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Is there more to say about the “crisis in cosmology”? What are the fundamental disagreements? Is there any way out of this mess? Why am I talking about it again? I discuss these questions and more in today’s Ask a Spaceman!

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Hosted by Paul M. Sutter, astrophysicist and the one and only Agent to the Stars (http://www.pmsutter.com).

 

EPISODE TRANSCRIPTION (AUTO-GENERATED)

this episode of Ask a Spaceman is brought to you by my friends at better help. Better help provides easy, convenient, affordable access to online counseling and therapy. And, you know, the therapy has been an important part of my, uh, life experiences, something I'm absolutely not ashamed to talk about. I wish more people used therapists and counselors to take better care of their own mental health, just like they take of their physical health. Uh, I know a lot of you turn tune into this show for Astro Thera as a word, but maybe if you're having a really tough time, you should talk to an actual professional, and so I encourage you to go to better help. They are convenient and professional. It's real therapy and counseling, and it is affordable and you can connect online. You don't have to wait in a waiting room or any of that. You just talk to someone who who cares and and knows what they're talking about. As a listener, you'll get 10% off your first month by visiting better help at better help dot com slash spaceman, and I want you to join over 1 million people who have taken charge of their mental health again, that's better help.

HE LP dot com slash spaceman. I don't think I've ever done something like this before. I've revisited topics before to go into more detail or to focus on a slightly different angle. Oh, and there there was that one episode about falling into a black hole where I got something wrong about the Hori horizon, what you'd experience there. And so I redid that episode so that kind of counts. But as you know, I do not have a lot of notes in front of me. When I record, I sit in front of my microphone and I keep talking until I'm done talking. Thankfully, I have a wonderful editor shout out to Cathy, so I sound somewhat coherent. But anyway, a few weeks or months, when it's time anyway, Ago, I did an episode on the Age of the Universe and the current So-called crisis in cosmology. Originally, it was supposed to be an episode on how do we measure the age of of the universe. But somewhere in my note taking, the theme shifted and I went with it, and instead I focused on the crisis It felt good when I finished my notes.

It felt good when I recorded. It felt good when it went live, but as the days passed, it felt less and less good. I didn't like thinking about that episode something felt off or wrong or incomplete. There were things still left on the table that we hadn't picked up and eaten and digested and enjoyed. When it came to that topic. I don't think I did the topic justice. I don't think I told the complete story. I don't think I told the best story about the crisis in cosmology. I don't think it served you as best it could. I still believe that my conclusions at the end of the episode are valid. And for those of you who are entirely lost, I encourage you to go listen to Episode 154. Is there really a crisis in cosmology? The crisis in cosmology is also known as the Hubble tension, which is why I focused on in that episode what I'm going to refocus on in this episode. Basically different measures of cosmology of this very important number, the Hubble parameter, which is the present day expansion rate of the universe, different measurements are giving different results, and we have no idea what's going on.

That's the short version. If you just want to stop there and then move on to the next episode, that's fine, because really, that's as far as this episode is gonna get. We're just gonna flush it out a little. But anyway, my conclusions the last time I talked about this or that this crisis is largely manufactured. That's a big deal because cosmologists have nothing else to talk about. They have nothing better to do than to keep engaging in this crisis. My conclusions that were that we don't understand supernova measurements as well as we insist that we do, and that the most likely resolution of the crisis will be more data and better understanding of the data rather than a revolution in physics. That's still my conclusion. That's where I'm gonna head in today's episode. But but there's more to the story a lot more so let's reload, restock and revisit the crisis in cosmology and see what surprises the universe has in store for us. In the first visit to the crisis in cosmology, this would be the loaded version rather than the Reloaded version.

I talked a lot about models model, this model, that mathematical models of the universe about model components and how they interact, uh, and and how parts of a model can can describe the evolution of a system, et cetera, et cetera. I talked about the model of the universe, but I didn't really dig into that model very much to tell you what that model was. This model has a horrible name, and maybe that's why I was unconsciously avoiding it because it such a just a blah, blah, blah, blah name. Like even the media doesn't want to use the name. And you know the media love jargon. They will attach themselves to jargon. They will use jargon more than you think, but even they avoid the name of this model, so they will call it. I'll see sometimes the standard cosmological model. But I'm old enough. There's a real cosmological standard model, and then this new model overturned it way back in 1998. 0, boy, back in my day, Yeah, there there was a standard cosmological model.

It turned out to be wrong, and it was replaced by this model, but I guess this model has been around for like 20 years, So it gets to be the standard cosmological model now, even though it's not. Anyway. The, uh, my eyelid twitches every time I see the phrase standard cosmological model because I'm like No, it's not. It's back in the in any way. The name of the model is Lambda CD M. That's right, the Greek letter lambda, followed by CD M. That's the name of the the standard cosmological model. Lambda stands for dark energy. It's the Greek letter that cosmologists used to represent dark energy, and then CD M stands for cold, dark matter. These are the two primary ingredients in the model. His model assumes that there's a thing called dark energy, and there's a thing called Cold Dark Matter and you put them together. You get lambda CD M. Sometimes people are can't find the Greek letter lambda on their keyboard, and so you'll see it written as L CD M. I usually do that because I'm super lazy when I'm typing about it.

But there it is lambda cum. That is the cosmological model that we are discussing. That is the focus of the crisis in cosmology. And to its credit, Lambda CD M is a relatively simple mathematical model. It it and what it does is it relates the contents of the universe to its evolution. And like any model, it makes assumptions. Any scientific model you will ever encounter has a base list of assumptions. The assumptions that go into Lambda CD M are that general relativity is the correct at large scales, it is the correct description of gravity. It assumes that the universe is homogenous and isotropic is pretty much the same. Once you get to big enough scales, it assumes that dark matter exists and really only plays around with gravity. Doesn't really interact with normal matter. It assumes that dark energy is also a thing is also a constant, has constant density so that you get more dark energy as the universe expands. It assumes that the universe is flat, uh, et cetera, et cetera.

Now, like any scientific model, any assumption we don't just test our models. We also test our assumptions. These assumptions don't exist just to make our life easy or to be convenient or to just start guessing these are motivated by observations. We have observations that the universe is flat. We have observations that there is this thing called dark energy. We have observations that there is some some kind of ma that doesn't interact with light. Uh, as far as we can tell, general relativity is correct, even though we've spent over 100 years trying to prove it wrong, et cetera, et cetera. So you get the idea. We've tested our assumptions, they go into the model, and the model has some unknowns. The Lambda CIA model has six unknowns, six adjustable parameters, six little variables in the model that you don't know ahead of time. For example, you need to go out and figure out you need to actually measure, say, the amount of dark matter. The Lambda CD M model assumes that dark matter exists and has these properties.

But it doesn't tell you how much you gotta measure that. Uh, you need to measure the amount of regular matter you need to measure the age of the universe and and a few other well, exactly three other parameters go in. Once you go out and measure those numbers, once you go out and actually discover those through observations, you can plug them into the Lambda CD M model and you let it fly. It's a relatively simple equation, especially as physics equations go and the model tells you everything else you need to know. And and that's crazy. Like Like think about this. Like once you go out and measure six things. I mean, if I told you if I walked up to you on the street and say, Hey, hey, hey, buddy, Listen, if you measure six things and only six things, you will be able to have a complete and accurate history of the entire universe. You would say I'm nuts. You probably still say I'm nuts, even though I'm explaining it in more detail and and we've known each other for a while.

But that's so cool, isn't it? You can measure six things. Six unknowns. Once you make them known through observations, then you know everything else. There is to know about the universe about cosmology. You are done. This model is awesome. It is encapsulating 13 and change billion years of cosmic history in the evolution of all its contents with six numbers. And once you get those six, you know everything else there is to know about the universe. Like, say, the present day rate of expansion a K A the Hubble constant. Now, one of the most awesome slash frustrating things about cosmology is that we have multiple probes. We have different ways of getting those six numbers On the plus side, the awesome side is that you can have multiple probes of the same number, so you can cross check like you can go out and do this observation. And you you pin down one of those Lambda CD M numbers and then you go do this observation.

You pin down the same number and they should agree, so you can cross check each other. Another plus is that you can have patreon. Yes, this model Lambda CD M supports the existence of patreon in exactly the same way that the existence of patreon supports this show. Patreon dot com slash PM Sutter Now on the minus side, on the minus side, the frustrating side is that no one single probe gives all the info. So you need to combine measurements. You have to combine measurements. There's no one single observation that you can use to get all six numbers in the Lambda CD M model and just be done with it. So you have to go out in the universe and you have to be clever and you have to try different things. And don't worry. I'm gonna describe those different things in a little bit. To give you an example of this. Another name for Lambda CD M for this model, which I like way better is called concordance cosmology. Because back in the late nineties, multiple probes lined up in the same way to give complimentary results that led to this overall picture.

So I like the concordance model better than the standard model. Can we Can we just start doing that? Can I get on the evening news? Can I can I take out an ad in the Wall Street Journal or something? Anyway, Another minus is that no single probe or measurement spans all of cosmic time. Usually it's just snapshots or a small window like you get a little observation here in the nearby universe. Maybe you use one kind of measurement to get something from 5 billion years ago. Maybe you use a different kind of measurement to get something from 13 billion years ago. You get these little snapshots, and so you need to assume this is another assumption of the model that it holds throughout the course of cosmic time, that the same model that you use at time A is the same model that you use at time. B. That is an assumption, and it's something we're we're currently wrestling with. Like I mentioned in the previous, regularly loaded episode, this kind of modeling work is pretty much the bread and butter or meat and potatoes. Choose your food based analogy, your cheese and crackers of every field of science.

There is nothing especially weird or new or smelly or off about the Lambda CD, M or concordance model. It's like any other model in science, folks. You have some assumptions. You have some unknowns, you observation and get those unknowns so that become they become knowns. And then your model tells you everything else you need to know. There's nothing special about it, except for the fact that it's not working. But hey, wait, wait, Let me let me take a step back. It works. The Lambda CD M model would not have stuck around for 20 years if it wasn't working at at least some level, All right, we're not adopting this model. We're not using this model because, like we love models and we get fascinated by certain No, no, no, it's because it's observational constrained. The Lambda CD M model is ridiculously successful, with six numbers pinned down. We get stunning agreement with observations we can mimic. We can fold in like galaxy evolution structure formation, the for the the abundance of elements, all the stuff we can get.

But there is this one tension point over the Hubble constant. But the reason that cosmologists are so focused on this crisis in cosmology is because the Lambda CD M model is almost too good. It's so damn good that if you're a professional cosmologist, that's the only thing to talk about. It's the only thing to write papers about. It's the only thing to get grants about The crisis in cosmology is the only interesting thing to happen in cosmology since the discovery of dark energy over 20 years ago. We focus scientists focus on the cracks on the shortcomings on the weaknesses of a model because that's where we learn. That's where new knowledge happens is by focusing by you finding a weak spot in a model and putting some pressure on it and seeing if it breaks. And when it breaks, you get to learn something new about the universe. So that's why there's so much focus on this because we've been bashing our heads about dark matter and dark energy for decades now, and we haven't made a lot of progress in those areas.

Yes, the the Lambda CD M model assumes that dark matter and dark energy exist then that they have a certain set of properties. We have no idea what dark matter is. We have no idea what dark energy really is. We just know that they have these properties and we can use that in this big cosmological model. We wish we knew what dark matter and dark energy were, but we don't and so that's a bummer. But now there's this crisis, this Hubble tension, this disagreement about the present day expansion rate, and so we're wondering if we being cosmologists. We're wondering if this is nature trying to tell us something. If this is a crack in the Lambda CD M model and if you can fix the crack. If you can find a solution, you might learn about dark matter or dark energy or general relativity or one of the assumptions or anything. Maybe we're about to learn something. Hence the fascination. But let me talk about these probes and and No, I don't know why cosmologists use the word probe all the time.

Ever since I first encountered this, I'm like did did did any of you not pay attention to popular culture And that that probe the word probe in astronomical context is usually associated with something else, Something very unpleasant. So I don't. Anyway, it's just the way it is. You in the back. Stop giggling, OK? This is serious science. The N A These probes these measurements are like eyewitnesses to a crime. OK, we've got these six unknowns. We've got these six variables that we're trying to fill in. We've got these six ways of describing us of There's been a murder and there's a suspect, and we want to know how tall the murderer is. How, uh, how big they are, what clothes they are wearing. Like, you know, here are six things that we can use to identify the murderer. And so we're gonna go out and ask some eyewitnesses to describe the murderer. And we're gonna get we We we want is all these eyewitnesses to agree on the same description of the murderer so that we can put the murderer in jail.

There are generally two general classes of eyewitnesses, slash measurements slash probes, early universe and late universe, the early universe. This is stuff happening at big scales at the early universe that we go and measure the the prototypical one, the the one I personally am a big fan of because I was a part of researching. This is the cosmic microwave background. This is the leftover light released when the universe was just 380,000 years old. A transition from being a plasma to a transparent gas. That light has been soaking the universe ever since, and some of it is hitting our microwave antenna so we can build quite literally, a baby picture of the universe from when it was just 380,000 years old. This is a gold mine of cosmological information because all the ingredients, like dark matter, normal matter age of the universe. You know, all the a bunch of these unknowns that we're trying to pin down played a role in the physics of generating the CMB and the CMB.

The those physics are actually pretty easy to model because, you know, we have a pretty good handle on plasma physics. We've been doing it for a while, pat ourselves on the back here, and so we can put these gradients in. We can play around, we can see. Oh, if I increase the amount of dark matter, how will that affect this light pattern coming from the cosmic microwave background? You can actually calculate that, but it's pretty straightforward calculations. And so using that map, what you actually have, you can say, Oh, there's actually this much dark matter because if there was a different amount of dark matter, it would throw this this observation off. So that's that's a gold mine, right? Right there. Another thing we have is big bang nucleosynthesis. This is our understanding of nuclear physics. When our universe was about a dozen minutes old, this is where we get all the hydrogen. This is when all the helium or most of the helium was formed This is when a little bit of lithium was formed. But, you know, between you and me, who cares about lithium, And we can go then and compare to observations. So if you start monkeying around with the physics of the universe when it was about to dozen minutes old, you get different amounts of hydrogen, different amounts of helium in the universe.

And so you compare that to observations and you get to learn about the ingredients of the universe. You get to fill in some of these free parameters these unknowns, this eyewitness description in the model in lamb to CD, M and concordance cosmology. Another thing is called BAO has un related to BO very, very unrelated to BOBAO. Make sure you say it carefully. That's Barry on acoustic oscillations. This is more physics happening in the early universe. When the universe was a plasma before the whole CMB thing, when it was younger than 380,000 years old, there were sound waves. It was a plasma. There are sound waves. So they were. There were literal giant sound waves crashing around the universe. I gotta do an episode of BAO someone please ask And then the CMB happened. The universe went transparent and the sound waves got like locked in because now there wasn't a plasma anymore. And, you know, sound waves are density waves. So there's regions of higher density regions of lower density. Those got locked in.

They go, they got frozen in, and then you fast forward. A few billion years and the places that were slightly higher density now have slightly more Galaxies in that position, relative to other other places. Super cool, right? These are called Baron acoustic oscillations, and there's there's many others in the early universe and and then we can turn to, like late universe probes or nearby universe probes. And you have things like the SES. The seid are this kind of pulsating star that you can know its true brightness. And you can compare its actual brightness on the sky to its true bright or the measured brightness to its true brightness. And it allows you to get a distance to it. Same thing for type one a supernova. You see a distant galaxy, a type one, a supernova goes off. You know how bright that supernova is supposed to be. You can compare that to how bright it looks. You do a little bit of trigonometry, you can get a distance and then you can measure the red shift. So you know how fast that galaxy is receding away from us.

There are other things. These are generally called standard candles and by far the vast majority of late universe. Local probes rely on this technique called standard candles, where you just know the true brightness of some object. And then you can use that to calculate a distance. Why do you want to calculate a distance? Because you want to build up a diagram relating the distance to an object to how fast it's receding away from us. That diagram, called the Hubble Diagram, is a key ingredient of the Lambda CD M model. So the Lambda CD M model tells you what that expansion rate ought to be in our nearby universe. It tells you how the universe ought to evolve and behave, and then you can use these probes like the SES and the type one A supernova, and they're more they are mirror variables. They're tip of the red giant branch. Uh, they are lensing time delays. Many many, many, many others that go out and tell you exactly what that expansion rate is as a function of distance as a function of time.

So we have one set of observations that help us fill in the Lambda CD M model one set of eyewitnesses that help us fill in those numbers in the Lambda CD M model. Then the Lambda CD M model. Once you fill those in, you turn the crank. It says, Well, here is your ex rate as a function of time. This is just what it is because I'm the Lambda CD M model and I'm in charge. Then you can go to all these other probes like the PhDs, the type one a S, the tip of the red giant branch. The lensing time delays the mirror variables. If you want more details on any of these happy to do the episode. Just ask, and you can actually go out and measure what that expansion rate is today. So this gives you a very easy way to test the Lambda CD M model. It gives you a way to test the eyewitness account. So you go talk to your eyewitnesses and they and you get a picture of the suspect and all the eyewitnesses say all the eyewitnesses agree that the suspect lived next door to the person who was murdered.

Everyone goes like Oh, yeah, yeah, yeah, they came out there or they I heard them knocking. And so yeah, yeah, yeah. All the eyewitnesses say that you feed that into your model your lamb to CD M you're like, Hm, I think this person lived next door. Now you go out and test that you actually go and you knock on that door and you see if the person that answers the door matches the description that the eyewitnesses gave you They're 6 ft one and around £200 or wear a red baseball cap. I. I don't know who that. Maybe that's maybe that's big bang nucleosynthesis talking right there. I don't know. And then you go, you you search the apartment, you search that that house or whatever and you look for a red baseball cap and you look for a person that's 6 ft one and £200. You test the model based on what the eyewitnesses give you. The eyewitnesses give you the model Now you have your suspect, the local expansion rate. Then you actually go out and measure the local expansion rate. The last time I framed the crisis in cosmology, I framed it as CMB versus Supernova.

But that wasn't the whole picture. Really. It's early universe versus late universe. When we combine a bunch of early universe probes say, CMB bar on acoustic oscillation, big bang nucleosynthesis and really any combination you desire of early universe probes of probes of the early universe. As long as you can fill in all six numbers with some degree of confidence, you get your Lambda CD M model. You get your suspect description, you pin down the entire evolution of the universe. Boom, you're done. Then when we go out and do any combination of late universe probes of nearby universe probes seid, type one, a supernova red giant, whatever. And we actually measure the Hubble constant the present day expansion rate. We get a different number. So we have a couple different tensions or a couple of different ways to frame the tension. It's not just cosmic microwave background versus supernova. It's late universe versus early universe. It's using the Lambda CD M model to inform our present day our knowledge of the present day universe versus measuring the properties of our present day universe.

It is large scale versus small scale when we go out in that early universe, you know, imagine imagine. I like to imagine we're living at the bottom of a funnel when we're doing cosmological observations. When you do local observations, local measurements, you're constrained to just the very, very tip of the funnel. There's not a lot of volume there nearby us. You know, if we go out to like the distance of the the Andromeda Galaxy, there's not a lot of Galaxies within that radius. We can't do a lot of cosmological measurements. There's not a lot of information, but if we go back further out, we have a bigger sphere in that bigger sphere, like the wider part of the funnel. There's more data to collect, and everything operating there is at larger scales. So the further out we go in space, the further back we go in time and then also the more volume we're able to get. So this is a disagreement between large scale measurements and small scale measurements. It's a disagreement between very, very, very, very far away measurements and not so far away measurements.

It's a disagreement between early universe measurements and late universe measurements. It's a disagreement between model dependent observations and predictions and more local measurements. The essential crisis is this. Whatever combination of early universe probes you use to fill in the Lambda CD M model once you get those six numbers, once you get your eyewitness sketch description done, you get an expansion rate of around 68 kilometers per mega parsec of our present day expansion rate. However, using whatever combination of late universe local measurements you want, we get a higher number. We have 74 kilometers per second per mega per se. That's less than a 10% difference, folks. Which is a huge testament to modern cosmology. I mean, come on, we're only measuring the entire universe here, and we're getting things right to around 10%. That's I mean, come on, slow clap right there for doing that.

Cosmologist, you know, only took us 100 years, but we got there, but and this is the crisis. The uncertainties on those numbers or the claimed uncertainties are on on those numbers are only around 2% so it's a 10% difference. But each number is only willing to wiggle, plus or minus 2%. That's too big of a difference. They shouldn't be that different from each other. There is a complicating factor here. A small number of techniques, like tip of the Red Giant branch, give a number for the Hubble constant, the Present-day expansion rate of the universe right smack in between those two extremes. So it's it's it's hard to say. It's hard to say or I should say, it's hard to say how, how useful or interesting that number is. We don't know if that's telling us something weird or if there's just something really funky about that measurement. If we go back to our eyewitness murder scene analogy that I am making up on the fly as usual, it's like if you interviewed a bunch of eyewitnesses and they were eyewitnesses and they don't know each other, and they all give the exact same description exact same description, and everyone agrees that the murder suspect is 6 ft tall.

Just everybody and you find, and they also agree about everything else, and you find someone the next door neighbor who matches the description perfectly but is only 5 ft tall. Something's off. Everything is agreeing. Except this one thing. This first cropped up back in 2014, when the plank satellite released its first results of the cosmic microwave background. It produced a value for the Hubble constant, the present-day expansion rate of the universe that was lower than what supernova measurements at the time had were reporting. That was 2014. It hasn't gone away since. So the best way to summarize this situation would be a lot of bickering. People criticizing the plank results, people criticizing the supernova results, people throwing shade on each other. Like, If I mean, if you knew how to do science, then I don't think this would be a problem. People saying everybody is wrong and ideas. So many ideas.

Check this out. There are over 300 published proposals for solutions to this crisis. 300. There are 300 separate ideas out there for how to resolve this crisis, because it's interesting because nothing else between, you know, ever since dark energy was discovered and we knew it, it existed Between that and 2014 basically nothing happened in cosmology. We didn't learn about dark matter. We didn't learn about dark energy. But then, beginning in 2014, something happened. The Lambda CD M model was falling up short, or we were seriously misunderstanding local measurements of our universe of the expansion rate or both. Or neither. There's four broad categories of solutions. One is solutions that try to change the physics of the early universe, you know, change the physics so that the Lambda CD M model doesn't fully apply at the time that the cosmic microwave background was generated, If you just change what the model assumes, maybe there's some form of dark energy that was playing around when our universe was young and then it went away.

Maybe there's more new trio flavors that are playing. Or maybe there are new forces of nature, you know, just whatever. So that you change the physics of the cosmic microwave background. You change your lambda CD M model by adding those new ingredients in, and then what you get out of the end of it is a higher present day expansion rate of universe. Because your model has changed. You're you're monkeying around with the model. However, these run into a lot of challenges because they often break late universe measurements like you can get a different Hubble constant. Yay! But then you really mess up how, like Galaxies form or something which is not so great. Another category is to to change the physics of the late universe. You know, we assume that the Lambda CD M model, uh, worked at the CMB and also works today. But maybe something's changed in the meantime, I mean, it hasn't been 13 billion years, so maybe dark energy is doing something funky in the past few billion years. But these models often don't work because that makes it hard to connect back to the cosmic microwave background.

It's hard to have physics that operate now. That didn't operate back then. And once you monkey around enough, I mean, they they break a lot of the relationships. Even though you get the correct Hubble constant today, we have measurements of the expansion rate going back a few billion years, and so it's hard to match those observations while getting a new present day expansion rate. It's hard to fit the whole few few billion years that we have observations, measurements of the expansion rate. Another broad category is maybe maybe we're getting physics wrong. Maybe general relativity is incorrect. These these are not having a good time of it could be, especially because of those kill and Nova results that I talked about a few episodes ago that just totally killed the vast majority of modified theories of gravity. And so it's really, really hard to develop a new theory of gravity that passes experimental muster and can explain things like the Hubble tension.

That's that's have fun with that. And then the last category is maybe we're misunderstanding something about our observations. It's unlikely to be just cosmic microwave background related, though, because you still get the attention. If, if we had zero observations of the cosmic microwave background and we just had Big Bang Nucleosynthesis and Barry on acoustic oscillations, we would still have the tension because that's enough to fill in the lamb to CD M model. So it's it seems, unrelated to just one particular probe because what matters is, as long as you get enough information to fill in the lamb to CD M model, you get the tension, and it's unlikely to be just supernova relayed. We could have absolutely no supernova measurements whatsoever. But we have enough other measurements of of the present day expansion rate the Hubble constant through things like mirror variables that the tension still exists. So it's unlikely to be one particular observation because it doesn't matter how you combine it or what probes you use you. The tension still persists. As of the recording of this episode, there is no agreed upon solution to the Hubble tension.

And indeed, there is no physics solution that matches all the available evidence. You fix one thing, you break another, you go to fix that, you break something else, you go to fix that and you end up breaking the first thing again. You just get caught. The earth are caught in this endless cycle. It's It's like playing whack a mole with the universe like oh, Hubble tension. I'm gonna whack that problem. 00, now you can't explain Galaxy firm. Oh, OK, whack that. Oh, now you can't explain. Uh, cosmic microwave background fluc. OK, whack that. Oh, now your abundance of light elements. OK, whack that and you're just constantly going around. Nobody has a solution as it was last time. My inkling is that if it's interesting, it's probably wrong. I, I suspect. And this is my personal suspicion that local measurements may not be as reliable as we think they are. In other words, I think it may be much more difficult to measure the Hubble constant in the local universe than we are leading ourselves to believe. But it's not just supernova or mirror variables here. I think it might be hard to measure the Hubble constant to the degree of certainty that we think we can do it.

That's my inkling. That's my inkling. I haven't written any papers about this, but everyone's, But that's so boring. Everyone's so excited by by new models by new physics, the crisis in cosmology might lead us to a better understanding of how the universe works because something is going off. If all these observations are accurate and as accurate as we think they are, then Lambda CD M concordant cosmology has to change. There has to be new ingredients, or there has to be new physics and don't get me wrong. It would be really cool if we learned something about dark energy or dark matter or the early universe through this crisis. But I'm not getting my hopes up, but that's just me. Either way, we're gonna learn something either. We learn something about physics. We learn something about the universe. We learn something about how to make cosmological observations, no matter what. The crisis in cosmology will make us better. And maybe I'll revisit this topic again for a re reloaded episode in a few years.

I'd like to thank myself for questioning my own sanity, which led to today's episode and especially my top patreon contributors. There are many, many more contributors. There's like 300 people. I mean, it's it's amazing the community of support around the show. I really do appreciate my top Patreon contributors. Matthew K, Justin Z, Justin G, Camino Duncan M Corey D, Barbara Kay, Neuter Dude, Robert MNH and Friel Cameron NAA Aone Tom B, Scott M, Rob H, Lowell T Justin and Lewis M. That's patreon dot com slash PM Sutter. Thank you everyone for asking questions. Keep those questions coming. I really need those questions. I need them to live it. If you don't send me questions, I'm gonna die there you go. There you go. I'll just guilt you into it. Uh, and please leave a review on iTunes or your favorite podcast app. I really do appreciate it. And tell some friends about the show. Send those questions, by the way, to ask us spaceman at gmail dot com or go to the website. Ask us spaceman dot com for all the links, and I'll see you next time for more complete knowledge of time and space.

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