Latest / Boring Science / Voyager Reached the Edge of the Solar System... Then Found Something Strange

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Voyager Reached the Edge of the Solar System... Then Found Something Strange · Boring Science

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  Speaker 1: Hello, and welcome to Boring Science to Sleep, a quiet
• 0:04
  Speaker 1: place where science becomes slow, soft, and easy to drift through. Tonight,
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  Speaker 1: you're going to gently explore the shocking discoveries made by
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  Speaker 1: Voyager at the edge of the solar system. Not to
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  Speaker 1: learn everything, and not to remember every detail, but simply
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  Speaker 1: to notice the journey slowly, calmly, one distant world at
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  Speaker 1: a time. You'll travel with two small spacecraft that left
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  Speaker 1: Earth in 1977, passed the giant planets, crossed an invisible
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  Speaker 1: boundary around the Sun, and eventually began sending back whispers
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  Speaker 1: from the space between the stars. But 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,
• 0:52
  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
• 0:58
  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, maybe let a fan
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  Speaker 1: hum softly in the background, and allow your body to
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  Speaker 1: become a little heavier, while your thoughts become a little lighter.
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  Speaker 1: There is nothing to do. You are safe. You can
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  Speaker 1: simply listen and drift. And very slowly... We can begin
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  Speaker 1: by returning to a small blue world, far behind us now,
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  Speaker 1: where the whole story began. Imagine yourself floating quietly above Earth,
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  Speaker 1: with no need to move, no need to reach anywhere,
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  Speaker 1: simply watching the planet turn beneath you. The oceans are
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  Speaker 1: blue and soft beneath the sunlight. Clouds move slowly across
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  Speaker 1: the surface. Somewhere below, people are sleeping, waking, walking through streets,
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  Speaker 1: looking out of windows. listening to rain, making plans for
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  Speaker 1: ordinary days. And from this distance, all of those lives
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  Speaker 1: are gathered together on one small world. This is the
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  Speaker 1: world Voyager was leaving. In the 1970s, scientists were given
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  Speaker 1: a remarkable opportunity, a kind of celestial arrangement that would
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  Speaker 1: not return for many generations. The outer planets were positioned
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  Speaker 1: in a way that allowed a spacecraft to travel from
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  Speaker 1: one giant world to another, using each planet's gravity to
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  Speaker 1: help shape its path. You can think of gravity here
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  Speaker 1: as a very gentle hand. Voyager would approach a planet,
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  Speaker 1: pass around it along a carefully chosen path and allow
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  Speaker 1: the planet's enormous gravity to change the spacecraft's motion. The
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  Speaker 1: spacecraft would not need to carry enough fuel to simply
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  Speaker 1: push itself all the way outward. Instead, it could borrow
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  Speaker 1: a little of the planet's movement, changing its speed and
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  Speaker 1: direction as it passed. This is called a gravity assist.
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  Speaker 1: But you do not need to hold on to the name.
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  Speaker 1: You can simply imagine a tiny traveller moving through darkness,
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  Speaker 1: meeting one enormous planet after another, and allowing each planet
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  Speaker 1: to quietly guide it onward. The opportunity was unusual because Jupiter, Saturn,
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  Speaker 1: Uranus and Neptune were arranged in a particularly useful pattern.
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  Speaker 1: It was as though several distant stepping stones had appeared
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  Speaker 1: across the outer solar system at just the right time,
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  Speaker 1: and NASA decided to take the opportunity. Voyager 2 left
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  Speaker 1: Earth first, on August 20th, 1977. Voyager 1 followed on
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  Speaker 1: September 5th. They were not enormous spacecraft. They were small machines,
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  Speaker 1: carrying cameras, scientific instruments, radios, computers … and a few
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  Speaker 1: carefully protected systems that would need to survive, not for years,
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  Speaker 1: but for something much longer. At the beginning, nobody could
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  Speaker 1: know just how long that would become. Their original journey
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  Speaker 1: was centred on Jupiter and Saturn. Four years was the
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  Speaker 1: basic shape of the mission. Four years. That sounds like
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  Speaker 1: a long time when you are standing on Earth. But
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  Speaker 1: compared with the age of the planets, it is barely
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  Speaker 1: a breath. And Voyager was about to leave that breath behind.
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  Speaker 1: Only about 13 days after launch, one of the spacecraft
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  Speaker 1: looked backward. Earth and the moon appeared together in the darkness,
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  Speaker 1: separated from the spacecraft by millions of miles. It was
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  Speaker 1: an early glimpse of something that would become one of
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  Speaker 1: the deepest themes of the entire journey. Distance changes the
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  Speaker 1: way you see home. From the ground, Earth feels enormous.
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  Speaker 1: You can walk across it for an entire lifetime and
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  Speaker 1: still see only a tiny part of it, But Voyager
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  Speaker 1: was already far enough away for Earth to begin looking small.
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  Speaker 1: The planet was still blue. The moon was still beside it.
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  Speaker 1: The sunlight was still falling across both worlds. Nothing about
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  Speaker 1: Earth itself had changed. Only the distance had changed. And
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  Speaker 1: that distance quietly transformed everything. Behind Voyager, the familiar world
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  Speaker 1: became smaller. Ahead, the darkness became wider. And somewhere far
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  Speaker 1: in front of the spacecraft was Jupiter. You can imagine
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  Speaker 1: approaching it slowly. At first, Jupiter would simply be another
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  Speaker 1: point of light, then a brighter point, then a distant sphere,
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  Speaker 1: and eventually, a gigantic world filling more and more of
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  Speaker 1: the spacecraft's view. Jupiter was so large that its gravity
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  Speaker 1: could become part of Voyager's journey. The spacecraft would pass
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  Speaker 1: through the planet's enormous gravitational environment, and that encounter would
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  Speaker 1: help send it onward. But gravity was not the only
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  Speaker 1: thing waiting there. Jupiter itself was waiting. And Jupiter was
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  Speaker 1: not the quiet, simple world that people had once imagined.
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  Speaker 1: It had moving clouds, enormous storms, moons hidden in the darkness,
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  Speaker 1: and a ring system that had not yet been seen.
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  Speaker 1: There were worlds there that had never been photographed closely.
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  Speaker 1: There were surfaces that that would reveal patterns nobody had expected,
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  Speaker 1: and there was one small moon whose surface would appear
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  Speaker 1: to be alive with volcanic activity. But for now, all
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  Speaker 1: of that was still ahead. You are still floating beside Voyager,
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  Speaker 1: somewhere between Earth and Jupiter, with the planet behind you
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  Speaker 1: becoming smaller and the giant world ahead becoming brighter. The
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  Speaker 1: spacecraft continues without hurry. There is no road beneath it.
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  Speaker 1: There is no wind. There is almost nothing around it,
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  Speaker 1: only darkness, sunlight, gravity, and the slow movement of a
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  Speaker 1: little machine, carrying a small piece of earth, farther than
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  Speaker 1: anything like it had gone before. The first great world
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  Speaker 1: is waiting, and as you drift quietly toward it, you
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  Speaker 1: can almost imagine earth behind you as a tiny blue light,
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  Speaker 1: still turning peacefully, while Jupiter grows slowly larger in the distance.
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  Speaker 1: There is nothing to chase. nothing to fear. The journey
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  Speaker 1: is simply continuing, one quiet gravitational step at a time.
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  Speaker 1: After leaving Earth behind, you continue outward through the darkness,
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  Speaker 1: with Jupiter slowly growing ahead of you. At first, it
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  Speaker 1: is only a point of light. Then, little by little,
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  Speaker 1: it becomes a small disk, and then a world, a
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  Speaker 1: very large world. Jupiter is so enormous that that the
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  Speaker 1: little spacecraft approaching it seems almost impossibly small, like a
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  Speaker 1: single grain of dust drifting toward a vast, slowly turning cloud.
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  Speaker 1: From far away, Jupiter looks calm. Soft bands of colour
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  Speaker 1: circle the planet, pale and dark layers moving around one another,
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  Speaker 1: while the great sphere turns quietly beneath the sunlight. But
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  Speaker 1: as Voyager came closer, that calm appearance began to change.
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  Speaker 1: The clouds were moving, the atmosphere was folding over itself.
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  Speaker 1: Storms were turning slowly, some of them lasting for years,
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  Speaker 1: perhaps much longer. And among all those clouds was one
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  Speaker 1: feature that had already been seen from Earth, but never
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  Speaker 1: with the closeness that Voyager could provide, the Great Red Spot.
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  Speaker 1: You can imagine looking down into it, slowly, without hurry.
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  Speaker 1: It is not a solid mark painted onto the planet.
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  Speaker 1: It is a vast storm, a huge rotating disturbance in
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  Speaker 1: Jupiter's atmosphere, larger than Earth. From your quiet position beside Voyager,
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  Speaker 1: the storm would seem less like something violent and more
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  Speaker 1: like a slowly turning whirlpool in an ocean without a surface.
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  Speaker 1: There is no shoreline, no ground beneath it, only layers
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  Speaker 1: of gas moving around one another, endlessly carried by the
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  Speaker 1: atmosphere of this enormous planet. And then, As Voyager looked
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  Speaker 1: toward the moons, the journey became even stranger. One of
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  Speaker 1: those moons was Io. At first, Io might have seemed
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  Speaker 1: like just another small world circling Jupiter, but then Voyager
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  Speaker 1: saw something that had never been seen before on another world. Volcanoes.
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  Speaker 1: Actual volcanic eruptions rising from the surface of a moon.
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  Speaker 1: The discovery changed the way scientists thought about small worlds.
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  Speaker 1: A moon did not have to be cold and inactive.
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  Speaker 1: It could still be moving inside. It could still be
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  Speaker 1: releasing heat. It could still be changing. Io is constantly
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  Speaker 1: tugged by Jupiter's enormous gravity, while the other nearby moons
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  Speaker 1: also influence its motion. Those repeated gravitational pulls gently stretch
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  Speaker 1: and squeeze the moon. producing heat deep inside it. You
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  Speaker 1: do not need to picture this as a complicated calculation.
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  Speaker 1: Just imagine a world being very slowly kneaded by gravity,
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  Speaker 1: again and again, for an almost unimaginable length of time.
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  Speaker 1: Deep inside Io, that motion becomes heat. and at the surface,
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  Speaker 1: the heat can find its way outward through volcanoes. So
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  Speaker 1: while Jupiter seemed to be a distant ball of clouds,
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  Speaker 1: one of the small worlds around it was quietly alive
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  Speaker 1: with fire. Then Voyager turned toward Europa. Europa looked very different.
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  Speaker 1: Its surface appeared smooth and pale, covered in ice. But
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  Speaker 1: the ice was not perfectly still. Long lines and cracks
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  Speaker 1: crossed the surface. forming delicate patterns that stretched across the moon.
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  Speaker 1: To you, looking at Europa from a great distance, it
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  Speaker 1: might have looked almost like a frozen lake viewed from above,
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  Speaker 1: except this lake was a world, floating in the darkness
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  Speaker 1: around another planet. And beneath that frozen surface, something even
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  Speaker 1: more interesting might be hiding. The patterns on Europa helped
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  Speaker 1: give scientists reason to consider that a large ocean of
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  Speaker 1: liquid water could exist beneath the ice. It was not
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  Speaker 1: something Voyager could simply see directly. It was an idea
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  Speaker 1: suggested by the shape and behaviour of the surface. And
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  Speaker 1: that is part of what made the discovery so beautiful. Sometimes,
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  Speaker 1: you do not see the thing itself. You see its
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  Speaker 1: quiet fingerprints, a crack in the ice, a slight movement,
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  Speaker 1: a pattern left behind. And from those small clues, you
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  Speaker 1: begin to imagine what might be resting underneath. Then there
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  Speaker 1: was Ganymede. Ganymede was not simply another moon. It was
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  Speaker 1: the largest moon in the solar system. Before these Voyager observations,
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  Speaker 1: Titan had often been regarded as the largest moon. But
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  Speaker 1: Ganymede revealed itself to be larger, changing the picture once again.
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  Speaker 1: Voyager was beginning to show that the solar system was
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  Speaker 1: not arranged as neatly as it might have seemed from Earth.
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  Speaker 1: Even the moons had their own personalities. One was volcanic,
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  Speaker 1: one appeared frozen but possibly hid an ocean. One was
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  Speaker 1: larger than any other moon, and there were still more
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  Speaker 1: surprises waiting. Jupiter itself had rings. They were much fainter
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  Speaker 1: than the magnificent rings of Saturn, so they had remained
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  Speaker 1: hidden from ordinary views. Voyager's instruments helped reveal them, along
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  Speaker 1: with additional small moons that had not been known before.
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  Speaker 1: It was as if the great planet had been quietly
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  Speaker 1: carrying a collection of small companions in the darkness, waiting
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  Speaker 1: for a spacecraft to come close enough to notice them.
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  Speaker 1: And now you can begin to see why Jupiter was
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  Speaker 1: more than simply the first stop. It was a change
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  Speaker 1: in perspective. Before Voyager, you could imagine planets as large,
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  Speaker 1: distant objects, beautiful but perhaps simple. After Voyager, that picture
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  Speaker 1: became harder to hold. Jupiter was a system, Its atmosphere moved.
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  Speaker 1: Its storms turned. Its moons changed. Its gravity reached outward.
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  Speaker 1: Its rings were waiting in the dark. And every discovery
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  Speaker 1: seemed to whisper the same idea in a slightly different way.
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  Speaker 1: There is more happening here than you can see from
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  Speaker 1: far away. Eventually, Voyager began preparing to leave. Jupiter's enormous
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  Speaker 1: gravity would help guide the spacecraft onward, changing its path
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  Speaker 1: and giving it a gentle boost as it passed through
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  Speaker 1: the planet's gravitational environment. You might imagine yourself drifting beside
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  Speaker 1: the spacecraft as Jupiter slowly falls behind. The great red
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  Speaker 1: spot becomes smaller. Io becomes a tiny point again. Europa's
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  Speaker 1: frozen surface disappears into distance. Ganymede fades into the darkness.
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  Speaker 1: And Jupiter, once so enormous before you, gradually becomes another
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  Speaker 1: bright world behind you. but the journey is not becoming
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  Speaker 1: quieter because there is nothing left to discover. It is
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  Speaker 1: becoming quieter because another giant planet is waiting farther away.
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  Speaker 1: Saturn is ahead. And around Saturn, there are rings, moons,
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  Speaker 1: and one particular world wrapped in a thick atmosphere, a
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  Speaker 1: world that will quietly change the paths of the two
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  Speaker 1: voyagers forever. Far behind you, Jupiter is slowly becoming smaller,
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  Speaker 1: Its enormous clouds are fading into the darkness, its moons
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  Speaker 1: are becoming tiny points of light, and the great storm
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  Speaker 1: that once filled your view is gradually disappearing. There is
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  Speaker 1: no sudden change. The spacecraft simply continues onward, carried through
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  Speaker 1: the darkness along a path shaped by gravity. And then,
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  Speaker 1: very slowly, another world begins to appear. Saturn. At first
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  Speaker 1: Saturn is only a distant point. then a pale sphere,
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  Speaker 1: and around it, almost as if floating in a delicate
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  Speaker 1: band of light, something begins to emerge. The rings. From Earth,
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  Speaker 1: Saturn's rings had already been one of the most beautiful
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  Speaker 1: sights in the night sky. But from Voyager's perspective, they
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  Speaker 1: became something much more intricate. They were not one smooth circle.
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  Speaker 1: They were made of countless narrow bands, gaps, particles, and
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  Speaker 1: delicate structures, all moving around Saturn together. You can imagine
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  Speaker 1: drifting above them, looking down through the sunlight, watching billions
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  Speaker 1: of tiny pieces of ice and rock orbit their planet.
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  Speaker 1: Some are small, some are larger. Together, they create the
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  Speaker 1: appearance of a single enormous ring. But the closer you look,
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  Speaker 1: the less simple it becomes. There are spaces between the rings.
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  Speaker 1: There are faint bands hidden beside brighter ones. there are
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  Speaker 1: tiny structures moving within the larger pattern. Saturn begins to
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  Speaker 1: feel less like a planet with a ring around it,
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  Speaker 1: and more like an entire landscape of moving material. And
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  Speaker 1: among this landscape are moons. Many moons, each one following
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  Speaker 1: its own quiet path. One of them is Mimas. From
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  Speaker 1: a distance, Mimas looks like a small, pale world. But
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  Speaker 1: across its surface is a huge crater, so large that
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  Speaker 1: it almost changes the personality of the moon itself. The
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  Speaker 1: crater is called Herschel. You do not need to remember
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  Speaker 1: the name. What matters is the image. A small moon,
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  Speaker 1: covered in ancient scars, floating beside a planet surrounded by
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  Speaker 1: enormous rings. It is another gentle reminder that the solar
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  Speaker 1: system is full of worlds that have been shaped by
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  Speaker 1: events long before you were here to see them. And
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  Speaker 1: then Voyager turned toward Titan. Titan was different, much different.
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  Speaker 1: It was large, cold, and surrounded by a thick atmosphere.
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  Speaker 1: That atmosphere became a kind of curtain. Voyager could look
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  Speaker 1: toward Titan, but it could not simply see through the
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  Speaker 1: dense layer surrounding the moon. The surface remained hidden. And sometimes,
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  Speaker 1: one of the most interesting things a spacecraft can discover
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  Speaker 1: is the limit of what it can see. You can
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  Speaker 1: imagine standing before a quiet window covered in mist. You
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  Speaker 1: know something exists beyond the glass. You may even see
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  Speaker 1: faint shapes moving behind it, but the details remain soft.
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  Speaker 1: Titan was like that. Voyager discovered that its atmosphere was
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  Speaker 1: much thicker than Earth's, and the moon became an intriguing
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  Speaker 1: place where familiar-looking cycles might occur with very different materials.
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  Speaker 1: Instead of water moving through clouds and rivers in the
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  Speaker 1: same way it does on Earth, Titan has a world
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  Speaker 1: where methane can take part in a slow cycle between
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  Speaker 1: the atmosphere and the surface. The details are complicated, but
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  Speaker 1: you can hold on to one simple image. A cold moon,
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  Speaker 1: wrapped in a thick atmosphere, with material slowly moving between
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  Speaker 1: sky and ground. A world that looks unfamiliar, yet carries
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  Speaker 1: a faint echo of something you already know. And while
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  Speaker 1: Voyager 1 was approaching Titan, something important was happening to
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  Speaker 1: the two spacecraft. They had begun their journey from the
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  Speaker 1: same Earth. They had travelled through the same broad region
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  Speaker 1: of space. They had passed Jupiter. They had both reached Saturn.
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  Speaker 1: But Saturn would be where their paths finally separated. Voyager
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  Speaker 1: 1 was directed toward Titan. Its encounter with the Moon
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  Speaker 1: would bend its trajectory. sending the spacecraft onto a path
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  Speaker 1: that would eventually carry it far above the broad plane
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  Speaker 1: in which the planets travel. That choice meant Voyager 1
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  Speaker 1: would not continue onward to Uranus and Neptune. Voyager 2 would.
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  Speaker 1: It is a quiet moment in the story, but a
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  Speaker 1: meaningful one. There was no dramatic farewell, no visible line
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  Speaker 1: between the two paths, no signal announcing that the journey
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  Speaker 1: had changed. There were simply two small spacecraft moving through
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  Speaker 1: an enormous solar system, each following a slightly different curve
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  Speaker 1: through space, one turning toward Titan, the other continuing outward.
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  Speaker 1: You can imagine watching them from very far away, two
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  Speaker 1: tiny lights. For a little while, they travel in roughly
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  Speaker 1: the same direction, then one slowly bends away. The distance
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  Speaker 1: between them grows. And eventually, they are following different roads
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  Speaker 1: through the darkness. Voyager 1 will continue toward the outer
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  Speaker 1: reaches of the Sun's influence. Voyager 2 will travel onward
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  Speaker 1: toward Uranus and Neptune. And this separation gives the two
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  Speaker 1: spacecraft something valuable. Two different perspectives, two different encounters, two
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  Speaker 1: different ways of seeing the same enormous neighbourhood around the sun.
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  Speaker 1: For Voyager 1, Titan is almost like a doorway. Beyond it,
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  Speaker 1: there will be no more close planetary encounters. The spacecraft
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  Speaker 1: will continue outward, farther and farther from the worlds that
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  Speaker 1: once filled its cameras. For Voyager 2, however, another destination remains. Uranus.
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  Speaker 1: a pale and distant planet that had never before been
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  Speaker 1: visited by a spacecraft. You are still drifting with Voyager
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  Speaker 1: 2 now, watching Saturn slowly fall behind. The rings become thinner,
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  Speaker 1: the moons become smaller, the planet itself becomes a quiet
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  Speaker 1: point of light. And somewhere ahead, in the cold distance,
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  Speaker 1: Uranus is waiting. It will look unfamiliar. It will be
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  Speaker 1: colder and stranger than the worlds Voyager has already seen.
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  Speaker 1: and when the spacecraft finally arrives there, it will once
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  Speaker 1: again discover that the outer solar system is not a
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  Speaker 1: collection of simple, silent planets. It is a place full
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  Speaker 1: of subtle motion, hidden structures, distant moons, and quiet surprises.
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  Speaker 1: So you can simply rest here for a moment, between worlds,
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  Speaker 1: Saturn behind you, Uranus ahead, and two little machines continuing
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  Speaker 1: along two different paths. each carrying a small piece of
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  Speaker 1: earth deeper into the darkness. Saturn is slowly disappearing behind you.
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  Speaker 1: The rings, once so wide and bright, have become thinner
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  Speaker 1: in the distance, until they are almost impossible to separate
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  Speaker 1: from the darkness around them. You continue outward. There is
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  Speaker 1: no road beneath you, no wind against the spacecraft, no
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  Speaker 1: sound passing through the empty space. only movement, a quiet
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  Speaker 1: movement through a place so large that even millions of
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  Speaker 1: miles can begin to feel like a small distance. And
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  Speaker 1: somewhere ahead, another pale world is waiting, Uranus. For most
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  Speaker 1: of human history, Uranus had been nothing more than a
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  Speaker 1: distant point of light. It was known as a planet, certainly,
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  Speaker 1: but only from far away. No spacecraft had ever travelled
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  Speaker 1: close enough to see its atmosphere, its moons, or its
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  Speaker 1: rings in detail. Voyager 2 would change that. As the
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  Speaker 1: spacecraft approached, Uranus slowly grew larger. But it did not
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  Speaker 1: look like Jupiter. It did not look like Saturn. There
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  Speaker 1: were no enormous colourful storms covering its visible face. No
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  Speaker 1: brilliant rings dominating the scene. Instead, Uranus appeared quiet, pale,
• 23:02
  Speaker 1: almost delicate. Its atmosphere had a soft blue-green colour, created
• 23:07
  Speaker 1: by the way gases high above the planet interact with sunlight.
• 23:11
  Speaker 1: And beneath that gentle appearance was a world of immense size,
• 23:16
  Speaker 1: composed largely of materials that behave very differently from the
• 23:19
  Speaker 1: familiar rocks and gases of Earth. Today, Uranus is often
• 23:24
  Speaker 1: grouped with Neptune as an ice giant. The name sounds dramatic,
• 23:28
  Speaker 1: but the idea is simple. These are enormous planets in
• 23:32
  Speaker 1: the cold outer solar system, rich in substances that, deep
• 23:37
  Speaker 1: inside them, exist under pressures and temperatures very different from
• 23:43
  Speaker 1: anything you experience on Earth. You do not need to
• 23:46
  Speaker 1: picture the details. You can simply imagine a giant cold world,
• 23:51
  Speaker 1: wrapped in a deep atmosphere, moving silently through the outer darkness.
• 23:57
  Speaker 1: Uranus also has rings. They are much darker and less
• 24:00
  Speaker 1: obvious than Saturn's magnificent rings. You might almost miss them
• 24:05
  Speaker 1: if you were looking casually, but Voyager revealed them as
• 24:08
  Speaker 1: real structures, narrow bands of material circling the planet, thin
• 24:13
  Speaker 1: rings around a pale world, and then there were the moons,
• 24:17
  Speaker 1: small worlds moving quietly around Uranus, each one carrying a
• 24:22
  Speaker 1: surface shaped by a very long history. One of the
• 24:25
  Speaker 1: most memorable was Miranda. It looked unusual, almost as though
• 24:30
  Speaker 1: different pieces of a landscape had been placed together. Cliffs, ridges,
• 24:35
  Speaker 1: bright and dark regions, strange patterns. From far away, Miranda
• 24:40
  Speaker 1: was only another small moon. But the closer Voyager looked,
• 24:44
  Speaker 1: the more complicated the little world became. It was another
• 24:48
  Speaker 1: reminder that even the smallest destinations can hold enormous stories.
• 24:54
  Speaker 1: You continue watching as Uranus passes behind you. The encounter
• 24:58
  Speaker 1: itself is brief, compared with the age of the planet.
• 25:02
  Speaker 1: A spacecraft arrives. A spacecraft observes. A spacecraft leaves. And
• 25:08
  Speaker 1: the planet continues turning in the darkness, almost completely unaware
• 25:12
  Speaker 1: that something from a distant blue world has passed nearby.
• 25:16
  Speaker 1: There is something peaceful about that. The universe does not
• 25:20
  Speaker 1: stop for the spacecraft. It simply continues. And Voyager 2
• 25:25
  Speaker 1: continues with it, farther outward, farther into the cold, until
• 25:30
  Speaker 1: another world begins to appear. Neptune. This time the difference
• 25:35
  Speaker 1: is striking. Neptune appears deep blue, with a restless atmosphere
• 25:40
  Speaker 1: moving across its enormous globe. Voyager 2 is about to
• 25:45
  Speaker 1: provide humanity with its first close view of this distant planet.
• 25:50
  Speaker 1: And once again, the solar system refuses to be simple.
• 25:54
  Speaker 1: Neptune has enormous weather systems. Dark regions move through its atmosphere.
• 26:00
  Speaker 1: Bright clouds drift above them. Winds race through the upper
• 26:03
  Speaker 1: layers of the planet, much faster than the gentle winds
• 26:07
  Speaker 1: you know on Earth. But from Voyager's distant viewpoint, all
• 26:11
  Speaker 1: of this still becomes a quiet picture. A blue sphere.
• 26:15
  Speaker 1: A few pale clouds. A dark region moving slowly across
• 26:20
  Speaker 1: the visible face. You can imagine looking at it without
• 26:24
  Speaker 1: needing to understand every motion. Just watching. Just noticing. And
• 26:29
  Speaker 1: then Voyager sees Triton. Triton is Neptune's largest moon. It
• 26:35
  Speaker 1: is extremely cold, its surface covered with nitrogen ice and
• 26:39
  Speaker 1: other frozen materials. But despite the cold, Triton is not
• 26:43
  Speaker 1: completely still. Voyager observed evidence of active processes on its surface,
• 26:49
  Speaker 1: including dark plumes rising upward. It was an unexpected kind
• 26:53
  Speaker 1: of activity for such a distant and frozen world. You
• 26:57
  Speaker 1: might imagine a quiet winter landscape where … Beneath the stillness,
• 27:02
  Speaker 1: something is gently moving, not warm in the way Earth
• 27:05
  Speaker 1: is warm, not alive in the familiar sense, but active, changing, continuing.
• 27:12
  Speaker 1: And Triton carried another fascinating clue. Its orbit around Neptune
• 27:17
  Speaker 1: moves in the opposite direction from the direction in which
• 27:21
  Speaker 1: Neptune rotates. That unusual path suggests that Triton may not
• 27:26
  Speaker 1: have formed alongside Neptune in the same way its planet did. Instead,
• 27:31
  Speaker 1: it may have been captured by Neptune long ago, a
• 27:34
  Speaker 1: small world that travelled through the darkness until, somehow, it
• 27:39
  Speaker 1: became part of another planetary system. You can let that
• 27:42
  Speaker 1: idea drift for a moment. A moon that may have
• 27:46
  Speaker 1: once belonged somewhere else. A world wandering through ancient space,
• 27:51
  Speaker 1: eventually becoming a companion to Neptune. And then Voyager 2
• 27:55
  Speaker 1: begins to move away. Neptune becomes smaller. Triton fades. The
• 28:01
  Speaker 1: atmosphere becomes a blue point. The point becomes a tiny light.
• 28:06
  Speaker 1: And slowly, the great planetary journey is coming to a close.
• 28:10
  Speaker 1: Jupiter has passed. Saturn has passed. Uranus has passed. Neptune
• 28:16
  Speaker 1: has passed. Voyager 2 has crossed the outer planetary realm
• 28:21
  Speaker 1: that no human spacecraft had previously explored in this way.
• 28:25
  Speaker 1: The rare alignment of planets that made the journey possible
• 28:29
  Speaker 1: is now far behind. What began in the late 1970s
• 28:34
  Speaker 1: as a carefully planned journey between worlds has become something
• 28:38
  Speaker 1: much quieter. There are no more giant planets waiting close ahead.
• 28:43
  Speaker 1: There are no more great rings to photograph. No more
• 28:47
  Speaker 1: enormous atmospheres filling the cameras. The spacecraft is leaving the
• 28:51
  Speaker 1: familiar planetary neighbourhood behind. And yet, the journey is not finished.
• 28:57
  Speaker 1: because beyond Neptune there is still something enormous. Not another planet,
• 29:03
  Speaker 1: not another moon, something much harder to see. The invisible
• 29:07
  Speaker 1: influence of the sun, a vast region of thin particles
• 29:12
  Speaker 1: and magnetic influence extending outward into darkness. Voyager 2 is
• 29:17
  Speaker 1: moving toward its distant boundary, and Voyager 1, following another
• 29:22
  Speaker 1: path after its encounter with Titan, is doing the same.
• 29:26
  Speaker 1: The planets are behind them now, The next discoveries will
• 29:29
  Speaker 1: not come from looking at worlds. They will come from
• 29:32
  Speaker 1: looking at almost nothing. From noticing tiny changes in an
• 29:36
  Speaker 1: almost empty space. From watching invisible particles slowly down, turn, scatter,
• 29:43
  Speaker 1: and move. And somewhere far beyond the blue light of Neptune,
• 29:47
  Speaker 1: that almost invisible boundary is waiting. Not like a wall,
• 29:51
  Speaker 1: not like a door, more like a place where one
• 29:54
  Speaker 1: kind of space gradually becomes another. You can simply rest
• 29:58
  Speaker 1: with that thought. The planets are fading behind you. The
• 30:02
  Speaker 1: darkness ahead is becoming larger. And in that darkness, Voyager
• 30:07
  Speaker 1: is approaching something that cannot be photographed in the ordinary way.
• 30:11
  Speaker 1: Something you can only discover by listening to the faint
• 30:14
  Speaker 1: traces carried back across the enormous distance. Something quiet. Something
• 30:19
  Speaker 1: almost invisible. And when you are ready, you can simply
• 30:23
  Speaker 1: keep drifting with it. Neptune is becoming smaller now. The
• 30:30
  Speaker 1: blue world that once filled part of Voyager 2's view
• 30:33
  Speaker 1: is slowly retreating into the darkness, becoming a distant point,
• 30:38
  Speaker 1: and then something even smaller, until eventually there is almost
• 30:41
  Speaker 1: nothing left to see. The great planetary journey is behind you. Jupiter. Saturn. Uranus. Neptune.
• 30:51
  Speaker 1: Four enormous worlds, each different, each carrying its own quiet
• 30:55
  Speaker 1: atmosphere of moons, rings, storms and frozen landscapes. And now
• 31:01
  Speaker 1: there is mostly darkness ahead. But before Voyager 1 completely
• 31:05
  Speaker 1: turns away from the familiar planets, something very small appears
• 31:09
  Speaker 1: in its camera. Earth. It is the 14th day of
• 31:13
  Speaker 1: February 1990. Voyager 1 is billions of miles from home.
• 31:18
  Speaker 1: The spacecraft turns its camera back toward the inner solar system,
• 31:23
  Speaker 1: toward the place it came from, and there, suspended in
• 31:26
  Speaker 1: a vast field of darkness, is a tiny point of
• 31:30
  Speaker 1: pale blue light, the pale blue dot. You might expect
• 31:34
  Speaker 1: Earth to look large. After all, Earth is where you live.
• 31:39
  Speaker 1: It holds oceans, forests, cities, mountains, clouds, and every person
• 31:44
  Speaker 1: you have ever known. But from this distance, all of
• 31:48
  Speaker 1: that becomes almost invisible. The entire world is reduced to
• 31:52
  Speaker 1: a tiny point, a little blue presence inside an enormous darkness,
• 31:57
  Speaker 1: and then something quietly remarkable happens. Voyager's cameras are turned off.
• 32:03
  Speaker 1: There will be no more planetary portraits from this spacecraft,
• 32:07
  Speaker 1: no more close views of giant worlds, no more detailed
• 32:11
  Speaker 1: images of moons. The camera's long visual journey is finished.
• 32:15
  Speaker 1: From this moment onward, Voyager will have to discover the
• 32:19
  Speaker 1: distant solar system in another way. Not by looking. By measuring.
• 32:24
  Speaker 1: By noticing tiny changes in particles. By sensing the invisible
• 32:29
  Speaker 1: environment around it. And so you can imagine Voyager continuing outward,
• 32:34
  Speaker 1: camera silent, its small instruments still working, its faint radio
• 32:38
  Speaker 1: signal still carrying information toward Earth. The planets are behind you.
• 32:44
  Speaker 1: But the sun is not. Even at these immense distances,
• 32:47
  Speaker 1: the Sun continues to influence the space around the spacecraft.
• 32:51
  Speaker 1: You cannot see this influence directly. There is no glowing
• 32:55
  Speaker 1: shell around the solar system, no bright boundary painted across
• 32:59
  Speaker 1: the darkness. Instead, imagine an enormous, almost weightless bubble surrounding
• 33:05
  Speaker 1: the Sun and everything moving around it. This is the heliosphere.
• 33:10
  Speaker 1: You can think of it as the enormous bubble of
• 33:13
  Speaker 1: influence created by the Sun's outward flow. The sun is
• 33:17
  Speaker 1: constantly releasing a very thin stream of charged particles. This
• 33:22
  Speaker 1: stream travels outward in every direction. It is called the
• 33:25
  Speaker 1: solar wind. It is so thin that space still seems empty.
• 33:31
  Speaker 1: But over enormous distances, these tiny particles create a region
• 33:35
  Speaker 1: that belongs, in a sense, to the sun. The planets
• 33:39
  Speaker 1: live inside this enormous region. So do the spacecraft. and
• 33:44
  Speaker 1: Voyager is moving slowly toward its farthest edge. For a
• 33:48
  Speaker 1: long time, scientists had imagined that the solar wind would
• 33:52
  Speaker 1: simply become weaker and weaker as it travelled away from
• 33:56
  Speaker 1: the sun, like a breath fading into a large room, quieter, thinner,
• 34:02
  Speaker 1: eventually almost nothing. But Voyager began to show that the
• 34:06
  Speaker 1: reality was more interesting. The solar wind did not simply
• 34:10
  Speaker 1: fade away. Instead, The outward flow eventually encountered another environment,
• 34:15
  Speaker 1: a place where the material coming from the Sun met
• 34:18
  Speaker 1: the extremely thin material between the stars. The boundary between
• 34:23
  Speaker 1: these two regions is called the heliopause, but you do
• 34:26
  Speaker 1: not need to picture it as a hard wall. It
• 34:29
  Speaker 1: is better to imagine a vast, invisible meeting place. On
• 34:33
  Speaker 1: one side, the Sun's particles are flowing outward. On the
• 34:37
  Speaker 1: other side, material from interstellar space is already present. the
• 34:41
  Speaker 1: two environments meet. They interact, they push gently against one another,
• 34:47
  Speaker 1: and Voyager is approaching that quiet transition. As it travels
• 34:51
  Speaker 1: farther away, the familiar influence of the sun becomes less dominant.
• 34:56
  Speaker 1: Particles coming from the sun become fewer. Particles arriving from
• 35:00
  Speaker 1: much farther away become more noticeable. It is almost like
• 35:05
  Speaker 1: walking slowly away from the warmth of a room, and realising,
• 35:09
  Speaker 1: only after a long time, that the air around you
• 35:12
  Speaker 1: has changed. There is no door, there is no single
• 35:16
  Speaker 1: instant when one world disappears and another suddenly begins. There
• 35:21
  Speaker 1: is a gradual transition. And yet, Voyager's instruments eventually detect
• 35:26
  Speaker 1: something that makes the boundary feel surprisingly real. In 2012,
• 35:30
  Speaker 1: Voyager 1 recorded a sharp decrease in the charged particles
• 35:34
  Speaker 1: associated with the sun, while particles arriving from the wider
• 35:38
  Speaker 1: galaxy became much more prominent. the spacecraft had reached interstellar space.
• 35:44
  Speaker 1: Six years later, Voyager 2 made the same extraordinary transition.
• 35:49
  Speaker 1: But Voyager 2 had an advantage. One of its instruments
• 35:53
  Speaker 1: was still able to directly examine the thin plasma surrounding
• 35:56
  Speaker 1: the spacecraft, giving scientists a more immediate look at the
• 36:00
  Speaker 1: boundary itself. And what they found was not a simple edge.
• 36:04
  Speaker 1: It was a region, a complicated region, a place where
• 36:08
  Speaker 1: particles from the Sun were and particles from interstellar space
• 36:13
  Speaker 1: interact with one another. Voyager had not simply crossed a
• 36:17
  Speaker 1: line drawn somewhere in the darkness. It had entered a
• 36:20
  Speaker 1: new environment. And this changed the meaning of the journey.
• 36:24
  Speaker 1: The spacecraft was no longer simply travelling farther from the planets.
• 36:29
  Speaker 1: It was moving through material between the stars. Material so
• 36:33
  Speaker 1: thin that you would normally call the region empty. And yet,
• 36:37
  Speaker 1: there was something there, tiny particles. Invisible fields, subtle waves,
• 36:43
  Speaker 1: faint traces of the sun reaching outward, and the quiet
• 36:47
  Speaker 1: pressure of the space between stars pressing inward. You can
• 36:51
  Speaker 1: let that image remain soft in your mind, a bubble
• 36:55
  Speaker 1: around the sun, a distant boundary, a spacecraft approaching it
• 36:59
  Speaker 1: after decades of travel. Nothing dramatic happens when Voyager crosses.
• 37:04
  Speaker 1: There is no flash, no sound, no visible doorway. only
• 37:10
  Speaker 1: numbers changing inside instruments, particles becoming rarer or more common,
• 37:15
  Speaker 1: invisible conditions shifting slowly around a machine that has been
• 37:19
  Speaker 1: travelling since the 1970s. And perhaps that is what makes
• 37:23
  Speaker 1: it so beautiful. The edge of the sun's influence is
• 37:27
  Speaker 1: not a wall. It is a conversation, a place where
• 37:31
  Speaker 1: one environment meets another, a place where the influence of
• 37:34
  Speaker 1: a star begins to give way to the space between stars.
• 37:39
  Speaker 1: and Voyager is quietly listening. Far behind it, Earth remains
• 37:44
  Speaker 1: a tiny blue point. Far behind that, the planets continue
• 37:48
  Speaker 1: circling the sun, and ahead, beyond the invisible boundary, there
• 37:53
  Speaker 1: is a colder, thinner environment that no human being had
• 37:57
  Speaker 1: ever directly explored before. You are safe here. There is
• 38:01
  Speaker 1: nothing to do. You can simply rest and imagine Voyager
• 38:05
  Speaker 1: drifting farther into that almost empty darkness. The camera is
• 38:09
  Speaker 1: silent now, the planets are distant, but the spacecraft is
• 38:14
  Speaker 1: still sensing, still measuring, still carrying a faint message home,
• 38:20
  Speaker 1: and somewhere beyond that invisible boundary, space itself is beginning
• 38:24
  Speaker 1: to feel just a little different. For a long time
• 38:30
  Speaker 1: you might imagine the edge of the solar system as
• 38:32
  Speaker 1: something simple, a distant place where the sun's influence slowly
• 38:36
  Speaker 1: becomes weaker, quieter. thinner, until eventually there is almost nothing left,
• 38:42
  Speaker 1: a little like the last warmth of a fire disappearing
• 38:45
  Speaker 1: into the night. But Voyager found something different. The edge
• 38:50
  Speaker 1: was not simply a fading away, it was active, it
• 38:54
  Speaker 1: was changing, and in some ways it was much stranger
• 38:57
  Speaker 1: than anyone had expected. You can imagine yourself drifting beside
• 39:02
  Speaker 1: Voyager now, far beyond the planets, surrounded by darkness so
• 39:06
  Speaker 1: complete it that there is almost nothing for your eyes
• 39:10
  Speaker 1: to hold onto. And yet, the space around you is
• 39:13
  Speaker 1: not truly empty. There are tiny charged particles moving through it.
• 39:18
  Speaker 1: There are invisible magnetic fields. There are faint disturbances travelling
• 39:23
  Speaker 1: through the thin material between the stars. There is movement everywhere,
• 39:27
  Speaker 1: but almost none of it can be seen. Voyager is
• 39:30
  Speaker 1: entering a place where these invisible things begin to matter
• 39:34
  Speaker 1: more than the distant planets ever did. The enormous bubble
• 39:38
  Speaker 1: created by the sun is meeting the space between the stars.
• 39:42
  Speaker 1: And the meeting is not gentle in the simple way
• 39:45
  Speaker 1: scientists once imagined. It is more like two enormous currents
• 39:49
  Speaker 1: slowly pressing against each other. The outward flow from the
• 39:53
  Speaker 1: Sun reaches a point where it can no longer continue freely.
• 39:57
  Speaker 1: It slows, it bends, it changes direction, and around it,
• 40:02
  Speaker 1: the material between the stars pushes inward. The boundary that
• 40:06
  Speaker 1: forms between these environments is the heliopause, but even that
• 40:10
  Speaker 1: word can make the boundary sound too neat. There is
• 40:13
  Speaker 1: no hard surface floating in space. no invisible glass wall. Instead,
• 40:19
  Speaker 1: there is a broad and changing region where the conditions
• 40:22
  Speaker 1: gradually become different. Voyager 2 gave scientists an especially valuable
• 40:27
  Speaker 1: glimpse of this transition, because one of its instruments could
• 40:31
  Speaker 1: directly sense the thin, electrically active gas surrounding the spacecraft.
• 40:37
  Speaker 1: And what it found was surprising. Outside the Sun's protective bubble,
• 40:42
  Speaker 1: The plasma was denser than scientists had expected in some regions.
• 40:47
  Speaker 1: The material was still extraordinarily thin. You would still experience
• 40:51
  Speaker 1: it as almost complete emptiness. But compared with the region
• 40:55
  Speaker 1: inside the heliosphere, there was noticeably more of it. Imagine
• 41:00
  Speaker 1: an enormous room where there is almost no mist at all.
• 41:05
  Speaker 1: Then imagine moving into another room where the mist is
• 41:08
  Speaker 1: still barely visible, but just slightly thicker. To your eyes,
• 41:13
  Speaker 1: both rooms might look empty. To a sensitive instrument, they
• 41:17
  Speaker 1: would be completely different environments. That is how Voyager was
• 41:21
  Speaker 1: able to notice what human senses never could. And there
• 41:25
  Speaker 1: was another difference. The material outside was generally colder than
• 41:29
  Speaker 1: the plasma closer to the boundary. Inside, the sun's enormous bubble,
• 41:34
  Speaker 1: the particles had been strongly influenced by the solar wind. Outside,
• 41:39
  Speaker 1: the environment belonged more to the space between stars. Yet
• 41:43
  Speaker 1: the two regions were not perfectly separated. Particles could cross.
• 41:48
  Speaker 1: Particles from the sun could move outward. Particles from interstellar
• 41:53
  Speaker 1: space could move inward. They could mingle in the region
• 41:57
  Speaker 1: around the boundary, creating something like a soft layer between
• 42:01
  Speaker 1: two enormous environments. So even the edge itself was not
• 42:05
  Speaker 1: truly an edge. It was a place of exchange. A
• 42:09
  Speaker 1: place where particles wandered across an invisible border. A place
• 42:13
  Speaker 1: where the sun and the wider galaxy quietly touched. And
• 42:17
  Speaker 1: then there was the magnetic field. You cannot see a
• 42:20
  Speaker 1: magnetic field. You cannot hear one. You cannot feel it
• 42:24
  Speaker 1: passing around you in the ordinary sense. But charged particles
• 42:28
  Speaker 1: can respond to it. They can curve. They can change direction.
• 42:33
  Speaker 1: They can become guided along invisible pathways. Voyager discovered that
• 42:38
  Speaker 1: the magnetic field just beyond the heliopause behaved in ways
• 42:42
  Speaker 1: that did not fit neatly into earlier expectations. The field
• 42:46
  Speaker 1: outside was stronger than many earlier estimates had suggested, and
• 42:50
  Speaker 1: that meant the space between stars was not as passive
• 42:53
  Speaker 1: as it might have seemed. The galaxy was pressing gently
• 42:57
  Speaker 1: against the sun's enormous bubble, not with a physical hand,
• 43:01
  Speaker 1: not with a solid surface. but through particles and invisible fields,
• 43:06
  Speaker 1: through an almost weightless pressure spread across an enormous distance.
• 43:10
  Speaker 1: The effect was subtle, but Voyager could measure it, and
• 43:14
  Speaker 1: there was something else that made the boundary even more interesting.
• 43:18
  Speaker 1: The heliosphere does not appear to be perfectly still. It
• 43:22
  Speaker 1: can move. It can ripple. It can become distorted. The
• 43:26
  Speaker 1: pressure around it can change as conditions in space change.
• 43:31
  Speaker 1: You can imagine a very thin membrane floating on a
• 43:33
  Speaker 1: slow ocean. The membrane does not remain perfectly motionless. A
• 43:38
  Speaker 1: distant wave arrives. It rises slightly, then settles. Another wave
• 43:44
  Speaker 1: comes from a different direction. The shape changes again. The
• 43:48
  Speaker 1: heliosphere behaves somewhat like this, although the real physics is
• 43:52
  Speaker 1: far more complicated. The boundary can shift as the sun's
• 43:56
  Speaker 1: activity changes and as disturbances travel outward. Sometimes a burst
• 44:02
  Speaker 1: of activity from the sun sends waves through the solar wind.
• 44:06
  Speaker 1: These disturbances can travel outward and eventually interact with the
• 44:10
  Speaker 1: material beyond the heliopause. So even after Voyager has entered
• 44:14
  Speaker 1: interstellar space, the sun has not completely stopped speaking to it.
• 44:19
  Speaker 1: Its influence can still reach outward. A disturbance begins near
• 44:23
  Speaker 1: the sun. It travels through the thin stream of particles.
• 44:27
  Speaker 1: It reaches the distant boundary. and the boundary responds, slowly, quietly,
• 44:34
  Speaker 1: across billions of miles. This is one of the most
• 44:37
  Speaker 1: beautiful things Voyager taught us. The solar system is not
• 44:41
  Speaker 1: an isolated island floating in empty space. It is connected
• 44:46
  Speaker 1: to its surroundings. The sun shapes the region around it.
• 44:50
  Speaker 1: The galaxy presses back. Particles cross between the two. Magnetic
• 44:55
  Speaker 1: fields guide invisible motions. and disturbances can travel across the boundary.
• 45:01
  Speaker 1: The edge is therefore not the end of influence. It
• 45:04
  Speaker 1: is a meeting place, a transition, a region where one
• 45:08
  Speaker 1: environment slowly becomes another. And perhaps the most surprising part
• 45:13
  Speaker 1: is that Voyager discovered this while travelling through what appears,
• 45:16
  Speaker 1: to human eyes, to be almost complete emptiness. You could
• 45:21
  Speaker 1: look out from the spacecraft and see darkness, stars, nothing else.
• 45:26
  Speaker 1: But inside that darkness the instruments were quietly finding density, temperature, pressure,
• 45:33
  Speaker 1: magnetic fields and moving particles, things that your eyes could
• 45:37
  Speaker 1: never reveal. It is a little like sitting in a
• 45:40
  Speaker 1: completely dark room and discovering that the air is moving
• 45:45
  Speaker 1: because a tiny feather beside you keeps turning. You cannot
• 45:49
  Speaker 1: see the air, but the feather tells you it is there.
• 45:52
  Speaker 1: Voyager is that feather. a tiny machine drifting through a
• 45:56
  Speaker 1: vast darkness, sensitive enough to notice movements that would otherwise
• 46:01
  Speaker 1: remain invisible. And the longer it travelled, the clearer it
• 46:05
  Speaker 1: became that interstellar space was not simply an empty destination.
• 46:09
  Speaker 1: It had texture, it had motion, it had pressure, it
• 46:13
  Speaker 1: had waves, and it had its own quiet character. The
• 46:17
  Speaker 1: boundary of the sun's influence was therefore not the simple
• 46:21
  Speaker 1: final wall that anyone might have imagined. It was alive
• 46:25
  Speaker 1: with subtle changes, a place where the sun and the
• 46:28
  Speaker 1: galaxy touched without ever truly touching. And Voyager was floating
• 46:33
  Speaker 1: directly through that meeting place, carrying its faint measurements home
• 46:37
  Speaker 1: across the darkness. There was still more to discover, because
• 46:41
  Speaker 1: among those measurements was something even quieter, a persistent ripple
• 46:46
  Speaker 1: in the thin plasma surrounding the spacecraft. Not a sound
• 46:50
  Speaker 1: in the ordinary sense. not something human ears could hear
• 46:53
  Speaker 1: in space, but a tiny wave, detected by an instrument,
• 46:58
  Speaker 1: translated later into something your ears could understand, a faint
• 47:02
  Speaker 1: hum from beyond the sun's protective bubble, and somewhere in
• 47:06
  Speaker 1: that almost empty darkness, Voyager was still listening. The darkness
• 47:14
  Speaker 1: around Voyager is almost completely silent, not the peaceful silence
• 47:19
  Speaker 1: of a quiet room. something even deeper. There is no
• 47:23
  Speaker 1: air flowing around the spacecraft, no atmosphere carrying the ordinary
• 47:27
  Speaker 1: vibrations that become sound to your ears. If you were
• 47:31
  Speaker 1: somehow floating beside Voyager, you would not hear a bell ringing.
• 47:36
  Speaker 1: You would not hear an explosion. You would not hear
• 47:39
  Speaker 1: the spacecraft itself humming. Space is simply too thin for
• 47:43
  Speaker 1: ordinary sound to travel through in the way it does
• 47:46
  Speaker 1: on Earth. And yet, Voyager has sent something back that
• 47:50
  Speaker 1: scientists can turn into something you can hear. A faint hum,
• 47:54
  Speaker 1: a tiny ripple hidden in the almost empty space between
• 47:57
  Speaker 1: the stars. It is not a sound that Voyager heard
• 48:00
  Speaker 1: with a microphone. It is a measurement. The spacecraft detected
• 48:05
  Speaker 1: subtle waves moving through the thin, electrically active material surrounding it.
• 48:10
  Speaker 1: Scientists could take those measurements and translate them into a
• 48:14
  Speaker 1: form that human ears can understand. and when you listen
• 48:18
  Speaker 1: to that translated signal, it can feel strangely intimate, a
• 48:22
  Speaker 1: small sound representing an environment unimaginably far away. You can
• 48:27
  Speaker 1: imagine Voyager floating there, alone, surrounded by darkness, while tiny
• 48:33
  Speaker 1: disturbances move through the particles around it. The spacecraft cannot
• 48:38
  Speaker 1: hear them, but its instruments can notice them. And that
• 48:42
  Speaker 1: is enough. These waves are sometimes called plasma waves. The
• 48:46
  Speaker 1: word plasma may sound complicated, but you can think of
• 48:50
  Speaker 1: it simply as an extremely thin gas, made of tiny
• 48:54
  Speaker 1: electrically charged particles. Even in interstellar space, where everything looks empty,
• 49:00
  Speaker 1: there are still enough of these particles for subtle waves
• 49:03
  Speaker 1: to travel through them. The waves are incredibly faint. They
• 49:07
  Speaker 1: are not dramatic bursts. They are more like tiny ripples
• 49:10
  Speaker 1: spreading across a nearly motionless surface. Voyager detects them, records them.
• 49:17
  Speaker 1: and sends the information home. The signal then begins another journey,
• 49:21
  Speaker 1: from the spacecraft to Earth, across an enormous distance. For
• 49:26
  Speaker 1: more than 20 hours, the message travels at the speed
• 49:29
  Speaker 1: of light before it reaches the giant listening antennas on
• 49:33
  Speaker 1: our planet. And then, when Earth sends a reply, another
• 49:37
  Speaker 1: long wait begins. More than twenty hours again. You can
• 49:42
  Speaker 1: almost feel the patience built into the mission. A question
• 49:45
  Speaker 1: is sent. You wait, and wait, and wait. Eventually, the
• 49:51
  Speaker 1: spacecraft answers. That rhythm has been part of Voyager's life
• 49:55
  Speaker 1: for decades. But sometimes, the answer does not come. Sometimes
• 50:00
  Speaker 1: the tiny voice from the darkness becomes confused, or incomplete,
• 50:05
  Speaker 1: or almost meaningless. One of the most unsettling examples happened
• 50:10
  Speaker 1: when Voyager 1 began returning strange information about its condition.
• 50:15
  Speaker 1: Instead of a clean stream of useful measurements, the spacecraft
• 50:19
  Speaker 1: transmitted patterns that appeared chaotic. The information did not make sense.
• 50:24
  Speaker 1: It was as if Voyager were still speaking, but had
• 50:27
  Speaker 1: somehow forgotten how to form its sentences. Engineers had to
• 50:32
  Speaker 1: determine whether the spacecraft was still healthy, whether the problem
• 50:36
  Speaker 1: was in the instruments. or whether something deeper inside the
• 50:39
  Speaker 1: old machine had failed. The spacecraft was unimaginably far away.
• 50:44
  Speaker 1: There was no possibility of sending someone to repair it.
• 50:48
  Speaker 1: No technician could travel out there with a toolbox. No
• 50:51
  Speaker 1: replacement computer could be delivered. Everything had to be done remotely,
• 50:56
  Speaker 1: through radio commands, very slowly, very carefully. And then, years later,
• 51:03
  Speaker 1: an even more difficult problem appeared. In November of 2023,
• 51:08
  Speaker 1: Voyager 1 stopped sending useful engineering information. For months, the
• 51:14
  Speaker 1: spacecraft remained connected in the most fragile sense. Earth could
• 51:18
  Speaker 1: still detect that something was being transmitted, but the information
• 51:23
  Speaker 1: was no longer useful in the ordinary way. The problem
• 51:26
  Speaker 1: was traced to corrupted computer code inside the spacecraft's flight
• 51:30
  Speaker 1: data system. You can imagine this as a tiny set
• 51:33
  Speaker 1: of instructions inside an extremely old machine becoming damaged. The
• 51:39
  Speaker 1: spacecraft still had power. It still had its basic ability
• 51:43
  Speaker 1: to communicate, but an important part of its internal organisation
• 51:47
  Speaker 1: had become confused. And there was a difficult question. How
• 51:52
  Speaker 1: do you repair a computer that is more than 20
• 51:55
  Speaker 1: billion kilometres away? You cannot open it. You cannot replace
• 51:59
  Speaker 1: its memory. You cannot plug anything into it. You have
• 52:03
  Speaker 1: to persuade it to repair itself. The engineers eventually found
• 52:07
  Speaker 1: a way. Some of the damaged code could be moved
• 52:11
  Speaker 1: into other portions of the spacecraft's memory. It was a
• 52:14
  Speaker 1: little like discovering that a damaged page in an ancient
• 52:18
  Speaker 1: notebook could be carefully rewritten onto several unused pages elsewhere.
• 52:23
  Speaker 1: But even that simple description hides the extraordinary difficulty. The
• 52:28
  Speaker 1: computer was designed in another era. Its memory was tiny
• 52:32
  Speaker 1: compared with the machines you carry in your pocket today.
• 52:36
  Speaker 1: Its instructions were arranged in a system created when the
• 52:39
  Speaker 1: Voyager mission was still new, and every command had to
• 52:43
  Speaker 1: travel across the enormous distance between Earth and the spacecraft.
• 52:47
  Speaker 1: On April 18th, 2024, the process of transferring the information began.
• 52:53
  Speaker 1: A command left Earth. Then everyone waited. The message needed
• 52:58
  Speaker 1: about 22 and a half hours to reach Voyager. After that,
• 53:02
  Speaker 1: the spacecraft had to process the command. Then another 22
• 53:07
  Speaker 1: and a half hours would pass before the response could return.
• 53:10
  Speaker 1: One small mistake could mean another long wait. There was
• 53:14
  Speaker 1: no instant confirmation, no quick test, no direct connection, only patience.
• 53:21
  Speaker 1: And then, roughly two days later, something wonderful happened. Voyager
• 53:27
  Speaker 1: 1 began communicating properly again. The old spacecraft had responded.
• 53:32
  Speaker 1: After months of uncertainty, its voice had returned. You can
• 53:36
  Speaker 1: let yourself imagine that moment quietly. Somewhere in the darkness,
• 53:41
  Speaker 1: billions of kilometres away, a machine launched in the 1970s
• 53:46
  Speaker 1: had received a message from Earth. It had changed something
• 53:49
  Speaker 1: inside itself, and then it answered, not loudly, not dramatically,
• 53:55
  Speaker 1: just a faint radio signal arriving at a giant antenna
• 53:58
  Speaker 1: on Earth, a small stream of information, a confirmation that
• 54:03
  Speaker 1: the spacecraft was still there, still alive in its mechanical way,
• 54:08
  Speaker 1: still travelling, still listening to the environment around it, still
• 54:13
  Speaker 1: capable of sending a little piece of the darkness home.
• 54:17
  Speaker 1: And this is perhaps one of the strangest things about Voyager.
• 54:21
  Speaker 1: The discoveries are not only about planets or boundaries, Sometimes
• 54:26
  Speaker 1: the discovery is simply that the machine itself is still functioning.
• 54:30
  Speaker 1: Still remembering. Still answering. Still carrying its old instructions through
• 54:35
  Speaker 1: an environment for which it was never originally designed. And
• 54:39
  Speaker 1: somewhere around it, those tiny plasma waves continue to move.
• 54:43
  Speaker 1: The spacecraft measures them. Earth receives the measurements. Scientists translate them.
• 54:50
  Speaker 1: And eventually, you can hear a representation of those distant ripples.
• 54:55
  Speaker 1: Not the sound of space itself, but the sound of
• 54:58
  Speaker 1: information from space. A way for something invisible to become perceptible.
• 55:03
  Speaker 1: A way for the emptiness between the stars to leave
• 55:06
  Speaker 1: a tiny trace in human experience. And then the signal
• 55:10
  Speaker 1: fades back into silence. The spacecraft continues outward. The antennas
• 55:15
  Speaker 1: on Earth continue waiting. The distance continues growing. And the
• 55:20
  Speaker 1: old machine, still carrying its small memory and its fragile voice,
• 55:25
  Speaker 1: drifts quietly onward. There is nothing to hurry toward. You
• 55:29
  Speaker 1: are safe. There is nothing to do. You can simply
• 55:32
  Speaker 1: listen and drift. Because even now, somewhere beyond the planets,
• 55:37
  Speaker 1: a tiny traveller is still moving through the darkness. And perhaps,
• 55:43
  Speaker 1: in that darkness, another faint ripple is already passing by.
• 55:50
  Speaker 1: You have travelled a very long way with Voyager now,
• 55:53
  Speaker 1: past Jupiter, past Saturn, past Uranus, past Neptune, past the
• 55:59
  Speaker 1: familiar worlds, past the distant boundary where the sun's influence
• 56:04
  Speaker 1: begins to give way to the space between the stars.
• 56:07
  Speaker 1: And through all of it, one quiet question remains. How
• 56:12
  Speaker 1: has such an old machine managed to keep going? The
• 56:15
  Speaker 1: answer begins with something surprisingly small. The computers. You might
• 56:20
  Speaker 1: imagine that a spacecraft travelling billions of miles through deep
• 56:24
  Speaker 1: space is must contain enormous computing power. But Voyager was
• 56:28
  Speaker 1: built in the 1970s. Its computers are extraordinarily simple by
• 56:33
  Speaker 1: modern standards. Each spacecraft has only a tiny amount of memory.
• 56:39
  Speaker 1: So little, in fact, that by today's standards the memory
• 56:42
  Speaker 1: would seem almost impossibly small. You can think of it
• 56:46
  Speaker 1: as a very small notebook. A notebook with only a
• 56:49
  Speaker 1: few pages. And yet, that little notebook has guided a
• 56:53
  Speaker 1: spacecraft through decades of darkness. Voyager also carries an old-fashioned
• 56:58
  Speaker 1: magnetic tape system for storing scientific information. It does not
• 57:03
  Speaker 1: work like the storage inside your phone. It is closer
• 57:07
  Speaker 1: to a very carefully engineered mechanical recorder designed to preserve
• 57:11
  Speaker 1: information and play it back slowly when Earth is ready
• 57:15
  Speaker 1: to receive it. The technology is old. The spacecraft is old.
• 57:20
  Speaker 1: The instructions are old, and yet they continue to function.
• 57:24
  Speaker 1: That is part of what makes Voyager so unusual. It
• 57:28
  Speaker 1: is not a powerful machine. It is a patient machine,
• 57:31
  Speaker 1: a machine designed to keep doing a small number of things, reliably,
• 57:36
  Speaker 1: for an extraordinarily long time. Its computer processes instructions slowly
• 57:42
  Speaker 1: compared with modern electronics. Its radio transmitter is also surprisingly weak.
• 57:48
  Speaker 1: From the spacecraft, The radio signal begins its journey toward
• 57:52
  Speaker 1: Earth with only a small amount of energy. But by
• 57:56
  Speaker 1: the time that signal has crossed the enormous distance between
• 57:59
  Speaker 1: Voyager and our planet, it has become extraordinarily faint. So
• 58:04
  Speaker 1: faint that Earth needs enormous listening antennas to hear it.
• 58:08
  Speaker 1: These antennas are spread around the world. They are part
• 58:11
  Speaker 1: of NASA's Deep Space Network. You can imagine them as
• 58:15
  Speaker 1: giant ears pointed toward the darkness. They listen patiently, and
• 58:21
  Speaker 1: somewhere among all the noise of space, they search for
• 58:24
  Speaker 1: the tiny voice of Voyager. The signal has travelled across
• 58:28
  Speaker 1: an almost unimaginable distance. By the time it arrives, it
• 58:32
  Speaker 1: is barely more than a whisper, yet the antennas can
• 58:35
  Speaker 1: still detect it, and sometimes Voyager needs to turn that
• 58:39
  Speaker 1: whisper toward Earth very precisely. This is where another piece
• 58:44
  Speaker 1: of old technology becomes important. Small engines called thrusters can
• 58:49
  Speaker 1: gently adjust the spacecraft's orientation. Voyager 1 once used its
• 58:54
  Speaker 1: primary systems for these delicate adjustments. But decades later, engineers
• 59:00
  Speaker 1: needed another option. In 2017, Voyager 1 successfully used backup
• 59:06
  Speaker 1: thrusters that had not been used since its encounter with Saturn.
• 59:10
  Speaker 1: Think about that for a moment. A set of tiny
• 59:13
  Speaker 1: mechanical engines had been waiting quietly for decades. They had
• 59:17
  Speaker 1: not been needed since the spacecraft was still visiting the
• 59:20
  Speaker 1: outer planets. Then, after all those years, they were asked
• 59:25
  Speaker 1: to work again. And they did. A little movement. A
• 59:29
  Speaker 1: tiny adjustment, just enough to help the spacecraft keep its
• 59:33
  Speaker 1: antenna pointed toward Earth. There is something almost gentle about
• 59:37
  Speaker 1: the idea. Old machinery waking briefly from a very long rest.
• 59:43
  Speaker 1: Not becoming young again. Not becoming powerful. Simply continuing to
• 59:48
  Speaker 1: do what it was built to do. But nothing lasts forever.
• 59:52
  Speaker 1: Voyager's power supply is slowly weakening. The spacecraft uses a
• 59:57
  Speaker 1: small nuclear power system that has been producing electricity for decades.
• 1:00:02
  Speaker 1: It also provides heat, helping the spacecraft remain warm enough
• 1:00:06
  Speaker 1: for its systems to function. As time passes, that power
• 1:00:11
  Speaker 1: source becomes weaker. So engineers have had to make choices.
• 1:00:15
  Speaker 1: Some instruments have already been turned off. Others have been
• 1:00:19
  Speaker 1: carefully managed. The spacecraft cannot keep everything running forever. One
• 1:00:24
  Speaker 1: by one, functions must become quieter. Not because Voyager suddenly fails,
• 1:00:30
  Speaker 1: but because its available energy is gradually becoming smaller. It
• 1:00:34
  Speaker 1: is a slow fading, a little less power, a little
• 1:00:37
  Speaker 1: less warmth, a little less ability to operate, and eventually,
• 1:00:42
  Speaker 1: the spacecraft will no longer have enough energy to communicate
• 1:00:45
  Speaker 1: with Earth. The voice will disappear, but the journey will not.
• 1:00:50
  Speaker 1: This distinction is important. Silence does not mean stopping. Voyager
• 1:00:55
  Speaker 1: will continue moving through space because nothing needs to push
• 1:00:58
  Speaker 1: it along. It already has momentum. So even after the
• 1:01:03
  Speaker 1: final signal is received, the spacecraft will continue drifting. For
• 1:01:08
  Speaker 1: thousands of years. Then tens of thousands. Then far longer.
• 1:01:13
  Speaker 1: It will pass through regions of space that no human
• 1:01:16
  Speaker 1: instrument will be listening to. It will continue beyond the heliosphere.
• 1:01:21
  Speaker 1: Far beyond that lies the enormous, distant region associated with
• 1:01:26
  Speaker 1: the Oort cloud, where icy objects may surround the Sun
• 1:01:30
  Speaker 1: at distances vastly greater than the planet's. So, although it
• 1:01:35
  Speaker 1: is natural to say that Voyager has left the solar system,
• 1:01:38
  Speaker 1: there is an important quiet detail. Crossing the heliopause does
• 1:01:42
  Speaker 1: not mean reaching the absolute gravitational edge of the Sun's domain.
• 1:01:47
  Speaker 1: The Sun's influence extends much farther. Voyager has entered interstellar space,
• 1:01:52
  Speaker 1: but its physical journey through the broader solar system will
• 1:01:56
  Speaker 1: continue for an extraordinarily long time. Eventually the spacecraft may
• 1:02:01
  Speaker 1: pass relatively near other stars. The uploaded source describes distant
• 1:02:06
  Speaker 1: future stellar encounters for both Voyagers tens of thousands of
• 1:02:10
  Speaker 1: years from now, but perhaps the most remarkable thing Voyager
• 1:02:13
  Speaker 1: carries is not a scientific instrument. It is the Golden Record,
• 1:02:19
  Speaker 1: a gold-plated message prepared for a future that nobody could predict.
• 1:02:24
  Speaker 1: Inside are photographs, greetings, sounds from Earth, music, human voices,
• 1:02:31
  Speaker 1: pieces of our world carefully chosen and placed aboard a
• 1:02:35
  Speaker 1: spacecraft that might travel long after the people who built
• 1:02:39
  Speaker 1: it are gone. You can imagine the record floating quietly
• 1:02:43
  Speaker 1: through the darkness. There is no guarantee that anyone will
• 1:02:46
  Speaker 1: ever find it. There may never be another civilization nearby.
• 1:02:51
  Speaker 1: There may never be another hand reaching out to examine it.
• 1:02:54
  Speaker 1: The record may simply continue travelling forever. And that is
• 1:02:58
  Speaker 1: perfectly possible. Its purpose was never a promise. It was
• 1:03:02
  Speaker 1: an offering. A small collection of sounds and images from
• 1:03:06
  Speaker 1: one tiny world, carried outward by two machines. If something
• 1:03:11
  Speaker 1: someday finds Voyager... The record may tell them that somewhere,
• 1:03:15
  Speaker 1: around one ordinary star, there was a planet filled with oceans, forests, animals, music, voices,
• 1:03:23
  Speaker 1: and people who wondered what existed beyond the darkness. And
• 1:03:27
  Speaker 1: if nobody ever finds it, the record will still travel, quietly, patiently,
• 1:03:33
  Speaker 1: without needing an audience. That may be the most fitting
• 1:03:36
  Speaker 1: ending for Voyager. Not a dramatic final discovery. Not a
• 1:03:40
  Speaker 1: sudden disappearance. just a gradual fading, the instruments becoming quiet,
• 1:03:46
  Speaker 1: the radio becoming weaker, the giant antennas on Earth listening
• 1:03:50
  Speaker 1: for a signal that eventually will no longer arrive. And
• 1:03:54
  Speaker 1: beyond that silence, the spacecraft continuing onward. You can imagine
• 1:03:59
  Speaker 1: Earth becoming smaller behind it, the sun becoming another bright star,
• 1:04:04
  Speaker 1: the planets becoming distant memories stored inside an ancient machine,
• 1:04:09
  Speaker 1: and the golden record remaining there attached to the spacecraft,
• 1:04:14
  Speaker 1: carrying its little collection of earth into the dark. You
• 1:04:17
  Speaker 1: are safe. There is nothing to do. You can simply rest.
• 1:04:21
  Speaker 1: Because Voyager does not need to hurry. It has already
• 1:04:25
  Speaker 1: travelled farther than anyone who built it could have imagined.
• 1:04:29
  Speaker 1: And when its voice eventually becomes silent, the darkness will
• 1:04:32
  Speaker 1: not swallow the journey. It will simply become quiet. The
• 1:04:37
  Speaker 1: spacecraft will continue drifting. The stars will continue shining. The
• 1:04:42
  Speaker 1: planets will continue turning. The sun will continue sending its
• 1:04:46
  Speaker 1: thin stream of particles outward, and somewhere, very far away,
• 1:04:51
  Speaker 1: two small machines from Earth will continue moving through the
• 1:04:54
  Speaker 1: space between the stars. Their signals may one day be gone,
• 1:04:58
  Speaker 1: their instruments may one day be still, but their paths
• 1:05:02
  Speaker 1: will continue. And perhaps that is the final lesson hidden
• 1:05:06
  Speaker 1: inside their journey. You do not always have to be
• 1:05:09
  Speaker 1: heard to keep moving. Sometimes, it is enough to leave
• 1:05:13
  Speaker 1: something gentle behind. A photograph. A measurement. A message. A
• 1:05:19
  Speaker 1: tiny golden record. A faint trace of where you came from.
• 1:05:23
  Speaker 1: And then, quietly, you can keep drifting. And so, our
• 1:05:32
  Speaker 1: journey quietly comes to an end. Voyager is still drifting
• 1:05:36
  Speaker 1: through the darkness. Carrying a small memory of Earth into
• 1:05:39
  Speaker 1: the space between the stars, you are safe. There is
• 1:05:43
  Speaker 1: nothing to do now. Just breathe slowly. Let your body
• 1:05:47
  Speaker 1: become still and allow the quiet of deep space to
• 1:05:51
  Speaker 1: surround you. The stars will keep shining, the planets will
• 1:05:54
  Speaker 1: keep turning, and Voyager will keep drifting onward. For now,
• 1:05:59
  Speaker 1: you can simply rest and drift gently into the quiet.