The video explores the deep and captivating mysteries of black holes, a concept initially met with skepticism even by renowned scientists like Einstein. Black holes possess singularities that cause the breakdown of einstein's equations, a phenomenon similar to dividing by zero in mathematics. This breakdown has led to continued investigations into the formation and properties of black holes, especially given the firm evidence of their existence. The conversation features Priya Natarajan, an expert at Yale University, who delves into the cosmic history and explorations of black holes, highlighting their enigmatic nature and the ongoing quest to understand them fully.

The development and acceptance of black holes as a real phenomenon were not immediate. From the initial skepticism about the possibility of their existence, with core contributions from scientists like Schwarzschild and Chandrasekhar, to the mathematical confirmations by figures like Oppenheimer and Penrose, the video traces the scientific journey toward acceptance. Recent observational studies using advanced technology such as the James Webb Space Telescope have provided invaluable data, allowing a better understanding and even direct imaging of these mysterious entities, making the case for their existence undeniable.

Main takeaways from the video:

Please remember to turn on the CC button to view the subtitles.

Key Vocabularies and Common Phrases:

1. singularity [ˌsɪŋɡjʊˈlærɪti] - (n.) - A point where a mathematical object is undefined, typically involving infinite values or conditions in a space. - Synonyms: (point anomaly, peculiarity, anomaly)

That is, when you get to the center of a black hole, to the singularity of a black hole, einstein's equations, they break down.

2. incontrovertible [ɪnˌkɒntrəˈvɜːtəbl] - (adj.) - Not able to be denied or disputed; absolute. - Synonyms: (undeniable, incontestable, irrefutable)

We have incontrovertible evidence that black holes are real.

3. astrophysical [ˌæstrəʊˈfɪzɪkl] - (adj.) - Relating to the branch of astronomy that deals with the physics of celestial objects and phenomena. - Synonyms: (celestial, astronomical, cosmic)

So it was a very apt term that then got picked up by John Wheeler much later to describe these astrophysical objects.

4. relativity [ˌrɛləˈtɪvɪti] - (n.) - A theory by Einstein about the relationship between space, time, and gravity. - Synonyms: (special relativity, general relativity, factuality)

Within Einstein's own general theory of relativity, there exists an entity whose physical properties break the very rules on which physics more broadly and general relativity more specifically are based.

5. cosmic [ˈkɒzmɪk] - (adj.) - Pertaining to the universe, especially when regarded as an orderly system. - Synonyms: (universal, galactic, astronomical)

Priya Natarajan, who is the Joseph S. And Sophia S. Frutton professor of Astronomy and Physics at Yale and studies the formation of black holes over the course of cosmic history.

6. opposition [ˌɒpəˈzɪʃən] - (n.) - Resistance or dissent, expressed in action or argument. - Synonyms: (resistance, dissent, objection)

It was a theoretical idea, but there was a lot of opposition to that idea for quite a while

7. einstein's equations [ˈaɪnstaɪnz ɪˈkweɪʒəns] - (n.) - Mathematical equations formulated by Einstein, expressing the fundamental relationships between geometric properties of space and the energy and momentum contained within it. - Synonyms: (field equations, gravitational equations, Einstein's field laws)

That is, when you get to the center of a black hole, to the singularity of a black hole, einstein's equations, they break down

8. penrose's theorem [ˈpɛnroʊzɪz ˈθɪrəm] - (n.) - A theorem about the incompleteness of the universe and the necessity of singularities within it under general conditions in general relativity. - Synonyms: (singularity theorem, gravitational collapse proof, Penrose's singularity argument)

And then Roger Penrose comes along and of course, ultimately the work earns him a share of the Nobel Prize.

9. accretion disk [əˈkriːʃən dɪsk] - (n.) - A structure formed by diffused material in orbital motion around a central body, typically in a swirling, flat formation. - Synonyms: (accretion structure, orbital disk, material swirl)

And the signature is that it should also glow in the X rays. And these objects would be quite faint. This is from the accretion disk around the black hole, producing.

10. event horizon [ɪˈvent həˈraɪzən] - (n.) - A boundary surrounding a black hole beyond which no matter or radiation can escape. - Synonyms: (boundary line, black hole border, horizon of no return)

So this is the formula of a very defining quantity for a black hole, and that's called the event horizon.

SUPERMASSIVE BLACK HOLES - Rethinking Their Origin

Thank you. Now, a number of people have been credited with the quote that no doubt you have heard. Black holes are where God divided by zero. Einstein has been credited with. Hawking has been credited with. I believe the correct attribution is to the comedian Stephen Wright, as it turns out. But regardless, the quip does highlight something true and important, which is this. Within Einstein's own general theory of relativity, there exists an entity whose physical properties break the very rules on which physics more broadly and general relativity more specifically are based. That is, when you get to the center of a black hole, to the singularity of a black hole, einstein's equations, they break down. And they break down in a manner, in fact, that is not unlike dividing by zero.

Now, because of this, unsurprisingly, Einstein himself, he was deeply skeptical that black holes were real. But by now, that ship has long since sailed. We have incontrovertible evidence that black holes are real. Yet that does not mean that we fully understand their structure or their formation. And our guest for this conversation has been really thinking very deeply about black holes, their properties and their formation, and has made a really bold suggestion about black holes that we will get to, which might just be receiving observational support, which would be a potentially wonderful step forward.

So I am so thrilled to introduce you to Priya Natarajan, who is the Joseph S. And Sophia S. Frutton professor of Astronomy and Physics at Yale and studies the formation of black holes over the course of cosmic history. She was named by Time magazine as one of the hundred most influential people of 2024. So great to see you, Priya. Thanks for joining us for this conversation. And I'd like to kind of jump right in to this subject of black holes because, you know, everybody's heard of these monstrous structures out there in the cosmos, and yet there are so many deep puzzles that still remain.

I thought just to kind of set context, ultimately, for the work of yours that I want to get to, if we can just sort of walk through the history of. Of thinking that led to this concept of black holes and ultimately for its observational support. So, I mean, where would you pick up the story with Karl Schwarzschild? Is that sort of a natural place, or is there another spot? First of all, thank you so much for inviting me. I'm so delighted to be here. Absolutely. And talking to all of you, I think we may want to start, strangely, perhaps, with the black hole of Calcutta.

So it turns out I know there's an Indian connection. Right. So Indians are notorious for this. We always kind of find a connection. So it turns out it was an infamous prison when the British East India Company was trying to make its way, and the local Nawab had actually imprisoned some officers overnight. And it was a place of no return. So it was a very apt term that then got picked up by John Wheeler much later to describe these astrophysical objects. But you're right, truly, where the story begins is with Einstein's theory of general relativity and Schwarzschild finding the first exact solution. Einstein never imagined that there might be an exact solution.

This just really corresponds in a simple way to the shape of space, space around a very compact distribution of matter. And it's a very peculiar, very strong distortion in the geometry of space. And Einstein, of course, one of the amazing things he did with his theory was to show that the geometry, the contents and the fate of the universe and of any entity in the universe were interrelated. And an exact solution would mean the shape of space around distribution of matter.

Now, it's an important point you make there that Einstein himself was not the first person to solve einstein's equations. Absolutely. And he actually. They're so messy that he never really imagined there would be an exact solution. Yeah. So he, like, got these approximate solutions that were pretty good. Got the bending of starlight by the sun from the approximate solutions. Yeah. But then Schwarzschild, within six months.

Right. Schwarzschild was actually fighting in the trenches, World War I. But Einstein had given this lecture at the Prussian Academy of Sciences. Swarchile heard about it in the trenches, and he found he was a fool. He had really good hearing out there. Not damaged yet. And can you imagine just nerding out when you're fighting and then coming back home and doing sort of in the evening? Maybe it was a way of dealing with the stress.

But he found a solution and he wrote to Einstein. And Einstein thought it was fantastic with solution, but he didn't think it was real. He thought this is like a nice, cute mathematical solution. And I think that's the way they remained for quite a while. The basic idea, he was assuming you had a spherical mass, you crush it sufficiently small and you. Yeah, bring it pretty much to a point, reduce it pretty much to a point, and then you would have an extreme distortion of space time, literally like a puncture in space time.

In fact, they had this formula, if we can just bring it up as a point of reference, tell us what we're seeing there. So this is the formula of a very defining quantity for a black hole, and that's called the event horizon. So this is sort of a sacred boundary for the black hole where essentially beyond this event horizon, the change in shape, the geometry of space time, is so extreme that anything that crosses this boundary never makes it back out, including light. Not just anything material, but also light. So this is an enigmatic property in many ways, I have to admit. This is one of the reasons the existence of an event horizon is what kind of tantalized me when I was a kid reading about this.

But it also turned off Einstein in a sense, because if you plug in, for instance, the mass of the sun into this formula, it, it tells you how much you'd have to squeeze the sun 3km, which is ludicrous sounding. You plug the Earth in there and you have to squeeze it down to a couple centimeters or something like that. Like a penny or something. Yeah. So how could you possibly do that? And yet we're gonna talk about ways that we think nature does it, that nature does it. And there may be novel ways if indeed this happens.

I mean, just to get sort of a picture of what the resulting region of space would look like. Absolutely. And I think what is really remarkable is that from all the skepticism, including from Einstein himself, kind of proposed the theory, right now we are finding pretty much every galaxy in the universe harbors one of these mysterious objects in its heart. And these black holes that are seen in the centers of galaxies, like the visualization you're all seeing is about often millions of times the mass of the sun, could even be billions, billions as well, which is sort of mind boggling scales.

And following again the history en route to having confidence that these objects were real before observations that we'll come to really nailed the case. Chandrasekhar was one who played a vital role. Can you just describe how he advanced our understanding here? Yeah. So I think Chandrasekar was the first person to make the connection of a class of existing astronomical object stars that were pretty well understood and showed that any star that by birth started off life with a mass about eight to ten times the mass of the sun or larger, would inevitably live its life out and explode and end up as a black hole. This was a theoretical prediction that he made.

In fact, he was able to work out that the stellar corpses. There were three kinds of stellar corpses. Compact objects, neutron stars, white dwarfs, and black holes. The most extreme would be the black holes. It was a theoretical idea, but there was a lot of opposition to that idea for quite a while. So it took. Once again, it's the peculiar properties of the black hole that Cause skepticism. And as you mentioned right away that one of. In your introduction, one of the peculiar properties other than the event horizon is the sort of breakdown of all physical laws as we understand them.

Once you edge closer and closer to the ultimate singularity, for which we don't quite even today have the right language to describe, I think there's been a lot of progress. So it's very enigmatic. So there's a lot of opposition to that idea. So we certainly won't answer the question of the singularity unless you're going to break some news here today. I want to stick to the real black holes. Well, but the real, real black holes have something going on down there that ultimately we have to address, because once we know they're real, they've got to make sense.

And singularity is nature's way of telling us that our mathematics is wrong. Right, Right. Or also so the limits of our current understanding. And so, again, these are the kinds of things. I mean, even Einstein himself, I think this paper is. What is it? 1939, wrote papers trying to argue that, sure, under these simplified, highly symmetric assumptions, perhaps you can get this mathematical solution, but it's not a real physical thing in the real world. But can you imagine, Brian, a scientist, actually writing a paper like, contradicting what his own theory predicts? I mean, Einstein was really. Yeah, he was definitely a liberal thinker.

You know, such a nice way of putting it. And he did it more than once. Absolutely. With the expansion of the universe. He was a holdout. He did not like aesthetically. He was so attached to the idea of fixity, he did not want to hear about the evidence. Ultimately, Hubble convinced him because there was enough observational evidence that Einstein could not be a holdout anymore. Yeah. And so he absolutely followed where the evidence took him, but en route, certainly had these interesting moments of not trusting the results from the equations that he himself had given the world, which is an absolutely interesting combination.

Now, I'd say among the next important steps in trying to understand whether black holes are real or not, you know, there is work, in fact, by Oppenheimer, who now, I think most people were at least somewhat aware of Oppenheimer until reason. Now everybody is, which is thanks to Christopher Nolan. Yeah. Which is a great thing. But I guess it was Oppenheimer and Snyder perhaps is the key paper. Yeah. So I think this was an important paper demonstrating numerically, computationally, actually following the explosion of a star all the way really close to as far as they could at the time that Numerica allowed them, and they were able to show that asymptotically, you're going to end up with an object that's going to be a gravitationally collapsed object.

I think that it's a very interesting point and a trajectory, which I think when we talk about new developments, we'll see it's the same trajectory. So you have a theoretical proposal, then you actually need a numerical demonstration, because in cosmology and astrophysics, we just can't do controlled experiments with the universe itself. So we simulate the universe in a box, the conditions. And once that's demonstrated, then there's faith in going and trying to look for these objects. I think that's sort of the same trajectory we follow still.

And I think the Oppenheimer Snyder paper is really important because it validated looking for signatures of a black hole. And then it was the discovery of Cygnus x1. From the mathematical standpoint, though, there was still an argument that people could make that whatever you're doing, it's still simplified. Right. And maybe if the star that's collapsing has enough irregularities or asymmetry, you know, that something will prevent this black hole from forming.

And then Roger Penrose comes along and of course, ultimately the work earns him a share of the Nobel Prize. But this, I think, had a dramatic impact on people's thinking. Yeah, absolutely. And I think he was again able to make a much stronger connection with the formation of the singularity, with the distortion in space time. And I think it's the work of Penrose and then Hawking after that that really sort of strengthened the idea and in a way normalized this concept of sort of extremal geometric distortion around a compact mass.

But with his results, all of a sudden was regardless of the impurity of the system, you were inevitably going to find yourself in the state of a black hole. And then you already mentioned, you know, John Wheeler was the fellow who picked up the name wherever the original origin may have came, but the black hole of Calcutta. Yeah, but do you know where it was that John Wheeler, where he was giving a talk when an audience member said, hey, it sounds like you're talking about a black hole. And he said, yeah, black hole. That's a good name.

I thought it was the relativistic meeting. Texas made in. Right. I don't think it was. I think it was. Anybody here. You know, you must be. I think Marsha Batushiak had tracked this data. No, here it is. Here it is. Watch this right here. It was there. What? No, really, you see, Tom's Diner right there. Right. That's the old Seinfeld. Seinfeld corner. So that's the Goddard Institute for Space Studies above it. And I am pretty certain that was at a lecture in that building that this. So that's where the term black hole comes from. So it was uttered first there. Okay. Now, I could be wrong, but I'm pretty sure that that's correct. If I am wrong, we'll cut this out of the digital version. You're absolutely certain about that?

Now, again, we're still sort of in the realm of theory. And then Andrea Ghez and collaborators, they begin to do exactly what you described. To start to look carefully at the center of our galaxy. Yeah. And starting to map essentially the shape of space and the impact of the shape of space on the motions of stars right around the black hole. So this is just incredibly beautiful work. I mean, every time I see this movie, I'm still, like, blown away that this is real data of real stars that have been followed for a couple of decades now.

And so this very. You can see, visually demonstrates this is sort of looking like the solar system and orbits. And you therefore know there is a very massive object at the focus that they're all whipping around. Basically, it has to be a black hole to account for the motions that you're seeing. And then, you know, just to really completely nail the case. Oh, yeah. Then you have direct imaging, finally, as close as up close as we will ever get to a black hole. So this is skirting just, you know, one and a half to two times outside the event horizon, where you're still able to see light that is sort of swirling around and is getting dramatically bent by the gravity of the black hole. And you're catching that.

So this is just a beautiful. It's my favorite donut. I'm with you on that, although I'm not a great fan of donuts. But it's a wonderful story of success. Absolutely. Coming from pure mathematics that churns across 100 years of human thought, ultimately resulting in a direct confirmation. That's kind of the dream that every one of us has.

And speaking of that dream, you're heading in the potential direction. Oh, my God, yes. Of a version of that dream. And so I thought it'd be good to now turn to the work that has been occupying you for quite some time, which is to think about alternate ways in which black holes could form. Right. And so give us a sense of. Yeah. So, I mean, this is super. It's super exciting, as you said. Right.

This Arc of proposing an idea, having, you know, working on it for a while, trying to persuade people that it might work, and then have people go out, look out for it and have all of that sort of close within the lifetime of a single scientific career. Yeah, it's just stunning. So I think the idea that we had. So this is work that I did with one of my postdocs in 2005, 2006, Giuseppe Laudato. And so at this time, what was happening was people finding these quasars which are basically actively feeding black holes, supermassive ones, farther and farther back in the universe. And they're super bright. They're like cosmic lighthouses.

And we can infer the masses of those black holes that are putting out that kind of beacon. And these were already sometimes a billion times the mass of the sun when the universe was barely a giga year, 2 giga years old. The entire universe today is 13.8 giga years. So just to give you a sense, it was really pretty close, so about a decade ago. So then the question was, if the seed black hole is the end state of a star that blows up, like Chandra told us, do we have enough time in the universe to grow it from 10 times the mass of the sun, maybe 50 times the mass of the sun, to a billion times the mass of sun?

Do we have enough time to make that happen with the physics that we currently understand about how black holes work? So it's basically eating up material in its environment and occasionally crashing into each other and maybe merging with it otherwise. Yeah, yeah. So it started to look challenging. So we said, oh, this is interesting. Can we just somehow make a black hole bypassing the formation of a star and make it be really massive from the get go? Like maybe can you start life? Can a black hole start life 10,000, 100,000 times the mass of the sun from its birth? Because then it alleviates the feeding timing kind of problem.

And so we found, actually just kind of thinking about the physics, not worrying at that time whether it's realistic, whether it can happen in our universe, just, can we get some physics to work? And we found we could. You needed some very special conditions. So we were able to show that in a very early galaxy, before you form any space stars in this particular galaxy, there's a setting where this would work. So you'd have a galaxy that has formed its first stars, but it has a little gassy satellite that's moving around. And in this gassy satellite, you don't form stars yet. Instead, you have a lot of gas. So that would settle in because the gas has some spin, some angular momentum.

It would settle down into a disk. And that this disk could then be made unstable by phenomena that are available, some departure in symmetry from spherical symmetry, which is expected. And then the whole thing would go unstable, kind of pulls on itself. And then, you know, and I think the analogy that works really nice and, you know, up to a point is when you pull the plug out of a bathtub and you see that vortex of material, water, going really fast, something like that, akin to pulling the plug happens in the universe and all the gas can get siphoned in very rapidly right into the center. And this is really what we need to make a black hole.

In fact, we have some visuals just to give a sense. So if we begin, this is the more conventional. Yeah, so you have a star, you have a massive star that starts its life out, then goes supernova, and then leaves behind a black hole. And then it could only grow by sucking in nearby material, merging with another. And that mass, its birth mass, is exposed. You know, it's uncertain. We don't know the masses of the first stars yet. They could have been much more massive than stars that are forming today nearby. So we think maybe that could be the way to make a black hole seed. That's 50 times, maybe 100 times, but not, not 10,000 times.

And then the new idea, if you can take us through that, so you have this gas disk that is swirling around in the satellite galaxy and you have direct collapse and you are starting to form. So no star, no star yet, and just gas and you form a black hole. But because of the particular configuration, you kind of need a galaxy nearby that has already formed stars to make this happen, because ultimately this object is going to crash and merge into that parent galaxy. In fact, I think we have the next phase of that as well.

So the black hole is formed and then it can do what you're saying. Yeah, it inevitably actually crashes into the parent galaxy. Yep. And when it does so then it's. Then it produces transiently a very special type of galaxy. So this is what we actually unimaginatively at the time called an over massive black hole galaxy. And obg, where the mass of the black hole far exceeds the mass of the stars, which is the opposite of what we find in the nearby universe, for example, for the Milky Way. So the mass of the black hole in the Milky Way is 4 million times the mass of the sun and the mass of the stars around it in just the inner region, three orders of magnitude larger.

So the gravity of our galaxy, in the entire scheme of things, the black hole doesn't count as much except when you get right next to the center. And this would be different, this would be different. And so I think there's this nice visual that helps give a sense of the distinct timeline of formation, so help us understand what we're seeing here. So this is a sequence showing you if you formed a light seed and you formed this heavy seed from direct collapse, then at an epoch, say between 400 to 600 million years after the Big Bang.

Well, I mean, the magic of this epoch is James Webb Space Telescope can take us right back to then. So the James Webb Space Telescope could potentially. So that's what we predicted. So you're predicting that the lower sequence may have happened in the early universe and it would have yielded over what was the exact name? Obgyn. Obgyn. My brain keeps going YN afterwards words, but so never occurred to me. Yeah, but you get this overly large black hole galaxy. So this penultimate frame that you see in the sequence. Right. So that's the difference if this galaxy started life with a light black hole versus one that formed a direct collapse.

And that third, that's penultimate frame, the fourth frame, there is an epoch that is now accessible to us with James Webb. We wrote this paper with the specific predictions. The original idea is 2005, 2006. It took a long while for this problem to be computationally tractable, to demonstrate it can happen and that the conditions in the universe are available for this to happen. Then we predicted in 2017 what James Webb should see, that if James Webb happens to look back to this epic, say 400 to 600 million years after the Big Bang and nature does produce these objects, we should see this very peculiar object. And did you have like a particular spectral signature that you'd be looking for? Yeah, absolutely. So there was a clear cut signature between 1 and 3 microns, which is sort of in the infrared.

This is the window, wavelength window that James Webb opened up to us. New eyes into the universe in that range. So there's very clear cut signature. But one of the other important things is because this object, the obg, has an overmassive black hole in the center, it means that the light output that's coming from there would be dominated by the mass, the dying gasps of gas that are being pulled into the black hole instead of the starlight.

So that's a skewed kind of budget where the light's coming from. And that has a very special Signature. I see. And the signature is that it should also glow in the X rays. And these objects would be quite faint. This is from the accretion disk around the black hole, producing. I see. And so it should be seen both by James Webb and in the X ray. And so that naturally takes us to the question of looking, now that James Webb is up there. And this is something that you have begun to do. Yeah, Sono. We have very compelling evidence.

So with an X ray astronomer, collaborator and friend, Akosh Bogdan, once we knew that James Webb was going to be scanning a bit of the sky, an opportune piece of sky, because these objects, you would like nature's telescopes, these cluster lenses that magnify the distant universe and bring them into view, ideally, because these objects are far away. If you can get help, additional help from nature, that would be great. And so James Webb was looking behind those regions. I see. So we proposed to look at that same region in X rays as well. So Aakosh suggested putting in a proposal to get time on Chandra and to look, because the incontrovertible evidence was going to be a set of properties, including detection in the X ray. And so both of these devices would be useful to get corroborating evidence.

And what is really beautiful about this work is, in fact, to originally calibrate that lensing and the magnifying effect Hubble data was used. So this was using everything that's up there. Absolutely. And so we have some of the imagery that no doubt has gotten you extremely excited. So this is James Webb. And maybe walk us through. I think this is the. Not quite the closest image that we have. Yeah. So what you saw there was that large lens that was going to bring the background into view. Yes. And that is the object that little back. If we zoom in. I think you have. Yeah, I think we have even. We can. Yes. I know it looks really blobby and tiny, but it's real and it's there. And then you go back and look at the Chandra data. Yeah. So I think we have some of that, too.

So let's just take a look at this data. We can bring up the Chandra and in fact, we can also, I think, label it as well. Yeah. And so when you study the details and then you compare it to your prediction, how is that looking? Unbelievable. I think I remember distinctly when Aakash called me so. Cause the key thing was that it had to be detected in the X ray. So James Webb had seen that object. We had the sort of the spectral energy distribution of that object and the shape looked uncannily like what we had predicted, and it was at the right kind of distance. Remember, I kept saying that there's kind of an opportune sort of timeline where these kinds of transient objects have to exist. So it was in that window and it satisfied.

So there were two properties. One was X ray detection and how bright it would be in the X ray compared to James Webb. Okay. So again, it's the balance of energy. The balance of energy in the X ray versus the infrared. And. And so when I saw this image, you know, that you could do that calculation because it was detected to this date. This is the most distant black hole where we have detected X rays as well. X rays have always been the kind of. Sure. Fireproof of the existence of an accreting black hole. Yeah, absolutely.

And so how has the community responded? Is this controversial? Is it broadly accepted? Is this done deal? Yeah, well, I think it's pretty much done deal. When we published the paper last year, it was another detection threshold. We were at like 4.6-sigma and we didn't have the entire X ray data yet. So now we have it at hand and we've crossed five sigma. So it is real for sure. And I think the community has come around to. I think the skepticism was actually much earlier on when, as we saw historically. Right. A lot of the pushback is for the theoretical idea, but that started shifting already in, say, about seven, eight years ago, when we made this first concrete prediction of what should be seen.

I think it would be fair to say black hole seeding became a bandwagon. And now it's a very active area of research and everybody wants to get in on trying to. Okay, how do you understand. I know black hole seeding became a thing like when we first wrote our papers in direct collapse, people were kind of skeptical. They said, oh, it's a cute piece of physics and it works, but is it real? And so we come back to that same arc. Right. And so now that we have the evidence, I think what is super exciting about this is that this is, of course, established. And so what it really tells you is that nature makes black holes in multiple different ways, not just what we thought before.

Stars run out of nuclear fuel, they collapse and so forth. But you're saying there are just more ways of doing that? Yeah. And can there be other ways? Yes, absolutely. So I think another way that I am super excited and open to is the idea of primordial black holes. So you could have made these very tiny black Holes very, very early on in the universe, during the very early, just post inflation of the universe, and that they could have survived throughout these singularities in space time and sort of sit around, sit around till our universe becomes dominated by matter and then start growing. And maybe they could be seeds.

So this is a picture that I've investigated with others. It's a very active kind of question. But once again, with this other seeding, there has to be a very compelling piece of evidence showing that that is the origin part of the problem is once matter or anything goes into a black hole, there is no memory. So you see a black hole, you cannot extract any information about how it formed. Therefore, it is the relationship between the black hole and its environment, the galaxy that it's sitting in, configuration, its mass ratio with the stars, et cetera, those are the signatures that can tell you more about how the black hole forms.

Yeah, I mean. Cause one of the striking properties of black holes is that there's a way in which they are the most simple objects in the universe. You label them by their mass, their charge and their angular momentum, how much they're spinning. And any two pretty much modular subtleties that are still at the forefront of research, any two that agree on these properties, they're effectively indistinguishable as objects in their own right. And so to understand about them, you need to know the environment and the history by which they came. And hopefully that is imprinted in some wake of. Exactly.

And the evolution. Right. So we are now, we have, since we have snapshots of data from the universe throughout its age, we're able to track not the same object, obviously, but objects in different stages. We have these theories that now connect the evolution from the formation. Of course, the issue is whether there is a slightly different growth path that one formation scenario may give you compared to the other. So it's a totally active area of research, but I think for direct collapse, I think it would be fair to say that now we have incredibly compelling evidence, especially since it's now sort of five sigma beyond five sigma.

Well, that is an amazing story. Congratulations. It really is. Thank you very much. Thank you. And thank you so much for this conversation. Thank you, everybody. Priya Natarajan SA.

SCIENCE, TECHNOLOGY, INNOVATION, BLACK HOLES, ASTRONOMY, COSMIC EXPLORATION, WORLD SCIENCE FESTIVAL