon, for example, was orbiting the Earth outside the plane of the Earth's orbit, it'd be much harder for it to eclipse the Sun. But because it moves around in the same plane, then it gets itself between the Earth and the Sun, and of course it doesn't eclipse the entire Earth. The Moon casts a shadow on the Earth, and that shadow moves across the surface of the Earth. When you're in that shadow, then you can see the eclipse. And at the same time, there are people who are not in that shadow who can still see the Sun sort of around the side of the Moon because they have a different angle. I saw the total clips back in twenty eighteen, was it. It's a pretty awesome event.
Yeah, And there's another one coming up in a year or two.
Right, There are a bunch of eclipses all around the world in the next few years, and if you have the opportunity to see them, I totally encourage you. Even though it has no deep astronomical significance, it's just sort of like a cool event. It makes you feel connected to people who have seen these things since prehistoric times and looked up and wondered like, whoa, something is different about the sky today. I wonder what that means.
Yeah, just like I feel connected to my thumb whenever I put it in front of the sun.
Are there times you don't feel connected to your thumb? That's what we should worry about.
Sometimes I feel like the thumb is we're not connecting into deep level.
You know, you and your thumb needs to go to therapy. It sounds like work out these issues.
Yeah, yeah, do you know anyone Maybe there's a good podcast for that.
Maybe I can point you to one.
I couldn't point. Awesome. My index finger isn't talking to me either, so.
It's always a surprise in the podcast. This is a direction I never would have guessed.
Yeah, but it's interesting. So what do you call a solar eclipse? Is when something blocks your view of it? Right, Like, you can also have a moon eclipse, right, a lunar eclipse.
Yeah, that's right. That's when the Earth gets between the Sun and the moon, and so the Moon is then blocked from the Sun by the Earth, and so you can still see the moon, but it's sort of like shaded. It turns a funny color because it's no longer getting as much direct sunlight because it's in the Earth's shadow. So basically eclipses are like when somebody gets into somebody else's shadow.
Right, Or I guess technically a lunar eclipse is like an Earth eclipse if you were standing on the moon.
Yeah, although if you were on the Moon, you would probably call that a solar eclipse, right, because the Sun would be getting eclipsed.
Are you saying it's all relative, Daniel, It's.
All relative and the names are not consistent. That's exactly the lesson of the podcast, all right.
And so it's interesting that you can you can block out the light from the Sun, but that applies also to any starr, Like you can have eclipses out there in space with any star, not just our Sun.
That's right. Stars out there have their own planets, and those planets have moons, and so on those planets there are eclipses happening. Those planets. Moons are blocking that Sun's light and creating shadows which crawl along the surface of those planets around other stars, and maybe aliens are looking up at those and being impressed by the astronomical display. But we can actually see those eclipses as well, because sometimes those planets pass in front of their star, blocking a little bit of the light from that star. So instead of making a line from your eyeball to our sun, now imagine a line from your eyeball to some star far far away, millions or billions of miles away, and a planet can pass along that line. Now, because you're so far away, the planet can't hope to block the entire star, but what it can do is dim it a tiny little bit. And that's actually one way that we discover planets around other stars. We see them making these sort of mini or partial eclipses of their star.
Yeah, it's one way we can detect planets in other stars. And in fact, you sort of look for stars that twinkle a little bit periodically, right with a constant beat, and that kind of tells you, hey, maybe it has a planet swinging around it.
Yeah. You study the brightness of the star and you notice a dimming and it dims periodically. So it dims for like a few days, and then it gets bright again for a fixed amount of days, and then it dims again, and it happens periodically, and that's how you can tell that something is going in front of it and blocking it, because otherwise stars can just twinkle and dust clouds can interfere with your observation. But if it's something regular, then you know that it's probably something orbiting near the star that's moving around it. And so it's a really powerful way to discover these other planets and also to measure their size, because the more dimming you get, the bigger the planet is. And these are always tiny little eclipses. You need really sensitive telescopes to even notice that these things are dimming. You could never see this with a naked die.
Right, And so if you see a star out there dimming and being eclipsed regularly, it might be a planet in its orbit. But it's kind of interesting also to think about that. You know, there are probably eclipses happening all the time with all the stars out there, right, Like maybe even asteroid flies near us or it gets in our way between us and another star. Technically that's an eclipse too.
Yeah, that's probably true, And there eclipses happening that we can't see.
Right.
This technique of seeing these planets relies on the planet lining up with our line of sight to that star. There are plenty of planets out there around stars that are just not aligned with us. Like we talked about how in our Solar system the Moon and the Earth and the Sun are mostly aligned in the disc of the Solar system. But the disc of our Solar system is not the same as the disc of other solar systems. Those are mostly random. I mean, every solar system has its own disc, and the planets mostly follow that disk, but the arrangement of our disc relative to other Solar system discs is kind of random, which means that most stars, when their planet passes in front of them, don't cause an eclip that we can see.
All right, Well, we're talking about whether or not you can involve a black hole in an eclipse, and so Daniel, can can you eclipse a black hole? Or can a black hole eclipse something else?
Yeah, it's a really fun question. Let's first talk about whether you can eclipse a black hole. And the first question is like, well, could you see a black hole anyway?
Right? Like, technically, what does it mean to see a black hole? Like, even if there was nothing between you and the black hole, are you actually seeing a hole? Like that hole is the absence of something, right exactly?
A shadow can't cast a shadow, right, in the case of an eclipse on the Earth, the Moon is casting a shadow on the Earth, but a black hole does it give off anything to create a shadow. And so technically a pure classical general relativity black hole is completely black. If you saw it out in the middle space, you would not see it doesn't give off any light. The only way you could see it is if it was in front of something else that was bright. It was like passing in front of a star and eclipsing it. So a classical black hole doesn't give off any light.
Something could technically block your view of the black hole, right, Like if a planet happened to fly between you and the black hole, you wouldn't see the black hole anymore. Would you call that an eclipse?
That sounds like a legal decision. I mean, the black hole is not giving off any light than is it being eclipsed.
Right, And let's say behind the black hole isn't like a galaxy or something bright, or a cloud of a bright cloud of gas or something, So you could actually without the planet blocking you would see the black hole. But now there's a planet between you and the black hole, so you don't see the black hole, And technically it would sort of look like an eclipse, right, it'd be like a black circle getting blocked by something maybe brighter.
Yeah, that's technically possible, but we do things that black holes do give off a little bit of radiation in some cases, and that black holes create an environment that gives off a lot of radiation a lot of light. So if you move away from just like the classical general relativity pure black sphere and talk about like the quantum version of it, or if you talk about the stuff around the black hole and the environment created by the black hole, then that could be.
Eclipsed, right, because what stuff falls into the black hole, it tends to get sped up so fast that it actually burns up and then that's bright.
Right, So are things when they come near the black hole. They don't always fall right in. I mean, if your head's straight for the black hole, you're going into the black hole. But if you sort of go near the black hole, then you get bent towards it and you sort of spin around it for a long time before falling in. And so that's called the accretion disc. It's like stuff that's on deck to be sucked into the black hole. And while you're in the accretion disc The black hole is still working you. It's got these tidal forces. It's pulling on the part that's closer to you harder than the part that's further from you, because gravity is stronger for closer things, and so big clouds of gas and dust that are about to fall into the black hole have a lot of internal friction because of the black hole's tidal forces. So they get heated up incredibly hot and emit a lot of radiation, and some stuff almost falls into the black hole, but the strong magnetic fields like guided around the black hole hole and it gets spun out at the top of the black hole, making these enormous jets of radiation. So black holes, even though themselves past the event horizon are black, the stuff around them could actually be very very bright. These things quasars are some of the brightest things in the universe.
Yeah, we've had episodes about that. Now. It's kind of ironic, right, that some of the brightest things in the universe actually come from black holes.
Yeah, because they are the source of a lot of gravitational energy, so they can speed stuff up, they can focus stuff, they can shoot stuff in another direction. Even though you know, if they actually ate that stuff up, you would never see it. But when they're not actually eating stuff, they're also powering the acceleration of other stuff nearby, which creates fantastical light shows, and those light shows can be eclipsed right.
Right, Although, as you said earlier, not every black hole has these light shows, right, Like, there's a whole range of black holes. There are maybe black holes who are sitting all by themselves somewhere with nothing around it to feed it to make it bright. And there are black holes with huge clouds of stuff that is constantly falling into the black hole.
Yeah, there's a broad diversity of black holes. The ones with big accretion discs are the ones that are easier for us to see because you can see the accretion disc right. Otherwise, it's very difficult to spot a black hole. You have to see it passing in front of something else. You have to see it eclipsing something in order to spot it. Mostly the way that we've identified black holes is from their accretion disc or from like the motion of stuff near them, indicating that there must be something very very heavy but not bright there.
Well, I think I see what you're saying. Like, if you define an eclipse as when you're blocking the light that's coming from something else. Then you sort of need the situation where the black hole is giving off light from its accretion disk to have a black hole eclipse.
Yeah. Otherwise you're just having a shadow of a shadow. And I don't even know what that is, but probably exists in the Pokemon universe.
Well, a shadow of a shadow is a double shadow.
It's a shadow squared.
But I guess you could technically block the shadow of a shadow, right, like you could blog looking at a shadow.
Yeah, I suppose. I mean, if you stand in a shadow, do you still have your own shadow? I don't know. That's a philosophical question. That's like the sound of one hand clapping.
Well, I guess you need like a third source of light or something.
Right, right, Yeah, then you get all sorts of complicated shadows.
But you're saying, there's a situation in which a black hole could have an accretion disc around it, which would make it bright, in which case something could float between you and it and block your view of this light source.
Exactly, and that would be a really powerful way to see interesting things really really far away, because black holes are very very bright when we see them. We can see them in very very distant, very ancient galaxies, so the very powerful probe of what's out there in the universe. There's sort of like these pencil rays of light that shine out into the universe. We can use them to measure like the density of stuff along that ray. We once talked about the cosmic web and how we use these pencil rays of light from quasars to like illuminate the universe and tell like where the dark matter is and where these filaments of gas between the galaxies are super interesting. And when something else happens to pass in front of that pencil ray of light in a way that we can see it, then we can use that to identify something. We can use that to see something that otherwise would have been invisible to us. So we can use these eclipses as ways to find stuff really really far away.
Wait, wait do you mean what what does this stuff do well?
For example, the technique we talked about for finding planets around other stars that mostly only works in our galaxy because the stars have to be close enough for us to resolve a single star and measure its brightness very effectively, So it's very difficult to see exoplanets in other galaxies, because remember, our galaxies like one hundred thousand light years across. Other galaxies are like millions of light years away, so we can't really use that technique to find planets around stars in other galaxies. But scientists have recently used this to find planets passing in front of black holes in other galaxies because black holes are such intense sources of this kind of radiation.
Whoa, because they act like a beacon within that other galaxy. But is this a planet that is part of the black hole system or is this like a random planet floating around another start it just happens to one's fly in front of the black hole.
We don't know, and in the case of a recent observation, the theory is that it might be a planet orbiting a black hole with a period of about seventy years, which means that we wouldn't know for another seventy years because we'd have to wait that long to see the next eclipse. If it is in fact orbiting that black hole. If it's just like a random transit, some blob passing in front of the black hole, then it won't happen again. But they actually did see this. They looked out with the Chandra X ray telescope at a galaxy called the Whirlpool galaxy, and they saw this kind of eclipse.
Meaning that we're looking at this galaxy that's far away, and we think that the light coming from it is a black hole.
That's right. We can zoom in on one part of that galaxy, and they think that there's a binary system there. They have like a normal like star and around it is orbiting a black hole, and the black hole's probably from some other star which collapsed and left a black hole. So the origin is probably some binary star system. Two stars orbiting each other, and that's a little bit surprisingly not uncommon, because stars tend to form near each other. One of them becomes a black hole. They have this binary system where the black hole is now like sucking material from the other star and it generates a very bright accretion disc. And so from that black hole you now have this very intense source of radiation, and the telescope consume in on that and see the radiation from the accretion disc of this black hole as it eats its sibling.
Wait, the black hole is orbiting the Sun. I guess it's a smaller mass than the Sun.
Well, they's sort of orbiting each other, right, the two both came from stars, and the black hole doesn't have all the mass of the original star came from. Probably these two stars started out similar mass, and so more accurately you would say they orbit each other.
And then on top of that, they think that maybe there's a planet orbiting around the black hole that's orbiting around.
The Sun exactly, because the black hole is actually quite small, it's very compact, and so when this planet passes in front of the black hole, it actually eclipses a good fraction of it. When we think about a planet transitting in front of a star in our galaxy, it's a tiny little dip in front of that star. But here, because the accretion disk in the black hole are very compact, every compressed by gravity, this planet actually blocked most of the light from this accretion disc as it passed forward. So you can look at like the brightness of this black hole over time, and they see this huge dip as something apparently eclipsed it. It clips the black hole, clips the black hole.
Yeah, but they only saw this once, or have they seen this periodically?
They've only seen it once. They have a model for this system and how far away this planet would have to be and how big it is, and in that model it takes about seventy years to orbit this system. But of course they're not making the grad student wait seventy years to graduate.
Although it could have also been like an asteroid passing in front of the Chandra telescoper, something that could have caused this dip.
Right, Yeah, there's a lot of possibilities. We don't see this thing very directly. We only just see a dip in this black hole, which we otherwise can't explain, which I mean something probably passed in front of it to block our view. And one hypothesis is a planet, but we can't tell very precisely.
Right, it could have been somebody's thumb.
Maybe did you put your thumb on Chindo that day? Or hey, is that what happened?
I don't know. My son doesn't tell me everything it does. That's the whole problem.
But if it's true, then it's really interesting because it's the first time we've discovered a planet in a far away galaxy using this transit technique.
Hmm. Interesting, that's amazing, and it'd be amazing to be on that planet. Can you imagine living on that planet and having like not just the sun, but a black hole also kind of like sunrising and sunsetting every day.
And seeing the black hole eat your sun. Right, That sun gets dimmer and dimmer every year as the black hole pulls the material out of it.
Wow, that'd be a pretty amazing view when you look up from that planet. I wonder if that's where pokemon are.
From, that's where they get their Z power.
Yeah, from the view, it's so amazing. All right, Well, we've seen a black hole get eclipse, and there are other examples of that, and there's also the reverse situation of whether or not a black hole can eclipse something else. So let's get into those. But first, let's take another quick break.
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Hi, I'm David Eagleman from the podcast Inner Cosmos, which recently hit the number one science podcast in America.
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Series of episodes this season to understand why and how our lives look the way they do. Why does your memory drift so much? Why is it so hard to keep a secret? When should you not trust your intuition? Why do brains so easily fall for magic tricks? And why do they love conspiracy theories? I'm hitting these questions and hundreds more because the more we know about what's running under the hood, better we can steer our lives.
Join me weekly to explore the relationship.
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All right, we're talking about black hole eclipses, whether or not you can eclipse a black hole or whether a black hole can eclipse something else. And it turns out that yes, you can eclipse a black hole. We've seen it. We have data from a black hole being eclipse out there in another galaxy.
That's right. Even though black holes are super powerful in the real world and in Pokemon, you can just stand in front of them and block their light.
Yeah, it's pretty amazing. We have data from that. And you said, there's another example of a black hole eclipse that we've seen.
That's right. There's a really cool galaxy about sixty million light years away. It goes by the exciting name of NNGC thirteen sixty five, and it's exciting because it has a very active galactic nucleus. This is what astronomers say when they mean that there's a big black hole at the heart of it, and it's very powerful and it's shooting a lot of stuff out. So if you imagine a galaxy is like a big flat disk of stuff, maybe with arms trailing behind it. Now add to that huge jets of stuff shooting up and down sort of from the middle of that disk. So the galaxy is no longer just like flat. It now has like an axle around which it's spinning.
And so we've seen this galaxy and has something eclipses.
Yeah, astronomers were really curious about what was going on at the heart of that galaxy, and they wanted to know how big was the black hole, and how big was the active part of it, this sort of like really intense part of the center of the galaxy. How big is that accretion disc. Problem is that the galaxy is so far away that it's really hard to measure that. Like we've taken pictures of black holes and their accretion discs, but it's very, very difficult, and for this galaxy, it's too far away for us to even use the event horizon telescope. So they were trying to figure out how big this thing was, and then they got lucky. They got lucky because a big cloud of gas, when they already knew and had studied before, passed in front of the black hole and eclipsed it. Because they knew how big this cloud was and how fast it was going, they were able to use that to measure the size of the black hole accretion disc itself.
Wait, what so there was a black hole in another galaxy farwaing, and a gas cloud within that galaxy passed in front of it, or between us and that other galaxy.
The gas cloud is part of that other galaxy.
You know, Oh, I see, And how do we know how big that gas cloud was? Because it's so far away.
It's so far away, but it's really big. And so they were able to measure the size of this gas cloud. It's much bigger than the black hole.
But it's big enough to see with the telescope.
It's big enough to see. Yeah, we can see other galaxies and we can see individual components of it. We can't always resolve things as small as stars, but big gas clouds we can resolve.
And so the cloud eclipse the black hole in the middle or the quasar in the middle, like it blocked it completely or just made it kind of fuzzy for a while.
It blocked it almost completely. I mean, some light can get through it at some wavelengths, but you can see definitely the dramatic dimming of this black hole because this cloud passes in front of the accretion disc, and so as it passes in front of one side of the accretion disk, it starts to dim, and then if it's totally blocking the disk, then you get the minimum brightness. And then as it starts to reveal the accretion disc again, the light comes back up. And so from the size of the gas cloud and the speed the gas cloud was moving, you can figure out the size of the accretion disc, which is what the astronomers are really curious to know.
Interesting, so these are recorded instances of black hole eclipses, like you could be the astronomer that saw a black hole eclip.
Yeah, exactly. And these are lucky coincidences, right, just like the Sun and the Moon lining up. In the case that these things line up in the sky, we can use that to learn something about these systems. We're always taking advantage of what's going on in the universe. Astronomers never get to like build experiments and say what happens if I crash these two things together, or if I pass this in front of the other thing. They have to just be clever in other ways of saying, well, I didn't get to design this situation, but what can I do to learn about the universe from it? Anyway? And so I love seeing astronomers be clever this way and figure out, like how to use the lucky lining up of these two objects to learn something about them.
And in this case, they used the gas cloud to learn about the size of this black hole. What did they learn about it?
So they learned the size not just to the black hole, but also the disc around it, right, because it's the disc around it, the accretion disc that really is generating that radiation. So they learn that this disc is about seven au wide, where Au is the distance from the Earth to the Sun. And so if you put this thing in our solar system and to extend out past the Earth's orbit and out past Mars, so this thing is really pretty big.
Wait, we can measure the size of the cloud before, but we couldn't measure the size of the black hole.
Yeah, and the cloud is bigger than the black hole, so we were able to resolve it all right.
Well, the final question is whether a black hole could eclipse something else, like if there's a star or a sun out there, and a black hole passes in between it and us, would it create an eclipse? That would be pretty dramatic, wouldn't it. That would be pretty dramatic, But it's almost impossible. If somebody's standing on the other side of a black hole and like turning on and off a flashlight, then a lot of those photons would get to you anyway. Remember that space around the black hole is really really curved, so light doesn't always travel in straight lines. So light that comes out from their flashlight that wouldn't otherwise get to your eye gets bent by the black hole towards your eye. So the black hole would eat some of the photons from the flashlight, but other photons that were going in other directions would get bent towards your eyeball, so you would.
Still see it.
Right, Like if a black hole just happened to fly into our solar system and get between us and the Sun, it wouldn't totally block the Sun. It would only block some of it.
Yeah, Like, if somebody stood on the other side of a black hole with a laser of single photons, they could shoot them at the black hole and you would eat them and you wouldn't see it. But if their source has any sort of width to it. If the photons come out at any sort of angle, then some of those are going to get bent around the black hole and towards your eye. We see the same thing happening actually already with the moon. This is Einstein's famous proof of general relativity that space is curved by mass, because he showed that photons from the Sun don't always get blocked by the Moon. The moon bends them around itself a tiny little bit. The Moon is lensing the light from the Sun a little bit, and a black hole would be a very very powerful gravitational lens. So it's almost impossible to hide behind a black hole, right.
You're saying, like, because the Moon is almost the same size as the Sun in the sky, it doesn't totally block the Sun because some of the light kind of flows around the Moon and gets to us anyway. But if the Moon was bigger right in the sky, might like ten times bigger than the Sun, it would almost totally block the Sun.
Right, Yeah, exactly, Although if the Moon was more massive then it would be more effective at bending some of the Sun's light towards us. And so there's two different effects going on there, And So if something is very small, like a black hole and very very dense, it's going to be excellent at gathering light that otherwise wouldn't have gone to you and sending it your direction.
So what would we see if a black hole stood between us and our sun? We would see like a black circle with a bright ring around it, right, and then that ring would sort of merge with the Sun and kind of distor the light around it, and then they would block the Sun and then it would keep going.
Yeah, exactly. It would look really weird and awesome. It reminds me actually of a great science fiction book I read, Perihelion by Greg Egan, where he talks about what happens when a black hole enters our solar system, and it's not something you should look forward to because it would just everything in the solar system, even before it made an impressive distortion of the Sun's light.
It'd be bad news. But let's say it was a really big black hole. It would totally eclipse our sun, right or we still see all of the light from the Sun. We wouldn't, right, We would only see some of the light from the Sun get bent around the black hole, but mostly it would be blocked.
We wouldn't see all of the light from the sun because photons shot directly towards the center of the black hole would still fall into the black hole, but photons shot in other directions would get bent around it.
To us, well, there would be a range, right, wouldn't there be a range, Like, it's not just the ones directly to the center of the black hole, so the ones a little bit off to the side also get sucked into the black hole.
Yeah. The bigger the black hole, or the closer you are to it, the sort of the wider range of photons that do fall into the black hole, but also the more powerful the black hole, the more it's able to bend other photons around it so that you can see it.
And have we seen an example of this, I guess we kind of have, right, I mean, we've taken pictures of black hole holes. Right, we have pictures of black holes, and presumably there are stars behind that black hole that we're not seeing because they're getting blocked by this black hole.
I don't know that we've seen that directly. We've discovered smaller black holes because of their gravitational effects on like nearby stars. Like if you see a star and it's moving in such a way that you can tell it's orbiting something, but you don't see the thing there, then you deduce that there's probably a black hole there, even if you don't see it. I don't know if we've seen direct lensing of background stuff from a stellar mass black hole.
Well, I guess if we have a picture of a black hole, technically it was blocking something behind it.
Right, Yeah, assuming there was something behind it, then yeah, it's getting blocked.
Yeah, well technically or that has to be something behind it, doesn't there. I mean, it's not like there, it's totally empty space behind.
It, right, Yeah, there's always background galaxies no matter how far you look.
All right, Well, I think your point is that it's complicated, right, because black holes bend space so much that it and they act like lenses out there in space that it's it's kind of a complicated situation to have a black hole block something else.
Yeah, black holes are great at bending light and eating photons, but they're also great at showing you what's behind them.
Yeah, but definitely, for sure we're seeing things block black holes from our view. It's just that the situation is more complicated for a black hole blocking RV of something else.
Yeah, exactly.
All right, Well, I think the main lesson is Pokemon was right. I think that's what you're saying.
Right, that's right. You don't need a physics degree. Just invest your college savings in Pokemon.
That's right. Just catch them all and you can retire to that tropical island or at least pay for your son's college. It kind of caused the same these days, it.
Does cost the same. Maybe you'll get a PhD in Pokemon.
I think there are probably are people getting their PhDs on the cultural impact of Pokemon. I'm sure you can get a PhD on anything.
Exactly. Everybody can get a PhD.
All right, Well, I guess the next time you look out into the night sky or even the daytime sky, imagine that there are black holes out there being eclipse and also eclipsing our view of the universe, because the universe is full of all these amazing objects.
And be impressed by how astronomers are taking advantage of coincidences and happenstance out there in the universe to teach us lessons to reveal the nature of the mysteries of our cosmos.
That's right. The main lesson here is don't put your thumb down on physics. Give it those thumbs up.
Yeah, two thumbs up to astronomy.
All right. We hope you enjoyed that. Thanks for joining us, See you next time.
Thanks for listening, and remember that Daniel and Jorge Explain the Universe is a production of iHeart Radio. For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows. When you pop a piece of cheese into your mouth, you're probably not thinking about the environmental impact. But the people in the dairy industry are. That's why there were working hard every day to find new ways to reduce waste, conserve natural resources, and drive down greenhouse gas emissions. House US dairy tackling greenhouse gases. Many farms use anaerobic digestors to turn the methane from maneure into renewable energy that can power farms, towns, and electric cars. Visit you as dairy dot COM's Last Sustainability to learn more.
Hi.
I'm David Eagleman from the podcast Inner Cosmos, which recently hit the number one science podcast in America. I'm a neuroscientists at Stanford, and I've spent my career exploring the three pound universe in our heads.
Join me weekly to explore the relationship between your brain and your life.
Because the more we know about what's running under the hood, bet or we can steer our lives. Listen to Inner Cosmos with Savid Eagleman on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts.
Parents looking for a screen free, fun and engaging way to teach your kids the Bible. As a mom, I was looking for the same thing, so I created Kids' Bible Stories podcast. Thousands of families are raving about it, and kids actually request to listen. With captivating sound effects, voices, and an apply section at the end to spark meaningful conversations, it's a hit with both kids and parents. Listen to Kids Bible Story's podcast on the iHeartRadio app, Apple podcasts, or wherever you get your podcasts.
