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The James Webb Space Telescope – Seeing the First Light · Talking Science

0:00
Usually, you know, when we talk about a time
0:01
machine, there is this expectation of something
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straight out of science fiction. Right. Yeah.
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Like a DeLorean or something. Exactly. A DeLorean
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with all the glowing circuits or some massive
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spinning metal ring generating a wormhole in
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some secret underground lab. I mean, time travel
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is supposed to be this. fundamental violation
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of the laws of physics. It always feels like
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it has to be some impossible manipulation of
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reality. We're so conditioned to think of time
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travel as breaking the rules of the universe.
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Right, but stepping into the world of astronomy
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and astrophysics, you realize we actually have
0:36
a functioning time machine right now. And it
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doesn't break the rules of physics. No, it relies
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on them completely. It really does. So welcome
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to today's deep dive. Today, we are looking through
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a massive stack of sources. We've got detailed
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engineering schematics for a spacecraft. We have
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mission logs from this just... intensely complicated
0:56
deployment phase and several recent research
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papers detailing the early scientific findings.
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It's a lot of material to go through. It is,
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yeah. Yeah. But our mission with this deep dive
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is to understand the beautifully clever design
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choices that allow the James Webb Space Telescope
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to literally see the very dawn of the universe.
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We want to take you on this warm, unhurried journey
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to break down the complex science here. And to
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set the stage for how this instrument operates,
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I mean, we really have to look at what it was
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built to do. So the James Webb Space Telescope,
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which astronomers often just call JWST. Or just
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Webb, right? Yeah, exactly. Just Webb. It's the
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successor to the famous Hubble Space Telescope.
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Which we all know and love. Right. Hubble spent
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30 years showing us the cosmos in unprecedented
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detail. So when they were planning the next generational
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leap, the ambition had to be monumental. further
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away than anything before it. And physically,
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seeing further out into space inherently means
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seeing further back in time, right? All the way
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toward the first stars and galaxies that ever
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ignited. Exactly. But let's unpack the mechanics
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of that immediately because it's so wild. How
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exactly does looking further out into space equate
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to looking into the past? Well, it all comes
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down to a really foundational physical rule,
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which is that light takes time to travel. Even
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though light is the fastest thing in the universe,
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moving at nearly 300 ,000 kilometers per second,
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it is not instantaneous. Okay, so it has a speed
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limit. Yes, exactly. So when you look at the
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moon, for example, you aren't seeing it as it
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is this exact second. You are seeing it as it
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was a little over a second ago. Because that's
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how long the light took. to bounce off the lunar
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surface and cross that distance to your eyes.
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Right. And the sun is about eight light minutes
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away. So you see it as it was eight minutes in
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the past. Wow. Okay. So the further away an object
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is, the longer that light has literally been
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in transit. Correct. If a galaxy is, say, a billion
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light years away from our solar system, the light
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entering a telescope's lens right now left that
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galaxy a billion years ago. We are capturing
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a snapshot of the deep past. That is just incredible
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to think about. It really is. But here is the
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central challenge of this whole mission. To see
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the absolute deepest past, like the very beginning
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of everything, James Webb had to be built with
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one very strange, almost counterintuitive quirk.
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Okay, what is it? To see the oldest light, it
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doesn't use visible light at all. Wait, really?
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We spent... decades and billions of dollars building
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the most powerful telescope in human history
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and we purposely designed it so it can't see
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what our human eyes see yeah pretty much and
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that's because the universe simply won't allow
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us to use visible light for this it comes down
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to a cosmological mechanism called redshift redshift
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okay let's break that down for someone who maybe
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doesn't have a huge science background sure so
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we know that the universe isn't static right
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space itself is actively expanding it's stretching
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out in all directions and as it stretches it
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carries all those distant galaxies away from
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us. Okay, but let me challenge that for a second,
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because this is where cosmology can get kind
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of tricky. If the universe is expanding, how
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do we know the light is physically stretching
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out? Couldn't the light just be, I don't know,
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losing energy over a 13 billion year journey?
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And that's why it looks different to our sensors.
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That is a really logical question. And honestly,
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for a long time, early physicists... debated
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exactly that they called it the tired light hypothesis
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tired light i love that yeah but We know now
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that the light isn't just losing energy or getting
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tired. We observe that the entire spectrum of
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light from distant galaxies shifts uniformly
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in a way that exactly matches the mathematics
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of expanding space. Oh, I see. Yeah, the fabric
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of space itself is the medium that is expanding,
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and the light wave is just embedded in that fabric.
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Ah, okay, so think of it like taking a deflated
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balloon and drawing a tight squiggly wave on
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it with a marker. As you blow that balloon up,
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the rubber itself stretches. Yes, perfect analogy.
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So that tight squiggly line gets pulled wider
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and wider. The peaks and valleys of the wave
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physically spread apart from one another. That
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is an excellent way to visualize the mechanics,
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yeah. Because light travels in waves, as the
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physical space stretches, the light waves get
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stretched out too. Makes sense. So when a light
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wave's peaks spread apart, its wavelength becomes
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longer. And in the spectrum of visible light,
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you know, the colors we can actually see, the
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longest wavelengths are red. Right. So as the
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light from the early universe gets stretched
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over billions of years of transit, it shifts
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toward the red end of the spectrum. Hence the
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name Redshift. But the stretching doesn't just
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stop at red. Right. It keeps going. It does.
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Light that originated from the earliest galaxies
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as ordinary visible light or even ultraviolet
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light has been stretched so much over its massive
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journey that by the time it reaches our solar
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system, it has fallen completely off the visible
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spectrum. Wow. Its wavelength is now longer than
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red light. It has actually become infrared light.
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Infrared. OK. Yeah. And we can't see infrared
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with our eyes, but we interact with it every
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single day. It is the exact same sort of light
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that the human body gives off as warmth. So if
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you want to see the ancient universe, visible
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light is practically useless because it's simply
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not visible anymore. It's been stretched out
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of existence as far as our optical sensors are
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concerned. Exactly. It's kind of like an everyday
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analogy would be like a siren dropping in pitch
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as an ambulance speeds away from you down the
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street. Yeah. But instead of sound waves stretching
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out and dropping in pitch, this is applied to
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the, I guess, the pitch of light waves. That's
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a great way to put it. The pitch of the light
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is dropping into the infrared, so it forces the
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engineering hand. You absolutely must build an
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infrared telescope. Right. But reading through
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these mission logs, it looks like picking infrared
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kind of accidentally solved a massive, completely
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different problem that astronomers were dealing
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with, something about space dust. Oh, yes, it
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did. Infrared has this profound second superpower,
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basically. It slips right through thick clouds
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of cosmic gas and dust. Oh, really? How does
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that work? Well, in the universe, new stars are
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born inside incredibly dense nebulas. To visible
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light, those dust clouds act like thick concrete
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walls. A visible light telescope like Hubble
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can only photograph the opaque outside of the
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cloud, but because infrared light has a much
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longer wavelength, it just glides right past
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those small dust particles. Oh, I love that.
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So by designing Webb to look back into the deep
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past, engineers inadvertently gave it the ability
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to peer into stellar nurseries happening right
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now. It can see through the dust to watch brand
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new stars and planets being born in real time.
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Yeah, it basically opened two entirely different
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doors into the cosmos with one single engineering
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choice. That is just brilliant. But transitioning
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a space telescope to rely on infrared has to
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create a massive mechanical issue, right? like
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you said, infrared light is fundamentally tied
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to heat radiation. It is. So anything that is
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warm is actively glowing in the infrared spectrum.
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Precisely. And that includes the telescope itself.
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Right. If the metal frame or the onboard computers
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or the scientific instruments are even slightly
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warm, they emit their own infrared radiation.
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And you have to remember, the entire purpose
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of this machine is to catch the faintest imaginable
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whispers of ancient heat arriving from the edge
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of the observable universe. So if the telescope
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is warm, It would be like trying to photograph
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a single glowing candle while you were standing
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inside a roaring bonfire. Exactly. The local
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glare from your own heat completely ruins the
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exposure. It drowns out everything else. So how
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do you solve the bonfire problem? To solve it,
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Webb has to operate in a state of staggeringly
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deep freeze. We're talking hundreds of degrees
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below zero. It cannot emit its own heat. Otherwise,
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it just blinds its own sensors. Wow. But, you
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know, if you're listening and wondering why we
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didn't just tuck the telescopes into low Earth
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orbit and let it hide in the Earth's shadow to
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keep it cold, I mean, it comes down to planetary
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heat, doesn't it? It does. The Earth is massive.
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It emits and reflects a tremendous amount of
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thermal radiation. Right. Our planet is basically
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a giant space heater. Yeah. You simply cannot
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park a sensitive infrared instrument that close
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to our planet. It would bake. So Webb had to
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be sent far away from the bonfire. Very far away.
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It operates roughly 1 .5 million kilometers away
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from Earth. 1 .5 million kilometers. To put that
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in perspective for you, that is roughly four
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times further out than the moon. Exactly. But
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it doesn't just float out there randomly, you
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know. It's parked at a very specific gravitational
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location called the L2 Lagrange point. Okay,
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let's break down the physics of L2 because reading
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about this, it is just a brilliant piece of orbital
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mechanics. Why pick that specific spot? Well,
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normally, if you put an object in orbit around
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the sun at a distance of 1 .5 million kilometers
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further out than Earth, It would take longer
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to complete an orbit than the Earth does. Is
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it a wider track to run? Right. It would move
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slower, and eventually it would just drift away
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from us. Okay. But L2 is this incredible gravitational
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sweet spot. At that exact distance, the combined
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gravitational pull of both the Sun and the Earth
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provides just enough extra inward tug to increase
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the centripetal force on the telescope. Centripetal
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force being the inward force needed to keep an
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object moving in a circular path. Right, exactly.
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So because of that extra gravitational tug from
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Earth and the Sun working together, Webb can
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orbit the Sun at the exact same speed that the
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Earth does despite being further away. Oh, wow.
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Yeah, it stays perfectly locked in pace with
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us. It effectively stays in our pocket as we
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both travel around the Sun. It really does. And
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that orbital lock is what completely solves the
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heat problem through pure geometry. Because from
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the perspective of L2, the Sun, the Earth, and
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the Moon... all lie in roughly the exact same
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direction in the sky. Which is the clever alignment
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that makes this whole thing possible. It means
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you only need one shield to blink all three sources
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of heat at once. That is so smart. Webb carries
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the sun shield roughly the size of a tennis court,
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constructed of incredibly thin, highly reflective
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layers. It faces that shield toward the sun,
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earth, and moon. And it just blocks the heat.
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Yep. The shield absorbs and deflects the heat,
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while the telescope itself faces permanently
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out into the freezing void of deep space. It
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operates in absolute frigid darkness. So the
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telescope is literally shivering in the dark,
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perfectly shielded from the heat of our solar
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system. But, I mean, it still has to physically
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gather those faint, stretched -out light waves.
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And to catch incredibly faint light, you need
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a giant mirror. You do. I like to think of it
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like a massive acoustic dish you might use to
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capture a faint whisper across a crowded stadium.
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The wider the dish, the more of that faint signal
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you can corral into your microphone. That's a
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great analogy. Webb needed a mirror over six
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meters across to do this job. But a solid six
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meter mirror is a logistical impossibility for
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spaceflight. Right, because there's no rocket
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payload staring on the planet wide enough to
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hold a single piece of glass that large. It simply
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would not fit inside the aerodynamic cone of
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a rocket. Exactly. So they built it out of 18
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separate hexagonal segments. The origami fold.
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Yes, the origami mirror. These segments had to
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be folded up for launch, packed into the rocket
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like incredibly complex origami, and then once
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it blasted into space, it had to unfold itself.
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It just sounds so risky. It was. Those 18 hexagonal
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mirrors had to swing into place and align in
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the freezing vacuum of space to within a fraction
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of the width of a human hair. They had to act
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as one perfectly smooth, six meter across mirror.
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The precision required is just difficult to wrap
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your head around. But I have to bring up one
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of my absolute favorite details from the sources
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here. The mirror isn't just regular silver glass.
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It is coated in a whisper thin layer of actual
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gold. Yes, it is. Why gold? I assume not just
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to make it look expensive. No, not for aesthetic
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reasons at all. It's because of how gold interacts
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with light at the atomic level. Gold reflects
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infrared light exceptionally well. Normal mirrors,
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like the ones you find in a bathroom, are highly
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reflective for visible light, but they actually
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absorb a significant portion of infrared light.
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Oh, I see. And when you are trying to capture
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a signal that has been traveling for 13 billion
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years, you absolutely cannot afford to have your
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own mirror absorb the data. You need maximum
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efficiency. Gold coating bounces roughly 99 %
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of that precious infrared light directly into
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the sensors. Let me just push back on the clean,
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sterile engineering aspect of this for a moment.
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Because we really have to look at the human anxiety
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of this mission design. It is, frankly, terrifying.
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It was a very stressful time. Right, because
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Webb is 1 .5 million kilometers away. It is far
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too distant for any astronauts to repair. When
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Hubble launched back in 1990 and they realized
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the mirror had a microscopic flaw, we had a safety
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net. Right. We sent a space shuttle up. Exactly.
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Astronauts did a spacewalk and they installed
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corrective optics. With Webb, there are no second
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chances. None at all. The distance makes it completely
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unreachable. That reality must have just dictated
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the entire 30 -year development cycle. Because
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it had to unfold in space, there were hundreds
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of intricate steps. There were. The deployment
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sequence was this massive chain of automated
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events. The tensioning layers of the sunshield
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had to pull tight one by one. Structural booms
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had to extend. Mirror segments swinging out on
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hinges and latching into place. Yeah, it's just
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staggering. If a single cable snapped, or if
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one hinge froze in the cold, the entire machine
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could have become useless space debris. The sheer
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terror of it cannot be overstated. Thousands
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of people dedicated their entire careers to this
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project, waiting 20 years, and then they just
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had to sit in a control room on Earth, watching
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telemetry numbers on a screen, hoping the automated
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sequence worked. No manual override. No manual
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override. But the gamble worked. The deployment
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was flawless. The golden eye opened. Okay, so
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after all of that, decades of design, billions
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of dollars, the nerve -wracking weeks of unfolding,
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what has this golden eye actually bought us?
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Let's look at the payoff. Well, the early scientific
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findings are already incredible. Let's start
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with the deep past, you know, the infant universe.
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Webb has successfully spotted galaxies from just
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a few hundred million years after the Big Bang.
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Which, in the timeline of a 13 .8 billion year
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old universe, that is practically the morning
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after. Exactly. But what's really fascinating
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is that these early galaxies look more numerous
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and much more developed than our cosmological
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models predicted they would be. Oh, really? So
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our assumptions about how quickly the universe
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grew up were wrong. They seem to be, yeah. The
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galaxies appear far more massive and structured
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than the timeline suggests they should be. Some
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people might hear that and think, well, science
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is broken. We failed. No, no, no. That is actually
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how science should work. Finding something that
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doesn't fit your model isn't a failure. It's
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the prize. It forces theorists back to the drawing
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board to ask better questions and build a more
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accurate theory. That makes a lot of sense. Yeah,
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Webb is disrupting our baseline understanding,
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which is exactly what you want it to do. So that
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covers the deep past. Yeah. But reading the research
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papers on exoplanets, it shows Webb is doing
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things much closer to home that feel distinctly
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like science fiction. Oh, absolutely. Exoplanet
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research is thrilling right now. It is essentially
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looking at planets around other stars and acting
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like a remote chemistry lab. That's a great way
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to put it. When a planet passes in front of its
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host star, From Webb's point of view, a tiny
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fraction of that starlight filters through the
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planet's atmosphere. Okay, so the starlight shines
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through the alien air. Yes. And different gases
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in that atmosphere absorb different, very specific
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wavelengths of that light. So by analyzing the
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light that finally reaches Webb, astronomers
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can see chemical fingerprints. That is amazing.
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So Webb is sensitive enough to read these fingerprints
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and tell us what the air is made of on a world
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trillions of kilometers away. It is. It has already
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detected things like carbon dioxide and water
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vapor in the atmospheres of distant exoplanets.
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Which is laying the groundwork to potentially
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find hints of life out there. Potentially, yes.
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It's an incredible capability. I do have to ask
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a natural follow -up, though, and I'm sure you
17:20
listening might be wondering this, too. Does
17:21
this mean the Hubble Space Telescope is totally
17:24
obsolete now? Should we just turn it off? Oh,
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no, not at all. That is the happy answer here.
17:29
They are partners. Oh, OK. Yeah. Hubble sees
17:31
visible and ultraviolet light and Webb, as we've
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discussed, sees infrared. So they aren't competing.
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Right. They're looking at different things. Exactly.
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Together, they build a much fuller, richer portrait
17:42
of the cosmos than either instrument could generate
17:44
on its own. It really is a remarkable synthesis
17:47
of engineering and physics. I mean, wrapping
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this up, the James Webb Space Telescope operates
17:52
as a time machine. And a chemistry lab rolled
17:55
into one. It really does. It's this massive gold
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-plated mirror sitting out in the deep, cold,
18:01
catching stretch light that has been traveling
18:03
since the dawn of space and time. And it's just
18:06
such a testament to human patience. You know,
18:09
people waiting 20 years to see if their life's
18:12
work would pay off just so we can understand
18:14
the universe we came from. It is a profound monument
18:17
to long -term human commitment. And, you know,
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it leads to a really fascinating final thought
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for everyone to mull over. Oh, what's that? Well,
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we've discussed how Webb looks at ancient galaxies
18:27
and reads the chemical air of planets trillions
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of kilometers away. But consider this. What happens
18:34
when an instrument this incredibly sensitive,
18:37
powerful enough to see the dawn of time points
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its golden eye at a patch of space we previously
18:42
thought was completely, utterly empty? If we
18:45
look deep enough into the absolute freezing dark,
18:49
what unseen infrared empires might be hiding
18:52
there, just waiting to completely rewrite our
18:54
place in the cosmos all over again? We built
18:57
a machine to look into the past, only to realize
18:59
the past has an entirely new future waiting for
19:02
us to discover. Thank you so much for joining
19:04
us on this deep dive. See you next time.