What’s the James Webb telescope searching for?
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Last week, NASA released the first color images from the James Webb Space Telescope.

And they're just jaw-dropping. The first image is a picture of thousands of these intricate, beautiful galaxies. And what's truly stunning about it is that this image is of the tiniest patch of sky. It's the equivalent of holding up a grain of sand against the sky at arm's length.

There's a whole bunch of other images, including this enormous orange nebula that sort of looks like a mountain range, except the peaks of these mountains are seven light years tall. It's just been a few images so far, but the web is already showing us things we just couldn't see before. Last year, before the web launched, we made two episodes all about the telescope, how NASA designed it to take these mind-blowing images, and what kind of enormous questions they're trying to answer with it.

So we thought we'd share them with you again this week. This time as one mega episode. We start our story back in 1990, when scientists first put a telescope in space to peer out at the distant universe.

T-minus 10, go for main engine start. We are go for main engine start. T-minus 6, 5, 4, 3, 2, 1, and liftoff of the space shuttle Discovery with the Hubble Space Telescope, our window on the universe.

This was the picture that NASA managers all over the world were waiting for. The Hubble Space Telescope is released. The clearest picture ever seen in the history of astronomy. Scientists expect it will revolutionize our understanding of how far we have come.

and still have to go. How far we have come. 381 miles above the Earth. We see stars, blobs, pillars. Floating in orbit. The Hubble Space Telescope. Each one tells us how far we have come.

When the Hubble Space Telescope launched in 1990, it was a gigantic leap forward. Hubble was something that scientists dreamed about having for decades. Science editor Brian Resnick. On Earth, we can put telescopes on mountaintops, but space...

Putting a telescope in space, that's kind of like the ultimate mountaintop. And from its orbit around the Earth, Hubble revolutionized our understanding of the universe. Hubble taught us that the universe is expanding faster and faster all the time.

It helped us determine about how old the universe is. And this is not a small thing. It's given us these ridiculously beautiful images, the Orion Nebula, the deep field, the pillars of creation. But now we're on the verge of a new era.

This is the future. NASA's James Webb Space Telescope. The Webb, which is launching in partnership with the Canadian and European space agencies, is the most powerful space telescope ever built. It's a grand scientific undertaking. A space telescope so sensitive, it can peer deeper into the cosmos than any previous orbiting observatory. Brian's been talking about the Webb since we launched this show, and he's been speaking to tons of astronomers who all have research projects lined up.

This is really the reason why I wanted to bring it to the show, because this is a machine for answering unanswered questions. I definitely think that Webb will be a paradigm-shifting telescope. We're going right up to the edge of the observable universe. The Webb Observatory.

represents the culmination of decades, if not centuries, of astronomy. We will find things that completely surprise us. It'll give us a view of parts of the universe we've never seen before. Things that fundamentally change the way that we understand the universe. I'm Noam Hassenfeld, and this week on Unexplainable, we'll be diving into the enormous question-answering machine that is the James Webb Space Telescope. How far we've come.

and still have to go how far we have come each one tells us how far we have come and still have to go how far we have come each one tells us how far we have come

Okay, Brian, before we get to some of the unanswered questions that the Webb telescope is going to let scientists try and answer, let's just start with the telescope itself. What makes the Webb so powerful? So I talked to Amber Straughan. She's a NASA astrophysicist. She's worked on Webb for years. And she really pointed out there are two key ways that the Webb improves on Hubble. The first way is really just the size. It's enormous. It's much bigger than the Hubble telescope.

Hubble's about the size of a school bus. Webb stands about four stories tall. It's about the size of a tennis court. So it is absolutely huge. And bigger with a telescope is inherently better? Yeah. So especially when it comes to this kind of telescope, the key component is the mirror. So a telescope mirror, you can sort of think of it like a light bucket. So the bigger it is, the more light it can just collect. Right.

And Webb has this light collecting area that's more than six times bigger than Hubble. And then also the bigger it is, the finer resolution it can see. And not only is it large, it's like a gorgeous golden honeycomb with all these different segments of hexagons. Here, let me send you.

Oh, cool. I mean, this looks like something that I would see in a sci-fi movie and be like, oh, wouldn't it be cool if they made things that looked like that? Yeah, and they did. And because it's so big, there aren't any rockets that are big enough to launch it fully deployed.

So the whole thing has to be folded up to fit inside a rocket. The engineers had to find a way to kind of origami it into a smaller package so it can actually fit on a rocket ship. And then once it launches, it will have to assemble itself in space. I'm sorry, assemble itself? Yeah, it's well supposed to. So that whole process of building a deployable telescope in space is...

is sort of the source of a lot of the engineering challenges. Okay, so the web is super big. What's the second important difference between the web and the Hubble? The type of light it collects.

Webb is an infrared telescope, so that means it sees the universe in infrared light, light that's a little bit more red than what our eyes can see. Hubble can detect visible light, which is what our eyes can see, but Webb can see what's invisible to our eyes.

And as far as all the frequencies of light go, red's at the lower end of the spectrum, right? Like longer wavelengths, lower energy? Yeah, so light comes in a lot of different flavors. So blue would be very high frequency. And then if it gets lower and lower frequency, it gets redder and redder and redder. And then it drops into infrared. And what's the advantage of having a telescope that can see infrared?

This relates to something we were talking about a couple of months ago on our episode on Henrietta Leavitt and the end of the universe. We talked about how the universe is constantly expanding, right? Right. More space all the time. So scientists discovered that by looking at the quality of light coming from different parts of space. And it turned out things that were farther away from us looked redder than the things that are closer to us. This is called redshifting. It's

Space is expanding, and as light travels through space from those distant galaxies, the light is literally stretched by the expansion of space. Imagine a star that's really far away, and the light from that star to get to us has to travel through space. But that space itself is expanding.

And that space is stretching the light until eventually it gets so red, it drops into infrared. And what that means here is that Webb, because it collects infrared light, it can see these very far away things that Hubble just couldn't see. Things that are so far away, the light might have started off in the visible spectrum, but is now infrared.

So the web will literally be seeing things that are so far away that no one's ever seen them before. Yeah, infrared telescopes are really sensitive. And because of that, the telescope has to be very, very, very cold. Because anything that is warm will glow in infrared. You and I, all your listeners, we're all glowing in infrared light. If the telescope was warm, it would just glow and see itself.

So to keep it cold, the web actually needs to be sent really far away from the Earth. Web is going to be a million miles away. That's about four times further than the moon. What? It's going to be at a place where it's shielded from the heat and light of the sun and the Earth. Sorry, four times the distance of the moon? Yeah, yeah, really very far. So this is not going to be orbiting the Earth. This is going to be orbiting the sun.

But also keeping itself in line with the Earth. It's called a Lagrange point. So it's orbiting the sun with us, but like at the same pace that we're orbiting the sun? Yeah, it's pretty wild. That is insanely cool. And when you add all those together, you know, the size of the mirror, the wavelength of light it will see, what we're going to get is a telescope that's about 100 times more powerful than Hubble, if you can even imagine that.

This is a super high-stakes mission. The web, it's going to be nearly a million miles away. And once it's there, we can't fix it. And what's haunting this whole project is that the Hubble needed to be fixed. After it was launched in 1990, the images from it just came back fuzzy. But I am extremely concerned by the fact that after spending almost $2 billion over a 12-year period,

We only now find out that this kind of mistake could occur. And it was kind of this national joke. Have you heard about the problems with the Hubble Space Telescope? A billion and a half dollars, we put up a telescope, and it's out of focus. And so astronauts had to launch on a space shuttle and fix it. Give the Hubble reading glasses, let's speak.

And they could do that because Hubble was close enough to the Earth where you could launch a shuttle and get there and fix it. And they called the NASA official repairman. And he said he'll be up there sometime in the 21st century between noon and five. I just, you build the greatest, biggest telescope that humanity's ever assembled. It's like, oh, it's blurry. Yeah, yeah. But you can't just go and fix the web if it breaks. It's way too far. It just has to work.

So have they been sort of like double-checking everything, like waiting a while to make sure they're not making any reading glasses mistakes? Yeah, it's just taken such a long time to get here. People were talking about the successor to the Hubble before the Hubble even launched. And the James Webb Space Telescope was originally supposed to launch in 2010 and cost around a billion dollars. Now the costs have ballooned to $10 billion, and it's just way overdue.

And they're still planning to launch it, right? That's the plan? The plan is to launch by end of 2021. And this can change. So don't at me if it does change. And then after it launches, you know, there will be some time like it has to deploy, has to do all these things that we talked about. Unfold in space? Yeah, fingers crossed. But then, you know, the science will start. And

This is one of the things that really drew me to the story is that anyone can use the Webb Space Telescope. What do you mean? Like there's like a terminal somewhere that you can walk up to and like check out space? Yeah, put your eye next to it. Put in a quarter? No, anyone in the world can write a proposal, say, I want to use Webb to look at this. Can we use it? Yeah, yeah. I wanted to know too. I asked Amber at NASA. Absolutely. Yeah.

I mean, you might need an astronomer friend to help you out. Should we apply? You know, I looked into it and I think it's a little bit over our heads to do this. Yeah, it's pretty competitive, to say the least. So in March 2021, the Space Telescope Science Institute, which runs the Webb and other space telescopes,

They sent out emails to scientists who had applied to use the web. And these scientists on this day were furiously checking their emails to see if, oh, were their proposals accepted? And it was kind of like all huddling around and finding out who got parts in the school play. It was an exciting day.

We totally felt like underdogs. It feels like a dream. It was honestly a truly amazing feeling. I think I was just stunned for a good minute there. I probably cried a little bit. I'm pretty sure I jumped up out of my chair in my office and shouted out, "Yes!" And Brian, you've been talking to these scientists for the last few months, right? Yeah, I've been talking to scientists who have been awarded time to use the telescope and

These conversations, they just leave me with a big smile. These are people who get to explore the frontiers of the cosmos, and they just have so many unanswered questions. What kind of questions are they trying to answer? Is there life on other worlds? Big one to start with. Yeah. And, you know, they're looking for life and not, you know, necessarily in our neighborhood, like on Mars or Venus, although there are searches for life on those planets.

But they're looking for life on worlds called exoplanets, which are planets that revolve around stars that are not our sun.

So planets in like entirely different systems? Yeah, yeah. And scientists in the last decade or so have detected so many of them. There's just been this exoplanet revolution. But we've detected them with smaller telescopes, and it's just hard to know a lot about them. We just can't study them super well. But that's going to change. The web is going to give us a whole new view onto exoplanets.

I talked to an astronomer, Lisa Dang. She's a PhD student at McGill University, and she's been awarded time on the web to study an exoplanet. This is the first telescope proposal that I ever submitted that was successful. It made me feel like an astronomer for the first time. What kind of exoplanet is she looking at? Oh, this is so rad.

So I was looking down the list of projects approved for the web, and I just stopped at Lisa's because she's going to study one of the most extreme planets we've ever discovered. I want to use the James Webb Space Telescope to look at K2-141b, the lava planet. A lava planet? Yeah, like when we get outside of our solar system, planets can get really weird. It probably looks like hell. Yeah.

So we know this planet is there, but we really don't know much more about it. We just haven't studied it in detail because we just

We just haven't had a big enough telescope. So I asked Lisa to help me imagine what could be there. Oh, I have so many mental images of what this planet could look like. This planet, the first thing to know about it is it's really close to its star. It's so hot on this planet that you could sustain a temperature that would melt the continent on the planet. Anything on that surface is just the hottest thing you can imagine. So instead of having oceans of water like we have here, we have oceans of lava on this planet.

planet. The floor is lava. But then there also could be weirder things. So like this world isn't like an uninteresting place. So things that I'm hoping to look for is maybe clouds on this planet? But they wouldn't be like any clouds you've ever imagined before.

Instead of having clouds of water molecule like we have here, these planets would have clouds made of rock. In these clouds, even if they're made of rock, they can still float because the particles in them would be small enough. It's probably looking pitch black, like dark black cloud. But depending on the shape of these particles, maybe they could be shiny or a cloud of crystals. And then those clouds, they can do cloud things.

We can also have rain from these clouds. It would be raining rock or like raining silicate. It's truly one of the most extreme places we've discovered in the galaxy.

Okay, the lava planet seems really cool and all, but why is the lava planet the place to start if Lisa is trying to search for life? It doesn't exactly seem like a place where there would be life. Yeah, it is a very extreme place if life exists there, which is unlikely. It would be unlike any life that we can think of. But there's a bigger picture reason why she's studying the lava planet. It's because it's the perfect place for her to get really good at atmosphere hunting.

Atmosphere hunting? So we don't know whether these planets even have an atmosphere like we described on Earth. But in order to find life anywhere, we're pretty sure a planet needs to have an atmosphere.

And the lava planet is just this big, hot place that glows in infrared really brightly. So it's going to be really visible for the Webb Space Telescope. So it's just a perfect place to learn how to study atmospheres on other planets and really refine the skills of analyzing them.

So looking at a lava planet is kind of like the first target that you want to try with James Webb before you go towards more temperate rocky planets like Earth, for example. And how exactly would the Webb figure out if a planet has an atmosphere? So what I am hoping to do with the James Webb Space Telescope is basically to observe this planet as it completes a whole orbit. When the planet crosses in front of its star, it will come in between the star and the Webb Telescope.

If there's an atmosphere there, that atmosphere will change the quality of light. So the atmosphere would act as a sort of filter. And then from there, like, Lisa can actually create these whole weather maps of the planet. So is she basically going to have to do this, like, one by one, point the web at every single planet to see if it has an atmosphere? Hopefully she doesn't have to do that all by herself. She's not alone here. She's not the only scientist studying exoplanets. I spend...

most of my time, not quite staring up at the stars, but trying to reveal their secrets. I talked to this guy, Kevin Stevenson. He's a planetary scientist at the Johns Hopkins Applied Physics Lab. It's exciting, right? This is the first step towards answering the question of, are we alone?

He's also been approved to use the web, and he wants to know if he can predict whether planets have atmospheres or not before he even looks at them directly with the web. How would you predict whether a planet would have an atmosphere? So there's actually this really neat pattern that scientists find in our own solar system where...

They look at our solar system and they catalog all the planetary bodies, the planets, the moons, and they see which ones have atmospheres and which ones don't. And it turns out it's just a function of how big the planets are and how warm they are. So this is a really neat trend that we see in our own solar system. And the question is, does this trend apply to systems outside of our solar system? Is it truly cosmic in nature?

There are potentially billions of planets to look at. And if we can just better predict which ones have atmospheres, then we can narrow it down. We're like a step further in the direction of answering the huge question, are there other habitable worlds? And where do we go from there? I mean, where do we go from, okay, these planets have atmospheres to is there life on those planets? Yeah.

Once we have confirmed that a planet has an atmosphere, the web can actually detect things in that atmosphere that might be signs of life or clues that the planet is habitable. We can detect water, CO, CO2, methane. You can ask fascinating questions like, what created that methane? Could it be life? If we want to look for a planet that's

similar to Earth, we would probably want to go out and look for CO2 first. It might sound small, like, oh, analyzing the atmospheres of different planets, but really, this is going to be our first step to that ultimate question of, is there life out there? Is there another Earth-like world? Is there a place that we could live on or something to live on? There's most certainly life out there.

The universe is large, the galaxy is large, there's billions and billions of planets out there. Life has to form. We've seen it form in the strangest places here on Earth, right? The question is, will we know that we're seeing life when we make that measurement? There are just so, so many exoplanets, and we just don't know what's possible on these worlds. And the web is giving us this opportunity to really deeply investigate them for the first time, to...

fill in the coloring book of the planets of the galaxy. It's a very complicated universe. I want to know where we fit into it all. Are we alone? And this kind of enormous ultimate problem of are we alone in the universe is just one of these huge questions that the web can let scientists try and answer, right? Yeah, yeah. Exoplanets are a huge source of unknowns, but there are other huge areas of unknowns too.

Areas that have less to do with traveling through space and more to do with actually seeing back in time. What do you mean? The farther away we look with a telescope, we see older and older light. That light has just taken a really long time to get to us. And we can take these snapshots of a universe like long past, like as it existed billions and billions of years ago. So they're hoping to find the very first light of the universe. Oh boy.

Coming up after the break, cosmic dawn, the dark ages, and what might be the very first starlight of the universe. Support for Unexplainable comes from Greenlight.

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Let's go to space, space, going to space, can't wait, space, space, going, better buy a telescope. Wanna see me? Buy a telescope. Wanna be in space? Space.

Okay, Brian Resnick, science editor. Hey. Before the break, you were saying that scientists don't want to just use the web to look for life on other worlds. They actually want to use it to look back in time. Yeah, yeah. If you look at something that's really far away, the light from it is really old. So something that's 100 light years away, the light from it has been traveling for 100 years.

And so with the web, like scientists are anxious to, to kind of push this as far as they can. Like they want to know how far back can they go and what mysterious things can they see when they go there? Basically, they're excited to take what the Hubble did and just go way further. Hubble was doing this too, sort of like seeing how far it can look back in time. Yeah. Yeah. Hubble, Hubble did this, uh, but it did so in a kind of radical way. Uh,

The idea was just to point Hubble at this blank patch of sky for 10 days, which is weirder than it sounds. Normally, astronomers pick something to study, and then they point the telescope at it. Yeah.

In fact, always what you do is you know what you're looking at. You don't just open the shutter, so to speak, and see what's there. This is Robert Williams. He was in charge of the Hubble in the 90s. But in my case, I thought it was really important to do. I think if you're going to make important discoveries, you've got to undertake risks. And so I told people, look, if we come up with no result, I'll fall on my sword.

But then the picture came back and I should just show you it. Okay. This is the Hubble Deep Field. Oh, I've seen this image before. It's just this square with just tons and tons of little dots of different colors scattered around. I guess those are stars? No, no, no, no, no. Those are galaxies. Oh, okay. So this is just really huge. Yeah.

The fact is, if you look out far enough, you can actually see back in time a timeline that's like a core sample of the universe.

And core sample, that's like when you drill down into the earth and you can see all these kind of past layers of sediment and stuff? Yeah, yeah. So this image, when you look at it, it looks like it's two-dimensional, but it really goes deep. Like you can take this image and sort the objects onto a timeline and see layers in time like you would in a core sample from the earth. So it's kind of like they're on this archaeological dig, but for space.

So nearer to us, like the more recent things in this image, galaxies look gorgeous. They have these elegant spiral shapes. But then if you look deeper in this image and you go to like a different strata, you see a few billion years before that, you see like galaxies that looked irregular. They look more like footballs.

And then even deeper before that, some billions of years before that, they look even like these kind of irregular blobs. And then even deeper, billions of years before that, well, that's when you get to the point where Hubble can just barely make them out and you just don't know exactly what these galaxies look like at all.

So this image of sort of deep space that the Hubble took is almost like showing us these fossils of galaxies? Yeah, like fossils are frozen in time. These galaxies are also kind of frozen in time because their light has taken so long to get to us. And so this image contains almost the entire history of the universe.

So how far back can the Hubble ultimately see? The Hubble could see back more than 13 billion years, which isn't nothing. That's like most of all time. But with Webb, astronomers are hoping to see back even farther. So Webb will allow us to see the faintest galaxies at the edge of the detectable, observable universe. I talked to Caitlin Casey. She's an astronomer at the University of Texas at Austin, and

She's going to use the web to go back hundreds of millions of years, even farther than the Hubble took us. The tiny specks of light in the background of the Hubble Deep Field will brighten and become more detailed. And then we'll get more specks of light even further in the past in the background of the web deep fields. So is Caitlin just trying to go further and further back in time, or is she looking for something specific? Oh...

She's looking for something that just gives me chills. What is she looking for? Cosmic Dawn.

We are looking for the first light that turned on at the very beginning of cosmic time and its impact on its surroundings. Is that the Big Bang? No, no, it isn't at all, actually. We can't see all the way back to the Big Bang just yet, but the universe went through a few phases to get to today. You know, we all go through phases. First, there was the Big Bang, this cosmic explosion.

And then for a while there, like everything was kind of this hot soup. Basically, there was a hot plasma that pervaded all of space. You know, you can think of it like a goopy hot mess. And then the universe cooled a little bit and entered its next phase, where it was dominated by this kind of dense, obscuring fog of primordial gas. There wasn't any light at all.

Scientists call it the Dark Ages. So the whole universe at that point was just dark or invisible? Yeah, but then something happened. That fog lifted. It became transparent. How did that happen? Is that what she's trying to figure out? Do we know...

what allowed us to see light? Yeah, scientists have a pretty good guess at the process that did it. So in science speak, when that fog became transparent, it became ionized. And scientists know what can ionize gas like that, and it's starlight. If you have like a cloud of gas and it encounters energetic light, that energetic light will ionize that gas

and disassociate that cloud. So the idea here is that light itself was the thing that changed the universe from invisible to visible. Yeah.

The darkness of the universe was pervaded by light for the first time. And so if that light just has turned on, then hits that gas and really transforms the entire universe from a dark place to a light place. But they still don't know what exactly that light was. And is that what Caitlyn's going to try to look for? Oh yeah. She's looking for the first stars, the first galaxies that transformed our universe.

We're trying to see which galaxies turned on first. And what kind of, other than just, I don't know, being totally obviously awesome, I mean, what kind of questions is Caitlyn trying to answer?

What would identifying the first light of the universe be able to help us solve? So when we identify the first light of the universe, we're really identifying the first galaxies. And once we understand where those first galaxies are, that helps us understand the distribution of matter and dark matter in the early universe.

We want to know why everything is the way it is today. It's like, you know, if you have an image of evolution of an animal, you can think of the evolution of the universe similarly. You need to see the earlier examples to have a complete understanding of how we got from there to here. You know, it just makes me curious about

all the things the Webb can't do and what might come next. I mean, we know that this is like the most advanced, coolest telescope humanity's ever built, but there's got to be a next telescope, right? Oh, yeah. There's always something more. Webb won't be the last space telescope.

There's always going to be more questions to answer, questions that even the web can't really get at. So I've been talking to a lot of scientists, and I've heard about three really cool telescopes that really can push past a lot of the boundaries of what the web can't do in really interesting ways.

Okay, three potential cool future telescopes. Let's start with future telescope number one. Future telescope number one would be called HABX, which is the Habitable Exoplanet Observatory. All right. And HABX is all about finding an Earth twin.

We could find a planet like Earth around a star like our sun and recognize it as such. This is Sarah Seeger. She's a MIT planetary scientist whose work is all about finding these other Earths. I love to describe my job as I am searching for aliens. So a big limitation of the web is that although it can see all sorts of cool planets, typically they'll be around dimmer stars. Oh, so the lava planet is around...

A dimmer star? Yeah, yeah. And really, there's no shortage of these planets that revolve around dimmer stars for us to explore with the web. But finding another Earth around a star like our Sun would be a lot harder because stars like our Sun are just so bright. Earth is 10 billion times fainter than our Sun. And planets that are close to stars that are so bright are just really hard to see. So if we want to go out and search for the Earth Twin,

we need to go to the next level, to a different kind of telescope. So is this where HAB-X comes in, the new telescope? Yeah, yeah. So Sarah is one of the scientists who's really pushing for this telescope, for this concept. And the idea behind this telescope is actually kind of simple. Okay. The HAB-X observatory will come in two parts. And one is a telescope, an optical telescope, a lot like the Hubble. Okay. But the key is the second part.

It's like an umbrella that floats alongside the telescope. Literally, we want to put up a giant, specially shaped screen called Starshade. Starshade? Yeah, it's actually really well named. So the Starshade exists to be perfectly aligned with the telescope and the star so that it blocks out some of that light from the star. Starshade would be in space far away from Earth, and it would operate together with the space telescope. And so these things would line up just so.

And that we'd be able to see other Earths or other Jupiters or other planets, whatever's there. I almost imagine like an outfielder in baseball trying to catch a pop fly putting up his glove to block the sun in order to see the baseball. Yeah, so the star shade is like that, but it's enormous. It's tens of meters in diameter. And so it looks like the silhouette of a giant sunflower. And would this just be about spotting these planets or would it be about like...

learning more about them. Yeah, so like the web, it would be able to determine the composition of the atmosphere. And it would be capable of detecting oxygen on these planets, which the web just, it's not really well suited to detecting oxygen. And if HabX and Starshade find a planet with oxygen, I mean, well, that's not like a perfect sign of life, but it sure raises the possibility. Yeah, I mean, it probably...

likelier that you'll have life on an oxygen planet than on a lava planet, right? I mean, as far as we know, we make a lot of Earth-centric assumptions about which planets are habitable and which are not. And Webb could totally destroy those assumptions. But at the same time, if life can exist on Earth, we should look for Earth-like planets. When you look up at the night sky and you see all the stars up there, you can wonder what's out there.

You know, we can nearly guarantee that the star you're looking at has planets. And to me it's amazing to think that we can learn something about that planet. Maybe not all the details that Earth has, but we can learn something and know about a world far away.

Okay, so that's one potential future telescope, HAB-X, with this starshade umbrella to block out the star. Yeah. What's another future telescope that could kind of take us past the limits of the web? So astronomers want to build telescopes to look even farther back in time than Webb can. Like before the first light of the universe? Yeah, yeah. It's kind of audacious that we can even think we can do that, but it's possible. This is still something that astronomers dream of,

being able to do someday. I talk to Paul Hertz. I'm the director of astrophysics at NASA. And he tells a story about what scientists think happened before that first light of the universe. When the universe was first created, it was so hot after the Big Bang, it was so hot that atoms couldn't exist. It was just a plasma of subatomic particles. So this was the post-Big Bang hot soup phase you were talking about earlier? Yeah, yeah. And then came the Dark Ages.

We can't see with light that part of the universe. But there are telescopes that can detect things that are not light. And in the Dark Ages, there were all these hydrogen atoms that were emitting these really faint radio waves. So if you build the right kind of radio telescope, very large, very sensitive, then you would be able to detect the radio waves and we could study the universe before the first stars and first galaxies.

And to do this, you would build a giant radio telescope on the far side of the moon. So this is the side of the moon that never faces the Earth. And this is a real idea. There's a couple of designs out there. One is called Farside. Another is called the Dark Ages Radio Explorer. Ah.

So like the moon is sort of like blocking out radiation and light and things like that? Yeah, so these early, early radio waves, they're super faint. It's just way too noisy here to hear them. We generate tons of radio noise. But the entire moon could act as this giant shield. Sure, it's thousands of miles of rock. So the radio waves can't get through that.

Okay, so we've got Starshade, which allows that first potential future telescope to block out the sun and see kind of Earth-like planets. Yeah. And then we've got Farside, which is a potential radio telescope that could take us back before the first light of the universe. What is the third potential future telescope that could take us past the web? Oh, this third one is so cool. We could go back even before these radio waves. How far back?

Nearly all the way back to the Big Bang itself. Okay. So this telescope concept is called LISA, the Laser Interferometer Space Antenna. Nice acronym. Yeah, let's just stick with LISA. Okay, so how would this telescope take us back before radio waves?

So, so far we've been talking about telescopes that, you know, quote unquote, see different forms of electromagnetism, optical light, infrared, radio. These are all electromagnetism. LISA is a telescope that would detect waves of gravity. Okay.

Yeah, yeah. It's a little weird, but just like waves can form in the ocean, they can form in the fabric of space itself. Okay. So imagine if some black holes slammed into each other. That collision is so massive that it can shake space. So it'll be like flapping space. And space will propagate that movement as waves. Anything within that space...

will warp. Things will shrink. They'll be stretched out. It's like looking at a funhouse mirror, but we are in the mirror, so to speak. And can we see ourselves getting all wobbly and circusy or at least detect these waves? Yeah, yeah. We actually have this technology. So in 2015, scientists detected gravitational waves coming from two black holes colliding.

And they could potentially detect gravitational waves from right after the Big Bang, from the hot soup phase of the universe. During that period when the universe was opaque, it was very thick and hot plasma, there were pressure waves moving through it. And that pressure makes matter move back and forth, which creates gravitational waves. These gravitational waves are...

You'd probably guess they're really faint. And so we would need a massive detector. So we need to have a gravitational wave observatory where the two ends of it are a million kilometers apart. Sorry, one telescope system observatory thing that has ends that are a million kilometers apart? Yes. How is that even possible to do?

Oh, you know, you put it in space. Okay, makes sense. Yeah, so LISA is, it's three satellites that form a triangle, and each side of this triangle, like, is more than a million kilometers long. And it sends lasers back and forth, and it measures whether the distance between the satellites has changed. And if it changes, it's because a gravitational wave went by and shrunk or expanded the space. Hmm.

So is this basically as close to the Big Bang as we can get? Could we ever get further than this? Yeah, this is probably the limit for now. Certainly the history of science says that many times we have thought something was unmeasurable or unknowable until somebody came along that was smart enough to figure out how to measure it and how to know it. Zooming out here for a second.

How realistic are any of these telescopes? Are these just like thought experiments or are any of these actually in the works? Plans for LISA are underway. The other two I mentioned...

They're on the to-do list, and whether what order we get them is still yet to be determined. So is this last telescope, LISA, is this sort of like the ultimate telescope, the most powerful telescope we can think of? You know what? It's funny. We've been talking about telescopes in terms of upgrades, like it's an iPhone, but really... There's no...

perfect or universal telescope. Each telescope, whether it's on Earth or in space, is designed to do a particular kind of science. So LISA would be really great at hearing these primordial gravitational waves, but it would just be blind to some other things like starlight. And this is just the trade-offs you have to decide in making telescopes. You can build a telescope that's great at one thing, but it'll probably be lacking in something else.

When scientists are thinking about constructing these future telescopes and weighing them against the current benefit of the Hubble or the Webb, are any of them asking the question of, like, why? I mean, is it just like a self-evident question that we would want to understand more and see further and build better telescopes? Or is it just sort of like...

trying to accumulate more knowledge for knowledge's sake, just trying to understand who we are and where we came from. Actually, I got this fascinating answer from Caitlin Casey. She's the UT Austin astronomer, the one who wants to look for the first light of the universe. She told me, if you look back to the Big Bang, to the Dark Ages, the cosmic dawn, the creation of stars, galaxies, planets...

We are a consequence of this. We can't see ourselves as being apart from this. We are of this. Humans trying to understand the universe is really the universe trying to understand itself. Yeah. I just love the idea of instead of thinking about

as humans understanding the universe. I love the idea of thinking of ourselves as like stardust and just composed of the same materials as the universe and we're all just the same thing understanding itself. That just seems really beautiful to me. Yeah, like the universe has built telescopes in a way. And I really sense there's this virtuous cycle here. So as we generate energy

what will be incredible images from the web and from other telescopes, we're only going to inspire more people to be curious and to get in and on this virtuous process of the universe becoming self-aware. If you're listening to this episode and you're like, I need more podcasts about space, then you're in luck.

Check out our series from last month called Lost Worlds. It's all about some of the wildest mysteries buried in the deep past of our solar system. We've got episodes about what killed Venus, whether there could be life on Mars, how the moon was formed, and whether there was a civilization on Earth before humans. If you want to learn more about the Webb telescope and the images that we're starting to get back from it,

Our friends over at Today Explained caught up with Amber Strawn from NASA to ask her all about it. Check out their episode, which is out this week. This episode was reported by Brian Resnick and produced by me, Meredith Hodnot. Noam Hassenfeld wrote the music and edited the episode with help from Jillian Weinberger and Bird Pinkerton. Mandy Nguyen took the facts. Christian Ayala was on mixing and sound design. And the rest of the Unexplainable team includes Catherine Wells and Richard Seema.

Special thanks to Joss Fong for sharing audio from her interview with Robert Williams. Joss produced a fantastic video for Vox all about the Hubble Deep Field Project in the 90s, which you can catch on Vox's YouTube channel. If you have any thoughts about this episode or ideas for the show, like please email us. We want to hear from you. You can find us at unexplainable at Vox.com. Unexplainable is part of the Vox Media Podcast Network.

And we'll be back next week.