Speaker 1: Somewhere in the southern sky, a single point of light
Speaker 1: waits for a telescope to find it. Astronomers call that
Speaker 1: light our nearest neighbour, and they are telling the truth.
Speaker 1: Alpha Centauri really is the closest star system to our Sun,
Speaker 1: but the word nearest is quietly hiding a monster. Our
Speaker 1: furthest spacecraft has flown for almost 50 years and crossed
Speaker 1: barely one thousandth of one percent of the distance to it.
Speaker 1: Light itself The fastest thing that exists needs more than
Speaker 1: four years to make the trip, and here is the
Speaker 1: part that should unsettle you. Even if humans somehow crossed
Speaker 1: that gap and arrived alive, they could never again share
Speaker 1: a single present moment with the Earth they left behind.
Speaker 1: Welcome to the horrifying distance between neighbours. If these journeys
Speaker 1: through space are the kind of thing you enjoy, it
Speaker 1: would honestly mean a lot if you tapped the like
Speaker 1: button and subscribed. It helps videos like this reach a
Speaker 1: few more curious people like you. Now, get yourself comfortable.
Speaker 1: Let's begin. Every few years, someone updates the poster on
Speaker 1: a classroom wall, and somewhere near the bottom, in small
Speaker 1: friendly letters, a caption promises that Alpha Centauri is our
Speaker 1: nearest neighbor. It is a comforting phrase. Neighbor suggests a fence,
Speaker 1: a shared driveway, a face you might wave to across
Speaker 1: the street. Nearest suggests you could, if you truly wanted to,
Speaker 1: walk there. The words are chosen to make the cosmos
Speaker 1: feel domestic, and they succeed beautifully. When astronomers say that
Speaker 1: Alpha Centauri is the closest star system to our sun,
Speaker 1: they are not exaggerating, and they are not lying. Out
Speaker 1: of the several hundred billion stars wheeling through our galaxy,
Speaker 1: this one system genuinely sits closer to us than any other.
Speaker 1: And that, strangely enough, is exactly where the trouble begins.
Speaker 1: Because the moment you ask what nearest actually means how far,
Speaker 1: in the plain arithmetic of kilometers and years, the friendly
Speaker 1: caption on the poster starts to curdle into something far
Speaker 1: stranger and far more unsettling than any label could ever contain.
Speaker 1: Start with what is actually out there. Because most people
Speaker 1: picture a single star and stop. Alpha Centauri is not
Speaker 1: one star. It is three stars. bound together in a
Speaker 1: slow gravitational relationship that has lasted billions of years. Two
Speaker 1: of them, Alpha Centauri A and Alpha Centauri B, are
Speaker 1: a closely matched pair, one almost a twin of our
Speaker 1: own sun, the other slightly smaller and cooler, the two
Speaker 1: of them circling a shared centre of gravity, the way
Speaker 1: a pair of dancers turn around one point on the floor.
Speaker 1: The third is a small, dim, sullen red dwarf called
Speaker 1: Proxima Centauri, drifting far out on the ragged edge of
Speaker 1: that system. so faint that no human eye has ever
Speaker 1: seen it without the help of a telescope. Together they
Speaker 1: form a trio, a little knot of three suns in
Speaker 1: the dark. And already, before we have travelled a single kilometre,
Speaker 1: the tidy word nearest has begun to fracture, because these
Speaker 1: three stars are not all the same distance from Earth,
Speaker 1: and the gap between them is going to matter far
Speaker 1: more than you might expect. Right now, the closest of
Speaker 1: the three to us is Proxima Centauri, sitting at a
Speaker 1: distance of roughly 4.24 light-years. Its two brighter companions, Alpha
Speaker 1: Centauri A and B, ride a little farther out, at
Speaker 1: about 4.34 light-years. That difference, a tenth of a light-year
Speaker 1: or so, sounds trivial, almost like a rounding error you
Speaker 1: could wave away. It is not. A tenth of a
Speaker 1: light-year is still nearly a trillion kilometres, a gulf far
Speaker 1: larger than our entire planetary solar system. So when someone
Speaker 1: announces that humanity has reached Alpha Centauri, the honest reply
Speaker 1: is a question. Which star? Arriving at Proxima would not
Speaker 1: mean arriving at the sun-like pair. You could cross an
Speaker 1: almost unimaginable distance, plant a flag at the red dwarf,
Speaker 1: and still have a further journey ahead of you to
Speaker 1: reach the other two. A journey longer than anything human
Speaker 1: hands have ever built a machine to survive. Nearest, it
Speaker 1: turns out, is not a single destination. It is at
Speaker 1: least three of them, stacked one behind the other in
Speaker 1: the dark. There is a small, almost poetic cruelty buried
Speaker 1: in the name of that closest star. Proxima is simply
Speaker 1: the Latin word for nearest. When astronomers found this faint
Speaker 1: red dwarf and realised it sat closer to us than
Speaker 1: any other star in the entire sky, they gave it
Speaker 1: a name that means, quite literally, the near one. And
Speaker 1: yet even this, the nearest of the nearest, the closest
Speaker 1: single star to our sun in all the galaxy, lies
Speaker 1: more than four light years from the chair you are
Speaker 1: sitting in. We named it for its closeness, and it
Speaker 1: is still so far away that the fastest thing in
Speaker 1: the universe needs more than four years merely to arrive.
Speaker 1: If the one we actually named the near one is
Speaker 1: this remote, you can already begin to feel what the
Speaker 1: rest of the galaxy is going to be like. And
Speaker 1: here is the first place where human intuition quietly betrays us.
Speaker 1: The phrase light year sounds like a measure of time.
Speaker 1: It has the word year sitting right there inside it,
Speaker 1: People hear four light years and picture four years of travel,
Speaker 1: the way you might picture a four-hour drive to another city.
Speaker 1: But a light year is not a unit of time
Speaker 1: at all. It is a unit of distance, the distance
Speaker 1: that light, moving at the fastest speed the universe permits
Speaker 1: anything to move, covers in one full year. And light
Speaker 1: does not stroll. It crosses about 300,000 kilometers every single second.
Speaker 1: In the time it takes you to blink, a beam
Speaker 1: of light could wrap itself around the Earth several times over.
Speaker 1: Now let that speed run, unbroken, for one entire year.
Speaker 1: And it traces out a line nearly nine and a
Speaker 1: half trillion kilometres long. That line, that single, ludicrous nine
Speaker 1: and a half trillion kilometre line is one light year.
Speaker 1: And the nearest star is more than four of them away.
Speaker 1: Numbers that large stop meaning anything at all. Trillion blurs
Speaker 1: into billion blurs into million. and the brain, quite sensibly,
Speaker 1: throws up its hands. So let me hand you a
Speaker 1: smaller ruler, one that astronomers use inside our own solar system.
Speaker 1: It is called the astronomical unit, and it is simply
Speaker 1: the distance from the Earth to the Sun, about 150
Speaker 1: million kilometres. That distance already dwarfs anything in human experience.
Speaker 1: You could line up nearly 12,000 Earths side by side
Speaker 1: across it. Now, one light year contains roughly 63,000 of
Speaker 1: those astronomical units. 63,000 Earth-to-Sun distances, laid end-to-end, just across
Speaker 1: a single light-year. And Proxima Centauri sits more than four
Speaker 1: light-years away. Carry out the multiplication and the nearest star
Speaker 1: lands at something like 268,000 astronomical units from where you are. 268,000
Speaker 1: times the distance to our own star, just to reach
Speaker 1: the front of the line. That is the true size
Speaker 1: of the word nearest. and so far nothing we have
Speaker 1: said has made it feel any smaller. And here a
Speaker 1: fair question arises, one that deserves a straight answer before
Speaker 1: we go any further. How could anyone possibly know that number?
Speaker 1: We have never sent anything even a fraction of the
Speaker 1: way to Proxima Centauri, so how do we dare to
Speaker 1: say it sits 268,000 astronomical units away and to say
Speaker 1: it with confidence? The answer is one of the quiet
Speaker 1: triumphs of astronomy. and it relies on nothing more exotic
Speaker 1: than a trick your own two eyes play every waking second.
Speaker 1: Hold up one finger at arm's length and look at it,
Speaker 1: closing first one eye and then the other. The finger
Speaker 1: appears to jump sideways against the far wall. Even though
Speaker 1: it has not moved at all, it shifts because you
Speaker 1: are viewing it from two slightly different positions, your left
Speaker 1: eye and your right. The nearer the finger, the bigger
Speaker 1: the jump. That apparent shift, born purely of looking from
Speaker 1: two places at once, is called parallax. and it is
Speaker 1: the foundation on which the entire staircase of cosmic distance
Speaker 1: is built. Now trade your two eyes for something enormously
Speaker 1: farther apart. As the Earth swings around the Sun across
Speaker 1: a year, it carries our telescopes from one side of
Speaker 1: its orbit to the other, two vantage points separated by
Speaker 1: nearly 300 million kilometres, the full width of our path
Speaker 1: around the Sun. Photograph a nearby star in the depths
Speaker 1: of winter, then photograph it again in the heart of summer,
Speaker 1: and that star, like the finger, appears to shift by
Speaker 1: the tiniest sliver against the fixed backdrop of far more
Speaker 1: distant stars behind it. Measure the size of that shift,
Speaker 1: apply the plane geometry a surveyor uses to fix a
Speaker 1: distant landmark, and the star's distance falls straight out of
Speaker 1: the arithmetic. No spacecraft required, no assumptions about engines or fuel,
Speaker 1: just the angle a star traces as we look at
Speaker 1: it from opposite ends of our own orbit. Proxima Centauri,
Speaker 1: being the closest star of all, produces the largest such
Speaker 1: shift of any star in the sky, and even so,
Speaker 1: that shift is heartbreakingly small, less than a single second
Speaker 1: of arc, an angle so fine it is comparable to
Speaker 1: watching a coin edge sideways from tens of kilometres away.
Speaker 1: Astronomers first pulled off this feat on a nearby star
Speaker 1: back in the 1800s, and modern instruments have since refined
Speaker 1: it to staggering precision. So when we say the nearest
Speaker 1: star is 4.24 light-years away, we are not guessing. and
Speaker 1: we are not extrapolating from a dream. It is a
Speaker 1: directly measured fact, wrung out of the sky by the
Speaker 1: simple act of looking from two sides of our orbit,
Speaker 1: a number as solidly established as the distance to the moon.
Speaker 1: And that is exactly what makes it so unsettling. This
Speaker 1: is not a figure we can argue down or engineer away.
Speaker 1: It has been measured, checked, and confirmed. The gulf is
Speaker 1: precisely as wide as it looks. There is one more
Speaker 1: thing worth settling before we ask why any of this
Speaker 1: should matter, and it concerns what actually fills the gap
Speaker 1: between here and there. We tend to picture the solar
Speaker 1: system ending neatly at Neptune, the outermost planet, as though
Speaker 1: the sun's territory had a tidy outer wall. It does not.
Speaker 1: The Sun's true domain reaches far, far beyond the last planet,
Speaker 1: and grasping how far is the final piece of just
Speaker 1: how isolated we really are. Beyond Neptune, the Sun's influence
Speaker 1: continues outward through a vast, sparse frontier. First comes the heliosphere,
Speaker 1: the enormous bubble blown by the solar wind, the stream
Speaker 1: of particles the Sun exhales in every direction, whose edge
Speaker 1: Voyager 1 crossed only after 35 years of flight. But
Speaker 1: even that is not the border. Far beyond it, astronomers
Speaker 1: infer the existence of the Oort cloud, a titanic shell
Speaker 1: of frozen, icy bodies, the dormant seeds of comets wrapped
Speaker 1: around the entire solar system like a faint spherical fog.
Speaker 1: We have never seen it directly. Its existence is deduced
Speaker 1: from where long-period comets fall in from, so it belongs, honestly,
Speaker 1: to the realm of well-founded inference rather than direct sight.
Speaker 1: But if it is there, as nearly all astronomers believe,
Speaker 1: it is staggeringly large. Its inner reaches may begin a
Speaker 1: couple of thousand astronomical units out, and its outer edge
Speaker 1: may extend to something like 100,000 astronomical units from the
Speaker 1: Sun well over a light year away, and by some
Speaker 1: estimates a fair fraction of the entire distance to Proxima Centauri.
Speaker 1: Sit with that for a moment, because it cuts in
Speaker 1: two directions at once. On one hand, It means the
Speaker 1: truly empty no-man's land between our star and the next
Speaker 1: is narrower than the raw distance suggests the sun's own
Speaker 1: faint outer territory, and perhaps a matching shell around Alpha
Speaker 1: Centauri may reach toward one another across the dark, leaving
Speaker 1: a smaller, strictly empty gap in between. On the other hand,
Speaker 1: it makes the human scale of the crossing worse, not better,
Speaker 1: because Voyager 1, our fastest and farthest traveller, will take
Speaker 1: roughly 300 years merely to reach the inner edge of
Speaker 1: the Oort cloud, and something like 30,000 years to pass
Speaker 1: all the way through it, and leave the Sun's domain
Speaker 1: behind at last. 30,000 years just to escape the outskirts
Speaker 1: of our own star's territory, and only then would the
Speaker 1: real journey to Proxima even begin. The Sun does not
Speaker 1: release its grip at Neptune. It holds on, faintly but genuinely,
Speaker 1: for more than a light year in every direction, and
Speaker 1: merely crossing that grip is itself a labour longer than
Speaker 1: all of recorded history. You might reasonably ask why anyone
Speaker 1: should care about a distance this hopeless. Why fix our
Speaker 1: attention on three stars we may never touch? For a
Speaker 1: long time, the honest answer was simply that they were there,
Speaker 1: the closest lights in the dark, the first stop on
Speaker 1: any imagined map of the galaxy, a natural place to
Speaker 1: point a dream. But in just the last few years,
Speaker 1: that abstract longing has been handed something concrete to aim at.
Speaker 1: because we now have real evidence that at least one
Speaker 1: of those stars may not be travelling alone through space.
Speaker 1: Around it and around its dim red companion there appear
Speaker 1: to be worlds. The red dwarf Proxima Centauri is the
Speaker 1: surer case. Astronomers have confirmed that it hosts planets of
Speaker 1: its own, including one, discovered back in 2016, that orbits
Speaker 1: within the star's so-called habitable zone, the narrow band of
Speaker 1: distances where temperatures could in principle allow liquid water to
Speaker 1: sit on a solid surface. A second, smaller world was
Speaker 1: later confirmed on a tighter orbit closer in. There have
Speaker 1: even been hints of a third, still argued over, still unconfirmed,
Speaker 1: the kind of faint signal that lives in the uncomfortable
Speaker 1: space between a genuine discovery and an honest mistake. But
Speaker 1: the headline holds firm. The nearest star to our own
Speaker 1: is not a barren, empty point of light. It has
Speaker 1: a family. And at least one member of that family
Speaker 1: sits squarely in the temperature range we tend to circle
Speaker 1: in red pen. Whenever we go looking for places where
Speaker 1: life might find a foothold, the bigger, brighter, sun-like star
Speaker 1: Alpha Centauri A is a far harder target its own light,
Speaker 1: and the glare of its close companion tend to drown
Speaker 1: out anything faint orbiting nearby. But in 2024, using the
Speaker 1: James Webb Space Telescope, and a special mask designed to
Speaker 1: blot out the star's overwhelming brightness, astronomers caught sight of something.
Speaker 1: A faint speck of infrared light, sitting about twice the
Speaker 1: Earth to Sun distance from the star. When they looked
Speaker 1: again in early 2025, the speck had vanished, which sounds
Speaker 1: like a failure until you realise that a planet on
Speaker 1: a stretched, elongated orbit can swing behind or in front
Speaker 1: of its star and briefly disappear from view. So the
Speaker 1: team did something clever. They simulated millions of possible orbits,
Speaker 1: and out of all that mathematics, a single plausible object emerged.
Speaker 1: A gas giant, roughly the mass of Saturn, tracing a
Speaker 1: long looping path that keeps it somewhere between one and
Speaker 1: two times our own Earth to Sun distance from the star. Now,
Speaker 1: precision matters enormously here, so let me be exact about
Speaker 1: what this is and what it is not. This world
Speaker 1: is a candidate, not a confirmed planet. It has been glimpsed, modelled,
Speaker 1: and argued for carefully in serious scientific papers, but it
Speaker 1: has not yet been pinned down beyond reasonable doubt. It
Speaker 1: appears to sit inside the star's habitable zone, but because
Speaker 1: it looks to be a gas giant rather than a
Speaker 1: rocky world, no one is suggesting it could hold life
Speaker 1: as we understand it, and its own discoverers have been
Speaker 1: refreshingly careful to say that the real test still lies ahead.
Speaker 1: Astronomers will point their instruments back at Alpha Centauri A,
Speaker 1: and wait to see whether the spec reappears exactly where
Speaker 1: the orbits predict. If it does, we may have confirmed
Speaker 1: the closest planet ever directly imaged around a Sun-like star.
Speaker 1: If it does not, it may quietly dissolve back into
Speaker 1: noise and instrument error. That discipline candidate, not certainty, is
Speaker 1: precisely the honesty this whole story is going to demand
Speaker 1: of us again and again. But notice what has happened
Speaker 1: all the same. The nearest star system has stopped being
Speaker 1: an empty signpost, and started becoming a place a trio
Speaker 1: of suns, with at least a handful of worlds circling them,
Speaker 1: one of which we may soon photograph clearly enough to
Speaker 1: give a proper name. And the more real a destination becomes,
Speaker 1: the more the distance to it begins to sting. It
Speaker 1: is one thing to be separated from nothing in particular.
Speaker 1: It is another thing entirely to be separated, by an
Speaker 1: almost incomprehensible gulf, from somewhere you could actually point to
Speaker 1: and genuinely want to reach. So let us finally look
Speaker 1: at that gulf head on. Let us stop hiding behind
Speaker 1: trillions and light years and shrink the whole impossible thing
Speaker 1: down to something small enough to hold in your hand.
Speaker 1: Imagine taking our entire planetary solar system, the Sun at
Speaker 1: the centre, and every planet out to distant Neptune circling
Speaker 1: around it and shrinking that whole spinning disc down until
Speaker 1: it is the size of a small coin, about two
Speaker 1: and a half centimetres across, resting on the desk in
Speaker 1: front of you. At that scale, The sun is not
Speaker 1: even a visible dot. It is a barely-there grain sitting
Speaker 1: at the coin's exact centre. Mercury, Venus, Earth, Mars, all
Speaker 1: of them are microscopic specks crowded invisibly near that grain.
Speaker 1: The giant planets, Jupiter and Saturn, and the two ice
Speaker 1: giants beyond them, ride around out near the coin's rim.
Speaker 1: That coin, that one small circle of metal under your fingertip,
Speaker 1: contains everything most people ever picture when they say the
Speaker 1: word space. Every planet, every moon... Every landing, every robot,
Speaker 1: every photograph humanity has ever taken from the surface of
Speaker 1: another world, all of it fits comfortably inside the coin. Now,
Speaker 1: keeping that scale fixed exactly where it is, where does
Speaker 1: the nearest star fall? Not on the desk, not in
Speaker 1: the room, not in the building. At this scale, Proxima
Speaker 1: Centauri sits about 110 metres away, farther than the length
Speaker 1: of a football field, out past the walls of whatever
Speaker 1: room you are in. across the street, somewhere down the block,
Speaker 1: and between your coin and that distant grain there is nothing.
Speaker 1: No other coins along the way, no halfway markers, no
Speaker 1: islands to rest on, just a vast black unbroken stretch
Speaker 1: of desk and pavement and empty air, with a single
Speaker 1: speck of a star waiting silently at the far end,
Speaker 1: and here is the detail that ought to stop you cold.
Speaker 1: Our farthest spacecraft, the most distant object human beings have
Speaker 1: ever launched, after nearly 50 years of unbroken flight, has,
Speaker 1: at this same scale, crawled only about the width of
Speaker 1: your hand beyond the coin's edge. It has not even
Speaker 1: left the desk, and the neighbour is 100 metres down
Speaker 1: the road. That spacecraft has earned the right to make
Speaker 1: the distance real, because no analogy quite does it the
Speaker 1: way an actual machine can. It is Voyager 1, launched
Speaker 1: in 1977, back when the fastest computers on Earth were
Speaker 1: slower than the phone in your pocket by a factor
Speaker 1: of millions. For almost five decades it has been falling
Speaker 1: outward past the orbits of the giant planets, past the
Speaker 1: edge of the sun's magnetic bubble, out into true interstellar space,
Speaker 1: the first object of human making ever to cross that
Speaker 1: particular threshold. And it is not dawdling. Voyager 1 is
Speaker 1: moving at about 17 kilometres every second. Not 17 kilometres
Speaker 1: an hour, 17 kilometres a second, roughly 61,000 kilometres an hour.
Speaker 1: quick enough to cross the entire United States in a
Speaker 1: handful of minutes. By every human standard we have, Voyager
Speaker 1: 1 is tearing through the dark faster than almost anything
Speaker 1: we have ever built. And in November of 2026, Voyager
Speaker 1: 1 reaches a milestone that sounds at first magnificent. It
Speaker 1: becomes the first human-made object ever to sit one full
Speaker 1: light day from Earth, meaning it will be as far
Speaker 1: away as light itself can travel in 24 hours. At
Speaker 1: that moment, it will be almost 26 billion kilometers from home,
Speaker 1: more than five times farther out than the planet Neptune.
Speaker 1: A radio signal leaving it, racing toward us at the
Speaker 1: speed of light, will take it from rive entire day
Speaker 1: to arrive. For a machine built with 1970s technology, now
Speaker 1: running on a trickle of power weaker than a household lightbulb.
Speaker 1: This is an achievement that borders on the absurd. One
Speaker 1: full light day. Light itself needs a whole day to
Speaker 1: bridge the gap between us and our farthest child, and
Speaker 1: now hold that triumph up against the distance we actually
Speaker 1: care about. Voyager 1, after half a century of flight,
Speaker 1: has reached one light day. The nearest star is more
Speaker 1: than four light years away. sit for a moment with
Speaker 1: the mismatch between those two units a day, set against years.
Speaker 1: To turn a single light day into a single light year,
Speaker 1: you would have to multiply it by 365. To reach Proxima,
Speaker 1: you would need more than four light years well over
Speaker 1: 1500 light days. Put another way, our fastest, farthest, most
Speaker 1: heroic spacecraft, the one we rightly celebrated every milestone, has
Speaker 1: so far covered a little over six hundredths of one
Speaker 1: percent of the way to the nearest star. Not six percent,
Speaker 1: six hundredths of one percent somewhere around one part in
Speaker 1: fifteen hundred of the whole journey, after fifty years. Moving
Speaker 1: faster than a rifle bullet the entire time, and remember
Speaker 1: what Voyager 1 actually represents. This is not some abandoned
Speaker 1: prototype or a timid first attempt. It is the single farthest,
Speaker 1: longest flying, most successful deep space traveller our species has
Speaker 1: ever produced the high water mark of everything human engineering
Speaker 1: has managed to hurl into the dark in all of history.
Speaker 1: Nothing we have ever built has gone farther, or faster,
Speaker 1: for longer, and this champion, this record holder, this best
Speaker 1: we have ever done, is essentially nowhere on the road
Speaker 1: to the nearest star. If our single greatest achievement can
Speaker 1: cover only one part in 1500 of the trip in
Speaker 1: 50 years of flight, then the distance is not merely large.
Speaker 1: It is a different category of thing altogether, a gulf
Speaker 1: that shrugs off our finest efforts as though they had
Speaker 1: never even happened. And it gets quietly worse, because Voyager
Speaker 1: 1 is not even aimed at Alpha Centauri. It is
Speaker 1: simply coasting outward in whatever direction its planetary tour happened
Speaker 1: to fling it, and it will wander the galaxy for
Speaker 1: tens of thousands of years without ever going near our
Speaker 1: nearest neighbour. But suppose it had been launched perfectly sent
Speaker 1: on a flawless straight line toward Proxima Centauri, holding that
Speaker 1: 17km a second pace the entire way. How long would
Speaker 1: the trip take? Not centuries. Not a few thousand years.
Speaker 1: Something on the order of 70,000 years closer to 73
Speaker 1: or 75,000, by the usual reckoning. 70,000 years is not
Speaker 1: a number that belongs to engineering. It is a number
Speaker 1: that belongs to anthropology. That is roughly the span of
Speaker 1: time separating us from the era when our ancestors were
Speaker 1: first spreading out of Africa, painting on cave walls and
Speaker 1: shaping the earliest tools we would still recognise as human.
Speaker 1: Sit with what that would actually require. If some band
Speaker 1: of early humans had somehow launched a voyager toward Proxima Centauri,
Speaker 1: at the very dawn of our species before agriculture, before writing,
Speaker 1: before the wheel, before every empire and language and religion
Speaker 1: that has ever risen and fallen that spacecraft would still
Speaker 1: be out there tonight. still falling through the dark, still
Speaker 1: not arrived. Every migration, every city, every invention, everything that
Speaker 1: has ever happened to human beings would have played out
Speaker 1: while the probe was in transit, and it would still
Speaker 1: have thousands of years of flight left ahead of it
Speaker 1: before it reached the finish line. That is not a
Speaker 1: journey in any ordinary sense. It is a crossing longer
Speaker 1: than the whole story of our species, run across a
Speaker 1: track so long we can barely make out the far end.
Speaker 1: At this point a very reasonable objection rises up, and
Speaker 1: you may already be forming it. Voyager, you might say,
Speaker 1: is old. It is a 1970s machine, lifted by chemical
Speaker 1: rockets and slung outward by the gravity of passing planets.
Speaker 1: Of course it is slow. We have better ideas now,
Speaker 1: faster engines, bolder designs, concepts sitting on drawing boards that
Speaker 1: could leave Voyager standing utterly still. Surely, with the right technology... 70,000
Speaker 1: years collapses down into something a determined civilization could actually contemplate.
Speaker 1: And that objection is entirely fair. It is in fact
Speaker 1: the exact question that every serious thinker about interstellar travel
Speaker 1: has been forced to stare directly in the face. But
Speaker 1: the answer is not the reassuring one you are hoping for,
Speaker 1: and the reason why is where this story begins to
Speaker 1: turn genuinely strange. Because there is a trap waiting inside
Speaker 1: the innocent phrase, go faster. Our intuition insists that speed
Speaker 1: is the whole answer, that if 17 kilometres a second
Speaker 1: buys us a 70,000 year crawl, then simply going 10
Speaker 1: times faster, or 100 times faster, will hand us a
Speaker 1: journey a human civilisation could live with. And yes, the
Speaker 1: arithmetic does shrink. But it does not shrink anywhere near
Speaker 1: as kindly as you expect, and the effort demanded to
Speaker 1: purchase each new increment of speed does not rise gently,
Speaker 1: it detonates. The distance to Alpha Centauri is not a
Speaker 1: wall you can knock flat by pressing harder on the accelerator.
Speaker 1: It is a distance so enormous that even speeds we
Speaker 1: can barely dream of achieving would still demand patience measured
Speaker 1: against the length of human generations, and every attempt to
Speaker 1: shorten the trip forces us to pay a price that
Speaker 1: climbs far faster than the time we manage to claw back.
Speaker 1: So we arrive at our first uncomfortable truth. The nearest
Speaker 1: star is nearest only in the sense that out of
Speaker 1: an ocean of hundreds of billions of stars, it happens
Speaker 1: to sit at the very front of the line. On
Speaker 1: the scale of a coin on your desk, it waits
Speaker 1: 100 meters down the street, with nothing in between. On
Speaker 1: the scale of our fastest spacecraft, it lies more than
Speaker 1: a thousand times beyond where 50 years of unbroken flight
Speaker 1: has managed to carry us. On the scale of a
Speaker 1: single human life, it hides behind some 70,000 years of travel.
Speaker 1: And we have reached all of these dead ends, without
Speaker 1: once stepping outside the realm of speeds humanity has already achieved.
Speaker 1: The obvious next move, then, is to go faster, far,
Speaker 1: far faster, and see just how much of this horrifying
Speaker 1: distance we can burn away. So, let us do exactly that.
Speaker 1: Let us take the boldest, fastest journeys human minds have
Speaker 1: ever dared to imagine, and find out how close they
Speaker 1: can truly bring the nearest star. We ended on a promise,
Speaker 1: the same promise every dreamer eventually makes when the arithmetic
Speaker 1: turns cruel, go faster. Voyager 1 is a museum piece
Speaker 1: with a nuclear heartbeat, lifted by chemical fire and slung
Speaker 1: outward by the gravity of passing planets, and of course
Speaker 1: it crawls. Build something better, press harder on the accelerator,
Speaker 1: and surely that monstrous 70,000 year crossing folds down into
Speaker 1: a number a determined civilisation could actually stomach. It is
Speaker 1: the most natural thought in the world, and it is
Speaker 1: exactly the thought this part exists to take apart. Because
Speaker 1: when you actually run the numbers on going faster, not
Speaker 1: with imaginary engines, but with the real speeds humanity has
Speaker 1: already reached, you discover something that ordinary intuition never sees coming.
Speaker 1: The distance to the nearest star does not yield gently
Speaker 1: to speed. It resists it, absorbs it, swallows enormous multiples
Speaker 1: of velocity, and hands back only the smallest scraps of time.
Speaker 1: And to feel why, we need a different ruler than
Speaker 1: the ones we have used so far. Not a coin
Speaker 1: on a desk. A human life. So let us fix
Speaker 1: that ruler in place before we start. Because everything in
Speaker 1: this part is going to be measured against it. Take
Speaker 1: a long, full human life. Call it 80 years. Birth
Speaker 1: to death. A good and complete span by any standard
Speaker 1: our species has ever known. Take a human generation. The
Speaker 1: gap from a parent to a child at roughly 25 years...
Speaker 1: and take the whole of what we grandly call recorded history,
Speaker 1: every written word, every empire, every dynasty, every name we
Speaker 1: still remember, which reaches back something like 5,000 years, no further.
Speaker 1: Those three numbers are the true scale of a human being,
Speaker 1: not the light year, not the astronomical unit, a life,
Speaker 1: a generation, the few thousand years of everything we have
Speaker 1: ever bothered to write down. Hold those against the journey
Speaker 1: to Alpha Centauri, and the distance stops being an abstraction
Speaker 1: and becomes something that presses directly on the shape of
Speaker 1: a human existence. Start again then, with the speed we
Speaker 1: already know. Voyager 1 moves at about 17 kilometres every second,
Speaker 1: and aimed perfectly at Proxima Centauri, it would arrive in
Speaker 1: the neighbourhood of 73,000 years. Now measure that not in
Speaker 1: raw years, but in the ruler we just built. 73,000
Speaker 1: years is more than 900 complete human lifetimes. lived one
Speaker 1: after another cradle to grave each person handing the journey
Speaker 1: to the next like a torch that never once goes out.
Speaker 1: It is roughly 3,000 human generations, parent to child to grandchild,
Speaker 1: repeated until the number stops meaning anything, and it is
Speaker 1: around 14 or 15 times the entire length of recorded history,
Speaker 1: every pharaoh and emperor and revolution we have ever chronicled.
Speaker 1: stacked end to end more than a dozen times over,
Speaker 1: just across from our star to the nearest one. That
Speaker 1: is the trip at the best cruising speed humanity has
Speaker 1: ever achieved. 900 lifetimes for a single crossing. But Voyager,
Speaker 1: you insist, is old and slow, and we have done
Speaker 1: far better since. And that is true, we have. So
Speaker 1: let us not compare the nearest star to a 1970s
Speaker 1: probe at all. Let us compare it to the single
Speaker 1: fastest object human beings have ever built. the outright speed
Speaker 1: champion of our entire species, the Parker Solar Probe. This
Speaker 1: spacecraft does something Voyager never could. It dives again and again,
Speaker 1: straight toward the sun, using our own star's gravity to
Speaker 1: whip itself into a frenzy, and at its closest approaches,
Speaker 1: it has reached a speed of roughly 190 kilometers per second,
Speaker 1: something on the order of 690,000 kilometers an hour. Nothing
Speaker 1: made by human hands has ever moved faster. It is
Speaker 1: more than 10 times quicker than Voyager. If raw velocity
Speaker 1: is the answer to the distance, this is the best
Speaker 1: answer we have ever produced. So point it at Proxima
Speaker 1: Centauri and let it run. What happens to our 73,000-year
Speaker 1: crawl when we swap in the fastest machine in human history?
Speaker 1: It drops genuinely, dramatically, all the way down to something
Speaker 1: like 7,000 years, and there is the trap, sprung in
Speaker 1: a single sentence. We took the crown jewel of human propulsion,
Speaker 1: an object more than ten times faster than our farthest traveller,
Speaker 1: and the journey to the nearest star still runs to 7,000 years.
Speaker 1: That is still longer than all of recorded history. If
Speaker 1: the Parker Solar Probe had launched toward Proxima at the
Speaker 1: dawn of the first written language, carrying that record-shattering speed
Speaker 1: the entire way, it would not be halfway there yet.
Speaker 1: Our absolute best, our fastest possible, our undisputed champion, and
Speaker 1: it buys a trip that still outlasts civilisation itself. And
Speaker 1: notice the cheat we quietly allowed ourselves, because it makes
Speaker 1: the picture even worse. The Parker Solar Probe does not
Speaker 1: actually travel at that speed in any useful sense. It
Speaker 1: only touches 190km per second for a few brief hours
Speaker 1: at the very bottom of its plunge toward the sun,
Speaker 1: borrowing that velocity from solar gravity, and then it climbs
Speaker 1: away and slows right back down. a stone thrown hard
Speaker 1: that inevitably falls. That blistering number is not a cruising
Speaker 1: speed at all. It is a momentary flourish, a speed
Speaker 1: the probe cannot keep and was never meant to keep.
Speaker 1: To send anything to Proxima at that pace, you would
Speaker 1: have to somehow bottle that fleeting velocity and hold it, unbroken,
Speaker 1: across four and a quarter light years of empty space,
Speaker 1: a feat we have no means whatsoever of accomplishing. And
Speaker 1: even if we could, even granting ourselves that impossible gift
Speaker 1: for free, the answer still comes back 7,000 years. The
Speaker 1: universe barely blinks. This is the pattern that ordinary intuition
Speaker 1: never grasps, so let us drag it fully into the
Speaker 1: light and make it undeniable. Speed and time do trade
Speaker 1: against each other, but the exchange rate on a distance
Speaker 1: this vast is punishing, and the human ruler makes the
Speaker 1: punishment obvious. Begin from Voyager's 73,000 years and start buying speed.
Speaker 1: Double it. Build an engine twice as good as anything
Speaker 1: that has ever flown, and the trip falls to around 36,000 years.
Speaker 1: You have doubled the greatest speed in human history, and
Speaker 1: the crossing is still hundreds of lifetimes long. Go 10
Speaker 1: times faster than Voyager, which is already faster than our
Speaker 1: real champion can cruise, and you land near 7,000 years,
Speaker 1: still longer than everything we have ever written down. Go
Speaker 1: 100 times faster than Voyager, a speed that exists only
Speaker 1: on paper, and the journey finally drops to something like
Speaker 1: 700 years. Seven centuries. Better but still, the span from
Speaker 1: the height of the Middle Ages to today, an unbroken
Speaker 1: flight so long that whole languages would be born and
Speaker 1: die aboard the ship before it arrived. And here is
Speaker 1: the line where the whole problem crystallises. To bring the
Speaker 1: journey down to a single human life, to make it
Speaker 1: possible for one person to be born at launch and,
Speaker 1: as an old woman, watch Proxima Centauri swell in the
Speaker 1: window before she dies, you need to go roughly a
Speaker 1: thousand times faster than Voyager 1, not twice as fast,
Speaker 1: not ten times, a thousand times, and a thousand times
Speaker 1: 17 km per second is 17,000 km per second, which
Speaker 1: is not a modest engineering upgrade at all. It is
Speaker 1: nearly 6% of the speed of light, 5.7%, to be
Speaker 1: exact a velocity so far beyond anything humanity has achieved
Speaker 1: or has any working means to achieve, that it belongs
Speaker 1: to a different conversation entirely. That is the wall this
Speaker 1: part has been walking you toward. The distance to the
Speaker 1: nearest star does not fold down into a human lifetime,
Speaker 1: through ordinary improvement, through better rockets or bolder chemistry or
Speaker 1: a clever gravity trick. It surrenders to a lifetime only
Speaker 1: at a fraction of the speed of light, and reaching
Speaker 1: a fraction of the speed of light is a problem
Speaker 1: of a completely different and far more violent kind. Sit
Speaker 1: with the shape of that, because it overturns the entire
Speaker 1: instinct we started with. We began this part certain that
Speaker 1: speed was the answer, that the 70,000 year crawl was
Speaker 1: merely the fault of old, slow machines. But the crawl
Speaker 1: is not really a machine problem at all. It is
Speaker 1: a distance problem. Every reasonable, buildable, imaginable improvement in propulsion,
Speaker 1: every factor of two, every factor of ten, every factor
Speaker 1: of a hundred, is devoured by four and a quarter
Speaker 1: light years of emptiness, and gives back a trip. still
Speaker 1: measured in centuries or millennia. The only speeds that can
Speaker 1: defeat the human ruler are relativistic speeds, and those are
Speaker 1: not improvements to what we do now. They are a
Speaker 1: leap into physics we have never once touched with anything
Speaker 1: heavier than a single subatomic particle. But suppose, just suppose
Speaker 1: that we made peace with the crawl instead of fighting it.
Speaker 1: Suppose we stopped demanding that any single traveller live to
Speaker 1: see the destination, and simply accepted that the journey would
Speaker 1: outlast everyone who began it. This is the honest logic
Speaker 1: behind the oldest interstellar idea of all, the generation ship.
Speaker 1: Do not build a faster engine, build a slower promise.
Speaker 1: Launch not a probe, but a world, a vessel large
Speaker 1: enough to carry a living community, one that is born,
Speaker 1: grows old, and dies in transit, generation after generation, so
Speaker 1: that the great-great-grandchildren of the founders are the ones who
Speaker 1: finally arrive. It is a concept. Nothing more no such
Speaker 1: ship exists. or is close to existing, and every part
Speaker 1: of it, from the closed ecology to the social order,
Speaker 1: remains firmly on the drawing board. But as a way
Speaker 1: of thinking, it exposes the true cost with brutal clarity.
Speaker 1: Because a generation ship does not shorten the distance, it
Speaker 1: simply changes who pays for it. Run the human ruler
Speaker 1: across such a voyage, and the toll is staggering. Even
Speaker 1: a relatively swift generation ship, moving far faster than anything
Speaker 1: we can currently build, might still take many centuries to arrive,
Speaker 1: which means dozens of generations would be conceived, would live
Speaker 1: entire lives, and would die inside a metal hull, never
Speaker 1: having stood on the planet they were sailing toward, and
Speaker 1: never having known the planet their ancestors left. An entire
Speaker 1: chain of human beings, hundreds of them, would exist purely
Speaker 1: as the middle of a journey, not the beginning who
Speaker 1: chose it, not the end who arrive, but the vast
Speaker 1: anonymous span in between, born into a corridor between two
Speaker 1: stars with no memory of one world and no hope
Speaker 1: of reaching the other in their lifetime. The distance does
Speaker 1: not go away on a generation ship. It is paid
Speaker 1: in full by people who never asked to pay it.
Speaker 1: And notice that we have, once again, quietly waved away
Speaker 1: the hardest part. To speak of a generation ship at
Speaker 1: all is to assume you could actually build a world
Speaker 1: that keeps a community of human beings alive, unassisted, for centuries,
Speaker 1: And that assumption hides a problem every bit as daunting
Speaker 1: as the propulsion it tries to sidestep. Think about what
Speaker 1: such a sealed vessel would truly have to do. It
Speaker 1: would have to be a complete self-contained world in miniature.
Speaker 1: Every breath of air scrubbed clean and used again. Every
Speaker 1: drop of water drunk, passed, purified and drunk once more.
Speaker 1: Every scrap of food grown, eaten, composted and grown afresh.
Speaker 1: Around and around for hundreds of years. without a single
Speaker 1: delivery from outside, and without one irreplaceable ingredient ever running out,
Speaker 1: our most ambitious sealed ecosystem experiments here on Earth, run
Speaker 1: for a mere handful of people over a mere handful
Speaker 1: of years, have struggled and faltered and needed rescuing from
Speaker 1: the outside air. A starship could never be rescued from
Speaker 1: the outside air, because there would be no outside air,
Speaker 1: only the same finite atmosphere, cycling through the same lungs
Speaker 1: and the same leaves, for longer than most nations have existed,
Speaker 1: and a closed loop like that is a fragile thing.
Speaker 1: On Earth, when a harvest fails or a disease sweeps
Speaker 1: through the crops, the wider world absorbs the shock. Food
Speaker 1: comes from elsewhere while the trouble passes. Aboard a sealed
Speaker 1: ship there is no elsewhere. A blight that ruins the crops,
Speaker 1: a fault that poisons the water, a slow imbalance that
Speaker 1: lets one gas build up and another run thin, any
Speaker 1: of these, in a world with no reserves and no resupply,
Speaker 1: could cascade from an inconvenience into a catastrophe and with
Speaker 1: no outside margin to cushion it. The whole system must
Speaker 1: not merely work, but work in perfect balance, self-correcting, for
Speaker 1: a span longer than the memory of most civilizations, with
Speaker 1: everyone's life riding on it every single day. The living
Speaker 1: machinery is only half of it, the other half is
Speaker 1: the people, and a small, sealed population turns out to
Speaker 1: be fragile in ways that have nothing to do with engines.
Speaker 1: A community aboard such a ship could not be too small,
Speaker 1: or the slow grind of chance would erode it, and
Speaker 1: it could not be too large, or the cost of
Speaker 1: hauling all those extra mouths to a fraction of light
Speaker 1: speed would climb straight back up the impossible energy curve.
Speaker 1: Somewhere between those limits sits a narrow band, a village
Speaker 1: of a few hundred, perhaps a few thousand. Souls who must,
Speaker 1: generation after generation, keep alive not just their bodies but
Speaker 1: every skill their descendants will one day need. How to
Speaker 1: repair the reactor, how to tend the crops, how to
Speaker 1: practice the medicine. how to run the world, lose a
Speaker 1: single vital craft to one bad generation that failed to
Speaker 1: teach it, and there is no library run to the
Speaker 1: next town over, no expert to summon from a home
Speaker 1: that swallows every message for years. The knowledge either survives
Speaker 1: intact aboard that one small hull, taught faithfully from parent
Speaker 1: to child down a chain hundreds of links long, or
Speaker 1: it is gone. And with it, perhaps, the mission. There
Speaker 1: is even a cruel circularity buried in the size of
Speaker 1: such a world. To be truly self-sufficient for centuries, the
Speaker 1: ship cannot be a slender dart. It must carry the
Speaker 1: mass of a small biosphere soil in which to grow crops,
Speaker 1: water enough to close the cycle, air enough to breathe, workshops,
Speaker 1: spare materials, and the raw stock to manufacture replacements for
Speaker 1: anything that breaks. All of that is weight, and enormous
Speaker 1: weight at that. But every additional tonne is a tonne
Speaker 1: that must itself be accelerated toward the stars. and we
Speaker 1: have already seen how viciously the energy cost climbs with
Speaker 1: mass and speed together. The more self-sufficient you make the ship,
Speaker 1: the heavier it becomes. The heavier it becomes, the more
Speaker 1: impossible it is to move quickly. The more slowly it moves,
Speaker 1: the longer the voyage lasts. And the longer the voyage lasts,
Speaker 1: the more self-sufficient the ship must be to survive it.
Speaker 1: Each requirement feeds the next, tightening like a knot that
Speaker 1: pulls harder the more you struggle against it. A generation
Speaker 1: ship is not a single hard problem. It is a
Speaker 1: nest of hard problems, each one making the others worse.
Speaker 1: And every one of these calculations, every lifetime and generation
Speaker 1: and century we have stacked up, has been quietly hiding
Speaker 1: a second problem, one we raised earlier and can no
Speaker 1: longer avoid. We keep saying, reach Alpha Centauri as though
Speaker 1: it were a single place, a door you walk through once.
Speaker 1: It is not. Remember that this is a system of
Speaker 1: three stars. and they are not sitting together at the
Speaker 1: same spot. The nearest of them, Proxima Centauri, is the
Speaker 1: one all our journey times have secretly been aimed at,
Speaker 1: because it is the closest but Proxima is a considerable
Speaker 1: distance out from its two brighter siblings, the Sun-like pair
Speaker 1: Alpha Centauri A and B. That inner gap is not small.
Speaker 1: Proxima orbits the pair at a remove of very roughly
Speaker 1: a fifth of a light year, something like 13,000 astronomical units. 13,000
Speaker 1: times the distance from the Earth to our own Sun.
Speaker 1: Let that inner distance meet the human ruler too, because
Speaker 1: it delivers the final blow to the fantasy of arrival.
Speaker 1: Suppose a crew, against all odds, reaches Proxima Centauri. They
Speaker 1: have crossed the Great Gulf. They stand, in whatever sense
Speaker 1: a crew can stand, at the nearest star. Have they
Speaker 1: reached Alpha Centauri? Only one third of it. To cross
Speaker 1: from Proxima to the Sun-like pair, That inner hop of
Speaker 1: a fifth of a light year would itself take, at
Speaker 1: Voyager's speed, something on the order of three or four
Speaker 1: thousand years. The leftover journey between two members of the
Speaker 1: same star system, the part we casually round away when
Speaker 1: we say the nearest neighbour, is on its own longer
Speaker 1: than all of recorded history. And even the two sun-like
Speaker 1: stars are not a single target. A and B circle
Speaker 1: each other on a stretched orbit that carries them anywhere
Speaker 1: from about 11 to 36 times the Earth to Sun
Speaker 1: distance apart. so that reaching one is not the same
Speaker 1: as reaching the other. The nearest star system is not
Speaker 1: a destination. It is a scattered archipelago of three suns,
Speaker 1: and touching one of its islands leaves you with crossings
Speaker 1: still ahead of you longer than human history itself. So
Speaker 1: the word nearest, which cracked once already, now shatters completely
Speaker 1: under the weight of time. It is nearest across a
Speaker 1: gulf that our fastest real machine would need 7,000 years
Speaker 1: to cross. It is nearest at a distance that swallows
Speaker 1: a thousand-fold increase in speed and still asks for a
Speaker 1: full human life in return. It is nearest as a
Speaker 1: place whose three stars are themselves separated by journeys longer
Speaker 1: than civilization. Every honest way we have of measuring it
Speaker 1: by lifetimes, by generations, by the whole span of the
Speaker 1: written past returns the same verdict. At any speed humanity
Speaker 1: has actually achieved, or can achieve through ordinary improvement, the
Speaker 1: nearest star is not a place a human being can go.
Speaker 1: It is a place a human being can only aim
Speaker 1: a long, slow chain of descendants toward and hope, and
Speaker 1: yet the calculation refused, again and again, to leave us
Speaker 1: anywhere but one exit. Every path we tried, the champion probe,
Speaker 1: the doubled engine, the hundredfold leap, even the melancholy patience
Speaker 1: of the generation ship kept pointing at the same narrow door.
Speaker 1: The only way to bring the nearest star inside the
Speaker 1: reach of a single human life is to move at
Speaker 1: a real fraction of the speed of light, not 17
Speaker 1: kilometres per second, not 190, 17,000, or 30,000, or 60,000
Speaker 1: kilometres per second velocities, where the numbers finally, mercifully collapse,
Speaker 1: where 70,000 years become 70, where a person could plausibly
Speaker 1: outrun the distance instead of merely bequeathing it. That is
Speaker 1: the promised land. That is the speed that would change everything.
Speaker 1: But nothing in this universe is faster than it is difficult,
Speaker 1: and the universe does not hand out fractions of light
Speaker 1: speed for free. To move a spacecraft at 6%, or 12%,
Speaker 1: or a fifth of the speed of light is not
Speaker 1: a matter of building a slightly better engine. It is
Speaker 1: a matter of pouring in quantities of energy that stagger
Speaker 1: the imagination, of surviving an emptiness that turns lethal the
Speaker 1: instant you move fast enough through it, of solving a
Speaker 1: problem so overlooked that that most people never even think
Speaker 1: to ask it the problem of how, having reached such
Speaker 1: a speed, you could ever possibly stop. So we have
Speaker 1: found our door, and it opens onto something far stranger
Speaker 1: than distance. It opens onto the price the universe charges
Speaker 1: for speed itself. And that price, the energy, the shielding,
Speaker 1: the aiming, and the terrible arithmetic of braking is where
Speaker 1: we go next. Every road we walked led to the
Speaker 1: same narrow door. If a human being is ever to
Speaker 1: be born beside our star and die within sight of another,
Speaker 1: the ship carrying them must move at a real fraction
Speaker 1: of the speed of light, not 17 kilometres per second,
Speaker 1: but 17,000, 30,000, 60,000, velocities where 70,000 years of crawling
Speaker 1: finally collapses into something a single life can hold. We
Speaker 1: found the door. Now we have to pay to walk
Speaker 1: through it. And the universe, it turns out, does not
Speaker 1: price speed the way our intuition expects. It does not
Speaker 1: charge a little more for a little more. It charges savagely, exponentially,
Speaker 1: at every level at once, in energy, in survival, in aim,
Speaker 1: and in the one demand almost nobody thinks to ask
Speaker 1: about until it is far too late. This part is
Speaker 1: the invoice, and by the end of it, the reason
Speaker 1: interstellar travel remains a dream and not a schedule will
Speaker 1: feel less like a failure of ambition and more like
Speaker 1: a wall built into the structure of reality itself. Begin
Speaker 1: with energy, because energy is the tollgate you cannot sneak past.
Speaker 1: There is a simple, merciless piece of physics governing how
Speaker 1: much it costs to make something move, and it is this.
Speaker 1: The energy of motion does not grow in step with speed.
Speaker 1: It grows with the square of speed. Hear that slowly,
Speaker 1: because the whole tragedy is folded inside it. If you
Speaker 1: want to go twice as fast, you do not need
Speaker 1: twice the energy you need four times as much. 10
Speaker 1: times as fast demands 100 times the energy. 100 times
Speaker 1: as fast demands 10,000 times the energy. The bill does
Speaker 1: not rise as you accelerate, it explodes. And this is
Speaker 1: before relativity even enters the room. As you push a
Speaker 1: ship toward a genuine fraction of light speed, the equations
Speaker 1: of relativity make the curve steeper still, so that the
Speaker 1: closer you creep to the speed of light, the more
Speaker 1: energy each additional sliver of velocity consumes. climbing toward a
Speaker 1: demand that would, at light speed itself, become infinite. This
Speaker 1: is not an engineering shortfall. It is a calculation from
Speaker 1: known physics, as solid as anything we understand, and it
Speaker 1: means that speed is the single most expensive thing you
Speaker 1: can buy in this universe. Put a number to it, gently,
Speaker 1: because the number is the point. Take a single sizeable
Speaker 1: crude ship, not a fleet, not a city, just one
Speaker 1: vessel of perhaps a thousand tons, modest for something meant
Speaker 1: to carry living people across the dark. Push it to
Speaker 1: merely a tenth of the speed of light, well short
Speaker 1: of the velocities that would save a human lifetime. The
Speaker 1: energy of motion locked into that ship, at that speed,
Speaker 1: works out to something comparable to a substantial fraction of
Speaker 1: everything human civilization generates. In an entire year, every power plant,
Speaker 1: every reactor, every burning barrel of oil on Earth, poured
Speaker 1: into one ship. And that is the theoretical flaw, the
Speaker 1: energy that ends up purely as motion in a perfect
Speaker 1: world with no losses at all. Real engines are nowhere
Speaker 1: near perfect. They waste most of what they consume as
Speaker 1: heat and light and useless exhaust. Fold in those inefficiencies
Speaker 1: and the true energy demand balloons far beyond the clean minimum.
Speaker 1: To go faster than a tenth of light speed, which
Speaker 1: is exactly what saving a human life requires, you climb
Speaker 1: back onto that squaring curve and the cost multiplies again
Speaker 1: and again. The energy needed to fling one crewed ship
Speaker 1: to the nearest star at survivable speed is not a
Speaker 1: quantity we are short of. It is a quantity that
Speaker 1: dwarfs the output of our entire species. This is the
Speaker 1: hard floor beneath every propulsion concept humanity has ever sketched,
Speaker 1: and it is worth walking up the ladder of those
Speaker 1: concepts to see how each one runs headlong into it.
Speaker 1: Start at the very bottom rung with the most audacious
Speaker 1: and most brutally simple idea anyone ever drew up in earnest.
Speaker 1: In the late 1950s, a team of first-rate physicists and engineers,
Speaker 1: including some of the finest minds of the atomic age,
Speaker 1: began serious work on a concept called Project Orion. Its
Speaker 1: logic was breathtaking in its crudeness. If you want to
Speaker 1: move something colossal, do not build a delicate engine at all. Instead,
Speaker 1: drop nuclear bombs out the back of your ship, one
Speaker 1: after another, and detonate them behind a massive shock-absorbing plate.
Speaker 1: Each explosion slams against the plate and shoves the whole
Speaker 1: vessel forward. Then another bomb, another shove, and another arrhythmic
Speaker 1: pounding of atomic blasts, kicking a spacecraft up to tremendous speed.
Speaker 1: It sounds like madness, and yet on paper it very
Speaker 1: nearly worked. Orion was studied with real rigor for years.
Speaker 1: Its designers ran the numbers, tested scale models driven by
Speaker 1: conventional explosives, and convinced themselves that a ship pushed by
Speaker 1: nuclear pulses could carry enormous payloads across the solar system,
Speaker 1: and that stretched-out interstellar versions might, in principle, reach a
Speaker 1: few percent of the speed of light over a voyage
Speaker 1: of centuries. To grasp how far the idea was actually pushed,
Speaker 1: consider that its designers did not shy away from the
Speaker 1: largest versions imaginable. Some sketches at the far end imagined
Speaker 1: vessels the size of small towns, driven by many thousands
Speaker 1: of nuclear charges released in sequence, coasting for centuries toward
Speaker 1: a neighbouring star. The pusher plate, the great slab that
Speaker 1: would absorb each blast, was not hand-waving either. The team
Speaker 1: worked hard on how such a plate could survive being
Speaker 1: struck over and over again. by the fury of a
Speaker 1: nuclear detonation without vaporizing or shaking the ship to pieces.
Speaker 1: These were sober calculations by people who understood nuclear weapons
Speaker 1: better than almost anyone alive. But Orion collided with walls
Speaker 1: of every kind. The most immediate was legal and moral.
Speaker 1: Detonating a long string of nuclear weapons in space runs
Speaker 1: headlong into the treaties that ban exactly that. Signed in
Speaker 1: part to keep the heavens free of atomic fire, and
Speaker 1: no one relished a launch that would scatter radioactive fallout
Speaker 1: across the sky on the way up. And even setting
Speaker 1: all of that aside, an interstellar Orion faced the same
Speaker 1: tyranny every concept faces. To reach the nearest star in
Speaker 1: anything short of millennia, it would need a quantity of
Speaker 1: nuclear devices, so vast, thousands upon thousands of bombs, that
Speaker 1: the whole scheme buckled under its own scale. So let
Speaker 1: me be exact, as this story always must be. Project
Speaker 1: Orion was genuinely studied and genuinely serious, but it was
Speaker 1: never built, never flown and, at interstellar scale, never anything
Speaker 1: more than a bold paper design. It is the first
Speaker 1: rung on the ladder and it already brushes the ceiling
Speaker 1: of what raw brute force can buy. Climb one rung
Speaker 1: higher to the most credible of the serious proposals. Nuclear fusion,
Speaker 1: the same reaction that lights the sun. In the 1970s,
Speaker 1: a group of British engineers ran a careful study called
Speaker 1: Project Daedalus, a design never built for an uncrewed probe
Speaker 1: that would ride controlled fusion explosions up to roughly 12%
Speaker 1: of the speed of light and coast to a nearby star.
Speaker 1: A later effort, Project Icarus, revisited and refined the same
Speaker 1: fusion dream. These were not fantasies scribbled on napkins. They
Speaker 1: were disciplined engineering studies by serious people, and even they,
Speaker 1: at 12% of light speed, described a decades-long, one-way, uncrewed
Speaker 1: flyby that would tear past its target in a matter
Speaker 1: of hours after cruising for half a century. No human aboard.
Speaker 1: No stopping. And the fuel requirements strained credibility vast quantities
Speaker 1: of a rare form of helium that we would essentially
Speaker 1: have to mine from the atmospheres of the giant planets.
Speaker 1: Because Earth does not hold nearly enough. That is the
Speaker 1: optimistic end of the ladder. That is the concept that
Speaker 1: works best on paper. And I must be precise, as
Speaker 1: this whole story demands, fusion propulsion of this kind has
Speaker 1: never been built, never been flown, and never been demonstrated.
Speaker 1: It is a proposed technology, not a proven one. Climb
Speaker 1: higher and you reach the boldest real proposal of our
Speaker 1: own era, and the one that came closest to a plan,
Speaker 1: Breakthrough Starshot. Its logic was to abandon the heavy ship entirely.
Speaker 1: Do not carry fuel at all, leave the engine on
Speaker 1: the ground. build a colossal array of ground-based lasers with
Speaker 1: a combined power of around 100 gigawatts, and aim it
Speaker 1: at a swarm of tiny, gram-scale probes, each trailing a delicate,
Speaker 1: reflective sail no heavier than a sheet of paper. For
Speaker 1: a few blazing minutes, the lasers would pour their light
Speaker 1: onto those sails, and the sheer pressure of that light
Speaker 1: would drive the little craft up to about 20% of
Speaker 1: the speed of light fast enough. In principle, to reach
Speaker 1: the nearest star in roughly 20 years rather than 70,000.
Speaker 1: It was audacious, and it was taken seriously by serious scientists.
Speaker 1: And it is, as of the middle of this decade,
Speaker 1: effectively shelved a program that quietly ran aground on its
Speaker 1: own staggering difficulties and funding, even as the underlying idea
Speaker 1: lives on in newer research. The concept endures, the schedule evaporated,
Speaker 1: and note what even the full dream promised, not a
Speaker 1: crude vessel. but a fleet of chips lighter than a coin,
Speaker 1: precisely because the energy wall makes anything heavier impossibly expensive
Speaker 1: to accelerate. To move people, you would need to scale
Speaker 1: that 100 gigawatt laser up by factors that leave the
Speaker 1: realm of engineering for the realm of pure speculation. At
Speaker 1: the very top of the ladder sits the most concentrated
Speaker 1: fuel physics permits at all, antimatter. When matter meets antimatter,
Speaker 1: both are annihilated completely. their entire mass converted into energy
Speaker 1: with a totality no other reaction approaches. Pound for pound,
Speaker 1: the most potent fuel the universe allows. On paper, a
Speaker 1: handful of it could drive a ship to relativistic speed.
Speaker 1: In reality, humanity has produced only the faintest whisper of antimatter,
Speaker 1: a few billionths of a gram in total, assembled atom
Speaker 1: by agonising atom in enormous particle accelerators at a cost
Speaker 1: that makes it, gram for gram, almost incomprehensibly the most
Speaker 1: expensive substance ever made. We cannot manufacture it in useful amounts.
Speaker 1: We cannot store it, because it destroys any ordinary container
Speaker 1: the instant it touches one. An antimatter starship is not
Speaker 1: a blueprint. It is a hope wearing the costume of
Speaker 1: a blueprint. And honesty requires me to label it exactly
Speaker 1: that highly speculative, resting on capabilities we do not possess
Speaker 1: and have no near path toward. And notice what we
Speaker 1: have not invoked anywhere on this ladder. There is no
Speaker 1: warp drive here, no wormhole, no faster-than-light shortcut folding the
Speaker 1: distance out of existence. Those belong to fiction, not to physics,
Speaker 1: and physics is the only thing this ship has to
Speaker 1: sail on. So the energy wall alone would be enough
Speaker 1: to stop us. But suppose we granted ourselves the energy
Speaker 1: for free. Imagine some benevolent miracle handed us the power
Speaker 1: to push a ship to a fifth of the speed
Speaker 1: of light at no cost. we would immediately collide with
Speaker 1: the second item on the invoice, and it is one
Speaker 1: almost nobody sees coming. At relativistic speed, empty space stops
Speaker 1: being empty. The gulf between the stars is not a
Speaker 1: perfect vacuum. It is thinly haunted by scattered atoms of
Speaker 1: hydrogen and by rare drifting grains of dust, so sparse
Speaker 1: that on the scale of a laboratory, you would call
Speaker 1: it the finest vacuum imaginable. At walking pace, at flying pace,
Speaker 1: even at voyager's pace, This thin haze is utterly harmless.
Speaker 1: You would never notice it. But energy, remember, grows with
Speaker 1: the square of speed. And that law does not only
Speaker 1: govern your ship, it governs everything your ship runs into.
Speaker 1: Race through that haze at a fifth of the speed
Speaker 1: of light, and the arithmetic turns lethal. Every single hydrogen
Speaker 1: atom you strike is no longer a harmless speck. It
Speaker 1: slams into the hull carrying the energy of the collision.
Speaker 1: And at these velocities, a steady rain of individual atoms
Speaker 1: becomes a continuous blast of radiation and erosion. sandblasting the
Speaker 1: leading face of the craft microscopically but relentlessly across four
Speaker 1: light-years of travel, and the atoms are the gentle part.
Speaker 1: Every so often, rarely, but inevitably over such a distance,
Speaker 1: the ship meets not an atom but a grain of dust,
Speaker 1: a moat so small you could lose it in a fingerprint,
Speaker 1: at a fifth of light-speed, that invisible moat arrives carrying
Speaker 1: the punch of a bullet, and a slightly larger one
Speaker 1: the punch of a small explosion, striking a hull that
Speaker 1: has no time whatsoever to react. This is not a
Speaker 1: hypothetical worry dreamed up to be dramatic. It is precisely
Speaker 1: why Breakthrough Starshot planned to send not one probe, but
Speaker 1: a swarm of a thousand, a grim admission that many
Speaker 1: would simply be shredded en route, and the mission would
Speaker 1: succeed only if enough survived the crossing. To move fast
Speaker 1: enough to save a human life is to turn the emptiest,
Speaker 1: gentlest medium in existence into a shooting gallery, and to
Speaker 1: spend the entire journey being fired upon by the vacuum itself.
Speaker 1: And erosion is only the visible half of what that
Speaker 1: headwind does. At a fifth of the speed of light,
Speaker 1: the hydrogen atoms the ship ploughs through do not merely
Speaker 1: scrape the hull, each one arrives carrying so much energy
Speaker 1: that the oncoming wind behaves less like dust and more
Speaker 1: like a sleet of hard radiation. a stream of particles
Speaker 1: energetic enough to bore straight through ordinary metal and into
Speaker 1: whatever lies. Behind it, blocking the sandblast is one thing.
Speaker 1: Blocking a penetrating radiation bath that pours in relentlessly for
Speaker 1: the entire crossing is another problem altogether. And a far
Speaker 1: heavier one, because the shielding that could stop it is
Speaker 1: itself dead weight, that must be dragged up to a
Speaker 1: fifth of light speed at the same ruinous cost as
Speaker 1: everything else. Speed does not just scratch the ship, it
Speaker 1: irradiates it. And there is a matching cruelty pointing the
Speaker 1: other way. A working starship, its reactor, its engines. The
Speaker 1: warmth of whatever lives inside it pours out heat constantly,
Speaker 1: and that heat has to go somewhere. On Earth, we
Speaker 1: shed warmth into the air and the ground without a thought.
Speaker 1: Space offers no such mercy. A near-perfect vacuum is a
Speaker 1: near-perfect insulator. It carries almost nothing away by contact, and
Speaker 1: a ship can rid itself of heat only slowly, by
Speaker 1: radiating it away into the dark. run a powerful engine
Speaker 1: inside that insulating emptiness, and the vessel faces the strange
Speaker 1: danger of cooking itself from the inside, even as the
Speaker 1: interstellar wind blasts it from the front, scorched within and
Speaker 1: irradiated without, at one and the same time. And the
Speaker 1: trap tightens on itself, as every trap in this story does.
Speaker 1: The faster you fly to shorten the crossing, the fiercer
Speaker 1: the radiation you drive into the hull. and the more
Speaker 1: heat your straining engine dumps into a void that will
Speaker 1: not take it. So the very speed you bought to
Speaker 1: save time demands still more shielding and still more cooling,
Speaker 1: still more weight, hauled up the same merciless curve. This, too,
Speaker 1: is not speculation but plain physics, one more line on
Speaker 1: an invoice that only ever grows. Grant us shielding, then,
Speaker 1: to armour the ship somehow against the sandblast and the
Speaker 1: sparse bullets of the dark. We arrive at the third item.
Speaker 1: quieter than the others, but no less unforgiving. The problem
Speaker 1: of aim. We speak of pointing a ship at Alpha
Speaker 1: Centauri as though the star were a fixed lamp hanging
Speaker 1: on a wall, waiting patiently for us to arrive. It
Speaker 1: is nothing of the kind. Alpha Centauri is moving, drifting
Speaker 1: across the sky, orbiting the galaxy on its own path, and,
Speaker 1: being three stars locked in a slow gravitational dance, shifting
Speaker 1: its internal arrangement year by year, as Proxima and the
Speaker 1: sun-like pairwheel about one another, you are not throwing a
Speaker 1: dart at a bullseye. You are throwing a dart across
Speaker 1: a distance so vast that light itself needs four years
Speaker 1: to cross it, at a bullseye that is itself gliding
Speaker 1: sideways the entire time, and you must aim not at
Speaker 1: where it is, but at where it will be decades
Speaker 1: from now, when your ship finally arrives. Over four light years,
Speaker 1: an error in your initial aim of the tiniest fraction
Speaker 1: of a degree does not put you slightly off target.
Speaker 1: It puts you wide of the entire system by distances
Speaker 1: larger than our whole solar system, sailing forever past into
Speaker 1: the empty dark with no fuel left to correct and
Speaker 1: no one to call for help. And when your probe
Speaker 1: does arrive, if it arrives, it must find and photograph
Speaker 1: a specific tiny world tucked close beside a blinding star,
Speaker 1: then turn and send that data home across four-plus light-years
Speaker 1: a signal so faint after crossing that gulf that catching
Speaker 1: it at all is a feat unto itself. The precision
Speaker 1: required is not the precision of a marksman. It is
Speaker 1: the precision of threading a needle you cannot see on
Speaker 1: a table on the other side of a continent while
Speaker 1: both you and the needle are moving. And now we
Speaker 1: reach the item on the invoice that almost no one
Speaker 1: ever mentions, the one that quietly undoes everything else, the
Speaker 1: problem of stopping. Look again, very carefully, at what even
Speaker 1: our boldest concept actually promised. Breakthrough Starshot was never a
Speaker 1: mission to visit the nearest star. It was a mission
Speaker 1: to fly past it. Those gram-scale probes, having spent 20
Speaker 1: years crossing the dark, would blaze through the entire Alpha
Speaker 1: Centauri system in a matter of hours, snatching whatever images
Speaker 1: and measurements they could grab in that brief, screaming pass,
Speaker 1: and then hurtle out the far side, never to slow,
Speaker 1: never to return, tumbling on into the galaxy forever. They
Speaker 1: could not stop. and this was not an oversight. It
Speaker 1: was a confession written into the design, because stopping is,
Speaker 1: if anything, harder than starting. Here is why breaking is
Speaker 1: the hidden monster. Every joule of energy you poured into
Speaker 1: accelerating your ship up to a fifth of the speed
Speaker 1: of light is still there when you arrive, locked into
Speaker 1: the ship's motion, and to stop you must get rid
Speaker 1: of all of it. Slowing down is not coasting to
Speaker 1: a gentle halt. It is the entire violent, ruinous work
Speaker 1: of acceleration performed a second time in reverse which means
Speaker 1: at minimum you must double the already civilization crushing energy
Speaker 1: budget we started with pay the whole staggering bill twice
Speaker 1: over but it is worse than merely double because of
Speaker 1: where the two payments come due when you launched you
Speaker 1: had a whole planet behind you laser arrays anchored to
Speaker 1: the ground fuel depots the full industrial might of earth
Speaker 1: to fling you forward when you arrive you have none
Speaker 1: of that There is no laser array waiting at Alpha
Speaker 1: Centauri to catch you. There is no fuel station orbiting Proxima.
Speaker 1: Whatever you need to shed a fifth of the speed
Speaker 1: of light, you must have carried with you the entire
Speaker 1: way which makes the ship heavier, which makes it cost
Speaker 1: vastly more to accelerate in the first place, which drives
Speaker 1: the launch energy back up the squaring curve all over again,
Speaker 1: each demand feeding the next without end. Every serious idea
Speaker 1: for solving this unfurling a vast magnetic sail to drag
Speaker 1: against the thin interstellar gas, or skimming the target star's
Speaker 1: own light and gravity to bleed off speed, remains firmly
Speaker 1: in the realm of the speculative, untested and unbuilt. And
Speaker 1: so we arrive at the sentence that captures the entire
Speaker 1: absurd predicament. We can, just possibly, imagine throwing something at
Speaker 1: the nearest star. We have no idea how to make
Speaker 1: it stop there. And even if we solved all of it,
Speaker 1: the energy, the shielding, The aim, the breaking there remains
Speaker 1: a final mundane grinding demand that the vacuum imposes for free.
Speaker 1: The ship has to keep working the entire way. A
Speaker 1: voyage to the nearest star at survivable speed is a
Speaker 1: journey of decades at the very least, and every hour
Speaker 1: of it unfolds in an environment that is actively hostile
Speaker 1: to machines swept by cosmic rays, starved of power and warmth,
Speaker 1: and utterly, absolutely beyond the reach of repair. There is
Speaker 1: no rescue crew, There is no replacement part. There is
Speaker 1: no engineer who can be sent out to fix a
Speaker 1: failed component four light years from the nearest workshop. We
Speaker 1: have exactly one machine that has run continuously in deep
Speaker 1: space for a comparable stretch of time, and it is
Speaker 1: instructive precisely because it is our champion. Voyager 1, flying
Speaker 1: since 1977, is a marvel, and it is also a
Speaker 1: slowly dying one. Its instruments switched off one by one
Speaker 1: to conserve a fading trickle of power. Its systems failing
Speaker 1: gradually as the decades grind on, kept alive only by
Speaker 1: engineers reaching across the void with clever fixes because it
Speaker 1: still hangs close enough to hear us. A relativistic starship
Speaker 1: would have no such lifeline. It would need to run
Speaker 1: for decades with near-perfect reliability, entirely alone, with every critical
Speaker 1: system either flawless or fatally redundant. Because the first uncorrectable
Speaker 1: failure is the end of the mission. And, if there
Speaker 1: is a crew, the end of them. We struggle to
Speaker 1: build a car that runs untended for 30 years on
Speaker 1: a driveway. This is a demand of a different order entirely.
Speaker 1: And now, before we tally the whole bill, there is
Speaker 1: one genuinely strange twist to add the single item on
Speaker 1: this list that does not punish the traveller, but favours them.
Speaker 1: So far, speed has only cost us. Energy, shielding, aim, reliability...
Speaker 1: all of it climbing against us. But at a real
Speaker 1: fraction of the speed of light, one of the deepest
Speaker 1: facts in all of physics quietly comes into play, and
Speaker 1: for once it works in the crew's favour. Time itself
Speaker 1: does not flow at the same rate for a fast-moving
Speaker 1: traveller as it does for the world left behind. This
Speaker 1: is not a metaphor, and it is not speculation. It
Speaker 1: is measured. confirmed physics, tested countless times in particles that
Speaker 1: live measurably longer when hurled through accelerators near light speed
Speaker 1: and in atomic clocks flown aboard aircraft that land a
Speaker 1: whisker out of step with the clocks left on the ground.
Speaker 1: Move fast enough and your own clock, your own heartbeat,
Speaker 1: your own ageing all runs slightly slow compared to everyone
Speaker 1: standing still. For a starship, this means the crew would
Speaker 1: age less than the years the journey takes as measured
Speaker 1: from Earth. And that sounds, at first, like the escape
Speaker 1: hatch we have been hunting for all along, a way
Speaker 1: to cheat the crushing travel times, to let a crew
Speaker 1: step across the dark while barely ageing at all. But honesty,
Speaker 1: as ever, demands the precise number, and the precise number
Speaker 1: is deflating. The effect only turns powerful when you get genuinely,
Speaker 1: ferociously close to the speed of light within a whisker
Speaker 1: of it. At the sort of speeds our boldest concepts
Speaker 1: actually reach, a fifth of light speed or so, the
Speaker 1: mercy it grants is real but modest. The crew would
Speaker 1: age only about 2% less than Earth does over the crossing.
Speaker 1: On a 20-year journey, that is a saving of a
Speaker 1: few months. Worth having, certainly, but nowhere near enough to
Speaker 1: turn an impossible voyage into a comfortable one. There is
Speaker 1: a further wrinkle folded inside it, one that quietly foreshadows
Speaker 1: trouble we will meet later. Because the crew's clock runs slow,
Speaker 1: a fast traveller would arrive to find that the destination
Speaker 1: and the home they left had aged very slightly more
Speaker 1: than they had. The two ends of the journey would
Speaker 1: not merely be far apart in space. They would fall
Speaker 1: a touch out of step in time itself, the movers
Speaker 1: ageing a little less than the still. At a fifth
Speaker 1: of light speed it is only a whisper of a difference.
Speaker 1: But it is a real one. and it hints that
Speaker 1: speed does not only stretch the distance between two worlds,
Speaker 1: it can, ever so slightly, pull their very clocks apart.
Speaker 1: To make time dilation truly dramatic to shrink a decades-long
Speaker 1: crossing into a handful of years felt aboard the ship,
Speaker 1: you would have to travel at 90%, 99%, 99.9% of
Speaker 1: the speed of light. And here the twist folds straight
Speaker 1: back into the trap we already know, because those velocities
Speaker 1: sit at the very steepest part of the energy curve,
Speaker 1: where the cost of each additional sliver of speed rockets
Speaker 1: toward the impossible. The faster you go, the more time
Speaker 1: dilation would help you and the more absurdly ruinously unaffordable
Speaker 1: that speed becomes. The universe offers the mercy and prices
Speaker 1: it out of reach in the very same breath. So
Speaker 1: even this, the one law of physics that seemed to
Speaker 1: be on the traveller's side, ends up deepening the same lesson.
Speaker 1: The distance does not bend for us. Not even time
Speaker 1: bends far enough to save us unless we can pay
Speaker 1: a price that only climbs the harder we ask. So
Speaker 1: lay the whole invoice out on the table and read
Speaker 1: the total. To bring the nearest star within a human lifetime,
Speaker 1: you must reach a fraction of the speed of light.
Speaker 1: To reach a fraction of the speed of light, you
Speaker 1: must pour in energy that dwarfs the output of all
Speaker 1: human civilization and pay it a second time to stop.
Speaker 1: You must armour a ship against a vacuum that turns
Speaker 1: lethal the very moment you move fast enough through it.
Speaker 1: You must aim... across four light years, at a moving
Speaker 1: three-star target, with a precision that punishes the slightest error
Speaker 1: with eternal exile in the dark. And you must build
Speaker 1: a machine that runs flawlessly, unrepaired, alone, for decades, in
Speaker 1: the most hostile environment that exists. Not one of these
Speaker 1: is solved. Several may not be solvable at all. This
Speaker 1: is why the nearest star, for all our dreaming, has
Speaker 1: no departure date not because we lack the will, but
Speaker 1: because the universe has priced the ticket beyond anything a
Speaker 1: single world can pay. And yet suppose, suppose some future humanity,
Speaker 1: richer and cleverer and more patient than we can easily imagine,
Speaker 1: somehow paid every line of this impossible bill. Suppose they
Speaker 1: mustered the energy, survived the sandblast, threaded the needle across
Speaker 1: four light years, and most miraculous of all actually stopped,
Speaker 1: sliding a living ship into orbit around a world circling
Speaker 1: the nearest star. Suppose they crossed the horrifying distance and won.
Speaker 1: You might think that would be the end of the
Speaker 1: story that arrival, so dearly bought, would finally close the
Speaker 1: gap and lay the whole nightmare to rest. It would not,
Speaker 1: because the distance to Alpha Centauri does not disappear the
Speaker 1: moment you arrive at Alpha Centauri. It changes into something else,
Speaker 1: something quieter, and in its own way far worse, and
Speaker 1: the travellers who crossed all those light years would discover,
Speaker 1: in their first hours at journey's end, that the gulf
Speaker 1: they thought they had defeated was still stretched out behind them, unbroken, permanent,
Speaker 1: and about to reshape every message, every decision, and every
Speaker 1: human life on both of its shores. That is the
Speaker 1: discovery waiting on the far side. That is where we
Speaker 1: go last. Let us give them the miracle. After everything
Speaker 1: after the energy that dwarfed civilization, the sandblasting vacuum they
Speaker 1: somehow survived, the needle threaded across four light years, the
Speaker 1: impossible arithmetic of stopping, Let us simply grant that some
Speaker 1: future humanity paid the whole bill and won. Picture the moment.
Speaker 1: A ship, launched generations ago from a blue world circling
Speaker 1: a yellow star, slides at last into a slow orbit
Speaker 1: around a planet at the nearest star. The engines that
Speaker 1: fought so long to shed the ship's terrible speed fall silent.
Speaker 1: Through the windows, a new sun hangs in the black,
Speaker 1: perhaps the warm, familiar gold of Alpha Centauri A. So,
Speaker 1: like the star their ancestors left, that it aches to
Speaker 1: look at. Below them turns a world no human eye
Speaker 1: has ever seen up close. They have done it. They
Speaker 1: have crossed the horrifying distance. Every calculation in every part
Speaker 1: of this story said it could not reasonably be done,
Speaker 1: and they did it anyway. Surely, now, the nightmare is over.
Speaker 1: Surely the distance so dearly bought is finally behind them.
Speaker 1: It is not, and the travellers learn this in their
Speaker 1: very first hours. When someone aboard does the most natural
Speaker 1: thing imaginable, they send word home. We made it. We
Speaker 1: are here. We are alive. They point their transmitter back
Speaker 1: the way they came, toward a pale dot lost in
Speaker 1: the dark, and they let the message fly at the
Speaker 1: fastest speed the universe allows, the speed of light, the
Speaker 1: same speed that governs every radio wave and every laser pulse,
Speaker 1: and every conceivable signal that will ever exist. And in
Speaker 1: that instant, as the message leaves, the true nature of
Speaker 1: the distance reveals itself. Because that triumphant word we are
Speaker 1: here will not reach Earth today, it will not reach
Speaker 1: Earth this year. It will cross the same four and
Speaker 1: a quarter light years the ship crossed, at light speed,
Speaker 1: and it will arrive at Earth more than four years
Speaker 1: after it was sent. The people who launch this mission
Speaker 1: will wait over four years, staring at empty sky, before
Speaker 1: they learn it succeeded. And the crew, having sent it,
Speaker 1: will wait more than eight years, four for the message
Speaker 1: to arrive, four for any reply to return before they
Speaker 1: hear a single human voice answer back. This is the
Speaker 1: discovery waiting on the far side of the miracle, and
Speaker 1: it is the cruelest turn in the whole story. The
Speaker 1: distance to Alpha Centauri does not end when you arrive
Speaker 1: at Alpha Centauri. It simply stops being a wall you
Speaker 1: cross and becomes a delay you can never close. You
Speaker 1: can conquer the space, pour in the energy, survive the crossing,
Speaker 1: Stop the ship, but there is a second distance hidden
Speaker 1: inside the first, made of pure time, and that one
Speaker 1: is immune to every trick you used on the first.
Speaker 1: No better engine touches it. No bolder ship shortens it.
Speaker 1: Faster rockets, larger antennas, cleverer transmitters, none of it matters
Speaker 1: in the slightest, because the message is already moving at
Speaker 1: the only speed there is, the absolute cosmic limit, and
Speaker 1: even that is not remotely fast enough. Four light years, remember,
Speaker 1: is a measure of distance. but it is also, unavoidably,
Speaker 1: a measure of the minimum time any word must spend
Speaker 1: in flight. The star's light you might glimpse tonight left
Speaker 1: it four years ago, and every message you ever send there,
Speaker 1: or receive from there, inherits that same four-year exile. The
Speaker 1: gap is not behind the travellers. It is around them, permanently,
Speaker 1: woven into every attempt they will ever make to speak
Speaker 1: to the world that made them. Let us be exact
Speaker 1: about the shape of this delay. because precision is what
Speaker 1: makes it real rather than merely poetic. A message from
Speaker 1: a settlement at Proxima Centauri to Earth takes more than
Speaker 1: four years to arrive. Call it four and a quarter years.
Speaker 1: One way. If those on Earth immediately compose a reply
Speaker 1: the very instant they receive it, that reply takes another
Speaker 1: four and a quarter years to return. So the fastest
Speaker 1: possible round trip a question asked and an answer received
Speaker 1: is roughly eight and a half years, and that is
Speaker 1: before a single human being has spent one second actually
Speaker 1: thinking about how to respond. Add the ordinary human time
Speaker 1: it takes to read, consider, discuss and decide, and a
Speaker 1: simple exchange, what should we do? Answered by, here is
Speaker 1: what you should do realistically, consumes nine years or more
Speaker 1: from asking to knowing. Nine years. That is the tempo
Speaker 1: of every conversation these two branches of humanity will ever have.
Speaker 1: Not a delay you wait out impatiently, the way you
Speaker 1: might wait for a slow reply, a delay longer than
Speaker 1: a childhood. A delay in which a person could ask
Speaker 1: a question, grow measurably older, and still be waiting when
Speaker 1: the answer finally arrives. Now watch what that single fact
Speaker 1: does as it spreads outward through every part of the
Speaker 1: settlers' lives, because it does not stay politely confined to
Speaker 1: the radio room. It reaches into everything. Consider, first, the
Speaker 1: simplest and most brutal case, an emergency. Something goes wrong
Speaker 1: at the settlement, a failure in the machinery that keeps
Speaker 1: them breathing, an illness no one aboard knows how to treat,
Speaker 1: a disaster no plan anticipated. On Earth, in any crisis,
Speaker 1: there is always somewhere. someone to call that instinct is
Speaker 1: so deep in us we forget it is a luxury
Speaker 1: of proximity at alpha centauri the settlers can call of
Speaker 1: course they can they can broadcast their emergency toward earth
Speaker 1: at the speed of light a desperate plea flung across
Speaker 1: the dark and that plea will arrive on earth more
Speaker 1: than four years after the crisis began earth's finest experts
Speaker 1: can gather work the problem and transmit back everything they
Speaker 1: know and their answer will arrive at alpha centauri more
Speaker 1: than four years after that By the time any help,
Speaker 1: any advice, any word of comfort from home reaches the settlers,
Speaker 1: more than eight years will have passed. Whatever the emergency was,
Speaker 1: it will have long since resolved itself, one way or
Speaker 1: the other. The people who needed rescuing will have either
Speaker 1: saved themselves without Earth, or they will be dead, and
Speaker 1: Earth will not even learn which for years, and will
Speaker 1: send its useless, loving advice into a silence that has
Speaker 1: already decided everything. Sit with the full weight of that.
Speaker 1: because it strips away the last comfort we secretly carry
Speaker 1: about exploration. Every previous frontier in human history, however remote,
Speaker 1: kept one thin thread back to the rest of us.
Speaker 1: A thread of rescue, resupply, reinforcement, or at the very
Speaker 1: least the knowledge that help was coming, even if slowly.
Speaker 1: A ship lost at sea might still be found. A
Speaker 1: base at the pole might still be reached. An astronaut
Speaker 1: in orbit is, at most, a few days, and a
Speaker 1: phone call from home. Alpha Centauri severs that thread completely
Speaker 1: and forever. There is no rescue that can arrive in
Speaker 1: time because the very news of the trouble cannot arrive
Speaker 1: in time. There is no resupply because a supply ship
Speaker 1: would itself take decades to cross the gulf. There is
Speaker 1: no reinforcement, no evacuation, no last-minute intervention from the world
Speaker 1: that sent them. The settlers are, in the most total
Speaker 1: sense the word has ever carried, alone, not lonely, which
Speaker 1: is a feeling, but alone, which is a fact of physics.
Speaker 1: Whatever befalls them befalls them without help. Earth can only
Speaker 1: ever be a witness to their emergencies, and a witness
Speaker 1: arriving four years late watching a fire it cannot possibly
Speaker 1: put out. And it is not only help that cannot arrive,
Speaker 1: nothing physical can. It is worth separating two things we
Speaker 1: usually lump together, because the gulf treats them very differently. Information,
Speaker 1: a message, an image, a warning, a design can at
Speaker 1: least cross the distance, even if it takes more than
Speaker 1: four years to do it, because information can ride on
Speaker 1: light itself, but matter cannot ride on light. Any physical object,
Speaker 1: a spare part, a medicine, a tool, a single sack
Speaker 1: of grain, would have to be flung across the same
Speaker 1: impossible gulf as the original ship, at the same ruinous cost,
Speaker 1: over the same span of decades. In practical terms, This
Speaker 1: means that once the settlement is founded, no cargo will
Speaker 1: ever again travel between the two worlds. Not once, not ever.
Speaker 1: There will be no trade, no imports, no shipments, no
Speaker 1: resupply of any physical thing across that distance, for as
Speaker 1: long as both worlds exist. Pause on how total that is,
Speaker 1: because nothing in human history prepares us for it. Every
Speaker 1: society we have ever built has leaned on others for
Speaker 1: its stuff. No city feeds itself. No nation mines and
Speaker 1: grows and manufactures every single thing its people touch. Our
Speaker 1: entire civilization is a vast web of exchange. This land
Speaker 1: grows the food, that one pumps the fuel, another forges
Speaker 1: the metal, a fourth builds the machines, and goods flow
Speaker 1: endlessly along the threads of that web, so that no
Speaker 1: one place ever has to make everything. A settlement at
Speaker 1: Alpha Centauri would be cut out of that web completely
Speaker 1: and permanently. It could receive knowledge from Earth instructions, discoveries,
Speaker 1: the design for a new machine, all beamed across as
Speaker 1: patient light, but it could never receive the machine itself.
Speaker 1: If the settlers wanted the thing, they would have to
Speaker 1: build it from scratch, out of whatever raw materials their
Speaker 1: own world happened to provide, using only the tools they
Speaker 1: had already made from the tools before those. Consider something
Speaker 1: as ordinary as a broken part in a life support system,
Speaker 1: the same kind of failure that, on Earth, a technician
Speaker 1: fixes in an afternoon with a replacement pulled off a shelf.
Speaker 1: At the settlement there is no shelf, and no factory
Speaker 1: across town, and no supplier a call away. If the
Speaker 1: settlers did not already carry a spare, or the machine
Speaker 1: to make a spare, or the machine to make that machine,
Speaker 1: then the broken part simply cannot be replaced, not slowly,
Speaker 1: not expensively, not ever, because the nearest place that could
Speaker 1: supply it is four and a quarter light years away,
Speaker 1: and no supply run can cross that gap in any
Speaker 1: human timescale. Every settlement in human history could, in the
Speaker 1: last resort, send home for what it lacked and wait
Speaker 1: for the wagons or the ships. This one could send
Speaker 1: home and wait and wait and no ship would ever come.
Speaker 1: The waiting would simply be the rest of time. This
Speaker 1: forces a completeness of self-sufficiency no human community has ever
Speaker 1: come close to achieving. The settlement would have to be
Speaker 1: its own farm and its own foundry, its own mine
Speaker 1: and its own laboratory, its own factory for everything from
Speaker 1: the largest reactor to the smallest screw. Every element its
Speaker 1: civilisation required, it would have to locate and extract locally,
Speaker 1: because not one atom would ever be shipped in from home.
Speaker 1: Every craft, every industry, every specialised skill that Earth's billions
Speaker 1: casually divide among themselves would have to be held. On Earth,
Speaker 1: if a single factory in a single country stops making
Speaker 1: some vital component, the rest of the world can, with effort,
Speaker 1: supply it. At Alpha Centauri, there is no rest of
Speaker 1: the world. There is only the settlement, and whatever the
Speaker 1: settlement cannot make, it will simply never have. So the
Speaker 1: isolation runs deeper even than the absence of rescue. It
Speaker 1: is the absence of the entire material lifeline every human
Speaker 1: society has always taken for granted. Earth can send its
Speaker 1: distant children ideas across the light years, and it can
Speaker 1: send them love, and it can send them the accumulated
Speaker 1: knowledge of the whole species, but it can never again
Speaker 1: send them a single physical thing they can hold. From
Speaker 1: the moment of arrival, the settlement is not merely governing
Speaker 1: itself and defending itself. It is manufacturing its entire world, alone,
Speaker 1: out of local dirt and local ore, with no delivery
Speaker 1: ever coming and no delivery ever possible. A colony, in
Speaker 1: every prior age of human expansion, was a place you
Speaker 1: kept supplied. This would be a colony that... by the
Speaker 1: pure arithmetic of the distance, could never be supplied at all.
Speaker 1: And from that raw fact of unreachable isolation, something profound
Speaker 1: and inevitable begins to grow, something that reshapes not just
Speaker 1: how the settlers survive, but who they become. Think about
Speaker 1: what it means to run a settlement when every instruction
Speaker 1: from headquarters is more than four years out of date
Speaker 1: on arrival. Imagine Earth, in its wisdom, sending a directive,
Speaker 1: do this, build that, decide the following by the time
Speaker 1: those words cross the gulf and reach the settlement more
Speaker 1: than four years have passed the situation the directive was
Speaker 1: written for no longer exists the people it was addressed
Speaker 1: to have moved on adapted faced a hundred developments earth
Speaker 1: could not have known about because those developments had not
Speaker 1: yet happened or had happened but their news was still
Speaker 1: crawling across the dark not yet arrived every command from
Speaker 1: home describes a world that is already gone Every order
Speaker 1: answers a question that was asked more than four years
Speaker 1: ago and has long since been overtaken by events. Earth
Speaker 1: is not merely slow to respond. Earth is structurally incapable
Speaker 1: of governing anything at Alpha Centauri, because governance requires knowing
Speaker 1: the present, and the present at Alpha Centauri is something
Speaker 1: Earth can never, ever possess. It can only know the
Speaker 1: settlement's past and always, unavoidably, a past more than four
Speaker 1: years stale. So the settlers cannot wait for Earth Not
Speaker 1: because they are rebellious, not because they resent the homeworld,
Speaker 1: but because the physics leaves them no choice. To survive
Speaker 1: at all, they must decide now, with what they have,
Speaker 1: on their own authority because the alternative is to freeze
Speaker 1: for nine years awaiting permission that, when it comes, will
Speaker 1: answer a question no longer being asked. Every meaningful decision
Speaker 1: about their own lives must be made locally, immediately, by
Speaker 1: people standing in the actual present of that distant world.
Speaker 1: and a community that must make all its own decisions,
Speaker 1: that cannot in practice be governed from outside, that answers
Speaker 1: its own emergencies and charts its own course, because no
Speaker 1: other course is physically possible that community is not a
Speaker 1: colony in any ordinary sense. It is becoming something else.
Speaker 1: It is becoming independent, not by declaration, but by the
Speaker 1: simple operation of the speed of light. The distance does
Speaker 1: not merely isolate them. It quietly and inexorably transforms them
Speaker 1: into their own separate authority, their own separate society, their
Speaker 1: own separate branch of the human project, because a gulf
Speaker 1: that no message can close in less than nine years
Speaker 1: cannot hold a single civilization together across it. It can
Speaker 1: only preside over the birth of two, and here we
Speaker 1: arrive at the deepest and strangest consequence of all the
Speaker 1: one that reaches past politics and survival into the very
Speaker 1: texture of what it means to be human together it
Speaker 1: is not merely that earth and the settlement cannot govern
Speaker 1: each other or rescue each other it is that they
Speaker 1: can never share a present turn that phrase over slowly
Speaker 1: because it is the true heart of this entire story.
Speaker 1: Two people standing in the same room share a present.
Speaker 1: They experience the same moment together and can speak and
Speaker 1: answer and know one another in real time. Even two
Speaker 1: people on opposite sides of the Earth share a present.
Speaker 1: Near enough, a voice crosses the planet in a fraction
Speaker 1: of a second and a conversation flows. But Earth and
Speaker 1: Alpha Centauri can never do this. When the settlers look
Speaker 1: at the most recent message from home, they are looking
Speaker 1: at Earth's past at events more than four years old,
Speaker 1: at a world that has already moved on to a present,
Speaker 1: the settlers will not glimpse for years yet. And when
Speaker 1: Earth looks at the settlement's transmissions, it too sees only
Speaker 1: the past, a report from more than four years ago,
Speaker 1: describing a moment that, for the settlers, is already ancient history.
Speaker 1: Each side is, permanently, watching the other through a four-year
Speaker 1: window into a vanished moment. Neither can ever reach the
Speaker 1: others now, The two branches of humanity can exchange information
Speaker 1: across the gulf, endlessly and richly, but they can never
Speaker 1: occupy the same instant of time. They are severed not
Speaker 1: in space alone, but in the present itself. Consider what
Speaker 1: that does to something as human as a conversation, and
Speaker 1: the loss becomes almost unbearably intimate. A conversation, as we
Speaker 1: have always known it, is a living thing, a back
Speaker 1: and forth, a call and an answer, two minds meeting
Speaker 1: in real time, and building something together in the moment.
Speaker 1: Between Earth and Alpha Centauri, that is simply gone, replaced
Speaker 1: by something that only wears the costume of dialogue. You
Speaker 1: send a thought into the dark, and then you wait
Speaker 1: not minutes, not hours, but years for a reply. And
Speaker 1: when the reply finally comes, you have changed. You are older.
Speaker 1: Your circumstances have shifted. The version of you that asked
Speaker 1: the question may barely resemble the version that receives the answer.
Speaker 1: A message might arrive from Earth addressed with warmth and
Speaker 1: urgency to a settler who, in the four-plus years the
Speaker 1: message spent crossing the void, has grown old, or moved away,
Speaker 1: or died, so that a living voice from home speaks
Speaker 1: tenderly to someone who is no longer there to hear it.
Speaker 1: Letters would routinely outlive the moods that wrote them, the
Speaker 1: crises that prompted them, sometimes the very people who sent them.
Speaker 1: Every exchange between the two worlds would be a kind
Speaker 1: of correspondence with the past. a series of messages in
Speaker 1: bottles cast into a four-year sea, each one describing a
Speaker 1: world that no longer exists by the time it washes ashore.
Speaker 1: This is not communication as any human being has ever
Speaker 1: known it. It is two civilizations writing history at each other,
Speaker 1: forever out of step, forever describing moments already gone. And so,
Speaker 1: across years and then decades and then centuries of this,
Speaker 1: the two branches of humanity would inevitably drift not through
Speaker 1: any quarrel, not through any decision, but through the sheer
Speaker 1: impossibility of staying synchronized across a nine-year gulf. Think of
Speaker 1: how quickly a shared human world diverges even over short separations.
Speaker 1: Languages shift, slang mutates, customs turn, values move, until people
Speaker 1: separated for a single generation already struggle to fully understand
Speaker 1: one another. Now, stretch that separation across a gap where
Speaker 1: the fastest possible exchange of ideas is takes the better
Speaker 1: part of a decade, where no fashion, no discovery, no
Speaker 1: shift in thought can pass from one world to the
Speaker 1: other in less than the time it takes a child
Speaker 1: to grow. The settlement would develop its own words for
Speaker 1: the new things it encountered, its own stories about its
Speaker 1: own sky, its own way of being human, shaped by
Speaker 1: a world with a different sun and a different past.
Speaker 1: Earth would move on to concerns the settlers could not
Speaker 1: follow in real time and would only ever learn about
Speaker 1: years too late to join. The two would remain kin-bound
Speaker 1: by shared origin, exchanging their patient, delayed messages across the dark,
Speaker 1: but they would grow into genuinely separate peoples, two human
Speaker 1: civilisations developing side by side on opposite shores of a
Speaker 1: gulf that no amount of goodwill could ever bridge. Not
Speaker 1: one humanity spread across two stars, two humanities, related and estranged,
Speaker 1: speaking to each other's ghosts. This, at last, is the
Speaker 1: full and horrifying meaning of the distance to Alpha Centauri,
Speaker 1: and it is nothing like the meaning we began with.
Speaker 1: We started with a comforting word on a classroom poster nearest,
Speaker 1: and we have watched it transform, stage by stage, into
Speaker 1: something monstrous. First we saw that nearest hid a gulf
Speaker 1: so vast our fastest spacecraft had crossed barely a fraction
Speaker 1: of a fraction of it. Then we saw that even
Speaker 1: the greatest speeds humanity has achieved would spend 70,000 years
Speaker 1: on the crossing, and that only a fraction of light
Speaker 1: speed could bring it within a single life. Then we
Speaker 1: saw the ruinous price of that speed, the energy, the shielding,
Speaker 1: the aim, the impossible arithmetic of stopping a bill so steep.
Speaker 1: The journey has no departure date and perhaps never will.
Speaker 1: And now, having imagined paying every impossible cost and winning
Speaker 1: the crossing anyway, we find the final cruelty waiting at
Speaker 1: the end. That arrival does not conquer the distance at all.
Speaker 1: It only converts the distance from a barrier of space
Speaker 1: into a barrier of time, and that barrier, made of
Speaker 1: the delay that light itself cannot outrun, is one we
Speaker 1: have no power whatsoever to break, because here is the
Speaker 1: thing that ordinary intuition, right to the very end, refuses
Speaker 1: to accept. We imagine the distance as a thing you
Speaker 1: cross once, a hard, heroic, one-time act, after which the
Speaker 1: crossing is done and the two worlds are joined. But
Speaker 1: the distance to Alpha Centauri is not something you cross
Speaker 1: once and finish with. It is something that continues, without pause,
Speaker 1: for as long as there are people on both sides
Speaker 1: of it. It sits inside every message, adding its four-year toll.
Speaker 1: It sits inside every emergency, ensuring that help can only
Speaker 1: ever arrive too late. It sits inside every decision, forcing
Speaker 1: each world to act alone in a present the other
Speaker 1: can never reach. It sits inside every relationship stretched across
Speaker 1: the gulf, turning every conversation into correspondence with the past.
Speaker 1: The travellers who reached Alpha Centauri would not have left
Speaker 1: the distance behind them at Earth. They would have carried
Speaker 1: it with them, and it would go on shaping every
Speaker 1: hour of their lives and their descendants' lives, and every
Speaker 1: hour of the lives of everyone back home who ever
Speaker 1: thought of them a permanent, silent third presence in the
Speaker 1: affairs of two worlds. long after the ship that made
Speaker 1: the crossing had rusted into memory. And so we arrive
Speaker 1: at the truth. This whole journey has been circling. Not
Speaker 1: a soft platitude that space is big, and not the
Speaker 1: false comfort that some future engine will someday make the
Speaker 1: gap trivial, because the gap that matters most is made
Speaker 1: of time, and no engine touches it. It leaves us
Speaker 1: with something far stranger and far more sobering. Suppose humanity
Speaker 1: truly does it. Suppose we become the kind of civilization
Speaker 1: that can pour the output of a thousand worlds into
Speaker 1: a single ship, that can armor it against the shooting
Speaker 1: gallery of the vacuum, that can thread it across four
Speaker 1: light years and miracle of miracles bring it to a
Speaker 1: stop around another star. Suppose we conquer the horrifying distance
Speaker 1: in every way it can possibly be conquered. Even then,
Speaker 1: even then, we would not have conquered the separation. We
Speaker 1: would have two branches of humanity. that can send each
Speaker 1: other messages but can never share a moment, that can
Speaker 1: exchange information but can never exchange a present, that can
Speaker 1: love each other across the dark but only ever four
Speaker 1: years too late. We could master the journey to our
Speaker 1: nearest neighbouring star and still, utterly and permanently, fail to
Speaker 1: master the distance because the distance was never only the
Speaker 1: space between the stars, it was the gulf of time
Speaker 1: hidden inside that space. the four-year silence that turns every
Speaker 1: now into a memory before it can ever be shared.
Speaker 1: Cross it, and you do not join two worlds. You
Speaker 1: begin two histories, and the last, quiet horror of the
Speaker 1: nearest star is this. The moment we finally reached it
Speaker 1: would not be the moment humanity became one, people spread
Speaker 1: across the heavens. It would be the moment humanity, gently
Speaker 1: and forever, split in two.