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--:-- Host: Today Explained, Ram is firm. Yesterday on the show, we brought you the first part of the Unexplainable Podcast's two-parter on the James Webb Telescope. You know what's coming next, so why don't we just get right to it? Okay, Brian Resnick, senior science reporter. Hey.
--:-- Brian Resnick: 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 kind of push this as far as they can. They want to know how far back can they go and what mysterious things can they see when they go there.
--:-- Brian Resnick: 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 did this. But it did so in a kind of radical way. The idea was just to point Hubble at this blank patch of sky for 10 days, which is weirder than it sounds.
--:-- Brian Resnick: Normally, astronomers pick something to study, and then they point the telescope at it. 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.
--:-- Brian Resnick: 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.
--:-- Brian Resnick: 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.
--:-- Brian Resnick: 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.
--:-- Brian Resnick: So this image, when you look at it, it looks like it's two-dimensional. But it really goes deep. 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.
--:-- Brian Resnick: 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 a different strata, you see a few billion years before that, you see galaxies that looked irregular. They look more like footballs.
--:-- Brian Resnick: 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.
--:-- Brian Resnick: 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.
--:-- Brian Resnick: 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.
--:-- Brian Resnick: 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. She's going to use the web to go back hundreds of millions of years, even farther than the Hubble took us.
--:-- Brian Resnick: 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 Caitlyn just trying to go further and further back in time, or is she looking for something specific?
--:-- Brian Resnick: 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's not at all actually We can't see all the way back to the Big Bang just yet.
--:-- Brian Resnick: 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.
--:-- Brian Resnick: 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.
--:-- Brian Resnick: 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?
--:-- Brian Resnick: 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.
--:-- Brian Resnick: 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.
--:-- Brian Resnick: But they still don't know what exactly that light was. And is that what Caitlin'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.
--:-- Brian Resnick: And what kind of, other than just, I don't know, being totally obviously awesome, I mean, what kind of questions is Caitlin trying to answer? Like, what would identifying the first light of the universe be able to help us solve?
--:-- Brian Resnick: So when we identify the first light of the universe, we're really identifying the first galaxies. And like, 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 like why everything is the way it is today.
--:-- Brian Resnick: It's like, you know, if you have an image of evolution of like an animal, you know, you can think of the evolution of the universe similarly. Like you need to see the earlier examples to have a complete understanding of how we got from there to here.
--:-- Brian Resnick: You know, these last two episodes, we've been talking about finding more exoplanets. We've been talking here about finding the first light of the universe. We've talked about all the ways that the web was more advanced than the Hubble and how the Hubble was more advanced than what came before it.
--:-- Brian Resnick: And it just makes me curious about all the things the web 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.
--:-- Brian Resnick: There's always something more. The web 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. But we're not totally in the dark here. Scientists know what a lot of these mysteries are, and they even know how to answer them.
--:-- Brian Resnick: But first, they're going to need some new types of telescopes and new far-flung places doing kind of wild things. And they're just not built yet, so scientists need to get to work. Up next, the mysteries that will still remain after the Webb Space Telescope, and the future telescopes that will try to solve them.
--:-- Brian Resnick: The beginning is the end, and the end is... Unexplainable. Unexplainable, we're back here with Brian. Hey! And we left off talking about the fact that the Webb isn't like the end of all telescopes. Is that there are more mysteries out there that the web just isn't advanced enough to look into.
--:-- Brian Resnick: Yeah, 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.
--:-- Brian Resnick: Let's start with future telescope number one. Future telescope number one would be called HAB-X, which is the Habitable Exoplanet Observatory. And HabEx 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.
--:-- Brian Resnick: This is Sarah Seeger. She's an 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.
--:-- Brian Resnick: 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.
--:-- Brian Resnick: 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.
--:-- Brian Resnick: So is this where HAB-X comes in, the new telescope? Yeah, yeah. So Sarah is one of the scientists who really pushing for this telescope for this concept. And the idea behind this telescope is actually kind of simple.
--:-- Brian Resnick: The Habex Observatory will come in two parts. And one is a telescope, an optical telescope, a lot like the Hubble. 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.
--:-- Brian Resnick: 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.
--:-- Brian Resnick: And so these things would line up just so 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.
--:-- Brian Resnick: 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?
--:-- Brian Resnick: 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 Habex 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.
--:-- Brian Resnick: Yeah, I mean, it's probably likelier that you'll have life on an oxygen planet than on a lava planet, right? I mean, as far as we know, like, we make a lot of Earth-centric assumptions about which planets are habitable and which are not. And Webb could totally, you know, destroy those assumptions.
--:-- Brian Resnick: But at the same time, you know, if life can exist on Earth, like, 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.
--:-- Brian Resnick: 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.
--:-- Brian Resnick: 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 web can. Like before the first light of the universe? Yeah, yeah.
--:-- Brian Resnick: 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 talked 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.
--:-- Brian Resnick: 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.
--:-- Brian Resnick: 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.
--:-- Brian Resnick: 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.
--:-- Brian Resnick: 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 Far Side. Another is called the Dark Ages Radio Explorer. So like the moon is sort of like blocking out radiation and light and things like that?
--:-- Brian Resnick: 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.
--:-- Brian Resnick: 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. And then we've got Farside, which is a potential radio telescope that could take us back before the first light of the universe.
--:-- Brian Resnick: 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.
--:-- Brian Resnick: 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?
--:-- Brian Resnick: 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.
--:-- Brian Resnick: 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.
--:-- Brian Resnick: 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 like detect these waves? Yeah, yeah. We actually have this technology.
--:-- Brian Resnick: 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 like the hot soup phase of the universe.
--:-- Brian Resnick: 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.
--:-- Brian Resnick: 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.
--:-- Brian Resnick: How is that even possible to do? Oh, you know, you put it in space. Okay, makes sense. Yeah, so LISA, it's three satellites that form a triangle, and each side of this triangle 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.
--:-- Brian Resnick: And if it changes, it's because a gravitational wave went by and shrunk or expanded the space. Huh. 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.
--:-- Brian Resnick: 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?
--:-- Brian Resnick: Plans for LISA are underway. The other two I mentioned, they're on like the to-do list and whether what order we get them, you know, 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?
--:-- Brian Resnick: 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.
--:-- Brian Resnick: 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.
--:-- Brian Resnick: 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?
--:-- Brian Resnick: 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.
--:-- Brian Resnick: 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.
--:-- Brian Resnick: Yeah. I just love the idea of instead of thinking about us 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.
--:-- Brian Resnick: 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 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.
--:-- Brian Resnick: How far will it come? And still have to go. How far will it come? Each one tells us how far will it come. This episode was reported by Brian Resnick and produced by me, Meredith Hocknott.
--:-- Brian Resnick: Noam Hassenfeld wrote the music and edited the episode, with help from Jillian Weinberger and Bird Pinkerton. Mandy Nguyen checked the facts, and Christian Ayala was on mixing and sound design.
--:-- Brian Resnick: Special thanks to Joss Fong for sharing audio from her interview with Robert Williams. Joss produced a fantastic video all about the Hubble Deep Field project in the 90s, which you can find in our newsletter.
--:-- Brian Resnick: Lauren Katz heads up our newsletter, and Liz Kelly Nelson is the VP of Vox Audio. You can sign up for our newsletter at vox.com slash unexplainable and email any thoughts you might have about the show to unexplainable at vox.com.
--:-- Brian Resnick: How far will it come? And still have to go. How far will it come? Each one hands us. How far will it come? And still have to go how far we have come each one tells us how far we have come
