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The Telescope That Sees the Beginning of Time · Night Science Stories

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  Speaker 1: Good evening and welcome to The Sleepy Scientist. I'm very
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  Speaker 1: glad you've found your way here tonight. Before we head
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  Speaker 1: tonight has found you, I hope you're comfortable. The lights
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  Speaker 1: journeys through science help you relax, then a like or
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  Speaker 1: joining me for a while already, thank you for continuing
• 0:51
  Speaker 1: to spend part of your evenings here. It genuinely means
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  Speaker 1: a great deal. Tonight, though, we're going somewhere unusually far away.
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  Speaker 1: So far, in fact, that looking across the distance means
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  Speaker 1: looking billions of years into the past. We're going to
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  Speaker 1: follow one of the most ambitious machines humanity has ever built.
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  Speaker 1: A telescope sitting alone in the darkness more than a
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  Speaker 1: million kilometres from Earth, collecting light that began its journey
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  Speaker 1: before our planet even existed. Hopefully, that is a suitably
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  Speaker 1: peaceful thought to fall asleep to. and if you happen
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  Speaker 1: to stay awake for all of it, at least you'll
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  Speaker 1: know why 18 golden mirrors, a sunshield the size of
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  Speaker 1: a tennis court, and several decades of engineering were needed
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  Speaker 1: simply to look at some very faint points of light. So,
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  Speaker 1: get comfortable, and we'll begin. How can a telescope look
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  Speaker 1: so far into space that it begins to show us
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  Speaker 1: the earliest chapters of the universe? There is something slightly
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  Speaker 1: strange about looking up at the night sky. something so
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  Speaker 1: ordinary that it is easy to forget it is happening
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  Speaker 1: at all. Whenever you look at the moon, the sun,
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  Speaker 1: a star or a distant galaxy, you're never seeing it
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  Speaker 1: exactly as it is at that moment. You're seeing it
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  Speaker 1: as it was. The reason is simply that light takes
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  Speaker 1: time to travel. Light moves extraordinarily quickly through empty space,
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  Speaker 1: at roughly 300,000 kilometres every second. On human scales, that
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  Speaker 1: is so fast that it seems instantaneous. Switch on a
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  Speaker 1: lamp across a room and there is no noticeable pause
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  Speaker 1: while the light crosses the distance. As far as our
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  Speaker 1: senses are concerned, the room simply becomes brighter. But the
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  Speaker 1: universe is rather larger than a room. Once distances begin
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  Speaker 1: stretching across hundreds of thousands, millions and eventually trillions upon
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  Speaker 1: trillions of kilometres, even light needs time to complete the journey.
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  Speaker 1: Consider the Moon. It hangs in the night sky looking
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  Speaker 1: close enough to touch, at least compared with almost everything
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  Speaker 1: else in astronomy. Yet the Moon is roughly 384,000 kilometres
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  Speaker 1: away from Earth. Light reflected from its surface takes about 1.3
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  Speaker 1: seconds to reach us. So when you look at the Moon,
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  Speaker 1: you are actually seeing the Moon as it was a
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  Speaker 1: little over one second ago. That is hardly ancient history.
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  Speaker 1: There is not much the Moon is likely to have
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  Speaker 1: done in the meantime. but the principle is important. Now
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  Speaker 1: look towards the sun. The average distance between Earth and
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  Speaker 1: the sun is roughly 150 million kilometres. Sunlight needs a
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  Speaker 1: little over eight minutes to cross that distance. Every sunrise,
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  Speaker 1: every patch of sunlight falling through a window, and every
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  Speaker 1: warm afternoon outside is produced by light that left the
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  Speaker 1: sun more than eight minutes earlier. If the sun could
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  Speaker 1: somehow suddenly vanish... which thankfully is not something stars simply
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  Speaker 1: decide to do on a quiet afternoon, Earth would continue
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  Speaker 1: receiving its light for a little more than eight minutes.
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  Speaker 1: Astronomy becomes stranger as we move farther away. The nearest
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  Speaker 1: star system to the Sun, Alpha Centauri, lies more than
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  Speaker 1: four light years from us. That means the light arriving
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  Speaker 1: from it tonight began travelling towards Earth more than four
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  Speaker 1: years ago. A light year is not a measurement of time,
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  Speaker 1: despite the name. It is a measurement of distance. One
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  Speaker 1: light year is the distance light travels through space in
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  Speaker 1: one year, almost 10 trillion kilometres. Many of the stars
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  Speaker 1: visible with the naked eye are tens, hundreds or even
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  Speaker 1: thousands of light years away. Their light began its journey
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  Speaker 1: long before it entered your eyes, and once telescopes begin
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  Speaker 1: looking beyond the Milky Way, the delay becomes enormous. The
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  Speaker 1: Andromeda galaxy is roughly 2.5 million light years away. When
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  Speaker 1: we observe Andromeda, we see light that left it roughly
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  Speaker 1: two and a half million years ago, long before modern
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  Speaker 1: humans appeared. More distant galaxies carry us much farther into
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  Speaker 1: the past. Some are seen as they existed billions of
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  Speaker 1: years ago, when the universe itself was dramatically younger than
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  Speaker 1: it is today. Astronomers describe this idea using the term
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  Speaker 1: look-back time. It is one of the foundations of observational cosmology.
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  Speaker 1: the study of the universe on its larger scales and
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  Speaker 1: across its history. In general, the farther away astronomers observe,
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  Speaker 1: the farther back in cosmic history they are able to investigate.
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  Speaker 1: This does not mean that a telescope physically travels backwards
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  Speaker 1: through time. Nothing inside the telescope is reversing the flow
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  Speaker 1: of history. The telescope simply waits for information that has
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  Speaker 1: already spent an enormous amount of time travelling across space.
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  Speaker 1: A photon leaving a distant galaxy does not know that
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  Speaker 1: anyone is waiting for it. It simply travels onwards. It
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  Speaker 1: may cross empty intergalactic space for millions or billions of
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  Speaker 1: years before eventually entering a telescope and being detected. That
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  Speaker 1: makes almost every astronomical observation a historical record. A telescope
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  Speaker 1: pointed at a nearby planet may be looking a few
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  Speaker 1: minutes into the past. A telescope aimed at a nearby
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  Speaker 1: star may be looking years into the past. A telescope
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  Speaker 1: studying a distant galaxy may be looking billions of years
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  Speaker 1: backwards through cosmic history. In that sense, every telescope ever
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  Speaker 1: built is a kind of time machine. The James Webb
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  Speaker 1: Space Telescope takes that idea to an extraordinary extreme. Its
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  Speaker 1: enormous mirror and highly sensitive infrared instruments were designed to
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  Speaker 1: collect incredibly faint light that has travelled through the universe
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  Speaker 1: for more than 13 billion years. Some of the photons
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  Speaker 1: it detects began their journeys when the cosmos was only
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  Speaker 1: a small fraction of its present age. They have been
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  Speaker 1: travelling almost ever since, and so the night sky is
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  Speaker 1: not really a single picture of the universe at one moment.
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  Speaker 1: It is a collection of different moments layered across the darkness.
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  Speaker 1: The moon belongs to a little over one second ago.
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  Speaker 1: The sun belongs to more than eight minutes ago. Nearby
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  Speaker 1: stars belong to years or centuries ago. Distant galaxies belong
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  Speaker 1: to epochs that ended billions of years before anyone on
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  Speaker 1: Earth could have looked up to see them. The deeper
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  Speaker 1: we look into space, the older the light becomes, and
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  Speaker 1: with a telescope powerful enough, cold enough, and sensitive enough,
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  Speaker 1: that ancient light can carry us astonishingly close to the
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  Speaker 1: first luminous chapters of the universe. If looking farther away
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  Speaker 1: means looking farther back in time, then there is an
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  Speaker 1: obvious question waiting at the end of that idea. How
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  Speaker 1: far back can we actually see? The universe is approximately 13.8
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  Speaker 1: billion years old. That is the scale we are working
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  Speaker 1: with when astronomers talk about the earliest galaxies, the first stars,
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  Speaker 1: or the beginning of cosmic history. The James Webb Space
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  Speaker 1: Telescope can see extraordinarily far into that past. But there
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  Speaker 1: is an important distinction to make. It cannot literally see
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  Speaker 1: the beginning of time. No ordinary telescope can simply point
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  Speaker 1: toward the Big Bang. and take a picture of the
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  Speaker 1: instant everything began. The problem is not that our telescopes
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  Speaker 1: are still slightly too weak. The problem is that for
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  Speaker 1: a long period after the universe began, light could not
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  Speaker 1: travel freely at all. The early universe was extremely hot,
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  Speaker 1: extremely dense, and filled with a rapidly interacting mixture of
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  Speaker 1: particles and radiations. In those early conditions, electrons were not
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  Speaker 1: yet bound to atomic nuclei in the stable atoms that
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  Speaker 1: fill the universe today. Instead, matter existed largely as an
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  Speaker 1: ionised plasma containing free electrons and positively charged nuclei. Photons
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  Speaker 1: trying to move through this environment were constantly scattered by
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  Speaker 1: those free electrons. So although light existed, it could not
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  Speaker 1: travel across great distances in a straight, uninterrupted path. The
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  Speaker 1: young universe was, in effect, opaque. You could imagine something
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  Speaker 1: a little like trying to shine a torch through extremely
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  Speaker 1: thick fog. The photons are there, but they are scattered
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  Speaker 1: again and again before they can travel very far. This
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  Speaker 1: changed roughly 380,000 years after the Big Bang. By then,
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  Speaker 1: the universe had expanded and cooled enough for electrons to
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  Speaker 1: combine with atomic nuclei, producing electrically neutral atoms. mostly hydrogen
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  Speaker 1: and helium. This transition is known as recombination. Once large
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  Speaker 1: numbers of free electrons disappeared into atoms, photons were suddenly
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  Speaker 1: able to travel much more freely through space. For the
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  Speaker 1: first time, the universe became transparent on enormous scales. Some
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  Speaker 1: of that ancient light is still travelling through the cosmos today.
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  Speaker 1: Astronomers detect it as the cosmic microwave background, a faint
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  Speaker 1: glare coming from every direction in the sky. This radiation
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  Speaker 1: is astonishingly old. It comes from a time when the
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  Speaker 1: universe was only around 380,000 years old, which sounds ancient
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  Speaker 1: by human standards, but is extremely early compared with the
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  Speaker 1: universe now almost 14 billion years old. The cosmic microwave
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  Speaker 1: background is therefore older than any star or galaxy the
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  Speaker 1: James Webb Space Telescope was designed to observe. Webb is
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  Speaker 1: not a microwave observatory. Its instruments work primarily in infrared wavelengths,
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  Speaker 1: so its purpose is not to study that earliest freely
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  Speaker 1: travelling light directly. Other observatories, including dedicated microwave missions, have
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  Speaker 1: mapped the cosmic microwave background in extraordinary detail. Webb is
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  Speaker 1: looking for what happened later. After recombination, the universe entered
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  Speaker 1: a very strange period. There were atoms. There was dark matter.
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  Speaker 1: There were small differences in density that gravity could gradually amplify.
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  Speaker 1: But there were not yet stars shining across the darkness.
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  Speaker 1: This period is known as the Cosmic Dark Ages. For
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  Speaker 1: a time, The universe contained matter, but very little visible
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  Speaker 1: structure in the form we would recognise today. No galaxies
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  Speaker 1: filled with stars, no glowing nebulae, no planets, no familiar
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  Speaker 1: points of starlight scattered across the sky. Gravity was quietly
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  Speaker 1: doing the slow work of gathering matter into increasingly dense regions. Eventually,
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  Speaker 1: somewhere within that darkness, the first stars began to form.
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  Speaker 1: Exactly when the very first stars appeared remains an active
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  Speaker 1: area of research, but the broad picture places their emergence
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  Speaker 1: within the first few hundred million years after the Big Bang.
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  Speaker 1: Their arrival began a period known as Cosmic Dawn. For
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  Speaker 1: the first time since the universe became transparent, new sources
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  Speaker 1: of light began switching on. The first stars were probably
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  Speaker 1: very different from many stars around us today. They formed
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  Speaker 1: from material containing almost no elements heavier than hydrogen and helium.
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  Speaker 1: Because the heavier elements had not yet been manufactured inside
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  Speaker 1: previous generations of stars, those first stars then helped create
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  Speaker 1: the raw material from which later stars, planets and eventually
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  Speaker 1: living things would be made. Soon after, the first galaxies
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  Speaker 1: began taking shape. This is one of the great frontiers
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  Speaker 1: the James Webb Space Telescope was designed to explore. Its
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  Speaker 1: enormous mirror and infrared instruments allow it to detect galaxies
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  Speaker 1: so distant that their light has been travelling for more
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  Speaker 1: than 13 billion years. Some spectroscopically confirmed galaxies observed with
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  Speaker 1: Webb existed when the universe was less than 300 million
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  Speaker 1: years old. That is an extraordinary thought. We are not
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  Speaker 1: seeing those galaxies as they are now. We are seeing
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  Speaker 1: them as they were when the universe had lived through
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  Speaker 1: only a tiny fraction of its present age. The light
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  Speaker 1: began its journey long before the sun existed, long before
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  Speaker 1: Earth formed, long before the Milky Way had settled into
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  Speaker 1: anything resembling the galaxy we know today. And because astronomers
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  Speaker 1: can analyse the spectrum of that light, they can do
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  Speaker 1: much more than simply notice that a faint object exists.
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  Speaker 1: They can measure its redshift, estimate its distance and age,
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  Speaker 1: investigate the stars forming inside it, study its chemical composition,
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  Speaker 1: and begin reconstructing how galaxies grew during the earlier stages
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  Speaker 1: of cosmic history. This is why the description of Webb
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  Speaker 1: as a telescope that sees the beginning of time is
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  Speaker 1: both powerful and slightly misleading. It does not see the
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  Speaker 1: exact beginning. It does not look all the way back
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  Speaker 1: to the Big Bang itself. What it does is reach
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  Speaker 1: towards some of the earliest luminous structures ever formed. It
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  Speaker 1: observes galaxies from a period when the universe was only
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  Speaker 1: beginning to resemble the place we see around us today.
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  Speaker 1: That is still remarkable enough. The deeper Webb looks, the
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  Speaker 1: closer it moves towards the boundary between the Dark Ages
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  Speaker 1: and cosmic dawn, where the first generations of stars and
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  Speaker 1: galaxies began illuminating space. And reaching that boundary required building
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  Speaker 1: on decades of earlier work, Long before Webb opened its
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  Speaker 1: golden mirror to the infrared universe, another space telescope had
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  Speaker 1: already transformed how deeply humanity could look into the past.
• 14:43
  Speaker 1: That telescope was Hubble. Before the James Webb Space Telescope
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  Speaker 1: began collecting ancient infrared light, another observatory had already transformed
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  Speaker 1: the way humanity looked into the depths of the universe.
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  Speaker 1: The Hubble Space Telescope was launched in 1990, carried into
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  Speaker 1: orbit aboard the Space Shuttle Discovery. It was a project
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  Speaker 1: led by the National Aeronautics and Space Administration, in partnership
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  Speaker 1: with the European Space Agency. And although Hubble became famous
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  Speaker 1: for producing some of the most beautiful astronomical images ever made,
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  Speaker 1: its real importance went much deeper than photography. It changed
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  Speaker 1: what astronomers were able to measure. It changed how far
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  Speaker 1: they could see. And, in several important ways, it helped
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  Speaker 1: create the scientific questions that eventually required Webb. The telescope
• 15:34
  Speaker 1: was named after the American astronomer Edwin Hubble. During the 1920s,
• 15:39
  Speaker 1: Hubble's observations helped demonstrate that some of the faint fuzzy
• 15:43
  Speaker 1: objects seen through telescopes were not small clouds inside the
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  Speaker 1: Milky Way, as many astronomers had once believed. They were
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  Speaker 1: entire galaxies in their own right, lying vastly beyond our own.
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  Speaker 1: His work also became central to the discovery that the
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  Speaker 1: universe is expanding. By studying galaxies and comparing their distances
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  Speaker 1: with the way their light was shifted toward longer, redder wavelengths,
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  Speaker 1: astronomers found that more distant galaxies were generally receding more quickly.
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  Speaker 1: This expanding universe would later become one of the most
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  Speaker 1: important reasons astronomers needed a telescope like Webb. But Hubble
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  Speaker 1: first had to show just how powerful a telescope could
• 16:23
  Speaker 1: become when placed above Earth's atmosphere. Hubble orbits only a
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  Speaker 1: few hundred kilometres above the planet. in what is known
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  Speaker 1: as low Earth orbit. That is extremely close compared with
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  Speaker 1: the scale of the universe, but it places the telescope
• 16:38
  Speaker 1: above almost all of Earth's atmosphere. For ground-based observatories, the
• 16:43
  Speaker 1: atmosphere creates several problems. Moving air bends and distorts incoming light,
• 16:49
  Speaker 1: causing stars to twinkle and fine details to blur. Water
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  Speaker 1: vapour and other molecules also absorb particular wavelengths before they
• 16:57
  Speaker 1: can reach a telescope on the ground. Modern ground observatories
• 17:01
  Speaker 1: can compensate for some of these effects remarkably well, but
• 17:05
  Speaker 1: Hubble gained the enormous advantage of looking through space itself.
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  Speaker 1: Above the atmosphere, its view could remain exceptionally sharp and stable.
• 17:15
  Speaker 1: That made possible one of the most influential experiments in
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  Speaker 1: the history of observational astronomy. In the 1990s, astronomers pointed
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  Speaker 1: Hubble toward a tiny patch of sky in the constellation
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  Speaker 1: Ursa Major. There was nothing particularly dramatic about the chosen region.
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  Speaker 1: It appeared almost empty. There were no bright nearby stars
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  Speaker 1: dominating the view, and no famous nebula sitting conveniently in
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  Speaker 1: the middle. The telescope simply stared into what looked like darkness.
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  Speaker 1: Over many separate exposures, Hubble collected faint light arriving from
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  Speaker 1: that tiny patch. When the observations were combined, the darkness
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  Speaker 1: was no longer empty. It was filled with galaxies. Thousands
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  Speaker 1: of them appeared in an area of sky so small that,
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  Speaker 1: viewed from Earth, it occupied only a minute fraction of
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  Speaker 1: the heavens. Some were relatively nearby by cosmic standards. Others
• 18:12
  Speaker 1: were seen billions of years in the past. The image
• 18:15
  Speaker 1: became known as the Hubble Deep Field. Its significance was
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  Speaker 1: not simply that it contained many galaxies. It demonstrated how
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  Speaker 1: much of the distant universe could be revealed by patiently
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  Speaker 1: collecting extremely faint light. A region that looked almost featureless
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  Speaker 1: to human eyes could contain an enormous record of cosmic history.
• 18:36
  Speaker 1: Later observations pushed even deeper. The Hubble Ultra Deep Field
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  Speaker 1: combined exposures gathered over long periods and revealed galaxies at
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  Speaker 1: even greater distances. With increasingly sensitive observations, Astronomers began identifying
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  Speaker 1: systems whose light had been travelling through space for more
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  Speaker 1: than 13 billion years. Those galaxies appeared extremely young. They
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  Speaker 1: were seen at stages when the universe itself was still
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  Speaker 1: in its infancy. For astronomers trying to understand how galaxies formed,
• 19:07
  Speaker 1: this was enormously valuable. Instead of studying only mature galaxies
• 19:12
  Speaker 1: and attempting to infer their histories, they could observe earlier
• 19:16
  Speaker 1: versions directly. Hubble also helped refine measurements of the expansion
• 19:21
  Speaker 1: of the universe, contributed to the evidence that cosmic expansion
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  Speaker 1: is accelerating, and produced extraordinarily detailed observations of stellar nurseries
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  Speaker 1: where new stars were forming inside clouds of gas and dust.
• 19:35
  Speaker 1: Images of regions such as the Eagle Nebula and the
• 19:39
  Speaker 1: famous Pillars of Creation became cultural icons. But behind the
• 19:43
  Speaker 1: dramatic appearance was serious physics. astronomers could study how young
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  Speaker 1: stars interacted with surrounding gas, how stellar radiation carved cavities
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  Speaker 1: through clouds, and how star formation unfolded within complex environments.
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  Speaker 1: Hubble had effectively opened a window into both the distant
• 20:02
  Speaker 1: universe and the detailed processes occurring much closer to home.
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  Speaker 1: But there was a limit Hubble is sometimes described as
• 20:10
  Speaker 1: a visible light telescope, although that is not quite accurate.
• 20:15
  Speaker 1: Its instruments can observe ultraviolet light, visible light, and part
• 20:20
  Speaker 1: of the near-infrared spectrum. That near-infrared capability allowed it to
• 20:25
  Speaker 1: reach much farther into cosmic history than a purely visible
• 20:29
  Speaker 1: light observatory could. Even so, Hubble was not designed primarily
• 20:35
  Speaker 1: for the much longer infrared wavelengths. that become increasingly important
• 20:40
  Speaker 1: when observing the earliest galaxies, and that mattered because the
• 20:44
  Speaker 1: universe itself was stretching the light. The farther astronomers tried
• 20:49
  Speaker 1: to look back, the more severely ancient light had been
• 20:52
  Speaker 1: shifted toward longer wavelengths by cosmic expansion. Eventually, some of
• 20:58
  Speaker 1: the most valuable light was being pushed beyond the part
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  Speaker 1: of the spectrum where Hubble worked most effectively. This was
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  Speaker 1: not a failure of Hubble, quite the opposite. Hubble had
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  Speaker 1: succeeded so well that it carried astronomy to the edge
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  Speaker 1: of its own capabilities. It revealed distant galaxies, proved the
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  Speaker 1: power of deep-field observations, and allowed astronomers to begin reconstructing
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  Speaker 1: how galaxies changed across billions of years. But it also
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  Speaker 1: exposed the next obstacle. If astronomers wanted to look still
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  Speaker 1: farther back, toward the earliest generations of galaxies, they would
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  Speaker 1: need a telescope built around infrared light from the beginning.
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  Speaker 1: The next observatory would need a much larger mirror. It
• 21:39
  Speaker 1: would need to operate at extraordinarily low temperatures. And most importantly,
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  Speaker 1: it would need to see the ancient light that the
• 21:46
  Speaker 1: expanding universe had stretched beyond Hubble's most sensitive vision. The
• 21:51
  Speaker 1: deeper astronomers tried to look with Hubble, the more they
• 21:54
  Speaker 1: encountered a strange problem. The oldest galaxies were not simply
• 21:58
  Speaker 1: becoming fainter. Their light was changing. To understand why, We
• 22:03
  Speaker 1: have to return to one of the most important discoveries
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  Speaker 1: in modern cosmology. The universe is expanding. This does not
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  Speaker 1: mean that galaxies are all rushing outward through pre-existing empty
• 22:14
  Speaker 1: space from some central point. On the larger scales, space
• 22:18
  Speaker 1: itself is stretching, carrying widely separated galaxies farther apart over time.
• 22:24
  Speaker 1: That expansion has direct effect on light. Light behaves as
• 22:28
  Speaker 1: a wave, and every wave has a wavelength. Visible light
• 22:32
  Speaker 1: occupies only a narrow portion of the electromagnetic spectrum, with
• 22:36
  Speaker 1: shorter wavelengths appearing toward the blue and violet end, and
• 22:40
  Speaker 1: longer wavelengths appearing toward the red. When light travels across
• 22:44
  Speaker 1: an expanding universe, the space through which it moves stretches.
• 22:49
  Speaker 1: The wavelength of the light stretches with it. By the
• 22:52
  Speaker 1: time that light reaches us, its wavelength can be much
• 22:56
  Speaker 1: longer than it was when it first left its source.
• 22:59
  Speaker 1: This effect is called cosmological redshift. The name can be
• 23:03
  Speaker 1: slightly misleading, because the light does not necessarily just become
• 23:07
  Speaker 1: a slightly redder shade that human eyes could still see.
• 23:11
  Speaker 1: With enough expansion, wavelengths that began in ultraviolet light can
• 23:15
  Speaker 1: be stretched into visible light, visible light can be stretched
• 23:19
  Speaker 1: into infrared, and light that began in the infrared can
• 23:23
  Speaker 1: be pushed into still longer wavelengths. So when astronomers say
• 23:27
  Speaker 1: that a distant galaxy is highly redshifted, they are not
• 23:30
  Speaker 1: simply saying the galaxy itself is naturally red. They are
• 23:34
  Speaker 1: describing what has happened to its light during the journey
• 23:37
  Speaker 1: across an expanding universe. The modern understanding of cosmic expansion
• 23:43
  Speaker 1: developed through the work of several scientists, including the Belgian
• 23:47
  Speaker 1: physicist and priest Georges Lemaître and the American astronomer Edwin Hubble.
• 23:53
  Speaker 1: Lemaître used Albert Einstein's general theory of relativity to describe
• 23:58
  Speaker 1: an expanding universe and connected that expansion with observations of
• 24:03
  Speaker 1: distant galaxies. Hubble's later measurements helped establish the observational relationship
• 24:10
  Speaker 1: between galactic distance and recession. The farther away galaxies were
• 24:14
  Speaker 1: found to be, in general, the more strongly their light
• 24:17
  Speaker 1: was shifted toward longer wavelengths. That relationship became one of
• 24:22
  Speaker 1: the foundations of modern cosmology. For astronomers interested in the
• 24:26
  Speaker 1: earliest galaxies, redshift creates both an opportunity and a problem.
• 24:31
  Speaker 1: The opportunity is that the amount of redshift contains information.
• 24:36
  Speaker 1: It helps astronomers estimate how much the universe has expanded
• 24:40
  Speaker 1: since the light was emitted, and therefore how far back
• 24:43
  Speaker 1: in cosmic history they are looking. The problem is that
• 24:46
  Speaker 1: the farther back they look, The farther the ancient light
• 24:49
  Speaker 1: moves away from the wavelengths our eyes can see. Imagine
• 24:53
  Speaker 1: a very young galaxy producing large amounts of ultraviolet radiation
• 24:57
  Speaker 1: from hot, massive stars. At the time that light leaves
• 25:01
  Speaker 1: the galaxy, much of it may be far bluer than
• 25:04
  Speaker 1: anything the human eye can detect. But the journey to
• 25:08
  Speaker 1: Earth may take more than 13 billion years. During that time,
• 25:13
  Speaker 1: the universe expands enormously. By the moment those photons arrive here,
• 25:18
  Speaker 1: what began as ultraviolet radiation may have been stretched all
• 25:22
  Speaker 1: the way into the near-infrared. Visible light can be shifted
• 25:26
  Speaker 1: even farther into the infrared. This is why the earliest
• 25:29
  Speaker 1: galaxies can effectively disappear from an optical image. They have
• 25:33
  Speaker 1: not stopped producing light. Their light has simply moved somewhere
• 25:37
  Speaker 1: else in the electromagnetic spectrum. And the closer astronomers try
• 25:41
  Speaker 1: to get to cosmic dawn, the more severe the problem becomes.
• 25:45
  Speaker 1: The earliest galaxies are already extraordinarily faint because they are
• 25:48
  Speaker 1: immensely distant. Their light is spread over a vast area
• 25:53
  Speaker 1: and only a tiny number of photons eventually reach a
• 25:56
  Speaker 1: telescope near Earth. On top of that faintness comes strong
• 26:00
  Speaker 1: cosmological redshift. The combination means that a telescope hoping to
• 26:04
  Speaker 1: investigate the first galaxies needs to do two things extremely well.
• 26:10
  Speaker 1: It must detect long infrared wavelengths. and it must collect
• 26:14
  Speaker 1: as much faint light as possible. Hubble can observe part
• 26:19
  Speaker 1: of the near-infrared spectrum, but its capabilities were never designed
• 26:23
  Speaker 1: to extend deeply into the much broader infrared range needed
• 26:28
  Speaker 1: for the earliest galaxies. The James Webb Space Telescope was.
• 26:33
  Speaker 1: Its instruments cover wavelengths beginning at roughly six-tenths of a micrometer,
• 26:39
  Speaker 1: close to the visible red part of the spectrum. and
• 26:42
  Speaker 1: extend outward to nearly 29 micrometers in the mid-infrared. That
• 26:47
  Speaker 1: wide range allows Webb to capture light that has been
• 26:50
  Speaker 1: stretched far beyond the region where Hubble is most sensitive.
• 26:54
  Speaker 1: But wavelength coverage alone would not be enough. Ancient galaxies
• 26:58
  Speaker 1: do not conveniently send us bright beams. By the time
• 27:02
  Speaker 1: their photons arrive, the signal can be extraordinarily weak, so
• 27:06
  Speaker 1: Webb also needed a much larger collecting area. Its primary
• 27:10
  Speaker 1: mirror is roughly 6.5 metres across, giving it far more
• 27:14
  Speaker 1: light-gathering power than Hubble. That means more photons can be
• 27:18
  Speaker 1: captured during an observation, allowing astronomers to study objects that
• 27:22
  Speaker 1: might otherwise remain little more than faint hints buried in
• 27:25
  Speaker 1: background noise. Once that light is collected, astronomers can examine
• 27:30
  Speaker 1: how its brightness changes across different wavelengths. Certain features are
• 27:34
  Speaker 1: especially useful. Hydrogen, for example, produces characteristic patterns in a
• 27:40
  Speaker 1: galaxy's spectrum. At very large distances, one important feature is
• 27:45
  Speaker 1: the sharp reduction in light at wavelengths, where neutral hydrogen
• 27:49
  Speaker 1: absorbs radiation. The position of this break moves toward longer
• 27:53
  Speaker 1: wavelengths as redshift increases. By measuring where such features appear,
• 27:58
  Speaker 1: astronomers can estimate how strongly a galaxy's light has been stretched.
• 28:03
  Speaker 1: Imaging can often provide an initial redshift estimate from the
• 28:06
  Speaker 1: colours of a distant source. Spectroscopy can go much further.
• 28:11
  Speaker 1: By spreading the light into its component wavelengths and identifying
• 28:15
  Speaker 1: specific spectral features, astronomers can measure redshift far more precisely.
• 28:22
  Speaker 1: A tiny reddish speck in an image can then be
• 28:25
  Speaker 1: placed within a particular era of cosmic history. That faint
• 28:29
  Speaker 1: smudge may turn out to be a galaxy seen only
• 28:32
  Speaker 1: a few hundred million years after the Big Bang. This
• 28:36
  Speaker 1: is why infrared capability sits at the heart of Webb's design.
• 28:40
  Speaker 1: It was not added because infrared astronomy happened to be useful.
• 28:44
  Speaker 1: It was demanded by the physics of the expanding universe.
• 28:48
  Speaker 1: If astronomers wanted to observe some of the first galaxies,
• 28:51
  Speaker 1: they had no choice but to follow their light into
• 28:54
  Speaker 1: the infrared. Once that scientific requirement was understood, however, an
• 28:59
  Speaker 1: enormous engineering problem appeared. Infrared telescopes are extremely sensitive to heat.
• 29:06
  Speaker 1: A warm telescope glows in infrared radiation of its own,
• 29:10
  Speaker 1: creating exactly the kind of background signal astronomers are trying
• 29:13
  Speaker 1: to avoid. The mirror also needed to be huge, because
• 29:18
  Speaker 1: the targets were so faint, and somehow this enormous, incredibly
• 29:23
  Speaker 1: cold observatory still had to fit inside a rocket. Astronomers
• 29:28
  Speaker 1: knew what they needed to build. The more difficult question
• 29:31
  Speaker 1: was whether anyone could actually build it. Once astronomers knew
• 29:36
  Speaker 1: that the next great space telescope had to work primarily
• 29:39
  Speaker 1: in infrared light, light, another problem became unavoidable. It needed
• 29:43
  Speaker 1: to be enormous. The earliest galaxies are unimaginably distant, and
• 29:48
  Speaker 1: the photons arriving from them are astonishingly scarce. Even a
• 29:52
  Speaker 1: galaxy containing billions of stars can appear as little more
• 29:55
  Speaker 1: than a faint smudge after its light has crossed the
• 29:58
  Speaker 1: expanding universe. for more than 13 billion years. A telescope
• 30:04
  Speaker 1: cannot create photons that never arrive. All it can do
• 30:08
  Speaker 1: is collect as many of the available ones as possible,
• 30:11
  Speaker 1: and for that the size of the mirror matters enormously.
• 30:14
  Speaker 1: Hubble's primary mirror is roughly 2.4 metres across. That was
• 30:18
  Speaker 1: large enough to revolutionise astronomy, but astronomers planning its successor
• 30:23
  Speaker 1: wanted considerably more collecting power. The primary mirror of the
• 30:27
  Speaker 1: James Webb Space Telescope is roughly 6.5 metres across. Its
• 30:32
  Speaker 1: effective light collecting area is around 25 square metres, compared
• 30:36
  Speaker 1: with roughly 4.5 square metres for Hubble. In practical terms,
• 30:41
  Speaker 1: Webb gathers several times as much light, close to six
• 30:45
  Speaker 1: times Hubble's collecting area. For a faint astronomy, that difference
• 30:50
  Speaker 1: is transformative. Imagine standing outside during a very gentle rain
• 30:55
  Speaker 1: holding a small bowl Only a few drops fall into
• 30:59
  Speaker 1: it each second. Replace the bowl with something much wider,
• 31:03
  Speaker 1: and suddenly you catch far more water without changing the
• 31:05
  Speaker 1: rain itself. A telescope mirror works in a broadly similar way.
• 31:11
  Speaker 1: The universe is sending the same tiny trickle of ancient
• 31:14
  Speaker 1: photons either way. A larger mirror simply catches more of them.
• 31:19
  Speaker 1: That extra light allows astronomers to detect fainter objects, collect
• 31:23
  Speaker 1: better spectra, and build clearer pictures of galaxies existing at
• 31:27
  Speaker 1: extraordinary distances. There was, however, a rather obvious difficulty. A
• 31:33
  Speaker 1: conventional mirror six and a half metres across would not
• 31:36
  Speaker 1: fit inside the nose of the rocket intended to launch it.
• 31:40
  Speaker 1: Space telescopes have to survive an unusual design constraint. They
• 31:44
  Speaker 1: may spend years operating in enormous open space, but first
• 31:49
  Speaker 1: they must squeeze inside the narrow protective fairing of a
• 31:52
  Speaker 1: launch vehicle. You cannot simply attach an enormous observatory to
• 31:56
  Speaker 1: the top and hope the atmosphere will be understanding about it.
• 32:00
  Speaker 1: So Webb's mirror could not be built as one solid piece. Instead,
• 32:05
  Speaker 1: engineers divided it into 18 individual segments. Each segment is hexagonal. Together,
• 32:12
  Speaker 1: when fully deployed, those 18 pieces form the enormous primary
• 32:16
  Speaker 1: mirror that gives Webb its distinctive honeycomb appearance. The hexagonal
• 32:21
  Speaker 1: shape was chosen for practical reasons. Hexagons can fit together
• 32:25
  Speaker 1: closely with very little wasted space between them. Squares can
• 32:29
  Speaker 1: also tile a surface neatly, but they would make it
• 32:32
  Speaker 1: harder to create an overall mirror shape approaching a circle.
• 32:36
  Speaker 1: Circles meanwhile leave gaps when packed together. Hexagons provide a
• 32:41
  Speaker 1: useful compromise. They can be arranged tightly while producing a broad,
• 32:45
  Speaker 1: roughly circular collecting surface. More importantly, the segmented design allowed
• 32:51
  Speaker 1: Webb to fold. During launch, sections of the primary mirror
• 32:55
  Speaker 1: were tucked inward so the observatory could fit inside the
• 32:58
  Speaker 1: rocket fairing. Once in space, those wings would swing outward
• 33:02
  Speaker 1: and lock into position, but simply placing 18 pieces beside
• 33:06
  Speaker 1: one another would not magically create a functioning telescope. They
• 33:10
  Speaker 1: also had to behave optically as though they were one
• 33:13
  Speaker 1: continuous surface. That required extraordinary precision. Each segment can be
• 33:18
  Speaker 1: moved using small actuators mounted behind it. engineers can adjust
• 33:23
  Speaker 1: its position and curvature with minute changes until light reflected
• 33:27
  Speaker 1: from all 18 pieces converges correctly. At first, after deployment,
• 33:33
  Speaker 1: a single star produced multiple separate images because each mirror
• 33:37
  Speaker 1: segment was pointing slightly differently. Through a long alignment process,
• 33:42
  Speaker 1: those separate images were gradually brought together until the segmented
• 33:45
  Speaker 1: mirror acted like one enormous optical instrument. The material used
• 33:50
  Speaker 1: for the segments was another carefully considered choice. The underlying
• 33:54
  Speaker 1: mirrors are made from beryllium. Beryllium is lightweight, stiff and
• 33:58
  Speaker 1: capable of retaining its shape extremely well under the extremely
• 34:01
  Speaker 1: cold conditions in which Webb operates. That last quality is crucial.
• 34:06
  Speaker 1: Materials expand when they warm and contract when they cool.
• 34:10
  Speaker 1: For an everyday object, these changes may be too small
• 34:12
  Speaker 1: to notice. For a space telescope, trying to control the
• 34:16
  Speaker 1: shape of a mirror with extraordinary precision tiny changes matter.
• 34:21
  Speaker 1: The engineers needed to understand exactly how the mirror would
• 34:24
  Speaker 1: behave after cooling to temperatures far below anything experienced in
• 34:28
  Speaker 1: an ordinary room. Each beryllium segment was therefore manufactured and
• 34:33
  Speaker 1: polished with its future cold operating conditions in mind. Then
• 34:37
  Speaker 1: came the feature that makes Webb instantly recognisable, the gold.
• 34:41
  Speaker 1: Each mirror segment is coated with an extremely thin layer
• 34:45
  Speaker 1: of gold because gold is particularly effective at reflecting infrared light.
• 34:50
  Speaker 1: The colour is striking, but appearance had essentially nothing to
• 34:54
  Speaker 1: do with the decision. The designers were not attempting to
• 34:57
  Speaker 1: build the most expensive looking telescope in history. The coating
• 35:01
  Speaker 1: exists because it improves the mirror's performance at the wavelengths
• 35:04
  Speaker 1: Webb was designed to observe. And despite the enormous golden surface,
• 35:09
  Speaker 1: there is remarkably little gold on it. The coating is
• 35:13
  Speaker 1: only about 100 nanometres thick. Across the entire primary mirror,
• 35:18
  Speaker 1: the total amount of gold is only around 50 grams,
• 35:21
  Speaker 1: roughly comparable with the mass of a golf ball. Underneath
• 35:25
  Speaker 1: that almost unimaginably thin layer lies the beryllium doing the
• 35:28
  Speaker 1: structural work. Making all of this function required far more
• 35:33
  Speaker 1: than one agency or one group of engineers. the National
• 35:37
  Speaker 1: Aeronautics and Space Administration led the mission in partnership with
• 35:41
  Speaker 1: the European Space Agency and the Canadian Space Agency. The
• 35:45
  Speaker 1: Space Telescope Science Institute became responsible for major aspects of
• 35:49
  Speaker 1: science operations, including managing the Astronomical Observing Programme. Northrop Grumman
• 35:55
  Speaker 1: served as the main industrial contractor for the observatory, while universities,
• 36:00
  Speaker 1: research institutes, laboratories, aerospace companies, and specialist teams across several
• 36:06
  Speaker 1: countries contributed instruments, components, testing, software, engineering and scientific expertise.
• 36:15
  Speaker 1: Thousands of people ultimately had some role in turning Webb
• 36:19
  Speaker 1: from an idea into a working observatory, and every major
• 36:22
  Speaker 1: component had to cooperate with everything else. The mirror had
• 36:25
  Speaker 1: to unfold properly, its segments had to align, the spacecraft
• 36:30
  Speaker 1: had to point with extraordinary stability. The instruments had to
• 36:34
  Speaker 1: detect signals so faint that only a small number of
• 36:37
  Speaker 1: photons might carry the information astronomers wanted. But the enormous
• 36:42
  Speaker 1: mirror created another problem. Webb had been designed to detect
• 36:45
  Speaker 1: infrared radiation, and warm objects emit infrared radiation. That included
• 36:51
  Speaker 1: the telescope itself. If Webb were allowed to remain too warm,
• 36:56
  Speaker 1: its own thermal glow could interfere with the faint infrared
• 36:59
  Speaker 1: light arriving from distant galaxies. It would be rather like
• 37:03
  Speaker 1: trying to study a candle in the distance, while holding
• 37:06
  Speaker 1: a bright lamp directly in front of your face. So
• 37:09
  Speaker 1: building the enormous golden mirror was only half the problem.
• 37:13
  Speaker 1: The next challenge was somehow keeping that entire observatory extraordinarily cold,
• 37:18
  Speaker 1: while sunlight poured across space around it. For Webb to
• 37:22
  Speaker 1: detect some of the faintest infrared light in the universe,
• 37:25
  Speaker 1: building an enormous mirror was not enough. The telescope also
• 37:30
  Speaker 1: had to become extremely cold. This follows from a slightly
• 37:34
  Speaker 1: awkward fact about infrared astronomy. The universe is not the
• 37:37
  Speaker 1: only thing producing infrared radiation. The telescope produces it too.
• 37:43
  Speaker 1: Infrared light is simply one part of the electromagnetic spectrum.
• 37:47
  Speaker 1: It sits beyond visible red at wavelengths too long for
• 37:50
  Speaker 1: human eyes to detect. It is often associated with heat
• 37:54
  Speaker 1: because objects at everyday temperatures emit a great deal of
• 37:57
  Speaker 1: their radiation at infrared wavelengths. Your body emits infrared radiation.
• 38:02
  Speaker 1: A building emits it. Earth emits it. And unless something
• 38:06
  Speaker 1: is done about it, a space telescope does as well.
• 38:09
  Speaker 1: That creates an obvious problem for an instrument trying to
• 38:12
  Speaker 1: measure extremely faint infrared signals arriving from distant galaxies. Imagine
• 38:18
  Speaker 1: trying to listen for a whisper while standing beside a
• 38:20
  Speaker 1: running engine. It does not matter how sensitive your ears
• 38:24
  Speaker 1: are if the nearby noise overwhelms the thing you're trying
• 38:27
  Speaker 1: to hear. For Webb, thermal radiation could become that noise.
• 38:32
  Speaker 1: The solution is one of the most remarkable parts of
• 38:34
  Speaker 1: the entire observatory. Beneath the mirror is an enormous five-layer sunshield,
• 38:40
  Speaker 1: roughly comparable in size to a tennis court. When fully deployed,
• 38:45
  Speaker 1: it stretches for more than 20 metres along its longest dimension.
• 38:49
  Speaker 1: Its job is to divide Webb into two very different environments.
• 38:53
  Speaker 1: On one side are the Sun, Earth, Moon, solar panels,
• 38:57
  Speaker 1: communications equipment, and other spacecraft systems that either produce heat
• 39:02
  Speaker 1: or reflect it. On the other side are the mirror
• 39:05
  Speaker 1: and scientific instruments, which need to remain extraordinarily cold. The
• 39:10
  Speaker 1: sunshield sits between them. Its five layers are made from
• 39:14
  Speaker 1: an extremely thin material called Kapton, coated with reflective materials
• 39:19
  Speaker 1: including aluminium. The layers are separated from one another rather
• 39:24
  Speaker 1: than forming one thick blanket. That separation is important. When
• 39:28
  Speaker 1: sunlight strikes the outer layer, much of the incoming energy
• 39:32
  Speaker 1: is reflected away. Some heat is absorbed, but the layer
• 39:36
  Speaker 1: can radiate much of that energy sideways into space. The
• 39:40
  Speaker 1: next layer receives less. Then the next receives less again.
• 39:44
  Speaker 1: Each successive layer reduces the amount of heat reaching the
• 39:47
  Speaker 1: cold side. it is a little like placing several separate
• 39:51
  Speaker 1: barriers between a fire and an object you're trying to protect,
• 39:55
  Speaker 1: except these barriers are incredibly thin sheets operating in the
• 39:58
  Speaker 1: vacuum of space. By the time the energy has crossed
• 40:02
  Speaker 1: all five layers, the difference in temperature between Webb's two
• 40:06
  Speaker 1: sides is enormous. The sun-facing spacecraft side can sit at
• 40:10
  Speaker 1: temperatures above the freezing point of water. Only a short
• 40:14
  Speaker 1: distance away, across the shield, The telescope operates at temperatures
• 40:18
  Speaker 1: tens of degrees above absolute zero. The primary mirror must
• 40:23
  Speaker 1: remain below roughly 50 kelvins. That corresponds to around minus
• 40:27
  Speaker 1: 223 degrees Celsius. At temperatures like these, Webb's mirrors emit
• 40:33
  Speaker 1: far less infrared radiation of their own, allowing them to
• 40:36
  Speaker 1: receive faint astronomical signals without drowning them in the telescope's
• 40:40
  Speaker 1: thermal glow. Several of Webb's near-infrared instruments become even colder.
• 40:46
  Speaker 1: They typically operate at roughly 39 kelvins, around minus 234
• 40:52
  Speaker 1: degrees Celsius. Most of this cooling happens passively. The sunshield
• 40:57
  Speaker 1: blocks incoming heat, while the telescope gradually radiates its own
• 41:02
  Speaker 1: remaining thermal energy into space. But one instrument requires something
• 41:06
  Speaker 1: more extreme. The mid-infrared instrument observes some of Webb's longest wavelengths.
• 41:12
  Speaker 1: At those wavelengths, even the tiny amount of heat remaining
• 41:15
  Speaker 1: in the observatory could interfere with measurements. So the mid-infrared
• 41:20
  Speaker 1: instrument must be cooled to only about 7 kelvins. That
• 41:24
  Speaker 1: is roughly minus 266 degrees Celsius, only a few degrees
• 41:29
  Speaker 1: above absolute zero. Passive cooling alone cannot reliably reach that temperature. Instead,
• 41:36
  Speaker 1: Webb uses a specialised cryo-cooler that actively removes heat from
• 41:41
  Speaker 1: the instrument. This makes the mid-infrared instrument one of the
• 41:45
  Speaker 1: coldest major parts of the observatory, and it is only
• 41:48
  Speaker 1: one member of a group of four principal scientific instruments.
• 41:53
  Speaker 1: The near-infrared camera is one of Webb's primary imaging instruments.
• 41:57
  Speaker 1: It detects near-infrared light and is particularly important for finding
• 42:02
  Speaker 1: extremely distant galaxies, studying star-forming regions, examining objects in our
• 42:08
  Speaker 1: own solar system, and helping align the telescope's mirror. The
• 42:13
  Speaker 1: near-infrared spectrograph approaches light differently. Rather than simply producing an image,
• 42:19
  Speaker 1: it can separate incoming radiation into its individual wavelengths. This
• 42:24
  Speaker 1: creates a spectrum, and spectra contain an extraordinary amount of information.
• 42:30
  Speaker 1: Atoms and molecules interact with particular wavelengths of light. Their
• 42:35
  Speaker 1: patterns can therefore leave recognisable signatures in a spectrum, rather
• 42:39
  Speaker 1: like fingerprints. By examining these patterns, astronomers can investigate which
• 42:44
  Speaker 1: chemical elements or molecules are present. They can estimate temperatures.
• 42:49
  Speaker 1: They can study how quickly material is moving toward or
• 42:52
  Speaker 1: away from us. And for distant galaxies, they can measure
• 42:56
  Speaker 1: cosmological redshift and determine how far back in cosmic history
• 43:00
  Speaker 1: the light originated. Webb can even collect spectra from many
• 43:04
  Speaker 1: objects at once, allowing astronomers to examine numerous faint galaxies
• 43:09
  Speaker 1: in a single field rather than studying every source individually.
• 43:14
  Speaker 1: The mid-infrared instrument combines imaging and spectroscopy at longer infrared wavelengths.
• 43:20
  Speaker 1: Those wavelengths are particularly useful for studying cooler objects, warm dust,
• 43:25
  Speaker 1: star formation, planetary systems, and distant galaxies whose light has
• 43:30
  Speaker 1: been shifted deeply into the infrared. Then there is the
• 43:33
  Speaker 1: fine guidance sensor with the near-infrared imager and slitless spectrograph.
• 43:39
  Speaker 1: supplied by the Canadian Space Agency. Part of this system
• 43:43
  Speaker 1: performs one of the less glamorous but absolutely essential jobs
• 43:47
  Speaker 1: on Webb. It helps the observatory point accurately. A telescope
• 43:52
  Speaker 1: capable of resolving extraordinarily faint targets must remain extremely steady
• 43:57
  Speaker 1: while collecting their light. Even a magnificent mirror is not
• 44:01
  Speaker 1: particularly useful if the spacecraft cannot keep it aimed at
• 44:05
  Speaker 1: the correct patch of sky. All of these systems depend
• 44:09
  Speaker 1: on one another. The large mirror gathers the light. The
• 44:13
  Speaker 1: mirror segments must remain aligned with extraordinary precision. The spacecraft
• 44:18
  Speaker 1: must hold the telescope steady. The sunshield must keep the
• 44:23
  Speaker 1: optics cold. The instruments must remain at the correct temperatures.
• 44:27
  Speaker 1: Detectors must convert arriving photons into measurable electrical signals. Communication
• 44:34
  Speaker 1: systems must send the resulting information back to Earth. and
• 44:38
  Speaker 1: all of it has to operate together in space. The
• 44:41
  Speaker 1: strange appearance of Webb begins to make much more sense
• 44:44
  Speaker 1: when viewed this way. Its golden segmented mirror is not
• 44:48
  Speaker 1: a stylistic choice. Neither is the enormous silver sun shield.
• 44:53
  Speaker 1: Its unusual shape is not the result of somebody deciding
• 44:56
  Speaker 1: that future space telescopes ought to look more dramatic. Almost
• 45:01
  Speaker 1: every major feature exists because infrared astronomy demanded it. To
• 45:05
  Speaker 1: see extremely faint ancient galaxies, Webb needed a large mirror.
• 45:10
  Speaker 1: To fit that mirror inside a rocket, it had to fold.
• 45:14
  Speaker 1: To observe infrared light, the telescope had to remain cold.
• 45:18
  Speaker 1: To remain cold, it needed an enormous sunshield. And to
• 45:22
  Speaker 1: observe some wavelength properly, parts of it had to become
• 45:25
  Speaker 1: colder still. One scientific requirement led to another engineering requirement,
• 45:31
  Speaker 1: and then another. The result was an observatory containing thousands
• 45:36
  Speaker 1: of components that would ultimately have to work together with
• 45:39
  Speaker 1: extraordinary precision. What had begun as an idea for the
• 45:43
  Speaker 1: successor to Hubble gradually became one of the most ambitious
• 45:47
  Speaker 1: scientific machines ever attempted. And turning that idea into something
• 45:51
  Speaker 1: capable of leaving Earth would take decades. Long before the
• 45:55
  Speaker 1: James Webb Space Telescope opened its golden mirror to the universe,
• 45:59
  Speaker 1: it existed only as an idea. In fact, The earliest
• 46:04
  Speaker 1: discussions about what might eventually succeed Hubble began before Hubble
• 46:08
  Speaker 1: itself had even been launched. Astronomers already understood that no
• 46:12
  Speaker 1: single telescope could answer every question forever. Hubble would be
• 46:16
  Speaker 1: extraordinarily powerful, but future observatories would eventually need to reach
• 46:20
  Speaker 1: farther into the infrared and farther back into cosmic history.
• 46:24
  Speaker 1: By the middle of the 1990s, that ambition had become
• 46:27
  Speaker 1: much more concrete. In 1996, an 18-member committee led by
• 46:32
  Speaker 1: the American astronomer Alan Dressler recommended the development of a
• 46:36
  Speaker 1: large space telescope designed to study the formation of the
• 46:39
  Speaker 1: first galaxies. At the time, the proposed observatory was known
• 46:44
  Speaker 1: as the Next Generation Space Telescope. The name was almost
• 46:47
  Speaker 1: modest compared with what the project would eventually become. The
• 46:51
  Speaker 1: original idea was relatively straightforward in principle. Build a large
• 46:55
  Speaker 1: infrared telescope. Place it in space. use it to study
• 46:59
  Speaker 1: some of the earlier stars and galaxies. The trouble was
• 47:03
  Speaker 1: that each of those simple sentences concealed an extraordinary engineering problem.
• 47:08
  Speaker 1: The mirror had to be much larger than Hubble's. It
• 47:10
  Speaker 1: had to fold. It had to unfold itself after launch.
• 47:14
  Speaker 1: Its instruments had to operate at extremely low temperatures. Its
• 47:18
  Speaker 1: enormous sunshield had to deploy correctly. Its mirror segments had
• 47:22
  Speaker 1: to align with extraordinary precision. And all of this had
• 47:26
  Speaker 1: to happen in an environment where nobody could simply walk
• 47:29
  Speaker 1: over with a toolbox if something went wrong. The mission
• 47:32
  Speaker 1: gradually grew into a huge international programme. The National Aeronautics
• 47:37
  Speaker 1: and Space Administration took the leading role. The European Space
• 47:41
  Speaker 1: Agency became a major partner, providing important hardware and the
• 47:45
  Speaker 1: eventual launch vehicle. The Canadian Space Agency supplied key scientific
• 47:49
  Speaker 1: and guidance systems. Universities, laboratories, research institutions, aerospace companies, engineers,
• 47:59
  Speaker 1: software teams and scientists across many countries became involved. Northrop
• 48:04
  Speaker 1: Grumman eventually became the principal contractor responsible for integrating major
• 48:08
  Speaker 1: parts of the observatory. The Space Telescope Science Institute prepared
• 48:13
  Speaker 1: for the task of operating Webb and organising its scientific
• 48:17
  Speaker 1: observations once the telescope reached space. What had begun as
• 48:21
  Speaker 1: an astronomical wish list was turning into a machine containing
• 48:25
  Speaker 1: thousands of components that all had to work together, and
• 48:29
  Speaker 1: as the design became more ambitious, the schedule began to move.
• 48:33
  Speaker 1: Then it moved again, and again. Early projections imagined a
• 48:38
  Speaker 1: launch much sooner and at a much lower cost than
• 48:41
  Speaker 1: what eventually proved possible, but the telescope being designed was
• 48:45
  Speaker 1: unlike anything previously built. The segmented primary mirror had to
• 48:49
  Speaker 1: behave as one optical surface after deployment. The sunshield had
• 48:53
  Speaker 1: to unfold from a compact launch configuration into something roughly
• 48:57
  Speaker 1: the size of a tennis court. The instruments had to
• 49:00
  Speaker 1: function at cryogenic temperatures. Deployment systems had to be tested repeatedly.
• 49:05
  Speaker 1: The entire observatory had to survive the vibration and stress
• 49:09
  Speaker 1: of launch, while remaining precise enough afterward to measure extraordinarily
• 49:14
  Speaker 1: faint infrared signals. Testing one component at a time was
• 49:17
  Speaker 1: not enough. The pieces had to be integrated. Then the
• 49:21
  Speaker 1: integrated systems had to be tested again. And when problems appeared,
• 49:26
  Speaker 1: engineers often had no choice but to redesign, repair or
• 49:29
  Speaker 1: repeat work that had already taken years. There were genuine
• 49:33
  Speaker 1: management problems as well. The Government Accountability Office repeatedly documented
• 49:38
  Speaker 1: scheduled delays rising costs, technical risks and difficulties in keeping
• 49:43
  Speaker 1: the programme within earlier estimates. By the years leading up
• 49:47
  Speaker 1: to launch, the projected cost had risen to roughly $ 9. 7 billion.
• 49:53
  Speaker 1: That figure made Webb not only one of the most
• 49:55
  Speaker 1: technically ambitious scientific projects ever attempted, but one of the
• 49:59
  Speaker 1: most expensive, and inevitably that brought political pressure. In 2011,
• 50:05
  Speaker 1: the telescope came remarkably close to being cancelled. the United
• 50:09
  Speaker 1: States House of Representatives Appropriations Proposal recommended ending funding for
• 50:14
  Speaker 1: the project after years of cost growth and delay. For
• 50:17
  Speaker 1: a mission already deep into development, this was not an
• 50:21
  Speaker 1: abstract threat. Cancellation would have ended decades of planning and
• 50:25
  Speaker 1: discarded enormous amounts of work already completed. The telescope survived.
• 50:31
  Speaker 1: Congress ultimately continued funding the mission under a revised plan
• 50:35
  Speaker 1: with tighter oversight and and a restructured budget and schedule.
• 50:40
  Speaker 1: But the episode made something very clear. Webb could not
• 50:43
  Speaker 1: simply continue indefinitely. Eventually, after all the delays and redesigns,
• 50:48
  Speaker 1: it had to work. It is easy to look back
• 50:51
  Speaker 1: at the long development period and imagine that every delay
• 50:55
  Speaker 1: was evidence of incompetence. The reality was more complicated. There
• 51:00
  Speaker 1: were certainly budgeting mistakes, unrealistic schedules and management failures. but
• 51:06
  Speaker 1: there was also the basic difficulty of building something that
• 51:09
  Speaker 1: had never existed before. Webb was designed to operate in
• 51:13
  Speaker 1: conditions that could not be completely reproduced on Earth. Its
• 51:17
  Speaker 1: mirror and instruments would eventually settle into an extremely cold
• 51:21
  Speaker 1: environment in space. Its sun shield would deploy in microgravity.
• 51:26
  Speaker 1: Its optical system would have to work after launch stresses
• 51:30
  Speaker 1: and after cooling by hundreds of degrees. Engineers could simulate
• 51:35
  Speaker 1: these conditions. They could test components inside enormous vacuum chambers.
• 51:41
  Speaker 1: They could shake the observatory to reproduce launch vibrations. They
• 51:45
  Speaker 1: could chill systems to extraordinarily low temperatures. But at some point,
• 51:49
  Speaker 1: testing had to end. The real experiment would happen only
• 51:54
  Speaker 1: after Webb had left Earth. That made the stakes increasingly uncomfortable.
• 51:59
  Speaker 1: Every year of additional work meant more money invested. more
• 52:02
  Speaker 1: people had spent significant parts of their careers on the telescope.
• 52:07
  Speaker 1: Some scientists who had been involved near the beginning of
• 52:09
  Speaker 1: the programme were approaching retirement by the time launch finally arrived.
• 52:14
  Speaker 1: And unlike Hubble, Webb was not heading into low-Earth orbit.
• 52:18
  Speaker 1: It was being sent roughly one and a half million
• 52:20
  Speaker 1: kilometres away. No servicing mission was waiting in reserve. There
• 52:25
  Speaker 1: would be no convenient opportunity to replace a failed instrument
• 52:28
  Speaker 1: or tighten something that had worked loose. The machine had
• 52:32
  Speaker 1: to survive launch. Then it had to begin assembling itself.
• 52:36
  Speaker 1: The mirror wings had to unfold. The sunshield had to
• 52:39
  Speaker 1: open and tension. The secondary mirror had to move into place.
• 52:44
  Speaker 1: Dozens of major mechanisms and hundreds of smaller components had
• 52:48
  Speaker 1: to operate correctly while Webb travelled farther and farther from Earth.
• 52:52
  Speaker 1: So after nearly three decades of planning, redesigning, testing, delaying
• 52:56
  Speaker 1: and spending, the end of the development programme did not
• 53:00
  Speaker 1: bring relief. it brought the most dangerous part. On Christmas
• 53:04
  Speaker 1: morning in 2021, the James Webb Space Telescope was finally ready.
• 53:09
  Speaker 1: It sat folded inside the protective fairing of an Ariane
• 53:13
  Speaker 1: 5 rocket at Europe Spaceport in French Guiana. The mirror
• 53:17
  Speaker 1: was tucked inward. The sunshield was packed away. The telescope,
• 53:22
  Speaker 1: that would eventually stretch across a space larger than a
• 53:25
  Speaker 1: tennis court, had been compressed tightly enough to fit inside
• 53:28
  Speaker 1: a rocket. Thousands of people had contributed to getting it there.
• 53:33
  Speaker 1: Nearly $ 10 billion had been committed. A scientific idea that
• 53:38
  Speaker 1: had begun a generation earlier was now sitting on top
• 53:40
  Speaker 1: of several hundred tonnes of fuel, and from that moment onward,
• 53:45
  Speaker 1: almost everything depended on what happened after the engines ignited.
• 53:50
  Speaker 1: On the 25th of December 2021, after decades of planning, redesigning, testing, delaying,
• 53:59
  Speaker 1: and wondering whether the telescope would ever actually leave Earth,
• 54:03
  Speaker 1: the James Webb Space Telescope finally reached the top of
• 54:06
  Speaker 1: its rocket. It was Christmas morning at Europe's spaceport near
• 54:10
  Speaker 1: Kourou in French Guiana. Inside the payload fairing of an
• 54:15
  Speaker 1: Ariane Space Ariane 5 rocket sat an observatory unlike anything
• 54:20
  Speaker 1: that had ever been launched before. The European Space Agency
• 54:25
  Speaker 1: had supplied the Ariane 5 launch as part of the
• 54:27
  Speaker 1: wider international partnership behind Webb. The National Aeronautics and Space
• 54:32
  Speaker 1: Administration led the mission. The European Space Agency contributed major
• 54:37
  Speaker 1: hardware and launch support. The Canadian Space Agency supplied important
• 54:41
  Speaker 1: scientific and guidance systems. Years of international work had been
• 54:46
  Speaker 1: reduced for a few tense minutes to one question. Would
• 54:49
  Speaker 1: the rocket carry Webb safely into space? At first glance,
• 54:54
  Speaker 1: that sounds like the obvious challenge. Rocket launches are violent events.
• 54:58
  Speaker 1: The vehicle shakes. Engines produce enormous forces. The payload experiences
• 55:04
  Speaker 1: intense vibration and acceleration, and every component has to survive.
• 55:10
  Speaker 1: But Webb had an additional problem. It could not be
• 55:12
  Speaker 1: launched in the shape it would eventually use. Its primary
• 55:16
  Speaker 1: mirror was far too wide. Its sunshield was far too large.
• 55:21
  Speaker 1: Its secondary mirror and supporting structures extended far beyond the
• 55:25
  Speaker 1: available space inside the rocket. So the observatory had been folded.
• 55:30
  Speaker 1: The enormous mirror wings were tucked inward. The five-layer sunshield
• 55:35
  Speaker 1: was carefully packed away. Support structures were collapsed. Components that
• 55:40
  Speaker 1: would later spread across an area larger than a tennis
• 55:42
  Speaker 1: court had been compressed into a package small enough to
• 55:45
  Speaker 1: fit inside the rocket's protective fairing. This meant that a
• 55:49
  Speaker 1: successful launch would not produce a finished telescope. It would
• 55:53
  Speaker 1: produce a folded telescope travelling through space. That distinction mattered enormously.
• 56:00
  Speaker 1: Even if the Ariane 5 performed perfectly, Webb would still
• 56:03
  Speaker 1: have to transform itself after launch. It would have to unfold.
• 56:07
  Speaker 1: Its solar array would have to deploy. Its communication systems
• 56:11
  Speaker 1: would have to work. Its sunshield would have to open
• 56:15
  Speaker 1: and tension correctly. Its mirrors would have to move into position,
• 56:19
  Speaker 1: its instruments would eventually need to cool, and its 18
• 56:23
  Speaker 1: mirror segments would later have to be aligned with extraordinary precision.
• 56:28
  Speaker 1: The launch was only the first hurdle. Still, it was
• 56:31
  Speaker 1: quite a hurdle. At around twenty past twelve in the
• 56:35
  Speaker 1: afternoon local time, the Ariane 5 lifted away from the
• 56:38
  Speaker 1: launch pad. The rocket climbed over the Atlantic Ocean, carrying
• 56:42
  Speaker 1: Webb upward through the atmosphere. For the observatory itself, there
• 56:46
  Speaker 1: was very little to do during those first minutes. It
• 56:49
  Speaker 1: was simply a passenger. Years of careful engineering could not
• 56:53
  Speaker 1: control the rocket once the engines had ignited. The Ariane
• 56:57
  Speaker 1: 5 had to do its job. Roughly 27 minutes after liftoff,
• 57:02
  Speaker 1: Webb separated from the rocket's upper stage. For the first time,
• 57:07
  Speaker 1: it was flying independently through space. Only moments later, one
• 57:12
  Speaker 1: of the first crucial automated deployments began. Its solar array unfolded.
• 57:18
  Speaker 1: This was essential because the observatory needed electrical power. The
• 57:22
  Speaker 1: deployment happened shortly after separation, and the array began converting
• 57:27
  Speaker 1: sunlight into electricity for Webb's onboard systems. That was one
• 57:31
  Speaker 1: small step completed. Many more remained. The rocket itself had
• 57:36
  Speaker 1: performed exceptionally well. In fact, the Ariane 5 placed Webb
• 57:40
  Speaker 1: onto its outbound trajectory. with such precision that the observatory
• 57:45
  Speaker 1: needed less propellant than expected for its early course corrections.
• 57:49
  Speaker 1: This turned out to be surprisingly important. Webb carries a
• 57:53
  Speaker 1: limited supply of propellant used for trajectory corrections and for
• 57:57
  Speaker 1: maintaining its orbit later in the mission. Every unnecessary correction
• 58:01
  Speaker 1: would have consumed some of that reserve. Because the launch
• 58:04
  Speaker 1: trajectory was so accurate, Webb could conserve more fuel. That
• 58:08
  Speaker 1: conservation eventually improved expectations for how long the observatory might
• 58:12
  Speaker 1: remain operational. A few extra metres per second of unwanted
• 58:16
  Speaker 1: velocity might sound trivial in ordinary conversation. For a spacecraft
• 58:20
  Speaker 1: expected to operate for years or decades, it can matter
• 58:24
  Speaker 1: a great deal. And Webb was heading somewhere very far away.
• 58:28
  Speaker 1: Its destination lay roughly one and a half million kilometres
• 58:31
  Speaker 1: from Earth. That is several times farther away than the Moon. Hubble,
• 58:36
  Speaker 1: by comparison, circles Earth only a few hundred kilometres above
• 58:40
  Speaker 1: the surface. Astronauts were able to visit Hubble multiple times.
• 58:44
  Speaker 1: They repaired it. They replaced instruments. They upgraded systems. There
• 58:49
  Speaker 1: was no equivalent plan waiting for Webb. Once it began
• 58:53
  Speaker 1: travelling outward, the distance between the telescope and Earth increased rapidly.
• 58:58
  Speaker 1: If something failed, nobody was preparing to climb aboard another
• 59:01
  Speaker 1: spacecraft and go and fix it. That reality had shaped
• 59:05
  Speaker 1: the entire mission. components had been tested repeatedly because many
• 59:10
  Speaker 1: of them would get only one chance to work. A
• 59:13
  Speaker 1: hinge might spend years folded on Earth and then be
• 59:16
  Speaker 1: asked to move once in space. A release mechanism might
• 59:19
  Speaker 1: be fired a single time. A cable, latch, motor, bearing
• 59:24
  Speaker 1: or actuator might perform one crucial action and never need
• 59:28
  Speaker 1: to repeat it. The telescope depended on a long chain
• 59:32
  Speaker 1: of these events, and because so many parts were interconnected,
• 59:35
  Speaker 1: one failure could potentially affect many others. The emotional stakes
• 59:39
  Speaker 1: were enormous, but the process itself was methodical. Mission controllers
• 59:45
  Speaker 1: watched telemetry. Engineers checked temperatures, electrical systems, communications, orientation, and
• 59:51
  Speaker 1: the health of Webb's many subsystems. The observatory continued drifting
• 59:56
  Speaker 1: farther from Earth. There was no dramatic change in scenery.
• 1:00:00
  Speaker 1: No horizon disappeared behind it. No sudden moment made the
• 1:00:04
  Speaker 1: distance feel real. Just numbers increasing quietly on screens, Columbia's
• 1:00:10
  Speaker 1: becoming tens of thousands, then hundreds of thousands. And while
• 1:00:15
  Speaker 1: that distance grew, Webb began the complicated task of turning
• 1:00:19
  Speaker 1: itself from a tightly packed spacecraft into a working observatory.
• 1:00:23
  Speaker 1: The National Aeronautics and Space Administration described this early journey
• 1:00:27
  Speaker 1: as the 29 days on the edge. the name was appropriate.
• 1:00:31
  Speaker 1: Launching the telescope had required decades of work, but now
• 1:00:36
  Speaker 1: Webb had to perform the part that could never be
• 1:00:38
  Speaker 1: fully rehearsed in the place where it would actually happen.
• 1:00:42
  Speaker 1: In the silence of space, moving farther from Earth each hour,
• 1:00:44
  Speaker 1: it had to unfold itself. What left Earth on Christmas
• 1:00:48
  Speaker 1: morning was not yet a complete telescope in the form
• 1:00:51
  Speaker 1: that astronomers had designed it to use. It was a
• 1:00:53
  Speaker 1: tightly folded machine. Inside the Ariane 5 rocket, Webb had
• 1:00:58
  Speaker 1: been compressed into a shape compact enough to survive launch.
• 1:01:02
  Speaker 1: Its mirror wings were folded inward. Its enormous sunshield was
• 1:01:06
  Speaker 1: packed away. Its secondary mirror support structure had not yet extended.
• 1:01:11
  Speaker 1: Many of the components that would eventually give the observatory
• 1:01:14
  Speaker 1: its full size were still locked firmly in place. Once
• 1:01:18
  Speaker 1: completely deployed, Webb would measure roughly 21 metres from end
• 1:01:21
  Speaker 1: to end. and around 14 metres across. The telescope therefore
• 1:01:28
  Speaker 1: had to perform an extraordinary transformation while already travelling through space,
• 1:01:32
  Speaker 1: and it had to do so without anyone nearby to help.
• 1:01:36
  Speaker 1: The deployment sequence contained more than 50 major steps. Those
• 1:01:40
  Speaker 1: steps depended on 178 release mechanisms, together with motors, hinges, cables, pulleys, bearings,
• 1:01:50
  Speaker 1: latches and actuators. Some components moved only once in the
• 1:01:54
  Speaker 1: entire mission. A mechanism might remain folded and restrained for
• 1:01:59
  Speaker 1: years on Earth, survive transport and launch, then receive a
• 1:02:03
  Speaker 1: single command in space and be expected to perform perfectly.
• 1:02:09
  Speaker 1: Engineers had identified more than 300 potential single points of
• 1:02:13
  Speaker 1: failure associated with the deployment. A single point of failure
• 1:02:17
  Speaker 1: is exactly what the name suggests. It is a part
• 1:02:20
  Speaker 1: of the system for which one particular failure could not
• 1:02:23
  Speaker 1: simply be bypassed by an identical backup doing the same job.
• 1:02:28
  Speaker 1: Not every such failure would necessarily have destroyed the entire observatory,
• 1:02:32
  Speaker 1: but some could have seriously reduced its scientific capability, while
• 1:02:36
  Speaker 1: others could have ended the mission before meaningful observations had
• 1:02:40
  Speaker 1: even begun. This was why Webb's deployment had generated so
• 1:02:45
  Speaker 1: much anxiety long before launch. The most complicated element was
• 1:02:49
  Speaker 1: the sunshield. During launch, its five delicate layers had been
• 1:02:54
  Speaker 1: folded and restrained against the spacecraft. Now they had to
• 1:02:59
  Speaker 1: become a structure roughly the size of a tennis court. First,
• 1:03:03
  Speaker 1: protective covers and restraints had to be released. Then the
• 1:03:06
  Speaker 1: structures supporting the shield had to begin moving outward. Long
• 1:03:11
  Speaker 1: booms extended to either side, pulling the folded membranes with
• 1:03:15
  Speaker 1: them and gradually spreading the shield into its broad diamond-like shape.
• 1:03:20
  Speaker 1: But opening it was only part of the task. The
• 1:03:23
  Speaker 1: five layers could not simply remain pressed together. They had
• 1:03:27
  Speaker 1: to be separated. Each one needed space around it so
• 1:03:31
  Speaker 1: that heat absorbed from the sun-facing side could radiate away
• 1:03:35
  Speaker 1: rather than simply passing directly into the next layer. Cables
• 1:03:40
  Speaker 1: and motors gradually pulled the layers apart. Then came tensioning,
• 1:03:44
  Speaker 1: Each membrane had to be drawn into its proper shape,
• 1:03:47
  Speaker 1: one layer at a time, until the five thin sheets
• 1:03:50
  Speaker 1: formed the thermal barrier Webb needed. The material was astonishingly thin,
• 1:03:56
  Speaker 1: yet its position mattered enormously. Too much slack, an incorrect fold,
• 1:04:01
  Speaker 1: or a problem with one of the mechanisms controlling the
• 1:04:04
  Speaker 1: membranes could have affected the telescope's ability to remain cold
• 1:04:07
  Speaker 1: enough for infrared astronomy. The deployment therefore proceeded carefully. It
• 1:04:13
  Speaker 1: was not simply a case of pressing one button and
• 1:04:15
  Speaker 1: hoping the telescope would unfold itself while everyone watched helplessly.
• 1:04:20
  Speaker 1: Webb had many automated systems, but mission controllers remained deeply involved.
• 1:04:26
  Speaker 1: Teams at the Space Telescope Science Institute and Mission Operations
• 1:04:30
  Speaker 1: Centres monitored telemetry from the observatory throughout the process. They
• 1:04:35
  Speaker 1: could examine temperatures, electrical currents, motor behaviour, positions and other
• 1:04:41
  Speaker 1: indicators of how systems were responding. Procedures could be paused.
• 1:04:46
  Speaker 1: Timing could be adjusted. Engineers could study the information coming
• 1:04:51
  Speaker 1: back from the spacecraft before deciding to continue. That flexibility mattered,
• 1:04:57
  Speaker 1: because the real observatory was now operating in space, not
• 1:05:01
  Speaker 1: inside a test facility. The deployment schedule was therefore treated
• 1:05:05
  Speaker 1: as a sequence to be managed rather than a stopwatch
• 1:05:08
  Speaker 1: that had to be obeyed regardless of conditions. Once the
• 1:05:12
  Speaker 1: sunshield had been successfully opened and tensioned, attention moved to
• 1:05:17
  Speaker 1: other structures. The secondary mirror was especially important. This smaller
• 1:05:22
  Speaker 1: mirror sits well in front of the primary mirror, supported
• 1:05:26
  Speaker 1: by a long structure that had been folded for launch.
• 1:05:29
  Speaker 1: Without it, the great golden primary mirror would have nowhere
• 1:05:32
  Speaker 1: useful to send the light it collected. The support structure
• 1:05:36
  Speaker 1: extended outward until the secondary mirror reached its operating position.
• 1:05:40
  Speaker 1: Then came the primary mirror wings. Webb's central mirror section
• 1:05:44
  Speaker 1: had already been exposed, but the groups of outer mirror
• 1:05:47
  Speaker 1: segments on either side remained folded backward. One wing moved
• 1:05:52
  Speaker 1: into place, then the other. On 8 January 2022, the
• 1:05:57
  Speaker 1: second primary mirror wing locked into position. The major physical
• 1:06:01
  Speaker 1: deployment of the observatory was complete. Less than two weeks
• 1:06:05
  Speaker 1: after launch, Webb finally resembled the telescope people had seen
• 1:06:09
  Speaker 1: in illustrations for years. But it was not yet ready
• 1:06:13
  Speaker 1: to do astronomy. Its first month in space also involved
• 1:06:17
  Speaker 1: course corrections, cooling, instrument activation and and the gradual movement
• 1:06:22
  Speaker 1: of the mirror segments away from their protected launch positions.
• 1:06:26
  Speaker 1: The telescope was also continuing toward the region, where it
• 1:06:29
  Speaker 1: would eventually carry out its observations, and even after arriving there,
• 1:06:34
  Speaker 1: one of the most delicate jobs remained. The 18 primary
• 1:06:38
  Speaker 1: mirror segments had to be aligned. Although they now formed
• 1:06:41
  Speaker 1: the familiar golden shape of Webb's primary mirror, they were
• 1:06:45
  Speaker 1: still 18 separate optical surfaces. If they pointed in slightly
• 1:06:50
  Speaker 1: different directions, they would not produce one sharp image. Early
• 1:06:54
  Speaker 1: alignment tests demonstrated this very clearly. When Webb observed a
• 1:06:58
  Speaker 1: bright star, each mirror segment initially produced its own image.
• 1:07:03
  Speaker 1: Instead of one star, the detectors could see a scattered
• 1:07:06
  Speaker 1: collection of separate points. This was expected. Over the following months,
• 1:07:11
  Speaker 1: engineers adjusted the segments using extremely precise actuators behind each mirror.
• 1:07:17
  Speaker 1: The positions changed by tiny amounts. Some adjustments were measured
• 1:07:22
  Speaker 1: on scales far smaller than the width of a human hair.
• 1:07:26
  Speaker 1: The goal was to make light reflected from all 18
• 1:07:29
  Speaker 1: segments arrive at the correct place with extraordinary precision. Gradually,
• 1:07:36
  Speaker 1: the separate star images were brought together. The process moved
• 1:07:40
  Speaker 1: from rough alignment to increasingly fine adjustments until the 18
• 1:07:46
  Speaker 1: mirrors began behaving optically like one enormous mirror six and
• 1:07:50
  Speaker 1: a half metres across. At the same time, Webb continued cooling.
• 1:07:55
  Speaker 1: Its instruments were checked, detectors were calibrated, pointing systems were tested.
• 1:08:01
  Speaker 1: The observatory that had spent years folded inside clean rooms
• 1:08:05
  Speaker 1: and test facilities was slowly becoming a scientific instrument. And
• 1:08:11
  Speaker 1: after all the concern surrounding the deployment, Something almost surprising happened.
• 1:08:16
  Speaker 1: It worked remarkably smoothly. The sunshield opened. The secondary mirror deployed.
• 1:08:23
  Speaker 1: Both primary mirror wings moved into place. The mirror segments
• 1:08:27
  Speaker 1: responded to alignment commands. The telescope survived the sequence of
• 1:08:32
  Speaker 1: events that had occupied engineers for years. There had been
• 1:08:35
  Speaker 1: no single dramatic rescue. No improvised repair. Just hundreds of
• 1:08:41
  Speaker 1: carefully designed actions occurring one after another, until the folded
• 1:08:45
  Speaker 1: spacecraft had become the observatory people had spent decades trying
• 1:08:49
  Speaker 1: to build. Webb no longer needed to unfold itself, but
• 1:08:53
  Speaker 1: to perform the science it had been designed for it
• 1:08:56
  Speaker 1: still needed an unusually cold and stable place to live.
• 1:09:00
  Speaker 1: And that place lay far beyond the Moon, in a
• 1:09:03
  Speaker 1: region of space defined by the combined gravitational motion of
• 1:09:06
  Speaker 1: Earth and the Sun. By the time Webb had finished
• 1:09:09
  Speaker 1: unfolding and aligning its enormous mirror, it was already far
• 1:09:13
  Speaker 1: from Earth. Its destination was not another planet, nor a
• 1:09:18
  Speaker 1: conventional orbit around our own. Instead, the telescope was heading
• 1:09:22
  Speaker 1: toward a region of space near what is known as
• 1:09:25
  Speaker 1: the second Lagrange point. This region lies roughly one and
• 1:09:29
  Speaker 1: a half million kilometres from Earth, in the direction opposite
• 1:09:32
  Speaker 1: the Sun. That is around four times farther away than
• 1:09:36
  Speaker 1: the Moon. At first, the idea of a Lagrange point
• 1:09:39
  Speaker 1: can sound more mysterious than it really is. It is
• 1:09:42
  Speaker 1: not a hidden object. There is no invisible platform waiting
• 1:09:46
  Speaker 1: in space. A Lagrange point is simply a region, where
• 1:09:50
  Speaker 1: the gravitational influence of two large bodies, combined with the
• 1:09:54
  Speaker 1: motion of a smaller object travelling with them, can create
• 1:09:57
  Speaker 1: a useful kind of balance. In Webb's case, the two
• 1:10:01
  Speaker 1: large bodies are the Sun and Earth. The mathematical ideas
• 1:10:04
  Speaker 1: behind these regions are connected to the 18th century work
• 1:10:07
  Speaker 1: of the mathematician Joseph-Louis Lagrange, who studied what is known
• 1:10:11
  Speaker 1: as the restricted three-body problem. This is the problem of
• 1:10:15
  Speaker 1: predicting the motion of a relatively small object under the
• 1:10:18
  Speaker 1: gravity of two much more massive bodies. The complete behaviour
• 1:10:22
  Speaker 1: can become extremely complicated, but under particular conditions there are
• 1:10:27
  Speaker 1: certain regions where the small object can remain in a
• 1:10:30
  Speaker 1: fairly stable relationship with the larger pair. These became known
• 1:10:34
  Speaker 1: as Lagrange points. There are five principal Lagrange points associated
• 1:10:38
  Speaker 1: with a two-body system, such as the Sun and Earth.
• 1:10:42
  Speaker 1: For Webb, the useful one is the second. It lies
• 1:10:46
  Speaker 1: beyond Earth when viewed from the Sun. So if you
• 1:10:49
  Speaker 1: imagined a line running outward from the Sun, through Earth
• 1:10:53
  Speaker 1: and continuing into space, the second Lagrange point would lie
• 1:10:57
  Speaker 1: far beyond our planet along that general direction. There is
• 1:11:01
  Speaker 1: an important detail here. Webb does not simply sit motionless
• 1:11:05
  Speaker 1: at that exact point. It follows a large orbit around
• 1:11:08
  Speaker 1: the region. This type of path is often described as
• 1:11:11
  Speaker 1: a halo orbit. At the same time, the entire system
• 1:11:16
  Speaker 1: is moving around the Sun along with Earth. So Webb
• 1:11:19
  Speaker 1: is constantly in motion. It travels around the second Lagrange point,
• 1:11:24
  Speaker 1: while the second Lagrange point itself travels around the Sun
• 1:11:26
  Speaker 1: with our planet. That sounds more complicated than placing the
• 1:11:30
  Speaker 1: telescope in a simple orbit around Earth. But for infrared astronomy,
• 1:11:34
  Speaker 1: it is an exceptionally useful arrangement. The main reason is geometry.
• 1:11:39
  Speaker 1: From Webb's perspective, the Sun, Earth and Moon all remain
• 1:11:43
  Speaker 1: in roughly the same general direction. That means the telescope
• 1:11:47
  Speaker 1: can keep its enormous sunshield facing them. The warm side
• 1:11:51
  Speaker 1: of the observatory absorbs and reflects radiation from that direction.
• 1:11:55
  Speaker 1: The mirror and scientific instruments remain on the opposite side,
• 1:11:58
  Speaker 1: protected in the deep cold created by the shield. This
• 1:12:02
  Speaker 1: is sometimes described by saying Webb lives in permanent shade.
• 1:12:06
  Speaker 1: That is a useful shorthand. but it is not quite
• 1:12:09
  Speaker 1: the whole story. The second Lagrange point itself is not
• 1:12:12
  Speaker 1: some naturally dark pocket where sunlight disappears. Webb remains exposed
• 1:12:17
  Speaker 1: to the space around it. What matters is the observatory's orientation.
• 1:12:22
  Speaker 1: The telescope carefully keeps the sunshield positioned between the warm
• 1:12:26
  Speaker 1: sources of radiation and the cold optical system. The shadow
• 1:12:30
  Speaker 1: is therefore created by Webb itself. That constant orientation is
• 1:12:35
  Speaker 1: one of the reasons the telescope can remain cold enough
• 1:12:38
  Speaker 1: to detect faint infrared signals from across the universe. Its
• 1:12:43
  Speaker 1: location also provides a relatively stable thermal environment. A telescope
• 1:12:48
  Speaker 1: repeatedly moving between sunlight and darkness would continually heat and cool.
• 1:12:55
  Speaker 1: That would be troublesome for an observatory relying on extremely
• 1:12:58
  Speaker 1: precise mirrors and very sensitive instruments. At Webb's operating location,
• 1:13:03
  Speaker 1: the thermal conditions can remain much steadier. This arrangement is
• 1:13:08
  Speaker 1: very different from the one used by the Hubble Space Telescope.
• 1:13:11
  Speaker 1: Hubble orbits only a few hundred kilometres above Earth. That
• 1:13:15
  Speaker 1: is close enough that astronauts were able to visit it
• 1:13:17
  Speaker 1: during several servicing missions. Those missions became an important part
• 1:13:22
  Speaker 1: of Hubble's history. Astronauts repaired equipment, replaced instruments, upgraded systems,
• 1:13:29
  Speaker 1: and corrected problems that would otherwise have limited the telescope's usefulness.
• 1:13:34
  Speaker 1: Webb was designed around a completely different philosophy. At roughly
• 1:13:39
  Speaker 1: one and a half million kilometres from Earth, it lies
• 1:13:41
  Speaker 1: far beyond the region reached by Hubble servicing missions. No
• 1:13:46
  Speaker 1: astronaut repair programme was built into the mission. The telescope
• 1:13:49
  Speaker 1: was designed to work remotely. If a component failed, engineers
• 1:13:54
  Speaker 1: on Earth could sometimes compensate through software, altered procedures or
• 1:13:59
  Speaker 1: redundant systems. But they could not simply send a crew
• 1:14:03
  Speaker 1: to replace a broken part. That made reliability essential from
• 1:14:07
  Speaker 1: the beginning. Even so, Webb's orbit is not completely maintenance-free.
• 1:14:11
  Speaker 1: The observatory must occasionally perform station-keeping manoeuvres. These small burns
• 1:14:17
  Speaker 1: help maintain the desired path around the second Lagrange point.
• 1:14:20
  Speaker 1: Without them, tiny gravitational influences and other effects would gradually
• 1:14:25
  Speaker 1: alter the orbit. Webb also needs to manage its orientation.
• 1:14:30
  Speaker 1: Sunlight pushing on the large sunshield creates a small but
• 1:14:33
  Speaker 1: continuous force. Over time, this can build up rotational momentum
• 1:14:38
  Speaker 1: inside the spacecraft's reaction wheels, which are used to control pointing.
• 1:14:43
  Speaker 1: The observatory therefore occasionally performs momentum management manoeuvres to keep
• 1:14:48
  Speaker 1: these systems within their operating limits. These corrections consume propellant,
• 1:14:54
  Speaker 1: and that matters because Webb carries only a finite amount.
• 1:14:58
  Speaker 1: The available propellant helps place an eventual limit on how
• 1:15:01
  Speaker 1: long the spacecraft can maintain its orbit and orientation. Fortunately,
• 1:15:05
  Speaker 1: the exceptionally accurate launch preserved more fuel than originally expected,
• 1:15:10
  Speaker 1: improving the mission's potential lifespan. But even while this distant
• 1:15:15
  Speaker 1: position makes Webb difficult to reach, it is precisely what
• 1:15:19
  Speaker 1: allows the telescope to do its work so well. Far
• 1:15:23
  Speaker 1: from the warmth of Earth, protected from the Sun by
• 1:15:26
  Speaker 1: its enormous shield and kept in a relatively stable thermal environment,
• 1:15:31
  Speaker 1: Webb can remain extraordinarily cold. That gives its instruments the
• 1:15:36
  Speaker 1: quiet infrared background they need. And from there, more than
• 1:15:41
  Speaker 1: a million kilometres from home, the telescope can detect kinds
• 1:15:44
  Speaker 1: of light that would be far harder to observe from
• 1:15:47
  Speaker 1: Earth's surface. It can see through dust, it can measure
• 1:15:51
  Speaker 1: faint heat, and it can collect ancient infrared radiation that
• 1:15:55
  Speaker 1: has crossed the universe for billions of years before finally
• 1:15:58
  Speaker 1: reaching its mirror. From its cold position far beyond the moon,
• 1:16:03
  Speaker 1: Webb spends much of its time looking at a universe
• 1:16:06
  Speaker 1: that human eyes could never see directly. The night sky
• 1:16:10
  Speaker 1: we experience is shaped by a surprisingly narrow window of light.
• 1:16:15
  Speaker 1: Human vision responds to what we call visible light, but
• 1:16:19
  Speaker 1: visible light is only a tiny part of the much
• 1:16:21
  Speaker 1: larger electromagnetic spectrum. At one end of that spectrum are
• 1:16:26
  Speaker 1: very short wavelengths, including gamma rays and X-rays. Moving through
• 1:16:32
  Speaker 1: longer wavelengths brings us to ultraviolet light, then the narrow
• 1:16:36
  Speaker 1: visible range our eyes detect. Beyond visible red lies infrared.
• 1:16:42
  Speaker 1: Farther still are microwaves and radio waves. All of these
• 1:16:45
  Speaker 1: are forms of electromagnetic radiation. They differ mainly in wavelength
• 1:16:50
  Speaker 1: and frequency. So infrared light is not an exotic substance
• 1:16:55
  Speaker 1: fundamentally different from the light coming through a window on
• 1:16:58
  Speaker 1: a sunny afternoon. It is the same broad physical phenomenon,
• 1:17:03
  Speaker 1: simply occupying wavelengths beyond the red edge of human vision.
• 1:17:07
  Speaker 1: Our eyes happen not to have evolved detectors for it.
• 1:17:11
  Speaker 1: Webb has. This is why images from the James Webb
• 1:17:15
  Speaker 1: Space Telescope should not be imagined as photographs, showing exactly
• 1:17:19
  Speaker 1: what a human astronaut would see if somehow floating beside
• 1:17:23
  Speaker 1: the observatory. The detectors measure infrared light that our eyes
• 1:17:28
  Speaker 1: cannot perceive. Astronomers then assign visible colours to different infrared wavelengths,
• 1:17:33
  Speaker 1: so that those measurements can be displayed in a form
• 1:17:36
  Speaker 1: we can examine. The colours can therefore carry scientific information,
• 1:17:41
  Speaker 1: even though they are translations of invisible light. Infrared radiation
• 1:17:45
  Speaker 1: is often casually described as heat. There is some truth
• 1:17:49
  Speaker 1: behind that description, but it needs a little care. Infrared
• 1:17:53
  Speaker 1: does not simply mean heat, it is electromagnetic radiation. Warm
• 1:17:58
  Speaker 1: objects often emit strongly at infrared wavelengths because all matter
• 1:18:02
  Speaker 1: above absolute zero emits thermal radiation, with the pattern depending
• 1:18:07
  Speaker 1: on temperature. A human body, a warm rock, a planet,
• 1:18:12
  Speaker 1: a cloud of dust, and the telescope itself can all
• 1:18:15
  Speaker 1: produce infrared radiation. This is precisely why Webb has to
• 1:18:19
  Speaker 1: remain so cold. But infrared photons can originate in many
• 1:18:24
  Speaker 1: other ways as well. They may begin as starlight. They
• 1:18:27
  Speaker 1: may be produced by atoms or molecules changing energy states,
• 1:18:32
  Speaker 1: they may come from warm dust surrounding a newborn star,
• 1:18:35
  Speaker 1: or they may have started their journey as ultraviolet or
• 1:18:38
  Speaker 1: visible light billions of years ago, only to be stretched
• 1:18:41
  Speaker 1: into infrared wavelengths as the universe expanded. That versatility makes
• 1:18:46
  Speaker 1: infrared astronomy enormously powerful. It also gives Webb a remarkable
• 1:18:51
  Speaker 1: ability to see into places that can remain hidden at
• 1:18:54
  Speaker 1: visible wavelengths. Space may look wonderfully clear in photographs, but
• 1:18:58
  Speaker 1: the regions between stars are not completely empty. They contain
• 1:19:02
  Speaker 1: gas and tiny solid particles collectively known as interstellar dust.
• 1:19:07
  Speaker 1: These dust grains are usually microscopic, Many contain materials such
• 1:19:11
  Speaker 1: as silicates, carbon-rich compounds and tiny particles incorporating heavier elements
• 1:19:18
  Speaker 1: produced by earlier generations of stars. Individually, they are insignificant.
• 1:19:23
  Speaker 1: Collected across vast clouds, however, they can have a dramatic
• 1:19:27
  Speaker 1: effect on light. Dust absorbs and scatters electromagnetic radiation. Shorter
• 1:19:33
  Speaker 1: visible wavelengths are often particularly affected meaning that a dense
• 1:19:37
  Speaker 1: cloud can hide whatever lies behind or inside it. A
• 1:19:42
  Speaker 1: star-forming region viewed in visible light can therefore appear as
• 1:19:46
  Speaker 1: a dark patch or thick silhouette. That darkness does not
• 1:19:50
  Speaker 1: mean the region is empty. Quite often the opposite is true.
• 1:19:54
  Speaker 1: Inside some of these clouds gravity is pulling gas and
• 1:19:57
  Speaker 1: dust together, dense pockets collapse, material gathers around growing objects
• 1:20:03
  Speaker 1: and new stars begin forming. These extremely young stars are
• 1:20:08
  Speaker 1: called protostars. A protostar may still be buried deeply inside
• 1:20:12
  Speaker 1: the cloud from which it formed, surrounded by dust that
• 1:20:15
  Speaker 1: makes it difficult or impossible to study clearly in ordinary
• 1:20:18
  Speaker 1: visible light. Infrared wavelengths can penetrate some dusty environments more effectively.
• 1:20:25
  Speaker 1: The reason is that the interaction between radiation and dust
• 1:20:28
  Speaker 1: depends strongly on wavelength. Longer infrared wavelengths are often scattered.
• 1:20:33
  Speaker 1: and absorbed less strongly by the small grains than visible
• 1:20:37
  Speaker 1: light is. The cloud therefore becomes more transparent. It is
• 1:20:41
  Speaker 1: not that infrared passes effortlessly through every possible concentration of dust.
• 1:20:46
  Speaker 1: Very dense material can still block it. But compared with
• 1:20:50
  Speaker 1: visible light, infrared observations can reveal structures and objects that
• 1:20:54
  Speaker 1: would otherwise remain concealed. For Webb, this means looking into
• 1:20:59
  Speaker 1: stellar nurseries and finding stars that are still in the
• 1:21:02
  Speaker 1: process of being born. It can study the disks of
• 1:21:05
  Speaker 1: gas and dust surrounding young stars where planets may eventually form.
• 1:21:10
  Speaker 1: These protoplanetary disks contain the raw material from which future
• 1:21:14
  Speaker 1: planetary systems can emerge. Dust grains collide and sometimes stick together.
• 1:21:20
  Speaker 1: Larger bodies gradually form. Over enormous periods of time, some
• 1:21:25
  Speaker 1: may grow into planets, moons, asteroids and comets. Infrared observations
• 1:21:31
  Speaker 1: allow astronomers to investigate the temperatures, chemistry and structure of
• 1:21:36
  Speaker 1: these environments while the process is still underway. Dust also
• 1:21:40
  Speaker 1: hides activity on much larger scales. At the centres of
• 1:21:44
  Speaker 1: some galaxies lie actively feeding supermassive black holes. The black
• 1:21:49
  Speaker 1: hole itself emits no light from inside its event horizon,
• 1:21:53
  Speaker 1: but matter spiralling toward it can become extraordinarily hot and luminous.
• 1:21:58
  Speaker 1: Such a system is known as an active galactic nucleus.
• 1:22:02
  Speaker 1: Gas and dust surrounding that region can obscure much of
• 1:22:05
  Speaker 1: the radiation at visible wavelengths. Infrared observations can reveal heated
• 1:22:10
  Speaker 1: dust and other signatures of the hidden activity, giving astronomers
• 1:22:14
  Speaker 1: another way to investigate what is happening around a distant
• 1:22:17
  Speaker 1: black hole. But Webb does not merely take infrared pictures.
• 1:22:22
  Speaker 1: Some of its most powerful measurements come from breaking light apart.
• 1:22:26
  Speaker 1: This is the role of spectroscopy. A spectrograph separates incoming
• 1:22:30
  Speaker 1: light according to wavelength, producing a spectrum. At first glance,
• 1:22:36
  Speaker 1: a spectrum may seem less impressive than a detailed astronomical image.
• 1:22:40
  Speaker 1: It may appear as a line, a band, or a
• 1:22:43
  Speaker 1: pattern of peaks and dips. But hidden inside those patterns
• 1:22:46
  Speaker 1: is an extraordinary amount of information. Atoms and molecules interact
• 1:22:51
  Speaker 1: with particular wavelengths because their internal energy levels are quantized.
• 1:22:56
  Speaker 1: An atom may absorb light at certain wavelengths. A hot
• 1:23:00
  Speaker 1: gas may emit strongly at others. Molecules can produce more
• 1:23:04
  Speaker 1: complicated patterns associated with their rotations and vibrations. These features
• 1:23:09
  Speaker 1: act like fingerprints. Hydrogen leaves characteristic signatures. Oxygen produces others.
• 1:23:17
  Speaker 1: Carbon-bearing molecules produce their own patterns. Water vapour, carbon dioxide,
• 1:23:22
  Speaker 1: methane and many other substances can potentially reveal themselves through
• 1:23:26
  Speaker 1: the wavelengths they absorb or emit. Astronomers can therefore take
• 1:23:31
  Speaker 1: light arriving from an object that may never be physically
• 1:23:34
  Speaker 1: visited and begin reconstructing what that object is made of.
• 1:23:38
  Speaker 1: The same spectrum can reveal more than composition. The relative
• 1:23:42
  Speaker 1: strength of different features can provide clues about temperature and density.
• 1:23:47
  Speaker 1: Patterns produced by atoms in different ionisation states can show
• 1:23:51
  Speaker 1: how energetic the surrounding environment is. Ionisation occurs when an
• 1:23:57
  Speaker 1: atom loses or gains electrons. and the amount of ionisation
• 1:24:01
  Speaker 1: in a cloud of gas can tell astronomers about the
• 1:24:03
  Speaker 1: radiation and temperatures affecting it. Motion also leaves a signature.
• 1:24:09
  Speaker 1: When material moves toward or away from us, its spectral
• 1:24:13
  Speaker 1: features shift slightly in wavelength through the Doppler effect. Astronomers
• 1:24:19
  Speaker 1: can use this to investigate the movement of gas inside galaxies,
• 1:24:23
  Speaker 1: the winds flowing from stars, or material orbiting around massive objects.
• 1:24:29
  Speaker 1: Then there is cosmological redshift. If a distant galaxy's familiar
• 1:24:34
  Speaker 1: spectral features have all been shifted substantially toward longer wavelengths,
• 1:24:39
  Speaker 1: astronomers can measure that displacement and determine how much the
• 1:24:43
  Speaker 1: universe has expanded since the light began travelling toward us.
• 1:24:48
  Speaker 1: This turns a spectrum into a kind of cosmic timestamp.
• 1:24:52
  Speaker 1: A faint object consisting of only a few pixels can
• 1:24:56
  Speaker 1: suddenly become much more meaningful. Its light can reveal what
• 1:25:01
  Speaker 1: atoms are present. It can indicate conditions within its gas.
• 1:25:06
  Speaker 1: It can show where the material is moving. And its
• 1:25:09
  Speaker 1: redshift can place the object within a particular period of
• 1:25:12
  Speaker 1: cosmic history. This is where Webb's infrared design brings two
• 1:25:17
  Speaker 1: apparently different kinds of astronomy together. Nearby, infrared wavelengths allow
• 1:25:22
  Speaker 1: it to peer through dust and investigate hidden stars, protostars,
• 1:25:27
  Speaker 1: planetary systems and galactic centres. Far away, those same infrared
• 1:25:32
  Speaker 1: instruments detect ancient radiation that did not necessarily begin as
• 1:25:37
  Speaker 1: infrared at all. The expansion of space stretched that ancient
• 1:25:41
  Speaker 1: light until it arrived in exactly the wavelengths Webb was
• 1:25:45
  Speaker 1: built to detect. One ability allows Webb to look through
• 1:25:49
  Speaker 1: obscuring material, the other allows it to look through cosmic time,
• 1:25:53
  Speaker 1: And occasionally the object at the end of that journey
• 1:25:55
  Speaker 1: appears almost disappointingly small. A handful of faint pixels. A
• 1:26:00
  Speaker 1: tiny reddish patch against darkness. Nothing remotely as dramatic as
• 1:26:05
  Speaker 1: a nearby nebula filling an entire image. Yet those few
• 1:26:09
  Speaker 1: pixels may contain the combined light of millions or billions
• 1:26:13
  Speaker 1: of stars. They may belong to a galaxy seen at
• 1:26:16
  Speaker 1: a time when the universe was only a few hundred
• 1:26:18
  Speaker 1: million years old. The image may be tiny. The information
• 1:26:22
  Speaker 1: travelling inside its infrared light is anything but. When Webb
• 1:26:26
  Speaker 1: turns its mirror toward a seemingly empty patch of sky
• 1:26:29
  Speaker 1: and waits, the idea of a telescope as a time
• 1:26:32
  Speaker 1: machine becomes something much more tangible. At first, there may
• 1:26:37
  Speaker 1: appear to be very little there. But as the telescope
• 1:26:40
  Speaker 1: gathers more and more faint infrared light, the darkness begins
• 1:26:44
  Speaker 1: to fill. Thousands of galaxies emerge. Some are relatively nearby.
• 1:26:49
  Speaker 1: Others are billions of light-years farther away, and scattered among
• 1:26:53
  Speaker 1: them are tiny sources whose photons began travelling when the
• 1:26:56
  Speaker 1: universe was only a few hundred million years old. A
• 1:27:00
  Speaker 1: deep-field observation is therefore not simply a picture of distant space.
• 1:27:05
  Speaker 1: It is a picture containing many different periods of cosmic
• 1:27:08
  Speaker 1: history at once. One of Webb's first great demonstrations of
• 1:27:12
  Speaker 1: this came from an image centred on the galaxy cluster,
• 1:27:15
  Speaker 1: known as SMACS 0723. The field contains thousands of galaxies,
• 1:27:22
  Speaker 1: but one of its most useful features is the massive
• 1:27:25
  Speaker 1: cluster in the foreground. The cluster itself lies billions of
• 1:27:29
  Speaker 1: light years away and contains an enormous concentration of galaxies,
• 1:27:34
  Speaker 1: gas and dark matter. That mass changes the path of
• 1:27:38
  Speaker 1: light travelling through the space around it. This effect is
• 1:27:42
  Speaker 1: called gravitational lensing. It emerges naturally from Albert Einstein's general
• 1:27:47
  Speaker 1: theory of relativity. In Einstein's description of gravity, massive objects
• 1:27:53
  Speaker 1: do not simply pull on other things across empty space.
• 1:27:57
  Speaker 1: Mass and energy affect the geometry of spacetime itself. Light
• 1:28:01
  Speaker 1: follows path through that curved spacetime. So when light from
• 1:28:05
  Speaker 1: a very distant galaxy passes near a massive foreground object,
• 1:28:09
  Speaker 1: such as a large galaxy cluster, its path can be
• 1:28:12
  Speaker 1: bent before it reaches us. The result can look rather peculiar.
• 1:28:17
  Speaker 1: Background galaxies may appear stretched into arcs. Some can look distorted.
• 1:28:23
  Speaker 1: Others can appear in more than one place because their
• 1:28:25
  Speaker 1: light has travelled along different paths around the foreground mass.
• 1:28:29
  Speaker 1: Most importantly for astronomers searching the early universe, the lens
• 1:28:33
  Speaker 1: can also magnify distant objects. A massive galaxy cluster can
• 1:28:38
  Speaker 1: therefore behave like an enormous natural telescope. Webb supplies the
• 1:28:43
  Speaker 1: mirror and detectors, while gravity supplies an additional lens made
• 1:28:47
  Speaker 1: from galaxies and dark matter. This allows astronomers to study
• 1:28:51
  Speaker 1: background objects that might otherwise be too faint to detect clearly.
• 1:28:55
  Speaker 1: The first deep-field images were spectacular, but they were only
• 1:28:59
  Speaker 1: a beginning. Astronomers soon moved into much larger observing programmes
• 1:29:03
  Speaker 1: designed specifically to find and study the earliest galaxies. One
• 1:29:08
  Speaker 1: of the most important is the James Webb Space Telescope
• 1:29:11
  Speaker 1: Advanced Deep Extragalactic Survey. This programme combines extremely sensitive infrared
• 1:29:17
  Speaker 1: imaging with spectroscopy. That distinction is important because finding something
• 1:29:22
  Speaker 1: that looks like a very distant galaxy is not quite
• 1:29:26
  Speaker 1: the same as proving that it is one. astronomers can
• 1:29:29
  Speaker 1: use imaging through several different infrared filters to identify promising candidates.
• 1:29:35
  Speaker 1: A very distant galaxy may appear brightly in longer wavelength filters,
• 1:29:39
  Speaker 1: while disappearing in shorter wavelength ones. That pattern can happen
• 1:29:44
  Speaker 1: because neutral hydrogen absorbs light below particular wavelengths, while cosmic
• 1:29:48
  Speaker 1: expansion shifts the location of that break farther and farther
• 1:29:52
  Speaker 1: toward the infrared. From the colours alone, astronomers can estimate
• 1:29:56
  Speaker 1: a photometric redshift. That gives them a good idea of
• 1:30:00
  Speaker 1: how distant the object may be. But there is room
• 1:30:03
  Speaker 1: for confusion. A nearer galaxy containing dust, unusual stars, or
• 1:30:08
  Speaker 1: particular emission features can sometimes imitate the colours of something
• 1:30:12
  Speaker 1: much farther away. This is why spectroscopy is so valuable.
• 1:30:17
  Speaker 1: Instead of measuring only broad ranges of light, a spectrograph
• 1:30:21
  Speaker 1: separates the incoming radiation into many individual wavelengths. Astronomers can
• 1:30:27
  Speaker 1: then search for identifiable spectral features and measure exactly how
• 1:30:32
  Speaker 1: far those features have been shifted. That produces a spectroscopic redshift.
• 1:30:38
  Speaker 1: It is a much stronger way of establishing that a
• 1:30:41
  Speaker 1: galaxy really does belong in the extremely early universe. And
• 1:30:45
  Speaker 1: Webb has now pushed that confirmed frontier to extraordinary distances.
• 1:30:49
  Speaker 1: Astronomers have identified galaxies existing within roughly the first 300
• 1:30:54
  Speaker 1: million years after the Big Bang. One of the most
• 1:30:57
  Speaker 1: extreme examples is a galaxy known as MOMZ-14. Its measured
• 1:31:02
  Speaker 1: redshift is roughly 14.44. That places the galaxy at a
• 1:31:07
  Speaker 1: time only about 280 million years after the Big Bang.
• 1:31:12
  Speaker 1: In a universe now around 13.8 billion years old, this
• 1:31:16
  Speaker 1: means we are observing it at only about 2% of
• 1:31:18
  Speaker 1: the universe's present age. Its light has been travelling for
• 1:31:23
  Speaker 1: more than 13 billion years. But even that statement needs
• 1:31:26
  Speaker 1: a little care. It does not mean the galaxy is
• 1:31:29
  Speaker 1: presently only a little more than 13 billion light years
• 1:31:32
  Speaker 1: from us. While the photons were travelling, the universe continued expanding.
• 1:31:38
  Speaker 1: The space separating our region of the cosmos from that
• 1:31:40
  Speaker 1: galaxy grew during the journey. So the distance the light
• 1:31:44
  Speaker 1: travelled through cosmic history and the galaxy's present-day distance are
• 1:31:49
  Speaker 1: not the same quantity. At enormous cosmological scales, Ordinary intuition
• 1:31:55
  Speaker 1: about distance begins to become unreliable. But the more important
• 1:31:58
  Speaker 1: idea is beautifully simple. The photons Webb detects from a
• 1:32:02
  Speaker 1: galaxy like MomZ14 began their journey before Earth existed. They
• 1:32:08
  Speaker 1: were already travelling long before the Sun formed. They began
• 1:32:11
  Speaker 1: crossing the universe billions of years before our solar system
• 1:32:14
  Speaker 1: condensed from a cloud of gas and dust. Even the
• 1:32:17
  Speaker 1: Milky Way had not yet developed into the mature galaxy
• 1:32:20
  Speaker 1: we see around us today. Those photons passed through an
• 1:32:24
  Speaker 1: expanding universe for more than 13 billion years. Along the way,
• 1:32:29
  Speaker 1: their wavelengths stretched. The galaxy became increasingly remote. Stars were
• 1:32:34
  Speaker 1: born and died elsewhere. Galaxies collided, planets formed. On one
• 1:32:40
  Speaker 1: small planet, life appeared. Much later, one species learned to
• 1:32:44
  Speaker 1: build telescopes. And eventually, a small fraction of those ancient
• 1:32:48
  Speaker 1: photons reached a gold-coated mirror floating more than a million
• 1:32:52
  Speaker 1: kilometres from Earth. That is what makes these faint objects
• 1:32:56
  Speaker 1: so remarkable. In the image, they may look almost insignificant.
• 1:33:00
  Speaker 1: A small reddish patch, a blur covering only a few pixels.
• 1:33:04
  Speaker 1: Perhaps something you might overlook entirely if you did not
• 1:33:07
  Speaker 1: know what you were seeing. But that tiny patch can
• 1:33:10
  Speaker 1: contain an entire galaxy. Its light carries information about stars
• 1:33:15
  Speaker 1: forming when the cosmos itself was young. Spectroscopy can reveal hydrogen.
• 1:33:21
  Speaker 1: It can expose signs of chemical enrichment. It can tell
• 1:33:24
  Speaker 1: astronomers how vigorously stars were forming and begin to reveal
• 1:33:28
  Speaker 1: how rapidly the first generations of galaxies assembled. And as
• 1:33:32
  Speaker 1: more of these objects are confirmed, astronomers can begin doing
• 1:33:35
  Speaker 1: something even more powerful than finding individual record holders. They
• 1:33:40
  Speaker 1: can build a population. They can compare galaxies across different
• 1:33:44
  Speaker 1: moments in the first few hundred million years. They can
• 1:33:48
  Speaker 1: ask how quickly galaxies became massive. how efficiently they formed stars,
• 1:33:53
  Speaker 1: how rapidly heavier elements appeared, and how soon recognisable structures
• 1:33:57
  Speaker 1: began emerging from the early cosmic darkness. That is where
• 1:34:01
  Speaker 1: Webb begins to fulfil the extraordinary promise contained in the
• 1:34:05
  Speaker 1: idea of seeing the beginning of time. It is not
• 1:34:08
  Speaker 1: photographing the Big Bang. It cannot show us the universe
• 1:34:11
  Speaker 1: at the instant it began. But it is reaching deep
• 1:34:15
  Speaker 1: into the period when the first luminous structures were taking shape.
• 1:34:19
  Speaker 1: The ancient light arriving at Webb is giving us some
• 1:34:21
  Speaker 1: of the earliest surviving pages in the universe's visible history,
• 1:34:25
  Speaker 1: and after more than 13 billion years in transit, those
• 1:34:29
  Speaker 1: pages are finally beginning to come into focus. Webb's ability
• 1:34:33
  Speaker 1: to read faint infrared light is useful not only for
• 1:34:36
  Speaker 1: galaxies more than 13 billion years in the past, it
• 1:34:39
  Speaker 1: can also tell us about planets much closer to home. Closer,
• 1:34:43
  Speaker 1: at least, by astronomical standards. Thousands of planets are now
• 1:34:48
  Speaker 1: known to orbit stars beyond the solar system. These worlds
• 1:34:51
  Speaker 1: are called exoplanets, and they range from enormous gas giants
• 1:34:56
  Speaker 1: larger than Jupiter to planets only slightly larger than Earth.
• 1:35:01
  Speaker 1: For most of them, even Webb cannot simply take a
• 1:35:04
  Speaker 1: detailed photograph. An Earth-sized planet around another star is far
• 1:35:08
  Speaker 1: too small and distant to appear as a little globe
• 1:35:11
  Speaker 1: covered in oceans, clouds and continents. The beautiful images often
• 1:35:16
  Speaker 1: used to represent exoplanets are usually artistic interpretations based on
• 1:35:21
  Speaker 1: the scientific information available. The real observation may be nothing
• 1:35:25
  Speaker 1: more visually dramatic than a change in the brightness of
• 1:35:27
  Speaker 1: a distant point of light. Yet hidden inside that light
• 1:35:32
  Speaker 1: can be information about an atmosphere surrounding a planet dozens
• 1:35:35
  Speaker 1: or hundreds of light-years away. One of Webb's most powerful
• 1:35:39
  Speaker 1: methods for retrieving that information is known as transit spectroscopy.
• 1:35:44
  Speaker 1: A transit happens when a planet passes in front of
• 1:35:46
  Speaker 1: its star from our point of view. The planet blocks
• 1:35:50
  Speaker 1: a small fraction of the star's light, causing the star
• 1:35:53
  Speaker 1: to appear slightly dimmer for a time. If the planet
• 1:35:56
  Speaker 1: has an atmosphere, something even more interesting happens. A tiny
• 1:36:00
  Speaker 1: amount of starlight passes through that atmosphere before continuing towards
• 1:36:04
  Speaker 1: the telescope. Different atoms and molecules absorb particular wavelengths. So
• 1:36:10
  Speaker 1: although most of the star's light continues onwards, Certain wavelengths
• 1:36:14
  Speaker 1: are blocked slightly more strongly than others. Webb can measure
• 1:36:18
  Speaker 1: those differences. Astronomers compare the spectrum of the star during
• 1:36:23
  Speaker 1: the planet's transit with measurements of the star when the
• 1:36:26
  Speaker 1: planet is not crossing in front of it. The result
• 1:36:30
  Speaker 1: is known as a transmission spectrum. Instead of seeing the
• 1:36:33
  Speaker 1: atmosphere directly, researchers see the tiny imprint it leaves on
• 1:36:37
  Speaker 1: the starlight passing through it. It is a remarkably delicate measurement.
• 1:36:43
  Speaker 1: The planet itself may be hundreds of light-years away. Its
• 1:36:47
  Speaker 1: atmosphere may block only a tiny additional fraction of the
• 1:36:50
  Speaker 1: star's light. Yet the pattern of absorption can reveal which
• 1:36:55
  Speaker 1: molecules are present. One of Webb's most important early demonstrations
• 1:37:00
  Speaker 1: came from the hot gas giant WASP-39b. This planet lies
• 1:37:07
  Speaker 1: roughly 700 light-years from Earth and orbits extremely close to
• 1:37:12
  Speaker 1: its star. It is nothing like our own world. It
• 1:37:15
  Speaker 1: is a large, hot, swollen gas planet with no solid
• 1:37:20
  Speaker 1: surface on which anyone would be planning a quiet picnic.
• 1:37:24
  Speaker 1: But its extended atmosphere makes it an excellent target for spectroscopy.
• 1:37:29
  Speaker 1: Webb detected a clear signature of carbon dioxide in its atmosphere.
• 1:37:34
  Speaker 1: It also revealed information about water vapour, sodium, potassium, carbon
• 1:37:39
  Speaker 1: monoxide and sulphur dioxide. The sulphur dioxide was particularly interesting
• 1:37:44
  Speaker 1: because its presence is linked to photochemistry, where energetic radiation
• 1:37:49
  Speaker 1: from the planet's star drives chemical reactions in the atmosphere.
• 1:37:53
  Speaker 1: The carbon dioxide measurement was especially significant because it demonstrated
• 1:37:57
  Speaker 1: how precisely Webb could identify important molecules in an atmosphere
• 1:38:02
  Speaker 1: beyond the solar system. Finding an exoplanet is one achievement.
• 1:38:07
  Speaker 1: Beginning to determine what its atmosphere contains is another. The
• 1:38:11
  Speaker 1: difference is rather like knowing that a distant house exists,
• 1:38:14
  Speaker 1: and then, without visiting it, beginning to work out something
• 1:38:18
  Speaker 1: about the air inside. Of course, large hot planets such
• 1:38:22
  Speaker 1: as WASP-39b are relatively favourable targets. Their atmospheres are extensive,
• 1:38:28
  Speaker 1: and the signal produced during a transit can be stronger
• 1:38:30
  Speaker 1: than it would be for a small rocky planet. The
• 1:38:33
  Speaker 1: real challenge is applying similar methods to smaller and cooler worlds.
• 1:38:38
  Speaker 1: One particularly intriguing target is K2-18b. It orbits a cool
• 1:38:42
  Speaker 1: red dwarf star roughly 120 light-years away, and is considerably
• 1:38:47
  Speaker 1: larger and more massive than Earth. Web observations have detected
• 1:38:52
  Speaker 1: methane and carbon dioxide in its atmosphere. Those measurements are
• 1:38:56
  Speaker 1: real and important. What they mean for conditions deeper inside
• 1:39:00
  Speaker 1: the planet is much less certain. Some interpretations have suggested
• 1:39:04
  Speaker 1: that K218b might belong to a proposed class of worlds
• 1:39:07
  Speaker 1: containing a deep ocean beneath a hydrogen-rich atmosphere. Other models
• 1:39:12
  Speaker 1: allow very different internal structures. At present, Astronomers cannot simply
• 1:39:17
  Speaker 1: look at its atmospheric spectrum and declare that there is
• 1:39:20
  Speaker 1: an ocean beneath the clouds. Still less can they conclude
• 1:39:24
  Speaker 1: that the planet contains life. This distinction becomes extremely important
• 1:39:29
  Speaker 1: whenever the word biosignature appears. A biosignature is some measurable
• 1:39:34
  Speaker 1: feature that could potentially be associated with biological activity. But
• 1:39:39
  Speaker 1: detecting a particular molecule is not the same thing as
• 1:39:42
  Speaker 1: discovering biology. Chemistry can be surprisingly inventive without any help
• 1:39:47
  Speaker 1: from living organisms. Volcanoes can release gases. Ultraviolet radiation can
• 1:39:53
  Speaker 1: drive chemical reactions. Atmospheres can produce compounds through processes that
• 1:39:58
  Speaker 1: do not occur in exactly the same way on Earth.
• 1:40:01
  Speaker 1: The surface, interior, ocean, clouds, temperature, atmospheric pressure and host
• 1:40:09
  Speaker 1: star can all change how those chemicals should be interpreted.
• 1:40:13
  Speaker 1: Even on Earth, a molecule rarely tells an entire story
• 1:40:17
  Speaker 1: by itself. For a distant planet, the problem becomes considerably harder.
• 1:40:22
  Speaker 1: Astronomers therefore search for combinations of evidence. One gas may
• 1:40:27
  Speaker 1: be interesting. Several gases existing together in a state that
• 1:40:31
  Speaker 1: is difficult to maintain without continual replenishment may be more interesting.
• 1:40:36
  Speaker 1: Knowledge of the star is important as well, because stellar
• 1:40:39
  Speaker 1: radiation can create or destroy molecules in a planet's atmosphere.
• 1:40:44
  Speaker 1: Understanding the planet's temperature and physical structure matters too. The
• 1:40:48
  Speaker 1: goal is not merely to ask which molecules are present,
• 1:40:51
  Speaker 1: but to understand the system that produced them. That is
• 1:40:55
  Speaker 1: one reason Webb's spectra are so valuable. The telescope is
• 1:40:58
  Speaker 1: not simply collecting attractive images of places we cannot visit.
• 1:41:03
  Speaker 1: It is turning light into physical evidence. The same principle
• 1:41:06
  Speaker 1: applies whether the source is an early galaxy or a
• 1:41:09
  Speaker 1: distant planet. A photon reaches the telescope. Its wavelength is measured.
• 1:41:15
  Speaker 1: Millions of such measurements build a spectrum. Patterns emerge, and
• 1:41:21
  Speaker 1: those patterns can tell us about matter located astonishingly far away.
• 1:41:26
  Speaker 1: In one direction, Webb can use red-shifted infrared light to
• 1:41:30
  Speaker 1: study galaxies from the first few hundred million years of
• 1:41:34
  Speaker 1: cosmic history. In another, it can examine starlight filtered through
• 1:41:38
  Speaker 1: a planetary atmosphere. and identify molecules floating above a world
• 1:41:43
  Speaker 1: orbiting another sun. In both cases, almost everything we learn
• 1:41:48
  Speaker 1: arrives encoded in light, and the planet's web studies did
• 1:41:52
  Speaker 1: not simply appear fully formed. They were assembled from gas, dust,
• 1:41:57
  Speaker 1: ice and heavier elements around young stars. To understand where
• 1:42:02
  Speaker 1: those distant worlds came from, we have to look into
• 1:42:05
  Speaker 1: the dusty regions where stars and their planetary systems are
• 1:42:08
  Speaker 1: still being born. the planets. Web studies around distant stars
• 1:42:13
  Speaker 1: did not begin as finished worlds. Long before an atmosphere formed,
• 1:42:17
  Speaker 1: before oceans or clouds were even possible, their material was
• 1:42:22
  Speaker 1: mixed into enormous clouds of gas and dust surrounding young stars.
• 1:42:27
  Speaker 1: To understand how planetary systems begin, astronomers have to look
• 1:42:31
  Speaker 1: into those clouds, and that is exactly where infrared light
• 1:42:35
  Speaker 1: becomes so useful. Some of the most beautiful regions in
• 1:42:39
  Speaker 1: the Milky Way are stellar nurseries, vast areas where new
• 1:42:42
  Speaker 1: stars are still forming. They are made from molecular gas
• 1:42:45
  Speaker 1: mixed with interstellar dust. Much of the gas is hydrogen,
• 1:42:50
  Speaker 1: the most abundant element in the universe, while the dust
• 1:42:54
  Speaker 1: contains tiny solid grains made from materials including silicates, carbon-rich compounds,
• 1:43:00
  Speaker 1: and heavier elements created inside earlier generations of stars. These
• 1:43:06
  Speaker 1: clouds can stretch across many light years. Most of the
• 1:43:09
  Speaker 1: material may remain cold and diffuse for long periods, but
• 1:43:13
  Speaker 1: in some regions gravity begins to win. A slightly denser
• 1:43:17
  Speaker 1: pocket attracts more matter. As additional gas falls inward, the
• 1:43:22
  Speaker 1: region becomes denser still. Gravity strengthens. The process can continue
• 1:43:27
  Speaker 1: until a portion of the cloud begins collapsing under its
• 1:43:29
  Speaker 1: own weight. At the centre, material becomes increasingly compressed. temperature
• 1:43:36
  Speaker 1: and pressure rise, and eventually a young object known as
• 1:43:40
  Speaker 1: a protostar begins to form. A protostar is not yet
• 1:43:43
  Speaker 1: a normal main-sequence star. Nuclear fusion has not necessarily begun
• 1:43:48
  Speaker 1: steadily in its core. Instead, it is still gathering material
• 1:43:52
  Speaker 1: from the surrounding cloud. Gas and dust fall inward, often
• 1:43:56
  Speaker 1: forming a rotating disk around the young star. Much of
• 1:44:00
  Speaker 1: this activity can be hidden from ordinary view. The same
• 1:44:04
  Speaker 1: dust that provides some of the material for new stars
• 1:44:06
  Speaker 1: also blocks visible light. A dense star-forming cloud may therefore
• 1:44:11
  Speaker 1: look dark when observed at optical wavelengths. A visible light
• 1:44:15
  Speaker 1: telescope can reveal glowing surfaces where radiation from nearby stars
• 1:44:20
  Speaker 1: illuminates the gas. It may show bright ridges, towering columns
• 1:44:24
  Speaker 1: and dark silhouettes. But deeper inside, young stars can remain concealed.
• 1:44:30
  Speaker 1: Infrared light changes the view. Longer infrared wavelengths can often
• 1:44:35
  Speaker 1: pass through dust more easily than visible light. That allows
• 1:44:38
  Speaker 1: Webb to look into parts of a stellar nursery that
• 1:44:41
  Speaker 1: would otherwise remain hidden. One of the most dramatic examples
• 1:44:46
  Speaker 1: is the Carina Nebula. This enormous star-forming region lies thousands
• 1:44:52
  Speaker 1: of light-years away in the southern constellation Carina. It contains
• 1:44:56
  Speaker 1: some of the most massive and luminous stars known in
• 1:44:59
  Speaker 1: our region of the Milky Way. When Webb observed part
• 1:45:02
  Speaker 1: of the nebula, It produced an image that became known
• 1:45:05
  Speaker 1: as the Cosmic Cliffs. The name is descriptive rather than literal.
• 1:45:10
  Speaker 1: What appears to be a jagged mountain range is actually
• 1:45:12
  Speaker 1: the edge of an enormous cavity within the nebula. The
• 1:45:16
  Speaker 1: tallest structures in the image extend for light years. They
• 1:45:20
  Speaker 1: are sculpted by radiation and stellar winds from hot, massive
• 1:45:23
  Speaker 1: young stars. Ultraviolet radiation strikes the surrounding cloud, heating and
• 1:45:29
  Speaker 1: eroding its surface. At the same time, the pressure from
• 1:45:33
  Speaker 1: that radiation and from fast-moving stellar material can compress neighbouring gas.
• 1:45:38
  Speaker 1: The result is an environment where destruction and creation occur
• 1:45:42
  Speaker 1: side by side. Some material is being stripped away. Elsewhere,
• 1:45:47
  Speaker 1: dense pockets may be pushed towards further collapse. Webb's infrared
• 1:45:51
  Speaker 1: view revealed young stars that are difficult to see at
• 1:45:54
  Speaker 1: visible wavelengths. It also showed jets and streams of material
• 1:45:59
  Speaker 1: associated with stars still in the process of forming. These
• 1:46:03
  Speaker 1: jets can be launched along the poles of a young
• 1:46:05
  Speaker 1: stellar system as material falls through a rotating disk towards
• 1:46:09
  Speaker 1: the central protostar. The process is not perfectly tidy. Star
• 1:46:14
  Speaker 1: formation rarely is. Some matter falls inward, some is redirected
• 1:46:19
  Speaker 1: and blasted outward, and the surrounding cloud records the consequences.
• 1:46:25
  Speaker 1: Another famous star-forming region transformed by Webb is the Pillars
• 1:46:29
  Speaker 1: of Creation. These enormous columns of gas and dust lie
• 1:46:34
  Speaker 1: inside the Eagle Nebula. They became widely known through images
• 1:46:38
  Speaker 1: from the Hubble Space Telescope, where the towering structures appear
• 1:46:42
  Speaker 1: almost solid against the surrounding glow. Webb looked again in infrared.
• 1:46:48
  Speaker 1: The pillars remained, but the view changed dramatically. More stars
• 1:46:53
  Speaker 1: became visible. Some objects previously hidden inside or behind the
• 1:46:57
  Speaker 1: dusty columns appeared clearly. Young stars and recently formed stellar
• 1:47:02
  Speaker 1: objects stood out against structures that had looked much more
• 1:47:04
  Speaker 1: opaque before. The pillars themselves are being shaped by intense
• 1:47:09
  Speaker 1: ultraviolet radiation from nearby massive stars. Their surfaces are gradually eroded.
• 1:47:15
  Speaker 1: Dense regions deeper inside can resist that erosion for longer,
• 1:47:19
  Speaker 1: and some may continue collapsing into new stars. This makes
• 1:47:23
  Speaker 1: the pillars of creation more than a striking shape. They
• 1:47:27
  Speaker 1: are part of an active physical environment where radiation, gravity, gas,
• 1:47:31
  Speaker 1: dust and newly formed stars are all interacting. Webb can
• 1:47:36
  Speaker 1: also study what happens after a protostar begins gathering material.
• 1:47:40
  Speaker 1: Young stars are often surrounded by disks. These protoplanetary disks
• 1:47:44
  Speaker 1: contain gas and dust orbiting the star. Within them, tiny
• 1:47:49
  Speaker 1: grains can collide. Some collisions cause particles to stick. Small
• 1:47:54
  Speaker 1: structures can become larger aggregates. Over time, and through a
• 1:47:58
  Speaker 1: complicated sequence involving gravity, collisions, migration, and changing disk conditions,
• 1:48:05
  Speaker 1: some material may eventually become planets. This is where the
• 1:48:09
  Speaker 1: connection with distant exoplanets becomes especially clear. A planet whose
• 1:48:14
  Speaker 1: atmosphere web studies today may have begun billions of years earlier,
• 1:48:18
  Speaker 1: inside a disk, much like the ones Webb is observing
• 1:48:21
  Speaker 1: around young stars now. The gases in its atmosphere, the
• 1:48:25
  Speaker 1: materials in its rocks, the ices in its outer system
• 1:48:29
  Speaker 1: and the overall architecture of its orbit all trace back
• 1:48:32
  Speaker 1: in some way to conditions during formation. By observing young
• 1:48:36
  Speaker 1: systems at different stages, Astronomers can begin to reconstruct that process.
• 1:48:42
  Speaker 1: Webb can examine warm dust inside disks. It can study
• 1:48:45
  Speaker 1: molecules in the gas. It can detect heated molecular hydrogen.
• 1:48:50
  Speaker 1: It can observe jets and outflows. Its spectrographs can reveal
• 1:48:55
  Speaker 1: chemical signatures that help researchers understand the composition of material
• 1:48:59
  Speaker 1: surrounding young stars. Different infrared wavelengths probe different temperatures and structures.
• 1:49:06
  Speaker 1: One region may be brighter because dust is warm. Another
• 1:49:10
  Speaker 1: may stand out because a particular molecule is emitting strongly.
• 1:49:13
  Speaker 1: A dark-looking feature may indicate cold, dense material. A bright
• 1:49:19
  Speaker 1: knot may mark a shock where fast-moving gas has collided
• 1:49:22
  Speaker 1: with its surroundings. This is why Webb's spectacular images are
• 1:49:27
  Speaker 1: scientifically important beyond their appearance. The colours and structures are
• 1:49:31
  Speaker 1: not simply decorations. They represent measurements across different infrared wavelengths.
• 1:49:37
  Speaker 1: Those measurements help astronomers investigate temperature, composition, density, star formation,
• 1:49:43
  Speaker 1: and the way radiation interacts with surrounding matter. A photograph
• 1:49:48
  Speaker 1: can therefore become a physical map. It can show where
• 1:49:51
  Speaker 1: stars are forming. It can reveal where radiation is eroding
• 1:49:54
  Speaker 1: a cloud. It can expose hidden protostars. And it can
• 1:49:58
  Speaker 1: identify some of the raw material from which future planets
• 1:50:01
  Speaker 1: may eventually emerge. This broadens the meaning of Webb's mission.
• 1:50:06
  Speaker 1: It was built to study origins at many different scales.
• 1:50:10
  Speaker 1: At one extreme, it observes galaxies from the earliest periods
• 1:50:14
  Speaker 1: of cosmic history. Much closer to home, it studies the
• 1:50:18
  Speaker 1: birth of individual stars. Closer still, it examines the dusty
• 1:50:23
  Speaker 1: disks from which planets can form. The same telescope can
• 1:50:27
  Speaker 1: therefore investigate how galaxies appeared, how stars assembled. how planetary
• 1:50:33
  Speaker 1: systems began. And once Webb started looking at the earliest
• 1:50:37
  Speaker 1: galaxies themselves, another surprise emerged. Some of those ancient systems
• 1:50:43
  Speaker 1: did not look quite as primitive as expected. A number
• 1:50:46
  Speaker 1: appeared brighter, larger or more developed than many astronomers had
• 1:50:50
  Speaker 1: anticipated for such an early period. The telescope built to
• 1:50:54
  Speaker 1: investigate how cosmic structures began was starting to suggest that
• 1:50:59
  Speaker 1: some of them may have grown faster than our earlier
• 1:51:01
  Speaker 1: models had predicted. When Webb began looking seriously into the
• 1:51:06
  Speaker 1: first few hundred million years of cosmic history, astronomers expected surprises.
• 1:51:11
  Speaker 1: They got them rather quickly. Before the telescope launched, computer
• 1:51:17
  Speaker 1: simulations and theoretical models had already produced detailed predictions for
• 1:51:22
  Speaker 1: what the earliest galaxies might look like. The broad expectation
• 1:51:26
  Speaker 1: was that the first system should generally be small, faint, irregular,
• 1:51:30
  Speaker 1: and still in the early stages of assembly. After all,
• 1:51:33
  Speaker 1: there had not been much time. Gravity had only had
• 1:51:36
  Speaker 1: a few hundred million years to gather gas into dark
• 1:51:39
  Speaker 1: matter halos, cool at gas, form stars, build galaxies, and
• 1:51:44
  Speaker 1: begin enriching them with heavier elements. Yet when Webb started
• 1:51:49
  Speaker 1: observing cosmic dawn … Astronomers began finding more bright galaxies
• 1:51:53
  Speaker 1: than many earlier models had predicted. Some appeared surprisingly luminous.
• 1:51:58
  Speaker 1: Others seemed unexpectedly massive. A few even looked as though
• 1:52:03
  Speaker 1: they had developed complicated structures remarkably early. For a while,
• 1:52:07
  Speaker 1: this produced dramatic headlines. Had Webb discovered galaxies that were
• 1:52:12
  Speaker 1: simply too large to exist? Had something gone badly wrong
• 1:52:16
  Speaker 1: with our understanding of the early universe? The reality turned
• 1:52:19
  Speaker 1: out to be more interesting and considerably more subtle. Estimating
• 1:52:24
  Speaker 1: the mass of a galaxy billions of light years away
• 1:52:26
  Speaker 1: is not like placing it on a scale. Astronomers infer
• 1:52:30
  Speaker 1: mass indirectly from the light they receive. That means building
• 1:52:34
  Speaker 1: models of the stars inside the galaxy and asking what
• 1:52:38
  Speaker 1: combination of stellar ages, temperatures, chemical compositions and total numbers
• 1:52:44
  Speaker 1: could produce the observed spectrum. Dust complicates the picture because
• 1:52:48
  Speaker 1: it can absorb some wavelengths and re-emit energy at others.
• 1:52:52
  Speaker 1: The history of star formation matters as well. A galaxy
• 1:52:56
  Speaker 1: that recently experienced an intense burst of new stars can
• 1:52:59
  Speaker 1: produce enormous amounts of light without necessarily containing as much
• 1:53:03
  Speaker 1: stellar mass as an older galaxy of similar brightness. Distance
• 1:53:08
  Speaker 1: must also be known accurately. And then there are black holes.
• 1:53:13
  Speaker 1: A supermassive black hole consuming surrounding material can power an
• 1:53:17
  Speaker 1: active galactic nucleus. Gas spiralling towards the black hole becomes
• 1:53:21
  Speaker 1: extremely hot and can produce extraordinary amounts of radiation. If
• 1:53:27
  Speaker 1: part of that light is mistakenly attributed to stars, astronomers
• 1:53:31
  Speaker 1: can overestimate the stellar mass of the galaxy. This is
• 1:53:35
  Speaker 1: one reason some of the earliest claims changed as better
• 1:53:38
  Speaker 1: observations became available. Spectroscopy allowed astronomers to separate different sources
• 1:53:43
  Speaker 1: of light more carefully. Improved models provided better estimates of
• 1:53:48
  Speaker 1: stellar populations. Some objects that initially appeared impossibly massive became
• 1:53:53
  Speaker 1: less extreme. The early universe had not suddenly become incompatible
• 1:53:57
  Speaker 1: with everything astronomers thought they understood. But the puzzle did
• 1:54:01
  Speaker 1: not disappear, even after some of the most dramatic mass
• 1:54:05
  Speaker 1: estimates were revised. Webb continued finding large numbers of bright
• 1:54:10
  Speaker 1: galaxies surprisingly early. The question shifted. Instead of asking how
• 1:54:16
  Speaker 1: impossible galaxies had formed, astronomers began asking whether the earliest
• 1:54:20
  Speaker 1: galaxies were simply much more efficient at turning gas into
• 1:54:23
  Speaker 1: stars than many previous models assumed. The early universe was
• 1:54:27
  Speaker 1: denser than the universe today. Galaxies contained enormous supplies of gas.
• 1:54:33
  Speaker 1: Matter was gathering rapidly into growing dark matter halos. Under
• 1:54:37
  Speaker 1: those conditions, star formation may have proceeded differently from the
• 1:54:42
  Speaker 1: way it typically occurs in nearby galaxies. Gas might have
• 1:54:45
  Speaker 1: cooled and collapsed efficiently. Bursts of star formation may have
• 1:54:49
  Speaker 1: been extremely intense. Feedback from young stars, supernovae and black
• 1:54:55
  Speaker 1: holes may also have behaved differently within these compact early systems.
• 1:55:00
  Speaker 1: Webb has also complicated the old mental picture of the
• 1:55:02
  Speaker 1: first galaxies as little more than shapeless blobs. Many certainly
• 1:55:07
  Speaker 1: are irregular. Some are clumpy, with several bright regions of
• 1:55:11
  Speaker 1: star formation scattered through them. Others appear elongated. Some look flattened,
• 1:55:18
  Speaker 1: suggesting disk-like structures may have emerged surprisingly early. And as
• 1:55:23
  Speaker 1: Webb observes slightly later periods within the first billion or
• 1:55:27
  Speaker 1: two billion years, increasingly organised galaxies begin to appear. That
• 1:55:32
  Speaker 1: does not mean fully mature modern spirals were everywhere immediately
• 1:55:36
  Speaker 1: after the Big Bang. But it does suggest that galaxies
• 1:55:39
  Speaker 1: could develop recognisable structure faster than simple pictures of gradual
• 1:55:44
  Speaker 1: cosmic growth might imply. Sometimes the surprises appear not in
• 1:55:49
  Speaker 1: a galaxy's shape, but in its spectrum. One striking example
• 1:55:53
  Speaker 1: is the galaxy known as Jades G.S.Z. 13.1. Webb sees
• 1:55:58
  Speaker 1: this galaxy as it existed roughly 330 million years after
• 1:56:03
  Speaker 1: the Big Bang. Its light contains unexpectedly strong emission from hydrogen,
• 1:56:08
  Speaker 1: known as Lyman-alpha emission. That is surprising because the early
• 1:56:12
  Speaker 1: universe at this period still contained large amounts of neutral
• 1:56:15
  Speaker 1: hydrogen between galaxies. Neutral hydrogen is very effective at absorbing
• 1:56:20
  Speaker 1: Lyman-alpha radiation. Astronomers might therefore expect much of this particular
• 1:56:25
  Speaker 1: light to disappear before travelling very far. yet Webb detected it.
• 1:56:30
  Speaker 1: Something about the environment surrounding the galaxy apparently allowed that
• 1:56:34
  Speaker 1: radiation to escape. Perhaps the galaxy, or nearby sources, had
• 1:56:39
  Speaker 1: already ionised a bubble in the surrounding hydrogen. Perhaps the
• 1:56:43
  Speaker 1: structure or motion of the gas helped the photons find
• 1:56:45
  Speaker 1: a path outward. Whatever the complete explanation turns out to be,
• 1:56:50
  Speaker 1: the observation gives astronomers information about the period known as
• 1:56:54
  Speaker 1: cosmic reionisation. when energetic radiation from early stars, galaxies and
• 1:56:59
  Speaker 1: black holes gradually transformed much of the neutral hydrogen filling
• 1:57:04
  Speaker 1: intergalactic space. Then there are the little red dots. They
• 1:57:09
  Speaker 1: are among the stranger populations revealed by Webb. As the
• 1:57:12
  Speaker 1: name suggests, many appear rather unremarkable at first. They are compact,
• 1:57:17
  Speaker 1: they are red, and on an image some really do
• 1:57:20
  Speaker 1: look like little dots, but they seem to become abundant
• 1:57:23
  Speaker 1: during an early period of cosmic history. then become much
• 1:57:27
  Speaker 1: less common as the universe ages. What exactly they are
• 1:57:31
  Speaker 1: remains an active question. Evidence from many of them points
• 1:57:35
  Speaker 1: towards rapidly growing supermassive black holes surrounded by dense material.
• 1:57:41
  Speaker 1: In some cases, much of the observed light may come
• 1:57:44
  Speaker 1: from hot gas falling towards a black hole, rather than
• 1:57:47
  Speaker 1: from ordinary stars. Other interpretations involve unusual stellar populations or
• 1:57:53
  Speaker 1: combinations of stars and black hole activity. Understanding that distinction
• 1:57:59
  Speaker 1: matters enormously. If the brightness is mostly coming from stars,
• 1:58:03
  Speaker 1: the objects may contain astonishing amounts of stellar mass. If
• 1:58:08
  Speaker 1: a black hole supplies much of the light, the host
• 1:58:11
  Speaker 1: galaxy may be considerably smaller. Either answer teaches us something important.
• 1:58:17
  Speaker 1: One changes our understanding of how rapidly galaxies assembled. The
• 1:58:21
  Speaker 1: other raises an equally difficult question about how enormous black
• 1:58:25
  Speaker 1: holes managed to appear so early. What Webb has not
• 1:58:29
  Speaker 1: done is casually overturn the entire standard picture of cosmology.
• 1:58:34
  Speaker 1: The universe still appears to be expanding. Dark matter remains
• 1:58:38
  Speaker 1: central to models of cosmic structure. Dark energy remains part
• 1:58:43
  Speaker 1: of the explanation for accelerated expansion at much later times.
• 1:58:48
  Speaker 1: The broad cosmological framework continues to describe an enormous range
• 1:58:52
  Speaker 1: of observations successfully. Many of Webb's most interesting tensions exist
• 1:58:57
  Speaker 1: instead within the astrophysics happening inside that framework. How quickly
• 1:59:01
  Speaker 1: could gas cool? How efficiently could early galaxies turn that
• 1:59:05
  Speaker 1: gas into stars? How rapidly could black holes grow? How
• 1:59:09
  Speaker 1: soon could disks and other organised structures emerge? How strongly
• 1:59:14
  Speaker 1: did young stars and black holes affect the gas surrounding them?
• 1:59:17
  Speaker 1: These are difficult questions. But difficult questions are exactly what
• 1:59:21
  Speaker 1: a more powerful telescope ought to produce. Science does not
• 1:59:24
  Speaker 1: work by building a model and then defending it from
• 1:59:27
  Speaker 1: inconvenient observations. A model earns its value by confronting those observations.
• 1:59:33
  Speaker 1: If new measurements reveal that an assumption was too simple,
• 1:59:36
  Speaker 1: the model changes. If better spectra show that a galaxy
• 1:59:40
  Speaker 1: is less massive than first thought, the estimate changes. If
• 1:59:44
  Speaker 1: unexpectedly bright galaxies keep appearing, theories of star formation have
• 1:59:48
  Speaker 1: to explain them. That is not science malfunctioning. It is
• 1:59:52
  Speaker 1: science doing what it is supposed to do. And perhaps
• 1:59:56
  Speaker 1: that is one of Webb's most important achievements. The telescope
• 1:59:59
  Speaker 1: was never valuable because it might confirm everything astronomers already believed.
• 2:00:04
  Speaker 1: It was valuable because it could finally observe regions of
• 2:00:07
  Speaker 1: cosmic history where many of those beliefs had barely been tested.
• 2:00:11
  Speaker 1: The first galaxies are no longer almost entirely theoretical objects
• 2:00:15
  Speaker 1: hidden beyond the reach of our instruments. They are becoming
• 2:00:18
  Speaker 1: measurable systems. Their spectra can be examined. their shapes can
• 2:00:22
  Speaker 1: be studied, their black holes can begin to be identified,
• 2:00:26
  Speaker 1: and every improvement in the observations reveals another layer of complexity.
• 2:00:31
  Speaker 1: Webb has already shown that the young universe was busier, brighter,
• 2:00:36
  Speaker 1: and in some ways more developed than the simplest expectation suggested.
• 2:00:41
  Speaker 1: But the telescope is still early in its scientific life.
• 2:00:45
  Speaker 1: The most important surprise may not be one we already
• 2:00:47
  Speaker 1: know how to describe, It may still be travelling quietly
• 2:00:51
  Speaker 1: towards Webb's mirror, hidden inside photons the telescope has not
• 2:00:55
  Speaker 1: yet collected. For all that Webb has already revealed, its
• 2:00:59
  Speaker 1: final scientific legacy is still impossible to know. The telescope
• 2:01:04
  Speaker 1: remains active, continuing to collect infrared light from distant galaxies,
• 2:01:09
  Speaker 1: newborn stars, planetary systems and worlds beyond the solar system.
• 2:01:15
  Speaker 1: Some questions it was designed to answer have become clearer.
• 2:01:18
  Speaker 1: Others have become more complicated. And somewhere within observations that
• 2:01:23
  Speaker 1: have not yet been made may be the discovery for
• 2:01:25
  Speaker 1: which Webb is eventually remembered most. One of its oldest
• 2:01:29
  Speaker 1: goals takes us back almost as far as stars can
• 2:01:32
  Speaker 1: take us. Astronomers would like to find evidence of the
• 2:01:35
  Speaker 1: first generation of stars ever formed. These hypothetical primordial stars
• 2:01:40
  Speaker 1: are usually known as Population 3 stars. The name is
• 2:01:45
  Speaker 1: slightly confusing because Population 3 actually refers to the earliest
• 2:01:49
  Speaker 1: stellar population. The numbering arose historically as astronomers classified different
• 2:01:54
  Speaker 1: groups of stars before the first generation itself had ever
• 2:01:57
  Speaker 1: been observed. Unlike the Sun, Population 3 stars would have
• 2:02:02
  Speaker 1: formed from almost pristine material left by the early universe.
• 2:02:07
  Speaker 1: After the Big Bang, ordinary matter consisted overwhelmingly of hydrogen
• 2:02:11
  Speaker 1: and helium. with tiny quantities of lithium. Carbon had not
• 2:02:16
  Speaker 1: yet been manufactured in stars. Neither had oxygen, silicon, iron,
• 2:02:21
  Speaker 1: or the many other heavier elements that now exist throughout galaxies.
• 2:02:26
  Speaker 1: Astronomers collectively refer to elements heavier than helium as metals,
• 2:02:30
  Speaker 1: even though this includes things such as oxygen that nobody
• 2:02:34
  Speaker 1: would normally call a metal in everyday conversation. Population three
• 2:02:38
  Speaker 1: stars would therefore have contained almost no metals at all.
• 2:02:42
  Speaker 1: They may also have been very different from stars forming today.
• 2:02:46
  Speaker 1: Without heavier elements and dust to help gas cool efficiently,
• 2:02:50
  Speaker 1: primordial clouds behaved differently as they collapsed. Many theoretical models
• 2:02:55
  Speaker 1: suggest that at least some of the first stars may
• 2:02:58
  Speaker 1: have become unusually massive, perhaps many tens or even hundreds
• 2:03:02
  Speaker 1: of times the mass of the Sun. If so, they
• 2:03:06
  Speaker 1: would have burned through their nuclear fuel extremely quickly and
• 2:03:09
  Speaker 1: disappeared long ago. Finding one directly is therefore extraordinarily difficult.
• 2:03:15
  Speaker 1: The first stars existed at enormous distances. Their strongest radiation
• 2:03:20
  Speaker 1: was often produced at ultraviolet wavelengths, and over more than
• 2:03:25
  Speaker 1: 13 billion years of cosmic expansion, much of that light
• 2:03:28
  Speaker 1: has been stretched toward visible and infrared wavelengths. It has
• 2:03:33
  Speaker 1: also become incredibly faint. An individual primordial star would therefore
• 2:03:38
  Speaker 1: have to compete with distant cosmic expansion. and the simple
• 2:03:42
  Speaker 1: fact that a single star produces far less light than
• 2:03:46
  Speaker 1: an entire galaxy. Webb may still have ways of reaching them.
• 2:03:51
  Speaker 1: One possibility is gravitational lensing. A massive galaxy cluster between
• 2:03:56
  Speaker 1: Earth and an extremely distant star can bend and magnify
• 2:04:01
  Speaker 1: the star's light, occasionally boosting something normally far too faint
• 2:04:05
  Speaker 1: into the range of detection. Astronomers can also search for
• 2:04:10
  Speaker 1: entire young galaxies, whose stellar populations appear exceptionally poor in
• 2:04:15
  Speaker 1: heavier elements. Their spectra might contain chemical patterns, suggesting that
• 2:04:20
  Speaker 1: much of their light comes from nearly pristine stars. Another
• 2:04:24
  Speaker 1: approach is to search for the aftermath. The first stars
• 2:04:28
  Speaker 1: changed the universe around them. They produced intense ultraviolet radiation.
• 2:04:34
  Speaker 1: They manufactured the first substantial quantities of heavier elements inside
• 2:04:38
  Speaker 1: their cores. When some died as powerful supernovae, they scattered
• 2:04:43
  Speaker 1: those elements into surrounding space. Others may have collapsed into
• 2:04:47
  Speaker 1: black holes that later became seeds for much larger black holes.
• 2:04:51
  Speaker 1: Even if Webb never produces a clear portrait of one
• 2:04:54
  Speaker 1: isolated Population 3 star, it may still identify the fingerprints
• 2:04:59
  Speaker 1: that the first stars left behind. There is another kind
• 2:05:02
  Speaker 1: of search happening much closer to us. Webb continues studying
• 2:05:07
  Speaker 1: the atmospheres of exoplanets. Its infrared spectrographs can detect molecules
• 2:05:12
  Speaker 1: by measuring the characteristic wavelengths they absorb as starlight passes
• 2:05:17
  Speaker 1: through an atmosphere. For some planets, astronomers hope eventually to
• 2:05:21
  Speaker 1: identify combinations of gases that could be investigated as possible biosignatures.
• 2:05:27
  Speaker 1: The wording matters. A possible biosignature is not a discovery
• 2:05:32
  Speaker 1: of life. Even an apparently exciting atmospheric molecule can have
• 2:05:36
  Speaker 1: several possible origins. Methane can be produced biologically, but it
• 2:05:41
  Speaker 1: can also emerge from geological processes. Oxygen can be strongly
• 2:05:46
  Speaker 1: associated with life under some circumstances, yet there are non-biological
• 2:05:50
  Speaker 1: mechanisms capable of producing it as well. The chemistry of
• 2:05:54
  Speaker 1: an alien planet cannot simply be interpreted by asking what
• 2:05:58
  Speaker 1: the same molecule usually means on Earth. Astronomers would need context.
• 2:06:03
  Speaker 1: They would need to understand the host star and the
• 2:06:05
  Speaker 1: radiation it sends towards the planet. They would need information
• 2:06:09
  Speaker 1: about atmospheric temperature and pressure. They would need to investigate
• 2:06:12
  Speaker 1: possible geological and photochemical processes. Repeated observations would be essential. Ideally,
• 2:06:19
  Speaker 1: several independent clues would point towards the same interpretation. Even then,
• 2:06:24
  Speaker 1: extraordinary care would be needed before anyone could reasonably claim
• 2:06:27
  Speaker 1: evidence of biology. Webb may therefore contribute to a discovery
• 2:06:31
  Speaker 1: of life without necessarily being the observatory that settles the
• 2:06:34
  Speaker 1: question alone. That possibility is only one small part of
• 2:06:38
  Speaker 1: its remaining work. The telescope will continue examining the earliest galaxies,
• 2:06:44
  Speaker 1: helping astronomers determine how rapidly they formed stars and accumulated mass.
• 2:06:49
  Speaker 1: It can investigate the growth of early black holes and
• 2:06:52
  Speaker 1: perhaps clarify how objects containing millions or billions of solar
• 2:06:56
  Speaker 1: masses appeared so quickly after the Big Bang. It can
• 2:06:59
  Speaker 1: study cosmic reanisation. when radiation from early luminous objects transformed
• 2:07:05
  Speaker 1: much of the neutral hydrogen between galaxies. Closer to home,
• 2:07:10
  Speaker 1: Webb can continue observing stellar nurseries, protoplanetary disks, brown dwarfs, planets, moons, asteroids,
• 2:07:19
  Speaker 1: comets and distant objects in the outer solar system. The
• 2:07:24
  Speaker 1: mission was designed to study origins, but that word covers
• 2:07:27
  Speaker 1: an enormous range of scales, the origins of galaxies, the
• 2:07:32
  Speaker 1: origins of stars, the origins of planets, and perhaps, indirectly,
• 2:07:38
  Speaker 1: clues concerning the conditions in which life can begin. How
• 2:07:42
  Speaker 1: long Webb will continue doing this is another interesting question.
• 2:07:46
  Speaker 1: The observatory was designed around a minimum scientific mission of
• 2:07:49
  Speaker 1: five years, with a goal of at least ten. But
• 2:07:53
  Speaker 1: its launch aboard the Ariane 5 rocket was exceptionally precise,
• 2:07:57
  Speaker 1: because Webb entered its outbound trajectory so accurate it needed
• 2:08:01
  Speaker 1: less propellant than expected for some of its early corrections.
• 2:08:05
  Speaker 1: That preserved fuel used for station keeping and momentum management.
• 2:08:09
  Speaker 1: As a result, the observatory has enough propellant to support
• 2:08:12
  Speaker 1: more than 20 years of scientific operations. That does not
• 2:08:16
  Speaker 1: mean Webb is guaranteed to work perfectly for more than
• 2:08:18
  Speaker 1: two decades. Fuel is only one limitation. Detectors age, electronics
• 2:08:24
  Speaker 1: can degrade, mechanical systems can develop problems. The telescope is
• 2:08:29
  Speaker 1: exposed to the space environment, including impacts from tiny meteoroids
• 2:08:34
  Speaker 1: travelling at enormous speeds. Most such impacts are extremely small,
• 2:08:39
  Speaker 1: but over many years they can gradually affect mirror segments
• 2:08:42
  Speaker 1: and other exposed surfaces. Eventually, some hardware failure may become
• 2:08:47
  Speaker 1: more important than the amount of propellant remaining. Still, the
• 2:08:51
  Speaker 1: possibility of such a long scientific life creates a curious
• 2:08:54
  Speaker 1: relationship between Webb's future and the universe's past. The longer
• 2:08:59
  Speaker 1: the telescope survives, the more ancient light it can collect.
• 2:09:03
  Speaker 1: Longer observing programs can reach fainter objects. Improved analysis can
• 2:09:08
  Speaker 1: extract information that earlier techniques missed. Astronomers can return to
• 2:09:12
  Speaker 1: intriguing targets with better questions. New discoveries can reveal where
• 2:09:17
  Speaker 1: the telescope should look next. A decade from now, researchers
• 2:09:21
  Speaker 1: may be using Webb in ways that were barely imagined
• 2:09:24
  Speaker 1: when it launched. That has happened repeatedly in astronomy. Powerful
• 2:09:28
  Speaker 1: instruments rarely produce only the discoveries they were specifically designed
• 2:09:32
  Speaker 1: to make. Once a new part of the universe becomes observable,
• 2:09:37
  Speaker 1: unexpected things tend to appear inside it. Somewhere in Webb's future,
• 2:09:42
  Speaker 1: data may be the unmistakable chemical imprint of an extraordinarily
• 2:09:46
  Speaker 1: primitive stellar population. There may be an exoplanet atmosphere unlike
• 2:09:51
  Speaker 1: any yet measured. There may be a galaxy from an
• 2:09:54
  Speaker 1: even earlier period than those currently confirmed. There may be
• 2:09:58
  Speaker 1: a black hole whose existence forces another revision of how
• 2:10:02
  Speaker 1: quickly these objects can grow. Or there may be something stranger,
• 2:10:07
  Speaker 1: an object or phenomenon that does not yet have a
• 2:10:10
  Speaker 1: convenient place in our existing categories. That may be the
• 2:10:14
  Speaker 1: most exciting possibility of all. Webb was built to answer
• 2:10:17
  Speaker 1: questions that astronomers already knew how to ask. Its greatest
• 2:10:22
  Speaker 1: discovery may come from finding something that nobody thought to
• 2:10:25
  Speaker 1: ask about. Every time we look into the night sky,
• 2:10:30
  Speaker 1: we are looking into the past. The moon appears to
• 2:10:33
  Speaker 1: us as it was a little over one second ago.
• 2:10:36
  Speaker 1: The sun appears as it was a little more than
• 2:10:38
  Speaker 1: eight minutes ago. Nearby stars show us light that may
• 2:10:42
  Speaker 1: have been travelling for years or centuries. and the faintest
• 2:10:45
  Speaker 1: galaxies visible to the James Webb Space Telescope can send
• 2:10:49
  Speaker 1: us photons that began their journey more than 13 billion
• 2:10:53
  Speaker 1: years ago. Astronomy has always worked this way. Light takes
• 2:10:58
  Speaker 1: time to travel. Distance, therefore, becomes a way of looking backward.
• 2:11:03
  Speaker 1: The farther away an object is, the older the light
• 2:11:05
  Speaker 1: we receive from it tends to be. Webb simply pushes
• 2:11:08
  Speaker 1: that basic fact to an extraordinary extreme. Its ability to
• 2:11:13
  Speaker 1: reach so far into cosmic history depends on several things
• 2:11:16
  Speaker 1: working together. The first is the finite speed of light.
• 2:11:20
  Speaker 1: The second is cosmological redshift. As the universe expands, the
• 2:11:25
  Speaker 1: wavelengths of ancient light are stretched. Radiation that began its
• 2:11:29
  Speaker 1: journey in ultraviolet or visible wavelengths can arrive at Earth
• 2:11:33
  Speaker 1: shifted into the infrared. That is why a telescope designed
• 2:11:37
  Speaker 1: to study the earliest galaxies must be extremely sensitive to
• 2:11:40
  Speaker 1: infrared light. Webb was built around that requirement. Its primary
• 2:11:44
  Speaker 1: mirror is roughly six and a half metres across. It
• 2:11:48
  Speaker 1: is made from 18 hexagonal segments of beryllium. Each segment
• 2:11:52
  Speaker 1: carries an extremely thin coating of gold, chosen because gold
• 2:11:57
  Speaker 1: reflects infrared radiation particularly well. The mirror is large enough
• 2:12:02
  Speaker 1: to gather faint photons arriving from objects so distant that,
• 2:12:05
  Speaker 1: in many cases, only a tiny trickle of light reaches us.
• 2:12:10
  Speaker 1: But a powerful infrared telescope cannot simply be large. It
• 2:12:14
  Speaker 1: must also be cold. Anything warm produces infrared radiation of
• 2:12:19
  Speaker 1: its own. If Webb were allowed to glow strongly in
• 2:12:22
  Speaker 1: the same wavelengths it was trying to observe, its own
• 2:12:25
  Speaker 1: heat would interfere with the signals arriving from space. So
• 2:12:29
  Speaker 1: beneath the mirror sits the enormous five-layer sunshield. It is
• 2:12:33
  Speaker 1: roughly the size of a tennis court. Its purpose is
• 2:12:36
  Speaker 1: to keep sunlight and thermal radiation from the Sun, Earth
• 2:12:40
  Speaker 1: moon and warm spacecraft systems away from the cold side
• 2:12:44
  Speaker 1: of the observatory. Behind that shield, the telescope and its
• 2:12:48
  Speaker 1: instruments can operate at temperatures hundreds of degrees below freezing.
• 2:12:52
  Speaker 1: Some parts cool naturally through passive radiation into space. The
• 2:12:56
  Speaker 1: mid-infrared instrument must become colder still, reaching only a few
• 2:13:00
  Speaker 1: degrees above absolute zero with help from a dedicated cryo-cooler,
• 2:13:04
  Speaker 1: and all of this takes place near the second Lagrange point,
• 2:13:07
  Speaker 1: roughly one and a half million kilometres from Earth. There,
• 2:13:11
  Speaker 1: Webb can keep the Sun, Earth and Moon on the
• 2:13:14
  Speaker 1: same general side of the spacecraft. Its shield remains between
• 2:13:17
  Speaker 1: those warm sources and the telescope. The entire geometry of
• 2:13:21
  Speaker 1: the mission exists to protect that cold infrared view. Before Webb,
• 2:13:26
  Speaker 1: the Hubble Space Telescope had already shown how powerful deep
• 2:13:29
  Speaker 1: observations could become. Hubble stared into apparently empty patches of
• 2:13:33
  Speaker 1: sky and revealed thousands of galaxies. Its deep fields transformed
• 2:13:38
  Speaker 1: our understanding of the distant universe. But Hubble also helped
• 2:13:42
  Speaker 1: expose the next problem. The farther astronomers looked, the more
• 2:13:46
  Speaker 1: ancient light had been stretched toward wavelengths beyond the region
• 2:13:49
  Speaker 1: where Hubble worked most effectively. So the next telescope had
• 2:13:53
  Speaker 1: to go farther into the infrared. It had to collect
• 2:13:56
  Speaker 1: more light, and it had to remain much colder. Meeting
• 2:13:59
  Speaker 1: those requirements produced one of the strangest-looking scientific machines ever built.
• 2:14:03
  Speaker 1: 18 golden mirror segments, a sunshield large enough to cover
• 2:14:08
  Speaker 1: a tennis court, Instruments operating at cryogenic temperatures. A structure
• 2:14:13
  Speaker 1: that could never have fitted inside a rocket if launched
• 2:14:15
  Speaker 1: at full size. Webb therefore had to leave Earth folded.
• 2:14:19
  Speaker 1: The mirror wings folded inward. The sunshield was packed away.
• 2:14:24
  Speaker 1: Support structures were collapsed. And after launch, the telescope had
• 2:14:28
  Speaker 1: to transform itself in space. That design took decades to realise.
• 2:14:34
  Speaker 1: Serious planning began in the 1990s. The mission changed shape repeatedly.
• 2:14:39
  Speaker 1: Costs increased, launch dates slipped, technical problems had to be solved.
• 2:14:45
  Speaker 1: At one point, the programme came close to cancellation. Testing
• 2:14:50
  Speaker 1: became longer and more complicated because almost every major feature
• 2:14:53
  Speaker 1: had to work in an environment that could never be
• 2:14:56
  Speaker 1: reproduced perfectly on Earth. Thousands of scientists, engineers, technicians, managers, programmers,
• 2:15:03
  Speaker 1: researchers and specialists across several countries contributed to the observatory.
• 2:15:09
  Speaker 1: By Christmas Day in 2021, the result of roughly three
• 2:15:13
  Speaker 1: decades of work was finally sitting on top of an
• 2:15:16
  Speaker 1: Ariane 5 rocket in French Guiana. And even then, the
• 2:15:20
  Speaker 1: difficult part was not over. Launch was only the beginning.
• 2:15:25
  Speaker 1: Webb travelled outward while unfolding itself. Release mechanisms activated. Booms extended.
• 2:15:32
  Speaker 1: The sunshield opened and tensioned. The secondary mirror moved into position.
• 2:15:37
  Speaker 1: The primary mirror wings unfolded. Then the 18 mirror segments
• 2:15:42
  Speaker 1: had to be aligned until they behaved like one enormous
• 2:15:45
  Speaker 1: optical surface. All of this happened while the observatory was
• 2:15:49
  Speaker 1: moving farther from Earth. There was no realistic expectation that
• 2:15:53
  Speaker 1: astronauts would ever arrive to repair it. Webb had been
• 2:15:56
  Speaker 1: designed to work alone. And it did. The telescope reached
• 2:16:00
  Speaker 1: its operating region. Its instruments cooled. Its mirrors aligned. And
• 2:16:06
  Speaker 1: then the science began. Already, Webb has observed galaxies from
• 2:16:11
  Speaker 1: only a few hundred million years after the Big Bang.
• 2:16:14
  Speaker 1: It has found early systems that appear brighter, more massive,
• 2:16:18
  Speaker 1: or more structured than some earlier models predicted. It has
• 2:16:22
  Speaker 1: shown that the young universe was active, complicated, and capable
• 2:16:27
  Speaker 1: of assembling luminous structures remarkably quickly. Those surprises do not
• 2:16:33
  Speaker 1: mean science has failed. They mean the telescope is doing
• 2:16:36
  Speaker 1: exactly what it was built to do. Scientific models are
• 2:16:40
  Speaker 1: not valuable because they remain untouched forever. They are valuable
• 2:16:44
  Speaker 1: because they can be tested. When observations reveal that an
• 2:16:48
  Speaker 1: assumption was too simple, the model improves. When new data
• 2:16:53
  Speaker 1: show that galaxies form stars more efficiently than expected, astronomers
• 2:16:58
  Speaker 1: revise their understanding. When early black holes appear larger or
• 2:17:02
  Speaker 1: more common than anticipated, theories of black hole growth have
• 2:17:05
  Speaker 1: to work harder. That process is not a weakness. It
• 2:17:09
  Speaker 1: is how knowledge becomes more precise. Webb has also looked
• 2:17:13
  Speaker 1: much closer to home. It has studied the atmospheres of
• 2:17:16
  Speaker 1: planets around other stars. It has detected molecules including carbon dioxide, methane,
• 2:17:21
  Speaker 1: water vapour and sulphur dioxide in distant planetary systems. It
• 2:17:26
  Speaker 1: has examined dusty stellar nurseries where new stars are forming.
• 2:17:30
  Speaker 1: It has looked into protoplanetary disks where future planets may
• 2:17:34
  Speaker 1: be assembling. It has studied objects within our own solar system.
• 2:17:38
  Speaker 1: The telescope designed to investigate the earliest galaxies has become
• 2:17:43
  Speaker 1: a machine for studying origins at almost every scale. And
• 2:17:47
  Speaker 1: there is still much left to find. Webb may eventually
• 2:17:50
  Speaker 1: reveal clearer evidence of the first generation of stars. It
• 2:17:55
  Speaker 1: may help astronomers understand exactly how cosmic dawn unfolded. It
• 2:17:59
  Speaker 1: may measure exoplanet atmospheres with enough precision to identify combinations
• 2:18:04
  Speaker 1: of molecules that deserve serious investigation as possible biosignatures. It
• 2:18:10
  Speaker 1: may clarify how quickly the first black holes grew, or
• 2:18:13
  Speaker 1: it may find something nobody has yet thought to search for.
• 2:18:17
  Speaker 1: That possibility is always present with a new observatory. The
• 2:18:20
  Speaker 1: most important discovery may not be the one written into
• 2:18:23
  Speaker 1: the original mission proposal. It may be the thing that
• 2:18:26
  Speaker 1: appears unexpectedly in the data and forces everyone to ask
• 2:18:31
  Speaker 1: a new question. There is something almost difficult to grasp
• 2:18:35
  Speaker 1: about the age of the light Webb receives. Earth is
• 2:18:38
  Speaker 1: roughly four and a half billion years old. Some of
• 2:18:42
  Speaker 1: the photons entering Webb's mirror have been travelling for more
• 2:18:44
  Speaker 1: than 13 billion years. They have crossed the universe for
• 2:18:48
  Speaker 1: almost three times as long as our planet has existed.
• 2:18:52
  Speaker 1: They were already on their way before the sun formed,
• 2:18:55
  Speaker 1: before Earth existed, before there were oceans, continents, trees, animals,
• 2:19:01
  Speaker 1: or anyone capable of wondering where the light had come from.
• 2:19:05
  Speaker 1: And now some of those photons end their journey by
• 2:19:07
  Speaker 1: striking a thin layer of gold on a mirror built
• 2:19:10
  Speaker 1: by humans. Webb does not literally see the beginning of time.
• 2:19:14
  Speaker 1: It cannot photograph the Big Bang itself. But it has
• 2:19:18
  Speaker 1: carried our vision farther toward the first luminous chapters of
• 2:19:21
  Speaker 1: cosmic history than previous observatories could routinely reach. It is
• 2:19:26
  Speaker 1: an eye built to read ancient light. An eye assembled
• 2:19:30
  Speaker 1: by thousands of people over roughly three decades. an eye
• 2:19:34
  Speaker 1: travelling around the sun with Earth, far beyond the moon,
• 2:19:38
  Speaker 1: keeping its mirror hidden behind a vast shield, and there
• 2:19:41
  Speaker 1: it remains, quietly collecting photons, one after another, some nearby,
• 2:19:48
  Speaker 1: some ancient, some carrying information from planets, others from newborn stars,
• 2:19:54
  Speaker 1: and some from galaxies shining when the universe itself was
• 2:19:57
  Speaker 1: still young. The history was always there, It has been
• 2:20:00
  Speaker 1: travelling towards us across the darkness for billions of years,
• 2:20:04
  Speaker 1: written into the light. All humanity had to do was
• 2:20:07
  Speaker 1: build an eye large enough, cold enough and sensitive enough
• 2:20:10
  Speaker 1: to begin reading it.