Into the Impossible With Brian Keating - Did JWST Just Solve the Biggest Crisis in Cosmology? Wendy Freedman [Ep. 461]

Episode Date: October 6, 2024

Discrepancies between different measurements of the Hubble constant have caused a major crisis in cosmology.  Our guest today, the incredible Wendy Freedman, is at the forefront of efforts to resolve this tension. Known for her pioneering work on the Hubble Key Project and her important contributions to the measurement of the Hubble constant, Wendy is now using the James Webb Space Telescope to bring clarity to this debate.  With decades of experience and a deep understanding of the complexity of cosmic measurements, there is no one better to shed light on this issue. So, can the James Webb Space Telescope help solve one of the biggest puzzles in cosmology? Tune in to this episode of Into the Impossible to find out!— Key Takeaways:  00:00 Intro  01:18 The role of JWST in solving the Hubble tension  04:01 Comparing different distance indicators 20:45 Standard sirens  34:05 Accurate cosmology vs. precision cosmology  36:35 Vera C. Rubin Observatory and Giant Magellan Telescope 42:50 Wendy’s take on dark energy  45:32 Outro  Additional resources:  ➡️ Learn more about Wendy Freedman:  💻 Uni website: https://astro.uchicago.edu/people/wendy-l-freedman.php  ➡️ Follow me on your fav platforms: ✖️ Twitter: https://x.com/DrBrianKeating 🔔 YouTube: https://www.youtube.com/DrBrianKeating?sub_confirmation=1 📝 Join my mailing list: https://briankeating.com/list ✍️ Check out my blog: https://briankeating.com/cosmic-musings/ 🎙️ Follow my podcast: https://briankeating.com/podcast ✨ Member's only playlist: https://www.youtube.com/playlist?list=UUMOmXH_moPhfkqCk6S3b9RWuw Into the Impossible with Brian Keating is a podcast dedicated to all those who want to explore the universe within and beyond the known. Make sure to subscribe so you never miss an episode! Learn more about your ad choices. Visit megaphone.fm/adchoices

It's peak pollination season, and my business is scaling fast. To keep the nectar flowing, I need a phone plan with top priority data speeds. That's why I chose Google Fi Wireless. My connections stay strong even when the hive is buzzing. Plus, unlimited plans started $35 a month. Now that's a deal that doesn't stay. Explore Google Fi Wireless plans today. Plus taxes and government fees.

Google Fi Wireless is not subject to data traffic deprioritization during times of high network usage. 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 the stay. Did the James Webb Space Telescope just solve the biggest mystery in cosmology?

The discrepancy between different measurements of the Hubble constant has been causing a lot of a jada in the astronomical community for the past few decades. But Wendy Friedman, a renowned astronomer and professor at the University of Chicago, is at the forefront of efforts to alleviate and solve this cosmic conundrum. Known for her pioneering work on the Hubble Key project, the very reason the Hubble Space Telescope was launched in part and her significant contributions to measuring the Hubble constant and properties of stars throughout the universe. Friedman is now leveraging the cutting-edge capabilities of the Web Space Telescope to tackle the Hubble tension head-on, with decades of experience and a deep understanding of the intricacies of cosmology, of measurements, of accuracy and precision. There's simply no one better to shed light, if you will, on this issue. So join us as we take a deep dive

and perhaps resolve the tension, the frustration, and the anxiety. astring astronomy today, courtesy of the brilliant Wendy Friedman. Let's go. Any sufficiently advanced technology is indistinguishable from magic. Open the pod bay doors, Howard. Wendy Friedman, thank you so much for coming back on the podcast, your second time on the podcast. Glad to do so. Yeah, thanks for hosting me in your beautiful office here at the University of Chicago. It's always a pleasure to come here. I get to experience humidity whenever I come from

Southern California, where you used to live for many years, director at Carnegie. So we're going to talk about your career and your current research and this really cool looking model in the background over there that you're so intimately connected with. But the first thing I think would be interested in talking about, there are these recent results that you have been participating in and leading to large part with the James Webb Space Talcum. So how did that come about? Because I understand from my friend Adam Reese, who's been on many times.

times it's very difficult to get time on the James Webb Space Telescope. They don't even know of all your accomplishments because everything is blind. Walk us through the process. How did you come up with the idea? What is it telling us? And how is it perhaps resolving the Hubble tension without the need for a psychotherapist? You're right. It's very difficult to get time on JWST's highly oversubscribed and very competitive. At this juncture, we're trying to measure the Hubble constant more accurately than it's ever been possible to do before. And, you know, know, there's this possibility that there's a discrepancy between the nearby values of the Hubble constant that we measure locally and what you get infer from measurements of fluctuations

in the cosmic microwave background. So we need higher accuracy than we've ever had before in the local distance scale. Because the microwave background observations now are so precise that we need to make sure that locally we can have a comparable competitive decision to see if the discrepancy is real. So our focus with JWST and wrote a proposal that depends not only on Cepheid variables, which we use, for example, with the Hubble Key Project, which the Shoes team also uses, but including also two other methods, the tip of the red giant branch and a new class of carbon stars we're calling J.A.G.B. stars. And the premise is that because there are systematic uncertainties in any method.

They all have their own. The only way that we will understand how we're limited by systematics is to make the measurements very precisely in each case. So you need distance indicators that are very precise internally and compare those. So that was our proposal to measure the distances to nearby galaxies that have hosted Type 1A supernovae. None of the methods I've just described goes out far enough that you can get into the smooth Hubble flow.

The peculiar motions induced by gravitational interactions are too large to measure it accurately at the 1% level that is now a goal. And it's a very challenging goal. Let me emphasize that. And so what we're doing is measuring the distances to the same galaxy is using these three techniques. So we didn't know. Are they all going to agree?

Will there be three different answers? And will there be an outlier? let's see. And if there's systematics, we'll try and uncover that. And so do the tip of the red giant branch, the carbon stars, the sephiates, do they have kind of orthogonal systematic effects? Do they share common systematic effects, you know, that have to be mitigated and you learn something from one branch and apply to another one? Or are they distinct?

Well, the nice thing about them is they're completely different populations. So sepheids are young stars. We find them in regions nearby to where they actually formed because they haven't had time to move away, diffuse away from the locations where they were formed. And so we can only find sephiads in the disk, and these are young stars. The tip of the edge eye branch, we can find them in the disk and the halo, but the advantage of the tip of the edge of branch is that you don't have to work in the disk, because in the disk you have lots of dust, you have high surface density of stars, so you have potential

crowding and blending of the objects, and that means you can't be. measure the lovelocity is very accurately. And when we get out in the halo, you don't have those problems. And then the JAGB stars are an intermediate population. We find them in the outer disc, so not as much of an issue of crowding or reddening and a very different evolutionary stage again. So that's the advantage. They have completely different systematic.

In common, what they have is the calibration. So with JWST right now, our galaxy that provides the geoccurring, geometric distance to anchor all the galaxies is NGC 42-58. It's a galaxy that has a black hole in its center, and it has water megamazers that are orbiting the black hole, and you can use those objects to estimate a distance, such as a geometric distance. So all of them have that zero point calibration. And that's true even if you had more calibrators, you can use the same ones for the target. get galaxies. So they're nice things. They're all independent in terms of their schizekes. And

then the relative comparison is very straightforward. When you say tip of the red giant, how do you know something's truly in the tip? How important is it to be, maybe say a little bit about HR diagrams and how you know this for some of the folks that might not be as much of astronomy mavens. Well, there can't be as much as you, but even as me. Can you describe what does it mean? What is exactly going on with the tip of the red giant branch? Yeah. So Giant Branch stars. are phase of stellar revolution, our sun will eventually become a red giant. And they have a core that has already exhausted the hydrogen and its center. Most stars spend most of their lives

burning hydrogen into helium. It's called the Bain sequence, and they spend most of their lives there. So these stars have used up their hydrogen. It's now got a core that's made of helium, a very dense state of helium, to degenerate core. And they're surrounded by an atmosphere of hydrogen or a shell of hydrogen and then an atmosphere. And the hydrogen is burning again, still burning hydrogen into helium.

And it keeps, so that's what's powering its luminosity. And it's dumping the helium that it's forming onto the core. So it's getting hotter and hotter, more and more luminous. And then it reaches at the point where the temperature is about 100 million degrees,

it can start to burn helium by this trupt. triple alpha process in a non-degenerate way. And so there's a thermal runaway. So the star can't expand because it's degenerate. The temperature is now enough you can start burning the helium and it can't expand. So it just... Wishing you could be there live for the big game, soaking up the atmosphere in a crowd.

But too often, life gets busy. Or the price holds you back. Price line is here to help you make it happen. With millions of deals on flights, hotels, and rental cars, you can go see the game live. Don't just dream about the trip. Book it with Priceline. Download the Priceline app or visit Priceline.com.

Actual prices may vary, limited time offer. The temperature gets higher and higher, higher, runs away, and the star very rapidly then falls onto the horizontal branch. It does it. So it's no longer ascending the red giant branch. It's reached the tip. And we call that the core helium flash

and the position at which this core helium flash occurs is what we observationally refer to as the tip of the red giant branch. And it's very well defined. You can actually see it by eye. You don't have to do any sort of data processing to, you see it. The giants climb, and then there's a small population of asymptotic giant branch stars. They provide a sort of pedestal, but you can still see this discontinuity. You measure the first derivative of the luminosity function, and we do lots of tests of injecting artificial stars, et cetera, et cetera, to see how well we're doing that, but it's very well measured. It's very simple.

And that's a nice aspect of the method because sephiids are more complicated. You have to measure periods for them. You have to have colors so that you can correct for dust. You have to worry about prouting and blending because they're in high surface brightness areas. You have to worry about metallicitis. There are a lot more factors that go into measurement of sephiate distance. Do the TRGBs, do they appear in globular clusters? Because those are also, you know, they do.

Indeed. And we know those measurements in the Milky Way in globular clusters and use the gaius satellite where they're parallaxes of those. She gets very active. So the number, you don't have as many of them. Yes. We have to do it in a way that we form a composite common magnitude diagram. But yes, absolutely.

Okay. Sure in globular clusters. Well, you brought up the complexities of sephiads. And I wonder if you could recount this, you know, kind of wonderful story in the history of astronomy me were Henry Anna Levitt's law, which, well, why don't you have to describe? Yeah, I can't resist. When I had on, I've had on, like, famous philosopher of the mind. His name is David Chalmers.

He came up with this concept called the hard problem of consciousness. You may have heard about it. Yeah. But it's quarks, absolutely. Yeah, so he's an amazing. I had him on, and he's from Australia. And I said, you know, David, if I had on ACDC, also from Australia, and I didn't ask them to play back in black.

I'm not doing a good job as a podcast. So I have to ask you as one of the foremost astronomers of our generation, describe what Henry had a Leavitt did. And my question for you is, how could they make so much progress and so much reliance on sepheate properties before they even knew anything about nuclear fusion? I mean, when she came up with this law, which you'll describe, they didn't know. Nuclear fusion even existed or how it took place in the core of stars or even elsewhere. So please, could you describe what is Leavitt's law?

and how could we make the progress that we made so rapidly in the early part of the 1900s without knowing any nuclear physics? Henry Lennett was studying stars in our nearby galaxy that we now know our galaxies. We didn't know that at times in the other. The large vatillard and a small metal cloud. And so, you know, as you know, and many of your listeners probably know, there was a debate at that time about whether or not our Milky Way galaxy was the entire extent of the universe or whether it was a galaxy as we now called them, similar to the Milky Way.

I mean, there were other galaxies similar to the Milky Way. And there was no way of telling because you couldn't measure the distances to these objects. There was no way of doing that other than for the nearest stars. And what Henrietta Levitt discovered was that there were stars in the Magellanic clouds that were changing their brightness over time. And so she had access to harder plates, photographic plates, which was the detector at that time.

And these are glass, big glass, for the ration plate. And what she found was that the brightness of these stars, they would get greater and greater and then at full more slowly. So rapidly rise in brightness and then fall off more slowly.

And that was similar to stars that have been known since the 1700s, Cepheid variables that were known in our own Noghulay galaxy. And so she made the further observation that the brightness of these stars was related to how fast they were changing in their brightness, the period of variation of the stars. So she plotted the brightness versus the period

in a logarithmic form and discovered there was this really tight correlation. And so the implication of that is that if you could measure the distances to some sephiates by some means, geometric perhaps means, then if you could measure the brightnesses of these stars, if you could find them in other objects, then you could determine just by the

inverse square law of light how far away. Light falls off as one of the, over the distance squared. You could determine the distance to that galaxy. So it was an empirical discovery. And again, nobody knew what the implications were, what the fundamental underlying physics was, but it was an empirical relation. People didn't even realize that the stars were pulsating at the time. Now, that came a few years later. But her results. had enormous implications. And sadly, she died before she was ever to see what the implications and those eyes own were. There's a new book coming out in the fall from MIT press about her that I'm going to have the author on. She's coming on. She's great. I've spoken to her.

Oh, you have. Okay. Great. Well, writing this conversation up when I talk in there. So another thing that I've wondered about, you know, kind of inverting my question is now that we know so much about nuclear fusion, has that impacted, you know, does that have an effect on the, like, cosmic distance ladder? Does it affect things or have we improved it, not merely knowing there's a correlation, understanding that causation effect in great detail through simulations of nuclear fusion, understanding the quantum mechanics of it, and so forth. Yeah, it's interesting. I mean, for cephalids, we don't yet. We cannot start from first principles and evolve of all the cephalids and say this is what we should find for the new was.

It's too complex. And the atmospheres are complex and we don't, there's still really a lot of uncertainty about how metallicity might affect the luminosity of these stars. So it's not just the interior is understanding the stellar evolution part of the interiors, but there's also an atmosphere and the atmosphere is in motion. So, no, we cannot do that.

The probably closest method would be the tip of the red giant branch. The stellar evolution of those stars is very well understood and it's been understood for decades. We understand the core helium flash. That's been really well modeled. And we do understand the nuclear physics

of those objects. And some of these carbon stars, what are they called J-A-B or? J-A-G-B, yes. J-A-G-B. That has to do with their spectral class three K. I like the bands of what you measure them, the J-BAN or something.

It's the region. So it turns out that there's in the infrared in the J-Ban, which is about 1.2 microns. The luminosity of these stars is essentially constant. And so it's a subset of carbon stars. And the reason, apparently,

that they show this constant luminosity is that these stars at their phase of evolution are actually dredging up material from the interior regions to the atmosphere. And some of that is carbon and that's what makes them look red.

And so the stars that are more massive, they are burning the carbon before it gets to the surface. The stars that are less massive never actually dredge up the material. So there's this intermediate mass range. where they are dredging up the carbon, and they, so they're bounded by these two limits. So these aren't like white dwarves that are pure carbon, right?

No, no, no. Okay. So the physics of the carbon stores, are they also apparently straightforward compared to the modeling sephiates from first principle, as you said? I think, no, again, understanding their atmospheres is just, it's not simple. It's much more complex than the giant branch stars. For those of us who are, you know, as familiar as you are with, you know, main sequence, stellar evolution. So my understanding was that, you know, the sun's nuclear fusion, you know, processes really occur in a relatively small volume, less than 10 percent of the volume of the star.

Maybe I'm wrong about that, but you were saying that for some of these objects that the tip of the red giants, they're actually fusing in the outer, in the outer atmosphere. Is that correct? No, it's still in the core. Okay. And what fresh? There's an atmosphere above that. Yes. Okay. And a shell surrounding the core. No, no, it's, it's very much the interior. But I think it's important to say that these methods, all of them, we don't understand type 1A supernobie to modernize. That's, yeah, one thing. These are empirical relations that we're using. And so, you know, they appear to work.

But that I think is, as I said, other than the tip of the red giant branch, probably a disadvantage than that we don't understand them well enough to start from first principles and say what the philosophy is ought to be. And would you have wanted to use the web telescope regardless of, you know, the targets that you were looking at? And it just happens to be the most advanced space telescope with understood systematics, at least. Or could Hubble still play a role in measuring these tip of the original? So, you know, Hubble has been the workforce for the extra lack of decency scale now for decades, right? And it's what we use for the key project. It was the Sefayotes have been the gold standard. and the reason that Hubble is so useful for Cepheid,

is that Cepheid, their amplitudes are larger in the optical part of the spectrum than they are in the infrared. The temperature sensitivity is smaller in the infrared. So it's a very good machine for finding these variable stars. And so I think that will remain the case. To actually discover Cepheid's, Hubble is a tool that you want or something that has sensitivity in the optical.

In terms of getting at the systematics, which is what we really have to be focused on now, JWST has a huge advantage and that it is sensitive in the infrared part of the spectrum. So the dust that we've vaguely talked about is the effects of dust are much smaller in the infrared. The resolution is about four times higher for JWST than it is in the infrared with hub. And so the crowding resolution issue is much less and the effects of dust are less. And those are the types of things now that we need to improve upon to get a more accurate measure. So find them with level, follow them off with JWST.

It's clearly the way to go at your moment. Have they, I talked to Bob Kirshner not too long ago and his late graduate student, Andy Friedman was my postdoc for a while in San Diego. They used to talk about the differences in type 1A supernova and the infrared sort of had this new luminosity peak that sort of comes on delayed and so forth. Are there other peculiarities that come in when you have an infrared machine like web? Your summer starts now with Memorial Day deals at the Home Depot. It's time to fire up summer cookouts with the next grill,

four-burner gas grill, on special buy for only $199. And entertain all season with the Hampton Bay West Grove seven-piece outdoor dining set for only $499. This Memorial Day get low prices guaranteed at the Home Depot. While supplies last, price invalid May 14th or May 27th, U.S. only exclusions apply. See Home Depot.com slash price match for details. That you wouldn't have noticed or maybe couldn't have measured as accurately, or is it primarily because it mitigates dust and the systematic effects that you speak about?

I think for the objects we're studying right now, it's really the tool that we need. Where we're limited right now is just a small number of objects that are available to actually measure. And so the statistics are still better with Hubble than they are with JWST, but that will improve with time. And the other is that because the samples are small, we're looking potentially that there may be systematic effects in the calibrators themselves.

And that's something that is, you know, we're starting to see hints of in the data, and we need to follow up and make sure that these aren't problems. So the objects that have been measured with Hubble that are the most distant objects in that sample, and it's a small sample, it's a few dozen and to show

that they don't have resolution issues so if you get let's say your corrections for crowding wrong then you're going to get your colors wrong later you get the dust corrections wrong then you're going to get your metallicity correction wrong

so it's not a simple matter as maybe there's one systematic but they are degenerate and so that could have a lot bigger effect than you think if you get them wrong. And the farther you push out in distance, the harder those measurements become. So I think within a few years, we will understand if, you know, either there are no problems or then there are problems with the more distant ones that we'll see. We just don't know yet,

because the distant ones have been tested. Right. And if, like, one of your grandkids comes to you and says, you know, nano, or they call you your grandma. I'd be right. Good. You know, I really want you to help me on my, you know, first grade science fair project, I want to develop, measure the Hubble constant, using this other tool, and it could be anything. What would be most exciting for you? And I'm kind of interested in your thoughts and things like standard sirens and all sorts of exotic phenomena.

But what would make you just so excited to move into? I'm very excited about the standard sirens. I'm talking about them. Maybe explain them first to the audits. Yeah. So the idea with standard sirens, these are objects that now have been detected with why and other gravitational wave detectors. So there are two neutron stars that start inspiring and coalesce,

and you can use the measurement of the gravitational wave interaction. If you have also a measurement of the velocity, you need a spectrum of the object. So you need an obstacle or some sort of telescope to also get a velocity, because you need distance and velocity to measure the Hubble constant. And so it's a very nice technique. It's independent completely of all the kinds of systematics that we're talking about for the local distance scale. And conceivably, it could be measured at larger distances where you don't have to worry about peculiar velocities, et cetera, et cetera.

But they turned out to be unbelievably rare. So there was this beautiful object that was discovered in 2017, almost as soon as they tuned on the detachers. They found this object and hundreds of people chased it in the optical. And it was just an amazing. Multi-messeigneur astronomy. Multi-Messager astronomy and the, given how fast that happened, you would predict there would be a lot more objects that have been there. And there have been a single amount like it since. So, I shouldn't be a more statistics.

So that's not going to happen anytime soon. But I really like the method because it's, you know, again, based on fundamental physics, don't have a lot of the systematics that we have to worry about, like dust and calibration. And it will have its own, you know, uncertainties. and that will become clearer when you have a larger sample, too. But it would allow us, I think, to test what we measure. And it's my strong belief that we won't have a Hubble constant to 1% until we have several methods that are precise at the 1% to 2% level. And during the key project that we did with Hubble when it was first launch,

we had five different methods. and the whole philosophy, and coming back to why do we do what you did with JWST, was let's measure several different ways of measuring distances, and then each of those will have its own set of systematics, and some of them will be unknown systematics. I can tell you dust will always make something look fainter. That's a systematic effect. But you discover other types of systematics as you increase your precision

and sort of other effects will pop up out of the noise. And you may not be aware of those until you get better measurements. So until we have several methods at the 1 to 2% level and then can compare them and get a robust estimate of the overall uncertainty, then I don't think the local distance scale is going to be providing the type of, you know, extraordinary claim is required extraordinary evidence. You need extraordinary evidence. And I don't think it comes from one method.

I think it's not going to get it from the satchiates alone. That's why we developed these other two methods. Hey there, students of the impossible. The Hubble tension might be one of the biggest mysteries in the cosmos, but a mystery to me is why so many of you that watch, engage, and love this podcast are not yet subscribed. It's only about 50% of you that are subscribed according to YouTube's analytics or podcast app metrics.

So let's resolve this great tension for me. Just subscribe. Click wherever you're watching on video, click subscribe, and on audio. make sure you follow the show. And don't be afraid to leave an asterism, a small number of stars as a review, no matter where you're listening to this podcast, or if you're watching it, leave a comment and a thumbs up. Now, back to the episode.

I was always curious just about why wasn't the key project led out of a space telescope science institute? How did it come to be led by you and Carnegie and the role that you played in it? And maybe you can take us back. What was the nucleus of it? I should say one of my close friends is Nick Spitzer at UCSD, and his dad, of course, is alignment. And we've played a big role in the nucleation of Hubble itself. And when did it become clear that this was worthy of a key project?

People think about Hubble. They think about all the pillars of creation, the deep field. They don't know because it's maybe not as pretty in the visuals as those objects are. But our subjects were. But how did it come to be? And how did you come to be the leader? Yeah, the genesis of it was actually Ricardo Giacone, who is the director of Space Telescope Sciences to,

even before Hubble was launched. And Ricardo's concern was that if you left the decision of how to allocate the time on the telescope to a group of astronomers, our time allocation committees or tax, there would be a natural tendency to divide up the time into tiny little pieces, because everybody knew this was going to be oversubscribed. We waited for decades, get above the first atmosphere, and it was pretty exciting. So he put together a panel of graybeards as it was coming, at the time and and ask them to consider what were big projects that only Hubble could do.

And if you said, you know, Hubble were to fall into the ocean a year after it was launched, you know, what would never get done from the ground? So what was unique to Hubble? And so they came up with this idea of key projects that got competed. We wrote a proposal for the key project, and we had to, in fact, apply for time every year. We were not guaranteed the time all the way through. And one of the projects that was recommended was the extra-lactic distance scale. And at that time, there was this debate about whether the Hubble concert was 50 or 100,

so a factor of two debate. And so we were invited to compete for that, and we did. And the original leader of the group was Mark Aronso. I was his deputy. And so Mark was tragically killed in an accident. peak in 1987. HUBL was supposed to be launched in 1986 right after what became a challenger, the challenger accident. And so the whole project was delayed. And then in the 1990s, we reproposed. And also, of course, then the spirit collaboration happened. And so our proponent would go

through. We got our first data in December, 1993. And so Rob Kerman, Kenne, get Jeremy Mould and I became co-Pi's and I was the PI in charge of the science end of the project. You see? So Jeremy was management and rob as budget as we put proposal together and but we were closely together. For a long time, Alan Sandidge, or you know, obviously very conversant with his work and famous claim that cosmology was a search for two numbers. Was there a concomitant search for Q-NOT, the deceleration parameter? Did we think about it or was that even on people's minds as part of it?

a key project that Hubble would eventually play a huge role in decipher. It was certainly on people's minds, and Sandidge certainly was interested in K. Not, his second number. And it really wasn't until it became possible to find large numbers of supernovae, and CCDs became available. And then the accuracy with which, again, you could measure velocities of supernovae and actually discover that there was this decline rate dependence and that you could. could standardize them, right? They had a much bigger scatter. So you needed something that would take you out again far enough that you could actually see what was expected to be deceleration at that time and large enough samples of them to actually be able to make measurements. And, you know, unlike sepheids, we can come back. We use some of the same sepheids that were discovered by

Hubble and Stentage and they're still there. It's a real advantage. Supernovae have them once and you're done. And so, you know, as people like Saul Pramutter who discovered or can't, you know, find the idea that you could do this in a batch way, observe them at one time, then follow up another time, new moon, and then find them in large numbers. And this discovery of this relationship between the peak brightness and how fast the supernova declines that really set it going. And then again, CCDs were sensitive at more than one wavelength.

That's what helped us with the sepheed, so that we could. correct for rendering, that was a big part of what we did with the key project, you couldn't do that with photographic plates. So it was both, there was technology really that allowed us to start addressing these questions. If you could order, you know, God to produce a supernova at bridge shift of two or something, like how would it impact cosmology and your research and even, you know, upcoming future research claims about dark energy evolution, how would us supernova, I don't know, What would be kind of the dream you're talking to God now, not just your make. What would you, what would it do?

If anything, take it, take a note of the fact I'm not in the strong words. I think, you know, what we need now are, um, No one goes to Hank's for his spreadsheets. They go for a darn good pizza. Lately, though, the shop's been quiet. So Hank decides to bring back the $1 slice. He asks co-pilot in Microsoft Excel to look at his sales and cost. Help him see if you can afford it.

Copilot shows Hank where the money's going and which little extras make the dollar slice work. Now, Hanks has a line out the door. Hank makes the pizza. Co-Pilot handles the spreadsheets. Learn more at M365 copilot.com slash work. Methods that, so technology again playing a role, right? Infrared helps us enormously. We get rid of the dust, high resolution.

Calibration is really important. It's not exciting, but nature is. giving us a lot of geometric anchors. There are three, maybe four nearby, where we have precise percent or so distances to galaxies. Now we have this mid-range where there's maybe three dozen galaxies, and then you have this problem that the bright ones actually seem to be closer. Is that a systematic effect or, you know, what are we seeing there?

So we need nature to supply us with a larger sample that we can be. comparing apples with apples with enough statistics along the way that we can make these measurements really accurately because what we're doing is, you know, we're starting from, say, our galaxy, sephiids or tip of the red gyre branch stars in the galaxy, and then we move out to galaxies where they've had type 1a supernovae, and we can measure sepheus and tip of the red gyre branch with Hubble, and then we're stepping out to the realm of the type 1A supernovae. And all of the years along the way have to be, you know, at the percent or less level if we're going to claim we've measured H not to 1 percent and we can compare with microwave background.

That's really hard. We're not dealing with things that you can measure with a ruler or meter stick, right? These are astrophysical objects, and it's a challenge. It's that way. So, you know, what I'd like is a distance indicator. That's why I like the gravitational wave sirens that are independent of the things like dust and metallicity and crowding

but then you just don't have them very many yet. So we don't have a perfect distant indicator. You know the maze are beautiful it's a beautiful technique but there's exactly one galaxy in the local neighborhood where it's edge on and you can make this measurement and the next nearest one is 50 kiloparsects

50 megaparsecs, sorry, away. So there's one, right? So if there's systematics in that, we have a way yet of getting to that. Large Magellanic Cloud and Milky Way have different metallicities. With sepheids, you're going to have to correct for that. Some people say there's no metallicity effect, but it has a huge effect on the ultimate zero point.

So it, you know, systematic matter. Explain metallicity real quickly for the audience. It might be a friend of it. Yeah. So we have within stars where you have these nuclear furnaces and you're building up the heavy elements. Eventually when these stars die, either a supernovae or red giants, they put these heavier elements out into the interstellar medium, and then the next generation of stars is formed with a greater metal abundance.

Now, in astronomy, we refer to anything that's heavier than hydrogen and helium is a metal, so that can get... Trauling, that's slightly confusing. But the metals have this effect that in the atmosphere, they're scattering radiation that's coming out from these nuclear processes in the core, and they can make the star, change the star's luminosity. So it's expected that there is an effect on the luminosities of Saffians due to differences in metallicity.

And it's not something that people worried about in the days of the factor of two to be, when we were arguing about 50 and 100. And so imperilies, Barry Maduro, and I did the first test of metallicity in 1990 in the Andromatic galaxy. And we said, okay, we know the Cepheid are all at the same distance. And with CCDs, we were able to correct for reddening for the first time. Was there another effect on the zero point due to metallicity? If we made the measurements at different radial distances in the galaxy,

we knew it had a metallicity gradient, could we see an effect? And we measured, it was 0.2 magnitudes per logarithmic unit of metallicity. but the uncertainty was large and people have been arguing about it same value but some of the studies on the most nearby objects say there's no effect at all

some recent measurements with Gaia say it's twice as large so it's a system at it and the gradient rises because there's more concentration of higher star formation rate near the core and some more processing of nuclear

elements than in the interoperating region, just more star formation, more gets speeded out again, until you get a gradient and jealousy as you go up from the center. You've talked a lot about, in recent talks I've heard you give about accurate cosmology versus precision cosmology. You know, when we describe the kind of desirables of what an astronomer or physicists do, I always say, you know, a systematic is in a fact that decreases your accuracy. You can measure something really precisely, tight groupings.

You've talked about that. but I also often will say at least for us in cosmology and C&B experiments in particular we know we have a systematic from dust that dust is everywhere you know it's I always joke when they you see these studies and like this new compound cures you know baldness and it's always at the end it so they can mice you know so I would say like you know the version of it exactly yeah so there's a meme online where people say well just say mice you know because it's like who knows if it has if you drink 10,000 cups of coffee you know you know in your morning, you're going to die.

Well, how do you know? Because we did this in mice. Well, how do you know? But I always say for astronomers, we just say dust. Like dust is basically the pernicious pain. Dust or magnetic fields. Magnetic fields. Sometimes they're linked together, right?

As they were for us with our claim measurement of inflationary gravitational limits. But I would say to my students, if you have a systematic, that means you have to now build another experiment. And that another experiment is not going to do the science you want to do. It's just going to measure this annoying thing that you didn't want to measure. Is it the same true? astronomy? I mean, you really kind of get to almost throw away the data that you collect

all in an effort to remove this pernicious effects. I mean, it's true that a lot of what you have to spend your time thinking about are the systematics. And if you make your measurement in the optical, you know, which is what Hubble, he didn't know. The photographic plates were only sensitive to blue wavelengths, right? So you make it over and over and over. And that, you know, the effects of dust are huge in blue wavelengths. So yeah, then it had to be done all over. And so, you know, what we were able to show with CCDs is that if you made measurements at multiple wavelengths, you could actually see the effect. You know, there's an interstellar distinction law that depends inversely on the wavelength.

And if you could make measurements at many wavelengths, you could actually measure that and correct for it. And that's what we do. Then you have to worry about metallicity. And then as I said, It's all wrapped up in can you get accurate photometry if your stars are crowded and they're blended with other star. You know, there's another star right under your sephi. You can't measure that, right? It's underneath. So you have to do a statistical correction. And that's...

So I have the old office that once was occupied by Jeff Burbage at UCST. And he and Margaret were alive and kicking for many years when I started at UCSD. And she left a lot of her old photographic plates in his office, which I inherited. So no one's getting, you know, without a fight for me. But I would see things including, you know, galaxies and spectra and, you know, I'm an amateur astronomer, so I'd look them up and I realized that she and Veer Rubin interacted very closely at UCSD for a period about two years when Vera was on leave from another Carnegie Institute of Magnetism, which I don't even know if that exists.

Terrestrial. Does it still exist? Oh, wow. Talk about Vera Rubin in the context of the telescope that bears her name. What is that likely to do for your research and transformative for? for astronomy and cosmology, what are its impacts much way to be? Yeah, it's going to be amazing. It's going to be surveying the sky, you know, covering the southern sky every few nights. That means it would be able to, over time, build up an incredibly deep image of the sky, but also look for transients, things that are changing.

And so, for example, with supernovae, it's likely to find something like a million or so supernovae. And one of the things right now, people have surveys, they do them with different telecomies. they do them with different telescopes, different instruments, try and calibrate them. They put them all together. And there's, again, systematic. So to have a homogeneous sample. So just, you know, for that one example, that's going to be amazing. It'll all be done with the same telescope.

And then you have to follow up the spectroscopy to get the red shifts. But that will be done. And that will be, I think, very important. So, you know, we have our Carnegie Supernova project. It's a smaller project that it was done in a homogeneous way. And then, you know, the Shoes Group has another project. together 18 surveys, right? So you walk big and homogeneous and that.

That's going to come from. Yeah. And then speaking of other technology that you're involved with behind us, and maybe all this overall drop it. No, please don't drop it. Yeah, so one of the kind of, so it's a scale model of the giant Magellan telescope observatory in Chile. When you need to build up your team to handle the growing chaos at work,

use Indeed sponsor jobs. It gives your job post the boost it needs to. be seen and helps reach people with the right skills, certifications, and more. Spend less time searching and more time actually interviewing candidates who check all your boxes. Listeners of this show will get a $75-sponsored job credit at Indeed.com slash podcast. That's Indeed.com slash podcast. Terms and conditions apply. Need a hiring hero? This is a job for Indeed sponsored jobs. And while Serena, I'm not too far away from...

I was honored to... Yeah. Gold-plated. A mock up mirror. So I did witness the construction of it in the early, in the middle of 2019. I was in Chile. And it was very impressive to me. Talk to me about what this instrument's going to do and how it fits in with this other, you know, kind of portfolio of enormous telescopes, extremely large telescopes. There was an overwhelmingly large telescope at one point.

Talk about what GMTO is going to mean for a strong. Yeah. So there are three of these extremely large telescopes. giant a John Telstope is one of them and the overwhelmingly large telescope became the EELT which is the European version. So this one is an 80-foot diameter mirror. You can't tell that from this model.

Each of the mirrors here is 8.4 meters in diameter, 27 feet in diameter. So it's quite a structure. And it will be located in the Andes Mountains in Chile and that the time for first light that we're estimating is early 2030s, the whole mountain has been now leveled, and the structure for the pier is in place. The seven mirrors, all of them now have been cast at the University of Arizona.

And one of the first light instruments is going to be an instrument with very high resolution, spectral resolution, for detection of Earth-mass planets, but it will be extremely exciting. It's a very wide field of view on the sky. So it's not as large as the European telescope, but it has this multiplexing advantage so you can cover a very wide area simultaneously.

And now an international partnership, we started off when I became chair of where we had three partners. We now have, well, 13 now and growing and international partners with Australia, South Korea, Brazil, Weizmann Institute in Israel, and then universities and other scientific institutions across the U.S. So it's moving. We're ready to go if we have this site,

and we're looking to the National Science Foundation for the rest of the construction funding. Yeah, they have to make a decision which where they're going to go. But it's an incredibly impressive. facility. I was joking. They built two. Option for two. You know, it's like when you buy a car and I say, well, you can buy

the undercoding, you know, for free. I guess you need that here in the Midwest. Yeah, so we leveled the mountain in 2012, I think, and we left enough room so that if another telescope project comes along and it wants a really good site, which Lusca Ponosite, there's room for that. That's spectacular. I use the

there, or currently a large Magellan telescope there, which is about the size of one of these sub-mirrors, right? If there could maybe maybe it's slightly smaller snow. Lower than that, yeah. Oh, that's right six meters. Six and a half,

your telescope and these are each 8.4 meters. Yeah. The coolest thing about that is that they have an eyepiece. I think the nascent focus, I've got which focus they use. It is. And they let us look at it. And we saw Ada Karina.

And I felt like, you know, a kid in the candy store. I've been looking through a mirror bigger than the web telescopes prior to the other. No, it's the name. You actually said color at the sign when you're a little bit of an eye piece. And it actually is exactly my height.

So that's great. And there were people there, you know, they were trying to court donors. They didn't appreciate it. I'm like from looking at all these things like a smudge, you know, in an eye piece when you're looking at, you know, M31 for the first time through a two-inch refractor, then looking at them was like, I just wanted to monopolize it for how about it spoiled all of us, right? You see the beautiful color images and people look through the telescope and expect that you're going to see that beautiful color. You just see the smudge, yeah, unless you're looking through a six-meter telescope.

So, Andy, as we wrap up, this part. You know, it's originally named after a saying by the great late Sir Arthur C. Clark, who said the only way of knowing the limits of the possible are to go beyond them into the impossible. So that's the name of the podcast. But he said many other things like for every expert. There's an equal and opposite expert. I like to drop that on my department chair when he's getting a little too out of control. But the one I want to have you react to. And I'm not calling you elderly. But he did say the following. He said when an elderly but distinguish, I'm not calling him that. But you've only been a professor for, you know, you're a young, your new professor. He said when an elderly but distinguished scientist says something is possible, she is very likely to be right. But when she says something is impossible, she is very much likely to be wrong. I want to ask you, what have you changed your mind about over your career or what have you been wrong about, if anything, that you'd pick out to kind of substantiate or even refute that effort? I think I was fairly skeptical about dark energy at the beginning. and that stemmed from seeing what happened with the sepheids and ignoring reddening.

And at the point when people started to talk about it, they hadn't really measured reddening for supernovae, and there weren't very many objects. And until that happened, you know, data are convincing. I want to be convinced by data. And so, but I think, you know, it sharpened things. People then did start to get helpful filters and crack for dust. Beth, you know, the data speak for themselves.

Yeah, it's wonderful. Well, Wendy, thank you so much for your second appearance on the End of the Impossible Podcast. I hope you'll come out. I should say, what more thing are you going to come me out? No, but I was open to the fact that there could be a clobological constant. And there were actually two directors at Carnegie who said to me, we know what the Hubble constant is.

Why are you wasting your time? I mean, literally, that was because we knew what the ages of globular clusters were. That was Sandidge's argument. So the Hubble Constant was going to be 50. to be consistent with the ages of globular clusters. And my strong feeling was we have to measure it. So, I mean, that's been just what I feel. And it's true today.

It's large in the head. And let's measure it well, and it's tough. Currently, that's right. Don't only focus on precision. Wendy Friedman. Thank you so much. It's been a great job. Nice to talk to you.

Thank you. It's great to be here. 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. Own it all. Pay off your home, travel for life, drive a Ferrari.

In celebration of the world premiere of the Monopoly Big Board Buckslot Machine by Aristocrat Gaming, Yamava Resort and Casino at San Manuel is giving one person a $1.6 million dream package. The biggest prize in Yamava's history. Club Serrano members can earn daily instant prizes and secure a spot in the finale May 29th. Don't pass go and own it all.

Only at Yamava, celebrating its 40th anniversary. You win? Details at yamava.com must be 21 to enter. Please gamble responsibly. Monopoly is a trademark of Hasbro. Hasbro is not a sponsor of this promotion.