Into the Impossible With Brian Keating - Dark Matter Doesn't Exist? With Mordehai "Moti" Milgrom (#253)

Episode Date: August 28, 2022

Mordehai "Moti" Milgrom is an Israeli physicist and the Isidor Rabi Professor Emeritus of Physics in the department of Particle Physics and Astrophysics at the Weizmann Institute in Rehovot, Israel. He received his B.Sc. degree from the Hebrew University of Jerusalem in 1966. Later he studied at the Weizmann Institute of Science and completed his doctorate in 1972. In 1981, he proposed Modified Newtonian dynamics (MOND) as an alternative to the dark matter and galaxy rotation curve problems. Milgrom suggests that Newton's Second Law be modified for very small accelerations. In the academic years 1980–1981 and 1985–1986 he was at the Institute for Advanced Study in Princeton. Before 1980 he worked primarily on high-energy astrophysics and became well-known for his kinematical model of the star system SS 43. Connect with me: 🏄‍♂️ Twitter: https://twitter.com/DrBrianKeating 📸 Instagram: https://instagram.com/DrBrianKeating  🔔 Subscribe https://www.youtube.com/DrBrianKeating?sub_confirmation=1 📝 Join my mailing list; just click here http://briankeating.com/list ✍️ Detailed Blog posts here: https://briankeating.com/blog.php 🎙️ Listen on audio-only platforms: https://briankeating.com/podcast   Join Shortform through my link Shortform.com/impossible and you’ll receive 5 days of unlimited access and an additional 20% discounted annual subscription! Subscribe to the Jordan Harbinger Show for amazing content from Apple’s best podcast of 2018! Can you do me a favor? Please leave a rating and review of my Podcast:  🎧 On Apple devices, click here, scroll down to the ratings and leave a 5 star rating and review The INTO THE IMPOSSIBLE Podcast. 🎙️On Spotify it’s here   🎧 On Audible it’s here Other ways to rate here: https://briankeating.com/podcast  Support the podcast on Patreon or become a Member on YouTube Learn more about your ad choices. Visit megaphone.fm/adchoices

Welcome everybody to another exciting episode of the Into the Impossible podcast featuring a legend, a famous legend, maybe some say an infamous legend in the field of cosmology and in particular, no pun intended, dark matter research and objections to dark matter and that's Dr. Mordecai Mughram Maiti Milgram of the Hayim Whitesman Institute in Rehovot Israel. He joined us in late in the afternoon evening, early evening in Israel while I was here in California. And he's really, as I say, a legend in cosmology because he has perhaps the most seriously taken

of all objections to dark matter as his modified Newtonian dynamics theory. The modified Newtonian dynamics does just that. It adjusts certain parameters, as Monty will describe in this video, in order to match the observations that astronomers have known about since the time of Vera Rubin, who, fun fact, was trained here at UC San Diego by none of other than my late great colleague Margaret Burbage

on how to do spectroscopy, and Margaret was doing rotation curves too, but she never really thought much of it and really didn't pursue it the same way Vera Rubin did. And you'll hear about other applications of Mond and challenges to Mond from audience questions, such as those from friends on Twitter, or on my YouTube community tab. So a reminder, you can always find out what I'm up to by going to one of those two locations, Dr. Brian Keating on YouTube and on Twitter. And occasionally on Instagram, but mostly not. And I also send up my newsletter, briankeating.com slash list. You can join that. You may be entered to win a little bit of space schmutt,

some dark matter from our cosmos, namely dust from a meteorite. See the website for more details. U.S. entries only, I'm afraid, it's too difficult to ship overseas and too expensive. But at any rate, we talked about many different things, including the famous bullet cluster, superfluid dark matter, popularized by none other than past guest and upcoming guests, Sabina Hassanfelder, look for her episode on her newest book, Existential Physics, coming soon. And we talked about his work with the relativistic version of Mondos, called Tebbes and other things

with Jacob Beckenstein, who was really the forerunner of Hawking's Hawking Radiation Ideas in the Black Hall Entropy theorem. So you'll hear a little bit about Jacob Beckenstein and more, including the future. And really what impressed me is his courage. We talk about chutzpah and he has a lot of it and it's healthy and it's good when used in moderation as much he does so sit back for now enjoy this ride into the impossible with a man who is told never to attempt the impossible but he did it anyway and you'll find out more about his courage later on this episode for now let's go deep into the darkest matters in the universe with muttie mordechai mordechai milgar let's go any sufficiently advanced technology is indistinguishable from magic

Open the pod bay doors, please help. Welcome, everyone, to a very special edition of The Into the Impossible podcast, featuring your Shirley, Dr. Brian Keening of the University of California, San Diego, where I am joined today, remotely joined from the Weitzman Institute, all the way in Israel, by a very, very legendary figure in the field of cosmology, and especially in the field of searching for dark matter, and potential alternatives to dark matter, and even alternatives to our theory of gravity.

And that's Professor Mordecai Malti Mildrum, who has known to many of you, but I will read his introduction at a later date as we go on throughout this conversation. But Mataay, Laila Tov, how are you? Latov, it's evening here, yeah, early in the morning at San Diego, I think. Yes, yes. So you might hear some of it.

kids getting ready to go to summer camp. So I was introduced to you many, many decades ago now. I mean, you're very, very famous in the field of cosmology. But most recently, by a mutual friend over Schilling, who was a guest on the podcast, I'll put a link to that summer up here, over there, I don't know, in the video. And then on audio, you'll be able to find it for his new book called The Elephant in the Universe, which is called Subtitle is 100-year Search for Dark Matter. and he mentions you. He actually mentions you in the very same paragraph almost as he mentions my late, great colleague, Professor Margaret Burbage, who was the mentor and friend to Vera Rubin.

And I want to start first by talking when Vera Rubin visited UC San Diego, where I am, she worked with Margaret, and Margaret actually taught her how to do rotation curve analysis. So I want to start with a little bit of history. the idea of modified Newtonian dynamics, Mond, what is it? And how did the idea come to you? So basically you may know, and the audience may know, that one of the most central questions puzzled in astronomy, in cosmology today, is what most of the universe is made of.

In very few words, what happens is when we study galaxies and we studied the motions of constituents in those galaxies, like the motion of stars and gas. And we use this motion to determine the gravitational pool of the whole galaxy on this constituent. We find that the gravitational pool is much stronger than one calculates, just taking the observed mass distribution in those galaxies, and calculating the gravitational force, using standard dynamics, which is COF Newton and also general relativity. In other words, there is a large discrepancy between the gravitational pool that is needed

to explain the motions of constituencies and systems of galaxies. The discrepancy between this and what the observed matter in those galaxies can supply in the way of gravity. Now, I took another fork at the time this was the late 1970s, early 80s, and with the proposal that the problem, the discrepancy that not result from the presence of yet undetected matter, but rather from the fact that we're not using correctly the laws of physics to calculate gravity. So that's an alternative would be you're using, let's say, Newtonian dynamics, which is a combination of the Neutonium. Newton's law of gravity and the law of inertia. You use this combination of laws to calculate how our stars should move in galaxies,

and they actually defy this is hard by moving much faster in the calculated. So, okay, maybe you are not using the right laws, or maybe these laws are correct, but only have a limited range of validity. But after all we know that they have been tested, successfully tested in the laboratory or in the solar system. So there are large phenomena that are well explained by this laws. But perhaps in galaxies and systems of galaxies and in the universe at large, this is not so. So that is essentially the main idea. Then you asked how it occurred to me.

So I hope to mention perhaps that, well, first of all, in my background, I did my PhD in particle physics, early 70s, and then I switched field to astrophysics. And initially, for several years, I worked in so-called high-energy astrophysics, having to do this explosive or cataclysmic phenomena, such as they called Newton stars, X-A-emitting stars, and so on. Towards the late 70s, I decided to switch fields. And I looked around and this issue of the discrepancy that I mentioned before, it just began to really

head in a very meaningful way, partly due to, of course, observation of Röh Rubein and Ragu, but also one should mention alongside with the contribution of Rubin that also works in the Netherlands using radio telescopes, not the optical telescopes, but the radio telescopes, who also measured the rotation of the science field, and the results of all of them showed quite clearly that this problem exists. So this stuck me as an interesting thing, a problem to start working on when I start to make this decision to switch fields. And I also happen to be going to be going to to be going to a sabbatical at the Institute for Advanced Studies in Princeton. And Princeton is the center of galaxy dynamics.

You might say that there still are, but there were quite a few world experts in galaxy dynamic. So my decision was just to go and spend this sabbatical year to study the field, prepare myself to embark on this issue now. To tell the tools from the beginning, I had a sort of a guiding idea. So I didn't just go deciding, okay, I'll walk on this field. But there was something about those rotations that struck me. Not at the same effect on others, but anyway, to me it appears quite interesting.

And there was that, well, let me just explain what the rotation curve is. So rotation is basically a measurement of the rotation of, you know that in this galaxy, starts in gas moving more or less circular motion, not exactly, but more or less circular, and they move in a disk and in a plane. So it's a curve that describes the measurement of the rotational speed of stars, let us say, or gas in a galaxy, as a function of the distance from the center. This would be very analogous to, say, telling us what is the rotational speed of the planets around the sun when you plot them against the distance from the sun, the values of the orbit.

And suddenly as you go further and further outside the galaxy, you expect this rotational velocity to go down these stages. Just as you find in the solar system that the rotation of speed of the planet becomes lower and lower as you go to the outer and out of planet. So the rotation of speed of Mercury, the highest in the world, then you go out of Venus, the Earth, Mars and so on. Rotations speed always decrease it. And people expected that to happen in galaxies as well, because you are going further outside in the galaxy. And the fact was that the measure velocity did not go down, they sort of remained flabish. They tended to, they went up at first, and then they didn't change much if you went out with the

and that the fact that the velocity still, stayed high and did not go down is the basis for the discrepancy, which I mentioned. So the calculated velocity was going down, the measured velocity was not going up, and just the difference was fixed a discrepancy, which, as I said, is standardly explained with that matter. But another thing, you know, I remember telling myself, okay, if it's due to dark matter, then that matter is there, you know, it would be more, it could be less, it could, density could, you know, change in different ways in different galaxy. Why should there be this apparently universal behavior that the rotation cap stays flat? Okay, it can happen, this dark matter might not,

does not conflict with that matter, but to me it was a question mark. And then I said to myself, well, maybe it's not that matter. Maybe there is some general law that dictates this that the rotation catch you safely. This is actually my guiding introduction to when I went to Princeton, in fact, I came a quote. was the idea which finally started my working on month, so only to work my stay there. So for the whole living in the need,

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starting at only 49 cents per square foot. So all you have to do is pick your perfect floor. Start your carpet project today at the Home Depot. How doers get more done. Exclusions apply for licenses seehomdeeper.com slash license numbers. Learning about galaxies and the behavior, but always with a view to finding perhaps some underlying modification of the laws of physics that would give rise to this behavior. And oftentimes when I give a, when I have a guest on to talk about, say dark matter or even specifically talking about beer reuben in particular, I get emails from

her estate or sorry, from Zwicki's relatives. So I get emails from or text messages or or comments on my videos saying that Vera Rubin, you know, it was not involved. It really wasn't her discovery. It was all my father, Zwicki. And I wonder, you, you talk. obviously, you've been speaking mostly about rotation curves, but in the early days, the earliest days, of course, Wiki was, of course, the person who coined the term in German, at least, I think Govert convinced me that it was actually a Dutch physicist Captan who coined it in English for some reason, and then Orte, etc. But why start with rotation curves? Why not start as Wiki did with the dynamics of clusters, which are also the kind of most massive,

bound gravitational objects in the universe. Why start with galaxy rotation curves instead of clusters, as Wiki did? So the apology for this should not be mine. It was the blame of the whole community. What happened in the set is, Tricky indeed pointed out to this satisfaction at least, that again, the galaxies that are the constituents of clusters of galaxies, also, not also, but move with the velocity is higher than expected. When expected means that what you calculate, this is an elliptical galaxy, but there is also a transparency of cluster of galaxies somewhere.

Yeah. Okay, so that's an elliptical galaxy. It's not a cluster. Right. But at any rate, so Riki pointed out that, yeah, the velocity is of, galaxies in clusters are much too high to be explained by the pool of the computational pool produced just by the observed metering those clusters.

And then he says, okay, to explain this, he also invoked dark net. But what happened to this idea between the 30s and, let's say, mid to late 70s, it just disappeared and nobody talked about it. You can only speculate about the reason. But I suspect that people just heard that the system were not understood so well so as to actually inferred. So, you know, it happened many times in Astrophysics. That some measurements are misinterpreted, incorrect, or maybe they are just appeared to them too bold. unjustified.

Anyway, whatever there is it was forgotten. I never had never heard about it. And in addition, I think the rotation girls really brought on the problem to the community in much sharper

terms because rotation kits are more accurately measured. So I just say one thing, you know, in clusters, okay, what we can measure are just one component of the velocity galaxies in the cluster.

We use Doppler effect to measure velocities, and that gives you only the component of the velocity along the line of side. Right. But to actually determine the gravitational pool and an object, you need its orbit. It's not enough to have it. It's, you know, one component of its velocity.

And you didn't have that in clusters. But in rotation clusters, Yes, you do because you know that the motion in Turkey and by looking at the electricity of the galaxy on the sky, you can tell what its inclination is to the line of side. So you can translate just this measured one component of the velocity to the full orbit. So in the case of rotation curves you actually do have the full orbit and it tells you exactly, or at least to higher, and my much higher, I like to see what, they actually got attention to me.

So that may have been part of why people may have said, okay, you know, maybe the components of the velocity in other directions. No, no. So it didn't bring the issue. But maybe also the, you know, the time was more right for this, there were more people interested in galaxy dynamics,

in the community and so also. It tells on more deceptive ground. So again, going back to how I came to have you on the podcast today, we go to the book by Govert Schilling, who features

you extensively throughout it. And again, this is coming into the work that is really kind of uniquely identified with you, I would say, which is this modification. And what he talks about, he says, I came across the work of Mordecai Milgram, probably in the 1988 book, Dark Matter by Wallace and Karen. Here was someone with a fresh take on a nagging cosmic mystery. While astronomers were becoming

convinced that flat rotation curves of galaxies and the dynamics of clusters could only be explained by assuming that the universe was dominated by dark matter, Milgram took another approach. He tried to change the laws of physics. Now, here was something. heroic. So first of all, besides the fact that you're a Sabra, what gave you the chutzpah to not only take on, you know, changing the laws of physics, but take on Isaac Newton, you know, who's considered by many the father of modern physics, if not all of science. So what gave you that confidence to go, as I always like to ask, what gives you the confidence to go into the impossible, the namesake of this podcast.

How did you come to say, well, actually, it's going to be even more important to go and change the laws of physics? As to Hutspar, to tell that I didn't think at the time, at least as far as I remember myself, that it was such a Hutzpar.

In first, there's my background is from part of physics, and there people dare to explore less conventional ideas and you know, astrophysics let's face it in the more conservative feeling, I should say.

In a way, I say that people like art of the physics, physicists invent the tools then, astrophysists use them.

So we don't like the tools to be taken away from them. Anyway, whatever seems to me, that the community for species is more, or at least at the time, had been more conservative. But I didn't at the time actually

took a lot of courage to come up with it. I said, why not? I mean, there's this idea. Let's try. If it works, it works if it doesn't. We may come back to this issue later. I mean, I was sure that we failed a short time, but anyway.

And, you know, I was even sure that once I came out, the people would just jump on the violin and start working on it. And I was completely wrong, you know, in the mind. But at any rate, I guess that later on, when I already saw what the reaction of people did, it take more courage than just coming with it. Before I actually knew how people would react. But even then, I don't remember myself,

it's made or wanted by this objection. And I said from the beginning, I had some very good collaborators with the late Jacob Beckenstein. And, you know, it was enough that, you know, a person doesn't be too many friends. wanted to spend some enough for some and I had him and he expressed a lot of confidence in the idea so it was enough for me and after some time yeah I want to get to Jacob in a bit but

but first you know when I think about this the story my younger listeners may not be as familiar but there was a very famous episode in the history of astronomy where the same person came up with two different approaches to the problem of dark matter. And that was a person, a French mathematician, with a very strange first name, Urbain, and the last name, Le Verrier. Yeah. And he first was the one to take observations

and make a prediction that Neptune was causing the anomalous behavior of the orbit of Uranus, which was the farthest planet known at the time. Turns out that Galileo actually accidentally discovered Neptune, although he didn't realize it in some observations he made of Jupiter, just completely serendipitously, Neptune was there in the background, and he thought it was a star. But anyway, besides that, LeVarrier,

he hypothesized that there must be some unseen form of another planet. That is a form of dark matter that was previously unseen, that was causing the strange interaction, is tugging on the orbit of Uranus and the planet Uranus. And then he was proven right. He was actually observationally verified. And then maybe pushing his luck, he then went out and predicted the explanation of the strange peculiarity of Mercury's orbit, which was another planet that was behaving badly.

And he said, this technique worked well for me. So why don't I postulate dark matter is the explanation for Mercury. and he postulated the existence of an unseen planet called Vulcan. And so he was right, and then he was wrong. And I wonder, which do you think was a bigger, you know, was there a mistake or blunder? And then maybe you can explain what Einstein did to correct the error of Laverier and why that was so important. Well, those are only a very happy analogy with what is happening in this documenter, because you see emotions, unexplained motion of something,

in a system that is obviously governed by gravity. So in one case, the less daring, should we say, I quoted this of just some other body in the system that you don't see and contradicts the poverty did work. That was the first example you gave. In the other case, I wouldn't call it a mistake. I think it was the right approach, not just because it succeeded once, but because it was at the time the more straightforward explanation.

So it was not what it turned out to not to be the right explanation. You should judge something that's being a mistake or not by how things look at the time it was made. Not very clear. So anyway, so indeed. the planet Mercury also showed some very small now, an anomaly in its behavior. Again, when you calculated the effect of all the non-planet and of the Sun, of course, from the motion of Mercury, and it moved in almost expected way, but not quite. There was a very small anomaly, the region of the New Jersey.

And Einstein was working on general relativity a lot in order to explain, this anomaly, which was not the case in my case. I did suggest the alternative with the high motivation of explaining the way that method. But that's not the way he thought. Einstein had the theory of special relativity in 1905. A theory of gravity, the Italian gravity, does not obey the principles of special relativity. special element. For example, special Ravini says that there's nothing that can propagate faster than light.

And according to the theory of Newton, if you shake an object here, this is felt right away at any distance from that. So much means that the effect of gravity of changes in gravity in the mass that produced gravity propagating with infinite speed. does not agree with special activity. So one motivation to find a generalization of Newtonian gravity that will adhere to the principle of special relativity. Another motivation was to actually generalize with special relativity tells you that physics look the same in the system that

move respect to each other, but only if they move at a constant speed that special relativity is about essentially about systems moving at the constant speed with respect and especially tells you how the loss of physics look in the physics but as I wanted to generalize these two you know just general motions and and it turned out to answer both questions in one first swoop and that will be the introduction of the theory of general which of course takes its name from the fact that it is generalizing special relativity, but it is also not just this, it is also a relativistic theory of gravity.

So it is an extension, generalization of Newtonian gravity. And it does predict small departures from the calculation of Newtonian gravity even for planets. Now its effects are very small in the planetary system. system. General activity kicks in or departs from Newtonian dynamics when you're dealing with velocity that are near the speed of light or fraction, the fraction of the speed of life with planets in the solar motion.

So if they move it, so on the Earth moves it about in 10,000 speed of light. So anyway, but they still has a small effect, and it turned out which means it's the Mercury and normally about planet. You may have heard that people are now talking about planet nine. Yes. Yeah, we're searching for it with the Simon's Observatory and the ACTA, Common Cosmology Telescope is searching for. We can see it with microwaves because anything above absolute zero, of course, emits that. And then, yeah, we are looking for. planet nine, but it's in the opposite direction. It's not closer to the sun.

Yeah, but I'm just saying that it was also invoked to explain some anomalies in the motion of other things. That's right. Yes, and that's frequently what happens in science. In my channel, I talk about the scientific method as not really existing. There is no one scientific method. There's multiple approaches, and sometimes you serendipitously come across anomalies. And sometimes that's quite a fruitful way to proceed. And actually, that dovetails nicely into a question by one of my viewers and friends on Twitter. And that's a professor in the UK, Martin Bauer, who studies particle physics. But Martin asks, there are galaxies for which the rotation curves fit the barionic matter alone.

In other words, galaxies that have no dark matter. matter in them. And so he's asking me to ask you, how do such galaxies that only have ordinary baryonic matter, how do they fit in, in the context of Mond? So, first of all, I suppose, you know, Monde predicts that the discussion is should kick in only at acceleration below. We haven't discussed Mone and what it is and so yet because I didn't say what Monde is. Okay. Well, actually, why don't we start with that then, Morda Kuhlke, because we don't have, you have to go and you've been very generous with your time. It's getting later. So let's start with what is Monde, and then we'll get into what things are perplexing about Monde in particular,

or about a non-dark matter candidates such as these galaxies. So first of all, what is Monde, and then I'll show some of the slides that you sent. So the question, the question is, okay, If I said to try to modify the laws of Newton, let us say, so to explain the discrepancies without that matter, you have to take into account the fact that I've mentioned that these laws have been verified or tested successfully in the solar system and in the lab. So you need to ask yourself, I mean, what in the, what attribute of the system would daily that Newtonian gravity is still correct, okay, or when it is correct,

and when you have to replace it with something else. Okay, so in fact, my mission, also I looked for different system attributes that you could use to differentiate between the solar system, where Newton's loads of when and galaxies is when they don't. So after a long story, I pinpointed on the accelerations,

being the crucial property. So accelerations, accelerations in galaxy are many others of magnitude smaller than what you encounter in the solar system. So I sort of hinge this discrepancy on acceleration, introducing a new constant of nature with a dimension to acceleration. It's always happened, you know what, when we introduced some departure from physics, like quantum physics, it introduced a new constant, the Planck's constant. In a way, it is a marker, it marks the borderline between the validity domain of the old COE, that's called it the classical also in the new CIR. So in relativity, this is plagued by the speed of light, in quantum mechanics by Planckons, and Mon it is played by this acceleration post. So, in essence, says that as long as accelerations in the system are much larger than the same not, which is the case in the labort or in solar center.

Standard physics holds very accurately, Newtonian gravity and general activity. But when you go to much lower acceleration, there is a departure, and yes, this equation actually summarizes the departure. So I don't know if I should explain it, but it's one way of putting it. You see this mu there if you just ignore the whole thing with the mu of A or A-0. get f over n equals A, which is just Newton's second law, which is the force divided by massive the acceleration. Mon introduces this correction, which can be very large. And when the acceleration, A becomes much smaller than this A-0, which is the constant of one,

this new becomes much smaller than one, which means, right, which means that you need, well, okay, F here is the force calculated from Newton. Right. So given the force calculated by Newton, when A is much more than A0, this B, this sort of volt A, it becomes much larger than you would get from Newton. And that is how the discrepancies is removed.

It says that the same, you know, force, actually Monde tells you that the force is not about. Okay, so I'm now ready to try to answer the question. I was before, I think that what I just said is more or less enough. So of course, I don't think he means those galaxies, but there are galaxies or these regions in galaxies where the acceleration are still larger than anode. And then you don't expect to see to see that method. You don't expect to see any skeptics.

In the language of dark matter, those who believe in dark matter, you don't expect to see dark matter. But there have been claims in the, yeah, yeah, yeah. Okay. So my short answer is I just don't believe this. I can explain to you why in so many words, but... You don't believe that there's no dark matter, or you believe that the rotate, there's no... I believe that they're not even said the measurements, but the interpretation of the the measurements is just incorrect.

And you know, the popular literature tends to accentuate this claim. Because the more spectacular they are, the more interesting they are for the readers. Right. But there are also other papers that, you know, that explain by all this is not so. I mean, or it is that there are more likely interpretations of the same data that,

I can tell you just one, for example, okay? So what they measure, again, as I mentioned before, in the class of galaxy, are the one component of the velocity. Okay, so only the one along the line of side, which is measurable by Doppler shape. But in order to estimate the mass of these galaxies, they need the three-dimensional velocity. Now, they don't really know that the velocity is in the plane of the sky,

are larger than what they measure along the next. So, in some believe, this galaxy specifically is rotating, but with such an inclination, you know, it's more or less in the plane of the sky. You wouldn't know it. You will only reduce the mass just based on this one velocity. And in fact, there are claims in the future that this galaxy is rotating. There's no problem. You know, it's a mess.

but yeah the basic answer I just don't and many others I should say and there are papers about it I mean that actually there are much more mundane right in any other that matter but never mind that's not my okay and then there's a question that's occurred many times in the literature and then in my audience Tim John who's a friend of the show, listens to the show.

He's asking, can you share your view on why the bullet cluster is a challenge for Mond? And how can it be explained by Mond? So first of all, what is the bullet cluster? I'll show a picture of it on the screen. So the bullet cluster was not, so let me just like. So the bullet cluster is a cluster of actually a pale of clusters that they've underdone a collision. We see them just a few hundred, I think, million years after they, actually the centers went to each other. Here we see them on the sky.

What you see here is in the X-A picture. These two clusters contain gas, hot gas. This gas are more or less in Vennigand, X-A's. You can see that. And this map basically tells you where, much of the barons are. The barons are the standard metal. In clusters, it is known to be dominated by

the hot gas. So essentially, essentially, they tell you where the barons are. Now, you can also study this double cluster, the so-called weak gravitational lens

by using the distortion of the images of galaxies that are far behind in the background in the background behind this cluster. Right, so these are the two sort of bluish things. So the reddish things are what we just saw before. The x-A emission from the hot gas and this is where the hot gas. The bluish things are where the galaxy in the clusters are. Now, so the cluster just went to each other. Imagine yourself that the two clusters before they collided contain this gas and galaxies mixed together.

But once they collided, because the gas cloud essentially cannot very easily go to each other because they're sticking. So they stayed more or less near the center, but the clums of galaxy just went to. And you see them as this tool. So, however, from studies of the distortion of images of galaxies behind the scene, we can tell where the dark matter is. Okay, we can tell, we can match essentially the total matter in the system. And it turns out to be where the galaxies are.

Okay, so it's more what the bluish things. So the claim is the following. No, no, no, no, no. You say that, you know, according to Monde, the clay. According to Monde, you know, you should find the discrepancy, or you should find this phantom or putative dark matter where the variance are. Yes. But in this system, they seem to be not where most of the variance are,

which is the registries, but where the British things, but where the British So that was the proof of the existence of that people of dark. So the question, the answer, our Mon answers, types answers, is several. So first of all, the problem was not that we already knew from the 90s that Mon does not explain the way completely, the mass discrepancy in clusters. This is still a standing issue with Mons,

but even much before we put it clusters and in analysis, later we show whatever, there are several analysis that show that if you apply mon to cluster, so in individual clusters, not one that underwent collision, there's also a discrepancy. It's, let's say, a discrepancy of a factor of 10, let's say. So the visible matter is just a tense of what's needed to supply the graphic. Right.

So you need like nine times more dark matter than you have visible matter. If you apply more to this system, it reduces the discrepancy greatly, but it still leaves a discrepancy of the factor of two. So you would still need in these clusters, not speaking about the bullet now, just about isolated, the tens of intensive plaster. You would still need some components that we haven't discovered yet. So some people prefer to say that this is maybe sterile

neutrinos that can fall into plastics, but not into galaxies, because the famous argument, there are too light to fall into galaxy. But my own, my, look, okay, my own, My own explanation is that yes, clusters still contain some baryonic method that we haven't detected yet. It's not an issue at all,

because you only need as much as you already see. And it could be in a component that hasn't been discovered yet. It could be, I mean, that starts from certain population could be called a gas class. There are quite a few papers of this. And you know, you may know that there is also some what we call the missing variance. We think we think what, you know,

we think we know what the total number of values in the universe, you know, this of nuclear synthesis formation of the like elements and so. So we think 4% of the closure density of the universe is barriers, but where are they? I mean, a tally of variance that's known them today can account for roughly 50% of the balance.

Okay, so where are the, and all that you need to explain away the problem is just about 5% if you some of all clusters and all clusters you need in clusters you need about 5% of the violence it's a small function of the balance budget to do that so it could even I'm not saying that I know that this is the answer that it could be a mundane answer you would very much like no, it is still an issue, I consider it an issue, an open question in one, but one that at least can have a simple explanation. And I should say that, okay, if you now know if you take what you learned from single class, then the bullet class suggests the A's in the way that you expect.

This extra component has to be non-s sympathy for other reasons and so when the two classes both. to get collide the extra component should follow the galaxy, not the galaxy. But anyway, that's the explanation. So looking at other challenges to Mond, there are questions about other types of dark matter. You just brought up one type, you know, sterile neutrinos or axions. But I often point out there's a detection of dark matter, at least that's been claimed for over 22. years, and that's by the Dama experiment. And I wonder, can you give me your perspective on Dama? Is it a challenge? And just more generally speaking, if the liquid and noble gas detectors like

Xenon, which is co-run here at UC San Diego by my friend and colleague and past guest, Kaishuan Nii and friend and past guest, Alina Apreo. Are there challenges to Mond if Dama is to be taken seriously? Let's start by saying that suddenly dark matter is detected, then it is a challenge, not just the challenge. It's just to take the carpet. If there's dark matter, then there's no need to. Sorry, Madi, it's a little hard to hear you. What did you?

I'm saying that if dark matter is actually discovered, then certainly it's a challenge. If particulate dark matter is detected, right? Yeah, but Dama, I mean, you don't have to ask me, ask anyone else, even those who believe in that way. I don't think they actually believe in Dama. Well, A, as you may know, it conflicts, you know, by many others of magnitude with other experiments. Right.

There are also, as far as I know, similar experiments using the same type of detectors that claim that they haven't seen anything. And there are mundane explanations. But look, I'm not the right person to ask. I have absolutely no idea of what exactly could go home with Dharma, and I don't have a way to find. Yeah. But generally speaking, right, if there was a, in other words, is there no possibility that both flowers could bloom, both the dark matter in particulate form and a modification, or is it really one or the other?

Well, in principle, it can be. And as you know, I watch bits of your interview with Sabina, most infernal, which at some point is advocated or endorsed this idea, hybrid idea, which is not the first, it's the most famous one, because the people, involved a more vocal, large audience. But similar ideas that we suggested before, for example, Blanchez from Paris, suggested that the universe is just filled with the,

the polarization polarized the medium, such that on large scales it works at dark matter, and on small scales it reproduces norm. And so the fluid dark matter is conceptually a similar idea is that those galaxies in the universe at large is, again, it is a fluid that could be either in the standard phase, in which case it works at dark matter, in the sense that it acts by its gravitational weight, gravitational pool. but in galaxy that it can form a superfluid phase, and there it doesn't act mainly by its gravitational pool,

but rather it modifies the interaction between volumes, between star and so on, so as to reproduce the effects of mind. Now, these are hybrid models. I don't, I can't say that it cannot be, but I don't like them very much, of the for several.

But on a steady ground, you know, it's like the easiest way out. You see, you put together, you stick together two different things.

You know, if you already have one sort of outrageous idea, you know, you want, and you see it succeed in a large range of phenomena. Why not try to improve

it so it succeeds? When you put two such things together, you know, they, they tend to sale in the region where you stay. You said this place was steps from the water.

We just haven't found the steps yet. How much did we save? Enough. Enough to get lost. Or you could book a stay with Hilton. Welcome to your oceanfront room. Just steps from the water. The Hilton sale is on now.

Book on Hilton.com or the Hilton app and save up to 20% to get the stay you expected. When you want savings, not surprises. It matters where you stay. Hilton for this day. Okay, this one works still, the other one works there. What happened? And, you know, this is a common thing that appear.

I don't know, it's not very famous. At the time where there was a struggle, let's say, between the Ptolemaean geocentric picture, you know, everything goes around the earth, including the sun. and the Copernican system where everything goes, but at least the planets go around the sun. And then there seem to be advantages to differ to the two things. And so Tico Bae put a hybrid, suggested the hybrid.

Did you know about this? So I know he's very famous. But he said, okay, let's have all the planets. Let's go around the sun, except the Earth. the fan with all its entourage of planets go around the earth. Yes. So actually it has the benefits of the Copernican system, but at least as far as the parallaxes were not yet observed.

So, you know, parallaxes were the clinching arguments for the Copernican system that were actually, by the motion, it's the apparent motion of things on the sky. We know that it is the earth that those are the sun. But I mean, before that, it actually combined the benefits of the Pernican system with those of the, you know, the sun. You could still be okay with the Bible, right? The sun goes along the air, so it could stop it at Gibbon and, you know, as the Bible dictated. And it was okay for others. So it was a hybrid.

But we know, we know what happened. So, you know, I understand. You know, I don't like the hype, but it's the historically. they haven't proven to work. And it's a very superfluid idea. It isn't really doing very good. I mean, if it's been at the GFARC at the paper where they claimed it doesn't work for rotation cases.

Anyway. Right. Well, Monty, I know it's getting late there and you've been so gracious with your time and the audience questions answering all the audience. questions. I want to ask you one last question, which is pertinent to the name of the podcast, which comes from one of Sir Arthur C. Clark's famous laws. He actually had four of them, and they're controversial, what's the naming, what's the counting of them? But I want to ask you the one that's pertinent to the name of my podcast, which states the following. The only way

of determining the limits of the possible is to venture beyond them, into the impossible. So that's in the name of the podcast comes from. And I want to ask you, in the context that I ask all my guests who are so gracious like you are, I want to ask you, what gave you the courage as a 20-year-old or 30-year-old? If you can go back to your former self and give some advice, some life advice, what would you say to give the courage to go, as you've done, the chutzpah, into the impossible? Yes. Well, because the seem of possibility. impossible actually accompanies me along the way because so many times I've heard this is impossible this impossible with Monde I mean yeah they said okay fine one was for galaxies

but it would be impossible to explain light bending and gravitational lensing so it took 20 years but there was finally a lot of this theory that did get lensing correctly and then people say well but you can't get the CNB. It's impossible to get the CNB correction with more than just last year. There was, you know, created by Scholics and Glosnik, suggesting a relativistic morseille that does reproduce the CNB fluctuation. From the very beginning for me, this possible impossible. Like the following one, you know, when I started thinking about it,

I, well, I didn't think it would be impossible, but I was sure that the poor is very low that I will actually be able to modify the loss of you. Of course. I'm like everyone else. Not crazy. So I started, I had this idea, initial idea. I said to myself, well, I'm sure in a day or two, I'll just show that it is wrong. It's impossible.

I mean, it's highly unlikely, at least that's not possible. And then I work, because it impinges on so many phenomena, I'm sure I'll find some It didn't happen after a few days. I worked it out again and again. I invested more time and so on. And every time, things that initially looked impossible, which is highly impossible, turn out to be possible. And yeah, if it's any, of course, this way of argumentation

doesn't work. So in the individual, I don't know how good an idea is to just telling the impossible because chances are in any case if he looks impossible, it's probably at least improbable, so you know, maybe wasting your time. But as a community, certainly, I mean, some of us should try what looks like impossible. As well, we're not going to get beyond the boundaries. Right. Right. So for Indivis. So what is good as a general advice for the community,

the community should always send, or at least should accept such people, you know, with open, open mind, at least not give trouble when they're trying to do something like this, because it's very important for the community to explore beyond what it is. Absolutely. Very good. Well, Mati, Todarabha. I want to wish you, Lailatov. Thank you for coming on. Yes. Thank you very much. She has. Any sufficiently advanced technology is indistinguishable from magic. Well, that's a wrap. Thank you so much for joining us in this probe of all things that go dark in the night. We covered the history and challenges of Mond and challenges to Mon as well as the future.

And I hope you'll stay tuned. Hopefully we'll have him back on again. And it'll be quite a treat to have on people, as I often do, that have alternative views. I've done interviews with people like Anna EGis and Paul Steinhart. interviews with Giant Narla Kar, a proponent of the steady state or quasi-steady state theory, as opposed to the Big Bang Theory, the others, bouncing models, Neil Turok as well. So I'm not afraid, and you shouldn't be either, to probe alternates to the standard orthodoxy of cosmology, particle physics, and beyond. So I want to thank you all for tuning in.

Reminder, you want to see the video of this episode. If you're listening on Audio Only, please do check out my YouTube channel, Dr. Brian Keating. where I show some visuals from this episode. And that will help explain some of the lacunae, the gaps in your understanding, perhaps. And speaking of audio episodes only, I want to take this time to say thank you to those of you who have left reviews of the podcast recently. I just got one from Summon with the very catchy name Beef Stew, who says in his or her title, Interesting Science Sprinkled with Dad Jokes. Okay, that's kind of the vibe I'm going for. Not all the time. As I say, you know, I always have to have a quote of dad jokes. Actually, I didn't give one today. What's a dad joke for today? Let me think about one. Oh, yeah, how about this? Have you heard of the Black Hole diet? Yeah, that's right. You just eat light. Okay, so Beef Stew says Brian is incredibly smart. Thank you. And talk to some of the smartest people on the planet. He also has a seemingly endless supply of dad jokes that makes me smile and or groan. I'm sure you're all groaning, but I do hope you will leave a review just like,

like beef stew. If you're doing so on Apple Podcast, you can do it very easily, along with a rating. I'm trying to get to 500 reviews, and your review will help me. We're getting close, but we need your help. And it's really the only feedback that I ask for, other than joining my mailing list, Brian Keating.com slash list, where I have giveaways, including things like my recently produced dialogue on the two world systems by Galileo Galilei, which I read with Frank Wilczak, Fabiola Giannati, and Lucio Petirillo and Carlo Revelli and Jim Gates. You don't want to miss that. I give them away for free on occasion. I also give away space dust if you're here in the USA.

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And we will do it for many years to come with your home. So thank you very much for going into The Impossible with me, your truly, your pandemic podcast host, still recovering from the lingering effects of COVID on society, but we're going to get through this together. And thanking you for not being afraid to take an unorthodox view of guests, such as today's guest, Mordecai Milgram. Thank you so much and have a wonderful week until we meet again. Ambition comes in all shapes and sizes. At First Citizens Bank, we roll with your goals because we're built for what you're building. Fit for your ambition for Citizens Bank.