Planetary Radio • Feb 02, 2022

Nobel laureate John Mather: The promise of the James Webb Space Telescope

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John mather

John Mather

Senior Astrophysicist in the Observational Cosmology Lab at NASA’s Goddard Space Flight Center, and Senior Project Scientist for the JWST

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Mat Kaplan

Senior Communications Adviser and former Host of Planetary Radio for The Planetary Society

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Bruce Betts

Chief Scientist / LightSail Program Manager for The Planetary Society

The JWST’s instruments have been turned on. Now begins the months-long preparation for observations that will reveal our universe as never before. 2006 Nobel Prize for Physics laureate John Mather is the senior project scientist for the new telescope. He shares his hope for what’s to come and a look back at how this mighty instrument came to be. He and Mat Kaplan also take a deep dive into the origin of the cosmos. Bruce Betts says early risers have a treat waiting for them in the predawn sky.

James Webb Space Telescope at L2
James Webb Space Telescope at L2 This artist’s concept shows the James Webb Space Telescope at a special location in space called L2 located 1.5 million kilometers (932,000 miles) from Earth. There, the Sun and Earth’s gravity balance out in a way that allows Webb to permanently keep the Sun, Earth, and Moon at its back while it observes the cosmos.Image: NASA / Adriana Manrique Gutierrez
James Webb Space Telescope main elements
James Webb Space Telescope main elements The James Webb Space Telescope is composed of three main elements. The Integrated Science Instrument Module houses the science instruments, the Optical Telescope Element includes the mirrors and backplane, and the Spacecraft Element consists of the spacecraft bus and sunshield.Image: NASA / STScI / Loren A. Roberts for The Planetary Society

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Mat Kaplan: Nobel Laureate, John Mather a parent of the James Webb Space Telescope this week on Planetary Radio.

Mat Kaplan: Welcome. I'm Mat Kaplan of The Planetary Society with more of the human adventure across our solar system and beyond. Here's another of those wonderful conversations that remind me of how lucky I am to host this show. John Mather shared the 2006 Nobel Prize for Physics awarded to him for his pioneering work with COBE, the Cosmic Background Explorer Spacecraft. It was COBE that convinced most of the holdouts that our universe began with that euphemism known as the Big Bang. John was already deeply involved with development of what would become the JWST and had been for years. He remains the senior project scientist for the observatory, which turned on its four instruments just days ago. I think you're going to enjoy this interview as much as I did. And I think you'll also enjoy hearing about gold, beryllium and golf balls from Bruce Betts when our chief scientist takes us across the sky for What's Up.

Mat Kaplan: Is that Enceladus at the top of the January 28th edition of The Downlink? It is, but that's not all. They're the plumes we talked about last week on the show and they're the rings seen edge-on. And that tiny companion, it's the moon called Pandora. Really, could you ask for anything more in one image? Thanks, Cassini. Here's more of what you'll find at Several astronomers think they found a medium-sized black hole in our neighbor, the Andromeda galaxy. What's medium? Oh, about a 100,000 times the mass of our sun. Nice profile shot of Andromeda too. And here's a discovery from Curiosity that came too late for my recent conversation with projects scientist Ashwin Vasavada. The Mars Rover has found an isotope of carbon that is associated with life down here on earth. No, it's still not close to being proof, but it's one more way station on the road to learning if we're alone in the universe.

Mat Kaplan: John Mather's more general title at NASA's Goddard Space Flight Center is Senior Astrophysicist in the Observational Cosmology Lab. He has been measuring and probing the cosmos for about half a century. As you'll hear, he was among the first to realize how infrared astronomy could tell us things about the universe that we would never discover within that narrow range of electromagnetic wavelengths we call visible light. Now he and we are mere months away from the most powerful infrared telescope in history beginning to deliver science. He has been on the JWST project from the beginning and can hardly wait to get his hands on that data. It was just a day or two after John and I recorded this conversation for Planetary Radio that I heard from Chris Carberry at Explore Mars. Chris wanted to know if I'd sit down with John a second time for a live February 3rd webinar. I hope you'll join us with your own questions for John if you hear this in time. We've got the registration link on this week's PlanRad episode page at

Mat Kaplan: John, thank you so much for joining us on Planetary Radio. It truly is an honor to talk with you. I already told you, it was your great conversation with your colleague there at Goddard, Michelle Thaller during the deployment coverage that made me think: Shoot, I've got to invite you to be on the show. So it's a great pleasure to have you on today.

John Mather: Well, thank you. I'm delighted to be here with you.

Mat Kaplan: Planetary Radio and The Planetary Society, we have been covering JWST from the start. We share your excitement about its progress and promise. And in fact, it was just a month ago that I was talking with your colleagues, Rene Doyon and Heidi Hammel and Michael McElwain. Last July, more fun than I've had, maybe across the entire pandemic, I got to go to Northrup Grumman and sit on the other side of the glass and talk to people like Bill Ochs about the telescope. I did not really get a feel for the scale of this magnificent new instrument until it was sitting across from me in that clean room. It's all inspiring.

John Mather: It truly is. It is enormous. It is gold. It is beautiful. It is complicated. And it is all folded up or was folded up to go into space on top of a rocket, which to me is one of those terrifying events that we know we have to live with and we design for it, but it's still kind of scary to imagine. You've put your life work and your friends' and colleagues' life work on top of all the explosive material you can find and you push the button and up it goes. And of course, it works perfectly because we've done this before.

Mat Kaplan: But even back in your 2006 Nobel lecture, which I listened to and very much enjoyed, well, first you had a slide about the telescope. And it's almost surreal that all that many years ago, the picture you showed is basically what has now unfolded up there in space. But you even said then that it's a little terrifying to some of your engineer colleagues on the team that this thing would have to unfold like the flower as it has.

John Mather: Yes, of course, it's terrifying. And it's terrifying in different ways for different people. At the beginning, you say we have to conceive the right things so that it'll do the science that we want. Then we have to come to a deal that says, we think we could do that. Then you go through the process of designing it and you have to prove that it's the right design. And then you go through the process of building it. Oh, now we tested it. And finally, at the very end, you have to say: I swear, I know how to make sure this will work because I've tested every single thing that could possibly go wrong. And I'm sure. And that is the most terrifying part because at the back of your mind, are we really sure? But I think we did what we needed to do and we certainly hope so because we were very thorough. We had thousands of requirements to check off, thousands of risk items that we're worried about, thousands of command procedures to rehearse and practice. And we're doing them, as far as we can tell, without mishap.

Mat Kaplan: You must be exceedingly proud of the team that has pulled this off, just to this point.

John Mather: I am, absolutely. I'm in awe of this team. It's so much easier for a scientist to say on the whiteboard, this is what we need to build, than it is to imagine how it's ever going to happen. And honestly, to find out what it really takes to make it happen is awesome and inspiring. And it's this terrifying in, if you say, I never could do that, but a team can do that. So we have.

Mat Kaplan: There were a lot of us at The Planetary Society who compared it to, not so much the Perseverance Rover, but Curiosity, when that concept of a sky crane and seven minutes of terror was new to all of us and JPL pulled it off. And there were some of us who pointed at the JWST and said, "Yeah, except that this is going to be more like seven weeks or more than that than seven minutes of terror."

John Mather: Well, it is a little different though. The thing about the landing on Mars is there's nothing you can do after you've built it and sent it to help. You cannot look at it as it's doing its landing because it takes too long for the information to get home. With Webb, we do have the ability to take our time and watch every single step very carefully. We're actually in touch with the observatory at all times when we're sending important commands. That's what we have when we're close to home as we're only one million miles away.

Mat Kaplan: Only. What is the current status as you understand it?

John Mather: As of today, we have deployed all the mirrors and all of the everything have been put in the right place. So we haven't quite yet started to focus the telescope. We haven't tried to get an image yet. But all the mirrors are where we said we would put them. And we are about to do the final burn that puts us into the Lagrange point orbit. Maybe I say a couple words about that orbit. We do not actually want to go to the Lagrange point because that's among other things, it's in the shadow of the earth. We need solar power, even though that we want to be cold. So we will be orbiting around that point in a giant loop, which takes about six months to go around as seen from here. It's actually a better place to go.

John Mather: And I should say, why did we go to the Lagrange point too? It is that place in the solar system where you're still relatively close to earth, but when you look out from the telescope, the sun, the earth and the moon are all in one direction. That means you can put up your one-sided umbrella and the telescope will be completely protected behind it. It will be cold and dark, which is of course what it takes to do infrared astronomy.

Mat Kaplan: You have made me think of what has become one of my favorite pages on the entire World Wide Web. And it's the dashboard for JWST that actually shows the temperature on the hot side of the telescope of the spacecraft and on the cold side. And the difference between those is already pretty striking.

John Mather: It is huge. Of course, by intention, we need the telescope to be so cold that it does not emit its own infrared light. And so that means the detectors have to be colder than about 40 Kelvin. The mirrors have to be colder than about 50 or 60 Kelvin. All of those things are done passively in the sense that no refrigerator is running to make that happen. But we do have, in addition, one instrument that requires 7 Kelvin. So it does have a compressor for helium gas, and it does go down and expand and cool off the Mid-Infrared Instrument.

Mat Kaplan: I'm going to take a wild guess and guess that's an instrument about which you may have a big interest in the results. Not that you don't have a big interest in the results from all of the instruments.

John Mather: Well, yes I do, but it is special in the sense that it is the most different. You can say the shorter wavelength instruments extend the Hubble observations just to a little bit longer wavelength. And they're very powerful and will show us things we never could have seen before. The mid-infrared one that goes from 5 up to 28 microns is far more powerful than its predecessor, which is on the Spitzer Space Telescope. The Spitzer telescope one mirror is about 85 centimeters across the one mirror that they have. The Webb telescope is six meters or six and a half meters across and it is something like 50 times the collecting area. So we were stunned as astronomers to see how well the Spitzer Space Telescope could see. They were able to see galaxies at a redshift of three or more, even though the telescope was so tiny, relatively speaking. So we knew there was a lot of science to gain by getting a bigger and better one. So they were a pioneer for this subject, as the Hubble was for its shorter wavelength coverage.

John Mather: And so now we know there's an awful lot out there to see. With the mid-infrared, we have the capability of seeing objects that are much cooler than ordinary stars. We have the ability to check whether that little spec that the near-infrared camera might see, is that really a distant galaxy or is that a little asteroid or a little tiny red star close to home? You got to measure these things as you can't just say, I found a red spec. It must be exciting. I have to say, I found a red spec. I've got to know what it is. That's a big challenge actually. The first big project and people said that we had to do in order to justify building the Webb telescope was to see those very first galaxies growing from the Big Bang material. Well, that's really hard. The bigger the telescope, the better. And after you've seen one, how do you know if it is a galaxy?

John Mather: What you should expect to see is one tiny, little, very faint infrared spec, almost without any shape, just almost like a little point object. Well, you got to find out this spectrum. To tell what's in it, you need a spectrum. As our listeners know, spectrum tells you the chemistry and the physics of something that you're seeing. So for an astronomer, a picture is worth a thousand words while a spectrum's worth a thousand pictures because it tells us what's really happening inside. We get the chemistry, the motions, the temperatures, the physical properties of what's inside. And you need to know that to know if the thing you found is primordial. So what's a sign of primordial? Well, it would be a galaxy that has nothing in it, but hydrogen and helium, because that's what we think came from the Big Bang. So, well, if it's got anything else in it, it's not the primordial one. It's the first, it might be a subsequent generation of stars that grew. That's pretty tricky, but it is our job.

Mat Kaplan: If or maybe rather when the JWST reveals the light of those very first galaxies, what do you hope we'll be able to learn from that, from these at least elementally, fairly simple structures?

John Mather: Well, number one question is, are we missing anything from the story? We've got a very wonderful collection of supercomputer simulations of the growth of the first objects and how they grow into modern times galaxies. They appear to grow by tiny things forming first, and then gravity pulls them together in wonderfully dramatic collisions. And it's just super to watch the movies in the computer of how this might have happened. But honestly, you don't know if it's the true story until you go look. So something could be missing.

John Mather: And what could be missing while we were surprised of, as you know, by discovering the acceleration of the universe that we call due to the dark energy. We were surprised by the dark matter, which nobody can see even now. We know it's there because it does something to have deflects the light, makes things orbit differently. So both of those things are big mysteries and we're still having a mystery about even measuring the expansion rate of the universe. We've got several different methods and they're very accurate and precise. And right now they're not agreeing as we expected them to. This is either too much data or a wonderful surprise from nature. So we hope to work that out.

Mat Kaplan: I think you're referring to the Hubble constant, has also shifted since Hubble first came up with that. What, nearly 80 or 90 years ago? Now I forget the exact date.

John Mather: In 1929 was when he published his graph with the expanded universe. And he was off by about a factor of 10 in the expansion rate. And he was off because his evidence was Cepheid variable stars. So Cepheid variable stars pulsate and we knew that the brightness is correlated with a period of variation. How long does the cycle of oscillation take? That tells you the brightness. What he didn't know yet, and it took us a long time to find out was that there are two at least categories of pulsating stars that look a lot alike, but are quite different. So he was fooled, and one kind is about 50 times brighter than the other kind. So that makes a big error. Now that was just to illustrate how hard this job is. There are so many other ways that nature has also fooled us over and over. Before we launched the Hubble telescope, there were still two schools of thought and they differed by a factor of two. And now the current answer is sort of in between. And the answers that we're getting are about 10% apart, which now seems to be extremely important.

Mat Kaplan: Do you expect or do you hope that this telescope will help us to understand the actual nature of dark matter and dark energy rather than just seeing their effects?

John Mather: Good question. Well, the question that could potentially be answered about the dark energy is, is it a constant? Einstein gave us some equations and as a place in him for his constant that describes the dark energy quite well. But that's because it's just a feature of his equations. That's allowed. If there's a actual physical process that the constant is representing, that's a whole other subject. Then it could be a variable instead of a constant. So that's the big open question. And we're working on that collectively. Well, we'll work on that, but so also will some other missions. The Europeans are flying the Euclid mission shortly. And then in about 2026, the US is flying the Nancy Grace Roman Space Telescope, which will also work on it, maybe even better. So we hope to make better measurements and maybe understand better. Now, what other thing you could learn? Well, we don't honestly know what this dark matter particle is, if it is even a particle. We used to think, well, maybe it's a weakly interacting massive particle.

Mat Kaplan: A WIMP, so called, right?

John Mather: A WIMP. So far, every place we've looked where we might be able to find a WIMP. It was too weakly interacting for us to ever find it. So we don't know that it's not that, but we know that it certainly isn't playing with us. So it just those particles, if they're here, they're zooming right through your body as we're sitting here and you can't feel a thing, and nothing that we've done in a laboratory has ever detected a single one of them. There's another category called the axion, which is a theoretical prediction that's, well, you can't argue against it, but we haven't seen it either.

John Mather: People have tried also in the laboratory to make detections of those. And they also refuse to turn up. So either there are dark matter axions and we just can't see them, or that's not the right story either. If they're particles, then a thing you could possibly learn about them is what's the mass of the particle, which you might find out by observing something about where is the dark matter and what is it doing. So there's a hope that we could learn something about them, both by measurements.

Mat Kaplan: Do you expect that we will see that dark matter, even all those billions of years ago has the same influence over what galaxies look like and the fact that they can hold together that it seems to show today, at least in the nearby galaxies?

John Mather: Well, good question. I think so important to remind people that we're here because of dark matter. The story that we tell as astronomers is that dark matter was able to move and cluster itself into structures that would lead into galaxies long before ordinary matter was free to move. We're here because of that. On those pink and blue blobs on the cosmic microwave background maps, most of those are coming from dark matter because there's a lot more dark matter than there is ordinary matter. So that sets up the initial conditions of the growth of structure. So we're here because of the dark matter.

John Mather: And our galaxy spins the way that it does because of dark matter. And we have lots and lots of evidence of dark matter, but we still don't know much about it. We only know what it does. We shouldn't even call it dark because when you say dark, people think black, but this is not black. It doesn't absorb light either. It's just completely transparent and it runs right through you while you're sitting here and you can't feel a thing, you can't see a thing. All we can do is measure the gravitational effects.

Mat Kaplan: Does this also say something and do you expect that the JWST will have more to tell us not just about the formation of these early structures in our universe, the galaxies and maybe their clusters, but also about the creation of the universe itself, that work that has so fascinated you for basically your entire career, the Big Bang and what followed it?

John Mather: Yeah. We may not with this observatory. We're not observing the cosmic microwave background or its details. They've already been very well observed. And there's one more thing that people want to measure about that cosmic background radiation, which is its polarization. There's a pattern of polarization they're looking for, which would tell us about very early times when gravitational waves could have been running through the universe. And if they did, they should have imprinted a particular kind of polarization on that background radiation. There are hints. We are getting close. We may be able to measure some of it from the ground. And we might have to go into space to really be sure. So that's the next big project for that area.

John Mather: But I do want to come back to one thing because we talk about the creation of the universe, but honestly, astronomers don't say the universe was created. We only can tell you the story of how it expands. There is not a first moment. The universe did not somehow spring into being from nothingness. We only have a strange behavior of time as we go back and back towards the earliest moments that you can imagine. The way I tell it is, as you try to imagine backwards to the extreme conditions of early times, when you run out of imagination, that's what we call the Big Bang.

Mat Kaplan: This is a topic I expect we will come back to before the end of this conversation because it has captured you for so long. What is the other science that you are most looking forward to when data starts to flow back to us from the telescope?

John Mather: We are going to look at everything from the first objects that grew from the Big Bang to now. All the steps that would lead to sort of the situation of the solar system, for instance. Not only when we look at the growth of galaxies and see how they change over time, but we'll be looking at stars being born inside those beautiful clouds like the Eagle Nebula or they call it the Pillars of Creation. Stars are being born now. They're being born in the sort of Orion and the middle star there, the Orion Nebula. So all those places are great places for stars to be born, but they are very interesting and frustrating for us astronomers because our telescopes cannot see inside. All those beautiful things that you see are blocking our view. We think of space as empty, but it's actually not. There's dirt and gas in space and the dust grains that block our view. And so the thing that would be the most interesting to know, you can't see.

John Mather: Infrared light has the capability of going around a dust grain instead of bouncing off. So we'll be able to see inside and see stars being born hopefully with planets. So we get some idea how planets are born as well. We have been surprised every year by new things about planets. When I was a youngster, it was imagined that planetary systems must be extremely rare because we had no idea how they could ever be formed. The sort of prevailing theory was, well, it must come from a close collision between two stars. Well, that was wrong. And actually we know that almost all stars have planets now. And that's a totally remarkable result of observations. Now, we still have an interesting challenge though, that we haven't found anything that looks like our solar system. Our solar system is unique in the sense of having a bunch of rocky planets close to the center, and then a gap with a asteroid belt and then some really big gas giant planets outside.

John Mather: Are we missing this in other stars because we just can't see well enough or are there really no other systems like the solar system? So this is getting at the question of, is earth a very special spot? Well, it is in the solar system. We're the only place that has a liquid ocean with continental drift, or the better name for it is plate tectonics. The continents have been zipping around across the globe for billions of years. And that was probably an important part of our planetarium biological history. We happened to get hit by a giant asteroid about 65 million years ago, which changed our own biological history immensely. So our story here on planet earth is of catastrophe after catastrophe and we're still here as the survivors, the lucky survivors of all of that. And maybe that was an essential part of our story. If you say, well, what if those things had not happened, would we be here? You can't answer that question. But maybe not. All of that is a pretty interesting part of our history and I think that's why I'm so excited about learning more about it.

Mat Kaplan: We are certainly very excited about the exoplanet discoveries and characterizations that may might, if we're very lucky, come from this telescope. I mean that possibility, maybe it will take a bigger, even bigger instrument, but what if the JWST finds methane and oxygen in the atmosphere of some world circling another star? I mean, it's hard to imagine anything, more exciting.

John Mather: Well, there will be future things that are even more exciting when we do find signs of life. But for now, I know what we're going to look at. We're going to be looking at about two dozen small planets orbiting small stars, and we'll be able to see, I think if they have water in their atmospheres. We'll be looking at a couple of dozen, I think total of 65 planets altogether, where we know they're going to go in front of their stars and we get a transit. So we can observe the light that comes through the planetary atmosphere on its way to our telescope and do the chemical analysis.

John Mather: So what's in those things? Well, it could be those little planets or just little rocks and they have no atmosphere. Or it could be that there is an atmosphere that's got nothing in it, but hydrogen or oxygen or who knows what's in it, nitrogen. Or it could be that it's full of fascinating molecules than the water one is one of the easier ones to find. So that's why we look for that. We could see some big planets that are more like Jupiter or Saturn orbiting closer into their stars. So we expect lots of surprises.

Mat Kaplan: I'm actually hoping that the telescope will surpass even the expectations of folks like you and find evidence for something like CFCs, chlorofluorocarbons, and we'll know that somebody out there is treating their planet as badly as we do sometimes. Heidi Hammel, who's been here regularly on the show. And as I said, we talked about a month ago. I know that she is also excited about what it may be able to do within our solar system. As you I'm sure know, she's very interested in what's happening in the outer solar system, particularly Uranus and Neptune, and I guess is sometime being budgeted for those studies.

John Mather: Oh, absolutely. We're looking at all the planets from Mars on outwards. And I'm particularly also interested in two satellites that are interesting because of the potential host for life. As everyone knows, Europa is got an ice covering an ocean. When we first heard about that from the Galileo mission that visited, everybody says, that's very cool, but we'll never know what's inside. We'll have to build a nuclear reactor and melt our way in. Then it was more recently discovered and we even have pictures from the Hubble Space Telescope that once in a while, the water jet's kind of spitting out from the cracks between these great blocks of ice. And so we're going to watch them with the Webb telescope. And NASA will fly a mission out there to fly through those plumes of water jets and see if that's only water, or if there's some organic molecules in there, or salt. It could be very salty under there.

John Mather: Then we're going to also be looking at Titan, the satellite of Saturn, which is so big that it has a thick atmosphere, enough atmosphere to support a helicopter. So you probably already know about that, the Dragonfly mission. Yeah, it is fascinating to me. And what makes it specially interesting to me is not just the technology, but the possibility that nature has done an experiment, which is to say, we've got the liquid solvents, we've got the gradients of tap properties, and we've got water vapor and we've got solid water. If there's any possibility for life to be formed based on a different solvent than water, that would be a place to look. So the natural lakes of hydrocarbons, the rain and clouds and all the kinds of things that would give opportunities for life to occur. They're there. I don't think we're going to be able to see any signs of that with the Webb, but it's what makes the whole subject very exciting to me.

Mat Kaplan: Very exciting stuff. We would also point to Enceladus, that moon of Saturn, which we were talking about in the show just last week, which hopefully there'll be a mission to before too many more years.

John Mather: Yes. And there's evidence this week that Mimas has a liquid ocean under the surface as well. So there's an awful lot going out there that we would love to find out more about.

Mat Kaplan: I had not heard of that announcement about Mimas. The universe just becomes more and more interesting. Much more of my conversation with Nobel Laureate, John Mather is moments away.

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Mat Kaplan: I would argue, and I know I'm not alone, that the impact of the images that the Hubble Space Telescope have captured are perhaps as important from the public sense as any of the science that it has delivered. And I wonder if you agree with that and if you think that the JWST will continue that tradition.

John Mather: Oh, I do agree. Pictures are beautiful. People keep them in their houses. They publish books of them. They keep them. I talked to one person who said she had her entire apartment covered with them. It was to kept her sane.

Mat Kaplan: I know a Senator who has one on his wall in Washington, DC.

John Mather: Yeah. Anyway, I am thrilled with those pictures. They are beautiful. And they tell us a story of a little bit about where we came from and what might be. Will Webb do the same thing? I think so. They'll be a little different because that's the point, it's supposed to be different, but beautiful anyway. Why do we make them beautiful? Well, it's partly so that we astronomers can understand them. We get a vast amount of information. You can't process many gigabytes of information to say, well, it means something, until you can make a picture.

Mat Kaplan: It sure does make for some pretty art, that intersection of science and art. I mean, you already mentioned the Eagle Nebula and the Pillars of Creation. Going back to that Nobel lecture that you gave in 2006, one of the things you mentioned, it's very similar to what our boss, the CEO of The Planetary Society likes to say, Bill Nye, that it really all comes down to answering two questions. And the way he puts it is, where do we come from? And are we alone? You stated it in a very similar way.

John Mather: Yeah, it is my big question. I've been interested in this since I was a child. Personally, I have a kind of answer to the are we alone question, which is, I'm sure we're not alone and I'm sure the neighbors are very far away. So I'm sorry to disappoint people. I'm quite sure they did not come to visit. And the reason that I'm sure is it is just space is so large. People don't fully appreciate the impossibility of what we see in science fiction stories.

Mat Kaplan: I'm with you, sadly. I wish we could look to a Star Trek universe where the Klingons are only a few light years away. But maybe that wouldn't be such a great idea, actually.

John Mather: Yeah.

Mat Kaplan: I wonder if you could just say something about your job and what are your responsibilities as senior project scientist.

John Mather: Yes. Well, my job has changed over the years. On the first day, I was the one scientist and there was one manager and we said, we're going to make a project. And what kind of project is it going to be? So then my job was to work with them to say, well, this is possible. And work with scientists to say, this is what we need to make the next big step in astronomy. So there was a little book that was published by a Committee called HST & Beyond, HST is the Hubble Space Telescope. And they outlined what they thought we should build. And this is it. But they were not as ambitious as what we are now. They thought, well, we probably can't afford such a big telescope. They didn't even know that it was logically possible. I sort of suspected that it was. And then as it happened, when the lead author of that was Alan Dressler, he met with Dan Goldin, who was the head of NASA at the time, and they liked each other.

John Mather: But Dan already knew that the work had been done on the larger telescopes that it could be folded up. He knew that from his work in classified world. So, okay. I didn't know that. But when he said we could try that, I said, "Let's try it, of course. That's what we need." And not only that, it will set out a plan for the long term future. We are no longer limited to what fits inside a small rocket, even a big rocket. We're no longer limited to what fits inside. So that's what I was doing in the beginning, working with teams of scientists and engineers. Then our next jobs were to say, well, exactly, please write down exactly what are the requirements, how big does it have to be, why does it have to be that way, what do the instruments have to do, how many pixels, what wavelengths, all those things have to be decided so that somebody can say, yes, I can build that for you.

John Mather: So then working with our managers, we ran competitions and they did all of that. And of course, they set up a procurement process, a formal process for NASA. And we also set up discussions with our international partners who's going to contribute which part. And so that took a lot of backing and forthing before we had an agreement, but it was all settled by about 2002 when we chose the major contractor, which was called TRW at the time, but then was shortly bought by Northrup Grumman. That's how we knew what shape the telescope would be more or less and what it could do. And we also chose the instrument teams at the same time. So then I had a new crowd of scientists to work with. And so we worked with the scientists, engine engineers all this time to make sure we're working on the same project that it's going to do what we all said we meant to do and then all requirements are being met, which is a big project. Now, my job is to cheer.

Mat Kaplan: I suspect it may involve a little bit more than that. You mentioned gravitational waves. I think of the LIGO observatory and all of the other fantastic instruments, ground-based instruments, like the new class of ground-based telescopes, which are currently under construction. ALMA, the Atacama Large Millimeter Array, which I'm always very proud that I got to visit once, which I think you also contributed too.

John Mather: A little bit, yeah.

Mat Kaplan: How will the JWST complement how will it fit into this much broader picture of all these different instruments looking at, well, so much of the electromagnetic spectrum, but even beyond the electromagnetic spectrum now to gravity?

John Mather: Well, we now have a 70 called multi-messenger astronomy, which is if something goes bang, we all want to follow up on it. So when the LIGO Observatory discovered the signs of a collision between two neutron stars merging into a black hole, we thought, well, actually, if that's true, then there should have been a flash of light. And so everybody that had any kind of observatory went to see, as soon as they could, is there something my telescope can pick up? And the upshot was, there were over 4000 authors on the papers that looked at and tried to find and interpret those signals that came from that one flash. That's an example of cooperation between different teams, different observatories. And they all say, start with something that happened and seen by one of them. And we all have to find out more about it. Something like that was amazing.

John Mather: They sort of knew when they built that observatory, the LIGO, that was a possibility that they might find some. But now we know much more about those objects since that was seen. Now we can tell you, not only was it two neutron stars merging, but we're now pretty sure that's where the very heavy chemical elements of the universe come from. So when you look down at your ring, if you have one on your finger and it's gold, that we know most of that gold came from merging neutron stars and some of it fell into the black hole and some of it flew out again and to get recycled into new planets and people. That's an astonishing story. We've got lots of other things that happen out there that have to be followed up.

John Mather: So the Webb will see things that nobody else can see. And that makes an interesting challenge because then that's all we've got. You get a spectrum and a picture from Webb. But if you can possibly follow it up with one of these other telescopes, then you'll know so much more. Sometimes you can get a sharper picture, but at a different wavelength. Sometimes you say, well, I didn't know it was hot enough to emit x-rays or gamma rays. So all of these things follow when you've discovered something odd. So you sort of start with taking a picture and then say, that's funny, what does that mean? Did anybody else see that? Oh, I'll send out a notice to my friends. Pretty soon they're all over it. And if it's exciting enough and you might find of huge discovery.

Mat Kaplan: I think it was Isaac Asimov, who said that "The progress of science is much less Eureka than, hmm, that's funny."

John Mather: Yeah. I think I remember his phrase when I said what I said. He was an amazing and brilliant guy.

Mat Kaplan: Absolutely. I bet that you have also been following the work of the decadal study, the one years ago that led to the development of the JWST and has just issued a new report for the years to come. And we have talked about that on this show and on our sister monthly program, the Space Policy Edition. I wonder if you'd like to say anything about what that study group has recommended now, what may follow the JWST, and for that matter, the Nancy Grace Roman Telescope.

John Mather: My goodness. Well, it's a very ambitious group. I was really pleased that they did not just say, we can't afford anything, so let's not do anything. They said, we have grand ambitions. And they were so grand that they said in the report, we're not ready to say this is exactly how to do it. We think you should take some time and develop the underlying technologies until you really know. They did say what they thought was the next thing that we ought to be working on as the highest priority. And I guess everybody's heard it is a follow on telescope about the same size as Webb, but more accurate and working at shorter wavelengths so that it would be capable of being like a kind of super Hubble with a very special capability of being good enough to see exoplanets orbiting around sun-like stars, which is about the hardest science problem we've defined for ourselves.

John Mather: And it's very difficult because the sun is about 10 billion times brighter than the earth. So if you go in and just point your telescope over there and you see one, you're going to have to get rid of all that starlight to be able to see the little planet. So that's extremely difficult, on the other hand, not impossible. We know roughly what we have to accomplish and how to prove it. So that's what the first step is, is work on that. There were two other categories of great missions proposed, a far-infrared observatory that sees the universe in a very different light. The longer wavelengths are just tell us different things. And the trouble with far-infrared is it's you basically can't do it from here. The atmosphere is almost completely opaque and it also glows. So darn, we just have to have a space telescope to make any progress. The other one was an x-ray mission, which combined a combination of much better detectors with much better telescope. So if you could do that, then the x-ray observations would make a huge jump forward.

John Mather: X-ray sources are interesting because they almost always extremely hot and coming from something extremely compact. So something collapsing right in front of us, something falling into a black hole, the debris from an exploding star like the neutron star in the Crab Nebula. All of those things are hot enough to send out x-rays and they can tell us something we might not have known. There are also interesting things about the very hot plasma in space between the stars. And the possibility of detecting some kinds of dark matter might happen in x-rays. So there's a lot to be learned from either of these kinds of other telescopes. And basically they didn't say, don't do that. They said, just do this one sort of Hubble follow on first, if you can get the technology going, but we're going to work on all three of them. So if I'd been on the committee, that's exactly what I would've said, work on all three of them and this is probably the first one to do.

Mat Kaplan: We've mostly been looking toward the future, at least with the technology, and to the distant past for what these technologies are looking at. But I want to take you back about a half a century ago, maybe even a little bit more when you went into this field and you were working with vacuum tubes and first generation infrared detectors. I mean, you were programming computers with paper tape. What does it feel like to see how far technology has advanced to enable tools like the JWST?

John Mather: I am astonished. I am overwhelmed. I think no one in 1975 could have forecast any of the details of what we've seen. The computer revolution was just beginning. The Fourier transform had just been recognized. Although as it turned out, Georges Lemaître, the cosmologist had invented it first decades before. Nevertheless, I don't know if anybody who had the imagination to see how prevalent the electronics revolution would be. When you can sell an electronic box to practically every person on planet earth, you've got an awful lot of resources to spend on making them better. And that was not something that anyone had really appreciated. It was a big deal to have a pocket calculator that cost $400.

Mat Kaplan: And I guess we could bring up the cliche now about the supercomputer that some of us wear on our wrist.

John Mather: Yes. So when I got to NASA Goddard, there was a computer at my desk and it was a slide rule. It was about that big around, four inches in diameter. And that was a pretty good computer. And people were just beginning to learn how to use computers for anything else. We still were designing of observatories with big pieces of white paper and sharp pencils. And so it is completely incomprehensible even for me that have been there to say, we went from that to this in such a short time. It's almost as big a jump as, well, we didn't know how to fly at all in 1902. And now we landed on the moon, what in 1969. And it only took us about eight years after President Kennedy said we were going to do it. That's even more of a miracle.

Mat Kaplan: Quite an accomplishment, and will always be, should always be regarded that way.

John Mather: And by the way, I just wanted to say, James Webb, the man was the one who did that. He was the second administrator of NASA.

Mat Kaplan: Oh yes, the James Webb.

John Mather: Yeah. The James Webb, the one we named our telescope for is the one who made the Apollo program happened and started up a space astronomy, sent off probes to Mars and to get out of the solar system and started up space telescopes. So we owe him a lot.

Mat Kaplan: It was in that era when you started to think about what might be done with telescopes and instruments in space. Of course, this led to your 2006 Nobel Prize that you shared with George Smoot. When you were describing the earliest days of what now is the James Webb Space Telescope, it made me think of how you describe the beginnings of COBE, the Cosmic Background Explorer that it seemed to start the same way that there were a few of you who said, wouldn't it be great if we could measure this?

John Mather: Yes. It's a kind of conversation that happens between people. I don't know of very many ways that science projects could happen when somebody just goes to the library to think. It's more likely, I've got a problem. Can you help me solve this problem? Oh, well, yes, I could. How about if we try this? And then it goes and goes. So everything I've worked on has always been coming from a conversation of some sort.

Mat Kaplan: Take us back to that. I think, I mean, we throw around Big Bang now. It's just sort of, well, of course that's where we come from. But how controversial was Big Bang Theory back in the mid, still in the mid 1970s when you and others started this work on what would become COBE?

John Mather: Oh my goodness. Well, I think most astronomers understood that the Big Bang was the right picture, the expanding universe, because there was a lot of good evidence for it. We'd seen the cosmic microwave background. Radiation had been discovered in 1965. We had the evidence of the distribution of the primordial chemical elements, the hydrogen, helium, and the tiny bits of lithium and beryllium left over from the Big Bang, and they matched the picture. We had the observations of the expansion rate, even though we didn't really know the piecewise value of the expansion rate. So it all was sort of hanging together, but there were people that said, well, no, I don't believe that. It was called the steady-state theory was the major alternative. It was kind of bizarre in its own way. They said, we don't believe your story, but we have something even more radical to tell you and it's better.

John Mather: And their version said, well, the universe is expanding. We see that. But it's actually in a kind of steady state and it's being replenished by matter being created out of nothing, so that it looks like it's expanding, but it's always been here for an infinite amount of time. So that was their solution to a sort of unwillingness to accept the observations that pointed so clearly in one direction. So when we actually measured the cosmic microwave background spectrum and it work matched the predictions of the expanding universe perfectly, they didn't have much way to hide anymore because their version of the expanded universe with matter creation just couldn't do that. There were other versions too. What if the Big Bang was cold? Well, anyway, then you have to work out what that would look like. None of that worked. So eventually though most of those people gave up, but some of them just died. They never gave up. So that's how it goes.

Mat Kaplan: I don't know who said it, but someone else who said that great new theories of cosmology come into acceptance as the previous generation of cosmologists passes away.

John Mather: It may be true. On the other hand, we don't have that many great new theories coming along. The expanding universe story was a radical departure from anything people had expected. Just to give a little history, now we say, well, Edwin Hubble showed it to us, but it was actually predicted twice before that by Georges Lemaître and before him Alexander Friedmann based on Einstein's equations. It was in there. Einstein didn't believe it. He thought that can't be right. Even after we observed it, even after he saw Hubble's observations, he still didn't really believe it. Only when somebody showed him the error of his theoretical approach did he believe it. That's the story I've heard, which is pretty remarkable. He stood his ground very carefully, but he was wrong. And then he finally said, well, that was my biggest mistake.

Mat Kaplan: Two other slides in your Nobel lecture. One of them, a curve, a plot with data points from COBE that are right on that curve, which was what was predicted, right? What the model predicted.

John Mather: Yeah.

Mat Kaplan: Did this level of data, was that it? Was that the nail in the coffin, so to speak, of steady-state?

John Mather: Well, I thought so, but there's a story there. One of the proponents of the steady-state theory was the chair of this session. When I showed those charts to the astronomical society, that very curve, and we got a standing ovation for the curve. And afterward somebody heard him say, they've swallowed it, hook, line, and sinker.

Mat Kaplan: Such as science. Here's the other thing I was going to mention. The other slide, the second one or the last of the ones that I want to mention from your Nobel lecture. And it makes me so glad that you've already mentioned Georges Lemaître. It's of him and that other fellow, Albert Einstein standing next to each other smiling. When the story that you tell was that Einstein was really rude to Lemaître when he thought he was had come up with the wrong interpretation of Einstein's own theory. But that Einstein did see the error of his ways and apologize. And it just, the two of them standing there after this disagreement just seems to say something so important to me about science and the way it's conducted.

John Mather: Well, it's something we can aspire to. And we hope that we behave ourselves. And but science being carried out by people, we will always have strong opinions. But my motto is, I have to go measure.

Mat Kaplan: John, this has been absolutely delightful as I expected it would be. We will join you in looking forward to first light from the James Webb Space Telescope, which actually might reveal to us first light, the first light in the universe, or at least the first galaxies. I guess, the most fun is still ahead of us.

John Mather: Absolutely. Looking forward to seeing it happen.

Mat Kaplan: Hey, it's time for What's Up on Planetary Radio. Here's the chief scientist, it's Bruce Betts. He's back. Yay!

Bruce Betts: Welcome back and better than ever. Did I go somewhere?

Mat Kaplan: No, I don't see you all week. I mean, this is it. I see you on a little Zoom-like screen. It's Zencastr for anybody who's really curious. But it's just a pleasure. That's all.

Bruce Betts: Yeah. Okay, sure. I haven't gone anywhere in years.

Mat Kaplan: You're like the rest of us.

Bruce Betts: Hey, but you know, I actually go out in the yard and look up at the sky. And when I look up at the sky, what a transition. When I look at in the evening in the west, Jupiter's still hanging on, but it's getting lower and lower. But for those of you up in the predawn, the planet party has really gotten going. We've got Venus looking super bright over in the east and the predawn. Look to its lower right and you can see reddish Mars. And look to its lower left during this coming week or so and you'll see Mercury. So Mercury, Venus and Mars, all hanging out in the predawn east. Venus and Mars getting a little bit closer together and will be hanging out for a little while. Mercury doing its thing.

Mat Kaplan: All of you out there, let me know if you actually get up at 5:30 in the morning to see some of this because I probably won't be joining you, but I do take your word for it, Bruce.

Bruce Betts: Oh, people get up at that time. I just assume the only people who saw these were people who stayed up all night. Yeah. Moving right along. I know, let's talk about dogs. I love dogs, the way they bark, the way their feet skidder and their claws skidder across the floor. But that's not important right now.

Mat Kaplan: I know your dog and that's Canis Major if there ever was one.

Bruce Betts: That was actually Canis Minor making all the noise. Canis Major's a lot more chill. God, I wish I'd named the dogs that. Yeah, that'd be embarrassing. Canis. Anyway, onto this weekend space history. It was this week in 1971 that the momentous Apollo experience of Alan Shepard hitting a golf ball on the moon occurred. And also, oh, by the way, Apollo 14 was on the moon exploring and grabbing samples and doing science. In 1974, Mariner 10 used Venus as a gravity system on its way to mercury. We move on to [inaudible 00:54:46].

Mat Kaplan: That was exactly what the golf ball said after Alan Shepard hit it.

Bruce Betts: Yeah, but no one can hear it. You probably heard a little something about this James Webb Space Telescope, I'm guessing. Yeah. And a couple episodes recently, including very recently. Did you know, you probably knew, Mat, that the mirror is coated in gold, very thin gold, about a hundred nanometers. And you may ask yourself, how does this tie to this week in space history and what would the mass all of that gold together be and what would it be equivalent to? And you know what the answer would be? A golf ball.

Mat Kaplan: Oh, is that right? I'll be darned. Okay. That's actually more than I might have expected.

Bruce Betts: So the coating is about 48 grams when you take all 25 square meters. Anyway, golf ball, that's the end of the golf ball segments for Planetary Radio.

Mat Kaplan: Even better than the gold is the beryllium in my book of the mirrors that's underneath the gold. I think it's just poetic justice that this element that might have been created in the Big Bang is going to be used to look back nearly to the Big Bang.

Bruce Betts: Whoa.

Mat Kaplan: I know I blew your mind.

Bruce Betts: All right. We move on to the trivia question. I ask you what planets have higher surface gravity than earth, where for the giant planets will use the gravity at the one bar about one atmosphere pressure level. How do we do, Mat?

Mat Kaplan: Dave Fairchild got it right. He's our poet laureate. And here's his submission from Kansas. Jupiter, Neptune or gravity giants, they rank one and two on the list. Saturn is next in the heavyweight option. The rings make me glad it exists. We come in fourth on a surface we travel on. I think the gravity is great. Earth has a value in meters per second squared sitting around 9.8.

Bruce Betts: Did not see that surprise ending coming with the gravitational constant value. Okay. Not gravitational constant-

Mat Kaplan: Was that correct?

Bruce Betts: Gravity, sorry, on earth.

Mat Kaplan: Wow.

Bruce Betts: Yes, that's correct. Jupiter, I assume you're going to go through the numbers or shall I?

Mat Kaplan: No, give us the numbers, please.

Bruce Betts: So Jupiter wins big time, 2.36g, where g is the surface gravity on earth. And Neptune is 1.12g. So just a smidgen more than earth and significantly less than Jupiter.

Mat Kaplan: And a lot of people pointed out to us, Uranus came close like Barry Olsen in Alberta and [Marcel Yan 00:57:34] in The Netherlands, it's not quite there, but it's very similar to the force of gravity on the surface of Venus. Uranus and Venus, who'd have thought? What a pair.

Bruce Betts: It's no coincidence. Actually, it is. It's a complete coincidence.

Mat Kaplan: A number of people, including [Hudson Ansley 00:57:53] in New Jersey and [Kent Merley 00:57:55] in Washington. The gravity is at one bar or a little above at Saturn's poles, but at the equator, it's less. Please explain, Dr. Bruce.

Bruce Betts: Saturn is bigger at the equator, and then it is the poles as pretty much all the planets are because they're rotating and being gaseous. It's particularly larger at the equator than the poles. And therefore, because gravity is proportional to one over the distance squared from the center of mass, that distance is larger at the equator than it is at the poles. So the gravity is weaker at the equator than it is at the poles at a similar atmospheric pressure.

Mat Kaplan: Brilliant. Brilliantly done. Thank you for enlightening us with that. Get it? Enlightening us, because we're [crosstalk 00:58:42].

Bruce Betts: Oh, I get it. That's funny. You're such a card.

Mat Kaplan: I haven't told you the winner yet, Jason [Gillette 00:58:51]. Jason Gillette in Ohio, longtime listener. Jupiter, Saturn, Neptune, he says, I was going to try to calculate the surface gravity of a rubber asteroid, but I don't know what's mass or radius. Send one over and I'll do the calculations. Ignore the fact that I don't really understand the math.

Bruce Betts: It's a trick.

Mat Kaplan: Jason, we are going to do that. You can get all those dimensions from the rubber asteroid that we're going to put in the mail to you for winning the contest this week. Congratulations.

Bruce Betts: I can give you the answer. The gravity of a rubber asteroid is tiny.

Mat Kaplan: There it is again. One more poem for you. [Gene Lewin 00:59:29] in Washington. This fundamental physical force that we measure in g's depends upon specific traits, size, mass and density. Of the planets in our solar system, and I'm counting Pluto too, only three exceed our planet's pole. We know this much is true. At the one bar pressure level, all the smaller planets fail. Jupiter, Saturn and Neptune are the three that tip the scale. In the group with lesser pole, an icy giant made the list. Uranus is just not that dense. I hope it doesn't feel dissed.

Bruce Betts: I'm pretty sure Uranus has some other self image issues, at least in the English speaking world. We're ready. Okay. What working spacecraft are at the Earth-Sun Lagrange point 2, L2, working spacecraft at Earth-Sun L2, and by at, I include halo orbits near L2. Go to

Mat Kaplan: How'd you know I was going to ask for that clarification? You have until the ninth, that'll be Wednesday, February 9th at 8:00 AM Pacific time to get us the answer. And here is a unique prize package for whoever makes it through this one, makes it pass with the right answer. You've all heard probably about the movie, Moonfall, which is premiering. I assume worldwide. I don't really know. On the fourth, Friday, February 4th, well, we have a package of swag from that movie. Now I have not seen it. Don't even want to tell you what I've heard about it, but the swag is great. There is a shirt, a t-shirt that says the megastructures club, which I think has a lot to do with the plot of the movie. And there's a baseball cap that says the same. There's a cool silver bag that says Moonfall.

Mat Kaplan: There's a collapsible rubber cup. I guess I should say rubber cup. And what looks like possibly a cork cup warmer, but I'm not really sure from the picture. On top of all of this, I think we're giving away some tickets that will be a part of this package. So you can go off and see Moonfall and then tell us all about it. I hope it will be great fun. I don't have great confidence in the science, but I do hope the movie will be fun.

Bruce Betts: Fun.

Mat Kaplan: I have nothing else to add, except this message that we will accompany with our congratulations to Jason [Hensley 01:02:00] in Texas, who says he took a break from the podcast for a while, as he was enjoying the birth of his son Orion, who he named Orion clearly because he heard me say that's my favorite constellation. Thank you, Jason. And welcome to earth, Orion. We look forward to having you as a listener.

Bruce Betts: Welcome, Orion. And make sure next child, you don't take a break from the podcast because you can listen to it while you're in the delivery room. I mean, the woman you're with will kill you, but next chance you should be willing to take Planetary Radio.

Mat Kaplan: There'll be plenty of time after that, but we do want to get Orion hooked as soon as possible. We're done.

Bruce Betts: Just for the record. I was kidding. All right, Orion, go out there. Look up the night sky. Well, I mean, bundle up, stay warm and hang out with parents. Look up the night sky and think about beryllium, using beryllium to study the Big Bang that created beryllium, and think about Mat thinking about it. Thank you and goodnight.

Mat Kaplan: That's Bruce Betts. He's thinking about it. Well, he's the chief scientist of The Planetary Society and he joins us every week here for What's Up. Planetary Radio is produced by The Planetary Society in Pasadena, California and it's made possible by its noble members. Your award awaits at Mark Hilverda and Jason Davis are our associate producers. Josh Doyle composed our theme, which is arranged and performed by Pieter Schlosser. Ad astra.