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How Big is Our Solar System_ · Boring Science

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  Speaker 1: You're standing in your backyard on a clear night, looking
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  Speaker 1: up at the stars scattered across the darkness like diamonds
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  Speaker 1: on black velvet. Maybe you spot Jupiter hanging there like
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  Speaker 1: a bright beacon, or catch a glimpse of Mars with
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  Speaker 1: its subtle reddish glow. They look so close, don't they,
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  Speaker 1: like you could almost reach out and pluck them from
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  Speaker 1: the sky. But here's what will absolutely blow your mind.
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  Speaker 1: Those points of light you're casually observing represent distances so vast,
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  Speaker 1: so incomprehensibly enormous, that your brain literally cannot process them.
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  Speaker 1: We're not talking about driving to the next city over.
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  Speaker 1: We're not even talking about flying to another continent. We're
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  Speaker 1: talking about distances that make the entire Earth seem like
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  Speaker 1: a grain of sand on an infinite beach. So just
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  Speaker 1: how big is our solar system? And I mean really,
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  Speaker 1: truly big. By the end of this journey together, you're
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  Speaker 1: going to understand why this question has haunted astronomers for centuries,
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  Speaker 1: and why the answer is so mind-bending that it fundamentally
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  Speaker 1: changes how you see your place in the universe. If
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  Speaker 1: you find comfort in these gentle explorations of space and science,
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  Speaker 1: I'd be grateful if you'd consider subscribing and giving this
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  Speaker 1: video a like. The visuals are here for you, but
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  Speaker 1: feel free to close your eyes, breathe deep, and let
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  Speaker 1: your imagination drift through the solar winds as we uncover
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  Speaker 1: truths that will reshape everything you thought you knew. I
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  Speaker 1: should warn you, this video might be just too interesting
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  Speaker 1: to not skip and to consider watching till the end.
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  Speaker 1: It might accidentally keep you awake. I'd love to know
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  Speaker 1: where you're watching from tonight and what time it is
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  Speaker 1: for you. Feel free to drop your location and time
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  Speaker 1: in the comments below. Let's start. Before we dive deep
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  Speaker 1: into the cosmic abyss, I want you to do something
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  Speaker 1: for me. Think about the farthest you've ever travelled from home.
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  Speaker 1: Maybe it's a few hundred miles to visit family. Maybe
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  Speaker 1: it's thousands of miles to another country. Hold that distance
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  Speaker 1: in your mind, because we're about to put it into
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  Speaker 1: a perspective that will make your head spin. Our solar
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  Speaker 1: system isn't just big. It's so stupendously, astronomically, ridiculously massive,
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  Speaker 1: that even using the fastest spacecraft we've ever built, it
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  Speaker 1: would take you over 40,000 years just to reach the
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  Speaker 1: nearest star beyond our solar neighbourhood. And that's traveling at
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  Speaker 1: speeds that would circle the entire Earth in about 90 minutes.
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  Speaker 1: But here's the thing that's absolutely fascinating. For most of
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  Speaker 1: human history, we had no idea. Ancient civilizations looked up
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  Speaker 1: at the same sky you see tonight and thought the
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  Speaker 1: stars were just tiny lights painted on a celestial dome
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  Speaker 1: hovering maybe a few miles above their heads. They had
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  Speaker 1: no concept that they were staring into an abyss so
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  Speaker 1: deep it defies human comprehension. The journey to understanding our
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  Speaker 1: solar system's true scale is one of the most incredible
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  Speaker 1: detective stories in human history. It's a tale of brilliant
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  Speaker 1: minds who refused to accept what their eyes told them,
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  Speaker 1: who dared to measure the unmeasurable, and who discovered that
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  Speaker 1: reality is far stranger and more magnificent than anyone ever imagined.
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  Speaker 1: Let's start with something that seems simple but is actually revolutionary.
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  Speaker 1: What exactly do we mean when we say solar system?
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  Speaker 1: Most people think of the eight planets orbiting our sun,
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  Speaker 1: maybe throw in some asteroids and comets and call it
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  Speaker 1: a day. But that's like describing a vast metropolitan city
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  Speaker 1: by only mentioning the downtown skyscrapers while ignoring all the suburbs,
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  Speaker 1: industrial districts and outlying communities that stretch for hundreds of
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  Speaker 1: miles in every direction. Our solar system is more like
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  Speaker 1: a cosmic empire with the sun as the absolute ruler
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  Speaker 1: at its centre. Its gravitational influence extends so far into
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  Speaker 1: space that objects literally trillions of miles away still feel
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  Speaker 1: its pull and orbit around it in vast, slow-motion dances
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  Speaker 1: that take thousands of years to complete. Think about this
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  Speaker 1: for a moment. When you drop a ball, Earth's gravity
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  Speaker 1: pulls it down. That same force, gravity, is what keeps
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  Speaker 1: the moon orbiting around us. It's what keeps us orbiting
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  Speaker 1: around the sun. And amazingly, that solar gravitational influence doesn't
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  Speaker 1: just stop at Pluto, or even close to it. It
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  Speaker 1: reaches out into the cosmic darkness, grabbing hold of icy
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  Speaker 1: chunks of rock and frozen gases that are so far away.
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  Speaker 1: they exist in a realm where the Sun appears as
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  Speaker 1: nothing more than a slightly brighter star among countless others.
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  Speaker 1: So when we talk about how big our solar system
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  Speaker 1: really is, we're not just measuring the distance to Neptune
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  Speaker 1: or even poor, demoted Pluto. We're measuring the edge of
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  Speaker 1: our Sun's gravitational kingdom, the boundary where its influence finally
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  Speaker 1: weakens enough that other stars can steal away its most
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  Speaker 1: distant subjects. But before we venture into those mind-bending outer reaches,
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  Speaker 1: let's start our journey closer to home and work our
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  Speaker 1: way outward, building up your cosmic perspective one incredible distance
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  Speaker 1: at a time. Right now, you're sitting on a planet
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  Speaker 1: that's roughly 8,000 miles in diameter. That's pretty big, right?
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  Speaker 1: You could fit about four Earths lined up side by
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  Speaker 1: side across the width of Jupiter. but here's where things
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  Speaker 1: start to get interesting. The distance from Earth to our
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  Speaker 1: Moon is about 240,000 miles. That means you could fit
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  Speaker 1: about 30 Earths in the space between us and our
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  Speaker 1: closest celestial neighbour. Already, we're talking about distances that are
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  Speaker 1: hard to visualise. If you could drive to the Moon
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  Speaker 1: at highway speeds without stopping, it would take you about
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  Speaker 1: four months of continuous driving to get there. Four months
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  Speaker 1: of driving through empty space to reach that bright disk
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  Speaker 1: you can cover with your thumb. But the Moon is
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  Speaker 1: practically in our backyard compared to what comes next. Our
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  Speaker 1: Sun sits roughly 93 million miles away from Earth. This
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  Speaker 1: distance is so important to astronomy that we use it
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  Speaker 1: as a cosmic measuring stick called an astronomical unit, or
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  Speaker 1: AU for short. One AU equals about 93 million miles.
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  Speaker 1: To put this in perspective, if Earth were the size
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  Speaker 1: of a marble, the Sun would be about the size
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  Speaker 1: of a large beach ball, positioned about 85 feet away.
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  Speaker 1: But even at this scale, we're just getting started with
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  Speaker 1: the true immensity of our solar system. Let's take a
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  Speaker 1: quick trip through the planetary neighborhood, building up these distances
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  Speaker 1: in your mind. Venus, our closest planetary neighbour, comes within
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  Speaker 1: about 25 million miles of Earth at its closest approach.
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  Speaker 1: That's still about 100 times farther than the Moon. Mars,
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  Speaker 1: that rusty red world that captures so much of our imagination,
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  Speaker 1: sits anywhere from 35 to 250 million miles away, depending
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  Speaker 1: on where both planets are in their orbits. Jupiter, That
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  Speaker 1: massive gas giant with its swirling storms and dozens of
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  Speaker 1: moons orbits at an average distance of about 5 AUs
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  Speaker 1: from the Sun. That's roughly 465 million miles. At this distance,
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  Speaker 1: sunlight takes about 43 minutes to travel from our star
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  Speaker 1: to Jupiter's cloud tops. Think about that for a second.
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  Speaker 1: When you look at Jupiter through a telescope, you're not
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  Speaker 1: seeing it as it is right now. You're seeing it
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  Speaker 1: as it was nearly three quarters of an hour ago,
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  Speaker 1: because that's how long it took the light to travel
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  Speaker 1: across all that empty space to reach your eyes. Saturn,
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  Speaker 1: with its magnificent ring system, sits at about nine and
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  Speaker 1: a half AUs, or roughly 890 million miles from the Sun.
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  Speaker 1: The light you see reflecting off Saturn's rings left the
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  Speaker 1: Sun about an hour and 20 minutes ago. But here's
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  Speaker 1: where our journey starts to get really wild. Uranus, that
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  Speaker 1: tilted ice giant rolling along on its side, orbits at
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  Speaker 1: about 19 AUs from the Sun. That's over 1.5 billion miles. Neptune,
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  Speaker 1: the windiest planet in our solar system, sits at about
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  Speaker 1: 30 AUs, or roughly 2.5 billion miles from our central star.
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  Speaker 1: At Neptune's distance, the Sun appears about 900 times dimmer
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  Speaker 1: than it does from Earth. If you were standing on
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  Speaker 1: Neptune's surface, Assuming you could somehow survive the crushing cold
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  Speaker 1: and howling winds, the Sun would look like nothing more
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  Speaker 1: than a very bright star in an alien sky. And
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  Speaker 1: here's the kicker. Even at Neptune's incredible distance of nearly
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  Speaker 1: 3 billion miles from the Sun, we're barely getting started
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  Speaker 1: with our solar system's true size. Neptune isn't even close
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  Speaker 1: to the edge of our solar system. It's more like
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  Speaker 1: we've just walked out of the city centre and reached
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  Speaker 1: the first ring of suburbs. Beyond Neptune lies a realm
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  Speaker 1: that most people have never even heard of, yet it
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  Speaker 1: contains some of the most fascinating and mysterious objects in
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  Speaker 1: our entire solar system. This is where we encounter the
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  Speaker 1: Kuiper Belt, a vast ring of icy objects that extends
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  Speaker 1: from about 30 AUs all the way out to around
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  Speaker 1: 50 AUs from the Sun. Pluto, that beloved former planet,
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  Speaker 1: is actually just one resident of this cosmic neighbourhood. It
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  Speaker 1: orbits at an average distance of about 39 AUs, or
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  Speaker 1: roughly 3.5 billion miles from the Sun. But Pluto has
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  Speaker 1: company out there. Thousands upon thousands of icy worlds drift
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  Speaker 1: through this distant realm, most of them too small and
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  Speaker 1: too far away for us to see clearly, even with
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  Speaker 1: our most powerful telescopes. Some of these Kuiper Belt objects
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  Speaker 1: are absolutely massive. Eris, one of the objects whose discovery
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  Speaker 1: led to Pluto's reclassification, is actually larger than Pluto itself.
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  Speaker 1: and sits at an average distance of about 68 AUs
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  Speaker 1: from the Sun. That's over 6 billion miles away. At
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  Speaker 1: this distance, the Sun provides about as much warmth as
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  Speaker 1: a candle would from about 2 miles away. These are
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  Speaker 1: worlds locked in perpetual winter, where temperatures hover around negative
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  Speaker 1: 400 degrees Fahrenheit. Nitrogen, which makes up most of our atmosphere,
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  Speaker 1: freezes solid at these temperatures. But even the Kuiper Belt,
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  Speaker 1: vast as it is, represents only the beginning of our
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  Speaker 1: solar system's true extent. Beyond this realm of icy dwarfs
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  Speaker 1: lies something even more spectacular and mind-bending. It's a spherical
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  Speaker 1: shell of objects so distant that they exist in a
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  Speaker 1: kind of cosmic deep freeze, barely touched by our sun's
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  Speaker 1: warmth or light. This is called the Oort Cloud. named
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  Speaker 1: after Dutch astronomer Jan Oort, who first proposed its existence.
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  Speaker 1: The Oort cloud is where our solar system's story gets
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  Speaker 1: truly incredible, where distances become so large that we have
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  Speaker 1: to completely reimagine what we mean when we talk about
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  Speaker 1: our cosmic neighbourhood. The inner edge of the Oort cloud
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  Speaker 1: begins at roughly 2,000 AUs from the Sun, That's about
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  Speaker 1: 186 billion miles, or roughly two trillion miles, but that's
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  Speaker 1: just where it starts. The outer edge of the Oort
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  Speaker 1: cloud extends to somewhere between 50,000 and 100,000 AUs from
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  Speaker 1: the sun. Let me put that in perspective for you.
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  Speaker 1: The outer boundary of our solar system sits roughly one
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  Speaker 1: and a half light years away from the sun. A
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  Speaker 1: light year is the distance Light travels in one year,
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  Speaker 1: moving at the incredible speed of 186,000 miles per second.
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  Speaker 1: Even at this cosmic speed limit, it takes light over
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  Speaker 1: a year to travel from the Sun to the very
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  Speaker 1: edge of its gravitational influence. This means that our solar
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  Speaker 1: system is about three light years across in total diameter.
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  Speaker 1: The nearest star to our Sun, Proxima Centauri, sits just
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  Speaker 1: over four light years away, In other words, our solar
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  Speaker 1: system and the nearest star system are practically touching in
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  Speaker 1: cosmic terms, separated by a gap that's smaller than the
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  Speaker 1: diameter of either system. But here's what's absolutely staggering about
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  Speaker 1: these distances. Remember that spacecraft I mentioned earlier, the one
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  Speaker 1: that would take 40,000 years to reach the nearest star?
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  Speaker 1: That same spacecraft Travelling at about 37,000 miles per hour
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  Speaker 1: would take over 10,000 years just to reach the inner
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  Speaker 1: edge of the Oort cloud. To travel completely across our
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  Speaker 1: solar system from one side to the other would take
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  Speaker 1: roughly 30,000 years of continuous flight. Human civilisation as we
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  Speaker 1: know it, from the first cities to the present day,
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  Speaker 1: spans only about 10,000 years. our entire recorded history could
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  Speaker 1: pass three times over during a single journey across our
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  Speaker 1: solar system. And we're not done yet. Because within this
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  Speaker 1: vast sphere of gravitational influence, some truly bizarre and wonderful
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  Speaker 1: things are happening that challenge everything we think we know
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  Speaker 1: about planets, moons, and the nature of our cosmic neighborhood.
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  Speaker 1: The Oort Cloud isn't just a collection of random space
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  Speaker 1: debris floating in the cosmic void. It's actually a treasure
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  Speaker 1: trove of pristine remnants from the very formation of our
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  Speaker 1: solar system. Icy time capsules that have remained virtually unchanged
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  Speaker 1: for over 4 billion years. These objects are like cosmic fossils,
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  Speaker 1: preserving the original materials that swirled around our young sun
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  Speaker 1: when the planets were still coming together. Mind-blowing is that
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  Speaker 1: we what's absolutely barely scratched the surface of understanding what's
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  Speaker 1: actually out there. Scientists estimate that the Oort cloud contains
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  Speaker 1: somewhere between 1 trillion and 100 trillion individual objects. That's
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  Speaker 1: more objects than there are stars in our entire galaxy,
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  Speaker 1: all bound to our single sun by the invisible threads
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  Speaker 1: of gravity. Most of these objects are roughly the size
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  Speaker 1: of mountains or small cities, chunks of ice and rock
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  Speaker 1: that spend most of their time in the ultimate deep freeze.
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  Speaker 1: But occasionally, something disturbs one of these distant wanderers. Maybe
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  Speaker 1: it's a passing star whose gravity gives it a gentle nudge,
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  Speaker 1: or perhaps it's the gravitational influence of a massive planet
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  Speaker 1: in a neighbouring star system. Whatever the cause, some of
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  Speaker 1: these icy objects begin the long, slow journey inward toward
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  Speaker 1: the sun, This is where things get really spectacular. As
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  Speaker 1: these visitors from the outer darkness approach our inner solar system,
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  Speaker 1: the sun's heat begins to work its magic. The frozen
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  Speaker 1: gases start to sublimate, turning directly from solid to gas
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  Speaker 1: without ever becoming liquid. This creates the magnificent tails we
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  Speaker 1: see streaking across our night sky. We call these visitors comets,
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  Speaker 1: But they're really messengers from the very edge of our
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  Speaker 1: solar system, bringing us samples of materials that have been
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  Speaker 1: preserved in cosmic storage for billions of years. Some of
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  Speaker 1: the most famous comets in history have made this incredible journey.
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  Speaker 1: Halley's Comet, which returns every 76 years or so, spends
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  Speaker 1: most of its time way out beyond Neptune. taking a
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  Speaker 1: leisurely cruise through the outer reaches of our solar system
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  Speaker 1: before making its brief spectacular appearance in our inner neighbourhood.
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  Speaker 1: But here's something that will absolutely blow your mind. The
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  Speaker 1: journey these comets make from the Oort cloud to the
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  Speaker 1: inner solar system can take millions of years. Think about that.
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  Speaker 1: A comet might begin its journey toward Earth when our
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  Speaker 1: planet is in the middle of an ice age, with
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  Speaker 1: massive glaciers covering most of the continents. By the time
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  Speaker 1: that comet finally arrives to put on its light show
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  Speaker 1: in our sky, entire species have evolved and gone extinct,
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  Speaker 1: continents have shifted, and human civilization has risen from nothing
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  Speaker 1: to spacefaring technology. Now, you might be wondering how we
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  Speaker 1: know all this stuff about regions of space so distant
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  Speaker 1: that no spacecraft has ever visited them. How can scientists
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  Speaker 1: be so confident about the existence of the Oort Cloud
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  Speaker 1: when we can't even see most of the objects in it.
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  Speaker 1: This is where the detective work of astronomy gets really fascinating.
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  Speaker 1: It all comes down to the orbits of the comets
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  Speaker 1: we can observe. When astronomers plot the paths these cosmic
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  Speaker 1: visitors take, they find that many of them are coming
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  Speaker 1: from seemingly random directions in space. They're not clustered around
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  Speaker 1: the plane where the planets orbit, which is what you'd
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  Speaker 1: expect if they originated from the Kuiper Belt. Instead, they
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  Speaker 1: arrive from above, below, and all around us, suggesting they're
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  Speaker 1: coming from a spherical shell surrounding our entire solar system.
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  Speaker 1: By working backward from these orbital paths, scientists can calculate
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  Speaker 1: where these comets must have originated. It's like being a
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  Speaker 1: detective who finds footprints in the snow and uses them
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  Speaker 1: to figure out where the person came from, even if
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  Speaker 1: you never actually saw them walking. but the Oort cloud
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  Speaker 1: isn't the only mind-bending aspect of our solar system's size.
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  Speaker 1: There are other ways to measure and think about cosmic
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  Speaker 1: distances that reveal just how isolated we really are in
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  Speaker 1: the vast ocean of space. Consider this perspective. Light from
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  Speaker 1: the sun takes about eight minutes to reach Earth. That
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  Speaker 1: means when you step outside on a sunny day, the
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  Speaker 1: warmth you feel on your face left the sun's surface
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  Speaker 1: eight minutes ago. It's like having a conversation with someone
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  Speaker 1: where every word takes eight minutes to travel between you.
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  Speaker 1: But that eight-minute journey is nothing compared to the time
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  Speaker 1: it takes sunlight to reach the outer boundaries of our
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  Speaker 1: solar system. Light from the sun takes over four hours
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  Speaker 1: to reach Neptune. To reach the inner edge of the
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  Speaker 1: Oort cloud, that same light needs over 11 days, and
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  Speaker 1: to travel completely across our solar system to its farthest
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  Speaker 1: boundary would take sunlight roughly two and a half years.
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  Speaker 1: This means that if the sun suddenly went out, we
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  Speaker 1: wouldn't know about it for eight minutes. Neptune wouldn't know
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  Speaker 1: for over four hours. And the most distant objects in
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  Speaker 1: our solar system wouldn't realise their central star had died
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  Speaker 1: until over two years later. It's like living in a
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  Speaker 1: cosmic neighbourhood so large that news takes years to travel
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  Speaker 1: from house to house. Here's another way to wrap your
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  Speaker 1: brain around these distances. If you could shrink our entire
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  Speaker 1: solar system down so that the distance from the Sun
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  Speaker 1: to Neptune fit inside a football field, then the nearest
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  Speaker 1: star would still be about 7,000 miles away. That's like
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  Speaker 1: placing a football field in New York City and having
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  Speaker 1: the next nearest football field somewhere in Europe. But perhaps
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  Speaker 1: the most humbling way to understand our solar system's size
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  Speaker 1: is to think about it in terms of human exploration.
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  Speaker 1: We've sent robotic spacecraft to every planet in our solar system,
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  Speaker 1: and these mechanical explorers have revealed worlds of incredible beauty
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  Speaker 1: and complexity. But even our fastest and most advanced spacecraft
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  Speaker 1: move at speeds that make interstellar travel seem almost impossibly slow.
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  Speaker 1: Voyager 1, currently our most distant human-made object, has been
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  Speaker 1: travelling away from the Sun for over four decades. It's
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  Speaker 1: moving at roughly 38,000 miles per hour, which sounds incredibly fast,
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  Speaker 1: until you realise that at this speed, it would still
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  Speaker 1: take over 9,000 years to travel just one light-year, And remember,
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  Speaker 1: our solar system extends roughly one and a half light
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  Speaker 1: years in radius. Voyager 1 has travelled so far that
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  Speaker 1: it has actually left the heliosphere, the bubble of charged
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  Speaker 1: particles that the sun blows around itself like a cosmic wind.
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  Speaker 1: This spacecraft is now travelling through interstellar space, the realm
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  Speaker 1: between stars. yet it's still technically within our solar system's
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  Speaker 1: gravitational influence. It won't escape the sun's gravitational pull completely
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  Speaker 1: for another 30,000 years. Think about the implications of this.
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  Speaker 1: A spacecraft that has been travelling for longer than most
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  Speaker 1: people live, moving faster than any human has ever travelled,
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  Speaker 1: still hasn't reached the true edge of our solar system,
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  Speaker 1: and won't for hundreds of centuries to come. This is
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  Speaker 1: the scale we're dealing with when we talk about our
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  Speaker 1: cosmic neighbourhood. Distances so vast that they challenge our very
• 23:03
  Speaker 1: ability to comprehend them, yet this entire system, impossibly large
• 23:08
  Speaker 1: as it seems, is just a tiny speck in the
• 23:11
  Speaker 1: grander scheme of the universe. But size isn't the only
• 23:17
  Speaker 1: mind-bending aspect of our solar system. The sheer variety and
• 23:21
  Speaker 1: strangeness of the worlds contained within this vast realm would
• 23:26
  Speaker 1: seem like science fiction. if we didn't have photographs and
• 23:29
  Speaker 1: data proving their existence. We have moons with subsurface oceans
• 23:36
  Speaker 1: that might harbour life, planets where it rains diamonds, worlds
• 23:41
  Speaker 1: with methane lakes and nitrogen snow, and asteroids made almost
• 23:47
  Speaker 1: entirely of precious metals. There are places in our solar
• 23:50
  Speaker 1: system where the sun appears as nothing more than a
• 23:54
  Speaker 1: bright star, where a day lasts longer than a year,
• 23:58
  Speaker 1: where storms larger than our entire planet have been raging
• 24:02
  Speaker 1: for centuries. There are worlds so cold that the atmosphere
• 24:06
  Speaker 1: itself freezes and falls as snow, and others where the
• 24:11
  Speaker 1: surface pressure would crush you instantly, even if you could
• 24:15
  Speaker 1: somehow survive the acid rain. All of this incredible diversity
• 24:21
  Speaker 1: exists within the gravitational embrace of our single star, scattered
• 24:25
  Speaker 1: across distances that make the entire Earth seem like a
• 24:28
  Speaker 1: mote of dust. And we're only just beginning to explore
• 24:32
  Speaker 1: and understand these alien worlds that share our cosmic neighborhood.
• 24:36
  Speaker 1: The more we learn about our solar system's true size
• 24:39
  Speaker 1: and complexity, the more we realize how special and precious
• 24:44
  Speaker 1: our small blue world really is. In all this vast emptiness,
• 24:49
  Speaker 1: spanning light years of space and containing trillions of objects,
• 24:53
  Speaker 1: we know of only one place where life definitely exists,
• 24:58
  Speaker 1: where liquid water flows on the surface, where the temperature
• 25:02
  Speaker 1: and atmospheric conditions are just right for complex chemistry to flourish.
• 25:10
  Speaker 1: We are cosmic lottery winners, living on a planet that
• 25:13
  Speaker 1: sits in just the right place, with just the right conditions,
• 25:17
  Speaker 1: in a solar system that's perfectly arranged to support the
• 25:21
  Speaker 1: incredible complexity we call life. And understanding the true scale
• 25:27
  Speaker 1: of our cosmic home makes this miracle seem even more extraordinary.
• 25:32
  Speaker 1: But our solar system's immensity becomes even more staggering when
• 25:35
  Speaker 1: you consider the speeds at which everything is moving through
• 25:38
  Speaker 1: this vast cosmic arena. Right now, as you sit reading this,
• 25:44
  Speaker 1: You're not just spinning on Earth's axis at over 1,000
• 25:47
  Speaker 1: miles per hour. You're also hurtling around the Sun at
• 25:51
  Speaker 1: roughly 67,000 miles per hour. That's fast enough to circle
• 25:56
  Speaker 1: the entire Earth in about 22 minutes. Yet even at
• 26:01
  Speaker 1: these breakneck speeds, it takes our planet an entire year
• 26:05
  Speaker 1: to complete just one orbit around our star. Mars moving
• 26:10
  Speaker 1: more slowly in its larger orbit takes nearly two Earth
• 26:14
  Speaker 1: years to make the same journey. Jupiter requires almost 12 years.
• 26:22
  Speaker 1: Saturn takes nearly 30 years. And poor Neptune, trudging along
• 26:27
  Speaker 1: in the outer darkness, needs 165 Earth years to complete
• 26:32
  Speaker 1: a single orbit. This means that since Neptune was discovered
• 26:37
  Speaker 1: in 1846, it has completed less than one full orbit
• 26:42
  Speaker 1: around the Sun. When Neptune finally completes its first observed
• 26:47
  Speaker 1: orbit in 2011, it will have been a cosmic marathon
• 26:51
  Speaker 1: spanning multiple human generations. But here's where the scale becomes
• 26:56
  Speaker 1: truly mind-melting. Those orbital speeds that seem so impressive become
• 27:03
  Speaker 1: almost laughably slow when measured against the distances involved. Earth
• 27:08
  Speaker 1: travels roughly 600 million miles during its yearly journey around
• 27:13
  Speaker 1: the Sun, That's like driving around the Earth's equator 24,000 times.
• 27:20
  Speaker 1: Yet this incredible journey takes place entirely within what we
• 27:23
  Speaker 1: might call the inner suburbs of our solar system. The
• 27:28
  Speaker 1: outer planets are travelling even greater distances with each orbit,
• 27:32
  Speaker 1: but they're moving much more slowly. Neptune crawls along at
• 27:36
  Speaker 1: only about 12,000 miles per hour in its orbit, which
• 27:40
  Speaker 1: sounds fast, until you realise that's slower than our fastest spacecraft.
• 27:45
  Speaker 1: At Neptune's orbital speed, it would take over eight years
• 27:49
  Speaker 1: just to travel the distance between Earth and the Sun once.
• 27:54
  Speaker 1: Now imagine trying to send a message to someone living
• 27:57
  Speaker 1: on Neptune. Even if we could transmit a signal at
• 28:00
  Speaker 1: the speed of light, the fastest possible speed in the universe,
• 28:04
  Speaker 1: that message would take over four hours to reach them.
• 28:07
  Speaker 1: Their reply would take another four hours to get back
• 28:10
  Speaker 1: to you. You could start a conversation in the morning
• 28:13
  Speaker 1: and not get a response until dinner time. And that's
• 28:17
  Speaker 1: assuming they replied immediately. But communication delays are just the
• 28:21
  Speaker 1: beginning of the challenges posed by our solar system's enormous scale.
• 28:27
  Speaker 1: Consider what it means for space exploration. When we send
• 28:31
  Speaker 1: commands to a spacecraft orbiting Mars, those instructions can take
• 28:36
  Speaker 1: anywhere from 4 to 24 minutes to arrive depending on
• 28:40
  Speaker 1: where Mars is in its orbit relative to Earth. This
• 28:44
  Speaker 1: means that when something goes wrong with a Mars mission,
• 28:47
  Speaker 1: there's no real-time remote control from Earth. By the time
• 28:52
  Speaker 1: we see a problem developing and send corrective commands, the
• 28:55
  Speaker 1: spacecraft might have already crashed or moved far from its
• 28:59
  Speaker 1: intended path. Every Mars mission has to be smart enough
• 29:03
  Speaker 1: to handle emergencies on its own, making split-second decisions across
• 29:08
  Speaker 1: hundreds of millions of miles of empty space, the psychological challenges.
• 29:14
  Speaker 1: Imagine being an impact of these distances is just as
• 29:17
  Speaker 1: profound as the technical astronaut on a mission to Mars,
• 29:21
  Speaker 1: watching Earth shrink to a pale blue dot and then
• 29:24
  Speaker 1: disappear entirely among the stars. The isolation would be unlike
• 29:30
  Speaker 1: anything humans have ever experienced. You'd be farther from home
• 29:34
  Speaker 1: than anyone in history, in a realm where Earth appears
• 29:38
  Speaker 1: as nothing more than a faint speck of light, if
• 29:41
  Speaker 1: it's visible at all. And Mars is relatively close by
• 29:45
  Speaker 1: solar system standards. A mission to Jupiter or Saturn would
• 29:50
  Speaker 1: mean spending years in the cosmic wilderness, so far from Earth,
• 29:54
  Speaker 1: that radio signals would take nearly an hour and a
• 29:57
  Speaker 1: half to make the round trip. You could ask mission
• 30:00
  Speaker 1: control a question and literally take a nap before receiving
• 30:04
  Speaker 1: an answer. But perhaps the most humbling aspect of our
• 30:07
  Speaker 1: solar system's scale is how it reveals our cosmic insignificance
• 30:11
  Speaker 1: while simultaneously highlighting our incredible uniqueness. In all this vast emptiness,
• 30:17
  Speaker 1: across trillions of cubic miles of space, across distances that
• 30:22
  Speaker 1: light itself takes years to traverse, we know of only
• 30:27
  Speaker 1: one tiny oasis where life has taken hold and flourished.
• 30:32
  Speaker 1: The numbers are almost incomprehensible. Our solar system contains roughly 99.8%
• 30:40
  Speaker 1: empty space. If you could somehow remove all that emptiness
• 30:44
  Speaker 1: and pack together just the solid matter from all the planets, moons,
• 30:48
  Speaker 1: asteroids and comets, the resulting ball would be smaller than
• 30:52
  Speaker 1: our sun, and the sun itself, massive as it is,
• 30:56
  Speaker 1: would be lost like a grain of sand, in the
• 30:59
  Speaker 1: vastness of the space it illuminates. Yet within this seemingly
• 31:04
  Speaker 1: barren immensity, we find worlds of breathtaking beauty and complexity. Europa,
• 31:10
  Speaker 1: one of Jupiter's moons, likely contains more liquid water beneath
• 31:14
  Speaker 1: its icy surface than all of Earth's oceans combined. Titan,
• 31:19
  Speaker 1: Saturn's largest moon, has lakes and rivers of liquid methane
• 31:24
  Speaker 1: flowing across its surface under a thick orange atmosphere. Enceladus
• 31:30
  Speaker 1: shoots geysers of water ice into space from its south pole,
• 31:35
  Speaker 1: creating one of Saturn's rings from its own subsurface ocean.
• 31:40
  Speaker 1: Each of these worlds represents a unique experiment in planetary science,
• 31:46
  Speaker 1: a different answer to the question of what happens when gravity,
• 31:50
  Speaker 1: chemistry and time interact under varying conditions. Some are frozen wastelands,
• 31:59
  Speaker 1: where the air itself would freeze solid. Others are pressure cookers,
• 32:05
  Speaker 1: where lead would melt and flow like water. Still others
• 32:09
  Speaker 1: might harbour the ingredients for life in hidden oceans beneath
• 32:12
  Speaker 1: miles of ice. The diversity is staggering, and it exists
• 32:17
  Speaker 1: across distances that make these worlds more isolated from each
• 32:20
  Speaker 1: other than any places on Earth have ever been. The
• 32:25
  Speaker 1: gap between Jupiter's moons is larger than the distance between
• 32:29
  Speaker 1: Earth and our moon. The space between Saturn's major moons
• 32:34
  Speaker 1: dwarfs the distance between continents on our planet. This isolation
• 32:39
  Speaker 1: has allowed each world to evolve its own unique characteristics
• 32:44
  Speaker 1: over billions of years. Unlike Earth, where weather systems and
• 32:50
  Speaker 1: ocean currents eventually mix and homogenise conditions around the globe,
• 32:55
  Speaker 1: These distant worlds have developed in cosmic solitude, creating environments
• 33:00
  Speaker 1: so alien that they challenge our very understanding of what
• 33:04
  Speaker 1: a planet can be. Consider Uranus, that strange world rolling
• 33:09
  Speaker 1: on its side like a cosmic bowling ball. Something in
• 33:13
  Speaker 1: its distant past, perhaps a collision with another planet-sized object,
• 33:17
  Speaker 1: knocked it over so that its axis of rotation is
• 33:20
  Speaker 1: tilted 98 degrees from vertical. This means that Uranus experiences
• 33:26
  Speaker 1: seasons lasting 21 Earth years, with each pole alternately facing
• 33:32
  Speaker 1: the Sun for decades at a time, while the other
• 33:35
  Speaker 1: hemisphere endures decades of darkness. Or think about Venus, Earth's
• 33:40
  Speaker 1: so-called twin, where the greenhouse effect has run completely out
• 33:43
  Speaker 1: of control. The surface temperature is hot enough to melt lead,
• 33:47
  Speaker 1: the atmospheric pressure is crushing, and it rains sulfuric acid.
• 33:52
  Speaker 1: This hellish world sits just 25 million miles away from us,
• 33:57
  Speaker 1: at its closest approach, yet it might as well be
• 34:00
  Speaker 1: in another universe for all the similarity it bears to
• 34:03
  Speaker 1: our temperate, life-friendly planet. These extreme variations exist within our
• 34:08
  Speaker 1: single solar system, bound together by the gravity of one star,
• 34:13
  Speaker 1: yet separated by distances so vast that each world has
• 34:16
  Speaker 1: become a unique laboratory for planetary physics and chemistry. The
• 34:21
  Speaker 1: isolation imposed by space has allowed each planet its own story.
• 34:26
  Speaker 1: Two and major moon to tell explore its own evolutionary
• 34:30
  Speaker 1: path without interference from its neighbours, and we're still discovering
• 34:34
  Speaker 1: new chapters in these stories. In recent decades, our robotic
• 34:39
  Speaker 1: explorers have revealed that several moons in the outer solar
• 34:42
  Speaker 1: system likely contain more liquid water than Earth. They've found
• 34:46
  Speaker 1: organic compounds, the building blocks of life, scattered throughout the
• 34:51
  Speaker 1: solar system. They've detected seasonal changes on worlds billions of
• 34:55
  Speaker 1: miles from the sun, and discovered that even in the coldest,
• 34:59
  Speaker 1: most distant regions of our cosmic neighbourhood, dynamic processes are
• 35:04
  Speaker 1: still shaping planetary surfaces. The scale of our solar system
• 35:08
  Speaker 1: means that we're essentially exploring multiple alien worlds, each as
• 35:13
  Speaker 1: complex and varied as Earth itself, scattered across a volume
• 35:17
  Speaker 1: of space so large it defies human intuition. Every new
• 35:22
  Speaker 1: mission reveals surprises that force us to reconsider what we
• 35:26
  Speaker 1: thought we knew about planetary science, about the conditions necessary
• 35:30
  Speaker 1: for life, and about the incredible diversity of worlds that
• 35:34
  Speaker 1: can exist around a single star. But as vast as
• 35:38
  Speaker 1: our solar system appears from our earthbound perspective, it represents
• 35:42
  Speaker 1: just the tiniest fraction of the cosmic story. The distances
• 35:47
  Speaker 1: we've been exploring as mind-bendingly large as they seem, are
• 35:51
  Speaker 1: nothing compared to the spaces between stars, between galaxies, between
• 35:56
  Speaker 1: the largest structures in the universe. Our entire solar system,
• 36:03
  Speaker 1: from the sun to the farthest reaches of the Oort cloud,
• 36:07
  Speaker 1: could fit comfortably within the space between our sun and
• 36:11
  Speaker 1: the nearest star. All of this incredible diversity All of
• 36:15
  Speaker 1: these alien worlds and cosmic phenomena we've been discussing exist
• 36:19
  Speaker 1: within what amounts to a tiny bubble in the vast
• 36:23
  Speaker 1: ocean of interstellar space. The nearest star system, Alpha Centauri,
• 36:29
  Speaker 1: contains at least three stars and potentially several planets. Yet
• 36:34
  Speaker 1: the gap between our solar system and theirs is so
• 36:37
  Speaker 1: enormous that it would take our fastest spacecraft tens of
• 36:40
  Speaker 1: thousands of years to cross it. The distances we measure
• 36:44
  Speaker 1: within our solar system in astronomical units would need to
• 36:48
  Speaker 1: be measured in light years when we start talking about
• 36:51
  Speaker 1: interstellar space, and even that represents just the beginning of
• 36:55
  Speaker 1: cosmic scale. Our galaxy, the Milky Way, contains somewhere between
• 37:01
  Speaker 1: 200 and 400 billion stars, most of them likely surrounded
• 37:06
  Speaker 1: by their own planetary systems. The distances between these stars
• 37:11
  Speaker 1: are so vast that if you could somehow travel at
• 37:14
  Speaker 1: the speed of light, it would take you 100,000 years
• 37:18
  Speaker 1: to cross from one side of our galaxy to the other.
• 37:22
  Speaker 1: Yet our galaxy is just one of trillions in the
• 37:25
  Speaker 1: observable universe, separated by distances that make the space between
• 37:31
  Speaker 1: stars look cramped by comparison. The nearest major galaxy to ours, Andromeda,
• 37:39
  Speaker 1: sits over two million light years away. Light that left
• 37:43
  Speaker 1: Andromeda when our earliest human ancestors were learning to use
• 37:47
  Speaker 1: tools is just now reaching Earth. This cosmic perspective makes
• 37:52
  Speaker 1: our solar system seem almost cozy by comparison, yet it
• 37:57
  Speaker 1: also highlights just how special and rare our little corner
• 38:01
  Speaker 1: of the universe might be. In all the vast emptiness
• 38:05
  Speaker 1: of space, across distances that challenge the very limits of
• 38:10
  Speaker 1: human comprehension, we find ourselves in this one perfect spot
• 38:14
  Speaker 1: where conditions are just right for liquid water, for complex chemistry,
• 38:20
  Speaker 1: for the incredible phenomenon we call life. The more we
• 38:24
  Speaker 1: understand about our solar system's true scale, the more we
• 38:28
  Speaker 1: appreciate both our cosmic insignificance and our incredible good fortune.
• 38:33
  Speaker 1: We are temporary arrangements of atoms that have somehow become
• 38:36
  Speaker 1: conscious enough to contemplate the very vastness that contains us,
• 38:41
  Speaker 1: living on a tiny world in a vast system that
• 38:44
  Speaker 1: is itself a mere speck in an almost infinite universe.
• 38:49
  Speaker 1: Yet within this seemingly impossible scale, something truly extraordinary is
• 38:54
  Speaker 1: happening right now that makes our solar system even more
• 38:58
  Speaker 1: remarkable than its sheer size alone would suggest. As we speak,
• 39:05
  Speaker 1: our entire cosmic neighbourhood is moving through space at speeds
• 39:09
  Speaker 1: that would make your head spin, carrying us on a
• 39:13
  Speaker 1: journey through the galaxy that spans distances so vast they
• 39:18
  Speaker 1: make even our solar system's dimensions seem quaint. Right now,
• 39:23
  Speaker 1: our sun, along with all its planets, moons, asteroids and comets,
• 39:28
  Speaker 1: is racing through the Milky Way galaxy at roughly 500,000
• 39:33
  Speaker 1: miles per hour. That's fast enough to circle the Earth
• 39:36
  Speaker 1: in about three minutes. Yet even at this breakneck pace,
• 39:41
  Speaker 1: it takes our solar system approximately 225 million years to
• 39:46
  Speaker 1: complete just one orbit around the centre of our galaxy.
• 39:52
  Speaker 1: Think about that timeline for a moment. The last time
• 39:55
  Speaker 1: our solar system was in this exact position in the galaxy,
• 40:00
  Speaker 1: dinosaurs ruled the Earth. The next time we complete this
• 40:04
  Speaker 1: cosmic circuit, our sun will be noticeably older and dimmer,
• 40:09
  Speaker 1: and who knows what form life on Earth might have taken,
• 40:13
  Speaker 1: if it still exists at all. but our galactic journey
• 40:16
  Speaker 1: is just one layer of motion in this cosmic ballet.
• 40:20
  Speaker 1: Our entire galaxy is also moving, racing through the universe
• 40:25
  Speaker 1: toward a collision with the Andromeda Galaxy that won't occur
• 40:28
  Speaker 1: for another four and a half billion years. When that
• 40:31
  Speaker 1: cosmic crash finally happens, the combined gravitational forces will completely
• 40:37
  Speaker 1: reshape both galaxies, flinging stars into new orbits and potentially
• 40:42
  Speaker 1: ejecting our solar system into the lonely depths of intergalactic space.
• 40:47
  Speaker 1: Even more mind-bending is the realisation that space itself is expanding.
• 40:53
  Speaker 1: The very fabric of the universe is stretching, carrying galaxies
• 40:57
  Speaker 1: away from each other at speeds that increase with distance.
• 41:01
  Speaker 1: This means that the most distant objects we can observe
• 41:04
  Speaker 1: are racing away from us faster than the speed of light.
• 41:08
  Speaker 1: Not because they're moving through space that quickly, but because
• 41:11
  Speaker 1: space itself is expanding between us. This cosmic expansion has
• 41:16
  Speaker 1: a profound effect on how we measure distances in our universe,
• 41:20
  Speaker 1: and raises fascinating questions about what lies beyond the edge
• 41:24
  Speaker 1: of our solar system. As space expands, the gravitational influence
• 41:30
  Speaker 1: of our sun becomes relatively weaker compared to the expansion
• 41:34
  Speaker 1: of the universe itself. This suggests that there might be
• 41:39
  Speaker 1: an absolute outer boundary to our solar system, beyond which
• 41:43
  Speaker 1: objects would be swept away by cosmic expansion, rather than
• 41:47
  Speaker 1: held in solar orbit. Scientists estimate this boundary might lie
• 41:53
  Speaker 1: somewhere around 100,000 astronomical units from the Sun, roughly where
• 42:00
  Speaker 1: we think the outer edge of the Oort cloud exists.
• 42:03
  Speaker 1: This isn't a coincidence. The edge of our solar system
• 42:07
  Speaker 1: might literally be defined by the point where our Sun's
• 42:10
  Speaker 1: gravity no longer compete with the expansion of space itself.
• 42:16
  Speaker 1: But here's something that will absolutely scramble your brain. The
• 42:20
  Speaker 1: expansion of space means that objects at the very edge
• 42:24
  Speaker 1: of our solar system are slowly but constantly drifting away
• 42:28
  Speaker 1: from the sun. Over cosmic timescales, our solar system is
• 42:33
  Speaker 1: actually shrinking as its most distant members are gradually stolen
• 42:37
  Speaker 1: away by the expanding universe. This process is so slow
• 42:42
  Speaker 1: that it's essentially imperceptible on human timescales. It would take
• 42:47
  Speaker 1: trillions of years for this expansion to have any noticeable
• 42:51
  Speaker 1: effect on even the outer reaches of the Oort cloud.
• 42:55
  Speaker 1: But the fact that it's happening at all reveals something
• 42:58
  Speaker 1: profound about the nature of our cosmic neighbourhood, and its
• 43:02
  Speaker 1: place in the larger universe. Our solar system isn't a static,
• 43:07
  Speaker 1: unchanging structure frozen in space and time. It's a dynamic,
• 43:11
  Speaker 1: evolving system that's constantly responding to forces, both internal and external.
• 43:17
  Speaker 1: Planets migrate inward and outward over millions of years due
• 43:21
  Speaker 1: to gravitational interactions. The Sun gradually grows brighter as it ages,
• 43:27
  Speaker 1: slowly pushing the habitable zone outward. Passing stars occasionally disturb
• 43:33
  Speaker 1: the Oort cloud, sending showers of comets racing toward the
• 43:38
  Speaker 1: inner solar system. even the shape of our solar system
• 43:42
  Speaker 1: changes over time. The orbits of the planets aren't perfectly
• 43:47
  Speaker 1: stable circles, but complex ellipses that shift and wobble due
• 43:52
  Speaker 1: to mutual gravitational influences. These orbital variations occur over such
• 43:59
  Speaker 1: long timescales that they're invisible to human observation, but they're
• 44:03
  Speaker 1: profound enough to affect climate patterns on Earth over hundreds
• 44:06
  Speaker 1: of thousands of years. Jupiter Our solar system's gravitational giant
• 44:12
  Speaker 1: acts like a cosmic shepherd, using its massive gravity to
• 44:17
  Speaker 1: protect the inner planets from asteroid and comet impacts, while
• 44:22
  Speaker 1: simultaneously stirring up the asteroid belt and occasionally flinging dangerous
• 44:28
  Speaker 1: objects toward Earth. Without Jupiter's protective influence, life on Earth
• 44:34
  Speaker 1: might never have had the stable conditions necessary to evolve
• 44:37
  Speaker 1: complex forms. But Jupiter's protection comes with a price. Its
• 44:43
  Speaker 1: gravitational influence also prevents the asteroid belt from coalescing into
• 44:47
  Speaker 1: a proper planet. The combined mass of all asteroids in
• 44:51
  Speaker 1: the belt is less than that of our Moon, scattered
• 44:54
  Speaker 1: across a region of space larger than the orbit of Mars.
• 44:58
  Speaker 1: These rocky fragments represent the building materials for a world
• 45:01
  Speaker 1: that never was, prevented from forming by Jupiter's overwhelming gravitational dominance.
• 45:08
  Speaker 1: This gravitational choreography extends throughout our solar system, creating resonances
• 45:13
  Speaker 1: and patterns that govern the motion of countless objects. Some
• 45:18
  Speaker 1: asteroids are locked in orbital resonances with Jupiter, completing exactly
• 45:23
  Speaker 1: two orbits for every one Jupiter completes, or three orbits
• 45:27
  Speaker 1: for every two. These mathematical relationships create gaps in the
• 45:32
  Speaker 1: asteroid belt where objects simply cannot maintain stable orbits. Similar
• 45:37
  Speaker 1: resonances exist throughout the outer solar system. Pluto is locked
• 45:41
  Speaker 1: in a 2 to 3 resonance with Neptune, meaning it
• 45:45
  Speaker 1: completes exactly two orbits for every three that Neptune completes.
• 45:50
  Speaker 1: This gravitational partnership has kept Pluto's orbit stable for billions
• 45:54
  Speaker 1: of years, despite the fact that their orbital paths actually
• 45:59
  Speaker 1: cross when viewed from above. The more we study these
• 46:02
  Speaker 1: gravitational relationships, the more we realise that our solar system
• 46:06
  Speaker 1: is less like a collection of independent objects orbiting the sun,
• 46:11
  Speaker 1: and more like a single integrated system where every component
• 46:16
  Speaker 1: influences every other component, change the mass or orbit of
• 46:21
  Speaker 1: any major planet, and the effects would ripple throughout the
• 46:25
  Speaker 1: entire system, potentially destabilising orbits and sending planets careening into
• 46:32
  Speaker 1: new paths. This interconnectedness becomes even more remarkable when you
• 46:38
  Speaker 1: consider the timescales involved. The gravitational influence of Jupiter on
• 46:43
  Speaker 1: Earth's orbit operates over cycles lasting hundreds of thousands of years.
• 46:49
  Speaker 1: These tiny orbital variations help drive ice ages and other
• 46:52
  Speaker 1: long-term climate changes on our planet. The gravitational dance between
• 46:57
  Speaker 1: Earth and Moon gradually slows our planet's rotation, while pushing
• 47:01
  Speaker 1: the Moon slowly away from us. In the early days
• 47:05
  Speaker 1: of our solar system, the Moon was much closer to Earth,
• 47:10
  Speaker 1: and our planet spun much faster. A day lasted only
• 47:14
  Speaker 1: about six hours, and the Moon appeared enormous in our sky,
• 47:19
  Speaker 1: creating tides that would have been catastrophically large by today's standards.
• 47:25
  Speaker 1: Over billions of years, tidal friction has gradually slowed Earth's rotation,
• 47:31
  Speaker 1: and pushed the Moon to its current distance of about 240,000 miles.
• 47:36
  Speaker 1: This process continues today. The Moon is still slowly spiralling
• 47:42
  Speaker 1: away from Earth at about an inch and a half
• 47:45
  Speaker 1: per year. In the distant future, assuming no other catastrophes intervene,
• 47:51
  Speaker 1: the Moon will be so far away that it will
• 47:54
  Speaker 1: no longer be able to create total solar eclipses. The
• 47:58
  Speaker 1: remarkable cosmic coincidence that makes the moon appear almost exactly
• 48:02
  Speaker 1: the same size as the sun in our sky is temporary,
• 48:06
  Speaker 1: existing only during this brief moment in cosmic history. These
• 48:11
  Speaker 1: ongoing changes remind us that the solar system we observe
• 48:14
  Speaker 1: today is just a snapshot of a continuously evolving system.
• 48:20
  Speaker 1: The distances we measure, the orbital periods we calculate, the
• 48:24
  Speaker 1: relationships between objects that seem so permanent and stable, are
• 48:29
  Speaker 1: all slowly shifting on timescales that dwarf human civilization. Four
• 48:34
  Speaker 1: and a half billion years ago, when our solar system
• 48:37
  Speaker 1: was young, the arrangement of planets was quite different from
• 48:41
  Speaker 1: what we see today. Jupiter and Saturn likely migrated inward
• 48:47
  Speaker 1: toward the sun, before being pulled back outward by their
• 48:50
  Speaker 1: gravitational interaction with each other. This migration may have scattered
• 48:55
  Speaker 1: the original asteroid belt and disrupted the formation of planets
• 49:00
  Speaker 1: in the inner solar system. Some scientists think there may
• 49:05
  Speaker 1: have been additional planets in the early solar system that
• 49:08
  Speaker 1: were ejected into interstellar space during these chaotic rearrangements. These
• 49:14
  Speaker 1: rogue planets, if they exist, would now be wandering through
• 49:18
  Speaker 1: the galaxy as cosmic orphans, no longer bound to any star.
• 49:23
  Speaker 1: Recent astronomical surveys have begun to detect objects that might
• 49:27
  Speaker 1: be these ejected worlds, dark and cold remnants of planetary
• 49:31
  Speaker 1: systems that once were. The scale of these processes, both
• 49:36
  Speaker 1: in terms of distance and time, challenges our ability to
• 49:40
  Speaker 1: comprehend the true nature of our cosmic neighborhood. We're not
• 49:46
  Speaker 1: just living in a large solar system. We're living in
• 49:49
  Speaker 1: an ancient dynamic system that has been evolving for billions
• 49:53
  Speaker 1: of years and will continue evolving for billions more. Our
• 49:59
  Speaker 1: perspective on this evolution is incredibly limited. Human civilization spans
• 50:05
  Speaker 1: perhaps 10,000 years. written history covers only a few thousand years.
• 50:13
  Speaker 1: Even our most advanced astronomical observations extend back only a
• 50:18
  Speaker 1: few centuries. Yet the processes that shape our solar system
• 50:22
  Speaker 1: operate over time scales of millions and billions of years.
• 50:26
  Speaker 1: It's like trying to understand the flow of a river
• 50:29
  Speaker 1: by observing a single drop of water for a microsecond.
• 50:33
  Speaker 1: We can see the immediate motion, but we miss the
• 50:35
  Speaker 1: large occurrence, the seasonal variations, the long-term changes in the
• 50:40
  Speaker 1: river's course. Our view of the solar system is similarly
• 50:45
  Speaker 1: constrained by our brief existence within it. But here's what
• 50:49
  Speaker 1: makes this limitation both humbling and inspiring. Despite existing for
• 50:55
  Speaker 1: such a tiny fraction of our solar system's history, despite
• 50:59
  Speaker 1: being confined to a single planet in this vast cosmic arena,
• 51:04
  Speaker 1: we've managed to piece together the story of our solar
• 51:07
  Speaker 1: system's formation evolution, and ultimate fate. We've sent robotic explorers
• 51:15
  Speaker 1: to every major planet, mapped the orbits of thousands of
• 51:19
  Speaker 1: asteroids and comets, and detected planets orbiting distant stars. This
• 51:25
  Speaker 1: achievement becomes even more remarkable when you consider the scale
• 51:29
  Speaker 1: we're dealing with. We've managed to study objects billions of
• 51:33
  Speaker 1: miles away using instruments that fit in our hands. We've
• 51:37
  Speaker 1: calculated the masses of planets by observing how they affect
• 51:41
  Speaker 1: the motion of their moons. We've determined the composition of
• 51:45
  Speaker 1: distant worlds by analysing the light they reflect or emit.
• 51:49
  Speaker 1: Every measurement, every observation, every calculation represents a triumph of
• 51:54
  Speaker 1: human ingenuity over the vast distances that separate us from
• 51:59
  Speaker 1: the objects we study. When we look at Saturn's rings
• 52:03
  Speaker 1: through a telescope, we're gathering light that has travelled for
• 52:06
  Speaker 1: over an hour through empty space to reach us. When
• 52:10
  Speaker 1: we receive data from a spacecraft at Jupiter, those radio
• 52:15
  Speaker 1: signals have crossed 400 million miles of vacuum. The fact
• 52:18
  Speaker 1: that we can study our solar system at all, given
• 52:21
  Speaker 1: its enormous scale and our tiny size within it, is
• 52:25
  Speaker 1: perhaps as remarkable as any of the discoveries we've made.
• 52:30
  Speaker 1: We are cosmic detectives piecing together clues from across billions
• 52:35
  Speaker 1: of miles of space and billions of years of time,
• 52:39
  Speaker 1: gradually building a picture of our place in this vast system.
• 52:44
  Speaker 1: And that picture keeps getting more complex and more beautiful
• 52:48
  Speaker 1: with every new discovery. Recent missions have revealed that several
• 52:53
  Speaker 1: moons in the outer solar system contain subsurface oceans that
• 52:57
  Speaker 1: might harbour life, We've discovered that even small asteroids can
• 53:03
  Speaker 1: have their own tiny moons. We've found that the space
• 53:06
  Speaker 1: between planets isn't empty, but filled with dust, charged particles,
• 53:11
  Speaker 1: and magnetic fields that create invisible highways and barriers throughout
• 53:16
  Speaker 1: our solar system. Each new revelation adds another layer to
• 53:21
  Speaker 1: our understanding of just how intricate and interconnected this vast
• 53:25
  Speaker 1: system really is. The distances that once seemed like empty
• 53:29
  Speaker 1: voids are actually filled with subtle influences and hidden relationships.
• 53:35
  Speaker 1: The objects that appear as simple points of light in
• 53:37
  Speaker 1: our telescopes turn out to be complex worlds with their
• 53:40
  Speaker 1: own weather, geology, and unique characteristics. Our solar system isn't
• 53:46
  Speaker 1: just big. It's not just old. It's not just complex.
• 53:51
  Speaker 1: It's all of these things simultaneously. operating on scales of distance,
• 53:55
  Speaker 1: time and intricacy that push the very limits of human comprehension.
• 54:01
  Speaker 1: And we've only just begun to explore it. The sheer
• 54:04
  Speaker 1: magnitude of what we're dealing with becomes even more staggering
• 54:09
  Speaker 1: when you realise that everything we've discussed so far represents
• 54:13
  Speaker 1: just the objects we know about. The truth is, our
• 54:17
  Speaker 1: solar system is filled with countless objects that remain completely
• 54:22
  Speaker 1: invisible to us. hidden in the cosmic darkness beyond the
• 54:26
  Speaker 1: reach of even our most powerful telescopes. Consider this mind-bending fact.
• 54:34
  Speaker 1: For every asteroid we've discovered and catalogued, there are likely
• 54:38
  Speaker 1: thousands more that we haven't detected yet. The asteroid belt
• 54:42
  Speaker 1: alone probably contains over a million objects larger than half
• 54:47
  Speaker 1: a mile across, and millions more smaller fragments that we'll
• 54:52
  Speaker 1: never be able to track individually. Each of these represents
• 54:56
  Speaker 1: a potential world in miniature, with its own unique composition, rotation,
• 55:01
  Speaker 1: and orbital characteristics. But asteroids are just the beginning. Throughout
• 55:07
  Speaker 1: the Kuiper Belt and scattered disk, there are likely tens
• 55:11
  Speaker 1: of thousands of objects larger than 60 miles across that
• 55:15
  Speaker 1: we haven't discovered yet. Some of these undiscovered worlds might
• 55:19
  Speaker 1: be larger than some of the moons we know about.
• 55:22
  Speaker 1: They're out there right now, silently orbiting in the darkness,
• 55:27
  Speaker 1: waiting for our technology to advance enough to spot them.
• 55:30
  Speaker 1: The Oort cloud presents an even more extreme case of
• 55:34
  Speaker 1: cosmic hide-and-seek. Remember those trillions of objects I mentioned earlier?
• 55:41
  Speaker 1: We've directly observed maybe a few dozen of them, and
• 55:44
  Speaker 1: only when they venture close enough to the sun to
• 55:47
  Speaker 1: develop visible tails as comets. The vast majority of Oort
• 55:53
  Speaker 1: cloud objects remain completely invisible to us, too small and
• 55:58
  Speaker 1: too distant to reflect enough sunlight for our telescopes to detect.
• 56:03
  Speaker 1: This means that our solar system is far more populous
• 56:07
  Speaker 1: than we can currently observe. It's like trying to estimate
• 56:10
  Speaker 1: the population of a vast city at night when most
• 56:13
  Speaker 1: of the buildings have their lights turned off. You can
• 56:17
  Speaker 1: see the bright downtown core and a few scattered neighbourhoods,
• 56:21
  Speaker 1: but the majority of the urban landscape remains hidden in darkness.
• 56:25
  Speaker 1: What makes this even more fascinating is that we're discovering
• 56:29
  Speaker 1: new objects all the time, and each discovery forces us
• 56:33
  Speaker 1: to revise our understanding of our solar system's structure and history.
• 56:38
  Speaker 1: In recent decades, we've found objects in the outer solar
• 56:42
  Speaker 1: system that don't fit neatly into our existing categories. Some
• 56:47
  Speaker 1: follow highly elliptical orbits that take them far beyond Pluto
• 56:51
  Speaker 1: before swinging back toward the Sun. Others seem to be
• 56:55
  Speaker 1: influenced by gravitational forces that we can't fully explain. These
• 57:00
  Speaker 1: discoveries have led some scientists to propose the existence of
• 57:03
  Speaker 1: additional planets in our solar system, worlds so distant and
• 57:07
  Speaker 1: dim that we haven't detected them yet. The hypothetical Planet 9,
• 57:12
  Speaker 1: if it exists, would orbit somewhere between 200 and 1,000
• 57:17
  Speaker 1: astronomical units from the Sun. That's so far away that
• 57:22
  Speaker 1: it would receive almost no heat from our star, existing
• 57:25
  Speaker 1: in a perpetual deep freeze where temperatures hover near absolute zero.
• 57:31
  Speaker 1: Finding such an object would be like trying to spot
• 57:34
  Speaker 1: a black marble rolling around in a football stadium with
• 57:37
  Speaker 1: only a penlight for illumination. It might be out there
• 57:41
  Speaker 1: right now, following its slow, stately orbit through the outer darkness,
• 57:46
  Speaker 1: completely invisible to our current technology, but gradually revealing its
• 57:51
  Speaker 1: presence through its gravitational influence on other objects. The search
• 57:57
  Speaker 1: for these hidden worlds represents one of the most exciting
• 58:01
  Speaker 1: frontiers in solar system exploration. Every few months, automated sky
• 58:07
  Speaker 1: surveys discover new objects in the outer reaches of our
• 58:11
  Speaker 1: cosmic neighbourhood. Some turn out to be relatively ordinary chunks
• 58:16
  Speaker 1: of ice and rock, but others surprise us with unusual
• 58:20
  Speaker 1: characteristics that challenge our understanding of how planets and small
• 58:24
  Speaker 1: bodies form and evolve. The process of discovery itself reveals
• 58:29
  Speaker 1: just how vast the search space really is. Astronomers have
• 58:33
  Speaker 1: to examine millions of images, looking for tiny points of
• 58:37
  Speaker 1: light that move slowly against the background of distant stars.
• 58:41
  Speaker 1: It's incredibly tedious work, like looking for a specific grain
• 58:45
  Speaker 1: of sand on a beach, but the payoff can be revolutionary.
• 58:50
  Speaker 1: When we do find these distant objects, studying them presents
• 58:54
  Speaker 1: its own set of challenges. They're so far away that
• 58:59
  Speaker 1: even our largest telescopes can barely make them out as
• 59:02
  Speaker 1: more than points of light. determining their size, composition, and
• 59:08
  Speaker 1: orbital characteristics requires years of careful observation and sophisticated analysis.
• 59:16
  Speaker 1: But here's what's truly remarkable about these discoveries. Each new
• 59:20
  Speaker 1: object we find adds another piece to the puzzle of
• 59:23
  Speaker 1: our solar system's formation and evolution. These distant worlds are
• 59:29
  Speaker 1: like cosmic fossils, preserving information about the conditions that existed
• 59:34
  Speaker 1: when our solar system was young. They're time capsules from
• 59:39
  Speaker 1: an era when the planets were still forming and the
• 59:43
  Speaker 1: architecture of our cosmic neighbourhood was being established. The more
• 59:46
  Speaker 1: we discover about these outer realms, the more we realise
• 59:50
  Speaker 1: that our solar system's influence extends even farther than we
• 59:53
  Speaker 1: previously thought. Some of the most distant objects we've found
• 59:57
  Speaker 1: are still clearly bound to our sun's gravity, following orbits
• 1:00:01
  Speaker 1: that take thousands of years to complete. This suggests that
• 1:00:05
  Speaker 1: our solar system's gravitational reach might extend even beyond the
• 1:00:10
  Speaker 1: traditional boundaries of the Oort cloud. Think about what this
• 1:00:14
  Speaker 1: means for our understanding of cosmic distances. We're not just
• 1:00:19
  Speaker 1: dealing with a solar system that's a few light years across.
• 1:00:23
  Speaker 1: we're potentially looking at a region of space where our
• 1:00:26
  Speaker 1: sun's influence can be detected across distances that approach the
• 1:00:31
  Speaker 1: nearest neighbouring star systems. The boundary between what belongs to
• 1:00:35
  Speaker 1: our solar system and what belongs to interstellar space becomes
• 1:00:39
  Speaker 1: increasingly blurry the farther out we look. This blurring of
• 1:00:44
  Speaker 1: boundaries reflects a deeper truth about the nature of space itself.
• 1:00:50
  Speaker 1: The universe isn't neatly divided into separate, isolated systems. Instead,
• 1:00:56
  Speaker 1: it's a continuous web of gravitational influences, magnetic fields, and
• 1:01:01
  Speaker 1: particle flows that connect everything to everything else across vast distances.
• 1:01:08
  Speaker 1: Our solar system exists within this larger cosmic environment, influenced
• 1:01:13
  Speaker 1: by and influencing its surroundings in ways we're only beginning
• 1:01:17
  Speaker 1: to understand. The passage of nearby stars can disturb the
• 1:01:21
  Speaker 1: Oort cloud, sending showers of comets racing toward the inner
• 1:01:25
  Speaker 1: solar system. Interstellar dust and gas flow through our cosmic neighborhood,
• 1:01:31
  Speaker 1: subtly affecting the orbits of our most distant objects. Even
• 1:01:36
  Speaker 1: more fascinating is the realization that our solar system is
• 1:01:40
  Speaker 1: currently passing through what astronomers call the local bubble. a
• 1:01:44
  Speaker 1: region of space that's been carved out by ancient supernova explosions.
• 1:01:50
  Speaker 1: This bubble of hot, thin gas extends for hundreds of
• 1:01:54
  Speaker 1: light years in all directions, and our solar system has
• 1:01:58
  Speaker 1: been travelling through it for several million years. The local
• 1:02:03
  Speaker 1: bubble affects our solar system in subtle but measurable ways.
• 1:02:08
  Speaker 1: It influences the flow of cosmic rays that reach our planets,
• 1:02:13
  Speaker 1: affects the density of interstellar material in our neighbourhood, and
• 1:02:18
  Speaker 1: even plays a role in the long-term climate patterns on Earth.
• 1:02:24
  Speaker 1: We're not just isolated observers of the universe. We're active
• 1:02:28
  Speaker 1: participants in cosmic processes that span galactic distances and timescales.
• 1:02:37
  Speaker 1: This cosmic context makes our solar system's already impressive dimensions
• 1:02:41
  Speaker 1: seem even more remarkable, we're not just dealing with a
• 1:02:45
  Speaker 1: large collection of objects orbiting a single star. We're looking
• 1:02:49
  Speaker 1: at a complex, dynamic system that interacts with its galactic
• 1:02:53
  Speaker 1: environment across multiple scales of distance and time. The heliosphere,
• 1:02:59
  Speaker 1: that bubble of charged particles blown out by our sun,
• 1:03:02
  Speaker 1: extends roughly 100 astronomical units in all directions. This might
• 1:03:07
  Speaker 1: sound small compared to the Oort Cloud, but it represents
• 1:03:10
  Speaker 1: our solar system's most direct interaction with the interstellar medium.
• 1:03:16
  Speaker 1: Where the solar wind meets the interstellar wind, complex physics
• 1:03:20
  Speaker 1: creates shockwaves and boundary layers that affect everything from cosmic
• 1:03:25
  Speaker 1: ray penetration to the behaviour of interstellar dust. Voyager 1
• 1:03:32
  Speaker 1: and Voyager 2, our most distant robotic explorers, have crossed
• 1:03:36
  Speaker 1: this boundary, and are now sending back our first direct
• 1:03:40
  Speaker 1: measurements of the interstellar environment. What they've found is that
• 1:03:45
  Speaker 1: the space between stars isn't empty or uniform. It's filled
• 1:03:50
  Speaker 1: with magnetic fields, charged particles, and structures that reveal the
• 1:03:55
  Speaker 1: complex history of stellar explosions, stellar winds, and galactic processes
• 1:04:01
  Speaker 1: that have shaped our cosmic neighborhood over millions of years.
• 1:04:06
  Speaker 1: These discoveries are rewriting our understanding of where our solar
• 1:04:10
  Speaker 1: system ends and interstellar space begins. The traditional view of
• 1:04:16
  Speaker 1: a clear boundary is giving way to a more nuanced
• 1:04:20
  Speaker 1: picture of overlapping zones of influence that extend across multiple
• 1:04:24
  Speaker 1: light years. Our solar system doesn't have a sharp edge. Instead,
• 1:04:30
  Speaker 1: it gradually transitions into the larger galactic environment through a
• 1:04:35
  Speaker 1: series of complex boundary regions. But perhaps the most mind-bending
• 1:04:41
  Speaker 1: aspect of our solar system's scale is how it relates
• 1:04:45
  Speaker 1: to time itself. The distances we've been discussing aren't just
• 1:04:50
  Speaker 1: measurements of space, they're also measurements of time. Light from
• 1:04:55
  Speaker 1: the sun takes over two years to reach the outer
• 1:04:58
  Speaker 1: edge of the Oort cloud. which means that the most
• 1:05:01
  Speaker 1: distant parts of our solar system exist in a different
• 1:05:05
  Speaker 1: temporal relationship with our star than we do. If something
• 1:05:08
  Speaker 1: dramatic happened to the sun right now, we'd know about
• 1:05:12
  Speaker 1: it in eight minutes, but the most distant objects in
• 1:05:15
  Speaker 1: our solar system wouldn't be affected for over two years.
• 1:05:20
  Speaker 1: In a very real sense, different parts of our solar
• 1:05:24
  Speaker 1: system exist in different moments of solar time, separated not
• 1:05:28
  Speaker 1: just by distance, but by the finite speed of light itself.
• 1:05:33
  Speaker 1: This temporal aspect of solar system distances becomes even more
• 1:05:37
  Speaker 1: striking when you consider orbital periods. Objects in the inner
• 1:05:43
  Speaker 1: solar system complete their orbits in months or years, while
• 1:05:47
  Speaker 1: objects in the Oort cloud might take millions of years
• 1:05:51
  Speaker 1: to complete a single journey around the Sun. Some of
• 1:05:55
  Speaker 1: the comets we observe today began their inward journey, when
• 1:05:59
  Speaker 1: early human ancestors were just learning to use stone tools.
• 1:06:03
  Speaker 1: The scale of these temporal relationships challenges our intuitive understanding
• 1:06:08
  Speaker 1: of what it means for objects to be part of
• 1:06:10
  Speaker 1: the same system. Can we really say that a comet
• 1:06:14
  Speaker 1: with a million-year orbital period is part of the same
• 1:06:17
  Speaker 1: solar system as Earth, which completes its orbit in just
• 1:06:21
  Speaker 1: one year? In what sense do these objects share a
• 1:06:26
  Speaker 1: common present when their relationship with the sun operates on
• 1:06:30
  Speaker 1: such vastly different time scales? These questions touch on deep
• 1:06:35
  Speaker 1: philosophical issues about the nature of time and causality in
• 1:06:41
  Speaker 1: cosmic systems. Our solar system isn't just large in space,
• 1:06:47
  Speaker 1: it's large in time, encompassing processes and relationships that operate
• 1:06:53
  Speaker 1: across multiple scales of temporal experience. The formation of our
• 1:06:57
  Speaker 1: solar system itself took place over millions of years, a
• 1:07:01
  Speaker 1: process so gradual that no single moment can be identified
• 1:07:06
  Speaker 1: as the instant when it came into being. The gravitational
• 1:07:10
  Speaker 1: collapse of the original solar nebula, the accretion of planetesimals
• 1:07:15
  Speaker 1: into planets, the migration of giant planets to their current orbits,
• 1:07:20
  Speaker 1: the late heavy bombardment that scarred the inner planets, all
• 1:07:25
  Speaker 1: of these processes unfolded over timescales that dwarf human comprehension.
• 1:07:31
  Speaker 1: Yet here we are, temporary arrangements of matter that have
• 1:07:36
  Speaker 1: achieved consciousness just long enough to contemplate the vast system
• 1:07:40
  Speaker 1: that contains us. We exist for what amounts to an
• 1:07:45
  Speaker 1: instant in solar system time, Yet we've managed to piece
• 1:07:49
  Speaker 1: together the story of our cosmic home's four and a
• 1:07:51
  Speaker 1: half billion year history. This achievement becomes even more remarkable
• 1:07:56
  Speaker 1: when you consider that we're not just studying our solar
• 1:07:59
  Speaker 1: system from within it. We're studying it while moving through
• 1:08:03
  Speaker 1: it at tremendous speeds. As I mentioned earlier, we're racing
• 1:08:09
  Speaker 1: around the sun at 67,000 miles per hour, while the
• 1:08:13
  Speaker 1: sun itself hurtles through the galaxy at half a million
• 1:08:17
  Speaker 1: miles per hour We're conducting our observations from a platform
• 1:08:21
  Speaker 1: that's constantly in motion through the very system we're trying
• 1:08:24
  Speaker 1: to understand. It's like trying to map a vast city
• 1:08:28
  Speaker 1: while riding on a speeding train that never stops. The
• 1:08:33
  Speaker 1: perspective is constantly shifting. Distances and angles are always changing.
• 1:08:39
  Speaker 1: And you can never step outside the system to get
• 1:08:41
  Speaker 1: an objective, stationary view of the whole thing. Yet somehow,
• 1:08:47
  Speaker 1: Through careful observation and mathematical analysis, we've managed to create
• 1:08:52
  Speaker 1: accurate maps of our cosmic neighbourhood and understand how all
• 1:08:57
  Speaker 1: its components fit together. The technology that makes this possible
• 1:09:02
  Speaker 1: is itself a testament to human ingenuity in the face
• 1:09:06
  Speaker 1: of cosmic scale. Our most powerful telescopes can detect objects
• 1:09:11
  Speaker 1: billions of times fainter than what the naked eye can see.
• 1:09:16
  Speaker 1: Our spacecraft navigation systems can plot courses across billions of
• 1:09:21
  Speaker 1: miles with accuracy measured in kilometres. Our mathematical models can
• 1:09:25
  Speaker 1: predict the positions of planets centuries into the future with
• 1:09:30
  Speaker 1: remarkable precision. But even our most advanced technology is humbled
• 1:09:35
  Speaker 1: by the sheer scale of what we're trying to study.
• 1:09:39
  Speaker 1: The James Webb Space Telescope, humanity's most powerful space-based observatory,
• 1:09:47
  Speaker 1: can peer deeper into the universe than ever before, yet
• 1:09:51
  Speaker 1: it still can't resolve individual objects in the Oort cloud.
• 1:09:56
  Speaker 1: The Voyager spacecraft, our most distant emissaries, have been traveling
• 1:10:01
  Speaker 1: for over four decades and are still within our solar
• 1:10:05
  Speaker 1: system's gravitational influence. These limitations remind us that despite all
• 1:10:12
  Speaker 1: our technological achievements, we're still dealing with distances and time
• 1:10:16
  Speaker 1: scales that challenge the very limits of what's possible to
• 1:10:20
  Speaker 1: observe and understand. We're cosmic detectives working with incomplete evidence,
• 1:10:26
  Speaker 1: trying to reconstruct the story of our solar system from
• 1:10:30
  Speaker 1: the limited clues we can gather. Yet the picture that
• 1:10:33
  Speaker 1: emerges from this detective work is breathtaking in its scope
• 1:10:36
  Speaker 1: and beauty. Our solar system isn't just a collection of
• 1:10:41
  Speaker 1: objects scattered through empty space, It's an integrated, dynamic system,
• 1:10:46
  Speaker 1: where every component influences every other component across vast distances
• 1:10:51
  Speaker 1: and long timescales. It's a cosmic ecosystem where the movement
• 1:10:56
  Speaker 1: of planets affects asteroid orbits, where the solar wind shapes
• 1:11:00
  Speaker 1: the magnetic environments of distant moons, where the passage of
• 1:11:05
  Speaker 1: nearby stars can trigger comet showers that rain down on
• 1:11:08
  Speaker 1: the inner planets. The more we learn about our solar
• 1:11:11
  Speaker 1: system's true scale and complexity, the more we appreciate what
• 1:11:15
  Speaker 1: an extraordinary place we call home. In all this vast emptiness,
• 1:11:21
  Speaker 1: across all these mind-bending distances, in all this cosmic time,
• 1:11:26
  Speaker 1: we find ourselves on a small blue world that happens
• 1:11:30
  Speaker 1: to exist in just the right place, under just the
• 1:11:33
  Speaker 1: right conditions, for liquid water to flow and complex chemistry
• 1:11:37
  Speaker 1: to flourish. The odds against this seem almost impossibly small.
• 1:11:43
  Speaker 1: Yet here we are, conscious beings who have emerged from
• 1:11:47
  Speaker 1: this cosmic dance of gravity and chemistry and time, capable
• 1:11:52
  Speaker 1: of contemplating the very system that gave birth to us.
• 1:11:57
  Speaker 1: We are the universe becoming aware of itself, temporary patterns
• 1:12:02
  Speaker 1: of matter and energy that have learned to measure cosmic
• 1:12:05
  Speaker 1: distances and ponder their own origins. And this brings us
• 1:12:09
  Speaker 1: to perhaps the most mind-bending realization of all. When we
• 1:12:14
  Speaker 1: talk about measuring our solar system, we're not just dealing
• 1:12:17
  Speaker 1: with static distances frozen in space like mile markers on
• 1:12:21
  Speaker 1: a cosmic highway. Every single measurement we make is constantly
• 1:12:25
  Speaker 1: changing because nothing in our solar system ever stands still.
• 1:12:32
  Speaker 1: Right now, as you absorb these cosmic dimensions, Mars is
• 1:12:36
  Speaker 1: either racing toward Earth at roughly 15,000 miles per hour,
• 1:12:41
  Speaker 1: or speeding away from us at the same rate, depending
• 1:12:45
  Speaker 1: on where we both happen to be in our respective orbits.
• 1:12:49
  Speaker 1: Jupiter is lumbering along its massive orbital path, but even
• 1:12:53
  Speaker 1: its seemingly slow motion carries it at over 29,000 miles
• 1:12:58
  Speaker 1: per hour through the void. This constant motion creates what
• 1:13:03
  Speaker 1: astronomers call the dynamic geometry of space. The distance between
• 1:13:09
  Speaker 1: any two objects in our solar system is never the
• 1:13:12
  Speaker 1: same from one moment to the next. When mission planners
• 1:13:16
  Speaker 1: calculate trajectories for spacecraft, they're not just plotting a course
• 1:13:19
  Speaker 1: through space, they're choreographing a dance through four-dimensional space-time, timing
• 1:13:25
  Speaker 1: arrivals to intercept moving targets across billions of miles of
• 1:13:28
  Speaker 1: constantly shifting cosmic real estate. Consider what this means for
• 1:13:33
  Speaker 1: something as simple as measuring the distance to Pluto. When
• 1:13:38
  Speaker 1: Pluto is at its closest approach to the Sun, it
• 1:13:41
  Speaker 1: sits roughly 2.5 billion miles away from us. But when
• 1:13:46
  Speaker 1: it swings out to the farthest point in its highly
• 1:13:49
  Speaker 1: elliptical orbit, that distance increases to over 4.5 billion miles.
• 1:13:56
  Speaker 1: That's like having your neighbour's house sometimes be down the street,
• 1:14:00
  Speaker 1: and sometimes be in another state, all while you're trying
• 1:14:03
  Speaker 1: to give someone directions. But Pluto's wandering is nothing compared
• 1:14:08
  Speaker 1: to the truly extreme objects lurking in the outer darkness
• 1:14:12
  Speaker 1: of our solar system. Some of these distant wanderers follow
• 1:14:16
  Speaker 1: orbits so stretched and elongated that they spend most of
• 1:14:20
  Speaker 1: their time in the cosmic equivalent of Antarctica, only occasionally
• 1:14:25
  Speaker 1: swooping close enough to the Sun to warm up above
• 1:14:28
  Speaker 1: the temperature of liquid nitrogen. Take Sedna, one of the
• 1:14:31
  Speaker 1: most distant objects we've discovered in our solar system. At
• 1:14:35
  Speaker 1: its closest approach to the Sun, Sedna comes within about
• 1:14:39
  Speaker 1: 76 astronomical units, which sounds close until you realise that
• 1:14:44
  Speaker 1: it's still over 7 billion miles away, more than twice
• 1:14:47
  Speaker 1: Neptune's distance. But when Sedna reaches the far end of
• 1:14:52
  Speaker 1: its incredibly elongated orbit, it travels out to roughly 937
• 1:14:56
  Speaker 1: astronomical units from the Sun. That's over 87 billion miles,
• 1:15:04
  Speaker 1: so far away that the Sun would appear as nothing
• 1:15:06
  Speaker 1: more than a slightly brighter star in a sky full
• 1:15:09
  Speaker 1: of stars. Sedna takes approximately 11,400 years to complete just
• 1:15:16
  Speaker 1: one orbit around the Sun. Think about that timeline. The
• 1:15:20
  Speaker 1: last time Sedna was at its current position, humans were
• 1:15:23
  Speaker 1: just emerging from the last ice age, developing agriculture and
• 1:15:28
  Speaker 1: building the first permanent settlements. The next time it returns
• 1:15:33
  Speaker 1: to this same spot, our civilization will likely be unrecognizable,
• 1:15:37
  Speaker 1: assuming it still exists at all. But here's what makes
• 1:15:42
  Speaker 1: Sedna truly extraordinary. Its orbit is so distant and so
• 1:15:47
  Speaker 1: stretched that something must have gravitationally nudged it into this
• 1:15:51
  Speaker 1: bizarre trajectory. The sun alone couldn't have created such an
• 1:15:56
  Speaker 1: extreme orbital path. This suggests that either a passing star
• 1:16:00
  Speaker 1: disturbed Sedna's orbit long ago, or there's another massive object
• 1:16:04
  Speaker 1: in our outer solar system that we haven't discovered yet.
• 1:16:08
  Speaker 1: This brings us to one of the most tantalising mysteries
• 1:16:11
  Speaker 1: currently haunting astronomy. Multiple lines of evidence suggest there might
• 1:16:16
  Speaker 1: be an undiscovered planet lurking in the far reaches of
• 1:16:21
  Speaker 1: our solar system, something astronomers have dubbed Planet Nine. If
• 1:16:27
  Speaker 1: it exists, this world would be roughly the size of Neptune,
• 1:16:32
  Speaker 1: orbiting somewhere between 200 and 1,200 astronomical units from the Sun.
• 1:16:38
  Speaker 1: At those distances, Planet 9 would be so cold and
• 1:16:42
  Speaker 1: so dim that finding it would be like trying to
• 1:16:45
  Speaker 1: spot a charcoal briquette floating in the darkness of a
• 1:16:48
  Speaker 1: football stadium. It would receive so little heat from the
• 1:16:52
  Speaker 1: Sun that its surface temperature would hover around negative, 370
• 1:16:57
  Speaker 1: degrees Fahrenheit, cold enough to freeze nitrogen solid. The search
• 1:17:02
  Speaker 1: for Planet 9 represents one of the most challenging treasure
• 1:17:06
  Speaker 1: hunts in scientific history. Astronomers are essentially looking for a
• 1:17:11
  Speaker 1: needle in a cosmic haystack, scanning millions of square degrees
• 1:17:15
  Speaker 1: of sky for an object that might move less than
• 1:17:18
  Speaker 1: the width of a human hair, as seen from a
• 1:17:21
  Speaker 1: mile away over the course of an entire year. But
• 1:17:25
  Speaker 1: the potential discovery of Planet 9 would revolutionise our understanding
• 1:17:29
  Speaker 1: of our solar system's size and structure. It would push
• 1:17:32
  Speaker 1: our cosmic neighbourhood's confirmed boundaries out to distances that begin
• 1:17:36
  Speaker 1: to approach interstellar scales. We'd be dealing with a planetary
• 1:17:41
  Speaker 1: system that spans roughly 1% of the distance to the
• 1:17:45
  Speaker 1: nearest star, a realm so vast that radio signals would
• 1:17:49
  Speaker 1: take over five hours to travel from the Sun to
• 1:17:53
  Speaker 1: this distant world. Communication with any spacecraft we might eventually
• 1:17:59
  Speaker 1: send to Planet 9 would require the patience of geological time.
• 1:18:04
  Speaker 1: A simple message from Earth would take hours to arrive,
• 1:18:08
  Speaker 1: and the response would take hours to return. You could
• 1:18:12
  Speaker 1: ask a question in the morning and receive an answer
• 1:18:15
  Speaker 1: after dinner, assuming anyone was still around to hear it.
• 1:18:19
  Speaker 1: But even Planet 9, if it exists, might not represent
• 1:18:22
  Speaker 1: the true edge of our solar system's gravitational influence. Recent
• 1:18:26
  Speaker 1: computer simulations suggest that objects as far out as 150,000
• 1:18:31
  Speaker 1: astronomical units might still be gravitationally bound to our sun.
• 1:18:36
  Speaker 1: That's roughly two and a half light years away, more
• 1:18:39
  Speaker 1: than halfway to the nearest star. At these distances, we're
• 1:18:43
  Speaker 1: dealing with a realm where the very concept of belonging
• 1:18:46
  Speaker 1: to our solar system becomes almost philosophical. Objects this far
• 1:18:51
  Speaker 1: out would take millions of years to orbit the sun once.
• 1:18:55
  Speaker 1: They would be more influenced by passing stars and galactic
• 1:18:58
  Speaker 1: tides than by our own star. Yet mathematically, they would
• 1:19:03
  Speaker 1: still be part of our cosmic family, however tenuous that
• 1:19:07
  Speaker 1: relationship might be. This extreme outer boundary reveals something profound
• 1:19:12
  Speaker 1: about the nature of gravitational influence in the universe. Gravity
• 1:19:18
  Speaker 1: never truly reaches zero, no matter how far you travel
• 1:19:22
  Speaker 1: from a massive object. It just gets weaker and weaker,
• 1:19:26
  Speaker 1: following what mathematicians call an inverse square law. Double the
• 1:19:31
  Speaker 1: distance and the gravitational pull becomes four times weaker. Triple
• 1:19:36
  Speaker 1: the distance and it becomes nine times weaker. But weaker
• 1:19:41
  Speaker 1: doesn't mean gone. Even at the incredible distance of 150,000
• 1:19:46
  Speaker 1: astronomical units, our sun's gravity would still be detectable, still
• 1:19:51
  Speaker 1: capable of holding objects in orbit, still defining the boundary
• 1:19:56
  Speaker 1: between what belongs to us and what belongs to the
• 1:19:59
  Speaker 1: galaxy at large. This fading influence creates what astronomers call
• 1:20:04
  Speaker 1: the Hill Sphere. the region around any massive object where
• 1:20:08
  Speaker 1: its gravity dominates over all other gravitational influences. For our Sun,
• 1:20:15
  Speaker 1: this Hill Sphere extends roughly two light years in all directions,
• 1:20:20
  Speaker 1: creating a sphere of gravitational dominance that's actually larger than
• 1:20:24
  Speaker 1: the distance to our nearest stellar neighbours. The implications are staggering.
• 1:20:32
  Speaker 1: Our Solar System's gravitational territory actually overlaps with the territories
• 1:20:37
  Speaker 1: of nearby star systems. There might be objects in space
• 1:20:41
  Speaker 1: that feel gravitational tugs from multiple stars simultaneously, cosmic orphans
• 1:20:47
  Speaker 1: that aren't quite sure which stellar family they belong to.
• 1:20:51
  Speaker 1: This overlap zone between stellar gravitational territories represents one of
• 1:20:56
  Speaker 1: the most mysterious regions in our local galactic neighbourhood. It's
• 1:21:00
  Speaker 1: a realm where the normal rules of planetary dynamics break down,
• 1:21:05
  Speaker 1: where objects might be captured by one star system, then
• 1:21:08
  Speaker 1: stolen away by another as stellar positions shift over millions
• 1:21:13
  Speaker 1: of years. Some scientists speculate that this disputed territory might
• 1:21:18
  Speaker 1: be populated by rogue planets, worlds that were ejected from
• 1:21:23
  Speaker 1: their birth star systems during chaotic formation processes. These cosmic
• 1:21:29
  Speaker 1: wanderers would drift through interstellar space, occasionally being captured by
• 1:21:34
  Speaker 1: passing stars or settling into long-term orbits in the gravitational
• 1:21:39
  Speaker 1: borderlands between stellar systems. If such rogue planets exist in
• 1:21:44
  Speaker 1: the outer reaches of our solar system, they would represent
• 1:21:48
  Speaker 1: the ultimate expression of cosmic scale. These would be worlds
• 1:21:54
  Speaker 1: that have travelled interstellar distances, carrying with them the chemical
• 1:21:58
  Speaker 1: signatures and formation history of alien star systems. Studying them
• 1:22:04
  Speaker 1: would be like examining cosmic fossils from distant regions of
• 1:22:09
  Speaker 1: our galaxy. But the search for such exotic objects pushes
• 1:22:14
  Speaker 1: our observational capabilities to their absolute limits. These hypothetical rogue
• 1:22:20
  Speaker 1: planets would be virtually invisible, emitting no light of their
• 1:22:25
  Speaker 1: own and reflecting almost no sunlight due to their enormous distances.
• 1:22:30
  Speaker 1: Detecting them would require next generation telescopes and survey techniques
• 1:22:35
  Speaker 1: that don't yet exist. Yet the search continues, driven by
• 1:22:40
  Speaker 1: the tantalizing possibility that our solar system might be far
• 1:22:43
  Speaker 1: stranger and more complex than we currently imagine. Each new
• 1:22:48
  Speaker 1: discovery in the outer darkness reveals that our cosmic neighborhood
• 1:22:52
  Speaker 1: contains secrets we're only beginning to uncover. The Kuiper Belt.
• 1:22:57
  Speaker 1: once thought to be a relatively simple disk of icy debris,
• 1:23:01
  Speaker 1: has turned out to be a complex region with distinct
• 1:23:04
  Speaker 1: populations of objects following different types of orbits. Some Kuiper
• 1:23:10
  Speaker 1: belt objects are nearly circular in their paths around the Sun,
• 1:23:15
  Speaker 1: while others follow highly elongated trajectories that carry them far
• 1:23:20
  Speaker 1: beyond Pluto before swinging back toward the inner solar system.
• 1:23:24
  Speaker 1: This diversity suggests a violent and chaotic past, a time
• 1:23:29
  Speaker 1: when gravitational interactions between the giant planets scattered objects throughout
• 1:23:34
  Speaker 1: the outer solar system like cosmic billiard balls. Computer simulations
• 1:23:40
  Speaker 1: of these early dynamics reveal a solar system in constant upheaval,
• 1:23:46
  Speaker 1: with planets migrating inward and outward, asteroid belts being disrupted
• 1:23:51
  Speaker 1: and reformed, and countless small bodies being flung into interstellar
• 1:23:56
  Speaker 1: space or crashed into planetary surfaces. The scars of this
• 1:24:00
  Speaker 1: chaotic period are still visible throughout our solar system. The
• 1:24:04
  Speaker 1: heavily cratered surfaces of the Moon and Mercury record the
• 1:24:09
  Speaker 1: tail end of this cosmic bombardment. The unusual tilts and
• 1:24:13
  Speaker 1: spins of Uranus and Venus hint at massive collisions that
• 1:24:17
  Speaker 1: knocked these worlds off their original axes. Even the asteroid
• 1:24:22
  Speaker 1: belt between Mars and Jupiter represents the shattered remains of
• 1:24:27
  Speaker 1: planetary building materials that never quite managed to coalesce into
• 1:24:31
  Speaker 1: a proper world. But perhaps the most dramatic evidence of
• 1:24:36
  Speaker 1: our solar system's violent past lies in the late heavy bombardment,
• 1:24:42
  Speaker 1: a period roughly 4 billion years ago when the inner
• 1:24:46
  Speaker 1: planets were pelted by an intense shower of asteroids and comets.
• 1:24:51
  Speaker 1: This cosmic storm may have been triggered by the migration
• 1:24:55
  Speaker 1: of Jupiter and Saturn to their current orbits, a gravitational
• 1:25:00
  Speaker 1: reshuffling that sent waves of debris cascading throughout the solar system.
• 1:25:06
  Speaker 1: The timing of this bombardment coincides remarkably with the earliest
• 1:25:10
  Speaker 1: evidence of life on Earth. suggesting that the same cosmic
• 1:25:14
  Speaker 1: violence that scarred planetary surfaces might have also delivered the
• 1:25:19
  Speaker 1: water and organic compounds necessary for biology to take hold.
• 1:25:24
  Speaker 1: In a very real sense, the enormous scale and dynamic
• 1:25:29
  Speaker 1: history of our solar system may have been essential for
• 1:25:32
  Speaker 1: creating the conditions that allowed life to emerge on our
• 1:25:35
  Speaker 1: small blue world. This connection between cosmic scale and biological
• 1:25:41
  Speaker 1: possibility extends far beyond Earth. Several moons in the outer
• 1:25:46
  Speaker 1: solar system, particularly Europa, Enceladus and Titan, show evidence of
• 1:25:52
  Speaker 1: subsurface oceans that might harbour life. These hidden seas exist
• 1:25:57
  Speaker 1: because of tidal heating, a process where gravitational interactions with
• 1:26:01
  Speaker 1: massive planets generate enough internal friction to keep water liquid,
• 1:26:07
  Speaker 1: despite surface temperatures that would freeze carbon dioxide solid. The
• 1:26:14
  Speaker 1: fact that these potentially habitable environments exist in the outer
• 1:26:18
  Speaker 1: reaches of our solar system, billions of miles from the
• 1:26:22
  Speaker 1: sun's warmth, reveals how the sheer size and gravitational complexity
• 1:26:28
  Speaker 1: of our cosmic neighbourhood creates opportunities for life in places
• 1:26:33
  Speaker 1: we never expected. The scale that once seemed like an
• 1:26:37
  Speaker 1: obstacle to habitability might actually be one of its greatest enablers.
• 1:26:42
  Speaker 1: But even these remarkable discoveries pale in comparison to the
• 1:26:47
  Speaker 1: most profound implication of our solar system's true size. The
• 1:26:52
  Speaker 1: distances we've been exploring represent just the beginning of an
• 1:26:56
  Speaker 1: even grander cosmic perspective. Our entire solar system, vast as
• 1:27:02
  Speaker 1: it appears from our Earth-bound viewpoint, occupies only the tiniest
• 1:27:07
  Speaker 1: fraction of our galaxy's volume. The Milky Way contains somewhere
• 1:27:12
  Speaker 1: between 200 and 400 billion stars, most of them likely
• 1:27:17
  Speaker 1: surrounded by their own planetary systems. If every star system
• 1:27:23
  Speaker 1: were roughly the same size as ours, and if they
• 1:27:26
  Speaker 1: were packed as efficiently as possible, with no empty space
• 1:27:29
  Speaker 1: between them, our entire galaxy would still be more than
• 1:27:33
  Speaker 1: 99% empty space. But star systems aren't packed efficiently at all.
• 1:27:40
  Speaker 1: They're separated by vast gulfs of interstellar vacuum that dwarf
• 1:27:44
  Speaker 1: even the enormous distances within individual solar systems. The space
• 1:27:50
  Speaker 1: between our sun and the nearest star contains virtually nothing
• 1:27:55
  Speaker 1: except incredibly thin wisps of interstellar gas and dust, magnetic
• 1:28:00
  Speaker 1: fields so weak they barely register on our most sensitive instruments,
• 1:28:05
  Speaker 1: and the occasional lonely rogue planet drifting through the cosmic void.
• 1:28:09
  Speaker 1: This interstellar emptiness extends in all directions for distances that
• 1:28:15
  Speaker 1: make our solar system's dimensions seem almost cosy by comparison.
• 1:28:20
  Speaker 1: If you could somehow would take you over four years'
• 1:28:22
  Speaker 1: travel at the speed of light, it just to reach
• 1:28:25
  Speaker 1: the nearest star system, to cross our entire galaxy, would
• 1:28:29
  Speaker 1: require 100,000 years of travel at the universe's ultimate speed limit.
• 1:28:35
  Speaker 1: Yet even our galaxy represents just one island of matter.
• 1:28:39
  Speaker 1: in an ocean of cosmic emptiness that extends far beyond
• 1:28:43
  Speaker 1: anything we've discussed so far. The nearest major galaxy to ours, Andromeda,
• 1:28:49
  Speaker 1: sits over two million light-years away. Between our galaxy and
• 1:28:54
  Speaker 1: Andromeda lies a void so vast and empty it contains
• 1:28:58
  Speaker 1: perhaps a few dozen small satellite galaxies scattered across distances
• 1:29:03
  Speaker 1: that would take light millions of years to traverse. This
• 1:29:07
  Speaker 1: cosmic perspective transforms our understanding of what it means to
• 1:29:11
  Speaker 1: ask how big our solar system really is. The question
• 1:29:16
  Speaker 1: isn't just about measuring distances within our local stellar neighbourhood,
• 1:29:20
  Speaker 1: it's about understanding our place in a hierarchy of cosmic
• 1:29:24
  Speaker 1: structures that extends from planetary orbits galactic clusters to the
• 1:29:29
  Speaker 1: largest known structures in the observable universe. At each level
• 1:29:34
  Speaker 1: of this cosmic hierarchy, the scales involved become more difficult
• 1:29:38
  Speaker 1: to comprehend. Planetary systems span light hours to light years.
• 1:29:44
  Speaker 1: Galaxies span tens of thousands of light years. Galaxy clusters
• 1:29:49
  Speaker 1: span millions of light years. The largest cosmic structures, Great
• 1:29:54
  Speaker 1: walls of galaxies separated by enormous voids can extend across
• 1:29:59
  Speaker 1: hundreds of millions of light years. Our solar system, impressive
• 1:30:04
  Speaker 1: as its dimensions may seem, represents just the first tiny
• 1:30:08
  Speaker 1: step up this ladder of cosmic scale. We are inhabitants
• 1:30:13
  Speaker 1: of what amounts to a single room in a house
• 1:30:16
  Speaker 1: that sits on a street in a neighborhood that's part
• 1:30:19
  Speaker 1: of a city that exists within a county that belongs
• 1:30:23
  Speaker 1: to a state, in a country, on a continent, of
• 1:30:26
  Speaker 1: a planet, in a solar system that's one of billions
• 1:30:30
  Speaker 1: in a galaxy, that's one of trillions in an observable universe,
• 1:30:34
  Speaker 1: that might itself be just a tiny fraction of a
• 1:30:38
  Speaker 1: larger multiverse whose true extent we can't even begin to imagine.
• 1:30:43
  Speaker 1: This progression of scales reveals something profound about the nature
• 1:30:47
  Speaker 1: of size and distance in our universe. At each level,
• 1:30:51
  Speaker 1: the structures that seemed impossibly large at the previous level
• 1:30:55
  Speaker 1: become almost negligibly small. Our solar system, which spans light
• 1:31:00
  Speaker 1: years and contains trillions of objects, becomes a barely detectable
• 1:31:05
  Speaker 1: speck when viewed from the perspective of our galaxy. Our galaxy,
• 1:31:10
  Speaker 1: containing hundreds of billions of stars, becomes invisible when viewed
• 1:31:15
  Speaker 1: from the distance of far galactic clusters. Yet paradoxically, this
• 1:31:20
  Speaker 1: cosmic perspective also highlights just how extraordinary our local neighbourhood
• 1:31:25
  Speaker 1: really is. In all the vast emptiness of intergalactic space,
• 1:31:30
  Speaker 1: across distances so large they challenge the very meaning of
• 1:31:33
  Speaker 1: the word distance, complex structures like our solar system are
• 1:31:37
  Speaker 1: incredibly rare and precious oases of organised matter and energy.
• 1:31:42
  Speaker 1: The fact that gravity can create and maintain such intricate
• 1:31:46
  Speaker 1: cosmic architectures across such enormous scales is itself a kind
• 1:31:51
  Speaker 1: of miracle. The delicate gravitational ballet that keeps planets in
• 1:31:57
  Speaker 1: stable orbits, that maintains the structure of asteroid belts and
• 1:32:02
  Speaker 1: comet clouds, that allows moons to orbit planets while planets
• 1:32:07
  Speaker 1: orbit stars, while star systems orbit galactic centres, requires a
• 1:32:14
  Speaker 1: kind of cosmic fine-tuning seems almost impossibly precise, change the
• 1:32:19
  Speaker 1: strength of gravity by even a small amount, and stable
• 1:32:23
  Speaker 1: planetary orbits become impossible. Make space expand faster, and galaxies
• 1:32:30
  Speaker 1: never form in the first place. Alter the properties of
• 1:32:34
  Speaker 1: matter in subtle ways, and stars can't ignite or planets
• 1:32:38
  Speaker 1: can't solidify. The universe we observe with its hierarchy of
• 1:32:43
  Speaker 1: structures extending from subatomic particles to galactic superclusters, exists within
• 1:32:48
  Speaker 1: an incredibly narrow range of physical parameters that allow complexity
• 1:32:53
  Speaker 1: and structure to emerge from primordial chaos. Our solar system
• 1:32:58
  Speaker 1: represents one successful solution to the challenge of creating stable,
• 1:33:03
  Speaker 1: long-lived structures in a universe governed by the competing forces
• 1:33:06
  Speaker 1: of gravity and expansion, attraction and motion, order and entropy.
• 1:33:13
  Speaker 1: The fact that this solution has persisted for over four
• 1:33:17
  Speaker 1: and a half billion years, allowing time for planets to cool,
• 1:33:22
  Speaker 1: atmospheres to develop, and life to emerge and evolve, makes
• 1:33:27
  Speaker 1: our cosmic neighbourhood not just large, but also incredibly precious.
• 1:33:32
  Speaker 1: Every measurement of distance within our solar system, every calculation
• 1:33:37
  Speaker 1: of orbital periods and gravitational influences, Every discovery of new
• 1:33:43
  Speaker 1: objects in the outer darkness adds another piece to our
• 1:33:46
  Speaker 1: understanding of how this remarkable system manages to maintain its
• 1:33:51
  Speaker 1: stability and complexity across such vast scales of space and time.
• 1:33:57
  Speaker 1: The question of how big our solar system really is
• 1:34:01
  Speaker 1: thus becomes not just a matter of astronomical measurement, but
• 1:34:05
  Speaker 1: a window into the fundamental nature of cosmic organisation itself.
• 1:34:11
  Speaker 1: We're not just measuring empty space between isolated objects. We're
• 1:34:15
  Speaker 1: mapping the architecture of gravitational relationships that bind our cosmic
• 1:34:20
  Speaker 1: neighborhood together and allow it to function as an integrated
• 1:34:23
  Speaker 1: system despite the enormous distances involved. This architectural perspective reveals
• 1:34:29
  Speaker 1: that size alone doesn't capture the full significance of our
• 1:34:33
  Speaker 1: solar system's dimensions. What matters isn't just how far objects
• 1:34:39
  Speaker 1: are from each other, but how these distances enable the
• 1:34:42
  Speaker 1: complex interactions that make our cosmic neighbourhood a living dynamic
• 1:34:48
  Speaker 1: system rather than just a collection of isolated worlds drifting
• 1:34:53
  Speaker 1: through empty space. The enormous distances between planets allow them
• 1:34:59
  Speaker 1: to maintain stable, independent orbits without interfering destructively with each other.
• 1:35:07
  Speaker 1: The vast extent of the Oort cloud provides a reservoir
• 1:35:11
  Speaker 1: of cometary materials that occasionally refresh the inner solar system
• 1:35:16
  Speaker 1: with water and organic compounds. The subtle gravitational influences that
• 1:35:22
  Speaker 1: operate across billions of miles help maintain long-term stability while
• 1:35:27
  Speaker 1: allowing for gradual evolutionary changes that prevent the system from
• 1:35:31
  Speaker 1: becoming completely static and lifeless. In this sense, our solar
• 1:35:36
  Speaker 1: system's enormous size isn't just an interesting astronomical fact. It's
• 1:35:42
  Speaker 1: an essential feature that makes possible everything from stable climates
• 1:35:47
  Speaker 1: to the gradual delivery of life-supporting materials to the long-term
• 1:35:52
  Speaker 1: habitability of worlds like Earth. The scale that initially seems
• 1:35:57
  Speaker 1: to separate and isolate objects actually enables the connections and
• 1:36:02
  Speaker 1: interactions that make our cosmic neighbourhood a unified functioning system.
• 1:36:07
  Speaker 1: Understanding this interconnected nature of our solar system's vast architecture
• 1:36:13
  Speaker 1: leads us to perhaps the most mind-bending realisation yet. When
• 1:36:19
  Speaker 1: we think about communication and travel across these cosmic distances,
• 1:36:23
  Speaker 1: we're not just dealing with practical challenges. We're confronting fundamental
• 1:36:28
  Speaker 1: limitations imposed by the very structure of spacetime itself. Consider
• 1:36:34
  Speaker 1: what it would mean to have a conversation with someone
• 1:36:37
  Speaker 1: living on Neptune. Even travelling at the speed of light,
• 1:36:41
  Speaker 1: the absolute fastest anything can move in our universe. Your
• 1:36:45
  Speaker 1: words would take over four hours to reach them. Their
• 1:36:49
  Speaker 1: response would take another four hours to return to you.
• 1:36:52
  Speaker 1: What we think of as a simple back-and-forth exchange would
• 1:36:56
  Speaker 1: stretch across an entire day, assuming both parties responded immediately
• 1:37:01
  Speaker 1: upon receiving each message. but this communication delay is nothing
• 1:37:06
  Speaker 1: compared to what we'd face trying to talk to inhabitants
• 1:37:09
  Speaker 1: of the outer Oort cloud. A radio message sent to
• 1:37:13
  Speaker 1: the edge of our solar system would take over two
• 1:37:16
  Speaker 1: years to arrive at its destination. The return message would
• 1:37:21
  Speaker 1: take another two years to come back. You could ask
• 1:37:24
  Speaker 1: someone a question when you're 20 years old and not
• 1:37:27
  Speaker 1: receive their answer until you're 24. entire relationships, careers and
• 1:37:34
  Speaker 1: life chapters could unfold in the time it takes for
• 1:37:37
  Speaker 1: a single exchange of ideas across our solar system's true diameter.
• 1:37:42
  Speaker 1: This temporal stretching of communication reveals something profound about the
• 1:37:47
  Speaker 1: nature of existence in a cosmic system this large. Different
• 1:37:53
  Speaker 1: regions of our solar system don't just exist at different
• 1:37:57
  Speaker 1: distances from each other. They exist in different temporal relationships
• 1:38:01
  Speaker 1: with the rest of the system. The outer Oort cloud
• 1:38:05
  Speaker 1: lives in a fundamentally different kind of present than we
• 1:38:08
  Speaker 1: do here on Earth. When we observe Jupiter through a telescope,
• 1:38:12
  Speaker 1: we're seeing it as it was 43 minutes ago. When
• 1:38:16
  Speaker 1: we look at the most distant confirmed objects in our
• 1:38:19
  Speaker 1: solar system, we're seeing them as they were hours or
• 1:38:23
  Speaker 1: even days ago. In a very real sense, our solar
• 1:38:27
  Speaker 1: system doesn't have a unified present moment. Instead, it exists
• 1:38:32
  Speaker 1: as a collection of overlapping temporal zones, each experiencing its
• 1:38:37
  Speaker 1: own slightly different version of now. This temporal complexity becomes
• 1:38:42
  Speaker 1: even more fascinating when you consider how it affects the
• 1:38:46
  Speaker 1: very concept of simultaneous events. If something dramatic happened to
• 1:38:51
  Speaker 1: the Sun right now, Earth wouldn't know about it for
• 1:38:55
  Speaker 1: eight minutes. Mars might not find out for 24 minutes.
• 1:39:01
  Speaker 1: Jupiter would remain unaware for nearly three quarters of an hour.
• 1:39:06
  Speaker 1: The outer planets could continue their normal existence for several
• 1:39:09
  Speaker 1: hours before the effects reached them. In that sense, our
• 1:39:14
  Speaker 1: solar system doesn't just span incredible distances in space. spans
• 1:39:19
  Speaker 1: incredible distances in time as well. The same event propagates
• 1:39:24
  Speaker 1: outward through our cosmic neighbourhood like ripples on a vast pond,
• 1:39:28
  Speaker 1: reaching different locations at different moments, creating a cascade of
• 1:39:33
  Speaker 1: cause and effect that can stretch across days or even weeks.
• 1:39:38
  Speaker 1: But the temporal challenges of our solar system's scale pale
• 1:39:41
  Speaker 1: in comparison to the navigational complexity of actually travelling between
• 1:39:46
  Speaker 1: these distant worlds. When mission planners calculate trajectories for spacecraft,
• 1:39:52
  Speaker 1: they're not just plotting routes through three-dimensional space. They're choreographing
• 1:39:58
  Speaker 1: journeys through four-dimensional space-time, timing launches and course corrections to
• 1:40:06
  Speaker 1: intercept moving targets across billions of miles of constantly shifting
• 1:40:11
  Speaker 1: cosmic terrain. Consider the challenge of sending a spacecraft to
• 1:40:15
  Speaker 1: Jupiter You can't simply aim at where Jupiter appears to
• 1:40:19
  Speaker 1: be in the sky and fire your rockets. By the
• 1:40:22
  Speaker 1: time your spacecraft crosses the vast distance between Earth and
• 1:40:25
  Speaker 1: Jupiter's orbital path, Jupiter will have moved hundreds of millions
• 1:40:29
  Speaker 1: of miles from its starting position. Instead, you have to
• 1:40:34
  Speaker 1: aim at where Jupiter will be when your spacecraft finally arrives,
• 1:40:38
  Speaker 1: calculating the intersection of two moving objects across distances so
• 1:40:42
  Speaker 1: large that tiny errors in initial trajectory can result in
• 1:40:46
  Speaker 1: missing your target by millions of miles. This problem becomes
• 1:40:50
  Speaker 1: exponentially more complex as you venture into the outer solar system.
• 1:40:54
  Speaker 1: A mission to Neptune requires predicting where that distant world
• 1:40:59
  Speaker 1: will be, not in months, but in years or even decades.
• 1:41:04
  Speaker 1: The spacecraft must be launched on a trajectory that accounts
• 1:41:07
  Speaker 1: for the gravitational influences of multiple planets. the subtle effects
• 1:41:12
  Speaker 1: of solar wind pressure, and even the tiny but measurable
• 1:41:16
  Speaker 1: impact of Einstein's relativistic corrections to classical orbital mechanics. The
• 1:41:23
  Speaker 1: mathematical precision required for these calculations pushes human knowledge to
• 1:41:27
  Speaker 1: its very limits. Mission planners must account for gravitational influences
• 1:41:32
  Speaker 1: so subtle that they wouldn't be noticeable over distances of
• 1:41:36
  Speaker 1: mere millions of miles. but become crucial when accumulated over
• 1:41:40
  Speaker 1: billions of miles and years of travel time. They must
• 1:41:44
  Speaker 1: predict the future positions of planets with an accuracy that
• 1:41:47
  Speaker 1: would be impressive, even if those planets were sitting still,
• 1:41:52
  Speaker 1: much less while they're racing through space at tens of
• 1:41:55
  Speaker 1: thousands of miles per hour. Yet somehow we've managed to
• 1:41:58
  Speaker 1: master this cosmic choreography well enough to send robotic explorers
• 1:42:02
  Speaker 1: to every major planet in our solar system. We've landed
• 1:42:06
  Speaker 1: on Mars, orbited Jupiter, flown through Saturn's rings and sent
• 1:42:12
  Speaker 1: spacecraft beyond the edge of the heliosphere into interstellar space.
• 1:42:18
  Speaker 1: Each of these achievements represents a triumph of human mathematics
• 1:42:22
  Speaker 1: and engineering over the seemingly impossible challenges posed by our
• 1:42:27
  Speaker 1: solar system's enormous scale. The Voyager missions provide perhaps the
• 1:42:33
  Speaker 1: most stunning example of this navigational mastery. Launched in the
• 1:42:38
  Speaker 1: late 1970s, these spacecraft were designed to take advantage of
• 1:42:43
  Speaker 1: a rare alignment of the outer planets that occurs only
• 1:42:46
  Speaker 1: once every 175 years. By carefully timing their trajectories, mission
• 1:42:52
  Speaker 1: planners were able to use gravitational assists from Jupiter and
• 1:42:56
  Speaker 1: Saturn to fling these robotic explorers toward Uranus and Neptune,
• 1:43:02
  Speaker 1: and eventually into interstellar space itself. The precision required for
• 1:43:07
  Speaker 1: these gravitational slingshots is almost incomprehensible. The spacecraft had to
• 1:43:13
  Speaker 1: arrive at exactly the right location relative to each planet
• 1:43:17
  Speaker 1: at exactly the right moment to receive the proper gravitational
• 1:43:21
  Speaker 1: kick toward their next destination, miss the target by even
• 1:43:26
  Speaker 1: a few hundred miles or a few minutes, and the
• 1:43:29
  Speaker 1: entire mission trajectory would be ruined. Yet both Voyager spacecraft
• 1:43:36
  Speaker 1: executed these cosmic billiard shots flawlessly, using the gravitational fields
• 1:43:42
  Speaker 1: of giant planets as stepping stones across the outer solar system.
• 1:43:46
  Speaker 1: They transformed what should have been impossible journeys, requiring decades
• 1:43:50
  Speaker 1: of continuous rocket thrust into elegant gravitational dances that carried
• 1:43:55
  Speaker 1: them to the edge of our solar system and beyond,
• 1:43:58
  Speaker 1: using only the initial push provided by their launch rockets.
• 1:44:02
  Speaker 1: The success of missions like Voyager reveals something remarkable about
• 1:44:06
  Speaker 1: the hidden order underlying our solar system's apparent chaos. Despite
• 1:44:11
  Speaker 1: the enormous distances, complex orbital mechanics, and multiple gravitational influences
• 1:44:18
  Speaker 1: at play, our cosmic neighbourhood operates according to mathematical principles
• 1:44:23
  Speaker 1: precise enough to allow for incredibly accurate long-term predictions. The
• 1:44:30
  Speaker 1: same laws of physics that govern the motion of a
• 1:44:33
  Speaker 1: thrown ball here on Earth also determine the paths of
• 1:44:36
  Speaker 1: spacecraft across billions of miles of interplanetary space. This mathematical
• 1:44:42
  Speaker 1: predictability becomes even more impressive when you consider the time
• 1:44:46
  Speaker 1: scales involved. The orbital mechanics calculations that guided Voyager's trajectory
• 1:44:52
  Speaker 1: were based on observations and theories developed over centuries of
• 1:44:56
  Speaker 1: astronomical research. Scientists in the 1700s and 1800s, working with
• 1:45:02
  Speaker 1: nothing more than telescopes and pencil and paper calculations, laid
• 1:45:07
  Speaker 1: the mathematical groundwork that made these 21st century space missions possible.
• 1:45:13
  Speaker 1: Isaac Newton's law of universal gravitation, formulated in the 1600s,
• 1:45:19
  Speaker 1: provides the fundamental framework we still use to navigate spacecraft
• 1:45:24
  Speaker 1: across the solar system. Johannes Kepler's laws of planetary motion,
• 1:45:30
  Speaker 1: derived from careful observations in the early 1600s, continue to
• 1:45:35
  Speaker 1: describe the elliptical orbits followed by both natural bodies and
• 1:45:39
  Speaker 1: artificial spacecraft. The mathematical tools developed by these scientific pioneers
• 1:45:46
  Speaker 1: centuries ago remain adequate for the most sophisticated space missions
• 1:45:50
  Speaker 1: we can currently imagine. This continuity between historical astronomy and
• 1:45:55
  Speaker 1: modern space exploration reveals something profound about the nature of
• 1:46:00
  Speaker 1: scientific knowledge and the structure of our universe. The same
• 1:46:05
  Speaker 1: mathematical relationships that ancient astronomers discerned by carefully tracking the
• 1:46:10
  Speaker 1: positions of wandering stars continue to govern the motion of
• 1:46:15
  Speaker 1: high-tech robotic explorers racing through the outer darkness of our
• 1:46:20
  Speaker 1: solar system. our growing mastery of solar system navigation has
• 1:46:26
  Speaker 1: also revealed just how much we still don't know about
• 1:46:30
  Speaker 1: our cosmic neighbourhood's true extent and complexity. Each successful mission
• 1:46:35
  Speaker 1: to the outer planets has discovered phenomena that previous theories
• 1:46:39
  Speaker 1: couldn't predict, from the active volcanism on Jupiter's moon Io
• 1:46:44
  Speaker 1: to the methane lakes on Saturn's moon Titan. the geysers
• 1:46:48
  Speaker 1: of water ice erupting from the south pole of Saturn's
• 1:46:52
  Speaker 1: moon Enceladus. These discoveries remind us that our solar system
• 1:46:57
  Speaker 1: isn't just large, it's also incredibly diverse, containing environments and
• 1:47:04
  Speaker 1: processes that challenge our understanding of planetary science. The same
• 1:47:09
  Speaker 1: gravitational forces that create the elegant orbital mechanics we've learned
• 1:47:14
  Speaker 1: to navigate, also drive complex geological processes on worlds billions
• 1:47:20
  Speaker 1: of miles from the Sun. Tidal heating from gravitational interactions
• 1:47:26
  Speaker 1: can keep subsurface oceans liquid on moons so distant that
• 1:47:31
  Speaker 1: sunlight provides virtually no warmth. Atmospheric dynamics can create weather
• 1:47:37
  Speaker 1: patterns that persist for centuries on planets. where seasons last
• 1:47:41
  Speaker 1: for decades. This diversity exists because of, not despite, our
• 1:47:47
  Speaker 1: solar system's enormous scale. The vast distances between objects allow
• 1:47:53
  Speaker 1: each world to develop its own unique characteristics without interference
• 1:47:57
  Speaker 1: from its neighbours. Unlike Earth, where global circulation patterns eventually
• 1:48:02
  Speaker 1: mix and homogenise atmospheric and oceanic conditions, The worlds of
• 1:48:08
  Speaker 1: our outer solar system exist in splendid isolation, free to
• 1:48:13
  Speaker 1: evolve their own distinctive environments over billions of years. Mars
• 1:48:18
  Speaker 1: develops a thin carbon dioxide atmosphere and experiences dust storms
• 1:48:23
  Speaker 1: that can engulf the entire planet for months. Venus creates
• 1:48:29
  Speaker 1: a crushing greenhouse effect that melts lead and produces sulfuric
• 1:48:33
  Speaker 1: acid rain. Jupiter maintains a storm system larger than our
• 1:48:38
  Speaker 1: entire planet that has been raging continuously for centuries. Each
• 1:48:42
  Speaker 1: of these environments represents a different solution to the challenge
• 1:48:47
  Speaker 1: of planetary evolution, made possible by the cosmic isolation that
• 1:48:51
  Speaker 1: our solar system's enormous distances provide. But perhaps the most
• 1:48:56
  Speaker 1: remarkable aspect of this diversity is how it extends even
• 1:49:00
  Speaker 1: to objects we once thought were simple and uniform. The
• 1:49:06
  Speaker 1: asteroid belt, for instance, was originally conceived as a relatively
• 1:49:10
  Speaker 1: homogeneous collection of rocky debris left over from planetary formation.
• 1:49:17
  Speaker 1: Detailed study has revealed it to be an incredibly complex
• 1:49:20
  Speaker 1: region containing objects with wildly different compositions, structures and histories.
• 1:49:27
  Speaker 1: Some asteroids are solid chunks of metal and rock, remnants
• 1:49:31
  Speaker 1: of the cores of shattered planetesimals, Others are loose collections
• 1:49:35
  Speaker 1: of rubble held together by their own weak gravity, so
• 1:49:39
  Speaker 1: fragile that a strong push could scatter them like cosmic dust.
• 1:49:44
  Speaker 1: Still others appear to be extinct comets, their volatile materials
• 1:49:49
  Speaker 1: long since boiled away by repeated passages near the Sun,
• 1:49:53
  Speaker 1: leaving behind only dark, carbonaceous skeletons. The asteroid Ceres, the
• 1:49:59
  Speaker 1: largest object in the asteroid belt, has turned out to
• 1:50:02
  Speaker 1: be complex enough to qualify as a dwarf planet in
• 1:50:04
  Speaker 1: its own right. Recent spacecraft missions have revealed that Ceres
• 1:50:10
  Speaker 1: has a differentiated interior with a possible subsurface ocean, making
• 1:50:15
  Speaker 1: it yet another potentially habitable world in the outer reaches
• 1:50:19
  Speaker 1: of our solar system. What we once dismissed as cosmic
• 1:50:23
  Speaker 1: rubble has proven to contain environments that might rival those
• 1:50:27
  Speaker 1: of the moons of Jupiter and Saturn, in their potential
• 1:50:31
  Speaker 1: for harboring life. This pattern of increasing complexity with increasing
• 1:50:35
  Speaker 1: exploration extends throughout our solar system. The more closely we
• 1:50:40
  Speaker 1: examine any region of our cosmic neighborhood, the more intricate
• 1:50:44
  Speaker 1: and fascinating it becomes. The Kuiper Belt has revealed itself
• 1:50:49
  Speaker 1: to be populated by objects following bizarrely complex orbital patterns
• 1:50:54
  Speaker 1: that hint at gravitational influences we don't yet understand. the
• 1:50:58
  Speaker 1: scattered disk beyond Neptune contains worlds like Eris that challenge
• 1:51:02
  Speaker 1: our very definitions of what constitutes a planet. Even the
• 1:51:08
  Speaker 1: space between planets, once thought to be essentially empty, has
• 1:51:13
  Speaker 1: proven to be filled with dust, charged particles, and magnetic
• 1:51:18
  Speaker 1: field structures that create invisible highways and barriers throughout our
• 1:51:23
  Speaker 1: solar system. Each of these discoveries adds another layer of
• 1:51:27
  Speaker 1: complexity to our understanding of what it means to measure
• 1:51:31
  Speaker 1: our solar system's true size. We're not just dealing with
• 1:51:36
  Speaker 1: simple distances between isolated objects floating in empty space. We're
• 1:51:42
  Speaker 1: mapping the architecture of an incredibly intricate system where every
• 1:51:47
  Speaker 1: component influences every other component across vast distances through mechanisms
• 1:51:53
  Speaker 1: we're only beginning to understand. The magnetic field generated by
• 1:51:57
  Speaker 1: Jupiter's rapid rotation, for instance, creates a magnetosphere so large
• 1:52:02
  Speaker 1: that it would be visible to the naked eye from
• 1:52:04
  Speaker 1: Earth if we could somehow see magnetic field lines. This
• 1:52:08
  Speaker 1: invisible bubble extends millions of miles around Jupiter, trapping charged
• 1:52:14
  Speaker 1: particles from the solar wind and creating radiation belts so
• 1:52:19
  Speaker 1: intense they can damage spacecraft electronics. The interaction between Jupiter's
• 1:52:26
  Speaker 1: magnetosphere and the thin atmospheres of its moons creates auroras
• 1:52:31
  Speaker 1: on worlds billions of miles from the Sun. Saturn's rings,
• 1:52:37
  Speaker 1: those elegant bands of ice and rock that have captivated
• 1:52:41
  Speaker 1: observers for centuries, turn out to be maintained by incredibly
• 1:52:45
  Speaker 1: complex gravitational relationships between the planet's dozens of moons. Some
• 1:52:51
  Speaker 1: moons shepherd ring particles into narrow bands, while others create
• 1:52:56
  Speaker 1: gaps by sweeping up material in their orbital paths. The
• 1:53:01
  Speaker 1: entire ring system exists in a delicate gravitational balance that
• 1:53:05
  Speaker 1: spans hundreds of thousands of miles, yet can be disrupted
• 1:53:09
  Speaker 1: by objects as small as houses. Even our Sun, the
• 1:53:14
  Speaker 1: gravitational anchor that holds our entire solar system together, reaches
• 1:53:19
  Speaker 1: across billions of miles through mechanisms more subtle than simple
• 1:53:23
  Speaker 1: gravitational attraction. The solar wind, a stream of charged particles
• 1:53:30
  Speaker 1: flowing outward from our star at speeds of several hundred
• 1:53:33
  Speaker 1: miles per second, creates a dynamic pressure that affects the
• 1:53:38
  Speaker 1: orbits of comets, pushes against the magnetospheres of planets, and
• 1:53:43
  Speaker 1: ultimately defines the boundary between our solar system and interstellar space.
• 1:53:47
  Speaker 1: This solar wind pressure creates the heliosphere, a vast bubble
• 1:53:52
  Speaker 1: of solar influence that extends far beyond the orbit of Pluto.
• 1:53:57
  Speaker 1: The boundary where this bubble meets the interstellar medium, called
• 1:54:01
  Speaker 1: the heliopause, represents one possible definition of our solar system's edge.
• 1:54:07
  Speaker 1: But this boundary isn't fixed or static. It expands and
• 1:54:12
  Speaker 1: contracts based on variations in solar activity, and changes in
• 1:54:16
  Speaker 1: the density of the interstellar medium through which our solar
• 1:54:19
  Speaker 1: system is moving. The Voyager spacecraft, our most distant robotic ambassadors,
• 1:54:25
  Speaker 1: have now crossed this boundary and are sending back humanity's
• 1:54:29
  Speaker 1: first direct measurements of the interstellar environment. What they've found
• 1:54:34
  Speaker 1: is that the transition from solar system to interstellar space
• 1:54:38
  Speaker 1: isn't sharp or sudden. Instead, it's a gradual shift through
• 1:54:44
  Speaker 1: multiple boundary layers, each with its own characteristic properties and dynamics.
• 1:54:50
  Speaker 1: This discovery has profound implications for how we think about
• 1:54:53
  Speaker 1: our solar system's true extent. Rather than having a clear
• 1:54:57
  Speaker 1: edge like the surface of a planet, our cosmic neighbourhood
• 1:55:00
  Speaker 1: seems to fade gradually into the larger galactic environment through
• 1:55:04
  Speaker 1: a series of transition zones that extend across multiple astronomical units.
• 1:55:12
  Speaker 1: The question of where our solar system ends and interstellar
• 1:55:16
  Speaker 1: space begins becomes less about identifying a specific boundary and
• 1:55:22
  Speaker 1: more about understanding a complex set of overlapping zones of influence.
• 1:55:27
  Speaker 1: But even as we grapple with these boundary questions, new
• 1:55:30
  Speaker 1: discoveries continue to push our understanding of solar system scale
• 1:55:35
  Speaker 1: in unexpected directions. The detection of interstellar objects passing through
• 1:55:41
  Speaker 1: our solar system, like the asteroid Oumuamua and the comet Borisov,
• 1:55:46
  Speaker 1: reminds us that our cosmic neighbourhood isn't isolated from the
• 1:55:49
  Speaker 1: rest of the galaxy. These visitors from other star systems
• 1:55:53
  Speaker 1: carry with them information about planetary formation processes in alien
• 1:55:57
  Speaker 1: solar systems, providing glimpses of how other stellar families compare
• 1:56:01
  Speaker 1: to our own. The fact that we can detect and
• 1:56:05
  Speaker 1: study these interstellar interlopers reveals just how sophisticated our observational
• 1:56:10
  Speaker 1: capabilities have become. Objects smaller than football fields, moving at
• 1:56:17
  Speaker 1: speeds of tens of miles per second, can now be
• 1:56:20
  Speaker 1: spotted and tracked as they race through our solar system
• 1:56:24
  Speaker 1: on trajectories that will carry them back into the galactic darkness.
• 1:56:30
  Speaker 1: These detections represent an entirely new frontier in astronomy, one
• 1:56:36
  Speaker 1: that promises to reveal the diversity of planetary systems throughout
• 1:56:40
  Speaker 1: our galaxy. But perhaps the most mind-expanding aspect of our
• 1:56:44
  Speaker 1: solar system's scale is how it prepares us to contemplate
• 1:56:49
  Speaker 1: even larger cosmic structures. The distances that seem so impossibly
• 1:56:55
  Speaker 1: vast within our solar system become almost intimate when viewed
• 1:56:59
  Speaker 1: from the perspective of interstellar space. Our entire cosmic neighbourhood,
• 1:57:04
  Speaker 1: from the sun to the outer edge of the Oort cloud,
• 1:57:07
  Speaker 1: occupies only the tiniest fraction of the space between neighbouring
• 1:57:11
  Speaker 1: star systems. If our solar system were shrunk down to
• 1:57:15
  Speaker 1: the size of a coin, the nearest star would still
• 1:57:18
  Speaker 1: be over a mile away. The distances that challenge our
• 1:57:21
  Speaker 1: ability to comprehend within our solar system become negligible when
• 1:57:25
  Speaker 1: measured against the true scale of our galaxy. Yet this
• 1:57:28
  Speaker 1: cosmic perspective also highlights just how extraordinary it is that stable,
• 1:57:33
  Speaker 1: complex systems like our solar system can exist at all
• 1:57:38
  Speaker 1: in a universe dominated by such vast, empty spaces. The
• 1:57:42
  Speaker 1: gravitational forces that bind our cosmic neighbourhood together operate across
• 1:57:47
  Speaker 1: distances so large that their effects become almost impossibly subtle.
• 1:57:52
  Speaker 1: yet somehow remain strong enough to maintain stable orbits for
• 1:57:56
  Speaker 1: billions of years. The delicate balance between gravitational attraction and
• 1:58:02
  Speaker 1: orbital motion that keeps planets in stable paths requires a
• 1:58:06
  Speaker 1: kind of cosmic fine-tuning that seems almost miraculous when contemplated
• 1:58:11
  Speaker 1: from the perspective of galactic distances. This balance becomes even
• 1:58:15
  Speaker 1: more remarkable when you consider that it must be maintained
• 1:58:19
  Speaker 1: not just across space, but across time as well. Our
• 1:58:23
  Speaker 1: solar system has existed in roughly its current configuration for
• 1:58:27
  Speaker 1: over four billion years, during which time our sun has
• 1:58:31
  Speaker 1: travelled completely around the galaxy, roughly 18 times. Throughout this
• 1:58:38
  Speaker 1: cosmic journey, passing close to other star systems, threading through
• 1:58:43
  Speaker 1: spiral arms dense with stellar neighbours, our solar system has
• 1:58:48
  Speaker 1: somehow maintained its structural integrity and continued to provide stable
• 1:58:53
  Speaker 1: conditions for the evolution of life. The fact that complex,
• 1:58:57
  Speaker 1: long-lived structures like our solar system can exist and persist
• 1:59:00
  Speaker 1: in a universe characterised by such enormous scales of distance
• 1:59:04
  Speaker 1: and time speaks to deep principles of cosmic organisation that
• 1:59:08
  Speaker 1: we're only beginning to understand. The same mathematical relationships that
• 1:59:13
  Speaker 1: govern the motion of planets around our sun also determine
• 1:59:16
  Speaker 1: the orbits of star systems around galactic centres and galaxies
• 1:59:21
  Speaker 1: around the centres of galaxy clusters. This hierarchy of cosmic structures,
• 1:59:28
  Speaker 1: each level bound together by gravitational forces operating across increasingly
• 1:59:33
  Speaker 1: vast distances, suggests that the principles we observe in our
• 1:59:37
  Speaker 1: solar system might be universal features of how matter organises
• 1:59:43
  Speaker 1: itself in the universe. The techniques we've developed for understanding
• 1:59:48
  Speaker 1: and navigating our cosmic neighbourhood might provide insights into the
• 1:59:52
  Speaker 1: structure and dynamics of much larger systems extending far beyond
• 1:59:57
  Speaker 1: our local galactic environment. As we continue to probe the
• 2:00:00
  Speaker 1: outer reaches of our solar system and develop more sophisticated
• 2:00:04
  Speaker 1: techniques for detecting and studying distant objects, we're not just
• 2:00:08
  Speaker 1: mapping our local cosmic territory, we're developing the conceptual and
• 2:00:12
  Speaker 1: technological tools needed to understand our place in the vast
• 2:00:16
  Speaker 1: hierarchy of cosmic structures that extends from planetary systems to
• 2:00:21
  Speaker 1: galactic superclusters. question of how big our solar system really
• 2:00:26
  Speaker 1: is thus becomes a gateway to even grander questions about
• 2:00:30
  Speaker 1: the scale and structure of the universe itself. Each measurement
• 2:00:35
  Speaker 1: of distance within our cosmic neighbourhood, each discovery of a
• 2:00:39
  Speaker 1: new object in the outer darkness, each successful navigation of
• 2:00:43
  Speaker 1: a spacecraft across billions of miles of space, adds another
• 2:00:48
  Speaker 1: piece to our understanding of how complex systems can emerge
• 2:00:51
  Speaker 1: and persist across the mind-bending scales of cosmic space and time.
• 2:00:56
  Speaker 1: In probing the true dimensions of our solar system, we're
• 2:00:59
  Speaker 1: not just satisfying scientific curiosity about our local environment, we're
• 2:01:04
  Speaker 1: taking the first steps toward understanding our place in a
• 2:01:07
  Speaker 1: universe whose true scale and complexity may forever exceed our
• 2:01:12
  Speaker 1: ability to fully comprehend yet somehow remains governed by mathematical
• 2:01:17
  Speaker 1: principles elegant enough for finite minds like ours to discover
• 2:01:22
  Speaker 1: and appreciate. And here's where our journey through cosmic distances
• 2:01:26
  Speaker 1: takes perhaps its most mind-bending turn yet. Because when we
• 2:01:32
  Speaker 1: truly grasp the scale of our solar system, we begin
• 2:01:35
  Speaker 1: to understand something that challenges every assumption we have about speed, distance,
• 2:01:41
  Speaker 1: and what it means to be fast in the cosmic arena.
• 2:01:45
  Speaker 1: You see, we live in a world where speed has
• 2:01:47
  Speaker 1: very specific meanings. A car traveling 60 miles per hour
• 2:01:52
  Speaker 1: seems reasonably fast. A jet aircraft cruising at 600 miles
• 2:01:57
  Speaker 1: per hour feels impressively rapid. Even our fastest bullet trains
• 2:02:02
  Speaker 1: racing along at 200 miles per hour give us a
• 2:02:05
  Speaker 1: visceral sense of velocity that we can relate to our
• 2:02:08
  Speaker 1: everyday experience. But here's what will absolutely shatter your perception
• 2:02:13
  Speaker 1: of speed. Right now, as you sit there absorbing these
• 2:02:17
  Speaker 1: cosmic dimensions, you are moving through space at velocities that
• 2:02:23
  Speaker 1: make every human-made vehicle look like it's standing perfectly still.
• 2:02:28
  Speaker 1: And I'm not just talking about Earth's rotation, though that
• 2:02:31
  Speaker 1: alone carries you eastward at over a thousand miles per
• 2:02:34
  Speaker 1: hour if you happen to be sitting near the equator. No,
• 2:02:39
  Speaker 1: we're talking about something far more spectacular. our entire planet
• 2:02:43
  Speaker 1: is hurtling around the Sun at roughly 67,000 miles per hour.
• 2:02:49
  Speaker 1: That's fast enough to circle the entire Earth in about
• 2:02:53
  Speaker 1: 22 minutes. Yet even this breakneck orbital velocity, impressive as
• 2:02:58
  Speaker 1: it sounds, represents just the beginning of our cosmic speed journey.
• 2:03:03
  Speaker 1: Because our Sun, dragging along its entire family of planets, moons,
• 2:03:08
  Speaker 1: asteroids and comets, is racing through the Milky Way galaxy
• 2:03:13
  Speaker 1: at approximately 500,000 miles per hour. At this speed, you
• 2:03:19
  Speaker 1: could travel from New York to Los Angeles in about
• 2:03:21
  Speaker 1: 30 seconds. You could circle the Earth's equator in roughly
• 2:03:27
  Speaker 1: three minutes. Yet this incredible velocity carries us on a
• 2:03:31
  Speaker 1: galactic orbit so vast that it takes our solar system
• 2:03:35
  Speaker 1: roughly 225 million years to complete just one lap around
• 2:03:41
  Speaker 1: our galaxy's centre. Think about that timeline for a moment.
• 2:03:46
  Speaker 1: The last time our solar system was in this exact
• 2:03:49
  Speaker 1: position relative to the galactic centre, the most advanced life
• 2:03:54
  Speaker 1: forms on Earth were primitive marine creatures just beginning to
• 2:03:58
  Speaker 1: venture onto land. Dinosaurs wouldn't appear for another hundred million years.
• 2:04:04
  Speaker 1: The next time we complete this cosmic circuit, our Sun
• 2:04:07
  Speaker 1: will be noticeably older and dimmer, and the face of
• 2:04:10
  Speaker 1: our planet will have been reshaped by geological and evolutionary
• 2:04:14
  Speaker 1: forces we can barely imagine. But even our galaxy's stately
• 2:04:19
  Speaker 1: rotation through space doesn't represent the end of our cosmic
• 2:04:23
  Speaker 1: velocity stack. Our entire galaxy, along with its neighbours in
• 2:04:28
  Speaker 1: what astronomers call the local group, is racing through the
• 2:04:32
  Speaker 1: universe toward an eventual collision. with the Andromeda Galaxy. This
• 2:04:38
  Speaker 1: intergalactic approach occurs at speeds exceeding 250,000 miles per hour,
• 2:04:45
  Speaker 1: fast enough to cross the continental United States in about
• 2:04:48
  Speaker 1: six minutes. When that cosmic collision finally occurs, roughly four
• 2:04:53
  Speaker 1: and a half billion years from now, the gravitational chaos
• 2:04:57
  Speaker 1: will completely reshape both galaxies, potentially flinging our solar system
• 2:05:02
  Speaker 1: into entirely new regions of space or ejecting it altogether
• 2:05:07
  Speaker 1: into the lonely depths of intergalactic void. The very structure
• 2:05:11
  Speaker 1: of our cosmic neighbourhood could be fundamentally altered by gravitational
• 2:05:15
  Speaker 1: forces operating across distances that dwarf even our solar system's
• 2:05:19
  Speaker 1: impressive dimensions. And still, we haven't reached the ultimate expression
• 2:05:24
  Speaker 1: of cosmic motion. The entire local group of galaxies, including
• 2:05:29
  Speaker 1: our Milky Way and Andromeda, participates in the expansion of
• 2:05:33
  Speaker 1: the universe itself. Space itself is stretching, carrying galaxy clusters
• 2:05:39
  Speaker 1: away from each other at velocities that increase with distance.
• 2:05:44
  Speaker 1: The most distant galaxies we can observe are receding from
• 2:05:48
  Speaker 1: us at speeds approaching the velocity of light, not because
• 2:05:52
  Speaker 1: they're moving that fast through space, but because space itself
• 2:05:57
  Speaker 1: is expanding between us. This cosmic expansion affects even our
• 2:06:03
  Speaker 1: solar system in subtle but measurable ways. Over unimaginably long timescales,
• 2:06:09
  Speaker 1: the expansion of space itself will gradually weaken our sun's
• 2:06:14
  Speaker 1: gravitational hold on its most distant subjects. Objects at the
• 2:06:19
  Speaker 1: very edge of the Oort cloud are slowly but inexorably
• 2:06:23
  Speaker 1: drifting away from our star, stolen not by the gravity
• 2:06:27
  Speaker 1: of passing objects, but by the fundamental expansion of the
• 2:06:32
  Speaker 1: universe itself. This process operates so slowly that it would
• 2:06:36
  Speaker 1: take trillions of years to have any noticeable effect on
• 2:06:39
  Speaker 1: our solar system's structure, but the fact that it's happening
• 2:06:43
  Speaker 1: at all reveals something profound about the dynamic nature of
• 2:06:47
  Speaker 1: cosmic architecture. Our solar system isn't a static structure frozen
• 2:06:52
  Speaker 1: in space and time. It's a dynamic, evolving entity, that
• 2:06:58
  Speaker 1: responds to forces operating across multiple scales of distance and duration.
• 2:07:04
  Speaker 1: But here's what makes these cosmic velocities truly mind-melting when
• 2:07:08
  Speaker 1: we consider them in the context of solar system distances.
• 2:07:12
  Speaker 1: Despite racing through space at speeds that make our fastest
• 2:07:15
  Speaker 1: rockets look like they're crawling, the objects in our cosmic
• 2:07:19
  Speaker 1: neighbourhood maintain their relative positions with remarkable stability across billions
• 2:07:24
  Speaker 1: of years. Jupiter has been following roughly the same orbital
• 2:07:29
  Speaker 1: path for over four billion years, despite the fact that
• 2:07:33
  Speaker 1: it's simultaneously participating in our solar system's galactic orbit, our
• 2:07:38
  Speaker 1: galaxy's motion through the local group, and the universe's expansion.
• 2:07:44
  Speaker 1: The gravitational relationships that maintain planetary orbits operate with such
• 2:07:49
  Speaker 1: precision that they can overcome the chaotic influences of our
• 2:07:53
  Speaker 1: participation in multiple cosmic motions operating across vastly different scales.
• 2:08:00
  Speaker 1: This stability in the face of cosmic chaos becomes even
• 2:08:04
  Speaker 1: more remarkable when you consider the mathematical complexity involved in
• 2:08:09
  Speaker 1: maintaining orbital relationships across such enormous distances while participating in
• 2:08:15
  Speaker 1: multiple layers of cosmic motion. Every object in our solar
• 2:08:20
  Speaker 1: system must somehow balance its gravitational relationship with the Sun
• 2:08:24
  Speaker 1: against the subtle influences of galactic tides, the gravitational effects
• 2:08:29
  Speaker 1: of passing stars, and even the weak but persistent influence
• 2:08:33
  Speaker 1: of cosmic expansion. The fact that these delicate gravitational balances
• 2:08:39
  Speaker 1: can persist across billions of years of cosmic evolution suggests
• 2:08:44
  Speaker 1: that our solar system represents something truly extraordinary in the universe.
• 2:08:50
  Speaker 1: We're not just dealing with a large collection of objects
• 2:08:52
  Speaker 1: held together by gravity. We're observing a stable, long-lived structure
• 2:08:58
  Speaker 1: that has somehow learned to dance with forces operating across
• 2:09:02
  Speaker 1: scales from planetary orbits to cosmic expansion. This cosmic choreography
• 2:09:07
  Speaker 1: becomes even more fascinating when you consider how it affects
• 2:09:11
  Speaker 1: our attempts to measure and navigate within our solar system,
• 2:09:15
  Speaker 1: When we send spacecraft to distant planets, we're not just
• 2:09:18
  Speaker 1: calculating trajectories through three-dimensional space. We're plotting courses through a
• 2:09:23
  Speaker 1: four-dimensional spacetime that's simultaneously rotating around our galactic centre, racing
• 2:09:30
  Speaker 1: toward Andromeda, and participating in the expansion of the universe itself.
• 2:09:36
  Speaker 1: The mathematical precision required for these calculations pushes human knowledge
• 2:09:43
  Speaker 1: to its absolute limits. Mission planners must account not only
• 2:09:49
  Speaker 1: for the gravitational influences of planets and moons, but also
• 2:09:53
  Speaker 1: for the subtle effects of our solar system's motion through
• 2:09:56
  Speaker 1: the galaxy, the influence of dark matter halos, and even
• 2:10:01
  Speaker 1: the tiny but measurable corrections imposed by Einstein's theories of relativity.
• 2:10:07
  Speaker 1: Yet somehow, we've mastered this cosmic navigation well enough to
• 2:10:12
  Speaker 1: send robotic explorers throughout our solar system with extraordinary precision.
• 2:10:18
  Speaker 1: We can predict where Jupiter will be in a decade
• 2:10:21
  Speaker 1: with accuracy measured in kilometres, despite the fact that Jupiter
• 2:10:25
  Speaker 1: will have travelled billions of miles through galactic space during
• 2:10:29
  Speaker 1: that time while participating in multiple layers of cosmic motion.
• 2:10:34
  Speaker 1: This navigational mastery reveals something profound about the mathematical elegance
• 2:10:40
  Speaker 1: underlying cosmic motion. Despite the apparent complexity of multiple overlapping
• 2:10:47
  Speaker 1: velocities and gravitational influences, the universe operates according to principles
• 2:10:53
  Speaker 1: precise enough to allow for incredibly accurate long-term predictions across
• 2:10:59
  Speaker 1: mind-bending scales of distance and time. But perhaps the most
• 2:11:03
  Speaker 1: humbling aspect of contemplating our solar system's true scale is
• 2:11:08
  Speaker 1: how it reveals the extraordinary rarity and preciousness of the
• 2:11:12
  Speaker 1: stable conditions have allowed complex structures like planetary systems to
• 2:11:17
  Speaker 1: form and persist. In a universe characterized by such enormous distances,
• 2:11:23
  Speaker 1: such tremendous velocities, and such powerful forces, the existence of
• 2:11:29
  Speaker 1: delicate gravitational relationships capable of maintaining stable orbits for billions
• 2:11:35
  Speaker 1: of years seems almost miraculous. Consider the incredible chain of
• 2:11:41
  Speaker 1: cosmic circumstances had to align perfectly for our solar system
• 2:11:46
  Speaker 1: to exist in its current form. Our location in the
• 2:11:49
  Speaker 1: galaxy had to be just right, far enough from the
• 2:11:53
  Speaker 1: chaotic galactic centre to avoid disruptive gravitational influences, but not
• 2:11:58
  Speaker 1: so far out in the galactic suburbs that we lacked
• 2:12:01
  Speaker 1: access to the heavy elements created by previous generations of stars.
• 2:12:07
  Speaker 1: Our sun, had to form with just the right mass
• 2:12:10
  Speaker 1: to provide stable energy output for billions of years. The
• 2:12:14
  Speaker 1: early gravitational interactions between forming planets had to settle into
• 2:12:19
  Speaker 1: stable configurations that could persist despite the ongoing chaos of
• 2:12:24
  Speaker 1: cosmic evolution. Each of these requirements represents a kind of
• 2:12:29
  Speaker 1: cosmic lottery ticket, and our solar system somehow managed to
• 2:12:33
  Speaker 1: win every single drawing the mathematical probability of all these
• 2:12:38
  Speaker 1: factors aligning perfectly seems vanishingly small. Yet here we are
• 2:12:44
  Speaker 1: living proof that such extraordinary cosmic arrangements not only can exist,
• 2:12:51
  Speaker 1: but can persist long enough for complex chemistry to evolve
• 2:12:55
  Speaker 1: into biology, and biology to evolve into consciousness, capable of
• 2:13:00
  Speaker 1: contemplating its own cosmic origins. This perspective transforms our understanding
• 2:13:08
  Speaker 1: of what it means to ask how big our solar
• 2:13:10
  Speaker 1: system really is. We're not just measuring empty space between
• 2:13:14
  Speaker 1: isolated objects. We're mapping the architecture of a cosmic miracle,
• 2:13:20
  Speaker 1: a stable island of organized matter and energy that has
• 2:13:24
  Speaker 1: somehow learned to maintain its structure across scales of distance
• 2:13:27
  Speaker 1: and time that challenge the very limits of human comprehension.
• 2:13:33
  Speaker 1: Every measurement we make, every spacecraft we navigate across billions
• 2:13:38
  Speaker 1: of miles, every calculation of orbital mechanics across cosmic timescales
• 2:13:44
  Speaker 1: represents not just a scientific achievement, but a kind of
• 2:13:48
  Speaker 1: cosmic archaeology. We're uncovering the hidden relationships and delicate balances
• 2:13:54
  Speaker 1: that allow our extraordinary solar system to exist and persist
• 2:13:59
  Speaker 1: in a universe that seems designed to tear such structures apart.
• 2:14:03
  Speaker 1: And as we continue to probe the outer reaches of
• 2:14:06
  Speaker 1: our cosmic neighbourhood, discovering new objects in the distant darkness
• 2:14:10
  Speaker 1: and mapping the subtle gravitational influences that shape their orbits,
• 2:14:15
  Speaker 1: we're not just expanding our knowledge of local cosmic geography,
• 2:14:20
  Speaker 1: we're developing a deeper appreciation for the remarkable rarity and
• 2:14:24
  Speaker 1: precious fragility of the stable cosmic structures that make our
• 2:14:28
  Speaker 1: existence possible. The question of our solar system's true size
• 2:14:34
  Speaker 1: thus becomes a meditation on the extraordinary nature of cosmic
• 2:14:38
  Speaker 1: organisation itself. In measuring the distances between worlds, we are
• 2:14:43
  Speaker 1: really measuring the spaces between miracles, mapping the architecture of
• 2:14:48
  Speaker 1: cosmic improbability that somehow conspired to create a corner of
• 2:14:53
  Speaker 1: the universe where matter could organise itself into planets and
• 2:14:56
  Speaker 1: moons and asteroid belts and comet clouds. and ultimately into
• 2:15:02
  Speaker 1: the complex arrangements of atoms we call life. Every new
• 2:15:07
  Speaker 1: discovery in the outer solar system, every successful navigation of
• 2:15:12
  Speaker 1: spacecraft across interplanetary distances, every precise prediction of planetary positions
• 2:15:18
  Speaker 1: across cosmic timescales, adds another verse to the most remarkable
• 2:15:23
  Speaker 1: story ever told. The story of how In a universe
• 2:15:28
  Speaker 1: characterised by chaos and expansion and destruction on the largest scales,
• 2:15:34
  Speaker 1: delicate gravitational relationships can create and maintain islands of stability
• 2:15:39
  Speaker 1: and beauty and complexity across distances so vast they defy
• 2:15:44
  Speaker 1: human intuition. We are temporary arrangements of stellar debris that
• 2:15:48
  Speaker 1: have somehow achieved the capacity to contemplate the cosmic architecture
• 2:15:53
  Speaker 1: that contains us. In measuring our solar system's true dimensions,
• 2:15:58
  Speaker 1: we're really measuring the scale of the miracle that made
• 2:16:01
  Speaker 1: our existence possible. And that measurement, however precise our instruments become,
• 2:16:08
  Speaker 1: however far our spacecraft travel, however deep our mathematical understanding grows,
• 2:16:15
  Speaker 1: will always point towards something larger and more wonderful than
• 2:16:19
  Speaker 1: any mere collection of numbers could ever capture. The true
• 2:16:24
  Speaker 1: size of our solar system isn't just about distance. It's
• 2:16:28
  Speaker 1: about the incredible fact that in a universe of such
• 2:16:31
  Speaker 1: unimaginable scale, such tremendous forces, such chaotic motion, something as
• 2:16:39
  Speaker 1: delicate and beautiful and improbably stable as our cosmic neighbourhood
• 2:16:43
  Speaker 1: could exist at all. And having achieved existence could persist
• 2:16:48
  Speaker 1: long enough for some of its matter to wake up
• 2:16:51
  Speaker 1: and wonder about its own origins. In that wondering, in
• 2:16:54
  Speaker 1: that questioning, in that persistent human drive to measure and
• 2:16:59
  Speaker 1: understand and explore, we find perhaps the most remarkable dimension
• 2:17:04
  Speaker 1: of our solar system's true scale. Not just its physical
• 2:17:08
  Speaker 1: extent across light years of space, but its capacity to
• 2:17:12
  Speaker 1: give rise to minds capable of contemplating infinity itself. But
• 2:17:18
  Speaker 1: perhaps the most staggering realisation about our solar system's true
• 2:17:22
  Speaker 1: dimensions comes when we consider what lies in the spaces
• 2:17:27
  Speaker 1: between these cosmic landmarks. You see, when most people imagine
• 2:17:32
  Speaker 1: our solar system, they picture the familiar diagram from textbooks,
• 2:17:38
  Speaker 1: neat circles representing planetary orbits, evenly spaced like ripples on
• 2:17:43
  Speaker 1: a pond. But this sanitised version completely fails to capture
• 2:17:48
  Speaker 1: the mind-bending reality of what actually exists in those seemingly
• 2:17:53
  Speaker 1: empty regions. The space between Mars and Jupiter, for instance,
• 2:17:58
  Speaker 1: isn't just a gap waiting to be crossed. It's home
• 2:18:01
  Speaker 1: to hundreds of thousands of asteroids, each following its own
• 2:18:05
  Speaker 1: unique orbital dance around the Sun. Some of these rocky
• 2:18:08
  Speaker 1: fragments are larger than mountains, while others are no bigger
• 2:18:12
  Speaker 1: than boulders. They tumble through the darkness in a cosmic
• 2:18:17
  Speaker 1: ballet so complex that no human mind could track all
• 2:18:21
  Speaker 1: their interactions simultaneously. But here's what will truly scramble your
• 2:18:26
  Speaker 1: understanding of scale. The asteroid belt containing all these hundreds
• 2:18:31
  Speaker 1: of thousands of objects is so vast that if you
• 2:18:34
  Speaker 1: were standing on one asteroid, The chances of seeing another
• 2:18:38
  Speaker 1: asteroid with the naked eye would be virtually zero. The
• 2:18:42
  Speaker 1: average distance between asteroids is over a million miles. You
• 2:18:47
  Speaker 1: could fire a spacecraft randomly into the asteroid belt, and
• 2:18:51
  Speaker 1: the odds of hitting anything would be astronomically small. This
• 2:18:56
  Speaker 1: emptiness within apparent fullness extends throughout our entire solar system.
• 2:19:02
  Speaker 1: The space between Earth and Mars– which seems so manageable
• 2:19:07
  Speaker 1: when drawn on paper, actually contains a volume roughly equivalent
• 2:19:11
  Speaker 1: to eight billion Earth-sized spheres. The gap between Jupiter and
• 2:19:15
  Speaker 1: Saturn could hold over 20 billion Earth-sized objects without any
• 2:19:19
  Speaker 1: of them touching. We're dealing with emptiness on a scale
• 2:19:24
  Speaker 1: that makes terrestrial concepts of distance seem quaint. Yet within
• 2:19:29
  Speaker 1: these vast empty regions, incredibly subtle forces constantly at work,
• 2:19:36
  Speaker 1: shaping and reshaping the architecture of our cosmic neighbourhood. Gravitational
• 2:19:42
  Speaker 1: resonances create invisible patterns that determine where objects can maintain
• 2:19:48
  Speaker 1: stable orbits, and where they'll be swept away by planetary influences.
• 2:19:55
  Speaker 1: The solar wind carves out magnetic highways and barriers that
• 2:19:59
  Speaker 1: affect the motion of charged particles across billions of miles.
• 2:20:03
  Speaker 1: Even more fascinating are the Trojan asteroids, cosmic hitchhikers that
• 2:20:09
  Speaker 1: share Jupiter's orbit around the sun while maintaining positions roughly
• 2:20:14
  Speaker 1: 60 degrees ahead of and behind the giant planet. These
• 2:20:20
  Speaker 1: objects demonstrate how gravitational relationships can create stability across enormous distances,
• 2:20:28
  Speaker 1: allowing small bodies to maintain fixed positions relative to much
• 2:20:32
  Speaker 1: larger objects despite the complex dance of forces operating throughout
• 2:20:37
  Speaker 1: the solar system. The discovery of these Trojan populations has
• 2:20:42
  Speaker 1: revealed that our solar system contains gravitational sweet spots, regions
• 2:20:47
  Speaker 1: where the competing influences of different massive bodies create zones
• 2:20:51
  Speaker 1: of stability that can trap objects for billions of years.
• 2:20:56
  Speaker 1: Jupiter alone has over 7,000 known trojans, but recent surveys
• 2:21:02
  Speaker 1: suggest there may be hundreds of thousands more too small
• 2:21:05
  Speaker 1: or distant for us to detect. But Jupiter's trojans represent
• 2:21:10
  Speaker 1: just one example of how our solar system's enormous scale
• 2:21:14
  Speaker 1: creates opportunities for gravitational complexity that wouldn't exist in a smaller,
• 2:21:20
  Speaker 1: more compact arrangement. Neptune has its own population of Trojan companions.
• 2:21:26
  Speaker 1: Mars hosts a small collection of co-orbital asteroids. Even Earth
• 2:21:30
  Speaker 1: shares its orbital path with a few tiny companions that
• 2:21:34
  Speaker 1: follow complex trajectories around our planet's Lagrange points. These gravitational
• 2:21:39
  Speaker 1: relationships reveal something profound about the hidden architecture of our
• 2:21:43
  Speaker 1: solar system. What appears from a distance to be a
• 2:21:47
  Speaker 1: simple arrangement of planets orbiting a star actually contains layer
• 2:21:52
  Speaker 1: upon layer of subtle interactions and complex dynamics that operate
• 2:21:58
  Speaker 1: across the full range of solar system distances. Consider the Hildes,
• 2:22:03
  Speaker 1: a group of asteroids that maintain a precise three to
• 2:22:06
  Speaker 1: two orbital resonance with Jupiter. These objects complete exactly three
• 2:22:11
  Speaker 1: orbits around the sun. For every two that Jupiter completes,
• 2:22:15
  Speaker 1: a mathematical relationship so precise that it's maintained across millions
• 2:22:20
  Speaker 1: of years despite the gravitational perturbations from other planets. The
• 2:22:24
  Speaker 1: Hildas occupy a region of space larger than the orbit
• 2:22:27
  Speaker 1: of Mars, yet they move in such perfect synchronisation with
• 2:22:31
  Speaker 1: Jupiter that their relative positions remain essentially unchanged across geological timescales.
• 2:22:39
  Speaker 1: This kind of gravitational choreography extends throughout the outer solar
• 2:22:43
  Speaker 1: system as well. The Kuiper Belt contains families of objects
• 2:22:49
  Speaker 1: locked in various resonances with Neptune, creating a complex structure
• 2:22:54
  Speaker 1: of populated and empty zones that reflects billions of years
• 2:22:58
  Speaker 1: of gravitational sculpting. Some regions are packed with icy bodies,
• 2:23:04
  Speaker 1: while others remain virtually empty due to orbital instabilities that
• 2:23:09
  Speaker 1: eject objects over cosmic time. The precision of these gravitational
• 2:23:16
  Speaker 1: relationships becomes even more remarkable when you consider the distances involved.
• 2:23:21
  Speaker 1: Neptune's influence on Kuiper Belt objects operates across billions of miles,
• 2:23:27
  Speaker 1: yet it's strong enough to maintain mathematical relationships accurate to
• 2:23:32
  Speaker 1: fractions of a percent over millions of orbital periods. It's
• 2:23:37
  Speaker 1: like having a conductor directing a cosmic orchestra, where the
• 2:23:40
  Speaker 1: musicians are scattered across light hours of space, yet somehow
• 2:23:44
  Speaker 1: maintaining perfect synchronisation. But perhaps the most mind-expanding aspect of
• 2:23:50
  Speaker 1: our solar system's true scale emerges when we consider how
• 2:23:54
  Speaker 1: these vast distances affect our very perception of time itself.
• 2:24:00
  Speaker 1: We've grown accustomed to thinking of simultaneity as absolute, assuming
• 2:24:05
  Speaker 1: that when something happens, it happens everywhere at the same moment.
• 2:24:10
  Speaker 1: But the finite speed of light combined with our solar
• 2:24:13
  Speaker 1: system's enormous dimensions, reveals that simultaneity is actually relative to
• 2:24:19
  Speaker 1: position within our cosmic neighbourhood. When a solar flare erupts
• 2:24:25
  Speaker 1: on the Sun's surface, Earth experiences its effects eight minutes later,
• 2:24:31
  Speaker 1: but Mars, depending on its orbital position, might not feel
• 2:24:35
  Speaker 1: those same effects for anywhere from 12 to 24 minutes.
• 2:24:40
  Speaker 1: Jupiter could remain unaware of the solar disturbance for nearly
• 2:24:44
  Speaker 1: an hour. The outer planets might continue their normal existence
• 2:24:48
  Speaker 1: for several hours before the effects propagate outward to their
• 2:24:52
  Speaker 1: distant realms. This means that our solar system doesn't experience
• 2:24:57
  Speaker 1: a unified present moment. Instead, it exists as a collection
• 2:25:02
  Speaker 1: of overlapping temporal zones, each operating on its own slightly
• 2:25:07
  Speaker 1: delayed timeline relative to solar events. A dramatic solar eruption
• 2:25:13
  Speaker 1: creates a wave of cause and effect that propagates outward
• 2:25:16
  Speaker 1: through our cosmic neighbourhood like ripples on a vast pond,
• 2:25:21
  Speaker 1: reaching different worlds at different times and creating a cascade
• 2:25:25
  Speaker 1: of responses that can stretch across days. But the temporal
• 2:25:30
  Speaker 1: complexity of our solar system's scale extends far beyond simple
• 2:25:35
  Speaker 1: light travel delays. The orbital periods of objects throughout our
• 2:25:40
  Speaker 1: cosmic neighbourhood span an incredible range, from Mercury's 88-day year
• 2:25:46
  Speaker 1: to the million-year orbits of some Oort cloud comets. This
• 2:25:50
  Speaker 1: means that different regions of our solar system experience time
• 2:25:55
  Speaker 1: at fundamentally different rates when measured in terms of their
• 2:25:59
  Speaker 1: relationship to the Sun. An object in the inner solar
• 2:26:02
  Speaker 1: system might complete hundreds of orbits during the time it
• 2:26:05
  Speaker 1: takes something in the outer Oort cloud to move through
• 2:26:08
  Speaker 1: just a tiny fraction of its immense orbital path. These
• 2:26:13
  Speaker 1: different temporal rhythms create a kind of cosmic polyrhythm where
• 2:26:17
  Speaker 1: various parts of our solar system are beating to completely
• 2:26:21
  Speaker 1: different drums while somehow maintaining overall structural harmony. The implications
• 2:26:27
  Speaker 1: become even more staggering when you realise that this temporal
• 2:26:31
  Speaker 1: diversity is precisely what allows our solar system to maintain
• 2:26:36
  Speaker 1: its stability across billions of years. If everything operated on
• 2:26:42
  Speaker 1: the same time scale, gravitational interactions would either quickly drive
• 2:26:46
  Speaker 1: objects into collisions or eject them from the system entirely. Instead,
• 2:26:52
  Speaker 1: the vast range of orbital periods creates a natural buffer
• 2:26:56
  Speaker 1: against chaos allowing temporary perturbations to average out over time
• 2:27:01
  Speaker 1: rather than building up into system-destroying instabilities. This temporal architecture
• 2:27:07
  Speaker 1: reveals yet another dimension of what it means to measure
• 2:27:11
  Speaker 1: our solar system's true size. We're not just dealing with
• 2:27:14
  Speaker 1: static distances frozen in space. We're mapping a dynamic system
• 2:27:19
  Speaker 1: where different regions operate according to different temporal rhythms. where
• 2:27:24
  Speaker 1: cause and effect propagate at the speed of light across
• 2:27:27
  Speaker 1: light-hours of distance, where the very concept of simultaneity becomes
• 2:27:32
  Speaker 1: relative to position within our cosmic neighbourhood. The more deeply
• 2:27:36
  Speaker 1: we probe these temporal relationships, the more we realise that
• 2:27:40
  Speaker 1: our solar system's enormous scale isn't just about the space
• 2:27:43
  Speaker 1: between objects. It's about the time relationships that connect distant
• 2:27:48
  Speaker 1: worlds to our central star and to each other. Every
• 2:27:53
  Speaker 1: measurement of distance becomes also a measurement of temporal delay.
• 2:27:58
  Speaker 1: Every calculation of orbital mechanics must account for the finite
• 2:28:03
  Speaker 1: speed at which forces and influences propagate across the vast
• 2:28:07
  Speaker 1: emptiness of interplanetary space. This temporal dimension of solar system
• 2:28:13
  Speaker 1: scale has profound implications for any future human exploration of
• 2:28:18
  Speaker 1: our cosmic neighbourhood. A conversation between Earth and a Mars
• 2:28:23
  Speaker 1: colony would involve delays measured in minutes. Communication with explorers
• 2:28:28
  Speaker 1: in the outer solar system would require the patience of
• 2:28:31
  Speaker 1: geological time, with hours or days passing between question and response.
• 2:28:38
  Speaker 1: But perhaps most humbling of all is the realisation that
• 2:28:42
  Speaker 1: these vast scales of distance and time have been operating
• 2:28:46
  Speaker 1: long before humans existed and will continue long after we're gone.
• 2:28:52
  Speaker 1: Our entire species represents just the briefest instant in our
• 2:28:56
  Speaker 1: solar system's four and a half billion year history. Yet
• 2:29:00
  Speaker 1: in that cosmic eye blink, we've managed to develop the
• 2:29:04
  Speaker 1: mathematical tools and technological capabilities needed to measure and understand
• 2:29:09
  Speaker 1: the true dimensions of our cosmic home. Every successful spacecraft mission,
• 2:29:16
  Speaker 1: every precise prediction of planetary positions, Every discovery of new
• 2:29:21
  Speaker 1: objects in the outer darkness represents a triumph of human
• 2:29:25
  Speaker 1: consciousness over the seemingly impossible challenges posed by cosmic scale.
• 2:29:31
  Speaker 1: We are temporary arrangements of matter that have learned to
• 2:29:34
  Speaker 1: think across light years of space and billions of years
• 2:29:38
  Speaker 1: of time, measuring distances so vast they challenge the very
• 2:29:43
  Speaker 1: foundations of human intuition. So here we are at the
• 2:29:47
  Speaker 1: end of our cosmic journey together, having travelled from your
• 2:29:50
  Speaker 1: backyard all the way to the edge of everything our
• 2:29:53
  Speaker 1: sun can touch. We've crossed distances so vast that light
• 2:29:58
  Speaker 1: itself takes years to make the journey, explored realms where
• 2:30:02
  Speaker 1: time moves differently, and discovered that our solar system isn't
• 2:30:06
  Speaker 1: just big, it's a living, breathing, dynamic universe unto itself. Tonight,
• 2:30:12
  Speaker 1: when you step outside and look up at those same
• 2:30:15
  Speaker 1: points of light that started our adventure, you'll never see
• 2:30:18
  Speaker 1: them the same way again. Because now you know the
• 2:30:22
  Speaker 1: truth about the cosmic ocean we're swimming in, and just
• 2:30:25
  Speaker 1: how extraordinary it is that we're here at all to
• 2:30:29
  Speaker 1: contemplate its infinite mystery. I wish you a very good night.
• 2:30:34
  Speaker 1: I hope you had an amazing time with me here
• 2:30:37
  Speaker 1: at Boring Science. I will see you tomorrow as always.
• 2:30:41
  Speaker 1: Until then, stay curious, keep wondering. This is Boring Science
• 2:30:47
  Speaker 1: signing off. Cheers.