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WHY HUMANITY MAY NEVER ESCAPE THE SOLAR SYSTEM · Boring Science

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  Speaker 1: Hello, and welcome to Boring Science to Sleep, a quiet
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  Speaker 1: place where science becomes slow, soft, and easy to drift through. Tonight,
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  Speaker 1: you are going to gently explore one of the largest
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  Speaker 1: questions we can ask about our future, why humanity may
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  Speaker 1: never truly leave the solar system. Not to solve the
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  Speaker 1: question tonight, and not to understand every detail, but simply
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  Speaker 1: to notice the enormous distances between one world and another. slowly, calmly,
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  Speaker 1: one quiet step at a time. Before you settle in,
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  Speaker 1: if you truly enjoy these calm journeys through interesting facts
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  Speaker 1: about science, you're welcome to like this video and subscribe,
• 0:43
  Speaker 1: only if it feels right for you. And when you're ready,
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  Speaker 1: let me know in the comments where you're listening from
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  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
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  Speaker 1: here together. Now, Dim the lights, let the room become
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  Speaker 1: a little quieter, perhaps let a fan hum softly somewhere nearby,
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  Speaker 1: and allow yourself to become comfortable. There is nothing to do,
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  Speaker 1: you are safe, you can simply listen and drift, and
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  Speaker 1: for a little while you can imagine that you are
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  Speaker 1: slowly leaving Earth behind. You begin somewhere very familiar, perhaps
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  Speaker 1: standing beneath a night sky, looking upward, watching the stars
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  Speaker 1: appear one by one, as the last traces of daylight disappear.
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  Speaker 1: From here, space looks almost peaceful enough to touch. The
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  Speaker 1: moon hangs above you, bright and pale, close enough to
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  Speaker 1: feel familiar. The stars look even closer. They are only
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  Speaker 1: points of light, tiny and calm, scattered across the darkness.
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  Speaker 1: And yet, your eyes are quietly hiding something from you.
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  Speaker 1: They are hiding distance. Human beings are very good at
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  Speaker 1: understanding the world around them. You can look across a
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  Speaker 1: room and understand what it means to be far away.
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  Speaker 1: You can look toward a mountain and sense the distance
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  Speaker 1: between yourself and its slopes. You can imagine walking across
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  Speaker 1: a city, crossing a valley, perhaps even travelling across an ocean.
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  Speaker 1: But eventually, the distances become so large that your intuition
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  Speaker 1: simply gives up. A thousand kilometres is already difficult to picture.
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  Speaker 1: A million kilometres becomes something more abstract. A billion kilometres
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  Speaker 1: becomes almost impossible to hold in the mind. You can
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  Speaker 1: say the number, you can hear the number, but you
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  Speaker 1: cannot easily feel it. And this is one of the
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  Speaker 1: quiet problems with space. When something is very far away,
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  Speaker 1: and then a million times farther away, both distances can
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  Speaker 1: begin to feel exactly the same. Very far. And yet
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  Speaker 1: they are not the same at all. So instead of
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  Speaker 1: trying to imagine the numbers, you can imagine yourself moving.
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  Speaker 1: Very slowly, you rise away from Earth. The familiar blue
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  Speaker 1: curve of the planet begins to shrink beneath you. The
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  Speaker 1: atmosphere becomes a thin, almost invisible layer. The oceans become darker,
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  Speaker 1: the continents become smaller, and then Earth becomes something you
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  Speaker 1: can hold in your imagination as a single round world,
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  Speaker 1: floating quietly in the blackness. You continue outward. The moon
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  Speaker 1: is behind you now, Its pale surface becomes a small sphere,
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  Speaker 1: and then a distant point. You keep going. Mars waits
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  Speaker 1: much farther away, sometimes relatively close, sometimes much farther, always
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  Speaker 1: moving in its own slow path around the sun. Beyond
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  Speaker 1: Mars are the giant planets, immense worlds wrapped in clouds,
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  Speaker 1: surrounded by moons and rings. And then, farther still, there
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  Speaker 1: is Pluto. From Earth, Pluto is almost impossible to picture
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  Speaker 1: as a destination. It is simply another tiny world moving
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  Speaker 1: through the outer darkness. But imagine that you continue. You
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  Speaker 1: do not stop at Pluto. You keep drifting outward, leaving
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  Speaker 1: the familiar planets behind. The Sun begins to look smaller.
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  Speaker 1: The planets become increasingly separated from one another. The solar system,
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  Speaker 1: which once seemed like a collection of worlds gathered around
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  Speaker 1: a single star, begins to feel more like an enormous
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  Speaker 1: field of darkness, with a few distant objects scattered through it.
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  Speaker 1: And this is only the beginning, because the solar system
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  Speaker 1: does not simply end where the planets end. Far beyond
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  Speaker 1: them lies a vast region called the Oort Cloud. You
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  Speaker 1: do not need to picture it as a solid shell.
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  Speaker 1: There is no wall there, no gate, no line painted
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  Speaker 1: across space telling you that you have arrived at the edge. Instead,
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  Speaker 1: The solar system simply becomes thinner and quieter. Objects become
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  Speaker 1: more distant. The sun's influence becomes weaker. The familiar neighbourhood
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  Speaker 1: of planets is far behind you. And the farther you travel,
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  Speaker 1: the more difficult it becomes to decide where the solar
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  Speaker 1: system truly ends. This is one of the strange things
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  Speaker 1: about leaving home. There is no moment when the universe
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  Speaker 1: gently announces that you are finished with the place you
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  Speaker 1: came from. You simply continue outward. and outward, and outward.
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  Speaker 1: The distance grows quietly beneath you. If you were travelling
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  Speaker 1: with one of the fastest spacecraft humanity has ever built,
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  Speaker 1: you might feel, at first, that the journey was becoming manageable.
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  Speaker 1: Human beings have already reached extraordinary speeds. Astronauts returning from
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  Speaker 1: the moon travelled at roughly 40,000 kilometres every hour. That
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  Speaker 1: sounds enormous when you compare it with anything moving on Earth.
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  Speaker 1: But space has a strange way of making enormous numbers
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  Speaker 1: feel small. The fastest human-made spacecraft have travelled more than 600,000
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  Speaker 1: kilometres every hour. At such a speed, the distance around
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  Speaker 1: Earth could be crossed in only a few minutes. The
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  Speaker 1: Moon would seem surprisingly close. Mars could become a journey
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  Speaker 1: measured in weeks rather than many months. Even Pluto could
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  Speaker 1: be reached in roughly a year in this simple imagined journey.
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  Speaker 1: For a moment, it sounds almost comfortable. Humanity becomes faster.
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  Speaker 1: The planets become reachable. The solar system begins to feel smaller.
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  Speaker 1: But then you look farther away. Much farther. You look
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  Speaker 1: toward the outer edge of the Oort cloud. And even
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  Speaker 1: at this extraordinary speed, the journey could still take roughly
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  Speaker 1: two and a half thousand years. Two and a half
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  Speaker 1: thousand years. Long enough for languages to change. For cities
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  Speaker 1: to disappear and be replaced. For entire civilisations to rise,
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  Speaker 1: transform and fade. Long enough for the people who began
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  Speaker 1: the journey to become ancient history many times over. And yet,
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  Speaker 1: you would still be travelling through the outer reaches of
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  Speaker 1: your own solar system. The strange part is not that
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  Speaker 1: the spacecraft is slow. The spacecraft is unimaginably fast. The
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  Speaker 1: strange part is that the solar system is unimaginably large.
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  Speaker 1: You have not failed to build a fast enough machine.
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  Speaker 1: You have simply begun to see the scale of the
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  Speaker 1: place you are trying to leave. And perhaps this is
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  Speaker 1: the first quiet lesson of the journey. The solar system
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  Speaker 1: does not feel like a prison because there is a
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  Speaker 1: wall around it. It feels difficult to leave because there
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  Speaker 1: is so much nothing between one meaningful place and another.
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  Speaker 1: You can look back now. The sun is smaller than
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  Speaker 1: it was. Earth is somewhere behind you. hidden among the darkness.
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  Speaker 1: The planets are scattered across an enormous, invisible landscape, and
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  Speaker 1: ahead of you there is no welcoming road, only more space,
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  Speaker 1: more darkness, more distance. You continue drifting, without hurry. There
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  Speaker 1: is nothing you need to reach tonight, nothing you need
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  Speaker 1: to solve. The stars can remain where they are, and
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  Speaker 1: as you rest here, perhaps you can let that first
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  Speaker 1: enormous distance become a little easier to feel, not as
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  Speaker 1: a number, but as a quiet space stretching gently between
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  Speaker 1: you and home. Because the farther you go, the more
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  Speaker 1: the meaning of speed begins to change, and somewhere beyond
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  Speaker 1: the familiar planets, another question is waiting very softly in
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  Speaker 1: the darkness. Not how far you can go, but how
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  Speaker 1: fast you can possibly get there. There is something comforting
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  Speaker 1: about speed. On Earth, speed usually means that a distance
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  Speaker 1: can disappear more quickly. A road that takes an hour
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  Speaker 1: becomes a road that takes 30 minutes. A journey that
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  Speaker 1: once required a day can become a journey of a
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  Speaker 1: few hours. The faster you move, the smaller the distance seems.
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  Speaker 1: And perhaps that is why, when you imagine humanity travelling
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  Speaker 1: to the stars, the first solution feels almost obvious. We
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  Speaker 1: simply need to go faster. So let yourself drift back
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  Speaker 1: into that thought for a moment. Imagine that you are
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  Speaker 1: inside a spacecraft, floating gently in a quiet cabin, with
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  Speaker 1: nothing pressing against your body except the soft pull of
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  Speaker 1: your own seat. The engines are somewhere behind you, the
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  Speaker 1: instruments glow faintly, and outside the window, Earth is becoming smaller.
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  Speaker 1: Humanity has already learned how to move extraordinarily quickly through space.
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  Speaker 1: When astronauts returned from the moon in 1969, they were
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  Speaker 1: travelling at roughly 40,000 kilometres every hour. That is difficult
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  Speaker 1: to imagine from the surface of Earth. It is many
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  Speaker 1: times faster than a passenger airplane. It is faster than
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  Speaker 1: almost anything you normally see moving across the ground. And yet,
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  Speaker 1: compared with the scale of the solar system, it is
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  Speaker 1: still gentle, still slow, still almost like taking a very
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  Speaker 1: small step into a very large room. So imagine that
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  Speaker 1: humanity keeps improving. Imagine that, Instead of relying only on
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  Speaker 1: the spacecraft that carried people to the moon, you are
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  Speaker 1: travelling on something far more powerful, something like the Parker
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  Speaker 1: Solar Probe. The Parker Solar Probe was designed to travel
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  Speaker 1: extraordinarily close to the Sun, using the Sun's gravity, together
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  Speaker 1: with carefully planned passes by Venus, to reshape its orbit
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  Speaker 1: and gain tremendous speed. It has become the fastest human-made
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  Speaker 1: object ever recorded. At its highest speeds, it has travelled
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  Speaker 1: at more than 600,000 kilometres every hour. More than 600,000.
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  Speaker 1: Just allow the number to float past you. You do
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  Speaker 1: not need to calculate it. You do not need to
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  Speaker 1: hold it in your mind. Just imagine the motion. At
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  Speaker 1: that speed, you could circle the Earth in only a
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  Speaker 1: few minutes. The distance between Earth and the Moon would
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  Speaker 1: take less than an hour. Humanity's fastest machine would glide
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  Speaker 1: across those familiar distances almost effortlessly. And now, imagine placing
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  Speaker 1: a human crew inside a spacecraft moving just as quickly.
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  Speaker 1: You leave Earth, the planet falls behind, the moon passes
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  Speaker 1: quietly in the distance, and the spacecraft continues outward. At
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  Speaker 1: this imagined constant speed, Mars could be reached in roughly
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  Speaker 1: two weeks. Two weeks. A journey that today's spacecraft normally
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  Speaker 1: experience over many months has suddenly become much shorter. For
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  Speaker 1: a moment, the solar system begins to feel smaller. Perhaps
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  Speaker 1: this is how humanity eventually escapes. Perhaps we only need
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  Speaker 1: better engines, better materials, better navigation, better ways of using
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  Speaker 1: the gravity of planets and stars. Perhaps speed really can
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  Speaker 1: solve the problem. So you keep going. Mars is behind
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  Speaker 1: you now. You continue toward the outer solar system. The
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  Speaker 1: sun is still bright, but its light feels slightly more distant.
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  Speaker 1: The enormous planets are scattered around you. Jupiter, Saturn, Uranus, Neptune,
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  Speaker 1: and farther out still, Pluto. At this imagined speed, Pluto
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  Speaker 1: could be reached in roughly a year. A year sounds
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  Speaker 1: long when you are thinking about an ordinary journey. But
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  Speaker 1: in the context of space … A year begins to
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  Speaker 1: feel surprisingly short. You could leave Earth this year and,
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  Speaker 1: in another year, find yourself beside a tiny distant world
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  Speaker 1: at the edge of the planetary region. You might look
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  Speaker 1: back toward the sun and see it shining as a
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  Speaker 1: small bright star. And perhaps you would think, we are
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  Speaker 1: almost there. But there is a subtle problem with the
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  Speaker 1: word there. Because Pluto is not the edge of the
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  Speaker 1: solar system. Not really. Beyond the planets, the sun's influence continues.
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  Speaker 1: Farther out, you pass a region called the heliopause, where
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  Speaker 1: the outward flow from the sun becomes much weaker and
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  Speaker 1: the surrounding interstellar environment begins to matter more. Voyager 2
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  Speaker 1: has already crossed this distant boundary after more than five
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  Speaker 1: decades of travel. But even Voyager's journey is only a
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  Speaker 1: small beginning when compared with the full extent of the
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  Speaker 1: solar system. You continue. You leave the planets behind. You
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  Speaker 1: pass the distant path of Voyager 2. The sun is
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  Speaker 1: now only a tiny light behind you. And then you
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  Speaker 1: begin moving towards something much more difficult to imagine. The
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  Speaker 1: Oort Cloud. It is not a solid shell. You would
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  Speaker 1: not suddenly fly through a visible wall of ice. Instead,
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  Speaker 1: it is an enormous, diffuse region containing distant icy objects,
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  Speaker 1: extending far beyond the familiar planets. It is so far
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  Speaker 1: away that the solar system begins to lose the feeling
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  Speaker 1: of being a collection of worlds. There is simply more darkness,
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  Speaker 1: more space, more distance. And now something strange happens. You
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  Speaker 1: are travelling at more than 600,000 kilometres every hour. You
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  Speaker 1: are moving faster than any human-made object has ever moved.
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  Speaker 1: And yet, reaching the far outer edge of the Oort Cloud,
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  Speaker 1: could still take roughly two and a half thousand years.
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  Speaker 1: Two and a half thousand years. You could almost watch
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  Speaker 1: history changing while you travel. The world you left behind
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  Speaker 1: would pass through countless generations. Languages could transform. Borders could disappear.
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  Speaker 1: Cities could be abandoned and rebuilt. Technology could become unrecognisable.
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  Speaker 1: And still, your spacecraft would be moving outward, still crossing
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  Speaker 1: the solar system. still surrounded mostly by darkness. This is
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  Speaker 1: where speed begins to reveal its strange secret. On Earth,
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  Speaker 1: making something faster makes a journey feel smaller. In space,
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  Speaker 1: making something faster sometimes only allows you to see how
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  Speaker 1: large the journey really is. The Parker Solar Probe is
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  Speaker 1: not slow. It is astonishingly fast. The spacecraft carrying you
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  Speaker 1: in this quiet thought experiment is not slow either. It
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  Speaker 1: is moving at a speed that would be almost unimaginable
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  Speaker 1: on Earth. But the solar system is larger still, and
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  Speaker 1: perhaps that is the more unsettling part. The problem is
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  Speaker 1: not simply that humanity has failed to build a fast
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  Speaker 1: enough spacecraft. The problem is that even our greatest speeds
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  Speaker 1: can become small when placed beside cosmic distances. You can
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  Speaker 1: continue drifting outward now, the sun behind you, the planets
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  Speaker 1: far behind you, Earth farther still. The light from home
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  Speaker 1: takes longer and longer to reach you. There is no road,
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  Speaker 1: no sign, no final boundary appearing ahead, only the slow,
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  Speaker 1: immense unfolding of distance. And if you were willing to
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  Speaker 1: give your spacecraft an even greater gift, if you could
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  Speaker 1: somehow push it beyond anything our current machines can achieve,
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  Speaker 1: perhaps the journey could become shorter still, much shorter. Perhaps
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  Speaker 1: for the first time, The stars themselves could begin to
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  Speaker 1: look like destinations rather than distant points of light. But
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  Speaker 1: even that hopeful thought carries a quiet question with it.
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  Speaker 1: How fast could you really go? And what happens when
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  Speaker 1: you begin approaching a speed that nature itself seems unwilling
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  Speaker 1: to let you cross? You are still drifting through the darkness,
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  Speaker 1: with the sun far behind you. The planets have become
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  Speaker 1: distant memories now, Small worlds scattered across an enormous region
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  Speaker 1: of space, and the question from before is still quietly
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  Speaker 1: following you. How fast could you possibly go? Perhaps much
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  Speaker 1: faster than anything humanity has built so far. So, for
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  Speaker 1: a little while, let yourself imagine that the future has
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  Speaker 1: already arrived. Imagine a spacecraft unlike any spacecraft that exists today.
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  Speaker 1: Its engines are powerful beyond anything you have seen. Its
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  Speaker 1: materials are stronger. Its computers are quieter and more capable.
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  Speaker 1: Its systems can repair themselves. And somehow, through technologies that
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  Speaker 1: do not yet belong to your time, this spacecraft can
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  Speaker 1: accelerate until it is travelling at about one-fifth of the
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  Speaker 1: speed of light. You do not need to think about
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  Speaker 1: the engineering. You do not need to calculate anything. Just
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  Speaker 1: imagine the feeling. The spacecraft moves forward. At first, the
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  Speaker 1: stars seem almost unchanged. Then the motion becomes unmistakable. The
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  Speaker 1: darkness begins to flow around you. The distant points of
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  Speaker 1: light appear to shift more quickly. And behind you, the
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  Speaker 1: solar system begins to fall away, one-fifth of the speed
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  Speaker 1: of light. That is an astonishing speed. Light itself travels
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  Speaker 1: so quickly that, in the time it takes you to
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  Speaker 1: take a single breath, it can travel hundreds of thousands
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  Speaker 1: of kilometres. your imagined spacecraft would be moving at a
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  Speaker 1: substantial fraction of that extraordinary speed. And suddenly, the distances
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  Speaker 1: that seemed impossible in the previous journey begin to change.
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  Speaker 1: The outer solar system becomes much more approachable. The long
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  Speaker 1: journey toward the distant Oort cloud is no longer measured
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  Speaker 1: in thousands of years. Instead, it could become a journey
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  Speaker 1: measured in years. And the nearest stars begin to feel
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  Speaker 1: different too, They are no longer simply lights in the
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  Speaker 1: night sky. They become places, destinations, something you could actually
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  Speaker 1: travel toward. This is where future propulsion begins to become interesting.
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  Speaker 1: One possibility scientists have considered is nuclear fusion, the process
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  Speaker 1: that powers the sun and other stars, where light atomic
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  Speaker 1: nuclei combine and release tremendous amounts of energy. You can
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  Speaker 1: imagine it simply as a way of unlocking an enormous
• 19:26
  Speaker 1: store of energy from very small amounts of matter. Another possibility,
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  Speaker 1: much more extreme, involves antimatter. Antimatter is not a magical fuel.
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  Speaker 1: It is a form of matter with properties opposite to
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  Speaker 1: ordinary matter, and when matter and antimatter meet, their mass
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  Speaker 1: can be converted into energy with extraordinary efficiency. These ideas
• 19:50
  Speaker 1: remain extraordinarily difficult to turn into practical spacecraft engines, but
• 19:56
  Speaker 1: tonight you do not need to solve that problem. For
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  Speaker 1: this quiet thought experiment, you can simply imagine that humanity
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  Speaker 1: eventually finds a way Perhaps the spacecraft carries its own
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  Speaker 1: powerful energy source. Perhaps energy is somehow transmitted toward it
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  Speaker 1: from far behind. Perhaps some technology that has not yet
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  Speaker 1: been invented changes the entire meaning of propulsion. For now,
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  Speaker 1: you can give humanity every advantage. The ship is fast.
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  Speaker 1: The ship is strong. The navigation systems are precise. The
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  Speaker 1: life support systems can keep you alive for decades. and
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  Speaker 1: you begin your journey toward the nearest stellar neighbourhood, Alpha Centauri.
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  Speaker 1: The name has appeared in human astronomy for generations, but
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  Speaker 1: now you are actually moving toward it. It is roughly
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  Speaker 1: four and a quarter light-years away. That phrase, light-year, sounds
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  Speaker 1: almost like a measurement of time, but it is really
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  Speaker 1: a measurement of distance. It means the distance light itself
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  Speaker 1: travels in one year. Even then, the number remains difficult
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  Speaker 1: to feel. Four years of light travelling through darkness. Four
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  Speaker 1: years of an invisible journey. And your spacecraft is moving
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  Speaker 1: extraordinarily quickly. At roughly one-fifth of the speed of light,
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  Speaker 1: a simplified journey to Alpha Centauri would still take about
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  Speaker 1: twenty years. Twenty years. You might leave while you are
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  Speaker 1: young and arrive after an entirely different chapter of your
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  Speaker 1: life has passed. Children could grow into adults during the journey.
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  Speaker 1: Cities on earth could change. Languages could shift. The technology
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  Speaker 1: you remember from home might already seem old. But twenty
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  Speaker 1: years is still something a civilization can imagine. It is
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  Speaker 1: no longer thousands of years. It is no longer an
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  Speaker 1: impossible distance in the ordinary sense. And so, for a moment,
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  Speaker 1: the future looks hopeful. Perhaps this is how humanity eventually
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  Speaker 1: leaves the solar system. Perhaps we only need to become
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  Speaker 1: extraordinarily good at moving very quickly. Perhaps the stars are difficult,
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  Speaker 1: but not unreachable. You continue drifting toward Alpha Centauri in
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  Speaker 1: your imagined spacecraft. The sun is now far behind. Its
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  Speaker 1: light is still reaching you, but it feels increasingly distant.
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  Speaker 1: The planets are gone from view. The space around you
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  Speaker 1: is almost completely dark, and there is something beautiful about
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  Speaker 1: this imagined journey. You are no longer crossing a planetary neighbourhood,
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  Speaker 1: you are crossing the space between stars. The emptiness itself
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  Speaker 1: becomes the landscape. There are no oceans beneath you, no mountains,
• 22:45
  Speaker 1: no roads, no clouds, only darkness, faint starlight, and the
• 22:51
  Speaker 1: quiet movement of your spacecraft. For a while, everything seems simple.
• 22:56
  Speaker 1: You have solved the problem of speed. You have taken
• 23:00
  Speaker 1: the extraordinary speed of humanity's fastest spacecraft and imagined something
• 23:05
  Speaker 1: vastly greater. You have turned millennia into years. You have
• 23:10
  Speaker 1: turned the stars from distant lights into possible destinations. And yet,
• 23:16
  Speaker 1: there is something you have not considered. You have made
• 23:19
  Speaker 1: the spacecraft incredibly fast. But you have not made space empty.
• 23:24
  Speaker 1: Because the darkness between the stars is not perfectly empty.
• 23:28
  Speaker 1: There are tiny particles drifting there. Atoms. Dust. Fragments of
• 23:34
  Speaker 1: material left behind by stars and planets. Most of them
• 23:38
  Speaker 1: are so small that you would never notice them. You
• 23:41
  Speaker 1: could pass through the darkness for a very long time
• 23:43
  Speaker 1: without seeing a single one. But at one-fifth of the
• 23:47
  Speaker 1: speed of light, seeing them may not be necessary. You
• 23:51
  Speaker 1: only need to meet one. At ordinary speeds, a tiny
• 23:54
  Speaker 1: grain of dust is almost nothing. At extraordinary speeds, the
• 23:59
  Speaker 1: same tiny grain becomes something very different. The faster you move,
• 24:03
  Speaker 1: the more energy a collision can release. And now the
• 24:07
  Speaker 1: very speed that seemed to solve the problem of distance
• 24:10
  Speaker 1: begins to create another problem. Your spacecraft is moving faster
• 24:14
  Speaker 1: than ever. The stars are getting closer. But the darkness
• 24:18
  Speaker 1: ahead is no longer entirely harmless. Somewhere in front of you,
• 24:23
  Speaker 1: Too small for your eyes to see, a single particle
• 24:27
  Speaker 1: may already be drifting through the path of your journey.
• 24:30
  Speaker 1: You continue forward, quietly, weightlessly, at an astonishing speed, and
• 24:37
  Speaker 1: the darkness remains still. For the next moment of the journey,
• 24:42
  Speaker 1: you can simply rest with that thought, because the greatest
• 24:45
  Speaker 1: danger may not be something large waiting among the stars,
• 24:49
  Speaker 1: it may be something almost unimaginably small. The particle ahead
• 24:56
  Speaker 1: of you is too small to see. You would not
• 24:59
  Speaker 1: notice it through the window. There is no warning light.
• 25:03
  Speaker 1: No distant object appears against the stars. There is only darkness,
• 25:08
  Speaker 1: almost perfectly quiet, while your spacecraft continues moving at an
• 25:12
  Speaker 1: extraordinary fraction of the speed of light. You might imagine
• 25:16
  Speaker 1: that space is empty, and in one sense it almost is,
• 25:21
  Speaker 1: compared with the crowded air around you on Earth. The
• 25:24
  Speaker 1: space between the stars contains almost nothing. But almost nothing
• 25:29
  Speaker 1: is not the same as nothing. There are atoms drifting
• 25:32
  Speaker 1: through the darkness. There are tiny grains of dust. There
• 25:36
  Speaker 1: are fragments left behind by ancient stars, by old collisions,
• 25:41
  Speaker 1: by worlds that formed and changed long before you arrived.
• 25:45
  Speaker 1: They are incredibly sparse. Sometimes, your spacecraft could travel an
• 25:50
  Speaker 1: enormous distance without encountering anything large enough to matter. And yet,
• 25:55
  Speaker 1: when you are moving this quickly, you do not need
• 25:58
  Speaker 1: very much matter for the journey to become difficult. Imagine
• 26:01
  Speaker 1: holding a single grain of sand in your hand. It
• 26:05
  Speaker 1: feels almost weightless. You could brush it away with your fingertip.
• 26:09
  Speaker 1: You could let it fall between your fingers and barely notice.
• 26:13
  Speaker 1: Now imagine that same grain moving toward you at a
• 26:16
  Speaker 1: substantial fraction of the speed of light. It is still
• 26:20
  Speaker 1: only a grain of sand. Its size has not changed.
• 26:24
  Speaker 1: Its weight has not suddenly become enormous, but the speed
• 26:27
  Speaker 1: has changed everything. The meeting between the grain and the
• 26:31
  Speaker 1: spacecraft would happen in an almost unimaginably short moment. The
• 26:36
  Speaker 1: energy carried by the moving particle would be released into
• 26:39
  Speaker 1: a very small area, and suddenly, something that seemed harmless
• 26:44
  Speaker 1: becomes something your spacecraft must respect. This is one of
• 26:48
  Speaker 1: the strange rules of deep space. Small does not always
• 26:52
  Speaker 1: mean harmless. not when speed becomes extreme. So you continue
• 26:57
  Speaker 1: drifting through the darkness. Ahead of you is an atom,
• 27:01
  Speaker 1: perhaps an atom of hydrogen, perhaps something heavier, perhaps a
• 27:06
  Speaker 1: tiny atom of iron. You do not see it. It
• 27:09
  Speaker 1: is far too small. But if it strikes the spacecraft
• 27:12
  Speaker 1: at such a high speed, it can behave less like
• 27:15
  Speaker 1: a gentle piece of matter and more like a microscopic projectile.
• 27:20
  Speaker 1: It can disturb the material it touches. It can break
• 27:24
  Speaker 1: apart atoms within the surface. It can leave a tiny
• 27:27
  Speaker 1: track of damage inside the structure of the spacecraft. One atom.
• 27:32
  Speaker 1: A particle too small to see. And yet, at these speeds,
• 27:37
  Speaker 1: even one particle can matter. Now imagine many more. Not
• 27:42
  Speaker 1: a cloud thick enough to see. Not a fog. Not
• 27:45
  Speaker 1: anything resembling weather. Just a faint population of microscopic particles
• 27:50
  Speaker 1: scattered through the interstellar darkness. Most of the time, there
• 27:55
  Speaker 1: would still be enormous amounts of empty space between them.
• 27:59
  Speaker 1: But your spacecraft is moving through all of that emptiness
• 28:02
  Speaker 1: at extraordinary speed. The faster you go, the more quickly
• 28:07
  Speaker 1: you sweep through the space ahead, and so the empty
• 28:10
  Speaker 1: universe begins to feel less empty. It becomes something like
• 28:14
  Speaker 1: an invisible ocean. You cannot see the water, you cannot
• 28:18
  Speaker 1: hear the waves, but every tiny particle is something you
• 28:21
  Speaker 1: are crossing through. And at a fifth of the speed
• 28:25
  Speaker 1: of light, even a microscopic encounter can become serious. Now
• 28:30
  Speaker 1: allow yourself to imagine something slightly larger, a grain of dust.
• 28:35
  Speaker 1: Perhaps it is no larger than a speck you might
• 28:38
  Speaker 1: find on a windowsill. On Earth, you could blow it
• 28:41
  Speaker 1: away with a breath. In space, at extreme speed, it
• 28:46
  Speaker 1: becomes something entirely different. When it strikes the spacecraft... The
• 28:50
  Speaker 1: impact can produce a flash of energy and heat. Material
• 28:54
  Speaker 1: can melt. Material can vaporise. A small region of the
• 28:58
  Speaker 1: protective surface can be damaged almost instantly. And the larger
• 29:03
  Speaker 1: the particle becomes, the more difficult the problem becomes. A
• 29:07
  Speaker 1: pebble would be worse. A larger fragment would be worse still.
• 29:11
  Speaker 1: And something roughly the size of a golf ball, moving
• 29:15
  Speaker 1: at such an extraordinary speed, could release an enormous amount
• 29:18
  Speaker 1: of energy when it collided with the spacecraft. You do
• 29:22
  Speaker 1: not need to picture the explosion. Instead, picture the quiet
• 29:26
  Speaker 1: before it. The spacecraft is moving. The cabin is still.
• 29:31
  Speaker 1: Perhaps you are resting against a seat. The stars are
• 29:34
  Speaker 1: distant points of light, and somewhere ahead, something is drifting
• 29:39
  Speaker 1: through the same darkness. You cannot see it. You cannot
• 29:43
  Speaker 1: steer around every microscopic particle. You cannot simply place a
• 29:47
  Speaker 1: road sign in space and ask the dust to move aside.
• 29:51
  Speaker 1: So you need protection. A spacecraft designed for such a
• 29:55
  Speaker 1: journey would need shielding, perhaps thick layers of material. perhaps
• 30:00
  Speaker 1: carefully designed surfaces that break incoming particles apart before they
• 30:04
  Speaker 1: reach the main structure. Perhaps several layers separated by empty spaces,
• 30:09
  Speaker 1: so that the first impact is absorbed before the energy
• 30:12
  Speaker 1: can travel deeper. The exact technology is a problem for engineers.
• 30:17
  Speaker 1: The basic idea is simple. If the darkness contains tiny
• 30:21
  Speaker 1: things that can hurt you, you build something strong enough
• 30:24
  Speaker 1: to stand between you and the darkness. But then another
• 30:28
  Speaker 1: quiet problem appears. Shielding has weight. The more material you carry,
• 30:33
  Speaker 1: the heavier the spacecraft becomes. And the heavier the spacecraft becomes,
• 30:38
  Speaker 1: the more energy you need to accelerate it. You wanted
• 30:42
  Speaker 1: more protection. Protection required more mass. More mass required more energy.
• 30:48
  Speaker 1: More energy meant a more demanding propulsion system. And so
• 30:52
  Speaker 1: the solution begins to fold back into the original problem.
• 30:56
  Speaker 1: This is something that appears again and again when you
• 30:59
  Speaker 1: think about interstellar travel. One difficulty rarely stands alone. You
• 31:05
  Speaker 1: solve one problem and the solution creates another. You want
• 31:09
  Speaker 1: to travel quickly because the stars are far away, but
• 31:13
  Speaker 1: travelling quickly makes collisions more destructive. You add shielding because
• 31:18
  Speaker 1: collisions are dangerous, but shielding adds mass. You add more
• 31:22
  Speaker 1: powerful engines because the spacecraft is heavier. But more powerful
• 31:26
  Speaker 1: engines require more energy. And then you are once again
• 31:29
  Speaker 1: looking for an even more advanced way to move. It
• 31:33
  Speaker 1: becomes a quiet circle. Distance asks for speed. Speed asks
• 31:38
  Speaker 1: for protection. Protection asks for energy. And energy asks for
• 31:43
  Speaker 1: technology that is far beyond anything humanity can easily build today. Still,
• 31:50
  Speaker 1: imagine that humanity somehow solves even this. Imagine that the
• 31:55
  Speaker 1: spacecraft becomes light enough, strong enough, protected enough. Imagine that
• 32:01
  Speaker 1: the dust between the stars no longer frightens you. The
• 32:04
  Speaker 1: journey continues. The darkness remains. The spacecraft moves onward. And
• 32:10
  Speaker 1: after everything you have done to make the journey possible,
• 32:13
  Speaker 1: one simple question begins to appear in the quiet. If
• 32:17
  Speaker 1: you can finally cross the darkness safely, what will be
• 32:20
  Speaker 1: waiting on the other side? Because reaching another star is
• 32:24
  Speaker 1: only the beginning. A star can be close, a planet
• 32:28
  Speaker 1: can be beautiful, a world can even appear promising from
• 32:32
  Speaker 1: millions of kilometres away. And still, it may not be
• 32:36
  Speaker 1: a place where you can live. For now, you can
• 32:39
  Speaker 1: simply let the spacecraft continue through the darkness, protected by
• 32:43
  Speaker 1: layers of material, surrounded by an almost empty universe. The
• 32:48
  Speaker 1: tiny particles remain out there, drifting silently. You move between them,
• 32:54
  Speaker 1: and somewhere ahead, beyond the invisible dust, a faint neighbouring
• 32:59
  Speaker 1: star waits in the distance. The spacecraft continues through the darkness.
• 33:07
  Speaker 1: The tiny particles are behind you now, or at least
• 33:10
  Speaker 1: you hope they are. The protective layers around your imagined
• 33:14
  Speaker 1: vessel remain quiet. The engines continue their patient work, and
• 33:19
  Speaker 1: somewhere ahead, slowly becoming more than a point of light,
• 33:23
  Speaker 1: Another star is waiting. For a long time, it is
• 33:27
  Speaker 1: only a faint glow, a tiny brightness among countless others.
• 33:32
  Speaker 1: But you know this one is different. This is not
• 33:35
  Speaker 1: simply a star you are looking at. This is a
• 33:38
  Speaker 1: star you are travelling toward. Alpha Centauri. It is one
• 33:42
  Speaker 1: of the nearest stellar systems to our Sun, only about
• 33:46
  Speaker 1: four and a quarter light-years away. That distance is still enormous.
• 33:51
  Speaker 1: But after everything you have imagined so far, 20 years
• 33:55
  Speaker 1: at roughly one-fifth of the speed of light, begins to
• 33:58
  Speaker 1: sound almost manageable. You have crossed the darkness. You have
• 34:03
  Speaker 1: protected the spacecraft. You have endured the years. And now,
• 34:08
  Speaker 1: at last, the destination begins to appear. The star grows brighter.
• 34:14
  Speaker 1: The darkness around it seems to change. You begin to
• 34:17
  Speaker 1: imagine planets moving through the distant light. you might feel
• 34:21
  Speaker 1: a small sense of relief. After all those years, you
• 34:25
  Speaker 1: have arrived somewhere else. But then you look more carefully,
• 34:29
  Speaker 1: and this is where the meaning of another star begins
• 34:32
  Speaker 1: to change. A star system can be close without being welcoming.
• 34:37
  Speaker 1: It can contain planets without containing a place for you
• 34:40
  Speaker 1: to live. It can be scientifically extraordinary without being a
• 34:44
  Speaker 1: second Earth. Alpha Centauri is a useful example because it
• 34:49
  Speaker 1: is so close to us. at least by the standards
• 34:52
  Speaker 1: of interstellar space. Its neighbourhood has become one of the
• 34:56
  Speaker 1: most interesting places for astronomers to study, especially the small
• 35:00
  Speaker 1: red star called Proxima Centauri, which is part of the
• 35:04
  Speaker 1: same stellar neighbourhood. Around Proxima Centauri, scientists have discovered planets.
• 35:11
  Speaker 1: Some of these worlds are fascinating because they exist at
• 35:14
  Speaker 1: distances from their star where temperatures might, under the right conditions,
• 35:19
  Speaker 1: allow liquid water to exist. And water matters. Liquid water
• 35:24
  Speaker 1: is one of the ingredients we associate strongly with life
• 35:27
  Speaker 1: as we know it. So you might hear the phrase,
• 35:30
  Speaker 1: habitable zone. It sounds promising. It sounds almost like an invitation.
• 35:36
  Speaker 1: But the phrase is much quieter than that. A habitable
• 35:39
  Speaker 1: zone does not mean a habitable planet. It does not
• 35:42
  Speaker 1: mean oceans. It does not mean forests. It does not
• 35:46
  Speaker 1: mean breathable air. It does not mean a surface where
• 35:50
  Speaker 1: you could step outside and feel a gentle breeze. It
• 35:54
  Speaker 1: simply describes a region around a star where, under suitable
• 35:58
  Speaker 1: atmospheric conditions, liquid water could potentially exist on the surface.
• 36:03
  Speaker 1: That is all. And that small distinction becomes enormous when
• 36:07
  Speaker 1: you are standing millions or billions of kilometres away from
• 36:11
  Speaker 1: the world you hope to reach. Imagine looking at a
• 36:14
  Speaker 1: planet from your spacecraft. From a distance it might appear beautiful.
• 36:19
  Speaker 1: A small sphere, illuminated by starlight. Perhaps there are colours
• 36:24
  Speaker 1: in its atmosphere. Perhaps clouds drift across its surface. Perhaps
• 36:29
  Speaker 1: the world reflects light in a way that reminds you
• 36:32
  Speaker 1: of Earth. But appearance is not enough. You would need
• 36:36
  Speaker 1: to know what the atmosphere is like. You would need
• 36:39
  Speaker 1: to know whether the surface pressure is suitable. You would
• 36:42
  Speaker 1: need to know whether the temperature remains within a range
• 36:45
  Speaker 1: that humans could tolerate. You would need to know whether
• 36:48
  Speaker 1: the planet has harmful radiation. You would need to know
• 36:52
  Speaker 1: whether its atmosphere is stable. You would need to know
• 36:55
  Speaker 1: whether water, if present, is actually accessible. And you would
• 36:59
  Speaker 1: need to know whether the planet remains friendly to life
• 37:02
  Speaker 1: over long periods of time. From far away, many of
• 37:06
  Speaker 1: these answers can be difficult to obtain, so the destination
• 37:09
  Speaker 1: remains uncertain. This is why Mars is such a useful
• 37:13
  Speaker 1: world to keep in mind. Mars is close, very close,
• 37:18
  Speaker 1: compared with another star. Humanity has sent spacecraft there many times.
• 37:24
  Speaker 1: We have watched its seasons. We have studied its surface.
• 37:28
  Speaker 1: We have found evidence that water once flowed across parts
• 37:31
  Speaker 1: of the planet. And yet, Mars is not a second Earth.
• 37:36
  Speaker 1: Its atmosphere is extremely thin. Its surface is cold. Its
• 37:41
  Speaker 1: environment offers little protection from the radiation that constantly travels
• 37:45
  Speaker 1: through space. A human settlement on Mars would need machines, habitats,
• 37:52
  Speaker 1: protective systems, and a constant supply of technology simply to
• 37:57
  Speaker 1: create conditions that Earth provides naturally. You can think about
• 38:01
  Speaker 1: that for a moment. A planet can be our neighbour.
• 38:05
  Speaker 1: It can contain water in some form. It can have mountains, valleys, dust, ice,
• 38:11
  Speaker 1: and ancient landscapes. It can be one of the most
• 38:14
  Speaker 1: interesting places humanity has ever explored. And still, it can
• 38:19
  Speaker 1: be deeply difficult to live there. Now move your imagination
• 38:23
  Speaker 1: back toward Alpha Centauri. You have spent 20 years reaching
• 38:27
  Speaker 1: this place. 20 years inside a spacecraft. 20 years of
• 38:32
  Speaker 1: recycled air. 20 years of artificial light. Twenty years of
• 38:38
  Speaker 1: maintaining the same small environment while the stars slowly changed
• 38:42
  Speaker 1: outside your window. And finally, you arrive, only to discover
• 38:47
  Speaker 1: that the nearest planetary system may not offer the kind
• 38:50
  Speaker 1: of world you were hoping for. That would not make
• 38:53
  Speaker 1: the journey meaningless. Science would still gain something extraordinary. You
• 38:58
  Speaker 1: would have reached another star. You would have learned about
• 39:02
  Speaker 1: planets that formed around another sun. You might discover geology, chemistry, atmospheres,
• 39:09
  Speaker 1: or perhaps even signs of something alive. The knowledge alone
• 39:13
  Speaker 1: could be priceless. But knowledge and settlement are different goals.
• 39:18
  Speaker 1: A place can teach you something without becoming your home.
• 39:22
  Speaker 1: And this distinction matters because humanity is not simply looking
• 39:25
  Speaker 1: for another planet. If the goal is to establish a
• 39:28
  Speaker 1: lasting civilization, beyond the solar system, you need more than
• 39:33
  Speaker 1: a world that is merely interesting. You need somewhere that
• 39:36
  Speaker 1: can support people. Somewhere with resources. Somewhere where machines can
• 39:42
  Speaker 1: operate for long periods. Somewhere where food can be produced.
• 39:47
  Speaker 1: Somewhere where human bodies can survive. and ideally, somewhere that
• 39:51
  Speaker 1: does not require an enormous artificial shell to replace every
• 39:56
  Speaker 1: basic condition of Earth. The closer you look, the more
• 40:00
  Speaker 1: demanding the requirements become. A world needs the right temperature,
• 40:05
  Speaker 1: the right kind of atmosphere, enough protection from harmful radiation,
• 40:10
  Speaker 1: accessible water, useful materials, and perhaps most importantly, enough stability
• 40:16
  Speaker 1: for a settlement to survive not merely for a few years,
• 40:20
  Speaker 1: but for generations. Nearby stars do not necessarily offer all
• 40:25
  Speaker 1: of this. Many of the stars around us are small
• 40:28
  Speaker 1: red stars. They are common in our galaxy, and some
• 40:32
  Speaker 1: have planets, but their environments can be very different from
• 40:36
  Speaker 1: the calm neighbourhood around our Sun. Some can produce powerful
• 40:40
  Speaker 1: bursts of activity. Some planets may orbit extremely close to
• 40:45
  Speaker 1: their stars. Some worlds may keep one side facing their
• 40:49
  Speaker 1: star for most of their orbit, creating environments very different
• 40:53
  Speaker 1: from the familiar rhythm of day and night on Earth.
• 40:56
  Speaker 1: None of this means that every nearby planet is hopeless.
• 41:00
  Speaker 1: It simply means that distance alone cannot tell you whether
• 41:03
  Speaker 1: a destination is useful. You could spend decades crossing the darkness,
• 41:08
  Speaker 1: only to arrive at another world that is almost as
• 41:11
  Speaker 1: difficult as Mars. and perhaps that is one of the
• 41:15
  Speaker 1: quietest problems with interstellar civilisation. The stars we can reach
• 41:20
  Speaker 1: first are not necessarily the stars we most want to reach.
• 41:25
  Speaker 1: The easiest destination may not be the best destination, and
• 41:28
  Speaker 1: the best destination may be much farther away. So you
• 41:32
  Speaker 1: remain there for a moment, looking toward the unfamiliar star.
• 41:37
  Speaker 1: It shines calmly. It does not know that you have
• 41:40
  Speaker 1: crossed twenty years of darkness to reach it, It offers
• 41:44
  Speaker 1: no promise, no welcome, no guarantee, just light. And perhaps
• 41:50
  Speaker 1: that is enough for tonight, because somewhere farther beyond this
• 41:53
  Speaker 1: small stellar neighbourhood, there may be worlds that are far
• 41:57
  Speaker 1: more earth-like, worlds with deeper oceans, gentler climates, richer atmospheres,
• 42:04
  Speaker 1: perhaps even the ingredients for life. But the farther you
• 42:08
  Speaker 1: search for those worlds, the larger the journey becomes. The
• 42:12
  Speaker 1: stars around you begin to form a larger map. The
• 42:16
  Speaker 1: nearest few lights become a small neighbourhood. And beyond that neighbourhood,
• 42:21
  Speaker 1: the galaxy opens quietly in every direction. There may be
• 42:25
  Speaker 1: countless destinations. But the question is no longer simply whether
• 42:29
  Speaker 1: they exist. The question is how long you would have
• 42:32
  Speaker 1: to travel to reach them. And when you begin measuring
• 42:35
  Speaker 1: that journey not in years but in generations, the meaning
• 42:39
  Speaker 1: of distance becomes something very different. The unfamiliar star ahead
• 42:46
  Speaker 1: of you is no longer alone. As you continue to
• 42:49
  Speaker 1: drift through the darkness, more faint lights begin to appear
• 42:53
  Speaker 1: around it. One star becomes several, several become dozens, and slowly,
• 43:00
  Speaker 1: the darkness begins to reveal something that was difficult to
• 43:03
  Speaker 1: see from Earth. You are not surrounded by an endless
• 43:07
  Speaker 1: number of nearby stars. The galaxy is enormous, but your
• 43:11
  Speaker 1: immediate neighbourhood is surprisingly small. Imagine drawing an invisible sphere
• 43:17
  Speaker 1: around the Sun, extending roughly 25 light-years across. By human standards,
• 43:23
  Speaker 1: this is an almost unimaginable volume of space. You could
• 43:27
  Speaker 1: spend your entire life travelling across a tiny part of it.
• 43:32
  Speaker 1: And yet, compared with the Milky Way, this neighbourhood is
• 43:35
  Speaker 1: almost nothing. It represents only around two hundredths of one
• 43:39
  Speaker 1: percent of our galaxy. a tiny bubble inside a galaxy
• 43:43
  Speaker 1: filled with hundreds of billions of stars. From far away,
• 43:48
  Speaker 1: the Milky Way looks crowded, a glowing river of stars,
• 43:52
  Speaker 1: a great spiral of light. But if you could move
• 43:56
  Speaker 1: close to the sun and then slowly zoom outward, the
• 43:59
  Speaker 1: picture would change, the stars would become separated, the darkness
• 44:04
  Speaker 1: between them would grow, and your own neighbourhood would begin
• 44:08
  Speaker 1: to look less like a city and more like a
• 44:11
  Speaker 1: handful of quiet lights, scattered across a very large night.
• 44:16
  Speaker 1: Within this small region, the source material counts 34 stars
• 44:20
  Speaker 1: and 6 brown dwarfs. Brown dwarfs are objects that formed
• 44:24
  Speaker 1: somewhat like stars, but never became massive enough to shine
• 44:28
  Speaker 1: like ordinary stars. You do not need to think of
• 44:31
  Speaker 1: them as destinations. For now, they are simply part of
• 44:35
  Speaker 1: the landscape around you. a small collection of objects drifting
• 44:39
  Speaker 1: through an enormous galaxy. And then you notice something else.
• 44:44
  Speaker 1: Only three of the stars in this neighbourhood are similar
• 44:47
  Speaker 1: to our Sun. One of those is the Sun itself.
• 44:50
  Speaker 1: Another is Alpha Centauri A. The rest are mostly different
• 44:54
  Speaker 1: kinds of stars, with many belonging to a class called
• 44:57
  Speaker 1: Red Dwarfs. Red Dwarfs are smaller and cooler than the Sun.
• 45:02
  Speaker 1: They are extremely common throughout the galaxy, and many of
• 45:05
  Speaker 1: them have planets. At first, this sounds encouraging. More stars.
• 45:11
  Speaker 1: More planets. More possible homes. Perhaps the answer is simply
• 45:15
  Speaker 1: to search carefully enough. You begin looking from one system
• 45:19
  Speaker 1: to another. A planet appears around a small red star.
• 45:23
  Speaker 1: Then another. Then another. Some of these planets occupy a
• 45:27
  Speaker 1: region where liquid water might exist under the right conditions.
• 45:31
  Speaker 1: That phrase sounds promising again. Liquid water. A comfortable temperature.
• 45:36
  Speaker 1: Perhaps an atmosphere. Perhaps clouds. Perhaps an ocean hidden beneath
• 45:41
  Speaker 1: the distant light. But you have already learned to be
• 45:44
  Speaker 1: careful with the word habitable. A habitable zone is only
• 45:48
  Speaker 1: a beginning. It tells you something about the amount of
• 45:51
  Speaker 1: energy a planet receives from its star. It does not
• 45:55
  Speaker 1: tell you what the atmosphere is made of. It does
• 45:58
  Speaker 1: not tell you whether the atmosphere is thick enough. It
• 46:01
  Speaker 1: does not tell you whether the surface is protected from radiations.
• 46:04
  Speaker 1: It does not tell you whether the planet has oceans.
• 46:08
  Speaker 1: And it certainly does not tell you whether you could
• 46:10
  Speaker 1: step onto the surface and breathe. Mars quietly reminds you
• 46:14
  Speaker 1: of this. Mars lies within the broad region around the
• 46:18
  Speaker 1: Sun where liquid water could, under suitable circumstances, exist. And yet,
• 46:24
  Speaker 1: Mars is not a comfortable second Earth. Its atmosphere is
• 46:28
  Speaker 1: extremely thin. Its surface is cold. Its environment is exposed
• 46:33
  Speaker 1: to radiation. A human settlement there would need to build
• 46:37
  Speaker 1: its own protection, its own enclosed spaces, its own carefully
• 46:42
  Speaker 1: maintained little islands of Earth-like conditions. So imagine discovering a
• 46:47
  Speaker 1: planet around another star. From your spacecraft window, it might
• 46:51
  Speaker 1: look almost perfect. You see a small world turning slowly
• 46:55
  Speaker 1: in the light. Perhaps it has clouds. Perhaps it has
• 46:59
  Speaker 1: a colour that reminds you of Earth. Perhaps the measurements
• 47:03
  Speaker 1: suggest that water might exist. And still, you cannot simply
• 47:07
  Speaker 1: assume that it is home. You would need to learn more.
• 47:12
  Speaker 1: Much more. This is where the size of the stellar
• 47:15
  Speaker 1: neighbourhood begins to matter. Because if one nearby world disappoints you,
• 47:20
  Speaker 1: perhaps another will be better. So you search again. And
• 47:24
  Speaker 1: perhaps you find another planet. It looks more promising. You
• 47:28
  Speaker 1: study it. And there are still uncertainties. Perhaps its gravity
• 47:32
  Speaker 1: is stronger than Earth's. Perhaps its atmosphere is too thick.
• 47:37
  Speaker 1: Perhaps its star is more active. Perhaps one side of
• 47:40
  Speaker 1: the planet receives far more energy than the other. Perhaps
• 47:44
  Speaker 1: water exists, but only beneath layers of ice. Perhaps the
• 47:48
  Speaker 1: planet is simply different in ways you cannot fully understand
• 47:51
  Speaker 1: from so far away. None of this means such worlds
• 47:55
  Speaker 1: are worthless. Quite the opposite. They could be among the
• 47:59
  Speaker 1: most fascinating places humanity ever discovers. They could teach you
• 48:03
  Speaker 1: how planets form. They could reveal strange climates. They could
• 48:08
  Speaker 1: contain chemistry unlike anything on Earth. They could even, perhaps,
• 48:13
  Speaker 1: offer signs of life. But scientific value and human habitability
• 48:18
  Speaker 1: are not the same thing. That distinction becomes more important
• 48:22
  Speaker 1: every time you imagine travelling for decades to reach a destination.
• 48:26
  Speaker 1: If you could send a small robotic probe, almost any
• 48:30
  Speaker 1: interesting world might be worth visiting. A probe does not
• 48:33
  Speaker 1: need breathable air. It does not need food. It does
• 48:37
  Speaker 1: not need a comfortable bed. It does not need a
• 48:40
  Speaker 1: supply of oxygen for 40 years. It can simply travel, observe,
• 48:46
  Speaker 1: collect information, and send its discoveries home. Human beings are different.
• 48:53
  Speaker 1: A human journey carries an entire fragile biological world inside it.
• 48:58
  Speaker 1: You need air, water, food, shelter, protection, medical care, reliable machines,
• 49:06
  Speaker 1: and time. So the question becomes increasingly difficult. How far
• 49:11
  Speaker 1: should you travel for a world that might be suitable?
• 49:14
  Speaker 1: If you stay within a relatively small neighbourhood, your journey
• 49:17
  Speaker 1: can remain within a scale that future technology might perhaps
• 49:21
  Speaker 1: make manageable. But the number of truly attractive destinations may
• 49:26
  Speaker 1: be small. If you expand the search, more possibilities appear.
• 49:31
  Speaker 1: Yet every expansion adds more distance. More years, more energy,
• 49:36
  Speaker 1: more uncertainty. And eventually … you reach a point where
• 49:40
  Speaker 1: the stars that seem most interesting may be so far
• 49:44
  Speaker 1: away that even travelling at a large fraction of the
• 49:47
  Speaker 1: speed of light would require hundreds or thousands of years.
• 49:51
  Speaker 1: You can imagine the map now. The sun is one
• 49:55
  Speaker 1: tiny point. Around it is a small bubble containing nearby stars.
• 50:00
  Speaker 1: Beyond that bubble is another layer, then another, then another.
• 50:05
  Speaker 1: Each time you widen the circle, the galaxy offers more possibilities.
• 50:09
  Speaker 1: But the journey grows with it. The neighbourhood becomes a province.
• 50:14
  Speaker 1: The province becomes a continent. And the continent becomes a world.
• 50:18
  Speaker 1: Except there is no road between them. There is only darkness.
• 50:23
  Speaker 1: And this is perhaps the quietest difficulty of all. The
• 50:27
  Speaker 1: universe may contain many places worth visiting. It may even
• 50:31
  Speaker 1: contain worlds that resemble Earth in ways we have not
• 50:35
  Speaker 1: yet imagined. But the worlds that are easiest to reach...
• 50:38
  Speaker 1: are not necessarily the worlds you most want, and the
• 50:42
  Speaker 1: worlds you most want may be waiting far beyond the
• 50:45
  Speaker 1: small neighbourhood surrounding the sun. So you drift there for
• 50:49
  Speaker 1: a moment, surrounded by distant stars. Thirty-four stars. Six brown dwarfs.
• 50:56
  Speaker 1: A tiny collection of lights inside an almost immeasurable galaxy.
• 51:01
  Speaker 1: It feels like a lot when you look at them
• 51:03
  Speaker 1: one by one, but when you look at the galaxy
• 51:06
  Speaker 1: as a whole, they almost disappear. And somewhere beyond them,
• 51:10
  Speaker 1: perhaps much farther away, another world may be turning beneath
• 51:14
  Speaker 1: another sky. A world with oceans. A world with an atmosphere.
• 51:20
  Speaker 1: A world that might be gentle enough to call home.
• 51:23
  Speaker 1: The difficulty is that you may have to travel an
• 51:26
  Speaker 1: extraordinarily long time to find it. And once distance becomes
• 51:30
  Speaker 1: hundreds of years, or thousands of years, the journey stops
• 51:35
  Speaker 1: being something that belongs to one human life. it begins
• 51:39
  Speaker 1: to belong to generations. The stars around you have become
• 51:44
  Speaker 1: a map. Some are close enough to imagine visiting. Others
• 51:48
  Speaker 1: are farther away, faint points of light that seem almost
• 51:52
  Speaker 1: unchanged no matter how long you look. And somewhere beyond
• 51:56
  Speaker 1: the small neighbourhood around the sun, there may be worlds
• 51:59
  Speaker 1: that are more promising than the ones nearby. Perhaps there
• 52:03
  Speaker 1: is a planet with a deep ocean. Perhaps there is
• 52:06
  Speaker 1: an atmosphere that could, with the right conditions, support life.
• 52:11
  Speaker 1: Perhaps there is a world that resembles Earth in ways
• 52:14
  Speaker 1: we have not yet discovered. But there is a quiet difficulty.
• 52:19
  Speaker 1: The farther away the destination becomes, the more the journey
• 52:23
  Speaker 1: belongs to time. You have already imagined travelling at roughly
• 52:27
  Speaker 1: one-fifth of the speed of light. That sounds impossibly fast.
• 52:32
  Speaker 1: And yet, even at such a speed, a destination dozens
• 52:36
  Speaker 1: of light-years away would still require decades. A destination hundreds
• 52:41
  Speaker 1: of light-years away would take much longer, and eventually you
• 52:46
  Speaker 1: reach distances where the journey is no longer something one
• 52:49
  Speaker 1: person could reasonably expect to complete. You would leave Earth,
• 52:53
  Speaker 1: you would travel, and you would grow old before the
• 52:56
  Speaker 1: destination appeared. So perhaps the spacecraft would need to carry
• 53:01
  Speaker 1: something more important than fuel. It would need to carry time,
• 53:05
  Speaker 1: Imagine stepping inside such a spacecraft. There is no launch
• 53:09
  Speaker 1: tower outside your window now. No familiar city. No ocean.
• 53:14
  Speaker 1: No forest. Only a carefully constructed interior, designed to remain
• 53:20
  Speaker 1: alive for a very long time. The lights are soft.
• 53:24
  Speaker 1: The air moves quietly through the ventilation system. Water is recycled.
• 53:29
  Speaker 1: Food is carefully stored or grown. Every machine has a purpose.
• 53:35
  Speaker 1: Every object has been chosen because someone, somewhere, imagined that
• 53:39
  Speaker 1: it might still be needed many years from now. You
• 53:43
  Speaker 1: begin the journey. At first, nothing seems unusual. A year passes.
• 53:49
  Speaker 1: Then another. The stars remain almost the same. You continue living.
• 53:54
  Speaker 1: You sleep. You wake. You eat. You look through the window.
• 53:59
  Speaker 1: And gradually, time begins to become part of the spacecraft itself.
• 54:04
  Speaker 1: Perhaps the people who designed the ship are no longer alive.
• 54:08
  Speaker 1: Perhaps the cities they knew have changed. Perhaps the Earth
• 54:12
  Speaker 1: they remembered has become a distant historical place. And still
• 54:16
  Speaker 1: the spacecraft continues. This is the basic idea behind a
• 54:20
  Speaker 1: generation ship. Instead of expecting the people who leave Earth
• 54:24
  Speaker 1: to arrive at the destination, the spacecraft becomes a home
• 54:28
  Speaker 1: for several generations. Children could be born during the journey.
• 54:32
  Speaker 1: Those children could grow old. Their children could continue the journey.
• 54:37
  Speaker 1: And eventually, perhaps descendants of the original travellers could arrive
• 54:41
  Speaker 1: at another star. It sounds strange because human journeys usually
• 54:46
  Speaker 1: belong to individual lives. You leave. You travel. You arrive.
• 54:52
  Speaker 1: But a generation ship changes that rhythm. The journey itself
• 54:56
  Speaker 1: becomes the destination for a very long time. The spacecraft
• 55:00
  Speaker 1: becomes a small moving world Inside it, people would need
• 55:04
  Speaker 1: to maintain not only machines, but an entire society. They
• 55:09
  Speaker 1: would need food. They would need water. They would need
• 55:12
  Speaker 1: places to live. They would need knowledge. They would need education.
• 55:17
  Speaker 1: They would need ways of repairing systems that might be
• 55:20
  Speaker 1: older than the people repairing them. And perhaps most importantly,
• 55:24
  Speaker 1: they would need a reason to continue. A journey lasting
• 55:28
  Speaker 1: decades is difficult to imagine. A journey lasting centuries is
• 55:33
  Speaker 1: something else entirely. The people who begin it may never
• 55:37
  Speaker 1: see the world they were trying to reach. And that
• 55:40
  Speaker 1: raises another possibility. Perhaps humans would not make the journey
• 55:44
  Speaker 1: in the form we know today. Perhaps machines would go first.
• 55:49
  Speaker 1: An autonomous spacecraft could travel without needing the same things
• 55:53
  Speaker 1: a human crew needs. It would not need a bedroom.
• 55:57
  Speaker 1: It would not need a kitchen. It would not need
• 55:59
  Speaker 1: a continuous supply of breathable air. It could sleep for
• 56:03
  Speaker 1: long periods. It could monitor itself. It could make decisions
• 56:07
  Speaker 1: without waiting for instructions from Earth. And, in some speculative ideas,
• 56:13
  Speaker 1: such a spacecraft might carry frozen embryos or genetic material
• 56:18
  Speaker 1: rather than adult humans. The machines would travel first, they
• 56:22
  Speaker 1: would arrive, they would prepare a suitable environment, and only
• 56:26
  Speaker 1: then perhaps would a new human population begin. This remains
• 56:31
  Speaker 1: highly speculative. The technology does not currently exist in the
• 56:35
  Speaker 1: form needed to make such a plan practical. But the
• 56:38
  Speaker 1: idea reveals something important. When distance becomes enormous, you begin
• 56:43
  Speaker 1: changing not only the spacecraft, but the meaning of what
• 56:47
  Speaker 1: it means to travel. Instead of carrying a person from
• 56:50
  Speaker 1: one place to another, you might carry the possibility of
• 56:53
  Speaker 1: a future person. Instead of transporting a civilisation, You might
• 56:58
  Speaker 1: transport the ingredients from which a new civilization could eventually grow.
• 57:04
  Speaker 1: And even then, another problem remains. Communication. Imagine that your
• 57:09
  Speaker 1: spacecraft has reached a planet 20 light-years away. You send
• 57:14
  Speaker 1: a message back toward Earth. The message travels at the
• 57:18
  Speaker 1: fastest speed nature allows. But Earth is 20 years away
• 57:22
  Speaker 1: in the other direction. You wait, and eventually, perhaps a
• 57:27
  Speaker 1: reply arrives. Twenty more years have passed. A simple conversation
• 57:32
  Speaker 1: could take decades. You ask a question. You wait twenty years.
• 57:37
  Speaker 1: Earth receives it. Someone answers. The answer travels back. Another
• 57:43
  Speaker 1: twenty years pass. By the time you receive the reply,
• 57:47
  Speaker 1: the person who sent the original message may have changed
• 57:50
  Speaker 1: completely or may no longer be alive. And that is
• 57:54
  Speaker 1: only twenty light years. Increase the distance. and the silence grows.
• 57:59
  Speaker 1: This means that an interstellar civilization could face a strange
• 58:03
  Speaker 1: kind of separation. You might have human communities around different stars.
• 58:09
  Speaker 1: They might share a common origin. They might share languages, memories, stories,
• 58:15
  Speaker 1: and perhaps even the same distant history. But they could
• 58:18
  Speaker 1: never communicate instantly. Each community would have to make decisions locally.
• 58:24
  Speaker 1: Each would develop according to its own circumstances. The farther
• 58:28
  Speaker 1: apart the communities became, the more independent they would become.
• 58:33
  Speaker 1: You could imagine a galaxy filled with small islands of
• 58:36
  Speaker 1: human life. Each island surrounded by darkness. Each able to
• 58:42
  Speaker 1: see the others. Each knowing that a message could cross
• 58:45
  Speaker 1: the space between them. But never quickly. This is different
• 58:49
  Speaker 1: from the civilizations you know on Earth. Here, a message
• 58:53
  Speaker 1: can cross a city in an instant. A conversation can
• 58:57
  Speaker 1: continue across an ocean almost without delay. On Earth, distance
• 59:02
  Speaker 1: is often something technology has learned to shrink. Between the stars,
• 59:06
  Speaker 1: distance remains stubborn. The message still needs time. The traveller
• 59:11
  Speaker 1: still needs time. And the civilization itself needs time. This
• 59:16
  Speaker 1: is why interstellar travel may be more than a question
• 59:19
  Speaker 1: of building a faster engine. It may be a question
• 59:22
  Speaker 1: of whether a civilization can survive long enough to use
• 59:26
  Speaker 1: that engine. Can it preserve knowledge? Can it maintain its machines?
• 59:31
  Speaker 1: Can it keep its societies stable? Can it accept that
• 59:35
  Speaker 1: the people who begin a journey may never see its destination?
• 59:39
  Speaker 1: Can it remain connected when a reply may take decades?
• 59:43
  Speaker 1: There are no simple answers, and perhaps you do not
• 59:46
  Speaker 1: need one tonight. You can simply imagine that little spacecraft
• 59:50
  Speaker 1: moving through the darkness. Inside, someone is sleeping. Someone is
• 59:55
  Speaker 1: watching a small screen. Someone is growing food beneath artificial light.
• 1:00:01
  Speaker 1: Someone is looking toward a star that still appears impossibly
• 1:00:05
  Speaker 1: far away. Years pass, then decades. The spacecraft continues. And
• 1:00:11
  Speaker 1: somewhere far behind, Earth continues too. Two places separated by
• 1:00:17
  Speaker 1: an ocean of darkness. Two places connected by light. And perhaps,
• 1:00:22
  Speaker 1: as you drift through this quiet thought, you begin to
• 1:00:25
  Speaker 1: understand— that the greatest distance between the stars may not
• 1:00:29
  Speaker 1: be measured only in kilometres or light-years. It may be
• 1:00:33
  Speaker 1: measured in generations, in memories, in the time between one
• 1:00:38
  Speaker 1: voice and another. And beyond that enormous stretch of time,
• 1:00:42
  Speaker 1: the galaxy remains quietly open, offering more stars, more worlds,
• 1:00:48
  Speaker 1: and more possibilities, but asking something very difficult in return, patience. Patience.
• 1:00:58
  Speaker 1: That may be the quietest word left with you now.
• 1:01:02
  Speaker 1: You have travelled a long way in your imagination. You
• 1:01:05
  Speaker 1: began on Earth, beneath a familiar sky. You watched the
• 1:01:09
  Speaker 1: planet become smaller. You passed the moon. You drifted beyond Mars,
• 1:01:15
  Speaker 1: beyond the giant planets, beyond Pluto, and toward the immense
• 1:01:19
  Speaker 1: outer regions of the solar system. You imagined humanity moving
• 1:01:24
  Speaker 1: faster than ever before, You imagined spacecraft travelling at a
• 1:01:28
  Speaker 1: remarkable fraction of the speed of light. You crossed the
• 1:01:32
  Speaker 1: invisible particles scattered between the stars. You protected the spacecraft
• 1:01:37
  Speaker 1: with layers of material. You arrived near another star. And
• 1:01:41
  Speaker 1: then you discovered that arriving somewhere is not the same
• 1:01:44
  Speaker 1: as finding somewhere to live. You searched the nearby stars.
• 1:01:48
  Speaker 1: You found planets. Some seemed promising. Some existed in regions
• 1:01:53
  Speaker 1: where liquid water might be possible. And yet, none could
• 1:01:57
  Speaker 1: simply be called another Earth. So you widened the search.
• 1:02:02
  Speaker 1: The neighbourhood became larger. The stars became more distant. And eventually,
• 1:02:07
  Speaker 1: the journey became longer than a human life. You imagined
• 1:02:11
  Speaker 1: generations living inside a spacecraft. You imagined machines travelling ahead.
• 1:02:17
  Speaker 1: You imagined messages taking decades to move between distant communities.
• 1:02:22
  Speaker 1: And after all of this, one conclusion seems almost unavoidable.
• 1:02:26
  Speaker 1: Leaving the solar system would be extraordinarily difficult, perhaps far
• 1:02:30
  Speaker 1: more difficult than humanity usually imagines. Our rockets are powerful
• 1:02:35
  Speaker 1: by earthly standards. Our computers are extraordinarily capable. Our spacecraft
• 1:02:40
  Speaker 1: can travel beyond the planets. We can land machines on
• 1:02:44
  Speaker 1: distant worlds. We can study planets around other stars without
• 1:02:48
  Speaker 1: ever visiting them. And yet, The scale of interstellar space
• 1:02:52
  Speaker 1: remains almost completely outside our ordinary experience. The distances are enormous.
• 1:02:59
  Speaker 1: The energy requirements are enormous. The dangers of travelling extremely
• 1:03:04
  Speaker 1: fast are real, and the most promising destinations may be
• 1:03:08
  Speaker 1: far beyond the small neighbourhood surrounding the Sun. Even if
• 1:03:12
  Speaker 1: we solve one difficulty, another quietly waits. More speed creates
• 1:03:17
  Speaker 1: harsher collisions. More shielding creates more mass. More mass demands
• 1:03:23
  Speaker 1: more energy. Longer journeys create biological and social problems. More
• 1:03:29
  Speaker 1: distant civilizations face longer communication delays. The pieces fit together
• 1:03:34
  Speaker 1: into a difficult picture. Not an impossible picture, but a
• 1:03:38
  Speaker 1: difficult one. And perhaps that distinction matters. Because there is
• 1:03:43
  Speaker 1: a temptation, when thinking about the future, to say that
• 1:03:47
  Speaker 1: something will never happen. Never. It is such a powerful word.
• 1:03:52
  Speaker 1: But history has often been uncomfortable with it. More than
• 1:03:55
  Speaker 1: a century ago, people were already wondering when humans might
• 1:03:59
  Speaker 1: build machines capable of powered flight. In 1903, a newspaper
• 1:04:05
  Speaker 1: editorial in the United States suggested that the problem might
• 1:04:09
  Speaker 1: require anywhere from 1 million to 10 million years to solve.
• 1:04:14
  Speaker 1: The estimate was wildly wrong. Only a short time later,
• 1:04:18
  Speaker 1: The Wright brothers successfully flew a powered aircraft. The difference
• 1:04:22
  Speaker 1: between prediction and reality was enormous. And this was not
• 1:04:26
  Speaker 1: because the laws of nature had changed. The laws had remained.
• 1:04:31
  Speaker 1: Human understanding had simply been incomplete. Technology had found a
• 1:04:35
  Speaker 1: path that was difficult to imagine beforehand. Decades later, humans
• 1:04:41
  Speaker 1: went farther still. In 1969, people walked on the moon.
• 1:04:46
  Speaker 1: Only 66 years had passed since the first successful powered flight.
• 1:04:50
  Speaker 1: 66 years. In the context of human history, that is
• 1:04:55
  Speaker 1: an incredibly short time. You can imagine someone in 1903
• 1:05:00
  Speaker 1: looking toward the sky. Perhaps powered flight seemed absurd. Perhaps
• 1:05:05
  Speaker 1: machines were too heavy. Perhaps engines were too weak. Perhaps
• 1:05:09
  Speaker 1: humans simply were not meant to fly. And then, within
• 1:05:13
  Speaker 1: a single human lifetime... The boundary had moved. So when
• 1:05:17
  Speaker 1: you look at interstellar travel today, perhaps you should be cautious.
• 1:05:22
  Speaker 1: The barriers are genuine. They are not merely pessimistic opinions.
• 1:05:27
  Speaker 1: The distances really are enormous. The speed of light really
• 1:05:30
  Speaker 1: does impose a fundamental limit on ordinary travel through space.
• 1:05:35
  Speaker 1: Matter between the stars really can become dangerous at extreme speeds.
• 1:05:40
  Speaker 1: Nearby planets really may be unsuitable for human settlement. and
• 1:05:44
  Speaker 1: maintaining a civilisation across many light years really would introduce
• 1:05:49
  Speaker 1: challenges unlike anything humanity has faced on Earth. These are
• 1:05:53
  Speaker 1: not problems that disappear simply because you wish for better technology,
• 1:05:57
  Speaker 1: but the future is not required to use the technology
• 1:06:00
  Speaker 1: you can imagine today. Perhaps one day humanity will develop
• 1:06:04
  Speaker 1: a propulsion system that seems as strange to us as
• 1:06:08
  Speaker 1: a modern spacecraft might have seemed to someone living centuries ago.
• 1:06:12
  Speaker 1: Perhaps new materials will make spacecraft dramatically lighter and stronger.
• 1:06:18
  Speaker 1: Perhaps new forms of energy will become practical. Perhaps machines
• 1:06:22
  Speaker 1: will learn to operate independently for centuries. Perhaps humans will
• 1:06:27
  Speaker 1: change biologically. Perhaps we will find ways to protect living
• 1:06:31
  Speaker 1: organisms during extremely long journeys. Perhaps we will discover something
• 1:06:36
  Speaker 1: about space itself that we do not yet understand. Or
• 1:06:40
  Speaker 1: perhaps none of these things will happen. Perhaps humanity will
• 1:06:44
  Speaker 1: remain near the sun. Perhaps we will build enormous habitats
• 1:06:48
  Speaker 1: throughout the solar system. Perhaps the planets, moons, asteroids and
• 1:06:53
  Speaker 1: distant regions around our star will provide enough room for
• 1:06:57
  Speaker 1: civilization for an unimaginably long time. That possibility is not failure.
• 1:07:03
  Speaker 1: The solar system itself is vast. There are many worlds here.
• 1:07:08
  Speaker 1: Many moons. many reservoirs of water and ice, many places
• 1:07:13
  Speaker 1: that humanity has barely begun to explore. Perhaps our future
• 1:07:17
  Speaker 1: civilisation will spread outward without ever needing to cross the
• 1:07:21
  Speaker 1: darkness between stars, and perhaps that is enough. You can
• 1:07:25
  Speaker 1: imagine humanity slowly expanding through its own stellar neighbourhood, quiet
• 1:07:31
  Speaker 1: settlements near distant moons, research stations among the asteroids, habitats
• 1:07:37
  Speaker 1: travelling around the sun. machines exploring the outer planets, small
• 1:07:42
  Speaker 1: communities living beneath protective structures surrounded by darkness and sunlight.
• 1:07:48
  Speaker 1: The solar system could become a very large home, and
• 1:07:51
  Speaker 1: beyond it the stars would remain, not as failures, not
• 1:07:55
  Speaker 1: as forbidden places, simply as distant possibilities. You might still
• 1:08:00
  Speaker 1: look toward them, you might still wonder what worlds are there,
• 1:08:04
  Speaker 1: you might still wonder whether another civilisation has looked toward
• 1:08:07
  Speaker 1: our own sun and asked the same questions. The universe
• 1:08:11
  Speaker 1: does not hurry. Stars form slowly. Planets change slowly. Galaxies
• 1:08:17
  Speaker 1: move slowly. Light itself takes years to cross the distances
• 1:08:22
  Speaker 1: between neighbouring stars. And perhaps humanity too will eventually have
• 1:08:27
  Speaker 1: to learn how to think on those timescales. Not in years,
• 1:08:31
  Speaker 1: not in decades, but in centuries. thousands of years, perhaps
• 1:08:37
  Speaker 1: even longer, so you can let the question rest now.
• 1:08:40
  Speaker 1: Will humanity ever leave the solar system? Maybe, maybe not.
• 1:08:45
  Speaker 1: The honest answer is that you do not know, and
• 1:08:48
  Speaker 1: perhaps no one alive today can know. What you do
• 1:08:52
  Speaker 1: know is that the journey would demand something extraordinary. Not
• 1:08:56
  Speaker 1: simply a better rocket, not simply a larger entity, engine,
• 1:09:00
  Speaker 1: but perhaps an entirely different relationship with distance, energy, time,
• 1:09:06
  Speaker 1: biology and civilisation itself. You can let that thought become quiet.
• 1:09:12
  Speaker 1: The stars remain where they are. The sun continues to shine.
• 1:09:17
  Speaker 1: Earth continues to turn. and somewhere far beyond the edge
• 1:09:21
  Speaker 1: of your imagination, another planet may be circling another star,
• 1:09:25
  Speaker 1: completely unaware that you are thinking about it tonight. Perhaps
• 1:09:29
  Speaker 1: one day you will reach it. Perhaps your descendants will.
• 1:09:33
  Speaker 1: Perhaps only a machine will arrive. Or perhaps humanity will
• 1:09:37
  Speaker 1: remain here, beneath this familiar sky, finding everything it needs
• 1:09:41
  Speaker 1: among the worlds that already surround the sun. There is
• 1:09:45
  Speaker 1: no need to decide. There is no need to predict
• 1:09:48
  Speaker 1: the ending. For now, you can simply rest. You are safe.
• 1:09:53
  Speaker 1: There is nothing to do. The universe can remain enormous.
• 1:09:58
  Speaker 1: The distances can remain difficult to imagine. The stars can
• 1:10:01
  Speaker 1: remain far away. And you can simply breathe, slowly, gently,
• 1:10:07
  Speaker 1: while the darkness continues around you. Because perhaps the deepest
• 1:10:11
  Speaker 1: mystery is not whether humanity will ever escape the solar system.
• 1:10:15
  Speaker 1: Perhaps the deeper mystery is what humanity will become while
• 1:10:19
  Speaker 1: it is still here, and somewhere beneath your feet, beneath
• 1:10:23
  Speaker 1: the oceans and mountains, beneath the familiar surface of earth,
• 1:10:28
  Speaker 1: another quiet story may already be waiting, a story about
• 1:10:32
  Speaker 1: the future, a story about the worlds we build before
• 1:10:35
  Speaker 1: we ever leave this one, and perhaps, very softly, that
• 1:10:40
  Speaker 1: is where you can let your thoughts drift next. And
• 1:10:45
  Speaker 1: so our journey drifts quietly to its end, You can
• 1:10:49
  Speaker 1: let the spacecraft become still now, even though it is
• 1:10:52
  Speaker 1: still moving through the darkness, even though the stars continue
• 1:10:56
  Speaker 1: to shine beyond the glass, even though the great distances
• 1:11:00
  Speaker 1: of the universe remain exactly where they were. You have
• 1:11:04
  Speaker 1: travelled from the familiar surface of Earth, beyond the Moon,
• 1:11:08
  Speaker 1: beyond the planets, toward the distant edges of the solar system,
• 1:11:12
  Speaker 1: and then farther still, into the quiet spaces between stars.
• 1:11:17
  Speaker 1: You have felt how enormous distance can become. You have
• 1:11:21
  Speaker 1: imagined extraordinary speed. You have passed through the nearly empty
• 1:11:26
  Speaker 1: space between the stars, where even tiny particles can matter
• 1:11:30
  Speaker 1: when you are moving fast enough. You have looked toward
• 1:11:34
  Speaker 1: other worlds and discovered that a planet can be beautiful
• 1:11:37
  Speaker 1: without being a home. You have watched the nearby stars
• 1:11:41
  Speaker 1: become a small neighbourhood inside the enormous Milky Way. And
• 1:11:46
  Speaker 1: you have imagined journeys so long that one human lifetime
• 1:11:50
  Speaker 1: would no longer be enough. Perhaps humanity will one day
• 1:11:54
  Speaker 1: cross those distances. Perhaps a future spacecraft will travel between
• 1:11:58
  Speaker 1: the stars. Perhaps machines will go first, quietly carrying knowledge
• 1:12:04
  Speaker 1: into places no human has ever seen. Perhaps generations of
• 1:12:08
  Speaker 1: people will live beneath unfamiliar skies. Or perhaps humanity will
• 1:12:12
  Speaker 1: remain within the solar system for a very, very long time,
• 1:12:16
  Speaker 1: building quiet homes among the worlds that already surround the sun.
• 1:12:21
  Speaker 1: There is no need to know tonight. There is nothing
• 1:12:24
  Speaker 1: to decide. You are safe. There is nothing to do.
• 1:12:28
  Speaker 1: The stars do not need an answer from you. They
• 1:12:30
  Speaker 1: will continue shining whether humanity reaches them or not. The
• 1:12:35
  Speaker 1: sun will continue its slow journey through the galaxy. The
• 1:12:38
  Speaker 1: planets will continue moving through their ancient paths. The distant
• 1:12:43
  Speaker 1: worlds will continue turning beneath skies, that no human has
• 1:12:47
  Speaker 1: ever touched, and Earth will continue carrying you quietly through space.
• 1:12:52
  Speaker 1: You can feel the weight of the bed beneath you now.
• 1:12:55
  Speaker 1: You can notice the slow rhythm of your breathing, in
• 1:12:59
  Speaker 1: and out, slowly, gently. There is no need to follow
• 1:13:03
  Speaker 1: every thought. If your mind wanders, let it wander. If
• 1:13:07
  Speaker 1: the story fades, let it fade. If you are already
• 1:13:11
  Speaker 1: drifting towards sleep, you can simply let yourself go, The
• 1:13:16
  Speaker 1: universe is large enough to hold every unanswered question. It
• 1:13:20
  Speaker 1: is large enough for possibilities we cannot yet imagine, and
• 1:13:24
  Speaker 1: perhaps that is comforting. You do not need to understand
• 1:13:27
  Speaker 1: the whole universe. You do not need to reach the
• 1:13:31
  Speaker 1: edge of it. You only need to rest here, beneath
• 1:13:34
  Speaker 1: this small patch of sky, while everything beyond you continues
• 1:13:38
  Speaker 1: its slow and silent movement. So let the stars become
• 1:13:42
  Speaker 1: softer now. Let the distant light become quieter. let the
• 1:13:46
  Speaker 1: enormous distances disappear from your thoughts. For tonight, you are
• 1:13:51
  Speaker 1: not travelling anywhere. You are simply here, breathing, resting, drifting,
• 1:13:57
  Speaker 1: and somewhere far beyond your room, the Milky Way continues
• 1:14:01
  Speaker 1: turning through the darkness, carrying stars and planets and clouds
• 1:14:05
  Speaker 1: of ancient dust with it. Somewhere among those stars, there
• 1:14:09
  Speaker 1: may be worlds no telescope has yet revealed. Somewhere, There
• 1:14:14
  Speaker 1: may be oceans we have never seen. Somewhere, perhaps, there
• 1:14:18
  Speaker 1: may be another quiet sky waiting for a future traveller.
• 1:14:22
  Speaker 1: But that future can wait. The stars can wait. The
• 1:14:26
  Speaker 1: universe can wait. For now, you can sleep. And so,
• 1:14:30
  Speaker 1: our journey drifts quietly to its end. Whether you are
• 1:14:34
  Speaker 1: still listening beneath the gentle glow of your screen, or
• 1:14:37
  Speaker 1: already floating somewhere between dreams and distant stars, thank you
• 1:14:42
  Speaker 1: for travelling here tonight. through silent distances, ancient light, distant worlds,
• 1:14:49
  Speaker 1: and the quiet questions surrounding humanity's place among the stars.
• 1:14:53
  Speaker 1: If this wandering brought you a little calm, you're welcome
• 1:14:57
  Speaker 1: to subscribe or share it with someone who could use
• 1:15:00
  Speaker 1: a gentler night beneath the cosmos. For now, rest well.
• 1:15:05
  Speaker 1: The stars will keep burning. The planets will keep turning.
• 1:15:09
  Speaker 1: The sun will keep shining. and the universe will carry
• 1:15:12
  Speaker 1: on softly around you while you sleep.