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The Universe Has an Edge... But It Isn_t Where You Think · Boring Science

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  Speaker 1: Hello, and welcome to Boring Science to Sleep, a quiet
• 0:04
  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 paradox of an infinite universe.
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  Speaker 1: Not to learn everything, and not to find a final answer,
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  Speaker 1: but simply to notice the strange shape of space, slowly, calmly,
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  Speaker 1: one thought at a time. Before you settle in, If
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  Speaker 1: you truly enjoy these calm journeys through interesting facts about science,
• 0:31
  Speaker 1: you're welcome to like this video and subscribe, but only
• 0:34
  Speaker 1: if it feels right for you. And when you're ready,
• 0:38
  Speaker 1: let me know in the comments where you're listening from,
• 0:41
  Speaker 1: and what time it is right now. It's always a
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  Speaker 1: quiet joy to see how many places and moments gather
• 0:47
  Speaker 1: here together. Now, dim the lights, perhaps let a fan
• 0:51
  Speaker 1: hum softly in the background. Allow your body to become
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  Speaker 1: a little heavier against the bed and let your attention loosen.
• 0:59
  Speaker 1: There is nothing to do. You are safe. You can
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  Speaker 1: simply listen and drift as we slowly step into the
• 1:05
  Speaker 1: vast darkness beyond the familiar sky. For a moment, imagine
• 1:10
  Speaker 1: that you are lying somewhere quiet beneath the night sky.
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  Speaker 1: Perhaps the room around you is already dark, with only
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  Speaker 1: a little light coming through a curtain. Perhaps there is
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  Speaker 1: a soft hum somewhere nearby. Perhaps you can hear the
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  Speaker 1: almost invisible sounds of a building settling into the night.
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  Speaker 1: You do not have to move. You do not have
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  Speaker 1: to understand anything. Just let your attention rise slowly, as
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  Speaker 1: if you were looking through the ceiling, through the roof,
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  Speaker 1: through the quiet layers of air above you, until the
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  Speaker 1: familiar world begins to disappear and the sky opens gently
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  Speaker 1: above your thoughts. At first, there is the moon, perhaps.
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  Speaker 1: and the nearby stars. Then there are more stars, and
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  Speaker 1: beyond those stars there are galaxies, and beyond those galaxies
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  Speaker 1: there is more darkness, more distance, more ancient light. You
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  Speaker 1: might imagine that if you simply kept looking farther and farther,
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  Speaker 1: eventually you would reach the very edge of the universe.
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  Speaker 1: It sounds reasonable. After all, if the universe has existed
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  Speaker 1: for a finite amount of time, and if light needs
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  Speaker 1: time to travel, then perhaps there must be some place
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  Speaker 1: where the view simply stops. And in one very particular sense,
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  Speaker 1: there is. But it is not quite the kind of
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  Speaker 1: edge you might imagine. There is no cosmic wall waiting
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  Speaker 1: at the end of space. No enormous surface standing silently
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  Speaker 1: in the darkness. No final boundary that says, beyond this point,
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  Speaker 1: nothing exists. Instead, the edge comes from something much quieter.
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  Speaker 1: Light takes time. Every photon, every tiny packet of light
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  Speaker 1: arriving from the night sky has been travelling toward you.
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  Speaker 1: Some light has travelled for a few seconds. Some has
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  Speaker 1: travelled for years. Some has travelled for millions of years.
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  Speaker 1: And some of the oldest light you can receive has
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  Speaker 1: been travelling across the changing universe for almost the entire
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  Speaker 1: history of the cosmos. There is a simple rule beneath
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  Speaker 1: all of this. Information cannot arrive faster than light. So
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  Speaker 1: when you look into space, you are not seeing everything
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  Speaker 1: that exists. You are seeing everything whose light has had
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  Speaker 1: enough time to reach you. That creates a kind of
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  Speaker 1: invisible horizon around you. It is not a horizon like
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  Speaker 1: the horizon at sea, where the surface of the earth
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  Speaker 1: eventually hides distant ships. It is a horizon made from time.
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  Speaker 1: Imagine that every moment in cosmic history sends out an
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  Speaker 1: enormous number of quiet messengers, travelling outward through space. Some
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  Speaker 1: of those messengers eventually reach you. Others have not arrived yet.
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  Speaker 1: And some may never reach you at all. So, when
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  Speaker 1: you look in one direction, and then another, and then another,
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  Speaker 1: your view gradually reaches farther back into the history of
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  Speaker 1: the universe. You are not simply looking farther away. You
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  Speaker 1: are looking farther into the past. The farther away a
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  Speaker 1: galaxy is, the longer its light has been travelling before
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  Speaker 1: arriving at your eyes. This means that the distant universe
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  Speaker 1: is also an ancient universe. A galaxy appearing as a tiny,
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  Speaker 1: faint point may actually be showing you what it looked
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  Speaker 1: like billions of years ago, when the Earth itself was
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  Speaker 1: very different, when our planet was still passing through long
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  Speaker 1: chapters of its own history. And if you keep looking farther,
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  Speaker 1: The distinction between distance and time becomes softer and softer.
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  Speaker 1: You are looking across space, but you are also looking
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  Speaker 1: backward through time. There is something beautiful about that, because
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  Speaker 1: the universe does not give you a single picture of itself.
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  Speaker 1: It gives you layers. Nearby stars appear closer to the present.
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  Speaker 1: More distant galaxies show older moments. And farther still, the
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  Speaker 1: light carries information from a universe that was younger, warmer,
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  Speaker 1: and very different from the quiet cosmos you know now. Eventually,
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  Speaker 1: your view reaches a remarkable distance. The most distant regions
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  Speaker 1: whose ancient light can reach us today are now roughly
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  Speaker 1: 45 billion light-years away. A light-year is simply the distance
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  Speaker 1: light can travel in one year. And so, 45 billion
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  Speaker 1: light-years is not a number that you need to picture.
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  Speaker 1: You do not need to count it. You do not
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  Speaker 1: need to imagine crossing it. It is enough to let
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  Speaker 1: the number become a feeling of distance so large that
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  Speaker 1: ordinary human scale quietly disappears. From your position, this observable
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  Speaker 1: region extends in every direction. It forms something like a
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  Speaker 1: vast sphere around you, not because you are physically located
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  Speaker 1: at the centre of the entire universe, but because you
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  Speaker 1: are the observer standing at the centre of your own
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  Speaker 1: visible region. Someone in another galaxy exists would have their
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  Speaker 1: own observable region, they too would stand at the centre
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  Speaker 1: of what they could see. So your cosmic horizon is
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  Speaker 1: personal in a very gentle sense. It marks the boundary
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  Speaker 1: of information that has reached you. And this is where
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  Speaker 1: the first great paradox appears. The observable universe has a boundary,
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  Speaker 1: but that does not mean the universe itself has a boundary.
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  Speaker 1: You can reach the edge of what you can see
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  Speaker 1: without reaching the edge of what exists. The distinction is
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  Speaker 1: small in words, but enormous in meaning. The visible universe
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  Speaker 1: is finite because the universe has had a limited amount
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  Speaker 1: of time to send light toward you. Space itself may
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  Speaker 1: continue beyond that visible region. There may be galaxies beyond
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  Speaker 1: your horizon. There may be stars beyond those galaxies. There
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  Speaker 1: may be regions of space whose light is still traveling
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  Speaker 1: toward you. slowly crossing distances that are almost impossible to imagine.
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  Speaker 1: And there may be regions whose light will never arrive,
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  Speaker 1: not because there is a wall there, not because space
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  Speaker 1: suddenly stops, simply because the cosmic distances involved, together with
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  Speaker 1: the continuing expansion of space, can place some regions permanently
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  Speaker 1: beyond your ability to receive their information. So the edge
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  Speaker 1: you see is not really an edge in space, it
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  Speaker 1: is an edge in time. It is the point beyond
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  Speaker 1: which there is no older light currently arriving at you
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  Speaker 1: from farther away. You are looking backward until there is
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  Speaker 1: simply no further past that can be seen. And for tonight,
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  Speaker 1: that is enough. You can let that thought become quiet.
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  Speaker 1: You are lying here on earth, beneath a sky filled
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  Speaker 1: with ancient light. Some of that light began its journey
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  Speaker 1: before human beings existed. Some began its journey before our
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  Speaker 1: species existed. Some began its journey when Earth itself was
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  Speaker 1: still very young. And after travelling through an expanding universe
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  Speaker 1: for unimaginable spans of time, a tiny part of that
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  Speaker 1: ancient light arrives here, quietly, almost unnoticed, and becomes part
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  Speaker 1: of what you can see. The darkness between the stars
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  Speaker 1: is not an empty wall. It is a horizon made
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  Speaker 1: from time. And beyond that horizon, there may still be
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  Speaker 1: more universe waiting in the darkness. unseen not because it
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  Speaker 1: is absent, but simply because its story has not reached you.
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  Speaker 1: For a little while longer, you can remain beneath that
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  Speaker 1: enormous sky, without needing to decide what the darkness means.
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  Speaker 1: You have already travelled as far as light allows you
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  Speaker 1: to see, not by moving through space, but simply by
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  Speaker 1: looking outward, receiving ancient messages and that have crossed the
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  Speaker 1: universe for billions of years. And now, very gently, you
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  Speaker 1: can allow yourself to wonder about something just beyond that horizon.
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  Speaker 1: What might be there? The simplest answer is also the
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  Speaker 1: most difficult to picture. There may simply be more universe,
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  Speaker 1: more space, more galaxies, more stars, more distances unfolding in
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  Speaker 1: directions that you cannot currently see. The fact that you
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  Speaker 1: cannot receive light from a region does not mean that
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  Speaker 1: the region is empty. It only means that its information
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  Speaker 1: has not reached you. You can think of yourself standing
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  Speaker 1: quietly in darkness with a small lantern. The lantern illuminates
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  Speaker 1: a little circle around you. Beyond the circle, you cannot
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  Speaker 1: see the ground. You cannot see the trees. You cannot
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  Speaker 1: see how far the landscape continues. But the darkness beyond
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  Speaker 1: the lantern does not tell you that the landscape ends there.
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  Speaker 1: It only tells you where your light stops being useful.
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  Speaker 1: The observable universe is a little like that, although the
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  Speaker 1: real cosmic horizon is much stranger. Your lantern is light itself,
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  Speaker 1: and the darkness beyond it is not necessarily emptiness. It
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  Speaker 1: is simply the part of the universe from which information
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  Speaker 1: has not reached you yet, or may never reach you.
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  Speaker 1: This distinction is important, because the observable universe is not
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  Speaker 1: automatically the same thing as the entire universe. When you
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  Speaker 1: hear the phrase, the observable universe, it can sound as
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  Speaker 1: though scientists have placed a boundary around everything that exists.
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  Speaker 1: But the word observable is doing most of the work.
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  Speaker 1: It means what you can observe. It does not mean
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  Speaker 1: everything that exists. Your view is limited by the age
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  Speaker 1: of the universe, by the travel time of light, and
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  Speaker 1: by the changing distances between regions of space. So there
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  Speaker 1: could be an enormous amount of reality beyond the region
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  Speaker 1: that can currently send information to you. Perhaps the total
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  Speaker 1: universe is only somewhat larger than what you can observe.
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  Speaker 1: Perhaps it is vastly larger. Perhaps it is finite. but
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  Speaker 1: arranged in a way that gives it no boundary, or
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  Speaker 1: perhaps it continues forever. For now, you can leave all
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  Speaker 1: four possibilities resting quietly in the darkness. There is no
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  Speaker 1: need to choose one. There is another gentle idea worth
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  Speaker 1: keeping in mind. You are not at the physical centre
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  Speaker 1: of the universe simply because your observable universe surrounds you.
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  Speaker 1: Every observer has their own horizon. Imagine another listener, somewhere
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  Speaker 1: on a planet, orbiting a distant star, perhaps billions of
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  Speaker 1: light years away. That listener looks outward into space. Their
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  Speaker 1: observable region surrounds them too. They have their own cosmic horizon.
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  Speaker 1: From their point of view, they are at the centre
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  Speaker 1: of what they can see. And from your point of view,
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  Speaker 1: you are at the centre of what you can see.
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  Speaker 1: This does not mean that both of you occupy some
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  Speaker 1: special central location in the entire universe. It simply means
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  Speaker 1: that every observer receives light from their own surrounding region.
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  Speaker 1: Every observer carries their own little window into cosmic history.
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  Speaker 1: Your window happens to be centred on you. Another window
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  Speaker 1: would be centred somewhere else. And the two windows would
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  Speaker 1: overlap in some places, while extending into different regions in others.
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  Speaker 1: You can let that picture become very quiet. Millions, perhaps
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  Speaker 1: billions of observers... each surrounded by their own observable horizon,
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  Speaker 1: each receiving ancient light from different directions, each looking into
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  Speaker 1: a portion of a much larger cosmos. No single observer
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  Speaker 1: necessarily sees the whole thing. And perhaps no observer ever could.
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  Speaker 1: Because even if you had a spacecraft capable of travelling
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  Speaker 1: for an extraordinary amount of time, the observable horizon is
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  Speaker 1: not simply a distant wall waiting for you to catch
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  Speaker 1: up with it. As you move, your relationship to the
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  Speaker 1: surrounding universe changes. New light can eventually enter your view.
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  Speaker 1: Other regions can remain beyond it. And because space itself
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  Speaker 1: is expanding, the story becomes even more subtle. Some very
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  Speaker 1: distant regions may be carried away from us in such
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  Speaker 1: a way that their light can never complete the journey
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  Speaker 1: to us. So there is a difference between something being
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  Speaker 1: far away and something being permanently beyond communication. The universe
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  Speaker 1: can contain places that are not merely distant, but causally
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  Speaker 1: disconnected from us. You do not need to hold on
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  Speaker 1: to the details. Just keep the gentle image. You are here.
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  Speaker 1: Light reaches you from a vast sphere around you. Beyond
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  Speaker 1: that sphere, space may continue, and beyond that, perhaps more space.
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  Speaker 1: There is no reason that the edge of your vision
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  Speaker 1: must be the edge of existence. In fact … This
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  Speaker 1: is where the old human idea of an edge begins
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  Speaker 1: to become difficult. If the universe has an edge, you
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  Speaker 1: might naturally ask what lies on the other side. If
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  Speaker 1: there is a wall, what is the wall standing in?
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  Speaker 1: If there is a boundary, what is beyond the boundary?
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  Speaker 1: If there is an outside, then the universe would seem
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  Speaker 1: to be inside something larger, and then that larger thing
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  Speaker 1: would raise the same question. What is outside that, and
• 14:34
  Speaker 1: what is outside that? The question can continue indefinitely, like
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  Speaker 1: a thought slowly unfolding into another thought. But perhaps the
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  Speaker 1: difficulty comes from using familiar words for something that may
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  Speaker 1: not behave like familiar objects. A house has an outside
• 14:51
  Speaker 1: because the house occupies part of a larger space. A
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  Speaker 1: planet has an outside because the planet exists within space.
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  Speaker 1: A star has an outside because there is space around it.
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  Speaker 1: But if the universe means all of space, all of
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  Speaker 1: the places in which things can exist, then asking what
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  Speaker 1: is outside it may not describe an ordinary location at all.
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  Speaker 1: There may be no larger room surrounding the cosmos. There
• 15:18
  Speaker 1: may be no dark container holding the universe. And there
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  Speaker 1: may be no meaningful direction called outside. This is one
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  Speaker 1: of those questions where language begins to become softer than usual.
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  Speaker 1: You can ask where the universe ends. But the word
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  Speaker 1: where already assumes there is somewhere beyond the thing you
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  Speaker 1: are describing. You can ask what lies outside everything, but
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  Speaker 1: the word outside already assumes there is an even larger space.
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  Speaker 1: Perhaps the universe does not require such a place. Perhaps
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  Speaker 1: space simply has the shape that it has, and perhaps
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  Speaker 1: that shape can be finite without having a border. For now,
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  Speaker 1: you can leave that possibility resting quietly. The observable universe
• 16:04
  Speaker 1: surrounds you. Beyond your horizon there may be more. You
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  Speaker 1: cannot see it, but you do not need to. The
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  Speaker 1: darkness does not have to be an ending. It can
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  Speaker 1: simply be the place where your information has not arrived,
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  Speaker 1: and as you rest here, beneath a small patch of sky,
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  Speaker 1: you can allow the horizon to become what it really is.
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  Speaker 1: Not a wall around existence, but a quiet boundary. around
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  Speaker 1: what has reached you so far. Far beyond it, space
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  Speaker 1: may continue in ways you cannot yet see, and perhaps,
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  Speaker 1: if space itself has a shape that you have never imagined,
• 16:42
  Speaker 1: even the idea of an edge may eventually begin to
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  Speaker 1: mean something very different. For a little while, you can
• 16:52
  Speaker 1: let the idea of the horizon become softer. You have
• 16:55
  Speaker 1: imagined the visible universe surrounding you. A vast region defined
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  Speaker 1: not by a wall, but by the simple fact that
• 17:03
  Speaker 1: light needs time to travel. And beyond that visible region,
• 17:08
  Speaker 1: there may be more. More space, more galaxies, more darkness,
• 17:13
  Speaker 1: more ancient light, continuing quietly beyond the reach of your
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  Speaker 1: present view. But there is another possibility, one that seems
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  Speaker 1: almost contradictory at first. What if the universe is finite?
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  Speaker 1: What if there is only a certain total amount of space?
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  Speaker 1: At first, that sounds as though there must be an edge.
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  Speaker 1: If there is a limited amount of something, you naturally
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  Speaker 1: imagine a final point, a boundary, a place where you
• 17:39
  Speaker 1: could stop and say, this is where it ends. You
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  Speaker 1: can see this with almost everything around you. A room
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  Speaker 1: has walls. A piece of paper has edges. A planet
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  Speaker 1: has a surface that eventually gives way to the space
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  Speaker 1: around it. Even the horizon you see on Earth seems
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  Speaker 1: to suggest that there must be some boundary somewhere beyond
• 18:01
  Speaker 1: your view. But those examples all share something important. They
• 18:06
  Speaker 1: exist inside something larger. Your room sits inside a building.
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  Speaker 1: The building sits on the Earth. The Earth sits inside space.
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  Speaker 1: So when you ask what lies beyond them, there is
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  Speaker 1: always somewhere else to point. But imagine that you are
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  Speaker 1: talking about the whole of space itself. There is no
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  Speaker 1: larger room waiting around it. There is no cosmic container
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  Speaker 1: that the universe has been placed inside. And that creates
• 18:33
  Speaker 1: a strange question. If the universe were finite, where would
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  Speaker 1: its edge actually be? And what would it mean to
• 18:40
  Speaker 1: stand on the other side? You can let that question
• 18:43
  Speaker 1: rest for a moment. Then imagine something much simpler. Imagine
• 18:48
  Speaker 1: an orange. Not the orange floating in space, but only
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  Speaker 1: its outer surface. Imagine that you are a tiny creature
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  Speaker 1: living on that surface, able to move in any direction
• 18:59
  Speaker 1: across it, but unable to leave the surface. You begin walking,
• 19:04
  Speaker 1: you walk forward, and you keep walking. You never reach
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  Speaker 1: an edge. There is no cliff, there is no final
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  Speaker 1: line where the surface suddenly disappears. You simply continue. Eventually,
• 19:18
  Speaker 1: if you keep following the curved surface long enough, you
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  Speaker 1: can return to the place where you began. The surface
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  Speaker 1: is finite, it has a definite size, and yet it
• 19:28
  Speaker 1: has no boundary. This is difficult to imagine only because
• 19:32
  Speaker 1: you are used to thinking about space from the inside
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  Speaker 1: of three dimensions. But the basic idea is surprisingly simple.
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  Speaker 1: Something can have a limited total extent without having an edge.
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  Speaker 1: The surface of the orange gives you a gentle way
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  Speaker 1: to picture this. Now, imagine that space itself could have
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  Speaker 1: a similar kind of property. Instead of being a flat,
• 19:55
  Speaker 1: endless-looking stage, perhaps the three dimensions of space could curve
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  Speaker 1: in such a way that they eventually connect back to themselves.
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  Speaker 1: Scientists can describe one possibility using the word hypersphere. You
• 20:10
  Speaker 1: do not need to remember the word. The softer idea
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  Speaker 1: is enough. A hypersphere, in this sense, is a three-dimensional
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  Speaker 1: space that curves back into itself. There is no wall
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  Speaker 1: surrounding it. There is no place where you suddenly fall
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  Speaker 1: into something outside. There is simply a particular geometry of space.
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  Speaker 1: And because the space is closed, a journey that always
• 20:33
  Speaker 1: seems to move forward could, in principle, eventually bring you
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  Speaker 1: back toward where you started. Imagine yourself inside a quiet spacecraft.
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  Speaker 1: You leave Earth. The planet becomes smaller behind you. The
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  Speaker 1: stars remain ahead. You choose one direction and begin travelling.
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  Speaker 1: You do not turn around. You do not make a U-turn.
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  Speaker 1: You do not change your destination. You simply continue forward.
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  Speaker 1: At first, everything looks ordinary. Stars pass slowly. Galaxies remain
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  Speaker 1: scattered across the darkness. There is no sign telling you
• 21:10
  Speaker 1: that space is curved. There is no visible boundary. Nothing
• 21:14
  Speaker 1: feels unusual. But if the geometry of the universe were
• 21:18
  Speaker 1: closed in this particular way, the path through space could
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  Speaker 1: eventually bend back toward its starting point. After an extraordinarily
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  Speaker 1: long journey, Earth might appear ahead of you again. You
• 21:31
  Speaker 1: would not have turned around. Space would simply have connected
• 21:34
  Speaker 1: your path back to home. This is one of the
• 21:37
  Speaker 1: quietest strange ideas in cosmology. A universe could have a
• 21:42
  Speaker 1: finite amount of space while giving you no edge to discover.
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  Speaker 1: You could keep moving without ever finding a final wall.
• 21:50
  Speaker 1: You could keep travelling without ever reaching an outside. And eventually,
• 21:55
  Speaker 1: in principle, the shape of space itself could bring you back.
• 22:00
  Speaker 1: The important word here is shape. You are not imagining
• 22:03
  Speaker 1: the universe as a giant orange floating inside some larger
• 22:08
  Speaker 1: black room. The orange is only helping you imagine the geometry.
• 22:13
  Speaker 1: In the real idea, there is no requirement for the
• 22:16
  Speaker 1: universe to be sitting inside anything larger. The curvature belongs
• 22:20
  Speaker 1: to space itself, and this connects gently with one of
• 22:23
  Speaker 1: the deepest ideas in modern physics. Gravity is not simply
• 22:28
  Speaker 1: a mysterious force pulling objects through an otherwise perfectly rigid stage.
• 22:33
  Speaker 1: Matter and energy affect the geometry of space-time. The presence
• 22:37
  Speaker 1: of matter can change the way distances and paths behave.
• 22:42
  Speaker 1: You can think of this very softly, as the universe
• 22:45
  Speaker 1: having a kind of geometry that is not completely fixed
• 22:48
  Speaker 1: and rigid. Stars, planets, galaxies and everything else exist within
• 22:53
  Speaker 1: that geometry, while also influencing it. On the scale of
• 22:58
  Speaker 1: the entire cosmos, the geometry could therefore, in principle, have
• 23:03
  Speaker 1: a global shape. It could be flat, it could be curved,
• 23:08
  Speaker 1: or it could have a more complicated way of connecting
• 23:10
  Speaker 1: different regions together. And this is where the idea of
• 23:14
  Speaker 1: a finite universe without an edge becomes less like a
• 23:18
  Speaker 1: paradox and more like a possibility. You do not need
• 23:22
  Speaker 1: a border for something to be finite. You only need
• 23:26
  Speaker 1: a particular kind of geometry. The orange surface gives you
• 23:29
  Speaker 1: the simplest intuition. The spacecraft gives you another. You travel forward.
• 23:35
  Speaker 1: You see no wall. You see no sign that space
• 23:38
  Speaker 1: is ending. You simply continue along the shape of space.
• 23:42
  Speaker 1: And if the universe is closed in this particular way,
• 23:45
  Speaker 1: the path itself can eventually lead home. For now, though,
• 23:50
  Speaker 1: there is no need to decide whether this is how
• 23:52
  Speaker 1: our universe actually works. We can simply notice that the
• 23:57
  Speaker 1: word finite does not always have to mean bordered. A
• 24:01
  Speaker 1: finite universe could be enormous. It could extend far beyond
• 24:05
  Speaker 1: everything you can observe. It could be so large that
• 24:08
  Speaker 1: its curvature would be almost impossible to notice from within
• 24:12
  Speaker 1: our small observable region. And if space really does have
• 24:16
  Speaker 1: some hidden global shape, that shape might be leaving clues
• 24:20
  Speaker 1: in the ancient light that surrounds you. Very faint clues,
• 24:24
  Speaker 1: quiet patterns, subtle repetitions. almost invisible traces of the way
• 24:30
  Speaker 1: space connects to itself, so you can remain here for
• 24:34
  Speaker 1: a little longer, floating gently beside the idea. Perhaps the
• 24:39
  Speaker 1: universe has an edge. Perhaps it does not. Perhaps it
• 24:43
  Speaker 1: has a finite amount of space, but no boundary at all.
• 24:47
  Speaker 1: And perhaps, somewhere far beyond your observable horizon, space curves
• 24:52
  Speaker 1: so gently that you would never know it was curving,
• 24:55
  Speaker 1: until one day, After an unimaginably long journey, the darkness
• 25:00
  Speaker 1: ahead began to look strangely familiar. You can let the
• 25:06
  Speaker 1: spacecraft remain very still for a moment. The imagined journey
• 25:11
  Speaker 1: has slowed, the stars are quiet around you, and Earth
• 25:15
  Speaker 1: is somewhere behind you, becoming smaller and softer in the darkness.
• 25:20
  Speaker 1: You have been imagining a universe that could curve back
• 25:23
  Speaker 1: upon itself, A universe with a finite amount of space,
• 25:27
  Speaker 1: yet without a wall, without a border, without an outside
• 25:31
  Speaker 1: that you could eventually step into. It is a strange possibility,
• 25:36
  Speaker 1: and yet there is something even stranger. A universe can
• 25:40
  Speaker 1: be curved without looking curved. At least, it can look
• 25:44
  Speaker 1: almost perfectly flat from where you happen to be. You
• 25:48
  Speaker 1: can think about the surface of a very large sphere.
• 25:51
  Speaker 1: If you were standing on a small patch of that surface,
• 25:54
  Speaker 1: the ground beneath your feet would appear flat. You could
• 25:58
  Speaker 1: place a little object beside you, and it would not
• 26:00
  Speaker 1: seem to roll towards some obvious curve. You could walk
• 26:04
  Speaker 1: across the surface for quite a while, and the curvature
• 26:07
  Speaker 1: might remain too gentle for your senses to notice. Only
• 26:11
  Speaker 1: when you travelled across a much larger distance would the
• 26:14
  Speaker 1: shape gradually reveal itself. Space could behave in a similarly
• 26:19
  Speaker 1: quiet way. If the entire universe were closed, but enormously
• 26:23
  Speaker 1: larger than the region you can observe, then your observable
• 26:27
  Speaker 1: universe might be only a tiny patch of the whole geometry.
• 26:31
  Speaker 1: The curvature could be so gentle that, from your small
• 26:34
  Speaker 1: cosmic neighbourhood, space would appear almost perfectly flat. This is
• 26:39
  Speaker 1: one reason the question is difficult. You are not looking
• 26:43
  Speaker 1: at the universe from the outside. There is no distant
• 26:47
  Speaker 1: balcony where you can stand and see its complete shape.
• 26:50
  Speaker 1: You are inside the thing you are trying to measure.
• 26:53
  Speaker 1: You can only examine the light that reaches you. You
• 26:57
  Speaker 1: can only measure the distances and patterns available within your
• 27:00
  Speaker 1: observable region, and so scientists look for very subtle clues.
• 27:06
  Speaker 1: They look at the ancient light that fills the sky.
• 27:09
  Speaker 1: This light has travelled for billions of years, carrying traces
• 27:13
  Speaker 1: of the early universe with it. You can imagine it
• 27:16
  Speaker 1: as a very faint cosmic memory. arriving from every direction,
• 27:21
  Speaker 1: almost equally quietly, carrying information about the shape and history
• 27:26
  Speaker 1: of the space through which it has travelled. If space
• 27:30
  Speaker 1: had a noticeable curvature, that curvature could slightly change the
• 27:35
  Speaker 1: way very distant patterns appear. The positions of ancient structures,
• 27:40
  Speaker 1: the apparent size of familiar cosmic patterns, and the distribution
• 27:45
  Speaker 1: of matter across enormous distances can all provide clues about
• 27:50
  Speaker 1: the geometry of the universe. You do not need to
• 27:53
  Speaker 1: follow the measurements themselves. You can simply imagine scientists listening
• 27:58
  Speaker 1: to the sky for the smallest possible whisper of curvature.
• 28:03
  Speaker 1: So far, the broad picture has been remarkably close to flat.
• 28:07
  Speaker 1: The measurements are consistent with a universe whose large-scale spatial
• 28:11
  Speaker 1: geometry is very nearly flat. But there is a gentle
• 28:15
  Speaker 1: distinction here. Nearly flat means does not automatically mean infinite,
• 28:20
  Speaker 1: and flat does not by itself tell you everything about
• 28:24
  Speaker 1: how space is connected. A universe could have a geometry
• 28:27
  Speaker 1: that appears flat across the region you can observe, while
• 28:31
  Speaker 1: still having a larger global structure that connects distant regions together.
• 28:36
  Speaker 1: This is where the size of the hidden universe becomes important.
• 28:40
  Speaker 1: Imagine that you are looking across a calm ocean. From
• 28:43
  Speaker 1: where you float, the water seems completely level, You cannot
• 28:47
  Speaker 1: see the curve of the whole Earth. The horizon remains
• 28:51
  Speaker 1: smooth and ordinary, but the planet is curved beneath you,
• 28:55
  Speaker 1: and if you travel far enough, you eventually discover that
• 28:58
  Speaker 1: your path can bring you around the world. The same
• 29:02
  Speaker 1: basic intuition can be applied, very carefully, to cosmic space.
• 29:07
  Speaker 1: If a closed universe were large enough, you might travel
• 29:10
  Speaker 1: through an enormous distance without noticing anything. that your path
• 29:14
  Speaker 1: was slowly bending through the global geometry. You would not
• 29:18
  Speaker 1: suddenly reach a cosmic corner. You would not see the
• 29:22
  Speaker 1: stars bending into an obvious circle. You would simply see
• 29:26
  Speaker 1: space continuing, and continuing, and continuing. The absence of an
• 29:32
  Speaker 1: obvious curvature signature therefore does not mean that every finite
• 29:36
  Speaker 1: possibility has been eliminated. It means that anything curvature must
• 29:40
  Speaker 1: be subtle enough to have escaped the measurements available so far.
• 29:45
  Speaker 1: In the particular closed universe picture you have been imagining,
• 29:48
  Speaker 1: this would mean that the complete universe could be much
• 29:52
  Speaker 1: larger than the observable part, possibly vastly larger. perhaps so
• 29:57
  Speaker 1: much larger that your entire observable region would resemble a
• 30:01
  Speaker 1: tiny window inside a structure whose full dimensions are far
• 30:06
  Speaker 1: beyond your experience. You can let yourself picture that for
• 30:09
  Speaker 1: a moment, a small sphere of visible space surrounding you,
• 30:14
  Speaker 1: and far beyond its surface still more space, not hidden
• 30:18
  Speaker 1: behind a wall, not tucked away in another dimension, simply
• 30:22
  Speaker 1: beyond the distance from which light has had enough time
• 30:25
  Speaker 1: to reach you. the whole universe could extend far beyond
• 30:29
  Speaker 1: what your instruments can currently inspect. And if its global
• 30:33
  Speaker 1: geometry were gently closed, the signs of that closure could
• 30:37
  Speaker 1: be spread across distances far greater than your observable horizon.
• 30:42
  Speaker 1: There is another quiet idea here. The shape of space
• 30:46
  Speaker 1: is not exactly the same question as the way space
• 30:49
  Speaker 1: is connected. You can have space that looks locally flat,
• 30:53
  Speaker 1: While its distant regions are connected in an unusual way,
• 30:57
  Speaker 1: this is sometimes described using the distinction between geometry and topology.
• 31:03
  Speaker 1: You do not need to hold on to the terminology.
• 31:06
  Speaker 1: Just keep the softer picture. Geometry asks how space feels
• 31:10
  Speaker 1: around you. Topology asks how the larger pieces of space
• 31:14
  Speaker 1: are joined together. And sometimes, the universe could look ordinary
• 31:19
  Speaker 1: in your immediate surroundings. while having a much stranger shape
• 31:22
  Speaker 1: when viewed as a whole. This is why cosmologists continue
• 31:26
  Speaker 1: to look for repeated patterns, unusual connections, and other subtle
• 31:31
  Speaker 1: signs in the ancient light of the sky. If distant
• 31:35
  Speaker 1: regions of space were connected in a particular way, light
• 31:38
  Speaker 1: might eventually travel along more than one route toward you.
• 31:43
  Speaker 1: The same ancient object could, in principle, appear from different directions.
• 31:49
  Speaker 1: not because the object had been copied, not because the
• 31:52
  Speaker 1: universe had suddenly created another one, but because the shape
• 31:56
  Speaker 1: of space had allowed the same light to reach you
• 31:58
  Speaker 1: along different paths. That idea leads gently toward an even
• 32:03
  Speaker 1: stranger possibility, a universe that behaves a little like a
• 32:07
  Speaker 1: cosmic hall of mirrors, where the geometry itself could make
• 32:10
  Speaker 1: one distant reality appear more than once. And once you
• 32:15
  Speaker 1: begin imagining that, You are no longer asking only how
• 32:18
  Speaker 1: large the universe is. You are beginning to ask how
• 32:22
  Speaker 1: space connects one place to another. For now, you can
• 32:26
  Speaker 1: simply rest with the quieter thought. Perhaps space is flat.
• 32:31
  Speaker 1: Perhaps it is curved. Perhaps it is finite in a
• 32:34
  Speaker 1: way so enormous that its boundaries never appear, because there
• 32:38
  Speaker 1: are no boundaries to appear. And perhaps the shape of
• 32:42
  Speaker 1: everything around you is so gentle, so immense... and so
• 32:46
  Speaker 1: carefully hidden that even after looking across billions of light-years,
• 32:50
  Speaker 1: you are still seeing only a small, quiet part of
• 32:54
  Speaker 1: the whole. You can remain quietly inside the darkness for
• 32:59
  Speaker 1: a little while longer. The stars are still around you,
• 33:03
  Speaker 1: distant and patient, their light arriving after journeys so long
• 33:08
  Speaker 1: that the beginning of each journey belongs to another age.
• 33:11
  Speaker 1: you have already imagined space curving gently back upon itself.
• 33:16
  Speaker 1: A traveller could move forward without finding a wall, without
• 33:20
  Speaker 1: reaching an outside, perhaps eventually returning toward the place where
• 33:25
  Speaker 1: the journey began. But there is more than one way
• 33:28
  Speaker 1: for a finite universe to be connected. The universe does
• 33:32
  Speaker 1: not have to be shaped like the simplest sphere. It
• 33:35
  Speaker 1: could have a more complicated arrangement. one in which different
• 33:39
  Speaker 1: directions through space connect back to different places. To imagine this,
• 33:44
  Speaker 1: you can think of something like a very gentle cosmic donut.
• 33:48
  Speaker 1: Not a donut floating through some larger room, just the
• 33:52
  Speaker 1: shape of the space itself. In mathematics, a shape like
• 33:55
  Speaker 1: this can be called a three-dimensional torus, but you do
• 33:59
  Speaker 1: not need to carry the name with you. The important
• 34:02
  Speaker 1: idea is simply that space can be connected in a
• 34:05
  Speaker 1: way that allows you to leave one region and, after
• 34:09
  Speaker 1: travelling far enough, return from another direction. Imagine yourself once
• 34:14
  Speaker 1: again inside a quiet spacecraft. You choose one direction. You
• 34:19
  Speaker 1: begin moving forward. The stars pass slowly. Nothing tells you
• 34:24
  Speaker 1: that space is connected in any unusual way. There is
• 34:28
  Speaker 1: no cosmic road sign. There is no glowing arrow in
• 34:31
  Speaker 1: the darkness. There is only the steady feeling of motion
• 34:35
  Speaker 1: through an immense and almost empty universe. Now imagine that
• 34:39
  Speaker 1: another traveller leaves from the same starting point, but instead
• 34:43
  Speaker 1: of following your direction, they choose a direction at a
• 34:47
  Speaker 1: right angle to yours. Both of you continue forward. Neither
• 34:51
  Speaker 1: traveller turns around. Neither traveller reaches an edge. And yet,
• 34:56
  Speaker 1: because the larger space has a particular topology... Your paths
• 35:01
  Speaker 1: could eventually return to the starting region in different ways.
• 35:05
  Speaker 1: One of you might come home sooner, the other might
• 35:08
  Speaker 1: need to travel much farther. The two journeys could have
• 35:12
  Speaker 1: completely different lengths, even though both began from the same place.
• 35:16
  Speaker 1: This is one of the reasons the shape of the
• 35:18
  Speaker 1: universe is more complicated than simply asking whether it is curved.
• 35:22
  Speaker 1: You are not only asking whether space bends, you are
• 35:26
  Speaker 1: asking how space connects. and that quiet distinction leads to
• 35:30
  Speaker 1: something especially beautiful. Light does not need to take the
• 35:34
  Speaker 1: shortest imaginable route in the ordinary sense you are used to.
• 35:39
  Speaker 1: If space itself is connected in an unusual way, light
• 35:43
  Speaker 1: can potentially travel along different paths and eventually arrive at
• 35:47
  Speaker 1: you from different directions. Imagine that a distant galaxy sends
• 35:51
  Speaker 1: out light. One beam travels toward you along one route
• 35:55
  Speaker 1: through space. another beam travels in a different direction. If
• 36:00
  Speaker 1: the universe is connected in the right way, both paths
• 36:03
  Speaker 1: could eventually bring light from the same galaxy back to
• 36:06
  Speaker 1: your small region of space. You might look into one
• 36:10
  Speaker 1: part of the sky and see the galaxy. Then you
• 36:13
  Speaker 1: might look somewhere else and see what appears to be
• 36:16
  Speaker 1: another galaxy. The two images could look different. They could
• 36:20
  Speaker 1: even seem to belong to different moments in cosmic history.
• 36:24
  Speaker 1: But in this strange possibility, they would actually be different
• 36:28
  Speaker 1: views of the same distant object. The universe itself would
• 36:32
  Speaker 1: be creating the illusion of duplication, a kind of cosmic
• 36:36
  Speaker 1: hall of mirrors, and the mirrors would not be made
• 36:39
  Speaker 1: of glass. They would be made by the geometry and
• 36:42
  Speaker 1: topology of space. You can imagine a star very far away.
• 36:47
  Speaker 1: Perhaps you see it in one direction, glowing softly, its
• 36:51
  Speaker 1: light having travelled across billions of years. Then, In another
• 36:56
  Speaker 1: part of the sky, you see another image. The image
• 37:00
  Speaker 1: looks similar. The position is different. The apparent age may
• 37:04
  Speaker 1: be different. Perhaps one image shows the star at an
• 37:08
  Speaker 1: earlier stage of its life. Another could show it much later.
• 37:12
  Speaker 1: You would not be seeing the star twice because there
• 37:15
  Speaker 1: were two identical stars. You could, in principle, be seeing
• 37:20
  Speaker 1: the same star through two different paths across a finite universe.
• 37:24
  Speaker 1: One view would be like looking at an old photograph.
• 37:28
  Speaker 1: Another would be like finding another photograph of the same
• 37:31
  Speaker 1: person taken much later. The person has not been copied.
• 37:35
  Speaker 1: Time has simply given you different views of the same story.
• 37:39
  Speaker 1: This possibility sounds almost magical, but the underlying idea is
• 37:43
  Speaker 1: simply about light following paths through space. And that is
• 37:47
  Speaker 1: why the ancient light of the universe becomes so useful.
• 37:51
  Speaker 1: The sky contains enormous numbers of patterns. Galaxies. Clusters. Ancient radiation.
• 37:59
  Speaker 1: Large-scale structures stretching across distances almost impossible to imagine. If
• 38:05
  Speaker 1: space were connected in a small enough way, some of
• 38:08
  Speaker 1: these patterns might repeat. Scientists could search for matching structures.
• 38:13
  Speaker 1: They could look for repeated patterns in the cosmic background.
• 38:17
  Speaker 1: They could ask whether two apparently separate regions might actually
• 38:20
  Speaker 1: be different views of the same underlying place. So far,
• 38:25
  Speaker 1: no convincing evidence has established that our universe has such
• 38:28
  Speaker 1: a small, repeating topology. The absence of a clear signal
• 38:32
  Speaker 1: does not mean that every possible topology has been ruled out.
• 38:37
  Speaker 1: It simply means that if such connections exist, they have
• 38:40
  Speaker 1: not revealed themselves clearly in the observations available to us.
• 38:44
  Speaker 1: Perhaps the universe is simply much larger than the region
• 38:48
  Speaker 1: we can observe. Perhaps the repeating paths are so enormous
• 38:52
  Speaker 1: that the light has not had enough time to complete them,
• 38:55
  Speaker 1: or perhaps space is connected in a completely different way.
• 38:59
  Speaker 1: You can let those possibilities drift past without choosing one.
• 39:03
  Speaker 1: The important idea is that the universe could be finite
• 39:07
  Speaker 1: without behaving like a box. It could be closed without
• 39:10
  Speaker 1: having a border, and it could even connect distant regions
• 39:14
  Speaker 1: in ways that make the same object appear from different directions.
• 39:18
  Speaker 1: there is something almost soothing about that thought. The night
• 39:22
  Speaker 1: sky might contain familiar things that you would never recognise
• 39:26
  Speaker 1: as familiar. A distant galaxy could appear to be alone
• 39:30
  Speaker 1: in one direction, while another image of that same galaxy
• 39:33
  Speaker 1: waits quietly somewhere else. A star could seem to be
• 39:37
  Speaker 1: telling one part of its history in one place, and
• 39:40
  Speaker 1: another part of its history somewhere far across the sky.
• 39:44
  Speaker 1: The light would not be lying. It would simply be
• 39:47
  Speaker 1: taking its time and it would be following the shape
• 39:50
  Speaker 1: of space, and if space is connected in a way
• 39:53
  Speaker 1: you cannot easily see, then the universe could be much
• 39:57
  Speaker 1: more intimate than its enormous distances suggest. Places that appear
• 40:02
  Speaker 1: impossibly far apart might belong to the same underlying space,
• 40:07
  Speaker 1: different directions might quietly lead toward the same regions, and
• 40:12
  Speaker 1: the darkness above you might contain not only distant worlds,
• 40:16
  Speaker 1: but different views of the same worlds, separated by journeys
• 40:20
  Speaker 1: of light that are far longer than any journey you
• 40:23
  Speaker 1: could make. So for now, you can simply rest beneath
• 40:27
  Speaker 1: that possibility. No need to solve the shape of everything,
• 40:31
  Speaker 1: no need to decide whether the universe is a sphere,
• 40:34
  Speaker 1: a donut, something flatter, something stranger, or something that has
• 40:39
  Speaker 1: no finite shape at all. You can just listen to
• 40:42
  Speaker 1: the quiet idea that space may have connections hidden beyond
• 40:46
  Speaker 1: ordinary sight, and somewhere in that immense darkness, perhaps a
• 40:51
  Speaker 1: single ancient light is travelling along one path toward you,
• 40:55
  Speaker 1: while another path is carrying the same story from another direction, slowly, gently,
• 41:01
  Speaker 1: without urgency, through a universe whose shape may be far
• 41:05
  Speaker 1: more subtle than anything your eyes could ever reveal. You
• 41:11
  Speaker 1: can let the idea of the cosmic hall of mirrors
• 41:14
  Speaker 1: become quiet again. Perhaps space is connected in a complicated way.
• 41:19
  Speaker 1: Perhaps distant light can follow different paths. Perhaps the same
• 41:23
  Speaker 1: ancient galaxy could, in principle, appear more than once, like
• 41:28
  Speaker 1: one distant story arriving through several roads. But there is
• 41:32
  Speaker 1: another possibility, simpler in one sense, and perhaps stranger in another.
• 41:38
  Speaker 1: Perhaps space does not curve back at all, Perhaps there
• 41:42
  Speaker 1: is no final connection waiting somewhere beyond the horizon. Perhaps
• 41:46
  Speaker 1: you can simply keep going, and keep going, and keep going.
• 41:52
  Speaker 1: Not because you are travelling towards some enormous destination, but
• 41:56
  Speaker 1: because there is no final destination built into space. There
• 42:00
  Speaker 1: is no last galaxy, no final region, no place where
• 42:04
  Speaker 1: the universe quietly runs out. This is the possibility of
• 42:09
  Speaker 1: an infinite universe. When you hear the word infinite, it
• 42:13
  Speaker 1: can feel enormous, almost too large for the mind to hold.
• 42:17
  Speaker 1: You might imagine an endless line stretching into darkness, with
• 42:21
  Speaker 1: one galaxy after another appearing forever. But infinity is not
• 42:26
  Speaker 1: really a very large number. It is the absence of
• 42:29
  Speaker 1: a final number. You can always imagine going farther, and
• 42:33
  Speaker 1: then farther again, and then farther still. There is no
• 42:38
  Speaker 1: last step waiting at the end. If the universe is
• 42:41
  Speaker 1: spatially infinite, you could travel in any direction and never
• 42:45
  Speaker 1: reach a final wall. You would not arrive at a
• 42:48
  Speaker 1: cosmic border. You would not find an empty region where
• 42:52
  Speaker 1: space suddenly stops. You would simply continue through space. Galaxies
• 42:57
  Speaker 1: could continue. Clusters could continue. Vast dark regions between them
• 43:03
  Speaker 1: could continue. The same physical laws could continue. The quiet
• 43:07
  Speaker 1: structure of space could continue beyond every distance you have travelled,
• 43:12
  Speaker 1: and there would never be a final place where you
• 43:14
  Speaker 1: could point and say, this is the end of everything.
• 43:18
  Speaker 1: You can imagine floating in your spacecraft again. There is
• 43:22
  Speaker 1: no destination. You are simply moving through an endless landscape
• 43:26
  Speaker 1: of darkness and distant light. A galaxy appears, then another,
• 43:31
  Speaker 1: then another. And even when you imagine yourself travelling farther
• 43:35
  Speaker 1: than any human journey could ever reach, the universe does
• 43:38
  Speaker 1: not become smaller. It does not become closer to an edge.
• 43:42
  Speaker 1: There is simply more. This idea may sound strange because
• 43:46
  Speaker 1: you are accustomed to things becoming larger by having a boundary.
• 43:50
  Speaker 1: A room can become larger because its walls move outward.
• 43:54
  Speaker 1: A balloon can expand because its surface has a limited shape.
• 43:59
  Speaker 1: But cosmic expansion does not require an outer wall. Space
• 44:03
  Speaker 1: itself can expand. You can imagine two distant galaxies drifting
• 44:08
  Speaker 1: farther apart, not because they are necessarily racing through a
• 44:12
  Speaker 1: pre-existing empty room, but because the space between them is changing.
• 44:17
  Speaker 1: And if space is infinite, that process can still happen.
• 44:21
  Speaker 1: An infinite universe can expand. This is one of those
• 44:24
  Speaker 1: ideas that feels contradictory only because everyday experience has trained
• 44:29
  Speaker 1: you to think of expansion as something that happens inside
• 44:33
  Speaker 1: a container. The universe does not need to have such
• 44:36
  Speaker 1: a container. There is no cosmic room around the universe.
• 44:41
  Speaker 1: The distances between distant regions can grow, while the whole
• 44:44
  Speaker 1: of space remains without a boundary. So you can have
• 44:47
  Speaker 1: infinite space. And you can have expansion. The two ideas
• 44:52
  Speaker 1: do not cancel each other. You can let that thought
• 44:55
  Speaker 1: settle gently. Infinite does not mean frozen. Infinite does not
• 45:00
  Speaker 1: mean unchanging. Infinite simply means there is no final spatial boundary,
• 45:06
  Speaker 1: no last region beyond which there is nothing more. And
• 45:10
  Speaker 1: there is another distinction worth keeping very softly in mind.
• 45:14
  Speaker 1: An infinite universe does not necessarily mean an infinite past.
• 45:19
  Speaker 1: Space and time are not the same question. You can
• 45:23
  Speaker 1: imagine a universe that extends without end across space. while
• 45:27
  Speaker 1: still having a finite history leading back toward the hot,
• 45:31
  Speaker 1: dense early universe described by modern cosmology. So when you
• 45:36
  Speaker 1: hear that the universe might be infinite, you do not
• 45:39
  Speaker 1: need to imagine that everything has existed forever. Spatial infinity
• 45:44
  Speaker 1: is about how far space extends. It is not automatically
• 45:48
  Speaker 1: a statement about how long the universe has existed. You
• 45:51
  Speaker 1: can have endless distance without endless time. You can have
• 45:55
  Speaker 1: a universe with no final galaxy, while still having a
• 45:59
  Speaker 1: cosmic history with a beginning to the expansion we can trace.
• 46:03
  Speaker 1: This distinction is easy to lose because your ordinary language
• 46:07
  Speaker 1: uses the same word, forever, for both distance and time.
• 46:12
  Speaker 1: But the universe does not have to follow the habits
• 46:14
  Speaker 1: of ordinary language. You can imagine a line that has
• 46:18
  Speaker 1: no end point, and you can imagine a clock that
• 46:21
  Speaker 1: has only been running for a limited amount of time.
• 46:24
  Speaker 1: Those are different properties, the same kind of separation can
• 46:28
  Speaker 1: exist in cosmology. And there is something else quietly interesting
• 46:32
  Speaker 1: about an infinite universe. If space really does continue without end,
• 46:37
  Speaker 1: then you are not living near the centre of it.
• 46:39
  Speaker 1: There would be no centre in the ordinary sense. Every
• 46:43
  Speaker 1: observer could look around and find themselves surrounded by their
• 46:47
  Speaker 1: own observable region. Every observer would have a horizon defined
• 46:51
  Speaker 1: by the age of the universe, the speed of light,
• 46:55
  Speaker 1: and the history of cosmic expansion. From your perspective, the
• 46:59
  Speaker 1: visible universe surrounds you. From someone unimaginably far away, their
• 47:04
  Speaker 1: visible universe would surround them. Their cosmic horizon would be
• 47:08
  Speaker 1: centered on them, just as yours is centered on you.
• 47:12
  Speaker 1: Neither of you would occupy a special cosmic middle. There
• 47:16
  Speaker 1: would simply be more space beyond each horizon. And if
• 47:19
  Speaker 1: you travel farther, the same idea remains. You might leave
• 47:24
  Speaker 1: your current observable region in imagination, cross distances that make
• 47:28
  Speaker 1: billions of light-years seem small, and still find yourself surrounded
• 47:32
  Speaker 1: by more space. There would be no final moment when
• 47:36
  Speaker 1: the universe whispers that you have arrived at its outermost edge.
• 47:40
  Speaker 1: Because in this possibility, there is no outermost edge. You
• 47:44
  Speaker 1: can let yourself rest with that. A universe with no
• 47:48
  Speaker 1: final wall. A universe with no last directions. A universe
• 47:53
  Speaker 1: in which every horizon is only a limit to what
• 47:56
  Speaker 1: can reach you, rather than a boundary of what exists.
• 48:00
  Speaker 1: And perhaps this is the simplest way to understand why
• 48:03
  Speaker 1: the question of infinity remains so difficult. You cannot stand
• 48:07
  Speaker 1: outside an infinite universe and look back at it. There
• 48:11
  Speaker 1: is no outside position available. You are always somewhere within it.
• 48:16
  Speaker 1: Your instruments can see only so far. Your light can
• 48:19
  Speaker 1: travel only so far. Your lifetime is brief. Even the
• 48:24
  Speaker 1: age of the cosmos, immense as it feels, gives light
• 48:28
  Speaker 1: only a finite amount of time to cross space and
• 48:31
  Speaker 1: bring information to you. So infinity may remain partly beyond
• 48:36
  Speaker 1: direct experience. You can describe it with mathematics. You can
• 48:40
  Speaker 1: explore what its physical consequences would be. You can compare
• 48:45
  Speaker 1: those consequences with observations. But you cannot simply walk to
• 48:49
  Speaker 1: the edge and check. because if the universe is truly infinite,
• 48:53
  Speaker 1: there is no edge to reach. And perhaps, somewhere far
• 48:58
  Speaker 1: beyond the last visible galaxy in your imagination, the darkness
• 49:02
  Speaker 1: simply continues, not as a frightening emptiness, but as an
• 49:07
  Speaker 1: absence of finality. More space, more distance, more quiet. No wall,
• 49:13
  Speaker 1: no border, no last place. Only the gentle possibility that
• 49:18
  Speaker 1: wherever you might go, there would always be somewhere farther still,
• 49:23
  Speaker 1: waiting without urgency beneath the same quiet laws of nature.
• 49:30
  Speaker 1: You can stay here beneath the quiet darkness for a
• 49:33
  Speaker 1: little longer. The universe around you has become almost impossibly large. First,
• 49:39
  Speaker 1: You imagined the small region of space that light has
• 49:43
  Speaker 1: had time to reveal. Then you imagined what might lie
• 49:46
  Speaker 1: beyond that horizon. You imagined a finite universe without an edge,
• 49:51
  Speaker 1: perhaps curving gently back toward itself. You imagined more complicated connections,
• 49:58
  Speaker 1: where light might travel along different paths and make one
• 50:01
  Speaker 1: distant galaxy appear more than once. And then you imagined
• 50:05
  Speaker 1: something even simpler. Perhaps space simply continues. There is no
• 50:10
  Speaker 1: final galaxy, no last direction, no outer wall, just more space,
• 50:16
  Speaker 1: extending farther than any journey you could make. And when
• 50:20
  Speaker 1: you allow that possibility to remain in your mind for
• 50:23
  Speaker 1: a while, another strange thought begins to appear. If space
• 50:28
  Speaker 1: really is infinite, could the things inside it repeat? Could
• 50:32
  Speaker 1: there be another Earth, another night sky, another room, another
• 50:36
  Speaker 1: person sitting quietly and listening to a science story, while
• 50:40
  Speaker 1: the rest of the universe continues around them. Perhaps even
• 50:44
  Speaker 1: another you. It sounds like something from a dream, but
• 50:48
  Speaker 1: the basic idea begins with something much quieter. There are
• 50:52
  Speaker 1: only so many ways that a small region of space
• 50:55
  Speaker 1: can be arranged if you limit the amount of matter
• 50:57
  Speaker 1: and energy inside it, and consider the physical rules that
• 51:01
  Speaker 1: govern those particles. Atoms can move. Particles can combine. Stars
• 51:07
  Speaker 1: can form. Planets can gather. life can develop. But the
• 51:12
  Speaker 1: number of possible arrangements within a sufficiently limited region, under
• 51:16
  Speaker 1: a particular set of physical assumptions, may still be finite,
• 51:21
  Speaker 1: even if that number is unimaginably enormous. Now imagine an
• 51:25
  Speaker 1: infinite amount of space divided into many regions of roughly
• 51:30
  Speaker 1: similar size. If the number of possible arrangements in each
• 51:33
  Speaker 1: region is limited, then with enough regions, some arrangements could
• 51:37
  Speaker 1: eventually appear again. and again, and again. Not because the
• 51:43
  Speaker 1: universe is trying to make copies, not because some cosmic
• 51:47
  Speaker 1: intelligence is pressing a repeat button, simply because infinite space
• 51:51
  Speaker 1: gives an endless number of opportunities for physical arrangements to occur.
• 51:56
  Speaker 1: You can imagine scattering an enormous collection of tiny stones
• 51:59
  Speaker 1: across an endless landscape. If there were only a limited
• 52:03
  Speaker 1: number of patterns in which the stones could be arranged
• 52:06
  Speaker 1: within each small area … then eventually some patterns might recur.
• 52:12
  Speaker 1: The same basic arrangement could appear far away, and farther
• 52:16
  Speaker 1: away again. The idea becomes stranger when you imagine increasingly
• 52:20
  Speaker 1: complicated arrangements. Perhaps a small cluster of atoms resembles another.
• 52:26
  Speaker 1: Perhaps a solar system has a distant counterpart. Perhaps a
• 52:30
  Speaker 1: planet has the same atmosphere. Perhaps, under the right assumptions,
• 52:35
  Speaker 1: a world could develop conditions remarkably similar to Earth. And
• 52:39
  Speaker 1: if the arrangement became extraordinarily precise, perhaps a person could
• 52:44
  Speaker 1: exist there who is physically indistinguishable from you at one
• 52:49
  Speaker 1: particular moment. The thought is fascinating, but there is an
• 52:53
  Speaker 1: important quiet boundary here. Infinite space does not automatically guarantee
• 52:58
  Speaker 1: an exact copy of you. The conclusion depends on assumptions
• 53:02
  Speaker 1: about the possible physical states, how those states are distributed,
• 53:07
  Speaker 1: and whether the universe really is infinite in the relevant sense. So,
• 53:12
  Speaker 1: this remains a theoretical possibility, not something science has observed.
• 53:17
  Speaker 1: You do not need to imagine another you as a certainty.
• 53:21
  Speaker 1: You can simply let the possibility drift beside you. Somewhere
• 53:25
  Speaker 1: unimaginably far away, perhaps matter has arranged itself into something familiar.
• 53:31
  Speaker 1: Perhaps there is another planet. Perhaps another ocean. Perhaps another
• 53:36
  Speaker 1: night sky. perhaps another small room, and perhaps, for one
• 53:41
  Speaker 1: brief moment, another person looks upward and wonders whether somewhere
• 53:45
  Speaker 1: else in the universe someone might be doing exactly the
• 53:49
  Speaker 1: same thing. The distances involved would be difficult even to describe.
• 53:54
  Speaker 1: If repetitions exist, they could be vastly farther away than
• 53:58
  Speaker 1: anything you can observe, far beyond the galaxies whose light
• 54:01
  Speaker 1: reaches your eyes, far beyond the horizon that defines your
• 54:05
  Speaker 1: visible universe. Far beyond any realistic spacecraft journey, the distance
• 54:11
  Speaker 1: would not be merely far, it would be almost impossible
• 54:14
  Speaker 1: to place into ordinary imagination. And yet, in an infinite universe,
• 54:19
  Speaker 1: distance itself does not prevent something from existing. Something can
• 54:24
  Speaker 1: be extraordinarily unlikely within one region, and still become possible
• 54:29
  Speaker 1: somewhere across an endless expanse, if the conditions required for
• 54:33
  Speaker 1: it are allowed. and if the necessary opportunities continue without limit.
• 54:38
  Speaker 1: You can rest with that thought without trying to picture
• 54:41
  Speaker 1: the number. There is no need for enormous mathematical notation.
• 54:46
  Speaker 1: There is no useful number for your mind to hold.
• 54:49
  Speaker 1: Just imagine a pattern appearing once, then disappearing into the distance, then, perhaps,
• 54:57
  Speaker 1: appearing again much farther away, like a faint rhythm repeated
• 55:01
  Speaker 1: across an endless darkness. But there is an even gentler
• 55:05
  Speaker 1: way to think about the idea. You do not need
• 55:08
  Speaker 1: another Earth. You do not need another person. You do
• 55:11
  Speaker 1: not even need exact repetition. An infinite universe could contain
• 55:16
  Speaker 1: an almost unimaginable variety of things. There could be planets
• 55:20
  Speaker 1: unlike anything you have ever seen. Stars with histories completely
• 55:25
  Speaker 1: different from our sun. Galaxies with shapes you have never imagined.
• 55:30
  Speaker 1: Regions of space so empty that millions of light-years might
• 55:34
  Speaker 1: pass without a single star nearby. Other regions might be
• 55:38
  Speaker 1: crowded with galaxies. And between all of them, the same
• 55:41
  Speaker 1: basic physical laws could continue quietly. Gravity. Light. Matter. Time.
• 55:49
  Speaker 1: The slow unfolding of cosmic history. Perhaps that is the
• 55:52
  Speaker 1: more beautiful consequence of infinity. It does not merely suggest copies.
• 55:58
  Speaker 1: It suggests abundance without a final limit. If space has
• 56:02
  Speaker 1: no end, then there may be no final example of anything.
• 56:06
  Speaker 1: No last galaxy. No final star. No ultimate arrangement of matter.
• 56:12
  Speaker 1: There would always be room for something farther away. And
• 56:15
  Speaker 1: if the laws of nature permit a particular arrangement, then
• 56:19
  Speaker 1: an infinite universe raises the quiet question of whether that
• 56:23
  Speaker 1: arrangement might occur again. Maybe once. Maybe many times. maybe
• 56:29
  Speaker 1: infinitely many times, or perhaps the assumptions needed for such repetition,
• 56:34
  Speaker 1: do not describe our universe at all. Science cannot simply
• 56:38
  Speaker 1: choose the more poetic possibility. It has to follow the evidence,
• 56:43
  Speaker 1: and at present, the total size of the universe remains unknown.
• 56:48
  Speaker 1: You know only the part whose information has had time
• 56:50
  Speaker 1: to reach you. Everything beyond that remains partly hidden, so
• 56:55
  Speaker 1: the idea of another you belongs in the same wide
• 56:58
  Speaker 1: territory where cosmology begins to meet philosophy. It is not
• 57:03
  Speaker 1: a prediction that you should expect to verify tomorrow. It
• 57:06
  Speaker 1: is a consequence that can emerge from certain models and
• 57:09
  Speaker 1: assumptions about infinite space. And perhaps that is enough. You
• 57:14
  Speaker 1: can let the thought remain unfinished. Because you are here,
• 57:18
  Speaker 1: in this particular moment, beneath this particular sky. Whether or
• 57:23
  Speaker 1: not another version of your story exists somewhere unimaginably far away,
• 57:28
  Speaker 1: this moment does not need a duplicate to be real.
• 57:32
  Speaker 1: You can hear the quiet sound around you. You can
• 57:35
  Speaker 1: feel the weight of your body resting where it is.
• 57:38
  Speaker 1: There is nothing to solve, nothing to prove. You are safe.
• 57:43
  Speaker 1: There is nothing to do, just listen and drift. And somewhere,
• 57:47
  Speaker 1: beyond the limits of what your eyes can see, The
• 57:50
  Speaker 1: universe may be continuing in ways you will never witness,
• 57:54
  Speaker 1: perhaps repeating certain patterns, perhaps creating forms that have never
• 57:59
  Speaker 1: existed before, perhaps doing something even stranger. You do not
• 58:04
  Speaker 1: need to know which one is true tonight. You can
• 58:06
  Speaker 1: simply rest beneath the possibility that an endless universe, if
• 58:11
  Speaker 1: it truly is endless, would have no shortage of space
• 58:15
  Speaker 1: for mystery. You can let the possibility of another Earth
• 58:21
  Speaker 1: drift quietly away now. You do not need to decide
• 58:24
  Speaker 1: whether another version of your story exists somewhere in the darkness.
• 58:29
  Speaker 1: Perhaps space is infinite. Perhaps it is finite but unimaginably large.
• 58:35
  Speaker 1: Perhaps space connects back upon itself in a shape that
• 58:38
  Speaker 1: would seem impossible from the small region you occupy. Perhaps
• 58:42
  Speaker 1: there are patterns repeating across distances so vast that no
• 58:46
  Speaker 1: light from them has ever reached you. Or perhaps the
• 58:49
  Speaker 1: universe has a structure that is still beyond the ideas
• 58:53
  Speaker 1: you have imagined tonight. For now, you can simply return
• 58:57
  Speaker 1: to something much closer, the small circle of visible space
• 59:01
  Speaker 1: surrounding you, the observable universe. It is a strange thing
• 59:05
  Speaker 1: to call it a boundary, because it is not really
• 59:08
  Speaker 1: a boundary of space. it is a boundary of information.
• 59:12
  Speaker 1: Light has been travelling through the universe for billions of years,
• 59:16
  Speaker 1: carrying quiet messages from distant places. Some of those messages
• 59:21
  Speaker 1: have reached you, others have not, and some may never
• 59:25
  Speaker 1: reach you. So when you look outward into the night,
• 59:29
  Speaker 1: You are not seeing the entire universe. You are seeing
• 59:32
  Speaker 1: the part of the universe whose light, or whose other
• 59:36
  Speaker 1: forms of information, have had enough time to arrive. You
• 59:40
  Speaker 1: can think of yourself sitting inside a vast sphere of
• 59:44
  Speaker 1: received light. The sphere is not a wall. You could
• 59:47
  Speaker 1: not touch it. You could not fly toward it and
• 59:51
  Speaker 1: eventually collide with it. If you travelled outward, the horizon
• 59:55
  Speaker 1: would simply remain a limit and on what information could
• 59:59
  Speaker 1: reach you from each direction. And as the universe changes
• 1:00:03
  Speaker 1: and expands, that horizon has a history of its own.
• 1:00:07
  Speaker 1: This is why the observable universe can be so much
• 1:00:10
  Speaker 1: larger across than the simple age of the universe multiplied
• 1:00:14
  Speaker 1: by the speed of light might suggest. Space itself has
• 1:00:18
  Speaker 1: been expanding while the light was travelling. The distances between
• 1:00:22
  Speaker 1: you and the ancient sources of that light have changed.
• 1:00:26
  Speaker 1: so the places whose light has taken billions of years
• 1:00:29
  Speaker 1: to reach you can now be much farther away than
• 1:00:32
  Speaker 1: those same billions of light-years might suggest in a simple,
• 1:00:36
  Speaker 1: unmoving picture. You do not need to calculate the distance.
• 1:00:40
  Speaker 1: You can simply imagine the light travelling across a changing
• 1:00:44
  Speaker 1: landscape of space, slowly, quietly, for an unimaginably long time,
• 1:00:50
  Speaker 1: and eventually arriving here. This ancient light gives scientists one
• 1:00:55
  Speaker 1: of their most valuable ways to investigate the universe as
• 1:00:58
  Speaker 1: a whole. The oldest light that can be observed directly
• 1:01:03
  Speaker 1: comes from a very early period in cosmic history. It
• 1:01:06
  Speaker 1: has travelled through expanding space for almost the entire age
• 1:01:10
  Speaker 1: of the cosmos. By studying its patterns, scientists can learn
• 1:01:15
  Speaker 1: about the early universe and about the large-scale geometry through
• 1:01:19
  Speaker 1: which that light has travelled. The patterns are extremely subtle.
• 1:01:24
  Speaker 1: You would not look at the night sky with your
• 1:01:26
  Speaker 1: eyes and immediately see the shape of the universe written
• 1:01:28
  Speaker 1: across it. The clues are hidden in tiny differences, small variations,
• 1:01:34
  Speaker 1: gentle relationships between enormous structures. A little like listening to
• 1:01:39
  Speaker 1: a very quiet sound and trying to understand the room
• 1:01:42
  Speaker 1: in which that sound was created. If the geometry of
• 1:01:46
  Speaker 1: space were strongly curved … The patterns in ancient light
• 1:01:50
  Speaker 1: could be affected in ways that scientists could potentially measure.
• 1:01:54
  Speaker 1: If space were very nearly flat, those patterns would look different.
• 1:01:58
  Speaker 1: And if the universe had certain unusual connections, there might
• 1:02:02
  Speaker 1: also be repeated structures or matching patterns that could reveal
• 1:02:06
  Speaker 1: something about its topology. Scientists have searched for such clues.
• 1:02:12
  Speaker 1: So far, there is no definitive observation showing that the
• 1:02:15
  Speaker 1: universe is a small closed space, that connects back upon itself.
• 1:02:21
  Speaker 1: There is also no observation that proves the universe must
• 1:02:24
  Speaker 1: be infinite. And this is where the mystery becomes especially gentle.
• 1:02:29
  Speaker 1: Science can measure the shape of the region it can observe.
• 1:02:32
  Speaker 1: It can test models. It can compare predictions with the
• 1:02:36
  Speaker 1: ancient light arriving from distant space. It can search for curvature.
• 1:02:41
  Speaker 1: It can search for repeated patterns. It can study the
• 1:02:45
  Speaker 1: distribution of galaxies across enormous distances. But there is a
• 1:02:49
  Speaker 1: difference between measuring what you can see and proving what
• 1:02:53
  Speaker 1: exists beyond every possible horizon. That difference matters. Imagine standing
• 1:02:59
  Speaker 1: beside a calm ocean at night. You can see the
• 1:03:03
  Speaker 1: water stretching toward the horizon. You can measure its surface.
• 1:03:08
  Speaker 1: You can study the waves. You can learn about the
• 1:03:11
  Speaker 1: depth and movement of the water near you. But you
• 1:03:14
  Speaker 1: cannot determine the complete shape of the entire ocean simply
• 1:03:18
  Speaker 1: by looking across one horizon. Cosmology faces a similar limitation,
• 1:03:23
  Speaker 1: only on a scale so much larger that ordinary imagination
• 1:03:28
  Speaker 1: begins to become quiet. You are inside the universe. There
• 1:03:32
  Speaker 1: is no external viewpoint from which you can photograph the
• 1:03:35
  Speaker 1: whole thing. There is no cosmic room where you can
• 1:03:39
  Speaker 1: stand outside and measure its walls. There is no final
• 1:03:42
  Speaker 1: observation that simply says, here is the edge. and if
• 1:03:46
  Speaker 1: the universe is infinite, there is no edge to find.
• 1:03:50
  Speaker 1: If it is finite but boundaryless, there may still be
• 1:03:54
  Speaker 1: no edge to find. Even if it is closed and connected,
• 1:03:58
  Speaker 1: its curvature could be so gentle and its dimensions so
• 1:04:02
  Speaker 1: enormous that the observable region would not reveal the complete shape.
• 1:04:07
  Speaker 1: This means that several very different universes can look surprisingly
• 1:04:11
  Speaker 1: similar from where you are. A truly infinite universe could
• 1:04:15
  Speaker 1: look almost exactly like a finite universe that is simply
• 1:04:19
  Speaker 1: much larger than what you can observe. A closed universe
• 1:04:23
  Speaker 1: could appear nearly flat if its curvature is gentle enough.
• 1:04:27
  Speaker 1: A more complicated topology could remain hidden if its characteristic
• 1:04:31
  Speaker 1: distances are larger than the region from which light has
• 1:04:34
  Speaker 1: reached you. So the night sky does not necessarily give
• 1:04:38
  Speaker 1: you one simple answer. It gives you constraints. It narrows
• 1:04:43
  Speaker 1: the possibilities. It quietly tells scientists which versions of the
• 1:04:47
  Speaker 1: universe are less consistent with what they see, and which
• 1:04:51
  Speaker 1: remain possible. And perhaps that is enough. Because science does
• 1:04:56
  Speaker 1: not always end with a final sentence. Sometimes it ends
• 1:05:00
  Speaker 1: with a boundary around what can currently be known. You
• 1:05:03
  Speaker 1: can feel that boundary without fearing it. It is not
• 1:05:06
  Speaker 1: a failure. It is simply the horizon of observation. The
• 1:05:10
  Speaker 1: universe does not become smaller because you cannot see beyond it.
• 1:05:14
  Speaker 1: There is no requirement for reality to stop where your
• 1:05:17
  Speaker 1: instruments stop receiving information. There may be more space beyond.
• 1:05:22
  Speaker 1: There may be connections you cannot yet detect. There may
• 1:05:25
  Speaker 1: be regions whose light is still travelling toward you. And
• 1:05:29
  Speaker 1: there may be regions from which no signal will ever arrive.
• 1:05:33
  Speaker 1: The observable universe is therefore both enormous and strangely small.
• 1:05:38
  Speaker 1: Enormous because it contains more galaxies, stars, planets, gas, dust, radiation.
• 1:05:44
  Speaker 1: and empty space than your mind can comfortably picture. Small
• 1:05:49
  Speaker 1: because it may represent only a portion of everything that exists.
• 1:05:53
  Speaker 1: And so you can return once more to the original question,
• 1:05:57
  Speaker 1: does the universe have an edge? Perhaps the observable universe
• 1:06:01
  Speaker 1: has a horizon, but that horizon is not a wall.
• 1:06:05
  Speaker 1: Does the whole universe have an edge? We do not know.
• 1:06:09
  Speaker 1: Could the universe be finite? Yes, in some models. Could
• 1:06:14
  Speaker 1: it be finite without a boundary? Yes. Could it be infinite? Yes.
• 1:06:20
  Speaker 1: That remains possible too. Could there be another way of
• 1:06:23
  Speaker 1: connecting space that you have never imagined? Perhaps. And perhaps
• 1:06:27
  Speaker 1: the most peaceful answer is not to force these possibilities
• 1:06:31
  Speaker 1: into a single conclusion. You can simply allow the universe
• 1:06:34
  Speaker 1: to remain larger than your certainty. You can rest beneath
• 1:06:38
  Speaker 1: the quiet sky and remember that you are safe. There
• 1:06:42
  Speaker 1: is nothing to do, There is nothing to solve tonight.
• 1:06:46
  Speaker 1: The galaxies do not need you to decide whether space
• 1:06:49
  Speaker 1: is finite. The stars do not need an answer. Light
• 1:06:53
  Speaker 1: continues travelling. Space continues expanding. Matter continues moving slowly through
• 1:07:00
  Speaker 1: the immense geometry of the cosmos. And somewhere beyond your
• 1:07:04
  Speaker 1: observable horizon, whatever the true shape of the universe may be,
• 1:07:09
  Speaker 1: reality continues without waiting for you to understand it. You
• 1:07:13
  Speaker 1: can let that thought become softer now. No final wall.
• 1:07:17
  Speaker 1: No final answer. Only a horizon, glowing faintly in the darkness,
• 1:07:23
  Speaker 1: marking not where the universe ends, but where your present
• 1:07:27
  Speaker 1: view begins to fade. And beyond that fading point there
• 1:07:31
  Speaker 1: may be more. More space. More time. More distant light.
• 1:07:36
  Speaker 1: More quiet possibilities. You do not need to follow them.
• 1:07:40
  Speaker 1: You can simply rest here, beneath your small patch of sky,
• 1:07:44
  Speaker 1: while the unseen universe continues gently around you. And so,
• 1:07:52
  Speaker 1: our journey quietly comes to an end. You don't need
• 1:07:55
  Speaker 1: to know whether the universe is finite, curved or infinite.
• 1:07:59
  Speaker 1: Just let the question drift away now, beyond the horizon
• 1:08:03
  Speaker 1: of your thoughts. The stars will keep shining, galaxies will
• 1:08:07
  Speaker 1: keep moving, and space will continue in whatever shape it
• 1:08:11
  Speaker 1: has always held. You are safe. There is nothing to do.
• 1:08:16
  Speaker 1: Just breathe slowly, close your eyes, and rest beneath the
• 1:08:20
  Speaker 1: endless sky, and somewhere far beyond what you can see,
• 1:08:24
  Speaker 1: the universe quietly goes on. Good night.