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THE UNIVERSE HAS NO EDGE...SO HOW BIG IS IT_ · Boring Science

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  Speaker 1: Hello, and welcome to Boring Science to Sleep, a quiet
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  Speaker 1: place where science becomes slow, soft, and easy to drift through. Tonight,
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  Speaker 1: you're going to gently explore the cosmic scale, the enormous
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  Speaker 1: size of the universe, the galaxies scattered through its darkness,
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  Speaker 1: and the strange distances that separate one island of light
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  Speaker 1: from another, not to learn everything, but simply to notice
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  Speaker 1: it slowly, calmly, one small thought at a time. But
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  Speaker 1: before you settle in, if you truly enjoy these calm
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  Speaker 1: journeys through interesting facts about science, you're welcome to like
• 0:37
  Speaker 1: this video and subscribe, only if it feels right for you.
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  Speaker 1: And when you're ready, let me know in the comments
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  Speaker 1: where you're listening from, and what time it is right now.
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  Speaker 1: It's always a quiet joy to see how many places
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  Speaker 1: and moments gather here together. Now, dim the lights, maybe
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  Speaker 1: let a fan hum softly in the background. and allow
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  Speaker 1: your body to become a little heavier against the surface
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  Speaker 1: beneath you. There is nothing to do. You are safe.
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  Speaker 1: You don't need to remember every detail, and you don't
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  Speaker 1: need to follow every thought. Just listen and drift, and slowly, gently, together.
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  Speaker 1: Let's begin by looking upward, toward the darkness above you.
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  Speaker 1: For a moment, you can simply remain where you are.
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  Speaker 1: There is no need to imagine anything complicated. Perhaps the
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  Speaker 1: room around you is quiet. Perhaps there is a small
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  Speaker 1: mechanical sound somewhere in the distance. Perhaps a fan is
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  Speaker 1: moving the air so gently that you can barely notice it,
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  Speaker 1: and beneath all of this ordinary night-time stillness, the earth
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  Speaker 1: is already turning. You do not feel it. You do
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  Speaker 1: not hear it. You do not notice the movement beneath you,
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  Speaker 1: and yet, slowly, continuously, your entire world is rotating through space.
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  Speaker 1: you are resting on a planet, a small, blue world
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  Speaker 1: covered with oceans, clouds, mountains, forests, cities, and countless quiet
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  Speaker 1: rooms like the one you are in now. From where
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  Speaker 1: you are lying, Earth can feel enormous. It takes days
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  Speaker 1: to cross it by airplane, weeks or months to cross
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  Speaker 1: parts of it by older forms of travel, and a
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  Speaker 1: lifetime to experience more than a small portion of its landscapes.
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  Speaker 1: But from far enough away, Earth becomes something very different.
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  Speaker 1: A small sphere. A little world turning silently in the dark.
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  Speaker 1: And beyond it, the moon moves around you, following its
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  Speaker 1: slow path through space, while Earth follows a much larger
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  Speaker 1: path around the sun. The sun itself is so large
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  Speaker 1: that more than a million Earth-sized worlds could fit inside it,
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  Speaker 1: if you could somehow place them there. Yet even the sun,
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  Speaker 1: which seems so dominant from your small position on Earth,
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  Speaker 1: is only one star, one star among many. You can
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  Speaker 1: picture it now, perhaps as a single warm point of light,
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  Speaker 1: glowing quietly in the darkness. And then, slowly, let your
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  Speaker 1: imagination move farther away. The sun becomes smaller. The earth
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  Speaker 1: becomes smaller. The planets become difficult to distinguish. The solar
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  Speaker 1: system begins to look less like a collection of worlds
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  Speaker 1: and more like a tiny moving region inside a much
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  Speaker 1: larger darkness. You continue drifting outward, and eventually you begin
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  Speaker 1: to see something enormous taking shape around you. The Milky Way,
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  Speaker 1: a vast galaxy containing hundreds of billions of stars, including
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  Speaker 1: the star you call the Sun. From inside the galaxy,
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  Speaker 1: you cannot easily see its complete shape. You are too
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  Speaker 1: close to it, It is rather like standing inside a
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  Speaker 1: forest and trying to see the entire forest at once.
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  Speaker 1: But if you could drift far above the Milky Way,
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  Speaker 1: you would see a broad, flattened galaxy, with curved spiral
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  Speaker 1: arms extending through space, filled with stars, gas, dust, and
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  Speaker 1: something more mysterious, something we cannot see directly, but whose
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  Speaker 1: gravity helps hold the galaxy together. Astronomers call this unseen
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  Speaker 1: component dark matter. you do not need to picture it
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  Speaker 1: as a strange glowing substance. It does not glow. It
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  Speaker 1: does not announce itself. Instead, you can simply think of
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  Speaker 1: it as part of the invisible gravitational architecture of the galaxy,
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  Speaker 1: something whose presence is inferred from the way stars and
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  Speaker 1: other matter move. And now you can drift farther still.
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  Speaker 1: The Milky Way begins to shrink beneath you. Its spiral
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  Speaker 1: shape becomes smaller. The stars become points. Then the galaxy
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  Speaker 1: itself becomes a small island of light, floating in darkness.
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  Speaker 1: This is where the word distance begins to lose some
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  Speaker 1: of its familiar meaning. Between the sun and the nearest stars,
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  Speaker 1: there are enormous stretches of space, so large that kilometres
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  Speaker 1: no longer feel useful. Astronomers often measure these distances in light-years,
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  Speaker 1: a light-year being the distance light travels in one year,
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  Speaker 1: and light travels extraordinarily quickly. Yet even light needs years
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  Speaker 1: to cross the space between some stars. So when you
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  Speaker 1: look at a distant star, you are not seeing it
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  Speaker 1: exactly as it is now. You are seeing light that
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  Speaker 1: began its journey some time ago. The star may have
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  Speaker 1: been shining in a slightly different place in its own
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  Speaker 1: story when that light first left. The farther away you look,
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  Speaker 1: the older the light can be. Already, without leaving your room,
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  Speaker 1: you can look into the past. and this quiet idea
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  Speaker 1: will become more important as you drift outward. Because the
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  Speaker 1: Milky Way is not alone. There are other galaxies. Hundreds
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  Speaker 1: of billions of stars gathered into one galaxy, and then
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  Speaker 1: another galaxy beyond it, and another, and another, separated by
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  Speaker 1: distances so vast that the darkness between them can become
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  Speaker 1: almost as important as the galaxies themselves. You can imagine
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  Speaker 1: drifting away from the Milky Way now, Its spiral arms
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  Speaker 1: become faint. The stars become tiny. The galaxy becomes a
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  Speaker 1: pale island behind you. And ahead, after an immense stretch
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  Speaker 1: of darkness, another island appears. Then another. Then many more.
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  Speaker 1: And slowly, you begin to understand that the Milky Way,
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  Speaker 1: which once seemed impossibly large, is only one galaxy among
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  Speaker 1: an immense population of galaxies. The observable universe may contain
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  Speaker 1: hundreds of billions of galaxies. and some estimates allow for
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  Speaker 1: numbers approaching two trillion. But even those numbers are difficult
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  Speaker 1: for the human mind to hold. So you do not
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  Speaker 1: need to hold them. You can let them become something softer.
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  Speaker 1: Imagine a dark ocean without waves. Across it, very far apart,
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  Speaker 1: are countless small lights. Each light is not a star.
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  Speaker 1: Each light is an entire galaxy. And within each galaxy
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  Speaker 1: are more stars than you could comfortably count in a lifetime.
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  Speaker 1: You drift quietly among them. Nothing is rushing. Nothing needs
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  Speaker 1: your attention. The galaxies are moving. The stars are moving.
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  Speaker 1: The earth is turning. And the entire universe is changing
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  Speaker 1: with time. But from your quiet place, all of this
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  Speaker 1: movement feels almost still. That is one of the strange
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  Speaker 1: things about cosmic scale. Something can be moving enormously fast,
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  Speaker 1: and yet appear completely calm when you are far enough away.
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  Speaker 1: The Earth turns beneath you. The Sun carries its planets
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  Speaker 1: through the galaxy. The Milky Way moves among other galaxies.
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  Speaker 1: And beyond all of this, space itself is part of
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  Speaker 1: a much larger story. For now, you can simply rest
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  Speaker 1: with the image. One small room. One small planet. One star.
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  Speaker 1: One galaxy. And then, beyond the edge of your imagination,
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  Speaker 1: countless other galaxies. separated by enormous stretches of darkness. You
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  Speaker 1: are not required to reach the end of that darkness.
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  Speaker 1: There may not even be an end that you could reach.
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  Speaker 1: You can simply remain here for a little while, beneath
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  Speaker 1: the quiet sky, knowing that the world around you is
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  Speaker 1: only one small place within something vastly larger. And as
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  Speaker 1: you let that thought become softer, another question begins to appear,
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  Speaker 1: almost by itself. If space can contain something this enormous,
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  Speaker 1: then what exactly is space? And if the universe has
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  Speaker 1: been changing for billions of years, perhaps space and time
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  Speaker 1: themselves are not quite as separate as they seem. You
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  Speaker 1: can remain exactly where you are, resting beneath the quiet
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  Speaker 1: movement of the earth, while the thought of the universe
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  Speaker 1: slowly becomes a little deeper. A moment ago, you were
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  Speaker 1: drifting outward, Watching the earth become smaller, the sun become
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  Speaker 1: a point of light, and the Milky Way become one
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  Speaker 1: island among countless others. Now, instead of moving farther away,
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  Speaker 1: imagine becoming still, very still. Because sometimes, to understand something
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  Speaker 1: as large as the universe, you do not need to
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  Speaker 1: travel farther into it. You only need to become quiet
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  Speaker 1: enough to notice what has always been around you. Space.
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  Speaker 1: It feels so ordinary. that you rarely think about it.
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  Speaker 1: There is the space between you and the wall, the
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  Speaker 1: space between buildings, the space between the earth and the moon,
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  Speaker 1: the space between stars. It seems like an empty background,
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  Speaker 1: something that simply exists so that everything else can exist
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  Speaker 1: inside it. But the deeper you look, the less simple
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  Speaker 1: space becomes. And time is just as familiar. You know
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  Speaker 1: the feeling of one moment passing into another. You know
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  Speaker 1: morning becoming afternoon, afternoon becoming evening, and evening becoming night.
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  Speaker 1: You feel time in the slow movement of your breathing,
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  Speaker 1: in the changing light outside your window, in the quiet
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  Speaker 1: accumulation of ordinary days. Space seems to tell you where
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  Speaker 1: something is. Time seems to tell you when something happens.
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  Speaker 1: For a long time, these ideas were treated as if
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  Speaker 1: they were separate and absolute, like two different parts of
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  Speaker 1: the world. But then, in the early 20th century, Albert
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  Speaker 1: Einstein began changing the way we understand them. His ideas
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  Speaker 1: showed that space and time are deeply connected. They are
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  Speaker 1: not two completely separate backgrounds. They belong to something larger,
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  Speaker 1: something we call space-time. You do not need to imagine
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  Speaker 1: space-time as another object floating somewhere beyond the stars. It
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  Speaker 1: is simply a way of describing the universe in which
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  Speaker 1: distances and moments belong together. If you move very quickly,
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  Speaker 1: measurements of time and distance can change compared with those
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  Speaker 1: made by someone moving differently. If you are close to
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  Speaker 1: a strong concentration of matter, Gravity affects the passage of
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  Speaker 1: time as well. The universe does not carry one perfectly
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  Speaker 1: rigid clock that ticks identically everywhere. Instead, space and time
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  Speaker 1: are woven into the physical story of everything that happens.
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  Speaker 1: And this is where the idea of gravity becomes wonderfully strange.
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  Speaker 1: You may have learned to think of gravity as a
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  Speaker 1: force that pulls. The earth pulls you toward its surface.
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  Speaker 1: The sun holds the planets in their paths. The moon
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  Speaker 1: remains connected to Earth. But Einstein offered another way to
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  Speaker 1: picture this. Matter changes the geometry of spacetime around it,
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  Speaker 1: and objects move through that changing geometry. You can imagine
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  Speaker 1: the space around a star becoming gently shaped by the
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  Speaker 1: star's presence, not like a hard surface being bent, but
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  Speaker 1: more like the paths available through the universe becoming subtly different.
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  Speaker 1: Then a planet follows one of those paths. From your
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  Speaker 1: quiet position on Earth, this appears as gravity. The Earth
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  Speaker 1: does not need to reach outward with an invisible hand.
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  Speaker 1: The motion of the planet, the shape of space and
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  Speaker 1: time around it, and the presence of matter all belong
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  Speaker 1: to one connected description. You do not have to solve
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  Speaker 1: the geometry. You only need to let the idea settle.
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  Speaker 1: Space can have shape. Time can be affected by gravity.
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  Speaker 1: And the universe is not simply a collection of things
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  Speaker 1: placed inside an empty container. The container itself is part
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  Speaker 1: of the story. Perhaps you can imagine yourself drifting again,
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  Speaker 1: but this time without seeing the stars. There is no horizon,
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  Speaker 1: no floor, no ceiling, only an immense quiet surrounding you.
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  Speaker 1: Now imagine a star appearing in the distance. Around it,
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  Speaker 1: nothing looks visibly different. There is no glowing outline around
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  Speaker 1: its gravity. There is no sign painted across the darkness.
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  Speaker 1: And yet, the presence of that star changes the space-time
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  Speaker 1: around it. Nearby objects respond to that geometry. Farther away,
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  Speaker 1: the effect becomes weaker. And across enormous distances, countless stars
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  Speaker 1: can influence one another through gravity, slowly shaping the movements
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  Speaker 1: of galaxies. This quiet influence continues on larger and larger scales.
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  Speaker 1: Stars gather into galaxies, galaxies gather into groups and clusters,
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  Speaker 1: and those structures become part of the immense cosmic web.
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  Speaker 1: Gravity is one of the reasons the universe is not
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  Speaker 1: simply a perfectly empty, evenly scattered darkness. It allows matter
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  Speaker 1: to gather. It gives structure to motion. It helps turn
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  Speaker 1: tiny differences in the young universe into into enormous patterns
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  Speaker 1: that can eventually span millions of light years. So, when
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  Speaker 1: you look at a galaxy, you are not simply looking
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  Speaker 1: at a collection of stars. You are looking at matter
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  Speaker 1: moving through space-time, following paths shaped by gravity, carrying with
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  Speaker 1: it a history that began billions of years ago. And
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  Speaker 1: there is something quietly beautiful about this. The same basic
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  Speaker 1: idea of gravity that keeps your body resting gently against
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  Speaker 1: the bed is also involved in shaping galaxies far beyond
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  Speaker 1: anything you could ever see with your eyes. The scale changes,
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  Speaker 1: the surroundings change, the numbers become almost impossible to imagine,
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  Speaker 1: but the underlying language of nature remains connected. Gravity does
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  Speaker 1: not suddenly become a different kind of gravity when you
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  Speaker 1: move from a falling leaf to a galaxy. The universe
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  Speaker 1: simply gives it more and more room to act. And now,
• 15:08
  Speaker 1: as you remain still, You can let the idea of
• 15:11
  Speaker 1: space-time become less like a scientific phrase and more like
• 15:16
  Speaker 1: a quiet background to everything around you. You are resting
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  Speaker 1: on a planet. The planet is moving around a star.
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  Speaker 1: The star is moving through a galaxy. The galaxy is
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  Speaker 1: moving among other galaxies. And all of these motions take
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  Speaker 1: place within space and time, within the larger structure that
• 15:35
  Speaker 1: Einstein taught us to see differently. Nothing is perfectly still.
• 15:40
  Speaker 1: And yet, from where you are lying, everything can feel
• 15:43
  Speaker 1: completely quiet. The Earth turns without disturbing your rest. The
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  Speaker 1: solar system moves without making a sound. The Milky Way
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  Speaker 1: changes over immense stretches of time. And space-time itself continues
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  Speaker 1: to carry every one of these movements. There is nothing
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  Speaker 1: you need to do with this thought. You can simply
• 16:03
  Speaker 1: let it remain somewhere in the background, like a very
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  Speaker 1: distant light. Because if space and time are part of
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  Speaker 1: the universe itself, then there is another question waiting quietly
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  Speaker 1: beyond them. What happens when space itself begins to change?
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  Speaker 1: What happens when the distance between galaxies is no longer
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  Speaker 1: something fixed, but something that can slowly grow? And to
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  Speaker 1: follow that thought, you will need to let your imagination
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  Speaker 1: drift backward, toward a time when there were no galaxies
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  Speaker 1: at all, when the universe was younger and hotter, and
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  Speaker 1: much more compact than the vast darkness you know tonight.
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  Speaker 1: You can let yourself remain still now, while the idea
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  Speaker 1: of space and time slowly settles into the background. The
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  Speaker 1: earth is turning, the sun is moving through the Milky Way,
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  Speaker 1: the Milky Way is travelling among countless other galaxies, and
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  Speaker 1: all of this is happening inside a universe that has
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  Speaker 1: been changing for an almost unimaginable length of time. billions
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  Speaker 1: of years, more than 13 billion years, a span of
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  Speaker 1: time so long that your mind does not need to
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  Speaker 1: hold it all at once. You can simply imagine it
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  Speaker 1: as a very long, quiet road stretching backward into darkness.
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  Speaker 1: And tonight you can begin walking gently along that road,
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  Speaker 1: not quickly, not trying to reach anything, simply allowing the
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  Speaker 1: present universe to become younger and younger. As you move backward,
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  Speaker 1: The galaxies begin to change. They become less developed. Stars
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  Speaker 1: become younger. The familiar structures of the cosmos slowly fade.
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  Speaker 1: And if you continue drifting backward far enough, there comes
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  Speaker 1: a time when there are no galaxies at all. No
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  Speaker 1: familiar stars. No planets. No quiet blue earth. The universe
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  Speaker 1: was once very different from the one you know now.
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  Speaker 1: It was much hotter, much denser. and the distances that
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  Speaker 1: separate today's galaxies had not yet grown into the enormous
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  Speaker 1: spaces you now imagine between them. This is the beginning
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  Speaker 1: of the story commonly called the Big Bang, but you
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  Speaker 1: do not need to imagine a giant explosion taking place
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  Speaker 1: inside an already existing empty space. There was no ordinary
• 18:25
  Speaker 1: room surrounding the universe, waiting for something to explode inside it. Instead,
• 18:32
  Speaker 1: the early universe itself was in a hot, dense state.
• 18:36
  Speaker 1: and space began expanding. The distances between regions of the
• 18:40
  Speaker 1: universe changed. The universe grew in scale, and as it expanded,
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  Speaker 1: it cooled. You can almost feel that cooling as you
• 18:49
  Speaker 1: imagine yourself drifting backward. At first, everything is intensely hot,
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  Speaker 1: filled with energy and rapidly moving particles. Then, as space expands,
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  Speaker 1: the temperature falls. Not suddenly, not like a switch being
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  Speaker 1: turned off, but gradually, over the enormous unfolding of cosmic time.
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  Speaker 1: Hot becomes less hot, dense becomes less dense, and the
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  Speaker 1: young universe continues to change. Very early in this story,
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  Speaker 1: something extraordinary may have happened. For a tiny fraction of
• 19:26
  Speaker 1: the universe's earliest existence, space may have undergone a period
• 19:30
  Speaker 1: of extraordinarily rapid expansion called inflation. The word sounds dramatic,
• 19:36
  Speaker 1: but you can imagine it very quietly. Imagine a tiny
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  Speaker 1: region of space, changing scale so rapidly that distances within
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  Speaker 1: it become enormously stretched. It is not that ordinary objects
• 19:48
  Speaker 1: are racing through space. Rather, the space itself is changing
• 19:52
  Speaker 1: its scale. A small region becomes vastly larger. And in
• 19:57
  Speaker 1: this process, tiny variations that existed in the early universe
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  Speaker 1: can also be stretched across enormous distances. These variations were
• 20:06
  Speaker 1: incredibly small, barely noticeable, almost like faint differences in an
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  Speaker 1: otherwise smooth surface. But those tiny differences would matter later,
• 20:17
  Speaker 1: much later, because the universe would continue expanding and cooling,
• 20:22
  Speaker 1: and gravity would gradually respond to the places where matter
• 20:26
  Speaker 1: was just slightly more concentrated than its surroundings. A little
• 20:30
  Speaker 1: more matter here, a little less there, nothing dramatic, nothing
• 20:35
  Speaker 1: that would have looked important at the time. but given
• 20:38
  Speaker 1: billions of years, small differences can become large structures. You
• 20:42
  Speaker 1: can let that idea rest gently for a moment. A
• 20:46
  Speaker 1: tiny variation, then a larger variation, then a cloud, then
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  Speaker 1: a star, then a galaxy, and eventually, the great cosmic web.
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  Speaker 1: All of this begins with differences so small that the
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  Speaker 1: young universe itself would have seemed almost smooth. But before
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  Speaker 1: stars could shine … Before galaxies could gather, the universe
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  Speaker 1: had to cool much further. In its early stages, the
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  Speaker 1: cosmos was filled with a hot mixture of charged particles.
• 21:18
  Speaker 1: Scientists call this state plasma. You do not need to
• 21:21
  Speaker 1: picture the word as something complicated. Simply imagine an immense
• 21:25
  Speaker 1: glowing sea, filling the young universe, so hot and dense
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  Speaker 1: that light could not yet travel freely for very long distances.
• 21:34
  Speaker 1: Light was constantly interacting with the charged particles around it.
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  Speaker 1: It was not yet moving through a transparent universe. Everything
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  Speaker 1: was still too crowded, and so the young cosmos remained
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  Speaker 1: filled with a kind of luminous fog. Then the universe
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  Speaker 1: continued expanding. It continued cooling. Eventually, the temperature became low
• 21:55
  Speaker 1: enough for electrons and atomic nuclei to join together and
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  Speaker 1: form neutral atoms. The fog began to clear. and something
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  Speaker 1: quiet happened. Light could finally travel freely across the expanding universe.
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  Speaker 1: That ancient light is still moving through space today. You
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  Speaker 1: cannot see it with your eyes. It has been stretched
• 22:15
  Speaker 1: and cooled by the expansion of the universe, but instruments
• 22:19
  Speaker 1: can detect it. Astronomers call it the cosmic microwave background.
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  Speaker 1: You can think of it simply as an ancient glow,
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  Speaker 1: a faint afterlight from a much younger universe. It has
• 22:32
  Speaker 1: been travelling for billions of years, across an expanding cosmos,
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  Speaker 1: across enormous distances, until some of it finally reaches you.
• 22:42
  Speaker 1: When you look at this ancient radiation through scientific instruments,
• 22:46
  Speaker 1: you are not looking at the universe as it appears today.
• 22:49
  Speaker 1: You are looking at a much younger universe, a universe
• 22:53
  Speaker 1: before galaxies, before stars, before planets, before Earth. before anyone
• 23:00
  Speaker 1: was here to wonder about any of it. And within
• 23:03
  Speaker 1: that ancient light are tiny variations in temperature and density,
• 23:08
  Speaker 1: small differences, almost impossibly small. Yet those differences contain the
• 23:14
  Speaker 1: early outlines of the structure that would eventually emerge. Over
• 23:18
  Speaker 1: immense periods of time, gravity slowly gathers matter, gas begins
• 23:24
  Speaker 1: to collect, clouds become denser, the first stars eventually ignite,
• 23:29
  Speaker 1: Stars gather into galaxies, galaxies gather into larger structures, and
• 23:34
  Speaker 1: the quiet pattern begins to grow. You can imagine watching
• 23:38
  Speaker 1: this from very far away. At first, there is almost
• 23:42
  Speaker 1: nothing to see. A young, glowing universe. Smooth, hot, full
• 23:48
  Speaker 1: of light. Then, slowly, tiny differences begin to matter. The
• 23:53
  Speaker 1: smallest variations become the earliest hints of future structure. The
• 23:57
  Speaker 1: universe cools. Space expands, matter gathers, light travels, and time continues.
• 24:05
  Speaker 1: Nothing needs to happen quickly. The universe has never needed
• 24:09
  Speaker 1: to hurry. Even the largest structures you can imagine are
• 24:13
  Speaker 1: built through processes that unfold across enormous stretches of time.
• 24:18
  Speaker 1: And perhaps there is something comforting in that. The galaxies
• 24:21
  Speaker 1: above you were not placed into the darkness all at once.
• 24:25
  Speaker 1: They emerged gradually. The stars did not appear together. They
• 24:29
  Speaker 1: formed over time. The cosmic web was not drawn in
• 24:33
  Speaker 1: a single moment. It grew from tiny differences that were
• 24:37
  Speaker 1: present when the universe was young. So when you look
• 24:40
  Speaker 1: upward tonight, you are not looking at a finished picture.
• 24:44
  Speaker 1: You are looking at the result of a very long unfolding,
• 24:47
  Speaker 1: a story in which space expanded, temperatures fell, light was released,
• 24:53
  Speaker 1: matter gathered, and simple beginnings slowly became the enormous architecture
• 24:58
  Speaker 1: surrounding you. And somewhere within that ancient story, the first
• 25:03
  Speaker 1: stars were waiting to appear, small points of light in
• 25:06
  Speaker 1: a universe that had never seen a star before. Their
• 25:10
  Speaker 1: light would eventually travel outward through the growing darkness, and
• 25:14
  Speaker 1: much later, some of that ancient light would become part
• 25:17
  Speaker 1: of the sky you see from your small place on Earth.
• 25:23
  Speaker 1: The first stars are beginning to appear now, very quietly,
• 25:27
  Speaker 1: in the deep history of the universe. You do not
• 25:30
  Speaker 1: need to imagine a sudden sky filled with them. There
• 25:34
  Speaker 1: is no instant when the darkness simply disappears. Instead, the
• 25:38
  Speaker 1: first stars emerge one by one, in different places, separated
• 25:44
  Speaker 1: by enormous distances, each one beginning its long life inside
• 25:48
  Speaker 1: the young cosmos. And around them, the universe is still changing.
• 25:54
  Speaker 1: Space continues to expand. The temperature continues to fall. Gravity
• 26:00
  Speaker 1: continues its patient work. You can let yourself rest with
• 26:03
  Speaker 1: that word for a moment. Gravity. A gentle tendency for
• 26:07
  Speaker 1: matter to gather. A quiet influence that never needs to hurry.
• 26:12
  Speaker 1: Long before you were here, long before the Earth existed,
• 26:15
  Speaker 1: gravity was already shaping the universe. It began with very
• 26:19
  Speaker 1: small differences. Some regions of the young cosmos contained just
• 26:24
  Speaker 1: a little more matter than others. The difference was tiny.
• 26:28
  Speaker 1: Almost nothing. But gravity notices even tiny differences when it
• 26:32
  Speaker 1: has enough time. A region with slightly more matter has
• 26:36
  Speaker 1: slightly more gravitational influence. It gathers a little more matter.
• 26:41
  Speaker 1: That additional matter strengthens the gravitational influence. More matter gathers,
• 26:47
  Speaker 1: and then more. Very slowly, very patiently, the small difference
• 26:52
  Speaker 1: begins to grow. You can imagine standing far above this
• 26:56
  Speaker 1: ancient universe. looking down into something that has no true
• 27:01
  Speaker 1: floor and no true ceiling. At first everything seems almost smooth,
• 27:07
  Speaker 1: then faint patterns begin to appear. Slightly denser regions here,
• 27:12
  Speaker 1: slightly emptier regions there. The pattern is so subtle that
• 27:17
  Speaker 1: you might hardly notice it. Yet over millions and billions
• 27:21
  Speaker 1: of years these quiet differences become important. One of the
• 27:25
  Speaker 1: ingredients in this story is something scientists call dark matter.
• 27:30
  Speaker 1: The name sounds mysterious, but the basic idea can remain simple.
• 27:35
  Speaker 1: Dark matter does not shine like a star. It does
• 27:38
  Speaker 1: not glow like ordinary gas. You cannot look at it
• 27:41
  Speaker 1: directly with your eyes, but its gravity affects the matter
• 27:45
  Speaker 1: around it. So scientists can notice its presence through the
• 27:49
  Speaker 1: way stars and galaxies move, and through the large-scale structure
• 27:53
  Speaker 1: of the universe. You can think of it as unseen
• 27:57
  Speaker 1: matter helping to shape the gravitational landscape in which ordinary
• 28:02
  Speaker 1: matter gathers. Gas slowly follows these gravitational patterns. Clouds of
• 28:08
  Speaker 1: gas become larger, some regions become denser, and eventually, inside
• 28:14
  Speaker 1: some of these clouds, gravity draws material inward until the
• 28:18
  Speaker 1: centre becomes hot and dense enough for a star to
• 28:22
  Speaker 1: begin shining. A new light appears. then another, then another.
• 28:28
  Speaker 1: The universe becomes less empty. Not because the darkness is disappearing,
• 28:33
  Speaker 1: but because small islands of light are beginning to form
• 28:36
  Speaker 1: within it. And those islands do not remain alone. Stars
• 28:40
  Speaker 1: gather together. Many stars can become part of a galaxy.
• 28:44
  Speaker 1: A galaxy may contain millions, billions, or even hundreds of
• 28:48
  Speaker 1: billions of stars, together with gas, dust, dark matter, and
• 28:53
  Speaker 1: other material. Some galaxies become broad and graceful. Some become rounded.
• 28:59
  Speaker 1: Some remain irregular. Some change their shape through encounters with
• 29:03
  Speaker 1: other galaxies. You can imagine two enormous clouds of stars
• 29:08
  Speaker 1: slowly approaching one another across space. There is no sound
• 29:12
  Speaker 1: in the vacuum between them. No crashing noise. No sharp
• 29:16
  Speaker 1: collision like two solid objects striking together. Instead, gravity gradually
• 29:22
  Speaker 1: changes their paths. Their stars move through one another. Gas
• 29:26
  Speaker 1: clouds interact. New stars may form. The shapes of the
• 29:30
  Speaker 1: galaxies become disturbed, and over a very long period, the
• 29:34
  Speaker 1: two galaxies can become one larger galaxy. Even this enormous
• 29:39
  Speaker 1: event can remain gentle when viewed across cosmic time. The
• 29:43
  Speaker 1: universe does not rush. It changes slowly enough that a
• 29:47
  Speaker 1: human lifetime is almost invisible within the process. And while
• 29:51
  Speaker 1: individual galaxies are forming, they are also gathering into larger groups.
• 29:56
  Speaker 1: A galaxy can belong to a group of galaxies. Groups
• 30:00
  Speaker 1: can be part of larger clusters. Clusters can gather into
• 30:04
  Speaker 1: even larger arrangements. And when you continue zooming outward, something
• 30:09
  Speaker 1: remarkable begins to appear. The universe does not distribute galaxies
• 30:13
  Speaker 1: completely at random. Instead, galaxies trace an enormous pattern, long strands,
• 30:21
  Speaker 1: broad sheets, dense knots, and enormous empty regions between them. Together,
• 30:27
  Speaker 1: these structures form what scientists call the cosmic web. You
• 30:32
  Speaker 1: can imagine it very softly, not as a physical net
• 30:35
  Speaker 1: hanging somewhere in space, but as a vast pattern of
• 30:39
  Speaker 1: matter spread across the universe. The galaxies are like points
• 30:43
  Speaker 1: of light following the pattern. The dark matter provides much
• 30:47
  Speaker 1: of the unseen gravitational structure. Gas flows toward denser regions.
• 30:53
  Speaker 1: Galaxies gather where gravity has created deeper concentrations of matter.
• 30:58
  Speaker 1: And between these regions are enormous cosmic voids, places where
• 31:03
  Speaker 1: matter is much more thinly distributed. The word void can
• 31:07
  Speaker 1: sound like absolute emptiness. But even these regions are not
• 31:11
  Speaker 1: necessarily perfect nothingness. They are simply much less crowded. There
• 31:16
  Speaker 1: may still be faint traces of matter. There may still
• 31:20
  Speaker 1: be distant galaxies. There may still be particles moving through
• 31:24
  Speaker 1: the immense darkness, yet compared with the dense regions around them,
• 31:28
  Speaker 1: the voids are extraordinarily quiet. You can let your imagination
• 31:33
  Speaker 1: drift through one now. You are moving through an enormous
• 31:36
  Speaker 1: region of space where galaxies are rare. There is almost
• 31:40
  Speaker 1: nothing nearby. No bright stars close enough to fill your view.
• 31:45
  Speaker 1: No familiar horizon, just darkness, distance, and a few faint
• 31:50
  Speaker 1: points of light far away. You continue drifting, and eventually,
• 31:55
  Speaker 1: the pattern becomes visible again. A distant strand of the
• 31:58
  Speaker 1: cosmic web. A long region where galaxies gather. A place
• 32:03
  Speaker 1: where matter has slowly collected across billions of years. From
• 32:07
  Speaker 1: this distance, the individual galaxies are almost too small to distinguish.
• 32:12
  Speaker 1: The structure itself becomes more important than the individual lights.
• 32:17
  Speaker 1: You are beginning to see the universe not as a
• 32:19
  Speaker 1: collection of separate galaxies, but as one enormous evolving pattern.
• 32:24
  Speaker 1: Small differences became larger differences. Gravity gathered matter. Matter formed clouds.
• 32:31
  Speaker 1: Clouds formed stars. Stars gathered into galaxies. Galaxies gathered into
• 32:37
  Speaker 1: groups and clusters. And these larger structures traced the great
• 32:42
  Speaker 1: cosmic web. The entire process is a kind of quiet accumulation.
• 32:47
  Speaker 1: Nothing needs to be dramatic. Nothing needs to happen all
• 32:50
  Speaker 1: at once. The universe simply keeps changing, and you can
• 32:55
  Speaker 1: rest with the thought that some of the largest structures
• 32:58
  Speaker 1: you see today began with differences so small that they
• 33:02
  Speaker 1: were almost impossible to notice. A little more matter here,
• 33:06
  Speaker 1: a little less matter there. A faint unevenness in a
• 33:10
  Speaker 1: very young universe. Then time, then gravity, then gathering, and
• 33:17
  Speaker 1: eventually the enormous architecture of the cosmos. You are safe
• 33:21
  Speaker 1: to let the details become blurry now. You do not
• 33:24
  Speaker 1: need to remember the names of every structure. You can
• 33:27
  Speaker 1: simply keep the feeling of scale. Tiny beginnings. Slow gathering.
• 33:33
  Speaker 1: Enormous results. And perhaps, as you drift through this immense
• 33:37
  Speaker 1: web of galaxies, you can begin to notice something else.
• 33:42
  Speaker 1: When you look outward into space, you are never seeing
• 33:45
  Speaker 1: the universe exactly as it is now. You are seeing
• 33:48
  Speaker 1: light that has travelled. And light takes time. So every
• 33:53
  Speaker 1: distant galaxy is also carrying a little piece of the
• 33:56
  Speaker 1: past toward you. The farther you look, the farther backward
• 34:00
  Speaker 1: your view can reach. And somewhere beyond the nearest galaxies,
• 34:05
  Speaker 1: beyond the clusters and filaments that seem so immense, there
• 34:08
  Speaker 1: are lights arriving from a universe much younger than the
• 34:11
  Speaker 1: one surrounding you now. You only need to remain still.
• 34:16
  Speaker 1: The ancient light is already on its way. The ancient
• 34:21
  Speaker 1: light is already on its way. You can let that
• 34:24
  Speaker 1: thought remain with you for a little while. Somewhere in
• 34:27
  Speaker 1: the darkness above you, light is moving quietly through space.
• 34:32
  Speaker 1: It may have begun its journey millions of years ago,
• 34:35
  Speaker 1: or billions of years ago. And although you are resting
• 34:39
  Speaker 1: here now, beneath your familiar ceiling, some of the light
• 34:43
  Speaker 1: reaching scientific instruments on Earth has been travelling for almost
• 34:47
  Speaker 1: the entire history of the universe. This is one of
• 34:50
  Speaker 1: the quietest, strange things about looking into space. When you
• 34:55
  Speaker 1: look far away, you are also looking backward. You do
• 34:59
  Speaker 1: not see a distant galaxy exactly as it is today.
• 35:02
  Speaker 1: You see the galaxy as it was when the light
• 35:04
  Speaker 1: you are receiving began its journey toward you. The farther
• 35:08
  Speaker 1: away the galaxy is, the longer its light has been travelling,
• 35:13
  Speaker 1: and so the farther you look, the deeper into cosmic
• 35:16
  Speaker 1: history you can see. You can imagine yourself drifting outward now.
• 35:21
  Speaker 1: At first, you pass familiar distances. The moon is nearby
• 35:25
  Speaker 1: on the cosmic scale. The planets are farther away. The
• 35:29
  Speaker 1: sun is farther still. Then the stars of the Milky
• 35:33
  Speaker 1: Way begin to surround you. Some of their light has
• 35:36
  Speaker 1: taken years to reach Earth. You move farther. The Milky
• 35:40
  Speaker 1: Way becomes smaller behind you. Other galaxies appear. And each
• 35:44
  Speaker 1: galaxy becomes more than a distant collection of stars. each
• 35:48
  Speaker 1: one becomes a message from another time, a quiet message
• 35:52
  Speaker 1: carried by light. You do not need to imagine the
• 35:55
  Speaker 1: light as speaking, it simply arrives. Its colour, brightness and
• 36:00
  Speaker 1: patterns contain information about where it came from and what
• 36:03
  Speaker 1: was happening when it began its journey. One of the
• 36:06
  Speaker 1: clues astronomers can observe is called redshift. The name can
• 36:11
  Speaker 1: sound complicated, but the basic idea is gentle. As the
• 36:16
  Speaker 1: universe expands, The space through which light travels also expands.
• 36:21
  Speaker 1: The waves of light become stretched. For visible light, this
• 36:25
  Speaker 1: stretching can shift its appearance toward the redder part of
• 36:28
  Speaker 1: the spectrum. So when astronomers measure the light from distant galaxies,
• 36:33
  Speaker 1: they can detect the imprint of the universe's expansion. The
• 36:37
  Speaker 1: light has travelled across an expanding cosmos. And in a sense,
• 36:42
  Speaker 1: the universe has gently stretched the journey along the way.
• 36:46
  Speaker 1: You can think of the light as carrying a record
• 36:48
  Speaker 1: of its passage, not a written record, not a message
• 36:52
  Speaker 1: made for anyone in particular, simply the physical traces left
• 36:56
  Speaker 1: behind as light moves through an evolving universe. And this
• 37:00
  Speaker 1: is why astronomy can feel a little like archaeology. Instead
• 37:04
  Speaker 1: of digging into the ground, you look into the sky.
• 37:08
  Speaker 1: Instead of uncovering ancient stones, you receive ancient photons. The
• 37:13
  Speaker 1: farther away they began, the older the scene you are seeing.
• 37:17
  Speaker 1: There is something wonderfully quiet about that. You can remain
• 37:21
  Speaker 1: exactly where you are and still look backward through billions
• 37:24
  Speaker 1: of years. You do not need a machine that travels
• 37:27
  Speaker 1: through time. You only need light that has been travelling
• 37:31
  Speaker 1: for a very long time. Astronomers have used this idea
• 37:34
  Speaker 1: to create some of the deepest views of the universe.
• 37:38
  Speaker 1: One famous example came from the Hubble Space Telescope. Astronomers
• 37:42
  Speaker 1: pointed the telescope toward a tiny region of sky that
• 37:46
  Speaker 1: appeared almost empty. There were no obvious bright stars filling
• 37:50
  Speaker 1: the view. At first glance, it looked like a patch
• 37:53
  Speaker 1: of darkness, but the telescope continued collecting light. Very faint light.
• 37:58
  Speaker 1: Light that had travelled enormous distances, and when the image
• 38:02
  Speaker 1: was assembled, the darkness was transformed. Thousands of distant galaxies appeared.
• 38:09
  Speaker 1: Some were large and bright. Others were tiny and faint.
• 38:13
  Speaker 1: Some looked familiar. Others looked irregular and young. And many
• 38:17
  Speaker 1: were so distant that the light reaching the telescope had
• 38:21
  Speaker 1: begun its journey when the universe was much younger. You
• 38:25
  Speaker 1: can imagine looking at that image slowly, not as a
• 38:28
  Speaker 1: photograph crowded with objects, but as a window, a tiny
• 38:33
  Speaker 1: window opening onto an enormous amount of space and time.
• 38:37
  Speaker 1: Each point of light represents a place. and each place
• 38:41
  Speaker 1: is being seen at a particular moment in its history.
• 38:45
  Speaker 1: One galaxy may appear relatively mature, another may appear smaller
• 38:49
  Speaker 1: and less organised, another may be surrounded by signs of
• 38:53
  Speaker 1: intense star formation, and another may be so faint that
• 38:57
  Speaker 1: you can barely tell it is a galaxy at all.
• 39:00
  Speaker 1: You are seeing different ages of the universe at once.
• 39:04
  Speaker 1: The sky becomes a kind of layered history. Closer galaxies
• 39:08
  Speaker 1: show you something closer to the present. Farther galaxies show
• 39:12
  Speaker 1: you earlier stages. And deeper still, you approach the time
• 39:17
  Speaker 1: when the first generations of galaxies were beginning to form.
• 39:20
  Speaker 1: This does not mean that distant galaxies are literally frozen
• 39:24
  Speaker 1: in the past. They have continued changing after the light
• 39:28
  Speaker 1: you see today began its journey. A galaxy that appears
• 39:32
  Speaker 1: young to you may now be much older. It may
• 39:35
  Speaker 1: have merged with another galaxy. Its stars may have changed.
• 39:39
  Speaker 1: Its shape may have transformed. But you have not received
• 39:44
  Speaker 1: those later events yet. Their newer light is still travelling.
• 39:48
  Speaker 1: And perhaps... In another unimaginably distant future, some later light
• 39:53
  Speaker 1: from that same galaxy may arrive. You would then see
• 39:56
  Speaker 1: another moment in its history, another quiet page, another view
• 40:01
  Speaker 1: of a changing universe. The farther you look, the more
• 40:05
  Speaker 1: difficult the observation becomes. Ancient galaxies are often extremely faint.
• 40:11
  Speaker 1: Their light has travelled for billions of years. Expansion has
• 40:15
  Speaker 1: stretched that light. and some of the earliest galaxies emit
• 40:19
  Speaker 1: much of their energy in wavelengths that are difficult for
• 40:23
  Speaker 1: human eyes to see. This is why modern observatories can
• 40:27
  Speaker 1: use infrared light. Infrared light allows astronomers to observe some
• 40:32
  Speaker 1: of the very distant, early galaxies whose light has been
• 40:36
  Speaker 1: stretched during its long journey. You can imagine the telescope
• 40:40
  Speaker 1: waiting patiently in the darkness. No hurry, no noise, simply
• 40:46
  Speaker 1: collecting faint traces of ancient light. A few photons arrive,
• 40:51
  Speaker 1: then a few more, and slowly an image begins to emerge,
• 40:56
  Speaker 1: a tiny object, a distant galaxy, a place that existed
• 41:00
  Speaker 1: when the universe was young. You are still here, resting
• 41:04
  Speaker 1: quietly on Earth, and yet, through light, you can reach
• 41:09
  Speaker 1: backward toward a time when our planet did not exist.
• 41:13
  Speaker 1: There were no oceans here. no mountains, no forests, no
• 41:18
  Speaker 1: human voices. The Milky Way itself was still changing. The
• 41:23
  Speaker 1: stars around us had not yet formed in their present arrangements.
• 41:27
  Speaker 1: And still, the light was moving, across the growing universe,
• 41:32
  Speaker 1: across enormous stretches of space, carrying with it the faint
• 41:36
  Speaker 1: appearance of ancient worlds of stars. This is why the
• 41:40
  Speaker 1: night sky is never simply a picture of where things are,
• 41:44
  Speaker 1: It is also a picture of when things were. The
• 41:47
  Speaker 1: stars you see are not all showing you the same
• 41:50
  Speaker 1: age of the universe. Nearby stars reveal relatively recent light.
• 41:55
  Speaker 1: Distant galaxies reveal older light. And the deepest observations reveal
• 42:00
  Speaker 1: a cosmos from an era so ancient that almost everything
• 42:04
  Speaker 1: familiar had yet to take shape. So you can let
• 42:08
  Speaker 1: yourself drift with that idea now. Space is not only distance.
• 42:13
  Speaker 1: Space is also a path through time. A light year
• 42:18
  Speaker 1: is not merely a measurement on a map. It is
• 42:21
  Speaker 1: also a reminder that light needs time to cross a distance,
• 42:25
  Speaker 1: and every distant light carries some history with it. You
• 42:29
  Speaker 1: look outward. The universe looks older. You look farther. The
• 42:33
  Speaker 1: past becomes deeper. And as you continue drifting toward the
• 42:37
  Speaker 1: edge of what light has had time to bring you,
• 42:40
  Speaker 1: another quiet boundary begins to appear. Not a wall, not
• 42:45
  Speaker 1: an edge, just a limit created by time, distance, and
• 42:50
  Speaker 1: the expanding universe. A place beyond which light from certain
• 42:54
  Speaker 1: regions has not had enough time to reach you. And
• 42:58
  Speaker 1: beyond that boundary, the universe continues, quietly, vastly, without needing
• 43:05
  Speaker 1: to end where your view ends. The ancient light has
• 43:11
  Speaker 1: been travelling for an almost unimaginable length of time, and now,
• 43:16
  Speaker 1: as you drift farther outward in your imagination, you begin
• 43:20
  Speaker 1: to approach something very strange. Not an object, not a planet,
• 43:25
  Speaker 1: not a distant wall floating in darkness. Instead, you approach
• 43:30
  Speaker 1: the limit of what light has had enough time to
• 43:32
  Speaker 1: show you. You can remain perfectly still while imagining this.
• 43:37
  Speaker 1: There is nothing to do. You are safe. You do
• 43:40
  Speaker 1: not need to reach the boundary, you only need to
• 43:43
  Speaker 1: notice the idea of it. The universe is enormous, but
• 43:47
  Speaker 1: your view of the universe is limited by time. Light
• 43:51
  Speaker 1: needs time to travel, and the universe has existed for
• 43:54
  Speaker 1: a finite amount of time. So there are regions of
• 43:57
  Speaker 1: space whose light has not yet had enough time to
• 44:00
  Speaker 1: reach you. Some light is still travelling, some distant light
• 44:05
  Speaker 1: may arrive in the unimaginably distant future, and some light,
• 44:09
  Speaker 1: because of the continuing expansion of space, may never reach
• 44:13
  Speaker 1: you at all. This creates what is often called the
• 44:17
  Speaker 1: cosmic horizon or the particle horizon. The words can sound
• 44:21
  Speaker 1: like something solid, but the horizon is not a wall.
• 44:25
  Speaker 1: There is no cosmic surface waiting somewhere in the darkness.
• 44:29
  Speaker 1: There is no place where space suddenly stops. There is
• 44:33
  Speaker 1: simply a limit to how far information carried by light
• 44:36
  Speaker 1: has been able to reach you since the universe began.
• 44:40
  Speaker 1: You can imagine yourself standing beside a very calm ocean
• 44:43
  Speaker 1: at night. There is no physical line where the sea ends.
• 44:47
  Speaker 1: The horizon is simply where your view becomes limited by
• 44:50
  Speaker 1: distance and the curvature of the earth. In the universe,
• 44:54
  Speaker 1: the idea is different, but the feeling is somewhat similar.
• 44:58
  Speaker 1: You can look outward only as far as the light
• 45:00
  Speaker 1: has been able to bring information to you. Beyond that,
• 45:04
  Speaker 1: there may be more space, there may be more galaxies,
• 45:07
  Speaker 1: there may be more clusters or There may be more
• 45:10
  Speaker 1: cosmic web, but their light is not yet part of
• 45:13
  Speaker 1: your view. And this is where the enormous scale of
• 45:16
  Speaker 1: the universe becomes especially difficult to imagine. The observable universe
• 45:21
  Speaker 1: is already incredibly large. The distance to the most distant
• 45:25
  Speaker 1: regions we can observe is measured in tens of billions
• 45:29
  Speaker 1: of light years. Yet, this does not mean the universe
• 45:33
  Speaker 1: itself is only that large. it means that this is
• 45:37
  Speaker 1: approximately the region from which information has been able to
• 45:40
  Speaker 1: reach us. Your observable universe is the portion of the
• 45:44
  Speaker 1: cosmos that is visible from your particular location, and there
• 45:49
  Speaker 1: is something quietly beautiful about that word, your, because every
• 45:54
  Speaker 1: observer has their own observable universe. If you were standing
• 45:58
  Speaker 1: on a planet around another star, your horizon would be
• 46:01
  Speaker 1: centred on you. Move somewhere else, and the boundary of
• 46:05
  Speaker 1: what you can observe would shift with you. The universe
• 46:09
  Speaker 1: does not have one special location from which everything can
• 46:12
  Speaker 1: be seen. There is no privileged cosmic balcony. You are
• 46:16
  Speaker 1: simply standing at one point within an enormous expanding cosmos,
• 46:20
  Speaker 1: and light is arriving from every direction. You can imagine
• 46:24
  Speaker 1: looking outward in one direction, then turning slowly, another direction,
• 46:30
  Speaker 1: and another. Everywhere you look your observable universe surrounds you,
• 46:35
  Speaker 1: A vast sphere of information, centred not because you are important,
• 46:39
  Speaker 1: but simply because observation always happens from somewhere. And beyond
• 46:44
  Speaker 1: that sphere, space does not suddenly become different. There is
• 46:48
  Speaker 1: no reason to imagine a great darkness beginning exactly at
• 46:51
  Speaker 1: the edge. The darkness is already everywhere. What changes is
• 46:56
  Speaker 1: only your ability to receive information from what lies farther away.
• 47:01
  Speaker 1: This distinction is important. The edge of your view is
• 47:04
  Speaker 1: is not necessarily the edge of reality. It is only
• 47:08
  Speaker 1: the edge of what has been able to communicate with
• 47:10
  Speaker 1: you through light. You can let that thought become very
• 47:14
  Speaker 1: soft now. A boundary without a wall. A limit without
• 47:18
  Speaker 1: an ending. A horizon without a place to stand. And
• 47:22
  Speaker 1: the expanding universe makes this even more interesting. As space expands,
• 47:28
  Speaker 1: the distance between very distant regions can grow. Light travelling
• 47:33
  Speaker 1: toward you is moving through that expanding space. The space
• 47:38
  Speaker 1: along its path can stretch while the light is travelling,
• 47:42
  Speaker 1: so the journey is not taking place across a fixed
• 47:44
  Speaker 1: cosmic landscape. The landscape itself is changing. A photon begins
• 47:50
  Speaker 1: its journey in one region of space. It moves onward. Meanwhile,
• 47:55
  Speaker 1: the space between its starting point and you continues to expand.
• 48:00
  Speaker 1: The light keeps travelling, but the distance it must cross
• 48:04
  Speaker 1: can continue changing. For sufficiently distant regions, expansion can become
• 48:09
  Speaker 1: so significant that their light can never reach you. This
• 48:12
  Speaker 1: does not mean those galaxies are locally moving through space
• 48:16
  Speaker 1: faster than light. Instead, the space between distant regions is expanding.
• 48:22
  Speaker 1: The distinction is subtle, but you do not need to
• 48:24
  Speaker 1: hold the technical details. You can simply remember that space
• 48:28
  Speaker 1: itself can change while light is travelling through it. and
• 48:32
  Speaker 1: so there are places in the universe whose light is
• 48:35
  Speaker 1: beyond your reach. Not because the places are hidden behind
• 48:38
  Speaker 1: a physical barrier, not because someone has closed a door,
• 48:42
  Speaker 1: simply because the universe is expanding, light has a finite speed,
• 48:47
  Speaker 1: and cosmic time has only been unfolding for so long.
• 48:51
  Speaker 1: You can rest with that. There is something strangely peaceful
• 48:55
  Speaker 1: about not being able to see everything. You do not
• 48:58
  Speaker 1: need to know the entire universe. You could not. Even
• 49:02
  Speaker 1: the observable portion contains more galaxies, more stars, more clouds
• 49:07
  Speaker 1: of gas, and more history than a human mind could
• 49:10
  Speaker 1: ever hold. And beyond what you can observe, the universe
• 49:14
  Speaker 1: may continue much farther. It may be enormously larger than
• 49:18
  Speaker 1: the observable region. It may even be infinite. Scientists do
• 49:23
  Speaker 1: not yet know the complete answer. Measurements of the large-scale
• 49:27
  Speaker 1: geometry of the universe can tell us much about its
• 49:31
  Speaker 1: shape and curvature, but they do not give us a
• 49:33
  Speaker 1: simple map showing where the entire cosmos ends. The uploaded
• 49:38
  Speaker 1: material likewise emphasises that the exact total size remains uncertain
• 49:44
  Speaker 1: and depends on measurements of the universe's curvature and assumptions
• 49:48
  Speaker 1: about its overall shape. So you can allow the question
• 49:52
  Speaker 1: to remain open. How large is everything? You do not
• 49:56
  Speaker 1: need an answer tonight. Perhaps the most honest answer is
• 50:00
  Speaker 1: simply that the observable universe is the part you can see,
• 50:04
  Speaker 1: while the full universe may extend far beyond it. And
• 50:08
  Speaker 1: there is another quiet detail. The observable universe itself is
• 50:13
  Speaker 1: not a permanent bubble. As time passes, more ancient light
• 50:18
  Speaker 1: can arrive. Your view can change. The boundary of observation
• 50:23
  Speaker 1: can shift. New information can cross the distances that once
• 50:27
  Speaker 1: separated it from you. But because cosmic expansion continues, there
• 50:33
  Speaker 1: are also regions whose light will gradually become inaccessible. The
• 50:37
  Speaker 1: horizon is therefore not merely a distant circle drawn around you.
• 50:42
  Speaker 1: It is part of an evolving relationship between space, time,
• 50:46
  Speaker 1: light and expansion. You can imagine yourself floating gently near
• 50:51
  Speaker 1: that invisible boundary now. Behind you are galaxies whose ancient
• 50:55
  Speaker 1: light has already arrived. Ahead of you are regions whose
• 51:00
  Speaker 1: light is still travelling. Farther still are places whose light
• 51:04
  Speaker 1: may never reach you. And beyond all of this, perhaps,
• 51:08
  Speaker 1: the universe continues quietly outward. More space. More darkness. More galaxies.
• 51:15
  Speaker 1: More distances. Nothing tells you exactly where everything ends. There
• 51:20
  Speaker 1: is no sign hanging in the darkness. No final wall.
• 51:25
  Speaker 1: Only the quiet limit of what can reach you. And
• 51:28
  Speaker 1: perhaps that is enough. You can let your imagination stop
• 51:32
  Speaker 1: trying to see farther. You can return gently to the
• 51:35
  Speaker 1: small room around you, the ceiling above you, the surface
• 51:39
  Speaker 1: beneath you, the soft movement of your breathing, the distant
• 51:43
  Speaker 1: sounds of the night. You are here. And far beyond you,
• 51:48
  Speaker 1: the universe continues. Somewhere, ancient light is still travelling. Somewhere,
• 51:54
  Speaker 1: galaxies are still forming. Somewhere, enormous regions of space remain
• 52:00
  Speaker 1: forever beyond your horizons. And the cosmos does not need
• 52:04
  Speaker 1: you to see all of it. It simply continues, quietly,
• 52:08
  Speaker 1: beyond the edge of your view. For now, you can
• 52:11
  Speaker 1: rest here, beneath the small portion of the universe that
• 52:15
  Speaker 1: happens to be visible from where you are. The universe
• 52:20
  Speaker 1: continues to expand. You can let those words become almost
• 52:24
  Speaker 1: like a slow breath, expanding, growing, stretching the distances between
• 52:30
  Speaker 1: distant galaxies. Nothing is rushing. Nothing is suddenly changing. The
• 52:36
  Speaker 1: cosmos simply continues its long movement through time. And for
• 52:40
  Speaker 1: much of its history, something familiar was helping to slow
• 52:44
  Speaker 1: that expansion. Gravity. You have already met gravity as the
• 52:49
  Speaker 1: quiet force that gathered matter into stars and galaxies. Gravity
• 52:54
  Speaker 1: does not only build structures. On the largest scales, the
• 52:58
  Speaker 1: combined gravity of matter is also works against the expansion
• 53:02
  Speaker 1: of the universe. In the young cosmos, matter was much
• 53:06
  Speaker 1: more concentrated. Galaxies were closer together. The universe was denser.
• 53:12
  Speaker 1: And gravity had more matter to work with. So, although
• 53:16
  Speaker 1: space was expanding, gravity gradually resisted that expansion. For a
• 53:21
  Speaker 1: very long time, the story seemed almost simple. The universe
• 53:25
  Speaker 1: began expanding. Gravity pulled against that expansion. The expansion should
• 53:31
  Speaker 1: gradually slow, and for billions of years, that was roughly
• 53:35
  Speaker 1: what happened. But the universe had another quiet ingredient, something
• 53:40
  Speaker 1: that did not behave in the familiar way, something we
• 53:43
  Speaker 1: still do not fully understand. Today, you can simply call
• 53:47
  Speaker 1: it dark energy. The name is enough. You do not
• 53:51
  Speaker 1: need to imagine a substance floating through space. You do
• 53:55
  Speaker 1: not need to imagine a mysterious wind pushing galaxies outward.
• 53:59
  Speaker 1: Scientists use the term because something associated with the large-scale
• 54:03
  Speaker 1: behaviour of the universe appears to be driving its expansion
• 54:07
  Speaker 1: to accelerate. And the discovery of this acceleration came from
• 54:11
  Speaker 1: looking very carefully at distant light. Imagine yourself drifting among
• 54:16
  Speaker 1: the galaxies again. You see their faint light arriving from
• 54:19
  Speaker 1: across enormous distances. Some of the light has travelled for
• 54:23
  Speaker 1: billions of years. Its wavelengths have been stretched by the
• 54:27
  Speaker 1: expanding universe. This stretching gives astronomers a way to measure
• 54:32
  Speaker 1: how much the universe has expanded along the light's journey.
• 54:36
  Speaker 1: But measuring distance across the cosmos is not easy. A
• 54:40
  Speaker 1: galaxy can be brighter than another galaxy, or dimmer. Its
• 54:44
  Speaker 1: size can be different. Its stars can be different. So
• 54:48
  Speaker 1: astronomers needed something whose brightness could be estimated with greater consistency.
• 54:54
  Speaker 1: One useful object was a particular kind of stellar explosion
• 54:58
  Speaker 1: called a Type Ia supernova. You can think of it
• 55:01
  Speaker 1: simply as a very bright cosmic beacon. These explosions can
• 55:06
  Speaker 1: become extraordinarily luminous, bright enough to be seen across immense distances.
• 55:12
  Speaker 1: Because their intrinsic brightness follows a relatively consistent pattern, astronomers
• 55:17
  Speaker 1: can compare how bright they actually appear with how bright
• 55:20
  Speaker 1: they are expected to be. If something that should look
• 55:23
  Speaker 1: bright appears very faint, it is likely farther away. And
• 55:28
  Speaker 1: by combining this distance information with the stretching of its light,
• 55:32
  Speaker 1: scientists can reconstruct how the universe has expanded over time.
• 55:37
  Speaker 1: It was a quiet measurement, a distant point of light,
• 55:41
  Speaker 1: a faint signal, a careful comparison, and yet the result
• 55:46
  Speaker 1: changed our picture of the cosmos. The most distant supernovae
• 55:51
  Speaker 1: appeared to be farther away than expected if the universe
• 55:54
  Speaker 1: had simply been slowing its expansion under gravity. Something had changed.
• 56:00
  Speaker 1: The expansion had not merely continued. It had begun accelerating.
• 56:04
  Speaker 1: You can let that discovery settle gently. No explosion. No
• 56:09
  Speaker 1: sudden cosmic event. Just a gradual change in the way
• 56:13
  Speaker 1: the universe expands. And the cause remains mysterious. Scientists call
• 56:19
  Speaker 1: the unknown influence dark energy. It is important to keep
• 56:23
  Speaker 1: the idea soft. Dark energy is not simply a known
• 56:27
  Speaker 1: anti-gravity substance. We do not yet know its fundamental nature. Instead,
• 56:33
  Speaker 1: it is the name given to whatever physical ingredient is
• 56:35
  Speaker 1: responsible for the observed accelerated expansion within our current cosmological understanding.
• 56:42
  Speaker 1: There are several ideas about what it might be. Perhaps
• 56:45
  Speaker 1: it is associated with a property of space itself. Perhaps
• 56:49
  Speaker 1: our understanding of gravity needs to be modified on the
• 56:52
  Speaker 1: largest scales. Perhaps something deeper is happening. For now, the
• 56:58
  Speaker 1: mystery remains. And perhaps that uncertainty is strangely peaceful. The
• 57:04
  Speaker 1: universe does not need to reveal everything at once. You
• 57:07
  Speaker 1: can simply observe what it does. As space expands, ordinary
• 57:11
  Speaker 1: matter becomes more spread out. Imagine the same number of
• 57:15
  Speaker 1: tiny particles occupying a larger and larger region. The matter
• 57:20
  Speaker 1: becomes more dilute. The average density falls. Galaxies remain bound
• 57:25
  Speaker 1: together because their local gravity is strong enough to hold them.
• 57:28
  Speaker 1: Stars remain inside galaxies, planets remain around stars, moons remain
• 57:34
  Speaker 1: around planets, your room remains around you. The expansion of
• 57:39
  Speaker 1: the universe does not pull apart the objects that are
• 57:42
  Speaker 1: already held together by stronger local forces. Instead, the most
• 57:47
  Speaker 1: noticeable expansion occurs across the enormous spaces between distant gravitationally
• 57:52
  Speaker 1: bound structures. The great voids between galaxies become larger. The
• 57:57
  Speaker 1: distances between distant groups increase. And because the expansion is accelerating,
• 58:03
  Speaker 1: this separation continues to grow. You can imagine floating through
• 58:07
  Speaker 1: one of these enormous cosmic voids. There are galaxies far
• 58:11
  Speaker 1: behind you. A cluster of galaxies lies far ahead. Between
• 58:16
  Speaker 1: them is a vast region containing very little matter. The
• 58:20
  Speaker 1: space itself is expanding. The galaxies are becoming more separated.
• 58:25
  Speaker 1: And slowly, the light from distant places becomes more difficult
• 58:29
  Speaker 1: to receive. Not because the galaxies suddenly disappear. They continue
• 58:35
  Speaker 1: to exist, they continue to shine, but their light must
• 58:39
  Speaker 1: travel across an expanding universe. As the expansion continues, some
• 58:44
  Speaker 1: distant galaxies can eventually become unreachable by their light. Their
• 58:49
  Speaker 1: ancient signals may already be arriving less frequently, or may
• 58:53
  Speaker 1: eventually cease to reach you. The observable cosmos therefore becomes
• 58:58
  Speaker 1: connected to the history of expansion. What you can see
• 59:02
  Speaker 1: depends not only on where galaxies are, but on how
• 59:05
  Speaker 1: space between you and them has changed over time. You
• 59:09
  Speaker 1: can rest with that idea. The universe is not simply
• 59:13
  Speaker 1: becoming bigger. Its expansion is changing, and that change slowly
• 59:18
  Speaker 1: alters the relationships between galaxies. Some structures remain together, others
• 59:24
  Speaker 1: drift farther apart. The cosmic web becomes more stretched across
• 59:29
  Speaker 1: the darkness. The great voids become quieter, and the distant
• 59:33
  Speaker 1: lights become more isolated. There is no central point where
• 59:37
  Speaker 1: this begins. There is no special direction. Everywhere, on the
• 59:42
  Speaker 1: largest scales, the same expanding universe continues. From your small
• 59:47
  Speaker 1: place on Earth, you happen to see one portion of it.
• 59:51
  Speaker 1: From another galaxy, another observer would see their own surroundings
• 59:55
  Speaker 1: expanding away in much the same broad patterns. The cosmos
• 1:00:00
  Speaker 1: has no privileged centre, only countless observers, countless galaxies, and
• 1:00:06
  Speaker 1: an enormous space changing with time, and now you can
• 1:00:10
  Speaker 1: allow yourself to drift farther into the future. Not millions
• 1:00:14
  Speaker 1: of years, not even billions in the ordinary human sense,
• 1:00:18
  Speaker 1: but the deep future of the cosmos, a future in
• 1:00:22
  Speaker 1: which galaxies become increasingly separated. A future in which more
• 1:00:26
  Speaker 1: distant lights slowly pass beyond the reach of observation. A
• 1:00:31
  Speaker 1: future in which the night sky becomes quieter. The universe
• 1:00:35
  Speaker 1: has already begun moving toward that distant loneliness. Not because
• 1:00:39
  Speaker 1: anything is wrong. Not because the cosmos is ending. Simply
• 1:00:44
  Speaker 1: because expansion continues. And if that expansion continues to accelerate,
• 1:00:49
  Speaker 1: the enormous spaces between the remaining islands of matter will
• 1:00:54
  Speaker 1: become more and more important. The galaxies near you will
• 1:00:57
  Speaker 1: remain for a very long time. Their stars will continue shining.
• 1:01:02
  Speaker 1: Their planets will continue orbiting. But beyond them, the darkness
• 1:01:06
  Speaker 1: will grow, very slowly, almost imperceptibly, like a room becoming
• 1:01:12
  Speaker 1: larger while the lights remain gathered in only a few corners.
• 1:01:16
  Speaker 1: You can rest here for a while. There is nothing
• 1:01:19
  Speaker 1: to solve. You are safe. The universe does not require
• 1:01:23
  Speaker 1: an answer from you, it simply expands, and as it expands,
• 1:01:28
  Speaker 1: the future becomes a little quieter, a little darker, and
• 1:01:31
  Speaker 1: a little more spacious. Far away, galaxies continue shining. Closer
• 1:01:37
  Speaker 1: to you, gravity continues holding familiar structures together, and between them,
• 1:01:43
  Speaker 1: the great emptiness continues to grow, patiently, silently, without hurry.
• 1:01:50
  Speaker 1: And somewhere in that widening darkness, the distant future of
• 1:01:53
  Speaker 1: the stars is waiting, so far away that you do
• 1:01:57
  Speaker 1: not need to reach it yet. The distant future is
• 1:02:02
  Speaker 1: waiting quietly in the darkness. You do not need to
• 1:02:06
  Speaker 1: hurry toward it. For now, the stars around you are
• 1:02:09
  Speaker 1: still shining. The Milky Way is still filled with enormous
• 1:02:13
  Speaker 1: clouds of gas, countless stars, and the slow movement of
• 1:02:18
  Speaker 1: galaxies through space. The universe is still young enough, in
• 1:02:22
  Speaker 1: the deepest sense, for light to fill much of the cosmos.
• 1:02:26
  Speaker 1: But if you allow your imagination to move forward, very gently,
• 1:02:31
  Speaker 1: across immense stretches of time, the universe begins to change.
• 1:02:35
  Speaker 1: Not suddenly, not dramatically, simply gradually. The same slow rhythm
• 1:02:41
  Speaker 1: that built the cosmos begins to work in the opposite direction.
• 1:02:45
  Speaker 1: Stars are born. Stars shine. Stars eventually use the fuel
• 1:02:50
  Speaker 1: that allows them to shine, and new stars form from
• 1:02:54
  Speaker 1: the remaining gas. For a very long time this cycle continues,
• 1:02:58
  Speaker 1: but the supply of easily available gas does not remain endless.
• 1:03:03
  Speaker 1: Over immense periods, more of it becomes locked inside stars.
• 1:03:07
  Speaker 1: Some stars die and return material to space. Some of
• 1:03:11
  Speaker 1: that material can later become part of new stars, but
• 1:03:15
  Speaker 1: the overall universe continues to change. Star formation gradually becomes
• 1:03:20
  Speaker 1: less common. The great factories of light become quieter. You
• 1:03:25
  Speaker 1: can imagine drifting through a galaxy far in the future.
• 1:03:28
  Speaker 1: It still exists. There are still stars. There is still gravity.
• 1:03:33
  Speaker 1: There are still planets and remnants of ancient stellar systems.
• 1:03:37
  Speaker 1: But the galaxy is quieter than it once was. Fewer
• 1:03:41
  Speaker 1: new stars are appearing. The brightest, youngest stars are less common.
• 1:03:46
  Speaker 1: The night between the stars feels deeper, and the universe
• 1:03:50
  Speaker 1: beyond the galaxy is becoming even more distant. Remember the
• 1:03:54
  Speaker 1: expanding space you imagined earlier. That expansion does not stop
• 1:03:58
  Speaker 1: simply because stars become old. On the largest scales, distant
• 1:04:03
  Speaker 1: galaxies continue moving away from one another as space expands.
• 1:04:08
  Speaker 1: Some nearby galaxies, however, are close enough for gravity to
• 1:04:12
  Speaker 1: overcome that expansion. The Milky Way belongs to a gravitationally
• 1:04:16
  Speaker 1: bound neighbourhood, and one of the largest nearby galaxies, Andromeda,
• 1:04:22
  Speaker 1: is expected to merge with the Milky Way over the
• 1:04:25
  Speaker 1: distant future. You can imagine these two enormous galaxies approaching
• 1:04:29
  Speaker 1: one another. There is no sound, no sudden impact, no explosion.
• 1:04:35
  Speaker 1: Their stars are separated by such enormous distances that individual
• 1:04:39
  Speaker 1: stars are unlikely to simply crash into one another. Instead,
• 1:04:44
  Speaker 1: Gravity slowly changes their paths. The shapes of the galaxies
• 1:04:48
  Speaker 1: become distorted. Their spiral structures can be rearranged. Their stars
• 1:04:53
  Speaker 1: follow new orbits. Gas clouds interact. And over a very
• 1:04:58
  Speaker 1: long period, the two galaxies can settle into one larger galaxy.
• 1:05:03
  Speaker 1: A new stellar home formed from two ancient ones. The
• 1:05:08
  Speaker 1: universe continues. But outside this merged galaxy... Distant structures are
• 1:05:13
  Speaker 1: becoming harder and harder to see. Expansion gradually increases the
• 1:05:18
  Speaker 1: separation between gravitationally unbound galaxies. Light from some distant regions
• 1:05:24
  Speaker 1: becomes increasingly difficult to receive. Eventually, many galaxies that are
• 1:05:30
  Speaker 1: visible to a future observer today would lie beyond that
• 1:05:34
  Speaker 1: observer's accessible horizon. The sky would contain fewer visible islands
• 1:05:39
  Speaker 1: of light. The universe would feel increasingly lonely. But loneliness
• 1:05:43
  Speaker 1: is not the same as emptiness. There would still be stars.
• 1:05:47
  Speaker 1: There would still be planets. There would still be the
• 1:05:50
  Speaker 1: remnants of ancient stars. There would still be matter. There
• 1:05:54
  Speaker 1: would still be gravity. The quietness would simply grow. And then,
• 1:05:59
  Speaker 1: over much longer periods, the stars themselves would slowly disappear.
• 1:06:04
  Speaker 1: The most massive stars have shorter lives. Smaller stars can
• 1:06:09
  Speaker 1: shine for extraordinarily long periods. Some of the smallest stars
• 1:06:13
  Speaker 1: can continue producing light for vastly longer than stars like
• 1:06:17
  Speaker 1: our Sun, but even these long-lived stars are not eternal. Eventually,
• 1:06:23
  Speaker 1: star formation becomes rare enough that the universe enters an
• 1:06:27
  Speaker 1: increasingly dark era. You can imagine yourself drifting through that
• 1:06:32
  Speaker 1: future cosmos. There is almost no new light being created.
• 1:06:37
  Speaker 1: The stars that remain are old. Some are faint, Some
• 1:06:41
  Speaker 1: have become stellar remnants. White dwarfs remain as cooling embers
• 1:06:45
  Speaker 1: of former stars. Neutron stars remain as incredibly dense remnants
• 1:06:50
  Speaker 1: of stellar deaths. Black holes remain where some massive stars
• 1:06:54
  Speaker 1: and other processes have left behind regions of extreme gravity.
• 1:06:59
  Speaker 1: And the galaxies themselves become collections of increasingly old objects.
• 1:07:04
  Speaker 1: The universe is still there, still expanding, still carrying matter
• 1:07:09
  Speaker 1: through space. but its sources of fresh light have become scarce.
• 1:07:13
  Speaker 1: This is sometimes described as the beginning of a cosmic
• 1:07:16
  Speaker 1: dark age. The phrase can sound frightening, but there is
• 1:07:20
  Speaker 1: nothing frightening that needs to happen. There is no final explosion,
• 1:07:25
  Speaker 1: no great cosmic curtain, no sudden moment when everything stops.
• 1:07:30
  Speaker 1: The universe simply approaches a state in which there are
• 1:07:33
  Speaker 1: fewer useful differences in temperature and energy. And this brings
• 1:07:38
  Speaker 1: you toward one of the deepest ideas about the far
• 1:07:41
  Speaker 1: future of the cosmos. Heat death. The phrase sounds much
• 1:07:45
  Speaker 1: more dramatic than the physical idea itself. Heat death does
• 1:07:50
  Speaker 1: not mean that everything becomes intensely hot. It means almost
• 1:07:54
  Speaker 1: the opposite. It describes a universe that approaches a state
• 1:07:58
  Speaker 1: of thermodynamic equilibrium, where energy has become so evenly distributed
• 1:08:03
  Speaker 1: that that there are fewer differences available to drive large-scale processes.
• 1:08:09
  Speaker 1: You can imagine a warm object placed inside a cooler room.
• 1:08:14
  Speaker 1: At first, there is a difference. Heat flows. The difference
• 1:08:18
  Speaker 1: allows something to happen. Eventually, the object and its surroundings
• 1:08:22
  Speaker 1: approach the same temperature. The flow becomes smaller. The difference fades.
• 1:08:28
  Speaker 1: In the far future of the universe, The same broad
• 1:08:31
  Speaker 1: principle applies on an immense cosmic scale. Energy becomes increasingly
• 1:08:36
  Speaker 1: spread out. Temperature differences become smaller. There are fewer concentrated
• 1:08:41
  Speaker 1: sources of usable energy. The universe approaches a state that
• 1:08:46
  Speaker 1: is extraordinarily quiet. But even this idea should not be
• 1:08:50
  Speaker 1: imagined as an exact appointment on a cosmic calendar. The
• 1:08:54
  Speaker 1: distant future depends on the long-term behaviour of the universe.
• 1:08:58
  Speaker 1: And the nature of dark energy remains one of the
• 1:09:01
  Speaker 1: great unanswered questions in cosmology. Scientists have strong evidence that
• 1:09:06
  Speaker 1: cosmic expansion is accelerating, but the deeper nature of whatever
• 1:09:10
  Speaker 1: causes that acceleration is not yet completely understood. Recent observations
• 1:09:16
  Speaker 1: have even raised the possibility that dark energy may change
• 1:09:19
  Speaker 1: with time, although those hints are not yet a settled conclusion.
• 1:09:24
  Speaker 1: So the very far future remains partly uncertain, and perhaps
• 1:09:28
  Speaker 1: that uncertainty belongs here. You do not need to imagine
• 1:09:32
  Speaker 1: one fixed ending carved into the fabric of reality. You
• 1:09:35
  Speaker 1: can simply imagine a direction, more expansion, more separation, fewer
• 1:09:41
  Speaker 1: new stars, older stars. fainter light, more space, more quiet,
• 1:09:48
  Speaker 1: and eventually a universe in which the great differences that
• 1:09:51
  Speaker 1: once created stars, galaxies, and glowing clouds have become increasingly small.
• 1:09:58
  Speaker 1: You can let that image become softer now. The universe
• 1:10:01
  Speaker 1: that once held an incredibly hot, dense beginning has spent
• 1:10:05
  Speaker 1: billions of years expanding. It formed particles, then atoms, then stars,
• 1:10:12
  Speaker 1: then galaxies. then clusters, then the enormous cosmic web. It
• 1:10:18
  Speaker 1: created places where light could shine for billions of years.
• 1:10:22
  Speaker 1: And now, in the distant future, that same universe slowly
• 1:10:26
  Speaker 1: moves toward greater spaciousness. You are lying here now, beneath
• 1:10:31
  Speaker 1: a small patch of its present sky. The stars you
• 1:10:34
  Speaker 1: know are still burning. The Milky Way is still alive
• 1:10:38
  Speaker 1: with motion. The universe is still full of light. There
• 1:10:43
  Speaker 1: is no need to leave the present. You can simply
• 1:10:46
  Speaker 1: notice how temporary this particular arrangement is. The stars above
• 1:10:50
  Speaker 1: you will not always look the same. The galaxies will
• 1:10:53
  Speaker 1: not always remain where they are. The cosmic web will
• 1:10:56
  Speaker 1: continue to stretch. The darkness will gradually become more dominant.
• 1:11:01
  Speaker 1: And yet, tonight, the light is still here. You can
• 1:11:05
  Speaker 1: hear the quiet sounds around you. You can feel the
• 1:11:08
  Speaker 1: weight of your body resting beneath you. You can breathe slowly.
• 1:11:12
  Speaker 1: There is nothing to solve. You are safe. The universe
• 1:11:16
  Speaker 1: has been changing for billions of years, without needing anyone
• 1:11:20
  Speaker 1: to guide it. And it will continue changing long after
• 1:11:24
  Speaker 1: this moment has passed. Perhaps that is the gentlest thought
• 1:11:27
  Speaker 1: of all. You do not need to carry the universe.
• 1:11:31
  Speaker 1: You only need to rest beneath it. The stars can
• 1:11:34
  Speaker 1: keep burning. The galaxies can keep turning. Space can keep expanding.
• 1:11:40
  Speaker 1: and somewhere beyond the edge of what you can see,
• 1:11:43
  Speaker 1: the long future continues unfolding, quietly, patiently, almost without sound.
• 1:11:50
  Speaker 1: For now, you can let the distant cosmos become a
• 1:11:53
  Speaker 1: soft background to your breathing, a little more darkness, a
• 1:11:57
  Speaker 1: little more space, a little more silence, and as you drift,
• 1:12:01
  Speaker 1: the universe keeps going, slowly becoming quieter, while you remain here,
• 1:12:07
  Speaker 1: resting beneath its ancient light. And so, our journey quietly
• 1:12:14
  Speaker 1: comes to an end. You have travelled from the small
• 1:12:17
  Speaker 1: world beneath you, across galaxies, through ancient light, and into
• 1:12:23
  Speaker 1: the vast future of the universe. But now, there is
• 1:12:27
  Speaker 1: nothing left to follow. You are safe. There is nothing
• 1:12:31
  Speaker 1: to do. Just breathe slowly. Let the darkness become softer,
• 1:12:35
  Speaker 1: and allow yourself to rest. The stars can keep burning.
• 1:12:40
  Speaker 1: The galaxies can keep drifting. and the universe can keep
• 1:12:43
  Speaker 1: expanding while you sleep. For now, simply close your eyes,
• 1:12:49
  Speaker 1: let go of the distant cosmos, and drift gently into
• 1:12:52
  Speaker 1: the quiet of the night.