Slow Orbit · Episode 1 · 29 min

The Solar System

A slow journey outward from the Sun, past each planet in turn, to the edge of the Solar System. Read by a synthetic voice. Script written and fact-checked by the show's team.

The script

The star

At the centre of our Solar System... there is a star.

It has burned here, steadily, for about four and a half billion years. Everything that travels around it... every planet, every moon, every grain of dust... depends on it.

The Sun is enormous. Across its face, one hundred and nine Earths could lie side by side... and still only just reach from one edge to the other.

And it holds almost everything. All the planets, all the moons, all the comets and the rocks together... are less than one part in a hundred of all the matter here. The rest... nearly all of it... is the Sun.

Its surface is never still. Cells of glowing gas, each one larger than a country, rise from below... spread out... cool a little... and sink back down. Again, and again. From far away it looks smooth. Up close, it is slowly boiling.

Here, at the surface, the temperature is around five and a half thousand degrees. Deep below, in the core, where the light is made... it is millions of degrees hotter.

Now and then, a great arch of glowing gas lifts from the edge of the Sun... hangs there, bright against the dark... and slowly falls back.

The light leaves in every direction. A small part of it travels toward a blue world, and arrives there eight minutes and twenty seconds later. On that world, the light of every afternoon left the Sun a few minutes before... a little like the sound of a bell, arriving a moment after it is struck.

From here, the journey goes outward.

Mercury

The first world is small... and grey.

Mercury. The planet closest to the Sun.

It is only a little larger than our Moon, and it looks very much like it. Grey dust. Round craters, one inside another... the marks of stones that fell here long, long ago, and were never washed away. There is no rain here to wash them. No wind to smooth them.

Mercury is the swiftest of the planets. It races around the Sun in just eighty-eight Earth days.

And yet, it turns on its axis very slowly. On Mercury, from one sunrise to the next takes about one hundred and seventy-six Earth days.

A single day here... lasts longer than two of its years.

The Sun rises over the grey plains... huge, white, and slow. It climbs for weeks. The shadows of the crater walls shorten, little by little. The rocks grow hot... hot enough to melt lead.

Then, very slowly, the Sun goes down.

And with almost no air to hold the warmth, the heat drains straight away into space. The night that follows is months long... and colder than anywhere on Earth.

Light... and then darkness... and then light again. That is all the weather Mercury has ever known.

Venus

Further out, a pale light. Soft... creamy... and very bright.

Venus.

Seen from Earth, it is the brightest point in the evening sky, or the morning sky... brighter than any star. For thousands of years, people called it the evening star, and the morning star.

Up close, it is wrapped in cloud. Thick, smooth, pale yellow cloud... that never opens. Not once. The ground beneath has never been seen by eye... only by radar, and by a handful of small landers that survived on the surface for just a short time.

Venus is almost exactly the size of the Earth. For a long while, people imagined warm swamps and forests under those clouds.

The truth is stranger.

Beneath the clouds, the air is so thick that it traps the Sun's heat like a lid on a pot. The ground is around four hundred and sixty-five degrees... by day and by night... at the poles and at the equator. It is the hottest planet of all... hotter even than Mercury, though Mercury is closer to the Sun.

The air presses down with about ninety times the weight of the air on Earth... the pressure you would meet deep under the sea.

And Venus turns backwards. Here, if the clouds ever parted, the Sun would rise in the west... and set in the east.

It turns so slowly that its day is longer than its year.

The pale planet glides on... its clouds lit softly by the Sun... keeping the surface hidden, as it always has.

Earth

And then... a blue light.

The Earth.

From a distance, it is small, and round, and very blue. White clouds turn in slow spirals over the oceans. Brown and green land slips in and out of the shadow.

At the very edge of the planet there is a thin glowing line. That line is the air. Every breath ever taken... every cloud... every breeze... every song ever sung... all of it has happened inside that thin, shining layer.

From out here, the Earth makes no sound. No cities. No traffic. No voices. It simply turns... once a day... carrying the morning across its face... and then the evening.

On one side, it is night. On the other, morning is arriving. The line between them moves slowly over the oceans and the mountains... as it has every day for billions of years.

The Earth travels around the Sun at a distance of about one hundred and fifty million kilometres. That distance is so useful that astronomers gave it a name of its own: one astronomical unit.

Close beside the Earth, a grey companion.

The Moon. About three hundred and eighty-four thousand kilometres away. It always turns the same face toward the Earth... as if it were listening.

The Moon has a story of its own... for another night.

Mars

Beyond the Earth, a reddish light. Warm in colour... but bitterly cold.

Mars.

It is about half as wide as the Earth. Its colour is the colour of rust... and it is rust: fine dust, full of iron, slowly rusted over a very long time. The whole planet is quietly, gently rusted.

A day on Mars lasts twenty-four hours and thirty-seven minutes. Almost a day like ours... with a few extra minutes in every evening.

But the evenings themselves are different. In the daytime, the Martian sky is a soft butterscotch colour. And at sunset, around the setting Sun, the sky turns blue... a cool, pale blue glow. The opposite of sunsets on Earth.

Mars has the tallest mountain of any planet. A volcano called Olympus Mons. It rises more than twenty kilometres above the land around it... more than twice the height of Everest. Its slopes are so wide and so gentle that someone standing on them would not know they were on a mountain at all. Just a long, slow rise... running on, past the horizon.

There are canyons here, and old dry riverbeds... where water once ran, a very long time ago. At the top and the bottom of the planet, white caps of ice.

And in the red valleys there are small machines from Earth. Sojourner. Spirit. Opportunity. Curiosity. Perseverance. They roll a little way each day... stop... look... measure... and roll on. One of them even brought a tiny helicopter, Ingenuity, which lifted into the thin air and flew.

In a quiet valley, one of them stands still as the blue sunset fades... waiting for the morning.

Two small moons circle Mars. Phobos and Deimos. They are not round... they are small and lumpy, like potatoes... and they cross the Martian sky in silence.

The asteroid belt

Beyond Mars lies a great, wide ring of small rocky worlds.

The asteroid belt.

In films, it is crowded. Rocks tumbling everywhere... ships swerving between them.

The real one is nothing like that.

The real asteroid belt is mostly empty. The rocks are so far apart that, standing on one, the next would usually be too far away to see. Spacecraft have crossed it many times, and passed through untouched.

Now and then, far off... a grey shape turns slowly in the sunlight. Then it is gone. And there is only the dark again.

The largest of them is Ceres. It is round, and small, and quiet... large enough to be called a dwarf planet. On its surface there are bright spots... patches of salt that catch the sunlight like frost on a winter field.

One asteroid... and then, a long time later... another.

Jupiter

Far ahead, a bright point grows into a small disc. The disc grows into a striped ball. And the ball grows... until it fills the view.

Jupiter.

The giant of the Solar System. It has more than twice the mass of all the other planets put together. Eleven Earths could lie across its face.

There is no ground here. Jupiter is a vast ball of gas... mostly hydrogen and helium, the same materials as the Sun. What we see are the tops of its clouds: long bands of cream, and tan, and brown, and rust... each one flowing around the planet at its own speed... sliding past its neighbours.

Where the bands meet, the clouds curl into eddies... like water around a stone in a river.

And in one of those bands... there is a storm.

The Great Red Spot.

It is wider than the whole Earth. It turns, slowly, round and round. It has been watched through telescopes for well over a hundred and fifty years... and it is still turning. In recent years, it has been growing a little smaller. But it is there tonight... as it has been for longer than anyone has been watching.

For such a vast world, Jupiter spins quickly. A day here lasts less than ten hours.

Jupiter has many moons. Most are small. But four are large... and they have a story.

In sixteen ten, an Italian astronomer, Galileo, turned one of the very first telescopes toward Jupiter. Beside the planet he saw four small points of light. Night after night, they moved... first on one side, then on the other. He understood what he was seeing. Small worlds... travelling around another world.

They still carry his name. The Galilean moons.

Io. The most restless world in the Solar System. Covered in volcanoes... always erupting... glowing yellow and orange.

Europa. Smooth and white, sealed in a shell of ice. And under that ice, scientists believe, a deep ocean of liquid water... lying in the dark.

Ganymede. The largest moon in the Solar System... larger even than the planet Mercury.

And Callisto. Old, and quiet, and covered in craters... a face that has seen a great deal.

Jupiter turns... its bands flowing... its storm turning... and its four moons circle it, as they have every night since long before Galileo first saw them.

Saturn

Further out, the light is softer. The Sun is smaller now.

And ahead... a golden planet, with a ring around it.

Saturn.

Perhaps the most beautiful of all the planets. Its rings spread out around it, wide and bright and delicate... like a brim of light.

They are not solid. They are made of countless pieces of ice, and a little rock. Some as small as grains of dust. Some as large as a house. All of them travelling around Saturn together... each on its own small path.

The rings are immense. The main rings would stretch more than two thirds of the way from the Earth to the Moon.

And yet they are astonishingly thin. In most places, about ten metres. No taller than a house. A model of the rings as wide as a football field would be thinner than a sheet of paper.

Wide... and thin... and shining.

Saturn itself is a ball of gas, like Jupiter, banded in soft gold. And it is remarkably light for its size. In an ocean large enough to hold it... Saturn would float.

A giant golden planet... floating... rising and falling on slow, enormous waves.

Its largest moon is Titan. Wrapped in a thick orange haze, it is the only moon with a heavy atmosphere. And under that haze there are lakes, and seas... not of water, but of liquid methane... lying still beneath a dim orange sky.

For thirteen years, a spacecraft called Cassini circled Saturn, sending home pictures of the planet, its rings and its moons. In two thousand and seventeen, at the end of its long work, Cassini made one last careful dive into Saturn's clouds... and became part of the planet it had studied for so long.

The rings tilt slowly as the planet passes... from a wide golden oval... to a single bright line... and open again.

The long dark

After Saturn, the distances become very large.

The Sun is now only a small, bright, distant light. Still the brightest thing in the sky... but no longer a great warm disc.

For a long time, there is nothing to see. Only the dark... and the stars.

In the summer of nineteen seventy-seven, two small spacecraft left the Earth, one after the other. Voyager 1, and Voyager 2. They passed Jupiter. They passed Saturn. And Voyager 2 went on... further out... toward the last two planets.

It took Voyager 2 twelve years to travel from the Earth to the very last planet.

Twelve years... crossing this emptiness... sending home a faint signal now and then... until at last, a pale blue-green world appeared ahead.

Out here, there is no hurry. There never is.

Uranus

The light ahead is pale and blue-green... like sea glass.

Uranus.

It was the first planet discovered with a telescope. In seventeen eighty-one, the astronomer William Herschel noticed it, and at first he thought it was a comet. It was a whole new world... and overnight, the known Solar System doubled in size.

Uranus is an ice giant. Cold and large, made mostly of water, ammonia and methane, deep beneath a smooth, hazy sky. The methane gives it that soft blue-green colour.

But the strangest thing about Uranus is the way it moves.

It lies on its side.

The other planets spin more or less upright as they circle the Sun... like spinning tops. Uranus is tipped over. It rolls along its path... like a ball rolling slowly across a floor.

Long ago, it seems, something very large struck it... and knocked it over. It has rolled this way ever since.

Uranus takes eighty-four Earth years to travel once around the Sun. And because it lies on its side, each of its poles has about forty-two years of daylight... followed by about forty-two years of night.

Forty-two years of a long, low evening... and then a night that lasts half a lifetime.

Uranus has faint dark rings, and many moons, named after characters from plays and poems. Miranda. Ariel. Titania. Oberon.

Only one spacecraft has ever visited. Voyager 2 passed by in nineteen eighty-six... looked carefully for a few days... and travelled on.

Neptune

Far, far out... the last of the planets.

A deep, rich blue.

Neptune.

It lies about thirty times farther from the Sun than the Earth does. Sunlight, which reaches the Earth in a little over eight minutes, takes about four hours to arrive here.

From Neptune, the Sun is no longer a disc at all. It is a small, very bright star... brighter than any other in the sky... but small.

Neptune was not found by looking. It was found by thinking.

Astronomers noticed that Uranus was not moving quite as it should. Something unseen was pulling on it... very slightly. In France, a mathematician named Urbain Le Verrier worked out, with pen and paper, where an unseen planet would have to be.

In eighteen forty-six, in Berlin, the astronomer Johann Galle pointed a telescope at that place in the sky... and there it was. A new planet. Very close to where the mathematics had said.

Neptune is cold and dark, but it is not still. It has the fastest winds in the Solar System... about two thousand kilometres an hour. White clouds stream across its blue sky. Dark storms appear... grow... and fade away again.

Neptune takes about one hundred and sixty-five Earth years to travel once around the Sun. Since the night it was discovered, it has completed only one full journey.

Its largest moon, Triton, travels around it backwards... against the planet's spin. Triton's surface is frozen and pale, with icy plains and dark streaks... one of the coldest places ever measured.

Voyager 2 reached Neptune in nineteen eighty-nine. It is still the only visitor this blue world has ever had. After it passed, it turned for one last look back... and continued into the dark.

The edge

Beyond Neptune, the Solar System does not simply end.

Out here, in the cold, there is a wide ring of small icy worlds... thousands upon thousands of them... drifting slowly around a faraway Sun.

One of them is Pluto. Once counted as the ninth planet... now a dwarf planet. Small, and icy... with a pale plain on its surface in the shape of a heart.

Pluto, too, has a story of its own... for another night.

From here, looking back, everything lies behind. The Sun. Small grey Mercury. Hidden Venus. The blue Earth and its Moon. Red Mars. The scattered stones of the belt. Great striped Jupiter. The golden rings of Saturn. Uranus on its side. Deep blue Neptune.

From here, they are only small points of light... some too faint to see at all... gathered around one bright star.

The scale of it is hard to hold. If the Sun were a grapefruit, lying on a table... the Earth would be a grain of sand, about thirteen metres away. Jupiter would be a small marble, about seventy metres away. And Neptune would be a tiny bead... about four hundred metres away... almost half a kilometre.

And the nearest star? On the same scale, it would be thousands of kilometres from the table.

So much space... mostly darkness... and a few small worlds, travelling patiently around their star.

The planets keep travelling

Far behind, the Sun is shining... and the planets are travelling around it... each on its own path, each at its own pace.

Mercury, in its long afternoon. Venus, under its clouds. The blue Earth, with its Moon. Mars, with its blue sunset. Jupiter, turning its great storm. Saturn's rings, shining. Uranus, rolling on its side. Neptune, deep and blue at the edge.

They have travelled like this for about four and a half billion years.

Nothing pushes them. Nothing hurries them. Each one simply follows its path... around... and around... as it has every day and every night, since long before anyone was there to watch.

And they will go on... after tonight... and after tomorrow... quietly... in the same way.

On the small blue world, evening moves slowly across the land... the lights come on, one by one... and then the night.

And far away... the Sun... keeps shining.

Also from the late hours: Embers of History · The Quiet Armoury · Myth and Score