シャドーイング練習: Why We Can Reach Pluto But Can’t Fly Above the Sun - 動画で英語スピーキングを学ぶ

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So, what exactly is above the solar system?

It seems like it should be the easiest thing in the world to find out.

Just take a rocket, point it straight up relative to the planetary plane, launch it into space, and take a look.

But no, we can't.

Or at least it's really, really, really hard to do.

Which is weird, because we've sent probes all the way to Pluto billions of kilometers away.

Yet getting above our own sun by flying straight up is, like I said, nearly impossible.

It's the point where the laws of physics look at us like we're complete maroons.

So just why is flying up, so to speak, harder than reaching the edge of the solar system,

and what exactly would we run into if we actually tried to get out there?

This whole cosmic pickle starts with the fact that the Earth isn't standing still.

Right now, you're sitting in your chair

or on your bed in your socks watching this video thinking you're in a state of absolute rest.

Yeah, that's kinda true, but not really.

At this very second,

our planet is hurtling sideways along its orbit around the Sun at a terrifying speed of 30 kilometers per second.

Per second.

To put that into perspective, that's over 100,000 kilometers per hour.

And any rocket we launch from Earth instantly inherits this insane sideways speed.

If we're flying to Mars, or Jupiter, or even Pluto, all of which orbit roughly in the same plane as Earth, at least we're already moving in the right direction.

It's a breeze.

Smooth sailing.

Okay, I exaggerate, but the Earth has already done the lion's share of the sideways motion work for us.

Yeah, we still need a big ass monster rocket, obviously, but we're accelerating mostly in the direction that we were already going, and that's it, we're on our way.

But if we want to defy the system and fly strictly perpendicular, straight up, that's where this free speed becomes our worst enemy.

Look, we don't need to completely cancel out that 30 kilometers per second and then accelerate upwards from zero.

We need to pull a different trick, redirect the velocity vector itself.

But even a perfect 90 degree turn would require about 42 kilometers per second of additional speed.

That delta V is so absurdly high that no conventional chemical rocket ever built by humanity could possibly pull it off.

And diving towards the sun isn't a magic fix either.

It only solves part of the problem.

Yes, the Oberth effect, this is the trick of firing your engines while moving extremely fast,

so the same burn produces a much larger change in orbital energy, is great for speeding up or slowing down.

But changing your orbital inclination is far more efficient when the spacecraft is moving slowly.

So engineers have to cheat.

They use the gravity of another planet to sling the spacecraft onto a new trajectory. Which planet?

We'll get to that.

But let's imagine we pulled off this gravitational trick shot and broke out of the plane.

What's up there?

First we have to cross the heliopause, the outer edge of the heliosphere.

That's the giant protective bubble the Sun blows around the entire solar system with its solar wind,

shielding us from much of that nasty barrage of galactic cosmic rays.

You can almost kind of think of it like the solar system's own gigantic atmosphere,

a vast magnetized cocoon protecting us from the rest of the galaxy.

For decades, serious guys in glasses drew this bubble like a comet with a rounded nose

and one enormous tail trailing behind it.

Which makes sense, I guess.

We're moving through the galaxy, so naturally you'd expect something streaming out behind us.

But in 2020, researchers combined data from several different space probes with computer simulations and came up with a very different possibility.

In their model, there's no ginormous comet tail.

Instead, the heliosphere looks more like a deflated croissant.

That's right, according to this model, we're flying through the cold dark galaxy inside a giant invisible croissant.

But the croissant is nothing, because beyond it lies the next great frontier, the Oort Cloud.

It isn't a solid wall,

it's unimaginably sparse, but calculations suggest that it surrounds our system as a roughly spherical shell.

So out there, in the absolute scary pitch black darkness, trillions of icy bodies could drifting around,

some the size of Mount Everest.

Any sane person would ask, wait, how do you know it's there if you've never actually seen it?

It's not like it glows.

Well, simple.

In 1950, Dutch astronomer Jan Oort, what are the odds he was studying the Oort cloud, and his name was Jan Oort.

Okay, yeah, it was named after him, obviously.

Anyway, he was studying the orbits of long-period comets, and noticed something weird.

A lot of them were coming in from mind-boggling distances, and, and this is important, from all directions at once.

That meant that what lay far beyond the planets wasn't another flat disk,

but a nearly spherical reservoir of icy chunks.

Basically a gigantic cosmic deep freeze that we haven't yet observed directly.

So yeah, that's astronomy for you.

An entire cloud and not a single picture of it.

The sheer scale of these distances is best illustrated by the legendary Voyager 2.

This guy's been cruising through the void since 1977 at 56,000 kilometers per hour.

Respect.

But just to reach the inner edge of this vast cloud, it still has another 300 years to go.

And to pass all the way through it, 30,000 years.

30,000 years.

It makes you kind of want to tell the devs of this universe, or God if you will, to bump up the travel speed a little because this is painfully slow.

And it would be fine if the Oort cloud just hung out quietly in the dark, but about 80,000 years ago,

a wandering binary system known as Schultz's star just flew by and grazed its outer edge.

Sounds like the opening scene of a Hollywood comet apocalypse, But this cosmic duo was,

thankfully, too light and too fast to send a global barrage of icy objects our way.

It probably disturbed some objects, but they'd take millions of years to reach even the inner solar system.

Basically, they came over to borrow a cup of sugar and clipped the Oort Cloud on their way out.

Now, let's leave the frozen realm of the Oort cloud behind and zoom out even farther.

Do you imagine the space around our entire system is just quiet and empty and clean?

Not a chance.

It's foggy.

Right now, the solar system is hurtling at breakneck speed through the local interstellar cloud,

a region where gas and dust are slightly denser than in the surrounding space.

By our standards, it's still virtually a perfect vacuum, but compared to the emptiness nearby, it's a thick cosmic soup.

Zoom out even more, and this little cloud becomes just a speck of dust inside a much larger structure.

Welcome to the local bubble, a colossal cosmic void, a thousand light years wide where the density of matter is obscenely low.

Imagine an exclusive VIP section of the galaxy where someone has swept out almost all of the gas.

And who exactly is this almighty cosmic janitor?

Well, all the clues point to the most violent events in the universe, supernova explosions.

Starting around 14 million years ago, this neighborhood went absolutely nuts, with roughly 15 massive stars blowing up here,

one after another, over the next several million years.

These monstrous explosions pushed the gas out and away in all directions, leaving behind a rarefied cavity with dense walls,

which is exactly what we're flying through right now.

So yeah, nice neighborhood, 15 supernovae and almost no gas.

100

But the explosions happened millions of years ago, and the bubble is completely transparent.

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You'd think there'd be zero evidence left, but the clues are sitting right under our noses, or rather, at the very bottom of our oceans.

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Scientists sampled deep sea sediments and found something called Iron 60 in them,

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a radioactive isotope primarily forged inside massive stars and then ejected into space during supernova explosions,

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or carried by intense stellar winds.

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Down on the seafloor, they discovered two major waves of this supernova fallout,

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one from about 2 to 3 million years ago and another from around 6 to 9 million years ago.

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It's not exactly a receipt with the home address of each dead star, but the evidence is rock solid.

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Dust from dead stars actually made its way all the way to the Earth, rained down, and now there's still some left at the bottom of the oceans.

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Pretty cool if you ask me.

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Anyway, like I said, millions of years have passed, and some of the evidence is still exactly where it landed.

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So, hold up, this is where our literal straight up journey ends.

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Otherwise, I'd be lying to you.

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From here on we stop flying and crank the galactic zoom to the max, pull the camera far beyond the local bubble,

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and the entire Milky Way galaxy comes into view.

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We've generally been sold on the idea that the Milky Way is some kind of beautiful, peaceful, glowing spiral like you see in the movies.

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Yeah, no. As soon as you rise above the galactic disc,

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that picture-perfect postcard instantly turns into a brutal crime scene.

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In the outer halo, that's the massive, rarefied sphere surrounding our galaxy, stellar streams stretch out.

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Take the Sagittarius stream, for example.

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That, ladies and gents, is what's left of one particular dwarf galaxy

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that the Milky Way has been methodically tearing to bits with its gravity for well nigh on billions of years now.

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The Milky Way is, in fact, a ruthless beast of a cannibal.

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It dragged its small neighbor into its orbit and is now smearing

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and smushing its stars in long glowing ribbons above and below its own plane.

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It looks beautiful in pictures, but in reality it's one galaxy digesting another for billions of years.

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But stellar graveyards are just child's play.

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Let's turn towards the very center of the galaxy and then look straight up.

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Hovering there in the dark are the Fermi bubbles.

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What Fermi bubbles?

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What the heck are those?

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Well they sound harmless, don't they?

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But they're not.

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These are two colossal regions of gamma ray emission, together with super duper heated gas and extremely high energy particles.

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Each one stretches about 25,000 light years from the galactic center.

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25,000 light years!

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Well just where does all that energy come from?

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I know you probably know.

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The prime suspect is none other than the supermassive black hole at the center of our galaxy, Sagittarius A-star.

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Millions of years ago, this monster is said to have feasted on a massive cloud of gas

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and then unleashed a gigantic burst of energy.

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If so, the Fermi Bubbles are the aftermath of that very event, or meal if you want to look at it that way.

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But the case isn't closed yet.

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have a second suspect, a powerful burst of star formation at the galactic center.

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Essentially, we have an enormous crime scene and two possible suspects.

145

Take your pick.

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And amidst all this chaos, the entire galaxy somehow holds together the disk,

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the stellar streams, the scorching gas, and the hundreds of billions of stars.

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So why doesn't it all just fly apart and off into the void?

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Well most of the heavy lifting here is done silently by the dark matter halo,

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an invisible, roughly spherical structure surrounding the Milky Way.

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It appears to contain more dark matter than all the galaxies, stars, planets and nebulae put together.

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We've got no idea what it's made of, but its gravity holds the entire galaxy in an iron grip.

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Look, I know, this whole dark matter thing all seems a bit convenient.

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They looked at things and the math wasn't mathin', so they just added a big dollop of invisible matter.

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But look, its effects keep showing up all over the place, in how galaxies rotate, how clusters move,

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and in gravitational lensing where invisible mass bends light.

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Something's there.

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Yeah, we can't see it or detect it directly, so far, hence the name Dark,

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but obviously we can't just toss it out of the equations either.

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There is one awkward detail here.

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We started by saying that flying directly out of the plane of the solar system is practically impossible.

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It requires insane fuel reserves or extremely tricky gravity assists.

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Except that humanity has already flown up.

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A bit, anyway.

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And we did it over 30 years ago.

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In 1990, the Ulysses probe headed into deep space, and instead of trying to brute force its way straight up from the Earth,

167

burning through tank after tank of precious fuel, it first flew towards Jupiter.

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Near Jupiter, Ulysses pulled off a brilliant gravity assist maneuver.

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The giant planet redirected the probe onto a trajectory inclined almost 80 degrees to the planetary plane.

170

And Ulysses became the first probe in history to pass over the northern and southern polar regions of the sun,

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not somewhere off to the side like the Earth and almost every other spacecraft, but almost directly above and below it.

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physics actually let us out of our 2D prison here.

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So why the hell don't we have that beautiful top-down photo of the solar system yet?

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Because Lissy simply didn't have a camera.

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It didn't fly out there for pretty desktop wallpaper.

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It had a serious scientific job measuring the solar wind, the magnetic field, and and invisible streams of charged particles.

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So, for almost 19 years, the probe just looped over the sun's poles,

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gathering unique data, but never took that most desired family portrait of the planets.

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But even if it had a camera, we still wouldn't have gotten one of those familiar textbook pictures.

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There wouldn't be any glowing orbital lines, or large colorful spheres neatly arranged around the sun.

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Almost the entire frame would be basically black.

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In the center there would be a blindingly bright sun, and the planets would look like a few pathetic pixels,

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some of which would be completely drowned out by the solar glare.

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To see the whole system at once, the probe would have had to have flown much higher

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and carried a telescope that wouldn't go blind from the sun

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while also still being able to spot the faint specks of the planets. And

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that beautiful solar system from above picture would have to be

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stitched together from dozens of separate shots with drawn in orbits

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and planets artificially enlarged thousands of times just so we could see them.

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So in the end, we wouldn't get a photo, but just another diagram, only an incredibly expensive one.

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Recently, though, humanity finally began to be able to see the sun from above its equatorial plane.

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In 2025, a spacecraft called Solar Orbiter reached a vantage point almost 17 degrees south of the solar equator,

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giving us our first direct view of the sun's south pole.

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Yeah, that doesn't sound super impressive,

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big deal, 17 degrees, but until then we'd image the Sun almost exclusively from the level of its equator.

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It's like spending your whole life seeing someone only from the side, and then suddenly discovering the top of their head.

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After further gravity assists at Venus,

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Solar Orbiter's inclination should increase first to 24 degrees, then eventually to 33.

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But even then it isn't going to take a picture of the entire solar system for us.

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It's studying stuff like the sun's magnetic fields and the solar wind

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and the fundamental mystery of how our star flips its magnetic poles every 11 years.

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Another problem is that we haven't even agreed on what UP actually is.

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The plane in which the planet's orbit is tilted about 60 degrees relative to the Milky Way's disk.

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So if you fly strictly up from the solar system, you won't majestically rise above the galaxy.

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You'll just plow diagonally through it, right through the stars and dust.

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Earth has one up, the solar system has another, and the whole big Milky Way has a third.

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We've been trying this whole time to find another floor above us.

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First above the planets, then above the sun, then above the entire galaxy.

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But the higher we climb, the more obvious it becomes.

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The problem isn't the root, it's the question itself.

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There is no universal up in the universe.

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Now we can finally answer the question that started it all.

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What is directly above the solar system?

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If you just head straight up relative to the planetary plane, your route will look like this.

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First, the edge of the heliosphere.

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Then the interstellar medium with the Oort cloud extending through part of it.

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That's it.

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The Sagittarius stream and the Fermi bubbles are not the next floors right above us.

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They are parts of a completely different, much more massive structure, the Milky Way.

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And beyond that, it's just the rest of the universe.

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And the solar system's plane itself isn't a cage.

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In fact, it's really just a memory.

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About 4.6 billion years ago, the sun and the planets formed from a colossal spinning cloud of gas and dust.

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The cloud collapsed, its rotation sped up, particles smushed into each other,

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and physics gradually flattened this giant cosmic soup into a disk.

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The sun ignited in the center, and our worlds formed from the remaining material.

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So Earth is flying sideways, not because someone maliciously locked it onto cosmic rails.

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It's simply continuing a motion inherited from the material that formed it, one that began long before the Earth itself even existed.

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For billions of years, all the planets have been racing in roughly the same direction around the sun,

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like cars on a massive, endless roundabout.

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You can take an exit.

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Physics doesn't forbid it.

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It's just that any sharp turn in space will cost you an absurd amount of energy.

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That's why our probes don't blast straight up.

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They haggle with gravity instead, catching rides from Jupiter and Venus, hopping between orbits for years,

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and squeezing every last bit of performance out of each kilogram of fuel.

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We aren't trapped in two dimensions, we're just passengers traveling through a giant 3D universe on a shoestring budget.

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And even if one day we muster the resources

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and send a probe far enough above the planetary plane

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and point its camera back at the solar system and take that historic shot, it probably won't look anything like the picture in the textbook.

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And of course, someone will inevitably look at that dark frame and ask, wait, what?

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We spend several billion dollars on this crapola.

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このレッスンの語彙とスピーキングのポイント

このB2レベルのスピーキングレッスンは、動画「Why We Can Reach Pluto But Can’t Fly Above the Sun」を教材にしています。繰り返し出てくる語は次のとおりです：solar, above, galaxy, sun, cloud。この動画には、シャドーイング用の文が242文、単語が3131語あります。音声の長さは22:41です。話す速さは1分あたり約138語で安定しており、シャドーイングしやすいペースです。英語の頻出3,000語に含まれる単語は78%だけなので、語彙は難しめです。

この動画の重要語彙

動画の中で特に難しい単語15語を、発音と意味つきで紹介します。

単語	発音	意味
cosmic 形容詞	/ˈkɑz.mɪk/	宇宙の
bubble 名詞	/ˈbʌbəl/	泡
orbit 名詞	/ˈɔɹ.bɪt/	軌道
disk 名詞	/dɪsk/	ディスク, 円盤
invisible 形容詞	/ɪnˈvɪzəb(ə)l/	目に見えない, 不可視の
planetary 形容詞	/ˈplænɪˌtɛəri/	惑星の
spacecraft 名詞	/ˈspeɪsˌkɹæft/	宇宙機
colossal 形容詞	/kəˈlɑsəl/	巨大な
croissant 名詞	/kɹəˈsɑnt/	クロワッサン
supernova 名詞	/ˌsuː.pə(ɹ)ˈnəʊ.və/	超新星
gigantic 形容詞	/d͡ʒaɪˈɡæntɪk/	巨大な
comet 名詞	/ˈkɒmɪt/	彗星, 箒星
surround 動詞	/səˈɹaʊnd/	囲む, 取り巻く
zoom 動詞	/zuːm/	猛スピードで進む
particle 名詞	/ˈpɑɹtək(ə)l/	粒子

動画に出てくる句動詞

単語	発音	意味
zoom out 動詞	/ˌzuːm ˈaʊt/	ズームアウトする, 縮小する
blow up 動詞		爆破する, 爆発する
find out 動詞		見出す, 調べる
get out 動詞		出て行く
leave behind 動詞		置き忘れる
show up 動詞		現れる
slow down 動詞		遅らせる
speed up 動詞	/spiːdˈʌp/	スピードを出す

この動画の文法

話し手がよく使っている文型を、動画の実際の表現とともに紹介します。

文型	動画での表現
現在完了進行形 have/has been + -ing — 以前に始まり今も続いている動作	guy's been cruising · We've been trying · have been racing
現在完了形 have/has + 過去分詞 — 過去の出来事が今も関係している	we've sent · has already done · you've never actually seen
受動態 be + 過去分詞 — 誰がするかより、何が起きるかに焦点を当てる	was named · been sold · is said

注意したい発音

話し手はwe're, isn't, don'tなど、短縮形や弱形を56回使っています。聞こえたとおりの短い形で発音しましょう。

「th」の音: pathetic /pəˈθɛtɪk/, mathematics /mæθ(.ə)ˈmæt.ɪks/
「sh」と「zh」の音: barrage /bəˈɹɑʒ/, gravitational /ˌɡɹævɪˈteɪʃənəl/, inclination /ˌɪn.klɪˈneɪ.ʃən/, sheer /ʃɪɚ/, dimension /daɪˈmɛn.ʃən/
長い単語（アクセントの位置に注意）: invisible /ɪnˈvɪzəb(ə)l/, planetary /ˈplænɪˌtɛəri/, supernova /ˌsuː.pə(ɹ)ˈnəʊ.və/, gravitational /ˌɡɹævɪˈteɪʃənəl/, inclination /ˌɪn.klɪˈneɪ.ʃən/

日本語話者が苦手な音：

/r/ と /l/ の区別 — /l/ は舌先を歯茎につけ、/r/ はどこにもつけない: planetary /ˈplænɪˌtɛəri/, stellar /ˈstɛl.əɹ/, spherical /ˈsfɛɹɪkəl/, orbital /ɔɹ.bət.l̩/, particle /ˈpɑɹtək(ə)l/
/v/ — /b/ にならないように、上の歯を下唇に当てる: invisible /ɪnˈvɪzəb(ə)l/, supernova /ˌsuː.pə(ɹ)ˈnəʊ.və/, void /vɔɪd/, gravitational /ˌɡɹævɪˈteɪʃənəl/, vector /ˈvɛktɚ/
/f/ — 「フ」ではなく、上の歯と下唇で出す: spacecraft /ˈspeɪsˌkɹæft/, spherical /ˈsfɛɹɪkəl/, rarefy /ˈɹɛəɹəˌfaɪ/, freeze /ˈfɹiːz/, terrify /ˈtɛɹɪfaɪ/

この動画での練習方法

まず声を出さずに動画を最後まで聞き、知らない単語をメモします。
通常の速度で一文ずつシャドーイングし、話し手のリズムに合うまで繰り返します。
自分の声を録音して元の音声と比べます。cosmic, bubble, orbitなどの単語に特に注意しましょう。

シャドーイングとは？英語上達に効果的な理由

シャドーイング（Shadowing）は、もともとプロの通訳者養成プログラムで開発された言語学習法で、多言語習得者として知られるDr. Alexander Arguelles によって広く普及されました。方法はシンプルですが非常に効果的：ネイティブスピーカーの英語を聞きながら、1〜2秒の遅延で声に出してすぐに繰り返す——まるで「影（shadow）」のように話者を追いかけます。文法ドリルや受動的なリスニングと異なり、シャドーイングは脳と口の筋肉が同時にリアルタイムで英語を処理・再現することを強制します。研究により、発音精度、抑揚、リズム、連音、リスニング力、そして会話の流暢さが大幅に向上することが確認されています。IELTSスピーキング対策や自然な英語コミュニケーションを目指す方に特におすすめです。

シャドーイングのやり方: ステップ別の完全ガイドを読む →

シャドーイング練習: Why We Can Reach Pluto But Can’t Fly Above the Sun - 動画で英語スピーキングを学ぶ

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