How do we measure the age of the universe? Why are different methods giving different results? How do we solve this problem? I discuss these questions and more in today’s Ask a Spaceman!
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This break is brought to you by Adobe Photoshop. Here's a fun fact. Every day, millions of people around the world use Photoshop to create all kinds of cool stuff. Designs for T-shirts and posters, graphics to promote brands and businesses, images for social and websites. Anyone can do it. And to the guy who put a bulldog's head on a parakeet's body, you, sir, are a genius. Get started for free today. Click or tap the banner to head over to Photoshop dot com. So, uh, how exactly do you measure something like the age of the entire universe? Being the avid, Ask a spaceman listener that I know you are. I'm confident that you will not be surprised by the answer of It takes a lot of math like a lot, But what I've always found strange is people's reaction to scientific modeling, which is going to play a huge role in this episode. We we can't directly measure the age of the universe. It's not like there's a clock out there ticking away, and as long as we can build a powerful enough telescope, we can resolve it, and we're just done.
Go home early like stop accepting new students in the graduate program. It's all over. No, measuring the age of the universe is an indirect problem. We have to measure other things, then plug that into a fancy math equation. And then that fancy math equation tells us the age. I mean, but the the age of the universe is not the only indirect measurement found in science. And whenever someone asks me a question and I start answering with, well, you take a model, you know their faces make this weird expression like they just tasted whatever they ate six hours ago. Not exactly unpleasant, but also not exactly welcome. It's just weird it It's such a strange reaction, but I think that people don't understand models and don't trust models, and they don't like models. And and honestly, I can't blame them like I'm recording this episode in the late spring of 2021 and we're on the nth wave of the coronavirus pandemic where N is either two or three or 57 depending on who you ask. And by and large are models of how the pandemic would spread.
How the virus would spread, how it behave have uniformly failed us in giving reliable results. You know, when it first hit, like a year ago, we thought there'd be a big spike and they go away by the summer. And then we had to bend the curve. Uh, and then and then that happened. But then its research. And then there was this another wave and and just like it's complicated and our models haven't been able to keep up to date with the evolving situation. So if we can't get a virus right, how could we possibly get the age of the universe, right? Well, it turns out that measuring the age of the universe is a slightly simpler problem than trying to model a pandemic. Who knew? We do understand the universe to be approximately 13.77 billion years old, but there's currently some disagreement about that number, and there are some disagreements between various measurements of getting that age, and those measurements, at first glance, give us very different answers. I mean, not much. We're talking like 10 or 20 million years, but it it's enough. We're precise enough and knowledgeable enough that that's a big deal, and that these different measurements are giving us different answers.
I realize that what I just said is not exactly building a lot of confidence in the whole. Use a model thing right now, but let's take an opportunity to breathe for a moment and see where this modeling ship takes us. And the first thing I need to address is the fact that we can estimate an age for the universe. I I'm not good at wax, poetic or even philosophic right now. I've done that before about the wonders of science and our powers of observation. There are plenty of previous Ask a spaceman episodes where I get into all that. No, no, no, no. I'm I'm gonna focus on a pressing practical question, which is relativity. You know, the whole relativity moving clocks run slow thing. The faster you move in space, the slower you move in time. A lot of people, uh, rightly question me. And when I say like the universe is 13.77 billion years old, they say, Well, according to who, you know if if I'm stationary on the Earth, but the earth is moving, the Milky Way galaxy is moving. Everybody's moving. Uh, if there's aliens in a different galaxy, and they're moving at a different speed. Won't they get a different age of the universe?
According to special relativity, no. Two clocks in the universe agree on the rate of passage of time and before relativity, we had this idea of, uh, the Newtonian master clock. There was this, like, absolute perfect clock ticking away somewhere in the universe. It didn't actually exist, but like it was, it was a It was a concept. It was an idea. There's a There was this standard reference of time against which all other measures of time were held up against and special relativity tore that all down and said, There doesn't have to be a master clock that everyone in the universe, depending on their reference frame, depending on how they're moving and accelerating and living their lives, will have a different measure of the passage of time. How can this possibly work well by contributing to patreon? That's one way patreon dot com slash PM Sutter to keep your relativistic clocks ticking. Thank you so much for your support, but there's more to relativity than special relativity.
There's general relativity. Special relativity says there doesn't have to be any master clock ticking away in the universe. General relativity says there can be. And in fact, there is. You're allowed to have a special frame of reference. In general relativity, we can identify an age of the universe that any observer anywhere can agree on. There is, it turns out, a very special reference frame that ticks along. There is a master clock to the universe, and we can all find it. We are moving relative to that master clock like us in our galaxy. In the aliens in another galaxy have slightly different velocities. So from our perspective, there will be slightly different ages of the universe. But we can both find a common reference frame that does give a universal clock that we can both agree on. So when we say, Oh, the universe is 13.77 billion years old and we convert years and all that into their alien language, they're like, Yeah, yeah, we agree.
And this master clock comes about because we do live in an expanding universe. Our universe gets bigger with time, so there's a breakdown between time and space. When it comes to the universe, there is a time right now, at this moment, the universe is this big. Yesterday it was slightly smaller, and tomorrow it will be slightly larger so you can identify a time based on the size of the universe. This sets up the ability to create a common reference frame, and that common reference frame is how long the universe has taken to get from the Big Bang. Until now, how long has it taken to get from that initial singularity, which we don't understand? That's that's a topic for quantum gravity today. We're purely, purely playing in the world of general relativity. General Relativity says that 13.77 billion years ago, our universe was infinitely tiny. OK, we know that's like wrong, but, like we, we can still do everything else we can do still do the rest of the episode.
So from that initial like question mark, we can count the time because the universe used to used to be smaller and they got bigger. And now it's this size. So when we go to the aliens, we can say, Hey, according to your measurements, how long has it been since the universe was infinitely tiny and there is a common reference frame for that. So that's pretty cool. So we can measure an age of the universe that is independent of our reference frame that aliens across civilizations across the universe can all agree on. And that's nice. So let's talk about the actual measurement. The problem with the age of the universe is pretty much like any other problem in all of science. You have a thing, a virus, a bunch of rocks, a vast cosmos, and you're trying to study it. And the first thing a scientist does is make some observations. What is the thing? Size? What is the thing's shape? What is it made of? What does it do when I poke it? The second thing a scientist does is develop a mathematical model to describe the behavior of that thing. How does that thing evolve with time? How does it respond to stimuli?
How does it relate to its surroundings? Why a mathematical model instead of some other sort of model? Well, a few reasons. It's more straightforward than using natural language. It's much clearer it enforces logical consistency so we can make predictions, and, uh, it makes you look and sound smart. The game of science is defined it as simple a model as possible that fits all available observations and successfully predicts behavior. There you go. I This is why I'm surprised when people turn up their noses when I bring up models because models are everywhere in science. One could even say that science is a mathematical model of the natural world. And you know what? I'm gonna go ahead and say that, and if you're up for it, you can say it along with me. Science is a mathematical model of the natural world. So when I say well, we start with you. You work with this model because the edge of the universe you shouldn't turn your nose up at that because literally, like everything I say in science is based on some sort of mathematical model. This is no exception. You got a problem with this? You got a problem with all the science, and that's a certainly a different episode.
So what's the mathematical model of the natural world when it comes to the whole entire universe? Well, we can start with general relativity like I mentioned before. This is a game of GR GR general relativity connects space time to the contents of spacetime. So if I have matter and energy matter and energy influence, they bend and warp and curve space time and then the bending and warping and curving of spacetime tells the matter and energy how to act it. It provides this linking This is our modern theory of gravity. So any time you have a situation where you've got some stuff and you're trying to figure out how it evolves, you use general relativity. General relativity is is more of a tool kit. It's a way of building models under a single framework. You can apply the GR toolkit to all sorts of situations. Anytime you got matter and energy, you're trying to figure out how it evolves. You apply GR, you got matter and energy In the solar system, you got stars and planets and stuff. Boom. You can use GR. You got matter and energy around black hole Boom.
You can use GR. You got matter and energy in a galaxy boom. You can use GR like any time you've got matter and energy in the universe. Boom. You can use GR general relativity to predict how that matter and energy will behave when you apply the general relativity tool kit. It's like this massive toolkit. There are 10 equations. They're all tangled up with each other. It's it's actually like, notoriously hard to to work with general relativity. Uh, but we make a few simplifying assumptions, which we've talked about before. You assume that the universe is spherical, that this stuff on average is uniformly distributed. You know a couple of things. This greatly simplifies the math so you can make progress. And once you do that, you get a special set of equations called the Friedman Equations. The Freeman equations are named after Alexander Friedman, who figured them out, which is a relief that he had that last name so it wouldn't be confusing about who discovered it and why we named it that it. It's the Freeman equations.
Nice line up there. The Friedman equations tell us how the universe evolves based on what's inside of it. It's a mathematical model, and it's easy. It's actually they're not complicated equations at all. You plug in the contents of the universe at any time, like OK, OK, we got this much dark matter. We got this much regular matter. We got this much dark energy. We got this much radiation. We got that many potato chips and on and on and on and on, and it gives you the expansion rate at that time. So if the contents of the universe change or evolve, then the expansion rate will change, like way back. In the past, the density of matter was way higher because it was the same amount of stuff but crammed into a smaller volume. So matter had that kind of influence on the expansion rate back then. Nowadays, the matter is more diluted. It's all thinned out. Since the density is lower, its influence on the expansion rate is lower. And in the far, far, far, far, far distant future it's its influence on the expansion rate will be, like zero, effectively zero.
I do not know what the effect of potato chips are on the expansion rate and how that changes over time. Maybe I'll write a paper on that. But the Freeman equation does what any scientific model does. It connects an observable like the contents of the universe to a behavior how quickly the universe is expanding. You do that at any point in time and a bunch of points in time. And then, you know the expansion rate over time, like, OK, today the expansion rate is this. Yesterday it was that back then it was that. And then you put that all together. Once you know all those expansion rates, you can figure out how long it took the universe to go from TC tiny to its present day size. That's the age as usual. I'm simplifying a lot of math here, but you get my draft the best place by far to measure the contents of the universe to play this game like, uh, and if we want to know the age of the universe, we need to know its expansion rate over time. And then from there we can get an age. The best place to do this is the cosmic microwave background, the cosmic microwave background or CMB, because who wants to keep saying that all the time?
The CMB is the leftover light from our when our universe was only 380,000 years old. This is a very special epoch in our universe. It transitioned from being a hot, dense, opaque plasma to a neutral gas that let light free. Initially, that light had a temperature of like 10,000 degrees. Now it's like three degrees. It's cooled down a bit. It's all the way down the microwaves, but we can see and we can do sky maps of it so you can literally take a picture of the universe. When it was nearly 380,000 years old, the CMB gives us precise, very precise knowledge of the contents of the universe. In fact, our maps of the CMB especially is the ones delivered by the the European Space Agency's plank satellite, which was the latest all sky map of the CMB from a few years ago. And I'm not just saying that how awesome plank is because I was a member of the plank collaboration it It's generally accepted to be awesome. Some of the most precise measurements ever achieved in science.
Actually studying the CMB is relatively straightforward because it's just a plasma at 10,000 degrees, and we actually have a really good physical understanding of plasmas at 10,000 degrees. Like our physics of plasmas is very, very sophisticated. We know a lot about plasmas. We know a lot about how things operate at these temperatures because we can recreate that in the laboratory, right? You can make a box and make it 10,000 degrees. You can directly study it if you want. We can recreate the conditions of the universe. When it was when it was this age. Easy stuff, really hard stuff, but relatively easy stuff. And so we can plug in various models, like different amounts of dark matter and how it might behave. Different amounts of normal matter, different amounts of radiation. We can plug all that in, and we can just directly compare to this massive data set of observations of the CMB. So we get this exquisite, highly detailed, precise measurement of the contents of the universe. We plug it into the Friedman equation, you get an expansion rate, and you get the expansion rate at that moment in time.
But once you lock down like OK, we got this much dark matter, we got this much normal matter. We got this much radiation. We know how the dark matter evolves with time on a cosmological scale, it just thins out. With time, it gets more and more diluted same for the normal matter. And same for the radiation. Just as our universe expands, all those components dilute and get thinner. And so their influence on the expansion rate changes in a very predictable way. And so, from that measurement of the cosmic microwave background way back when we can get the contents and we have a good understanding of how they evolve Boom, bang. You got your expansion rate as a factor of time. And then you got your age of the universe. One major caveat here, Big One. And that's dark energy. Dark energy is the name we give to the accelerated expansion of the universe that we see today. Dark Energy started doing its thing about 5 billion years ago. Dark energy was not really present in the early universe.
It was not a major player. We can't see dark energy in the cosmic microwave background. It didn't really have an influence on the physics back then. It was just hanging out in the background, waiting for its time. It was actually waiting for all the matter to dilute enough that its influence on the expansion rate would drop low enough that it could start to influence the expansion rate. So we do have to add one thing to the CMB measurements. We have to add dark energy. We have to add it in by hand based on other measurements. OK, that's not so bad. We plug in what we know about dark energy. We get the present day universe. We can fast forward to the present day expansion rate done right. Well, almost before I continue, I want to let you know that 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 life. Experience is something I'm absolutely not ashamed to talk about.
I wish more people used the therapists and counselors to take better care of their own mental health, just like they take care 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 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 Now back to our Astro therapy session brought to you by not a licensed psychologist, but an astrophysicist, but good enough, right?
At least for now. Once you have a measurement of the cosmic microwave background in hand, and once you know something about dark energy, you can basically reconstruct the entire history of the universe, at least in terms of its expansion rate. And you can even predict what today's expansion rate is something we call the Hubble constant. The Hubble constant is not constant, but I'm not in charge of naming things. It's just the name we give to the expansion rate of the universe right now. A billion years ago, the expansion rate was different. That's not the Hubble constant today. The expansion rate is whatever it is. Today, it's around 70 kilometers per second per mega parsec. If you're curious, it's not a constant, but it's called the Hubble constant whatever. But once you have the CMB, once you have some knowledge of dark energy, you can get, predict and measure and estimate what the expansion rate of the universe is today and across all the time. And then you can get the age of the universe. But hold on. We can flip this script. I've been focusing on measuring the contents of the universe, being the observable and then the expansion rate coming out of the model and from there calculating the age.
But I'm about to blow your mind. There are two sides to every equation, folks. There are two sides to every equation like like think of something simple like like Newton's Law, like F equals MA, force equals mass times acceleration. You can measure the acceleration in the mass and get the force. You can also measure the force in the mass and get the acceleration you can go the opposite direction. There are two sides to every equation. You can work them in either direction. What you call an observable I may call a result of the model and vice versa. With the Freeman equations, you can plug in the contents and get the expansion rate. You can also measure the expansion rate and use that to estimate the contents. So what if I told you it's possible to measure the expansion rate of the universe today? Right now, directly before our very eyes, we do this all the time with supernova, a very special kind of supernova called type one a supernova. This is what happens when a giant star spills its atmosphere onto a binary white dwarf. It reaches the critical threshold the white dwarf blows up. It's very, very bright. These are called standard candles or standardize candles because it's pretty much the same physical system.
Every time White dwarfs are all about the same size. They blow up in all about the same way, so we know or can estimate how bright they should be. And we can compare that to how bright they really are in some distant galaxy and do that for a bunch of different Galaxies at different distances and different speeds moving away from us. And we could just measure the expansion right, like right there. And since standard candles and supernova, you can't really see very, very far away with them because, you know, even as bright as a supernova is, they can't go that far with our telescopes. So it's a relatively, uh, nearby measurement of the expansion rate, which means it's a measure of the expansion rate, pretty much of what it is today. Like today's expansion rate, you can measure directly with supernova, so using supernova, we can measure the expansion rate, then plug that into the Friedman equation and get the contents. It's It's a lot harder to do this now, I'm saying, but you get the gist. And once you've measured the expansion rate today and once you've solved the Friedman equation, you can run the clock backwards and get an age of the universe.
And here's the sticky thing. These two methods Method number one is going very far away to the cosmic microwave background, getting a very accurate measure of the contents, then running the clock forwards to get the current present day expansion rate disagrees very slightly with the expansion rate measured from the supernova, and you'll see this presented in different way. We it's called the crisis in cosmology or the cosmological constant problem. Some news outlets and articles and even journal articles will reference the expansion rate of of Today as being the major source of disagreement. Sometimes it'll be phrased as disagreements over the age of the universe is all the same thing because it's all coming from the Friedman equations. Like I said at the beginning, it's not much. It's only like 10 or 20 million years on a difference of a measurement of 13.77 billion. But we're precise enough in our measurements nowadays that this difference is big enough to be statistically significant.
These measurements are both becoming very, very, very precise. We're gaining a lot of knowledge both from the CMB and from supernovae, and they're disagreeing to a big enough amount that it's it's noticeable. We have different methods that should agree. These are two different sides of the same equation. They should end up equaling each other because that's what an equation does. It equals two things But we measure one side of the Freeman equation, the contents and we measure the other side the expansion rate, and we're getting different results. Hence a crisis or a problem. Now I hear what you're saying. Paul, Paul, Paul, Paul. Paul. Why in the world should we trust a model? This is in your voice in particular, but somebody instead of the expansion rate directly before our very eyes. I mean, are you seriously saying we're gonna go back in time, over 13 billion years, Make some measurements of the contents, plug it into a model fast forward 13 billion years and get an expansion rate?
And we're supposed to believe that at the same level as just using supernova to measure the expansion rate right before our very eyes. Why don't we just declare that something's wrong with our CMB measurements or the models and move on with our lives? Guess what, folks? Because even the supernova measurements use models. Everything in science is a model. Or should I say science is a model of the universe? Yes. Using supernova as standard candles, you can directly access the expansion rate of the universe. But to make a supernova a standard candle to really say I know exactly how bright that supernova should have been so that you can compare it to how bright it looks and use that to get a distance measurement to a galaxy that takes a model that takes a model of how stars work, how the supernova work, how quickly they brighten up, how bright they get, how quickly they decay. It's not as simple and straightforward as just saying, Well, all these type one a supernova are pretty much the same brightness.
And so all we have to do is measure them. No, it takes a lot of modeling, a lot of work, a lot of understanding to make the claim that type one a supernova are precise standard candles that we know how bright they're supposed to be takes a lot of mathematical modeling. So we have a few choices. Maybe something really is going wrong with our CMB measurements. Maybe we don't understand the universe. We don't understand plasmas as well as we thought. We're we're doing something wrong. Maybe Plank messed up. Maybe we messed up something in our analysis back then, and we we spit out bad, bad results bad data. Maybe something is going wrong with our supernova measurements. Maybe we don't understand supernova as well as we thought we did. Maybe things are a little bit messier than we thought, and all it takes to make this crisis go away is for one or both of these measurements to just be more uncertain than we thought it was like we we're claiming a certain level of certainty.
No, no, I really say it's It's this. It's like, very narrow, narrow now or narrow. But if it turns out it's actually you're a little bit more uncertain. Things are a little bit messier than you thought. Then the whole thing goes away because once things are uncertain enough, then they don't disagree by this large amount. Like if I say, uh oh my my measurement of the expansion rate is five plus or minus one, and your measurement is 10 plus or minus one. Then we greatly disagree. But if I say my measurement is five plus or minus three so anywhere from 2 to 8 and your measurement is 10 plus or minus three, anywhere from 7 to 13, well, then we overlap a little, you know in that +78 ballpark. We overlap and the crisis goes away. So the whole reason this crisis exists is because both sides, the CMB side and the supernova side are claiming that their results are very, very precise. So maybe the CMB results aren't as precise as we thought or just flat out wrong. Maybe the supernova results aren't as precise as we thought they were or just flat out wrong.
Maybe something's going wrong with our model. Remember, we use the Friedman equation to make this connection. We have to plug in our understanding of dark energy. Maybe dark energy is more complicated than we thought. Maybe dark energy changes with time or or connects with dark matter in an interesting way. You know, maybe there's some extra forces or interactions happening in the universe at large scales. Maybe the Friedman equation itself. Maybe general relativity is starting to break down. And this is the first crack in general relativity that's ever had in its in a century. Maybe it's all of the above. Maybe we don't understand supernova and CMB and dark energy. Should you trust models in science? Sure. But like everything else in science, all answers are provisional. This is our answer. Until we get better data, I have my own personal take on the crisis in cosmology. If you just want to stop the episode here and have a pretty objective discussion of the issue, that's fine.
If you wanna have a subjective discussion of the issue, then keep listening. I am an astrophysicist. I am a cosmologist. I have worked on the cosmological constant problem. I was a member of the plane collaboration when we did our analysis. I personally believe and and most people believe, that the CMB measurements themselves are fine, that we didn't mess up the analysis that we do understand our uncertainties. Most people, most cosmologists. I'm not just saying this because, like I agree with them, it is true. Most cosmologists think that the CMB measurements are totally fine. Also, it's my opinion, and I'm not alone in this opinion that something's a little off with the supernova measurements that they are a little bit more uncertain than what the supernova people are claiming that we're making this whole crisis in cosmology exists, Uh, because of the observations of like six Galaxies, that's enough to to drive the uncertainty down and to move the measurements so that this crisis exists. So if you like, get rid of those six Galaxy measurements, this whole crisis goes away.
A lot of the discussion in the crisis in cosmology is led by Adam Reese. He is a Nobel Prize winner. He won the Nobel Prize for using supernova to discover dark energy in the first place. It's my humble opinion, and I'm not alone in this opinion that the crisis, this controversy wouldn't exist if Adam Reese wasn't around to push on it like it smells like he wants a second Nobel prize. One was just wasn't enough. I'm of the opinion that supernova are much, much messier than we think they are. You can make some astrophysical adjustments if, like if you change, like the rotation rate of the white dwarf, and you don't understand the rotation rate as well as you thought. That's enough to make the supernova measurements uncertain enough that the crisis goes away like that's it. That's all it takes is to change the rotation rate of the white dwarfs, and it changes the brightness in unpredictable ways. And once you account for that uncertainty, then it goes away, but that's a boring solution. And the truth is, we've been working on dark energy for 20 years now.
It was discovered in the late 19 nineties. So over 20 years, pushing on 25 years since we learned about the existence of dark energy, we don't know much more about dark energy than we did 25 years ago. We have a much more precise measurement of it. We know that it certainly exists, and it's there. But in terms of explaining it, understanding it, knowing its history, whether it has changed in time or it is just a constant we haven't learned much in 25 years. The crisis in cosmology is exciting and interesting for cosmologists because it's something to talk about. It's a potential observational conflict between one kind of measurement and another kind of measurement. And when observational conflicts exist, it gives you an opportunity to build a new theory of physics, like if if if the results hold up, if the supernova measurements and the cosmic microwave background measurements continue to disagree, then you have to explain it.
And once you explain it, you need a new theory of physics to explain. And once you do, you have a new theory of physics like. And maybe the best explanation if this holds up is like evolving dark energy or changing dark energy with time. Well, that requires new knowledge of dark energy that we didn't have before, and that's exciting. And that's interesting. Like the crisis in cosmology from a very pessimistic point of view is an excuse to keep writing papers about dark energy. Otherwise, there wouldn't be anything left to say until we have a new round of observations until a new Galaxy survey a new CMB scan like and that takes like years and decades to plan out and do so. But in the meantime, as long as the co the crisis exists, we can keep talking about dark energy, and we can keep writing papers about it. If the crisis went away, if it was something boring, like whoops. See, we don't understand supernova as well as we thought. Well, then, that's the end of the discussion. Once you fix that measurement, the crisis goes away and there's nothing left to talk about, so a very cynical point of view.
It's like I feel like sometimes cosmologists want to keep the crisis going so that they can keep talking about dark energy because it's something to talk about. Otherwise, we're just back to where we were 25 years ago, which is we don't know anything about dark energy. That's my take on it. I don't think the crisis is a crisis. I think we need to better understand our supernova measurements. I think the supernova people are great cosmologists. They're holding their data, their methods, their analysis a little bit too close to the chest. For this to be a a fully honest discussion, I would like to see more an openness. All the CMB data is publicly available. All of our analysis is data like there were hundreds of people involved in the blank collaboration. It's all publicly available, so it's been vetted years and years and years later it's been vetted, redone by independent groups, they all get basically the same answer. Maybe dark energy is evolving and changing with time, and that's an explanation for this crisis. That's the most interesting answer.
But to me, if it's interesting, it's probably wrong. We'll see where it goes. Let's check back in in like five years or a decade. Maybe the crisis still exists. Maybe one of the camps, the CNB camps or the supernova camp gives in and says, OK, OK, fine. The uncertainties are larger than we thought. Maybe some new measurement comes in like there. There are more ways of measuring the expansion rate of the universe and the age of the universe. They're not as fully fleshed out and realized as CMB and supernova and some other techniques. Maybe they come in and, like, weigh one side or the other. Maybe not. Oh, it it It makes work for cosmologists while we wait for another mission to fly. I suppose that's a cynical take, though. In the end we are trying to understand the universe. We are trying to understand the expansion of the universe. This is a fun question. It's a challenging question. It's a difficult question right now. As far as we understand, different measurements are getting different results, and that's an opportunity for progress. No matter what, we're gonna learn something. Either we learn something about the CMB.
We learn something about supernova. We learn something about dark energy in the universe. No matter what this crisis will lead to increased knowledge, which is not a bad thing. And so maybe it's worth it. Thank you to Robert B on email and Campbell D for asking the question that led to today's episode and thank you to my top patreon contributors. It's patreon dot com slash PM Sutter Matthew K, Justin Z, Justin G, Kevin Oak and Duncan M. Corey D, Barbara K Dude Robert M, Nate H, Andrew F, Chris Cameron, now NAIA a. Tom B, Scott M, Rob H and Lowell T Thank you so much. I truly, truly do appreciate it. Keep those questions coming in the hashtag. Ask us space and be sure to leave a review on iTunes or your favorite podcast application. Go to ask us spaceman dot com or email. Ask us spaceman at gmail dot com, and I will see you next time for more complete knowledge of time and space.