Speaker 1: Hey, Daniel, how do you like your coffee in my mouth?
Speaker 1: I guess usually or maybe sometimes in ice cream. I mean, like,
Speaker 1: do you like to drink the tiny, strong Italian coffees
Speaker 1: or the big week American style coffees? Hmmm, I guess
Speaker 1: I like the sort of medium sized coffee, you know,
Speaker 1: strong enough to be for grown ups, but not like
Speaker 1: a punge in the face. I see. And does that
Speaker 1: apply to particles too? Do you prefer tiny particles or
Speaker 1: massive ones? I don't know. I like them heavy enough
Speaker 1: to be rare and worthy of winning a Nobel Prize,
Speaker 1: but light enough that we can discover them at Collider's.
Speaker 1: And you're so middle of the road. Sometimes the middle
Speaker 1: of the road is exactly where the mysteries lie. Hi
Speaker 1: am Jorge, handmade cartoonists and the creator of PhD comics. Hi.
Speaker 1: I'm Daniel. I'm a particle physicist, and I usually eat
Speaker 1: a medium size portion of cookies for breakfast, for lunch,
Speaker 1: or all of the above. Every time you start eating cookies,
Speaker 1: you can't just have one. You try to avoid having
Speaker 1: the whole box, so I end up somewhere in the middle,
Speaker 1: somewhere like half of a box of cookies. Depends are
Speaker 1: you're doing arithmetic half or geometric half, you know, it
Speaker 1: depends on the day. Then you can do zenos paradox
Speaker 1: that can eat half the box, and then you eat
Speaker 1: the other half, and then the half the remaining half,
Speaker 1: and pretty you ate everything but a crumb. Yeah, well,
Speaker 1: that's a great way to avoid eating the whole box, right,
Speaker 1: Wisdom from the ancient Greeks. It's the Greek diet, it's
Speaker 1: the new Mediterranean diet. Only eat half of the remaining
Speaker 1: box of cookies. But welcome to a podcast. Daniel and
Speaker 1: Jorge Explained the Universe, a production of I Heart Radio,
Speaker 1: in which we take a bite of the entire box
Speaker 1: of universe cookies. We chew on the bits to talk
Speaker 1: about black holes, We think about all the little chocolate
Speaker 1: chips that are particles. We dig down into the crumbs
Speaker 1: and try to understand everything that's going out there in space,
Speaker 1: in the universe, in history, and in the future. We
Speaker 1: very humbly try to explain the entire universe to you.
Speaker 1: That's right. There are amazing mysteries all over the universe,
Speaker 1: and those mysteries range from gigantic size galaxy cluster billions
Speaker 1: of light years wide mysteries and really really tiny mysteries
Speaker 1: in the particles and the little quarks and tiny quantum
Speaker 1: fluctuations that make up who we are. Are you saying
Speaker 1: I'm just a quantum fluctuation that I could just disappear tomorrow.
Speaker 1: Well we can all disappear tomorrow, Daniel, depends on what
Speaker 1: you guys are working on at the large handring collider there. Well,
Speaker 1: if we make a black hole, will make a little
Speaker 1: itty bitty when I promise good, I'm glady that's an option.
Speaker 1: I'm so glad you're not tempted at all to just
Speaker 1: dial it up. We'll have a knob here in front
Speaker 1: of me, you know, So tell me what what size
Speaker 1: black hole should we be making here the late see?
Speaker 1: How about a zero sized black hole? That's no fun?
Speaker 1: And how are we going to learn the secrets of
Speaker 1: the universe? Keep you inside the tiny black holes? I'm
Speaker 1: okay where they are right now. But black holes are amazing.
Speaker 1: They are fascinating. They do contain amazing secrets of the
Speaker 1: universe inside them. But there are also really fascinating questions
Speaker 1: about how they get made and why they are the
Speaker 1: size they are or the size they aren't. Yeah, they
Speaker 1: seem to be everyone's favorite space mystery. Do you think
Speaker 1: maybe it was all in the name, Like if you
Speaker 1: had called them, I don't know, vacuum holes or gravity pits,
Speaker 1: do you think people would still be as interested in
Speaker 1: the I think they would. I think it's their fundamentally
Speaker 1: alien nature that makes themselves fascinating. We know they are
Speaker 1: really deeply, weirdly different from anything we have seen before,
Speaker 1: and I think that's what sparks our curiosity. You know,
Speaker 1: we want to go there and see it and explore
Speaker 1: it because we want to understand what's possible in the universe.
Speaker 1: As we say often on the podcast, it's the extreme
Speaker 1: situations that teach us what the rules really are because
Speaker 1: they show us the limits. Yeah, and as you say that,
Speaker 1: you can find them in all kinds of sizes out
Speaker 1: there in space. There are black holes that are humongous
Speaker 1: and warm the center of galaxies and help keep galaxies
Speaker 1: kind of together, and you can make them tiny little
Speaker 1: ones that evaporate right away. Yeah, that's right. There are
Speaker 1: these funny, two different populations of black holes, the ones
Speaker 1: that seem to come from the collapse of stars and
Speaker 1: the huge galaxy gobblers at the center of many galaxies,
Speaker 1: and the weak thing is that there don't seem to
Speaker 1: be any in between. Really, there's no like Goldilocks black holes.
Speaker 1: There's only two options, like VENTI and X are large.
Speaker 1: That's right. You either don't open the box of cookies
Speaker 1: or you eat the whole thing. The universe never goes
Speaker 1: for half a box. Yeah, so there are mostly two
Speaker 1: sizes of black holes in the universe. One you're saying
Speaker 1: it are the ones that come from the collapse of stars.
Speaker 1: Those are I mean, they're pretty big. There's still like
Speaker 1: the size of you know, many suns. Yes, these are small,
Speaker 1: only on the sort of like cosmic galactic scale, right,
Speaker 1: smaller than a whole galaxy. Still a normal is still
Speaker 1: more massive than our entire solar system. But yeah, tiny
Speaker 1: compared to other things. And then you have the huge ones,
Speaker 1: the ones that are how many, like millions of times
Speaker 1: the mass of the Sun up to millions or even
Speaker 1: billions of solar masses, so many stars compacted into a
Speaker 1: tiny little space at the center of some of these
Speaker 1: galaxies really just mind bogglingly massive and incredibly powerful objects. Yeah,
Speaker 1: and so black holes can be any size really in between,
Speaker 1: and you know, from tiny, two huge, But apparently you
Speaker 1: don't see a lot of ones in the middle out
Speaker 1: there in the cosmos. Most of the ones that you
Speaker 1: see out there are either kind of supernova size or
Speaker 1: gigantic galaxy center size. Yeah, it's even more dramatic than that.
Speaker 1: We have never seen any in between. There's not an example,
Speaker 1: a single example of a black hole in between those two.
Speaker 1: So we don't actually know if it's possible to have
Speaker 1: an intermediate size black hole. Maybe the laws of physics
Speaker 1: just don't allow it. So that's the question will be
Speaker 1: tackling today. So to be on the program, we'll be
Speaker 1: asking the question where are all the intermediate mass black holes?
Speaker 1: You've gotta made it easier for me, Daniel, and just
Speaker 1: medium mass. Well, that was going to be my next
Speaker 1: question is what would you have called these things? Because
Speaker 1: intermediate size black holes or intermediate mass black holes is
Speaker 1: quite a mouthful. Yeah, I don't know, just go with
Speaker 1: like the Starbucks rude and call them large black holes,
Speaker 1: which are really the medium sized black holes. That's true,
Speaker 1: but everything in the universe is enormous, right, so maybe
Speaker 1: the Starbucks naming scheme makes sense. Yeah, large, extra large,
Speaker 1: super large, and galectically large, cosmic large. That's right. It's
Speaker 1: like ordering fries and McDonald's there are no more small fries,
Speaker 1: Is that true? I think so. I think you can
Speaker 1: only order large or extra large. I will admit not
Speaker 1: having been to McDonald since I worked there when I
Speaker 1: was six. And yeah, you seem to know a lot
Speaker 1: about their menu, Danniel. I'm a member of society. I
Speaker 1: participate in society. I read memes on the internet to
Speaker 1: educate me about humanity. You turn your your nose up
Speaker 1: at fast food change, sure, like everyone else in society.
Speaker 1: But yeah, maybe I would call medium sized black holes.
Speaker 1: You know that kind of makes sense. Yeah, you know,
Speaker 1: as a middle child, I'm sort of sensitive to this naming.
Speaker 1: You know, middle seems to like be defined by the others.
Speaker 1: There's nothing like unique and identifying about being in the middle.
Speaker 1: You're like defining yourself by what you're not instead of
Speaker 1: by what you are. We just opened up a whole
Speaker 1: black hole of psychological trauma. There issues there and Daniel,
Speaker 1: your middle children out there. You know you know that well,
Speaker 1: you have like ninety seven brothers and sisters, right, so
Speaker 1: you you've got to understand and is this why you
Speaker 1: started a podcast just to err on your sibling rivalry issues. Yes,
Speaker 1: it's been a three hundred episode plan to get to
Speaker 1: this moment exactly. All right, tell me, Daniel, tell me
Speaker 1: about your childhood. I feel defined by my more massive
Speaker 1: and less massive brothers. I see now you're making swipes
Speaker 1: at their body weight there, man, I meant intellectual gravitas,
Speaker 1: of course, yes, of course, of course, but yeah, I'll
Speaker 1: rate that. Are talking about black holes, Daniel, and how
Speaker 1: there aren't any real middle of the ones out there
Speaker 1: in space. You mostly see big ones or smaller ones
Speaker 1: the size of a few sons, And so that's the question,
Speaker 1: where are all the intermediate mass black holes? So it's
Speaker 1: usually we were wondering how many people out there knew
Speaker 1: that these black holes are are missing from the universe
Speaker 1: and where they could be. So thanks to everybody who
Speaker 1: volunteered to answer my random questions with no preparation or
Speaker 1: reference materials. If you'd like to participate in future episodes,
Speaker 1: please write to me two questions at Daniel and Jorge
Speaker 1: dot com. We love your contributions and I promise you
Speaker 1: it's fun. So think about it for a second. Where
Speaker 1: do you think all the medium or intermediate mass black
Speaker 1: holes in the universe are. Here's what people had to say.
Speaker 1: That's a good question. I think that there's no proof
Speaker 1: that they even exist, but that they do. Maybe they
Speaker 1: are lurking somewhere in the intergalactic space where there's just
Speaker 1: no stuff for them to eat and growth. They don't
Speaker 1: don't form those Christian disks, And basically the only way
Speaker 1: that we can spot a black hole is by looking
Speaker 1: at the Christian disk and figuring out indirectly that there
Speaker 1: must be a black hole in the middle of it.
Speaker 1: But if there is no a Christian disk, that we
Speaker 1: may have a black hole that is somewhere out there,
Speaker 1: but we just have no chance of ever spotting it.
Speaker 1: So I would bet for intergalactic space. I know at
Speaker 1: the center of a galaxy you get really big black holes.
Speaker 1: I think they're called supermassive black holes. So they won't
Speaker 1: be there, but maybe be an intergalactic space. But I'm
Speaker 1: not sure. All right, not a lot of clarity here
Speaker 1: from our listeners. I like the idea that maybe they're
Speaker 1: floating out there in space and we just can't see them.
Speaker 1: This one president said, made they're lurking in intergalactic space. Yeah,
Speaker 1: it's a cool idea. If you're a black hole, can
Speaker 1: you do anything else in space except lurk? Oh? Come on,
Speaker 1: you could be very dramatic. You could swoop into us
Speaker 1: always system and gobble it up and destroy everything. Right,
Speaker 1: that's the opposite of lurking. That's like leaping. Yeah, but
Speaker 1: then afterwards you go back to lurking. Well, I like
Speaker 1: this idea because it suggests that you know, there are
Speaker 1: things out there and intergalactic space that we don't know
Speaker 1: about that we can't see. That it might surprise us
Speaker 1: that basically you could hide anything out there as long
Speaker 1: as it's dark enough. And you know, that's a reasonable point.
Speaker 1: And I guess the real mysteries that you know there
Speaker 1: there could be intermediate mass black holes out there, Like,
Speaker 1: there's nothing that we know about so far that would
Speaker 1: would prevent them. Theoretically they're possible, but you just don't
Speaker 1: see them. Yeah. Well, that's the problem with black holes
Speaker 1: is that you can't see them directly, right because they
Speaker 1: are black. All you can do is see their effect
Speaker 1: on stuff behind them or around them. And so if
Speaker 1: you had a black hole deep in the middle of
Speaker 1: space with nothing around it, how would you detect it, it
Speaker 1: it would be undetectable, it would be very effectively lurking.
Speaker 1: And so this is actually a good point. The question
Speaker 1: that needs to know how did it get made? How
Speaker 1: did you form a black hole out there in the
Speaker 1: middle of space with nothing around you. Usually black holes
Speaker 1: are made from stuff, and then there's other stuff around
Speaker 1: that didn't get black holeified, and you can use that
Speaker 1: to detect it. That's the mystery. And so I guess maybe, Daniel,
Speaker 1: let's start at the beginning and let's talk about how
Speaker 1: you would even define an intermediate black hole, like, what
Speaker 1: is there a technical range of masses that we qualify
Speaker 1: as intermediate Yeah, there actually is. Unfortunately for the psychology
Speaker 1: of intermediate mass black holes, they are defined by what
Speaker 1: they are, not they're defined by their bigger and larger siblings. Right,
Speaker 1: So it's a black hole that's between a solar mass
Speaker 1: black hole like one that comes from a collapsed star,
Speaker 1: and we can talk about it, but there's definitely an
Speaker 1: upper limit on how big that can be, because there's
Speaker 1: an upper limit of how big a star can be.
Speaker 1: So it has to be bigger than the black hole
Speaker 1: that could come from a star, but then smaller than
Speaker 1: black holes we see the center of galaxies, which is
Speaker 1: about ten thousand or fifty thousand times the mass of
Speaker 1: the Sun. So there's a huge range there between a
Speaker 1: hundred and like ten thousand solar masses. We call the
Speaker 1: intermedi a mass range for black holes. Oh, I see
Speaker 1: there's a limit due to the sizes of stars. Exactly
Speaker 1: what kind of black hole do you imagine when you
Speaker 1: think about black holes? Probably are the ones that come
Speaker 1: from when a star collapses, Right, you know that stars
Speaker 1: are formed from gases that are collected by gravity, and
Speaker 1: then you get fusion burning, which prevents further collapse. Right,
Speaker 1: gravity would just go directly to a black hole if
Speaker 1: the star didn't ignite fusion inside of it, which was
Speaker 1: pushing out with radiation to prevent the collapse. That happens
Speaker 1: for you know, several billion years or so until the
Speaker 1: fuel runs out and turns into heavy ash, which accelerates
Speaker 1: the gravitational collapse instead of preventing it, and then the
Speaker 1: whole thing collapses into a black hole. But there's a range.
Speaker 1: They're like, it can't collapse into a black hole if
Speaker 1: it doesn't have enough mass. So the lower limit on
Speaker 1: a black hole that comes from the Sun is like
Speaker 1: ten solar masses. Smaller than that, and it collapses into
Speaker 1: like a neutron star or something else because it can
Speaker 1: still resist the gravitational pressure. But what about larger than that, Like,
Speaker 1: can bigger star collapse into a bigger black hole? It can,
Speaker 1: but you can only get up to about eighty or
Speaker 1: ninety times the mass of the Sun. And the reason
Speaker 1: is that you can't have a star that's much bigger
Speaker 1: than about three hundred times the mass of the Sun.
Speaker 1: You try to make a star bigger than that, Remember
Speaker 1: we talked about this on an episode about the biggest
Speaker 1: stars in the universe. Then those stars aren't stable. They
Speaker 1: blow themselves apart because as the star gets bigger and
Speaker 1: the inside of it gets higher pressure, and that higher
Speaker 1: pressure means the fusion burns hotter, and so it produces
Speaker 1: more radiation. It's very nonlinear, and so a little bit
Speaker 1: more stuff means a much higher temperature inside, which means
Speaker 1: radiation blowing out. So then the star literally tears itself apart.
Speaker 1: So the biggest star you can have is about three
Speaker 1: hundred times the mass of our Sun, which means that
Speaker 1: there's a limit on how big a black hole you
Speaker 1: can get that comes from a star, I see, But
Speaker 1: the limit is smaller than the biggest star. So the
Speaker 1: biggest stars can be three hundred times the mass of
Speaker 1: our sign, but the ones that turn into black holes
Speaker 1: are only the ones that go up to about eighty
Speaker 1: times the mass of our Sun. No, no, it's because
Speaker 1: not all the stuff in the star ends up in
Speaker 1: the black hole, right it's tearing itself apart, and not
Speaker 1: all of it collapses in the black hole. You still
Speaker 1: get a huge amount of stuff outside the black hole
Speaker 1: that it's blown out. You know. Sometimes you get like
Speaker 1: a supernova before you get a black hole, and that
Speaker 1: shoots a huge amount of energy and mass out into
Speaker 1: the universe. So the process to go from star to
Speaker 1: black holes not ad efficient, which is why three hundred
Speaker 1: solar mass stars turned into about eighty or ninety solar
Speaker 1: mass black holes. You're talking about the kind of the
Speaker 1: limit of the size of the black hole that can
Speaker 1: come from a star. But the stars usually started off
Speaker 1: with three hundred times the mass of the Sun, and
Speaker 1: then they collapse into eight times the mass of the Sun,
Speaker 1: and those are very rare. Like stars that massive are
Speaker 1: very very rare because they're very unstable and short lived.
Speaker 1: Most stars are much much smaller than that. So most
Speaker 1: of the stellar black holes you see out there are
Speaker 1: in the lower end of the ten to eighty range.
Speaker 1: Eight is like really extreme and crazy and rare. So
Speaker 1: then that's like one kind of limit, like the biggest
Speaker 1: stars kind of defines what the biggest black holes that
Speaker 1: can come from the Sun with their masses exactly nicee.
Speaker 1: And we see a lot of those out in the space, right. Yeah,
Speaker 1: those are all over the galaxy. Every time you have
Speaker 1: a star that's that big, its path will lead it
Speaker 1: to become a black hole, And so those black holes
Speaker 1: are appearing all the time. They're not rare, they're not weird,
Speaker 1: that not unusual, and we see lots of those black
Speaker 1: holes around the universe. That's the kind of lower range
Speaker 1: of black holes, and then there's like the upper range
Speaker 1: of black holes. Yeah, the black holes that we see
Speaker 1: at the centers of galaxies are like completely different beasts.
Speaker 1: I mean, they are similar from the general relativity point
Speaker 1: of view in that they are very compact objects that
Speaker 1: are very dense that have incredible gravity, but they seem
Speaker 1: like monsters compared to these stellar black holes because they
Speaker 1: tend to have masses like a million or a billion
Speaker 1: times the mass of one son, and so these are
Speaker 1: just really enormous and they really like drive the gravity
Speaker 1: of a galaxy. They sit at the center of the
Speaker 1: galaxy and they are you know, like one one hundreds
Speaker 1: of the mass of the whole galaxy is in that
Speaker 1: single black hole and it's pulling on the whole galaxy
Speaker 1: and it's slurping everything around and it's gobbling stars at
Speaker 1: the middle. We have one like this at the center
Speaker 1: of our galaxy. They're pretty common, I guess, Like I
Speaker 1: think most galaxies have a supermassive black hole at its center.
Speaker 1: Like when you look out into space and you see,
Speaker 1: you know, millions and millions of galaxies, most of them
Speaker 1: have one of these giant black holes in the middle.
Speaker 1: We don't actually know the fraction of these galaxies that
Speaker 1: have one, And that's one of these questions, Like we
Speaker 1: know that black holes in the center of galaxies tend
Speaker 1: to be proportional to the mass of the galaxy. So
Speaker 1: bigger galaxy, bigger black hole the center. Smaller galaxy, smaller
Speaker 1: black hole the center. We don't know if they all
Speaker 1: have black holes, like we've seen a lot without them.
Speaker 1: We don't know the fraction of galaxies that have black holes, actually,
Speaker 1: but it's not rare. I guess that's what I mean.
Speaker 1: You see them often. Yeah, it's not uncommon. Absolutely, They
Speaker 1: kind of all over the place, yes, And so what's
Speaker 1: the range of size as we've seen for those? So
Speaker 1: up to billion, right, like ten billion solar masses is
Speaker 1: the biggest black hole we've ever seen. And as far
Speaker 1: as we can tell, there's no upper limit to how
Speaker 1: big a black hole can get. Like, you keep feeding
Speaker 1: that thing, it'll just keep getting bigger. The limit really
Speaker 1: is just like cann be around enough stuff and have
Speaker 1: enough time to gobble it. On the lower end of
Speaker 1: super massive black holes, the smallest one we've seen is
Speaker 1: about fifty thousand times the mass of the Sun. This
Speaker 1: is in a little mini galaxy we call these dwarf galaxies,
Speaker 1: about three hundred forty million light years from here. The
Speaker 1: galaxy is called r g G one eighteen. And that's
Speaker 1: the smallest black hole we've ever seen inside a galaxy.
Speaker 1: It's fifty thousand times the mass of the Sun. That's huge.
Speaker 1: Imagine fifty of our sons, Yeah, and then collapsing into
Speaker 1: a black hole like the gravity of fifty thousand suns
Speaker 1: is nothing to be sneezed at, or if you sneezed
Speaker 1: at it, your sneeze will get sucked up by that
Speaker 1: black hole right away. This is not we just gets
Speaker 1: slurped out of your nose. Probably we should call that
Speaker 1: black hole is in tight Hey, yeah, then will be
Speaker 1: a green black hole depending on the size of years
Speaker 1: these we'll see. All right, Well, it seems like there
Speaker 1: are these huge populations of black holes out there, kind
Speaker 1: of the the star sized ones and the gassy size ones,
Speaker 1: but maybe not so many in the middle. So let's
Speaker 1: get into whether or not they actually exist or whether
Speaker 1: or not we're just not seeing them. But first let's
Speaker 1: take a quick break. All right, Daniel, we're talking about
Speaker 1: intermediate mass black holes. Now. Is that the official names
Speaker 1: are an acronym for that, That is the official name.
Speaker 1: You'll see that in the literature if you search for them.
Speaker 1: And you know, I call them I m b H.
Speaker 1: But it sort of reminds me of I MDB, so
Speaker 1: I think maybe we need a better name for them.
Speaker 1: M I see. Well, they do sort of collect stars
Speaker 1: in a way, right, I'm sure there are films of
Speaker 1: gas clouds I'm really stretching in here. Yeah, well, we
Speaker 1: should go look this up on the Internet movie black
Speaker 1: Hole Database. I'm sure there is one, isn't There are
Speaker 1: dots and physicists kind of keep track of everything and
Speaker 1: polish it online. I don't know, but after this episode,
Speaker 1: I'm gonna go type in i mbhdb dot com and
Speaker 1: see if somebody owns that already. Oh man, maybe you
Speaker 1: should have checked that before sponsoring it on the podcast.
Speaker 1: Some family with kids are gonna look that up and
Speaker 1: then they're gonna be like what. Alright, we're talking about
Speaker 1: whether or not intermediate mass black holes exist because we
Speaker 1: don't really see them out there in space. We see
Speaker 1: the kind that are about the size of suns, a
Speaker 1: few hundred suns that came from suns. And we talked
Speaker 1: about black holes that are at the center of galaxies,
Speaker 1: which are huge tens of thousands or maybe millions or
Speaker 1: billions of times the mass of our sun out there
Speaker 1: in the middle of galaxies. But you don't see a
Speaker 1: lot of black holes in between out there. Yeah, there
Speaker 1: seems to be this weird gap there, and it makes
Speaker 1: us wonder, like, are there those black holes out there?
Speaker 1: But we just can't see them yet, or is there
Speaker 1: some reason why they don't even exist, like they're unstable,
Speaker 1: or they accelerate really quickly to becoming supermassive, or they
Speaker 1: fall apart in some way. Like anytime there's a puzzle
Speaker 1: like that, something we don't understand, where we see something
Speaker 1: we don't expect, or we don't see something we do expect,
Speaker 1: that's a clue. That's an opportunity to figure out something.
Speaker 1: It's a moment where we can learn something about the
Speaker 1: universe because we're ready to be surprised by the data. Right. Yeah,
Speaker 1: it would be like, you know, having a population of
Speaker 1: people and then seeing only two sizes of people, like
Speaker 1: not seeing you know, sort of a continuum and like
Speaker 1: a smooth range of sizes of people. Yeah, and it
Speaker 1: would make you wonder like how did all those tall
Speaker 1: people get so tall? At some point they must have
Speaker 1: been medium height, right, so where are all the future
Speaker 1: tall people? Why are there no medium height people who
Speaker 1: are growing into those tall people. That's basically the question
Speaker 1: we're asking about these intermediate mass black holes. I mean,
Speaker 1: for example, you wonder about these supermassive black holes. How
Speaker 1: did they get supermassive? They must have started from something.
Speaker 1: If they started from something very small, then you know,
Speaker 1: by simple arguments, they must have at some point been
Speaker 1: in that intermediate range. Right, Well, I guess that's one
Speaker 1: of the mysteries, right, Like, we don't actually know where
Speaker 1: these supermassive ones in the center of galaxies came from
Speaker 1: or how they came to be so large. That's one mystery, right,
Speaker 1: that's exactly the mystery. Like the argument had just made
Speaker 1: that supermassive black holes may have started from small things
Speaker 1: and then grown to supermassive, we don't actually know if
Speaker 1: that's true, and we see things about supermassive black holes
Speaker 1: that we can't explain using that idea. For example, we
Speaker 1: look really far into the edge of the universe to
Speaker 1: see old old galaxies, to see galaxies when they were
Speaker 1: very very young, right like just a billion years after
Speaker 1: the beginning of the universe, there were already galaxies, and
Speaker 1: in those galaxies we already see super massive black holes,
Speaker 1: like black holes that have two billion solar masses. So like,
Speaker 1: only a billion years have passed and already you've made
Speaker 1: stars and galaxies and supermassive black holes inside them. We
Speaker 1: don't know how it's possible to go from nothing to
Speaker 1: supermassive black hole in just a billion years. So it's
Speaker 1: a mystery. How did those black holes get started. We
Speaker 1: don't know. I see a billion years from the Big Bang,
Speaker 1: you're saying, we already had black holes that are billions
Speaker 1: of times the massive US Sun. Yeah, exactly, And we
Speaker 1: can see them because those super massive black holes have
Speaker 1: really big accretion disks around them, like this disc of
Speaker 1: gas and dust and other stuff that's getting swirled in
Speaker 1: it gets really hot and it glows. It sends off
Speaker 1: a huge amount of radiation. Those are called quasars. So
Speaker 1: we see these quasars in the very very distant universe
Speaker 1: from the very early universe, and if you model the
Speaker 1: formation of galaxies, it's really hard to get a black
Speaker 1: hole that big that fast. We talked about this in
Speaker 1: our episode about supermassive black holes, so you can dig
Speaker 1: into that if you want more details. But very briefly,
Speaker 1: there's sort of like a limit at how fast a
Speaker 1: black hole can grow. It's called Eddington limit. And as
Speaker 1: you pump more stuff near a black hole than actually
Speaker 1: the radiation from the stuff near it pushes stuff away
Speaker 1: from the black hole. So it's hard to feed a
Speaker 1: black back hole fast enough to have a grow to
Speaker 1: be that big that quickly. So it's a mystery. We
Speaker 1: don't know if these black holes actually started from something
Speaker 1: small and then passed through this intermediate mass black hole
Speaker 1: region and then became supermassive black hole, or if they
Speaker 1: somehow skipped it. Could they have just you know, drunken
Speaker 1: a lot of strong coffee or Italian style and black espresso,
Speaker 1: or maybe American style boxes of cookies. You know, there
Speaker 1: are other ideas to explain the supermassive black holes, like,
Speaker 1: for example, maybe there were black holes that begin in
Speaker 1: the very beginning of the universe, before there were even particles,
Speaker 1: before they were stars, before there was even really matter.
Speaker 1: Maybe there were these primordial black holes right because the
Speaker 1: Big Band was pretty crazy, I imagine, or at least
Speaker 1: how the universe was before the Big Bang, and you know,
Speaker 1: things were pretty chaotic and crazy, and so maybe why not,
Speaker 1: why couldn't you just have black holes form and that
Speaker 1: kind of primordial high energy soup. Yeah, you could have.
Speaker 1: And if you did that, then you could have gotten
Speaker 1: a bunch of really tiny black holes and intermediate mass
Speaker 1: black holes and maybe even supermassive black holes, or big
Speaker 1: enough at least to become a seed which later turned
Speaker 1: into these early supermassive black holes. And so it might
Speaker 1: be possible that the supermassive black holes were seeing were
Speaker 1: never intermediate mass, that they formed like suddenly during the
Speaker 1: Big Bang, already fifty thousand solar masses and then just
Speaker 1: grew to a billion masses. So the point there is
Speaker 1: just because you have really big black holes doesn't mean
Speaker 1: they were once medium sized. Right. It's it's kind of
Speaker 1: like having a birthmark, like a mall you're born with,
Speaker 1: not a mall of that shows up later. Yeah, and
Speaker 1: there's a lot of really fun stuff. We have a
Speaker 1: whole episode about primordial black holes, which is a really
Speaker 1: fascinating topic because they might actually be real and out there,
Speaker 1: and some people still think they might account for the
Speaker 1: dark matter. So it's a really fun topic. The problem
Speaker 1: with primordial black holes is that if you make them,
Speaker 1: you expect to make them out all sizes, like really
Speaker 1: big ones and then also really little ones and the
Speaker 1: smaller ones. We should see those, and we should see
Speaker 1: them evaporating, because from small black holes evaporate and they
Speaker 1: give off radiation and as they give off radiation, they
Speaker 1: get smaller, and as they get smaller, they give off
Speaker 1: more radiation, so they would evaporate very brightly and we
Speaker 1: should see that, and we haven't. So there's some skepticism
Speaker 1: about whether primordial black holes are a thing. You're saying, like,
Speaker 1: at the beating of the universe, we don't see evidence
Speaker 1: for those little tiny black holes for me. Yeah, we
Speaker 1: don't see evans for it. It doesn't mean that they
Speaker 1: didn't happen, but we don't see evidence for it. So
Speaker 1: if primordial black holes are the explanation for super massive
Speaker 1: black holes, you need some reason why they basically only
Speaker 1: got made on the larger size and they didn't make
Speaker 1: littler ones that we would also be seen. But that's
Speaker 1: not the only problem with that theory, right that Also
Speaker 1: the theory is that even if you had started with
Speaker 1: tiny black holes from the Big Bang, there's no way
Speaker 1: they could have grown that big to what we see today. Yeah, well,
Speaker 1: you need to make primordial black holes to be pretty big,
Speaker 1: so you need to start from pretty large primordial black
Speaker 1: holes so that they could be big enough to seed
Speaker 1: the supermassive black holes we see today. You'd make them
Speaker 1: at all ales in the Big Bang from tiny to
Speaker 1: really massive. And I see. And the problem is that
Speaker 1: we don't see evidence for those large seeds or what well,
Speaker 1: that would explain the supermassive black holes. But we would
Speaker 1: also expect to see the little ones, and we don't
Speaker 1: see the little ones anywhere. Like the little ones. We
Speaker 1: should see those evaporating all over the galaxy like they
Speaker 1: should last, you know, a few billion years, and they
Speaker 1: should be evaporating in these bright flashes of light as
Speaker 1: they disappear. But we don't see that. So that means
Speaker 1: that there aren't little primordial black holes. Doesn't mean there
Speaker 1: weren't really big primordial black holes, but it means there
Speaker 1: weren't really little primorial black holes. And that means that
Speaker 1: it's a little bit more complicated to explain. Oh, I
Speaker 1: see right, because we can see back in time. Right
Speaker 1: when we look at into space, we can sort of
Speaker 1: see back in time towards what was there close to
Speaker 1: the Big Bang. Exactly, we do literally see back in
Speaker 1: time because light takes time to get here from Earth.
Speaker 1: We're seeing now what happened a million or a billion,
Speaker 1: or five or ten billion years ago. As we look
Speaker 1: deeper into the universe. It's really pretty awesome that we
Speaker 1: can look backwards in time. But there are also other
Speaker 1: ways that you could form these sue for massive black
Speaker 1: holes without going through the intermediate mass black hole route right.
Speaker 1: You could, for example, even without forming them in the
Speaker 1: Big Bang, you could have this scenario where super massive
Speaker 1: black holes formed directly from clouds of gas and dust.
Speaker 1: It's called direct collapse. They never stopped and become a
Speaker 1: star and burn for billions of years. First they just
Speaker 1: go straight to black hole. Really, you can do that.
Speaker 1: You can just form a black hole without igniting and
Speaker 1: with fusion and everything. It's a theory. We've never proven
Speaker 1: it and we've never seen one, but it's a theory
Speaker 1: that people can't rule out. If you have enough stuff,
Speaker 1: like a really big blob of stuff, then it collapses
Speaker 1: fast enough the fusion doesn't have a chance to slow
Speaker 1: it down and repel it, and it just goes straight
Speaker 1: to black hole. And you can sort of simulate it,
Speaker 1: and that can actually happen, like if you like the
Speaker 1: clouds somehow takes up enough speed compressing that it starts
Speaker 1: to night in the middle, but it's too late. There's
Speaker 1: more stuff falling in and then poof, it becomes a
Speaker 1: black hole. Yeah, grand gravity wins. And again it's still
Speaker 1: just a theory, but the calculations check out out. We've
Speaker 1: never seen when we don't have direct evidence for it.
Speaker 1: But it's a way to potentially explain how these supermassive
Speaker 1: black holes got started and then had a chance to grow.
Speaker 1: And it would be another way to have really big
Speaker 1: black holes without ever going through this middle phase, this
Speaker 1: awkward teenage years of the black hole, when you head
Speaker 1: between a hundred and ten thousand solar masses. They could
Speaker 1: have directly collapsed to something really really big fifty tho
Speaker 1: solar masses and then just kept growing from there. Isn't
Speaker 1: there another theory that these supermassive black holes come from
Speaker 1: smaller black holes colliding and merging into bigger and bigger ones.
Speaker 1: For sure, But that takes a long time, right. If
Speaker 1: you think that these big black holes came from really
Speaker 1: tiny black holes, then they spend a long time in
Speaker 1: the tiny stage, right because the gravity is proportional to
Speaker 1: the size of it. And so if you start from
Speaker 1: just like one stellar black hole and then at another
Speaker 1: and at another, there's not enough time in the universe
Speaker 1: to get up to billions of solar masses. That's the problem, right,
Speaker 1: because I guess you know it thinks in space on
Speaker 1: just like collapse head on. Right, they have to circle
Speaker 1: each other for a while, you have to date, you know,
Speaker 1: you have to go grab some coffee, eat some cookies,
Speaker 1: and then eventually they collapse into each other. Right, that's
Speaker 1: kind of the idea, Like things just don't running to
Speaker 1: each other out there in space. Yeah, it's not like
Speaker 1: some huge cosmic kid out there is trying to build,
Speaker 1: you know, a supermassive black hole by sticking the black
Speaker 1: hole legos together. It's got to happen. And for that
Speaker 1: to happen, the things have to be in the right
Speaker 1: arrangement and they have to collapse into each other. And
Speaker 1: it gets easier as your black hole gets bitter because
Speaker 1: it's more powerful and it can gobble stuff, so like
Speaker 1: the sphere of its influence grows and where it can
Speaker 1: eat from grows, so then it grows more quickly. But
Speaker 1: that's why a black hole that starts from a really
Speaker 1: small object spends most of its time small before it
Speaker 1: accelerates its growth near the later phase. So we would
Speaker 1: see those and they would take too long to get
Speaker 1: to the supermassive black hole stage, so they can't explain
Speaker 1: all the really old, huge black holes that we see, right,
Speaker 1: and so that's the big mysteries that we know where
Speaker 1: the smaller size black holes come from. They come from stars,
Speaker 1: and then we see a bunch of the huge black
Speaker 1: holes in the center of galaxies, but we don't see
Speaker 1: the ones in between, and we don't know how the
Speaker 1: big ones got as big as they did, Yeah, exactly.
Speaker 1: We don't know those big ones were once intermediate size,
Speaker 1: and we can't see any examples of the intermediate sized ones,
Speaker 1: which seems like a head scratcher, right. Yeah, it's kind
Speaker 1: of like a double mystery, like we don't know how
Speaker 1: they got so big, and also we don't see any
Speaker 1: of the middle ones. Yeah, and we'd love to unravel
Speaker 1: that mystery. We'd love to understand how these supermassive black
Speaker 1: holes form. And so finding one like when it was
Speaker 1: a child might really give us a clue to how
Speaker 1: they formed, or if we could prove that they never
Speaker 1: were children, they were like fully born as supermassive black holes,
Speaker 1: then one fell swoop that would also be fascinating. That
Speaker 1: is a possibility, is that maybe they were made super
Speaker 1: big in the big bank as primordial black holes or
Speaker 1: through direct collapse. There are some mechanisms to make these
Speaker 1: things and skip that intermediate phase. Right, That would make sense, right,
Speaker 1: you know, to have their own proper origin story that
Speaker 1: doesn't involve growing. Yeah, it does make sense. But you know,
Speaker 1: galaxies come in all sizes. There are really big galaxies
Speaker 1: and there are smaller galaxies, and it goes down to
Speaker 1: pretty small like galaxies can be down to just a
Speaker 1: few thousand stars. And so if black holes inside galaxies
Speaker 1: are proportional to the mass of the black hole, and
Speaker 1: again we don't know that, we've just seen that relationship
Speaker 1: for larger galaxies, then it stands to reason that these
Speaker 1: smaller galaxies should have smaller black holes inside them. Well
Speaker 1: that's the mystery, and so let's talk about now how
Speaker 1: we could find them or are people looking for these
Speaker 1: medium sized black holes and is it theoretically possible to
Speaker 1: see them or that they can exist. So let's get
Speaker 1: into that, but first let's take another quick break. Alright,
Speaker 1: we're talking about the ignored middle child, i'll black holes
Speaker 1: of the universe, And I know this is a personal
Speaker 1: topic for you. Daniel I'm sticking up for these black holes.
Speaker 1: You're just trying to make them the cool ones. I think, Yeah,
Speaker 1: we're like, who cares about? The little ones are the
Speaker 1: big ones, They get all the attention. The cool ones
Speaker 1: are the ones that you know, sit in the back
Speaker 1: and plot their revenge with a podcast years later, decades,
Speaker 1: decades into making This is My Revenge. No, set the
Speaker 1: record straight. I love my brothers. They're wonderful and they're supportive,
Speaker 1: and we're all very good friends. Right, Yes, did that
Speaker 1: not sound sincere I meant it to. That sounded a
Speaker 1: little tacked on at the end, But hey, you know,
Speaker 1: I know how it goes your lawyer or a therapist.
Speaker 1: Is there supposed to be a difference? Really? All right, well,
Speaker 1: let's get into this mystery of the medium sized black holes.
Speaker 1: We can't see them anywhere, now, Daniel. Do you think
Speaker 1: we don't see them because we can't see them or
Speaker 1: because they don't exist? That's the question. We don't know
Speaker 1: the answer too, because frustratingly, smaller black holes are harder
Speaker 1: to see. Like, one thing we're pretty good at is
Speaker 1: figuring out what we're good at, and we're good at
Speaker 1: seeing really big black holes because we can see them
Speaker 1: affect how stars move in the center of galaxies, or
Speaker 1: sometimes they have like huge quasars. We also know that
Speaker 1: we're not very good at seeing smaller black holes, and
Speaker 1: so we haven't seen any. But we also know that
Speaker 1: we're not great at spotting them, so that leaves the
Speaker 1: questions sort of up in the air. Right. Yeah, even
Speaker 1: the ones that come from giants sons, they're kind of
Speaker 1: hard to spot in space, right, It's not like they glow,
Speaker 1: they're transparent invisible, and space is pretty dark, and maybe
Speaker 1: they're not heavy enough to kind of like have a
Speaker 1: big impact in the stars around them. Yeah, you have
Speaker 1: to infer them. You have to be lucky. So you
Speaker 1: have to see for example, gravitational lensing where the light
Speaker 1: that passes near them gets bent as if there was
Speaker 1: a huge invisible mass of stuff there, and you know,
Speaker 1: you have to know that it's really compact and dense,
Speaker 1: so it's not just like some big diffuse cloud or
Speaker 1: dark matter, or you have to see their impact on
Speaker 1: other nearby stars with nothing else to explain it. So
Speaker 1: it's usually just like a process of elimination. We see
Speaker 1: something happening in space and we can't explain it in
Speaker 1: any other way other than a black hole. It's pretty rare.
Speaker 1: You get very direct evidence of a black hole though sometimes,
Speaker 1: and that's usually in the center of a galaxy, when
Speaker 1: they're really big and there's like quasar emissions and other
Speaker 1: stars moving very close to them. Have we seen the
Speaker 1: smaller black holes, like, is there a catalog of them
Speaker 1: or are they still kind of theoretical that they exist? Now,
Speaker 1: we have definitely observed stellar mass black holes. Absolutely, we've
Speaker 1: seen their gravitational lensing, we have seen their effect on
Speaker 1: other bodies. In fact, we did a whole fun podcast
Speaker 1: episode about the history of how people became convinced that
Speaker 1: was not just a mathematical concept, but they were real
Speaker 1: and they were out there, and the first one was
Speaker 1: at the center of our galaxy is supermassive black hole.
Speaker 1: But then later we observed a few candidates whereas a
Speaker 1: stellar mass black hole m I see. And so we
Speaker 1: see those, and we sort of see them in our
Speaker 1: neighborhood kind of in our galaxy at least, but we
Speaker 1: don't see the ones that are bigger, which you would
Speaker 1: think we'd see, right because they are more massive and
Speaker 1: so they would have more more of an impact on
Speaker 1: the motion of stars around them, but we don't see them.
Speaker 1: We see them if they're big enough, right, A million
Speaker 1: mass black hole has a big impact on what's going
Speaker 1: on in the center of galaxy. And so we can
Speaker 1: look at those galaxies and we can study the motion
Speaker 1: of stars in their center, and we can infer the
Speaker 1: presence of a black hole, just like we do for
Speaker 1: our galaxy. The problem is that smaller galaxies have fewer
Speaker 1: stars and smaller black holes. So if you're looking at
Speaker 1: a smaller galaxy like a dwarf galaxy, and you're trying
Speaker 1: to understand does the motion of the stars tell me
Speaker 1: there's some invisible sorts of gravity there? Then these are
Speaker 1: small galaxies. It's sort of hard to just like get
Speaker 1: the angular resolution you need to tell the motion of
Speaker 1: the stars in these far away small galaxies. Oh, I see.
Speaker 1: So you're saying that maybe they are there in smaller galaxies,
Speaker 1: but we just can't tell. We know that we can't
Speaker 1: see them. We know that if they were there, we
Speaker 1: could not see them today. We just do not have
Speaker 1: the resolution in current tell lescopes to see these stars
Speaker 1: moving well enough to answer the question is there an
Speaker 1: intermediate mass black hole there, Like, we just don't have
Speaker 1: the eyeballs that we need. So they could be out there,
Speaker 1: then it could be out there. We know that we
Speaker 1: couldn't see them if they were there, so they could
Speaker 1: be out there. And we have big plans like the
Speaker 1: thirty meter telescope or the extremely large telescope. These are
Speaker 1: things that are being built now and will come online
Speaker 1: in tennish years. These will have much better resolution. They'll
Speaker 1: be able to like get crisper pictures of these small
Speaker 1: galaxies that are far away, to get a sense for
Speaker 1: the motion of the stars near their center and tell
Speaker 1: us if there's an intermediate black hole there or not.
Speaker 1: We just can't see them today, and we haven't been
Speaker 1: able to see them, right, Like, we know that they've
Speaker 1: been kind of hiding from us if they exist, which
Speaker 1: we don't know if they exist. Yeah, we know they've
Speaker 1: been hiding from us. But that's just one technique to
Speaker 1: see intermediate mass black holes, right is to look for
Speaker 1: the motion of the stars near their center. There are
Speaker 1: other techniques that people have been trying as well. What
Speaker 1: are those techniques? Well, another one is not to look
Speaker 1: at galaxies at all, but to look for other kinds
Speaker 1: of things. Is this stuff out there in the universe
Speaker 1: called globular clusters. We had a whole fun podcast EFFS
Speaker 1: just about what are globular clusters and how much fun
Speaker 1: it is to say that word. But these are weird
Speaker 1: spherical collections of stars, and because they're much smaller than galaxies,
Speaker 1: people think they might have intermediate mass black holes in them.
Speaker 1: The upside is that they're much closer than other galaxies.
Speaker 1: They tend to be like orbiting our galaxy. Like we
Speaker 1: have several globular clusters orbiting our galaxy, so they're nearby,
Speaker 1: so we can like take pretty good pictures and see
Speaker 1: the motions of the stars inside them and get a
Speaker 1: sense for whether or not there's an intermediate mass black
Speaker 1: hole inside. Oh, I see these clusters. They're busier basically, right,
Speaker 1: They have more stuff to them, more stars, and so
Speaker 1: you would be able to maybe see the effects of
Speaker 1: a medium black hole in them. Yeah, and they're much
Speaker 1: closer than these other dwarf galaxies which tend to be
Speaker 1: pretty distant, and so we would have a shot. The
Speaker 1: problem is that these globular clusters aren't as tightly packed
Speaker 1: sometimes as a dwarf galaxy, and so the speeds of
Speaker 1: the stars are slower, so it's hard to tell if
Speaker 1: there's an intermediate mass black hole. There are not. You
Speaker 1: need to take pictures over like decades to see the
Speaker 1: motions of those stars and infer it. And there's a
Speaker 1: few globular clusters out there where people think maybe there's
Speaker 1: a black hole there based on the measurements of velocities
Speaker 1: of the stars, but none of them really hold a
Speaker 1: to scrutiny. Like somebody announces, wow, look we found an
Speaker 1: intermediate mass black hole, and then another group looks at
Speaker 1: the same measurements and they say, no, we can explain
Speaker 1: this without a black hole, So it doesn't really hold up.
Speaker 1: You see, it's tricky. It's tricky because you have to
Speaker 1: kind of like see the footprint of the black hole,
Speaker 1: and it's not easy to do. And another technique is
Speaker 1: to look not for the motion of stars, but for
Speaker 1: the radiation from the accretion disc Right, we know that
Speaker 1: black holes are not on their own, and especially the
Speaker 1: massive ones in the centers of galaxies are surrounded by
Speaker 1: gas and dust that's emitting a lot of radiation, so
Speaker 1: these are called quasars. And we think that intermediate mass
Speaker 1: black holes should also have intermediate mass accretion disks and
Speaker 1: be intermediate as quasars, So we're looking for these as well.
Speaker 1: Really we've only seen like supermassive quasars or stellar size quasars. Yes,
Speaker 1: we've only seen supermassive quasars. Stellar mass black holes don't
Speaker 1: tend to have quasars because they don't have the mass
Speaker 1: to get their creation disk like up to that energy,
Speaker 1: so they tend to only be from the centers of galaxies.
Speaker 1: And the problem here is that we're looking for like
Speaker 1: really old galaxies before they got really really big, so
Speaker 1: like intermediate size galaxies, and these tend to be pretty
Speaker 1: far away. And if you're looking for the black hole,
Speaker 1: because it's a quasar, it tends to like drown out
Speaker 1: the rest of the galaxy, so you can't like really
Speaker 1: see what's going on in the galaxy. So we have
Speaker 1: these quasars we've identified as maybe candidates for intermediate mass
Speaker 1: black holes, but they're so far away we can't like
Speaker 1: see the stars and really identify whether there's a black
Speaker 1: hole there. Oh, I see, because there could just be
Speaker 1: like a bunch of stars, yeah, clustered together. So but
Speaker 1: that's one thing people are doing. But I think the
Speaker 1: most exciting is this brand new way we have looking
Speaker 1: at the universe first seeing things that's not based on
Speaker 1: light but based on gravitational waves, right, like the ripples
Speaker 1: and off space. Yes, out there in the universe, the
Speaker 1: ripples in space itself, because when anything accelerates in the universe,
Speaker 1: it creates a change in the gravitational field, and that
Speaker 1: change ripples through space. And if the thing is really
Speaker 1: really big, really really massive, and moving really really fast,
Speaker 1: then you can actually measure these gravitational waves billions and
Speaker 1: billions of light years away, and we have and the
Speaker 1: things that have generated the gravitational waves that we've been
Speaker 1: able to see here on Earth in observatories like Lego
Speaker 1: are the mergers. For example, of two black holes falling
Speaker 1: into each other, they accelerate around each other in this
Speaker 1: crazy death spiral, emitting a huge amount of energy as
Speaker 1: gravitational waves, and that we can use to figure out
Speaker 1: how massive were the two black holes that fell in
Speaker 1: and how massive is the resulting black hole, right because
Speaker 1: you're seeing like the actual ripples and gravity from these
Speaker 1: black holes, So just the ripple itself kind of tell
Speaker 1: how big the things are that are crashing into each
Speaker 1: other it's a very very detailed fingerprint because the ripples
Speaker 1: tell you how fast things were going, and from that
Speaker 1: you can back out things like how massive they must
Speaker 1: have been, how strong was the gravity, and so yeah,
Speaker 1: you can figure out how massive the individual black holes
Speaker 1: were before they collapsed, and the mass of the final
Speaker 1: black hole, which is not just the two black holes
Speaker 1: added together. Some of the energy from the original two
Speaker 1: black holes get lost in gravitational radiation, these gravitational waves,
Speaker 1: and so the idea is that you know, we can
Speaker 1: listen to when these black holes crashing into each other,
Speaker 1: and so you're saying, like, maybe one day we'll see
Speaker 1: or hear are the tag two intermediate black holes crashing
Speaker 1: into each other, and then we'll be able to say, hey,
Speaker 1: there's an intermediate one. Yes, absolutely, that's a possibility, because
Speaker 1: we can use this as a way to weigh black
Speaker 1: holes and we cannot otherwise directly see right, because remember,
Speaker 1: gravitational waves can pass through anything. No amount of gas
Speaker 1: or dust or radiation or whatever can stop them. So
Speaker 1: it's just another very powerful orthogonal way of looking at
Speaker 1: the universe, so we can get glimpses. Also, there's another
Speaker 1: angle there, which is maybe we can see two really
Speaker 1: really big stellar mass black holes merge. Like what happens
Speaker 1: when an eighties solar mass black hole and a seventies
Speaker 1: solar mass black hole get together, Well, they must form
Speaker 1: a black hole that's heavier, right, that maybe even over
Speaker 1: that threshold into the intermediate mass range. Here, it's an
Speaker 1: X rated event there that Yeah, and this has actually happened.
Speaker 1: And in two thousand nineteen they did see a merger
Speaker 1: that resulted in a black hole that weighed a hundred
Speaker 1: and forty two solar masses. And so this is really cool.
Speaker 1: You can look this up on Lego. They call this
Speaker 1: the black hole graveyard, and they showed like the masses
Speaker 1: of the black holes that formed the new black holes.
Speaker 1: And so we're now seeing more and more of these things,
Speaker 1: and they're sort of pushing up that limit. Like it's
Speaker 1: true that you can't make a black hole from a
Speaker 1: single star that's bigger than eighty but as you said earlier,
Speaker 1: as you start to combine these, they can creep up
Speaker 1: a little bit and get over that hundred stellar mass threshold. Right,
Speaker 1: And we've seen this, right, you're saying, you can go
Speaker 1: online and look at the data of a hundred and
Speaker 1: forty two solar mass black hole basically being born. Yes,
Speaker 1: you can see it. It happened billions of years ago,
Speaker 1: but just recently seeing the evidence here on Earth, so
Speaker 1: that's exciting. It sort of cracks that number. It doesn't
Speaker 1: really answer the mystery, right because it doesn't explain why
Speaker 1: we don't see them. At A thousand and five thousand
Speaker 1: and ten thousand, it's like just over the threshold of
Speaker 1: what you might consider intermediate mass black hole. But we're
Speaker 1: planning to build future crazy gravitational observatories that might be
Speaker 1: able to see even bigger ones from further away. I
Speaker 1: don't know if you've heard about the Lisa experiment. No,
Speaker 1: what is it. The Lisa experiment is a version of Ligo.
Speaker 1: This experiment we have mirrors dangling underground in Louisiana and
Speaker 1: in Washington and in Italy to observe the ripples of space.
Speaker 1: This is a version of it, but using three satellites
Speaker 1: in space placed like really really far apart, but precisely
Speaker 1: aligned relative to each other. Wow, that's pretty cool in space.
Speaker 1: In space, I know, it's names bonkers, right that you
Speaker 1: could have like two satellites and have them maintain an
Speaker 1: exact distance relative to each other. It's going to be
Speaker 1: very complicated and very expensive. But if they build it
Speaker 1: this facility, Lisa will be very powerful at seeing gravitational
Speaker 1: waves and you could detect them from intermediate mass black
Speaker 1: hole murders Lisa in space. It sounds like a song.
Speaker 1: He ripped that off from the Beatles, Lisa and the
Speaker 1: Sky black Holes. All right, Well, I think you convince me, Daniel.
Speaker 1: I think the middle children are pretty cool or they
Speaker 1: don't exist one of the two. Sometimes I feel that way.
Speaker 1: They're definitely lurking, They're big. Middle children are big lurkers.
Speaker 1: For sure. We are psychological lurkers. Yes, So it's a
Speaker 1: really fun question like why don't we see these things?
Speaker 1: How did the supermassive black holes get so big without
Speaker 1: going through this stage? Or maybe we don't see them
Speaker 1: just because we don't have the telescopes yet, And in
Speaker 1: twenty or thirty years we'll see a bunch of them
Speaker 1: and they'll answer a lot of our questions about how
Speaker 1: black holes get made because they are, I guess, in general,
Speaker 1: just a cool family. You know, the youngest siblings and
Speaker 1: the oldest siblings. They're all pretty cool in their own
Speaker 1: way and pretty impactful in the universe. Right, everybody contribute
Speaker 1: to the family. We love every part of it. All right,
Speaker 1: I guess we'll leave that question dankling. What happened to
Speaker 1: the intermediate black holes? Nobody knows. It's a black hole
Speaker 1: in itself of information, but we'll figure it out. Stay
Speaker 1: tuned for more updates from science. You might have to
Speaker 1: wait another three episodes until Daniel figures it out his therapist,
Speaker 1: but we'll get there, okay, all right. We hope you
Speaker 1: enjoyed that. Thanks for joining us, See you next time.
Speaker 1: Thanks for listening, and remember that Daniel and Jorge explained.
Speaker 1: The Universe is a production of I Heart Radio. For
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