Plus de 50 faits sur l'espace mettront à l'épreuve les limites de votre imagination

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Transcript

00:00:00 "Hang on to your hat, we're going to embark on an incredible journey.

00:00:05 With the help of brilliant scientists and their work, we asked the AI to bring us 2 billion years back

00:00:11 to show us what our wonderful planet looked like at the time.

00:00:15 So, we tie his belt and off we go.

00:00:17 Jumping in a time travel machine and going to visit Earth when it was just a baby

00:00:22 about 4 or 5 billion years ago would have been a big mistake.

00:00:27 A total chaos would have reigned then.

00:00:30 First of all, the ground was still in fusion and very soft,

00:00:33 so landing your time travel machine would have been a problem.

00:00:37 And as soon as you got out of the machine, you would have seen a completely different Earth

00:00:41 from the one we know today.

00:00:43 The landscape was made of steep mountains, sparkling seas and vast expanses of land.

00:00:50 A massive volcano would erupt constantly, releasing gases and ashes into the air.

00:00:57 A real firework.

00:00:59 And even if you had a super machine capable of gliding and equipped with heat protection devices,

00:01:05 you would still have trouble breathing.

00:01:07 You see, the atmosphere of primitive Earth was a bit crazy.

00:01:11 Thick clouds floated in the sky, casting mysterious shadows on the Earth.

00:01:16 The air was as thin as a murmur and filled with all kinds of strange gases,

00:01:21 like hydrogen and helium.

00:01:24 Carbon dioxide was everywhere, coloring a sparkling glass.

00:01:28 The steam filled the air and made it very humid.

00:01:31 And there was also a suspicion of ammonia and methane, in case all that wasn't enough.

00:01:36 It's a lot of gas, huh?

00:01:38 But something is missing, oxygen.

00:01:40 By inhaling, you wouldn't feel this familiar breath of air filling your lungs.

00:01:45 There were no luxurious forests yet.

00:01:48 Instead, you could find rugged and rocky terrain.

00:01:52 Some of these rocks still bear the marks of the intense forces, collisions and earthquakes

00:01:58 that shaped the Earth for millions of years.

00:02:01 But in the midst of all this violent beauty, something amazing was about to happen.

00:02:06 Life, in its infancy, was preparing its big entrance.

00:02:10 Organisms such as algae and bacteria dominated the scene.

00:02:14 They thrived in the oceans.

00:02:16 They fed on carbon dioxide to grow and multiply.

00:02:20 The cells grew slow, active, full of microscopic, multicolored and protruding life forms.

00:02:26 These tiny organisms worked hard, releasing oxygen while vacating their occupations.

00:02:32 These real little factories slowly modified the composition of the atmosphere.

00:02:37 This is what the primitive Earth looked like, more or less.

00:02:41 But why was it so hostile?

00:02:44 And how has it been able to change so much since?

00:02:47 The heat of the Earth comes from all kinds of things that happened during its formation.

00:02:51 First of all, the objects that came together to form our planet were already releasing a lot of heat.

00:02:57 Then, as the Earth grew, its gravitational force increased considerably.

00:03:04 It attracted even more matter towards it, and it also squeezed it very hard in its arms.

00:03:09 And you know what happens when you compress something?

00:03:12 It heats up like a coconut.

00:03:15 This incredible warming had a huge impact on the structure of the Earth.

00:03:19 Imagine a mixture of rocks, metals and minerals.

00:03:22 As the heat rose, all this matter began to melt.

00:03:26 And guess what?

00:03:27 A very dense metal flowed to the center and became the core of the Earth,

00:03:32 while the lighter rocks rose to form the crust and the mantle.

00:03:36 It's as if the Earth had decided to dissociate itself by creating distinct layers.

00:03:41 [In the language of the ancient Greek]

00:03:44 But the warming did not stop there.

00:03:47 With all these mixtures and these displacements, the Earth became even warmer.

00:03:51 It was as if you were increasing the temperature of a giant planetary oven.

00:03:55 All this crazy heat had serious consequences.

00:03:59 The high temperature of the Earth accelerated everything.

00:04:02 The tectonic plates were dancing. A real geological stir was taking place on the surface.

00:04:08 And that's not all.

00:04:09 The Earth was also bombarded by serious cosmic visitors.

00:04:13 Imagine that.

00:04:15 While the Earth was busy collecting all kinds of space debris and forming,

00:04:20 the mess reigned in the solar system.

00:04:23 Saturn and Jupiter had a great idea of all the chambers in the orbit of the sun,

00:04:27 sending all their massive objects to our poor Earth.

00:04:32 And it was not a joke.

00:04:34 These impacts melted the minerals of our Earth's crust and even vaporized them.

00:04:38 These collisions were so powerful that they even released the gases from the Earth's atmosphere.

00:04:44 You're talking about a firework. Believe it or not,

00:04:47 we can still observe the scars of these old collisions.

00:04:51 It takes a detective's work, but its consequences are clearly visible for a trained eye.

00:04:57 For example, we have the crater of Mani Itzok in Greenland.

00:05:02 Even if the crater itself is not visible,

00:05:04 we find in this area of the rocks that used to be at a depth of 20 to 25 km under the surface of the Earth.

00:05:12 And guess what?

00:05:13 It bears the marks of an intense and sudden shock.

00:05:16 A lot has happened.

00:05:18 The biggest collision took place with a planet called Theia.

00:05:22 Theia, the size of Mars, would have crashed on Earth with a huge boom.

00:05:26 A colossal event that changed everything.

00:05:29 The metallic core of Theia merged with that of the Earth,

00:05:32 while the outer layers of the two planets were projected into space.

00:05:37 The result? A magnificent ring of debris around our planet.

00:05:42 Here is the most interesting part.

00:05:44 These debris did not float indefinitely.

00:05:47 They started to assemble like puzzle pieces.

00:05:50 And here we are.

00:05:51 We have obtained our moon.

00:05:53 Incredible, isn't it?

00:05:55 And this amazing process would have taken only 10 years, or less.

00:05:59 It's completely crazy.

00:06:01 This formidable event about the Moon is called the "hypothesis of the giant impact".

00:06:06 So the next time you look at our satellite in the night sky,

00:06:09 remember that it is actually a big piece of our own planet.

00:06:14 In addition, the Earth also experienced a great adventure

00:06:17 during the creation of its atmosphere.

00:06:20 The first attempt at creating an atmosphere did not go very well.

00:06:24 A thin layer of hydrogen and helium formed

00:06:27 when all this matter accumulated.

00:06:29 But these gases did not hold.

00:06:31 They ended up escaping into infinite space.

00:06:34 Goodbye guys.

00:06:36 But the Earth did not give up.

00:06:37 It left again more beautiful.

00:06:39 And this time it was much more successful.

00:06:42 The volcanoes came to the rescue.

00:06:44 They spat out all kinds of gases, water vapor, carbon dioxide,

00:06:48 and all kinds of other bizarre substances.

00:06:51 Even the meteorites and comets participated in the party,

00:06:55 bringing air and nitrogen.

00:06:58 Our atmosphere is on the verge of becoming what it is today.

00:07:02 But there you go.

00:07:03 There was no oxygen in this second experiment.

00:07:06 No, not a single little bite.

00:07:09 The oxygen produced by the sun's rays by dividing water molecules

00:07:13 disappeared immediately because of certain chemical reactions.

00:07:16 It was only with the third experiment, and the appearance of life,

00:07:20 that things began to change.

00:07:23 Photosynthetic organisms took the lead

00:07:26 and used all the carbon dioxide in the air to make their food.

00:07:31 And they started releasing oxygen.

00:07:34 Finally, these organisms managed to produce so much oxygen

00:07:37 that the chemical reactions could no longer stop the process,

00:07:40 and an atmosphere was created.

00:07:42 It is only for about 350 million years that we have reached

00:07:45 the oxygen level we know today,

00:07:48 about 21% of the air we breathe.

00:07:51 Thus, volcanoes ignited in the mysterious oceans,

00:07:54 this little glimpse of the past reveals a very different Earth

00:07:57 from the one we know.

00:07:59 It is fascinating to explore these landscapes

00:08:01 and to imagine the first forms of life developing.

00:08:05 Thanks to the IAEA, we can see the extraordinary history of the planet

00:08:09 and admire the wonders of its perpetual evolution.

00:08:13 So, stay tuned for more exciting trips.

00:08:17 In space, no one can hear you scream.

00:08:21 As everyone knows, star explosions, asteroids crashing,

00:08:26 and planets on fire don't make any noise in space.

00:08:29 Really?

00:08:31 What if we could hear some noise up there?

00:08:34 OK, back to school.

00:08:36 Sound is a mechanical wave coming from a vibration.

00:08:39 But what does that mean exactly?

00:08:42 The most famous example is that of guitar strings.

00:08:45 If you scratch one of them, it starts vibrating.

00:08:48 The atoms inside the metal string start to vibrate

00:08:51 and hit the atoms of the air around them.

00:08:53 The atoms push each other until some reach our ears.

00:08:57 It's like the wave created by a stone thrown into a pond.

00:09:00 It happens very quickly, at a speed of around 340 m/s.

00:09:05 Then, our eardrums start vibrating at the same frequency.

00:09:10 The small water inside our ears transmit this vibration to the brain.

00:09:14 The brain then uses its magic, recognizes the pattern, and turns it into sound.

00:09:20 Great! Now we know that we need certain particles to create sound.

00:09:26 And we can find these particles in gases, liquids, and solid substances.

00:09:31 But what about space?

00:09:33 It's an almost perfect vacuum.

00:09:35 And you've probably heard that there's no sound in space because it's a vacuum.

00:09:40 But what does that really mean?

00:09:43 A perfect vacuum is a totally devoid of matter.

00:09:47 That means there's nothing in this place.

00:09:50 Yes, despite all these celestial bodies in space,

00:09:53 there's no air between them, no atoms, no particles.

00:09:57 Nothing at all.

00:09:59 In fact, almost nothing.

00:10:01 To be exact, a perfect vacuum doesn't really exist.

00:10:04 We can't get rid of atoms, but space is very close to this notion.

00:10:09 On average, there are 1 to 5 atoms per cubic centimeter.

00:10:13 That may seem like a lot, but you have to keep in mind that these atoms are microscopic,

00:10:18 and the distance between them is huge.

00:10:21 For comparison, 1 cubic centimeter of air contains about 1,000 atoms.

00:10:26 So, of course, with such a low density, these atoms can't push each other,

00:10:31 even if the vibration is very strong, like in the case of a supernova, for example.

00:10:36 They still can't do it.

00:10:39 But then, movies are lying to us.

00:10:42 All these epic space scenes actually take place in an almost embarrassing silence.

00:10:47 Not so fast.

00:10:49 What if we told you that there are, in fact, certain ways to hear sound in space?

00:10:55 First of all, there's always noise on other planets.

00:10:58 If there's an atmosphere on a space body, or at least something like gas, water, or a solid surface, there will be noise.

00:11:06 In our case, the atmosphere becomes completely silent about 100 km above the Earth's surface.

00:11:13 That's when the sky stops being blue and a black starry veil begins.

00:11:19 In any case, you'd have to land on another planet or at least get close to its atmosphere to hear something.

00:11:26 But whatever it is, the sound would be very different.

00:11:29 Let's take the example of our sister planet, Venus.

00:11:32 The atmosphere there is very dense.

00:11:34 Scientists even call it a "thick chemical soup".

00:11:39 If you managed to stay alive and talk there, your voice would be very different.

00:11:45 It would be much louder and deeper.

00:11:49 So, if you've always wanted to sing like Pavarotti, now you know what to do.

00:11:54 And what would happen if the Earth had a denser atmosphere?

00:11:58 What would we hear?

00:12:00 Well, you can vaguely imagine it if you've ever been in the water.

00:12:05 The water is very dense. The sound moves much faster and better than in the air.

00:12:10 At a speed of almost 2 km per second.

00:12:15 If you sat in an empty room without a sound source, you wouldn't hear much, would you?

00:12:21 Now, dip your head in the water and observe how the same silence resonates here.

00:12:26 It's not silent at all.

00:12:28 Even if you don't hear the sound of the water itself, you'll immediately notice how much you can hear your own body.

00:12:35 How your blood pulses in your veins, how your heart beats, the slightest movement of your fingers.

00:12:40 Pretty scary, isn't it?

00:12:43 This gives us an idea of what would happen to us on a planet with a denser atmosphere.

00:12:48 And it's just crazy. We would hear everything.

00:12:52 Animals running, the movement of tectonic plates.

00:12:57 So it's obvious that there's sound on other planets.

00:13:01 But what about space?

00:13:04 There's also sound, for example, in a cloud of dust.

00:13:07 You can find space dust almost everywhere in space.

00:13:11 It could be the remains of a star or something else.

00:13:14 And in these places, everything is a little denser than normal.

00:13:18 This means that there are probably dust clouds where the particles are very close to each other.

00:13:24 This means that they can produce sounds.

00:13:27 Of course, these will be very weak and transmitted over a very short distance.

00:13:31 But it's still better than nothing, isn't it?

00:13:34 It turns out that we have already recorded a spatial sound.

00:13:38 It comes from the galactic llama of Perseus, which is 250 million light years away from us.

00:13:45 NASA recorded it in 2003.

00:13:48 It looks like a note in B flat.

00:13:52 But its frequency is so low that the human ear unfortunately cannot perceive it.

00:13:58 But apart from that, we can only hear something inside space ships.

00:14:03 After all, they are small air pockets.

00:14:06 In a space suit, you would also hear the sounds very well, including your breathing or the movement of your breast.

00:14:13 But two astronauts floating side by side would not hear each other, even if they were approaching and shouting very loudly.

00:14:20 It's quite funny.

00:14:22 If you hit your head against something, the noise would be very loud for you.

00:14:26 But your astronaut colleague would not hear anything.

00:14:29 That's why astronauts use radio devices.

00:14:32 Now, in a purely theoretical way, if you could somehow get out of your space suit and survive,

00:14:41 you would be able to hear the chatter and the noises that take place inside the space ship.

00:14:46 But how?

00:14:47 Simply because there is air inside the ship that transmits the sound.

00:14:51 The air reaches the metal envelope and crosses it.

00:14:54 If you pressed against the ship, preferably touching it with your elbow or knee,

00:15:00 the sound would be transmitted to the brain directly by your bones, ignoring the ears.

00:15:05 Yes, our bones drive the sound.

00:15:08 This is how, for example, deaf people listen to music.

00:15:11 This is what is called bone conduction, which is used in some headphones and other technologies.

00:15:17 You can do a little experiment.

00:15:19 Close your ears with your fingers.

00:15:21 Close them well so that you can hardly hear anything.

00:15:24 Then try to touch a sound source.

00:15:26 It can be anything that vibrates, for example a speaker playing music,

00:15:31 with a part of your body where the bone is close to the skin.

00:15:34 Now observe, or rather listen, the miracle happen.

00:15:38 You can hear the sound, not through your ears, but directly in your brain.

00:15:42 However, do not repeat this experience in space.

00:15:45 Now you've probably heard of things like the sounds of space,

00:15:51 where you can listen, for example, to the sounds emitted by the sun or different planets.

00:15:56 How do you record them?

00:15:57 It's pretty easy.

00:15:58 We use another way of hearing the sound in space, electromagnetic waves,

00:16:03 in other words, a radio.

00:16:05 The radio is based on the same form of electromagnetic radiation as light.

00:16:10 These waves can travel in space without any problem.

00:16:13 Astronaut emitters work this way.

00:16:16 An astronaut says something to his colleague.

00:16:20 The sound waves transform into radio waves, reach the other person,

00:16:24 and are then converted back into sound.

00:16:26 And this is how we get what we call the sounds of space.

00:16:30 Our planet is also very noisy in this regard.

00:16:33 We send a huge amount of radio waves into the universe,

00:16:37 all the radio signals we've already heard.

00:16:40 It's a shame that they only travel at 110 light years from us.

00:16:44 But after all, it may be a good thing that we don't hear everything that happens in space.

00:16:49 Imagine that sound could easily travel in the universe.

00:16:52 We would hear absolutely everything, from solar eruptions to supernovas.

00:16:57 Astonishing, isn't it?

00:16:59 Space is a Space Station

00:17:03 If you've ever seen pictures taken from a space ship or from the International Space Station

00:17:09 showing celestial bodies lit by the sun, like the Earth or the Moon,

00:17:13 you may have noticed something wrong.

00:17:16 Space seems too empty.

00:17:18 A magnificent background filled with stars is missing.

00:17:20 It seems that it would be very boring to go and observe the stars directly from space,

00:17:24 since the sky is always so dark.

00:17:27 During the day, the sky above our heads is blue because of the diffusion of light.

00:17:32 This happens when the sunlight passes through the atmosphere.

00:17:35 But if you are on the Moon or elsewhere in space,

00:17:38 there is no atmosphere to diffuse this light.

00:17:40 That's why the sun always seems dark.

00:17:43 But that doesn't mean there is less light.

00:17:46 If you took a look through a space station's window,

00:17:49 you would see as much direct sunlight as if you were looking through the window of your apartment

00:17:54 for a day without clouds, maybe even more.

00:17:56 When you take a picture in a sunny day, you probably use a short exposure

00:18:01 and the narrow aperture of your camera.

00:18:04 In this way, only a short burst of light enters the lens.

00:18:08 The same principle applies when our pupils contract to the sunlight

00:18:12 so as not to have to manage too much light.

00:18:15 And since it is just as bright up there in space,

00:18:17 the process is the same when you take pictures of objects lit by the sun.

00:18:21 By using a short exposure, you can get good pictures of the Earth or the surface of the Moon.

00:18:27 But that also means that there will be no stars in the picture.

00:18:30 Even up there, the stars are relatively dull.

00:18:33 They don't emit enough light to appear in the pictures taken with such settings.

00:18:38 Our planet has a blue sky, which slowly turns into a magnificent orange-red palette at dusk

00:18:44 and vice versa at dawn.

00:18:46 But if you ever get to observe a sunset on Mars,

00:18:49 you must expect the opposite, a bright orange-brown sky that takes a bluish hue at sunset.

00:18:55 First of all, Mars is further away from the sun than our planet.

00:18:58 So when you look at the sun from the Martian surface, it looks more dull and smaller.

00:19:04 And that's not all.

00:19:05 The sun observed since Mars is only a bluish white dot surrounded by a blue halo.

00:19:10 The fine atmosphere of the red planet contains large particles of dust,

00:19:14 which create an effect called "Mie diffusion".

00:19:17 This occurs when the diameter of the particles in the atmosphere

00:19:20 is almost the same as the wavelength of the light diffused.

00:19:24 This effect filters the red light from the sun's rays.

00:19:27 Thus, only blue light would reach your eyes on Mars.

00:19:30 How is it that the Earth has no rings?

00:19:33 All the gas giants of our solar system, Jupiter, Saturn, Uranus and Neptune, have such rings,

00:19:40 while the planets Telluric, Mercury, Venus, Earth and Mars do not.

00:19:45 There are two theories about how rings can appear around a planet.

00:19:50 They could be only remnants of material from the time when the planet was formed.

00:19:55 Or they could be the remains of a moon that was destroyed by a collision with a space body

00:20:00 or torn apart by the strong gravitational attraction of its mother planet.

00:20:04 The gas giants formed in the outer regions of our solar system,

00:20:09 while all the Telluric planets are in the interior.

00:20:12 So, maybe the interior planets were better protected from potential collisions that could have formed their rings.

00:20:18 There are also more moons in the outer regions of our solar system,

00:20:22 which could be another reason why the planets that are there have rings.

00:20:27 In addition, the larger planets have a stronger gravity.

00:20:30 This means that they can keep their rings stable after their formation.

00:20:34 Some experts think that the Earth had a ring system a long time ago.

00:20:38 An object the size of Mars could collide with our mother planet,

00:20:42 which probably created a dense ring of debris around it.

00:20:45 Some scientists think that these debris did not form a ring,

00:20:48 but what we know today as the Moon.

00:20:51 A giant planet is probably hidden on the edge of the solar system, well beyond Neptune.

00:20:56 Scientists have named this mysterious hypothetical world "the new planet".

00:21:01 If it really exists, it is probably similar to Uranus or Neptune

00:21:05 and ten times larger than our planet.

00:21:08 It is probably orbiting the Sun,

00:21:11 but in the confines of the solar system, about 20 times farther than Neptune.

00:21:16 Another interesting theory states that the new planet could actually be a black hole

00:21:21 the size of a foam bubble, which deforms space as a large planet would.

00:21:26 While we used to think that water was a rare substance in space,

00:21:30 it actually exists everywhere in our solar system.

00:21:33 For example, it can be found in asteroids and comets,

00:21:37 as well as in the craters of the Moon and Mercury.

00:21:40 We still don't know if there is enough water to make possible human colonies live,

00:21:45 if we decide to settle there.

00:21:47 But a certain amount of water is certainly present there.

00:21:50 Mars also houses water at its poles.

00:21:53 It is mainly hidden in the layers of ice and probably under the dusty surface of the planet.

00:21:58 Europe, the moon of Jupiter, also has water.

00:22:01 It is the most likely candidate we knew to welcome life outside the Earth.

00:22:06 There is probably an entire ocean of liquid water under its frozen surface,

00:22:10 and it could contain twice as much water as all the oceans of the Earth combined.

00:22:15 Neptune is surprisingly warm,

00:22:17 even if it is 30 times farther from the Sun than our planet

00:22:20 and receives less sunlight and heat.

00:22:23 But it emits much more heat than it receives.

00:22:26 Its atmosphere is also much more active than we thought.

00:22:30 Especially if we compare it to its neighbor, Uranus.

00:22:33 These two planets emit the same amount of heat,

00:22:36 even though Uranus is much closer to the Sun.

00:22:39 But no one knows why.

00:22:41 Neptune also has extremely strong winds,

00:22:44 which can reach a speed of 2,400 km/h.

00:22:47 Could it be responsible for this heat?

00:22:50 Or maybe it's because of the planet's core, or its gravitational force?

00:22:54 A monstrous black hole rushes into space at a speed of 8 million km/h.

00:22:59 Scientists have located it thanks to the Hubble Space Telescope.

00:23:03 They think it weighs as much as a billion suns.

00:23:06 It was supposed to stay in its place in the center of its original galaxy,

00:23:10 but gravitational forces push it in all directions.

00:23:13 At some point, this black hole will free itself from its galaxy

00:23:17 and continue to wander in the universe.

00:23:19 Fortunately, it is still 8 billion light years away from us.

00:23:23 Solar storms are so powerful that they could plunge us into complete darkness.

00:23:28 In July 2012, the most powerful solar storm in the last 150 years

00:23:33 nearly wiped out the Earth.

00:23:35 Mass-Ejection Coronal, or CME,

00:23:39 are large ionized gas bubbles.

00:23:42 They crossed our orbit at the time.

00:23:45 If they had been our direct target,

00:23:48 we would have faced solar matter rushing towards the Earth,

00:23:51 damaging computers and causing power outages that would have lasted months.

00:23:56 A surprise solar storm struck us on June 25, 2022.

00:24:00 A photographer even managed to capture superb light haze

00:24:04 that crossed the dawn sky in Calgary, Canada,

00:24:08 and lasted 5 minutes.

00:24:09 They were caused by the storm.

00:24:11 Vampire stars really exist.

00:24:14 They are part of a binary star system,

00:24:17 and they can literally suck the life out of the other star in the system

00:24:20 in order to continue to burn longer.

00:24:23 The idea is simple.

00:24:24 A smaller, less massive star

00:24:27 steals hydrogen from its sister to increase its own mass.

00:24:31 This vampire star then becomes warmer.

00:24:34 In addition, its color changes to a bright blue.

00:24:37 Thus, it looks much younger.

00:24:40 The color of the universe is nicknamed "Cosmic Latte".

00:24:44 The light from the galaxies and stars that are there,

00:24:47 as well as gas and dust clouds in the observable universe,

00:24:50 has a specific color.

00:24:52 It is an ivory color, quite close to white.

00:24:55 The universe is beige because there are more areas

00:24:58 that produce green, yellow and red light

00:25:01 than areas that emit blue.

00:25:03 Did you know that there is an astronomical object

00:25:06 in which space and time exchange their place?

00:25:10 But how does it work?

00:25:11 And what exactly does it mean to exchange space and time?

00:25:15 Let's try to understand.

00:25:17 Imagine that you are in a spaceship

00:25:19 that can only move in a straight line.

00:25:21 Your trajectory leads to an inevitable point

00:25:23 and you have no idea what awaits you.

00:25:26 You can only hope that it won't be too serious.

00:25:29 Meanwhile, everything around you is pure madness.

00:25:32 A chaotic assembly of historical events.

00:25:35 What do you see?

00:25:37 Ancient humans and dinosaurs?

00:25:39 The birth of the universe?

00:25:40 The future?

00:25:41 Who knows?

00:25:43 This is what the universe would look like

00:25:45 if we exchanged time and space.

00:25:47 And, in theory,

00:25:49 this is what you would see if you fell into a black hole

00:25:52 and you managed to survive.

00:25:54 But how is such a thing possible?

00:25:57 First, let's talk about time and space.

00:26:01 Imagine that you draw an electric bulb

00:26:03 on a sheet of paper.

00:26:04 Then you take another sheet

00:26:05 and you draw the way it lights up.

00:26:08 For now, it's just a small circle of light.

00:26:10 Another sheet, the circle of light gets bigger.

00:26:13 It becomes bigger and bigger

00:26:14 until, finally, it turns into a huge circle.

00:26:18 In reality, the bulb lights up in a blink of an eye

00:26:21 because the speed of light is faster than the universe.

00:26:25 But here, on our drawings,

00:26:27 we captured the propagation of light image by image.

00:26:31 We see how, over time,

00:26:32 the light has gone from a small dot to a large circle.

00:26:36 But if you stack these circles,

00:26:38 doesn't it remind you of a certain shape?

00:26:40 For example, a cone?

00:26:42 Exactly!

00:26:44 We call this a cone of light.

00:26:46 And time is the central axis of this cone.

00:26:49 Why?

00:26:50 Because light transforms from a small dot

00:26:52 to a large circle over time.

00:26:55 To remember, let's draw a time vector,

00:26:58 an arrow inside the cone.

00:27:00 It goes from the past to the future.

00:27:02 During this time, the circles represent space.

00:27:05 In space, we can move as we want,

00:27:07 in any direction,

00:27:08 up or down,

00:27:10 in zigzags and so on.

00:27:12 But no matter how many zigzags we draw,

00:27:14 we always move along the time line.

00:27:17 We can't go back,

00:27:19 and we can't stop time.

00:27:21 This helps us define time and space.

00:27:24 Time is the direction in which the cone of light is oriented.

00:27:27 It is the direction where all our paths lead,

00:27:29 and where our future is inevitably located.

00:27:32 And space is all the variety of perpendicular directions

00:27:35 along the time line.

00:27:37 This graph is very simple.

00:27:40 If it could be applied to the entire universe,

00:27:42 time would flow in the same way everywhere.

00:27:45 However, if you have seen at least a few popular science fiction movies,

00:27:49 you know that this is not the case.

00:27:51 In reality, time can be a lot of work.

00:27:54 For example, if you relax near a black hole,

00:27:57 what will only be two hours for you

00:27:59 can turn out to be 20 years for your friend on Earth.

00:28:02 But why?

00:28:04 Take a deep breath.

00:28:05 Now gravity comes into play.

00:28:07 You probably think that it is simply this force

00:28:09 that helps us to stay on the ground.

00:28:11 But it is much, much more complex than that.

00:28:15 Gravity is one of the basic physical forces of our world.

00:28:19 And it is incredibly powerful.

00:28:21 It is even so powerful that it can distort space and time.

00:28:26 It can literally influence the speed of time

00:28:28 like a powerful wizard.

00:28:30 How?

00:28:31 To understand it,

00:28:32 let's take something slightly bigger than a light bulb.

00:28:35 For example, a supernova.

00:28:38 Somewhere in the universe, a star has just exploded.

00:28:41 How do we know?

00:28:43 Nothing in the universe.

00:28:44 No sound, no radio wave.

00:28:46 Nothing travels faster than light.

00:28:49 So we only become aware of the birth of a supernova when we see it.

00:28:54 And this only happens when its light cone grows sufficiently

00:28:57 and reaches our planet.

00:28:58 So the light cone grows and grows.

00:29:01 So far, everything is fine.

00:29:03 And finally, it reaches our planet.

00:29:05 But there is a hitch.

00:29:07 Our planet is massive.

00:29:09 Very massive.

00:29:11 And it has a fairly strong gravity.

00:29:13 So what happens?

00:29:14 Gravity changes the direction of the light cone.

00:29:17 It begins to pull the cone towards the center of our planet.

00:29:20 And with it, it also pulls our arrow of time.

00:29:24 This means that it slows down time.

00:29:26 And the closer the light cone is to us,

00:29:28 the more the arrow bends.

00:29:30 And the more time slows down.

00:29:32 What does that mean?

00:29:34 It means, for example, that a watch around your ankle

00:29:37 will be slower than a watch on your wrist.

00:29:40 That your head ages faster than your legs.

00:29:42 And that astronauts in Earth orbit age a little slower than people on Earth.

00:29:47 This is what scientists call general relativity.

00:29:51 OK.

00:29:52 But what is the relationship with our subject?

00:29:54 How can we understand what will happen if we exchange space and time?

00:29:58 Don't worry, we'll get there.

00:30:01 Now imagine a cosmic body with incredibly strong gravity.

00:30:05 It deforms time and space so much that it feels like it's exchanging.

00:30:09 It's a black hole.

00:30:11 It pulls absolutely everything to its center.

00:30:14 No star, no planet, no light can escape it.

00:30:19 Let's say our light cone is approaching it.

00:30:22 First, as usual, time begins to bend towards the center of the black hole,

00:30:26 attracted by its gravity.

00:30:28 But gravity is very strong.

00:30:30 So it bends more and more.

00:30:32 And time goes slower and slower as you get closer to the center.

00:30:36 At the end, the light cone crosses the limit of the black hole,

00:30:39 what is called the horizon of events.

00:30:42 At that moment, it has deformed so much that now it is literally pointing down.

00:30:47 We can say that time has changed its direction.

00:30:51 Time is pointing down.

00:30:53 What is this absurdity?

00:30:55 It will be easier to explain with a real example.

00:30:58 Imagine that you are a crazy astronaut who decided to jump into a black hole.

00:31:03 And there is an observer in a spaceship watching you do that.

00:31:07 At first, for you, nothing changes.

00:31:10 Look at your watch.

00:31:11 You see that 5 seconds have passed.

00:31:13 Everything is fine.

00:31:15 But what happens to the observer?

00:31:17 First of all, you will fall for a very long time.

00:31:20 The observer has been sitting there for 50 years.

00:31:23 And you always fall because your time has slowed down.

00:31:27 Secondly, as space is also deformed near a black hole,

00:31:31 the observer will see that you will start to stretch like a spaghetti.

00:31:35 It is a scientific term, by the way, which bears the name of "spaghetti-ification".

00:31:40 And then you finally cross the horizon of events.

00:31:43 The observer no longer sees you.

00:31:46 Light cannot escape a black hole,

00:31:48 so your image will not reach the observer, even if you are still inside.

00:31:52 And what happens to you?

00:31:54 And if you survived one way or another,

00:31:57 remember that the arrow of time points to the center of the black hole.

00:32:00 This means that now the center of the black hole is your future.

00:32:05 It is not a place.

00:32:07 It is a destiny that you cannot change.

00:32:10 And the place where you come from, as well as the rest of the universe,

00:32:13 no longer exists for you.

00:32:15 Because now it is not a place, but an event of the past.

00:32:20 And since you cannot go back in time, you will never be able to come back.

00:32:24 But what is around you?

00:32:26 A complete chaos.

00:32:28 The rays of light are now moving in all directions, forward, backward, and so on.

00:32:33 The rays representing the events of the past, the future, the present,

00:32:36 all of this is moving around you.

00:32:38 In reality, space and time have not exchanged their places.

00:32:42 But it seems that they have.

00:32:44 Because in space, you can only move forward,

00:32:47 as if you were following a straight line.

00:32:49 And the time reflected in the rays of light

00:32:51 revolves around you and moves in all possible directions.

00:32:56 And here we return to the beginning.

00:32:58 This horrifying example helps us to imagine

00:33:00 what we would feel if time and space were reversed.

00:33:05 Of course, all of this is only theory and assumption.

00:33:08 The very idea that we are moving in a direction,

00:33:10 the one we have not chosen,

00:33:12 and that there is a complete temporal chaos around

00:33:14 seems quite frightening.

00:33:17 And yet, it would be a very interesting experience.

00:33:21 Are you in?

00:33:23 The magnetic field of the Earth hides a fascinating story.

00:33:30 It turns out that it weakens day after day.

00:33:34 In fact, this has been happening for the last 3,000 years.

00:33:38 And if this trend continues,

00:33:40 we could experience it in a millennium.

00:33:45 But then, what happens?

00:33:47 Well, imagine this.

00:33:49 The magnetic north becomes the south, and vice versa.

00:33:52 It seems crazy, doesn't it?

00:33:54 When this happens, the magnetic shield

00:33:56 that protects our planet can weaken,

00:33:58 allowing more cosmic rays to hit us.

00:34:02 These high-energy cosmic particles

00:34:04 can cause malfunctions in the electronics of our satellites

00:34:08 and cause all kinds of disasters.

00:34:12 The last time such a polarity reversal occurred

00:34:16 was between 772,000 and 774,000 years ago.

00:34:21 Fortunately, humanity can count on its most intelligent members

00:34:24 to be interested in the history of the Earth's magnetic field.

00:34:28 We take carotid sediments from the ocean floor

00:34:31 and study the magnetization of fossils

00:34:33 to determine when these upheavals occurred in the past

00:34:36 and when they could occur again.

00:34:40 Another group of researchers studies the South Atlantic anomaly.

00:34:45 A vast region where the Earth's magnetic field

00:34:47 is about three times weaker than it is at the poles.

00:34:51 By using the data of several satellites,

00:34:53 they try to determine what causes this anomaly

00:34:57 and how it could evolve in the future.

00:35:00 This could give us an overview of how a weakened magnetic field

00:35:04 can affect our satellites and our planet.

00:35:07 Of course, our generation will not be there to witness these changes,

00:35:11 but it still makes us wonder

00:35:13 what this planet could look like upside down,

00:35:16 magnetically speaking, of course.

00:35:19 NASA astronomers have also announced that in 4 billion years,

00:35:23 our Milky Way galaxy will experience a spectacular shatter.

00:35:27 After a cosmic collision that will shake everything,

00:35:30 we are not talking about a small, unconsequential clutch,

00:35:33 but a titanic collision with our neighbor,

00:35:36 the Andromeda galaxy.

00:35:39 Humanity will have to cramp up on the cows' floor for this,

00:35:43 because our sun could be projected into a new region of the galaxy.

00:35:47 However, the Earth and our solar system

00:35:50 should not be seriously affected.

00:35:53 It seems hard to believe.

00:35:55 So, how is this done?

00:35:57 The Hubble Space Telescope has taken rigorous measurements

00:36:00 of Andromeda's movements.

00:36:02 Although the galaxies are destined to collide,

00:36:05 the stars inside each are so far apart from each other

00:36:09 that they should not collide with other stars during the event.

00:36:13 Nevertheless, the stars will be projected into different orbits

00:36:16 around when we go to the central galaxies.

00:36:19 According to the simulations, our solar system

00:36:22 will probably eject a lot more alloy from our galactic yao

00:36:26 than it does today.

00:36:28 Now, you can arrange your telescopes.

00:36:31 No need to count the years.

00:36:33 The event is planned to happen in about 4 billion years.

00:36:36 So, the chances for us to witness it are non-existent.

00:36:40 Saturn loses its rings.

00:36:42 Fortunately, we will not be there to witness this sad event either.

00:36:46 Apparently, these rings,

00:36:48 under the influence of Saturn's magnetic field,

00:36:51 are attracted to it in the form of ice particles' rain.

00:36:55 According to NASA's research,

00:36:58 this rain of rings

00:37:00 drains an amount of water that could fill

00:37:03 an Olympic swimming pool every half hour.

00:37:06 The whole system of Saturn's rings

00:37:09 will probably disappear in 300 million years.

00:37:12 Scientists think that we are rather lucky

00:37:15 to be able to observe Saturn's rings at the present time

00:37:18 because they seem to be in the middle of their lifespan.

00:37:21 But if you consider that the rings orbiting around the planets

00:37:24 are all temporary,

00:37:26 there is therefore a chance that we have simply missed

00:37:29 Jupiter's majestic rings

00:37:31 or Uranus and Neptune's.

00:37:33 These planets today only have tiny rings around them.

00:37:38 Scientists have been debating for a long time

00:37:42 whether Saturn was formed with these rings

00:37:45 or if the planet acquired them later in its existence.

00:37:48 New research tends to favor the second scenario,

00:37:52 indicating that they are unlikely to have more than 100 million years,

00:37:56 while Saturn itself has about 4.5 billion.

00:38:00 What could have caused the appearance of these rings in the first place?

00:38:04 Well, there are some theories.

00:38:06 One of them suggests that the rings could have formed

00:38:10 when small satellites ice in orbit around Saturn collided.

00:38:15 Perhaps because their orbits had been disturbed

00:38:17 by the gravitational attraction of an asteroid or a comet.

00:38:21 Who knows what humans could look like in the future?

00:38:24 It is unlikely that we will observe major changes in our lives.

00:38:28 But let's take a step back in the future

00:38:30 and think about what we could become.

00:38:33 We would become cyborgs with all kinds of cybernetic implants,

00:38:37 new metamorphic cells and special biological and artificial beings.

00:38:43 To understand our future evolution,

00:38:45 we must take a look at our past.

00:38:48 A million years ago, Homo sapiens did not even exist.

00:38:52 There were some similar species, like the Neanderthal man.

00:38:56 If we look back to today,

00:38:58 humans have become bigger and more robust.

00:39:01 But maybe in the future we will become smaller to save energy,

00:39:06 because we predict that our planet will be more and more populated.

00:39:10 Speaking of overpopulated planets,

00:39:13 living in these new conditions means that we will have to adapt,

00:39:17 and quickly.

00:39:18 We interact constantly with a lot of people,

00:39:21 and remembering everyone's names becomes a crucial skill.

00:39:25 Fortunately, technology could help us with brain implants

00:39:29 that will improve our memory.

00:39:31 In the future, we could also use more visible technologies

00:39:35 that will be an integral part of our appearance.

00:39:38 Imagine having a bionic eye

00:39:40 with a camera capable of visualizing different wavelengths.

00:39:44 Although predicting a million years in the future is pure speculation,

00:39:49 we can use bioinformatics

00:39:51 to make some predictions about our near future.

00:39:54 Demographic trends suggest that urban areas

00:39:58 will have a greater genetic diversity,

00:40:00 while rural areas will become less and less diversified.

00:40:04 And what about space?

00:40:06 If we end up colonizing Mars,

00:40:08 our bodies could be altered by low gravity.

00:40:11 Maybe we'll develop longer arms and legs,

00:40:14 or even isolated hairs like our Neanderthal cousins.

00:40:18 In the future, our moon will also undergo some dramatic changes.

00:40:22 We won't see our living being there either.

00:40:25 In about 5 billion years,

00:40:27 this corner of the universe will experience major changes.

00:40:30 For now, our sun is quietly in its main sequence phase.

00:40:35 It's just burning hydrogen as if nothing happened.

00:40:39 In the future, during its red giant phase,

00:40:41 the sun will swell like a boulder,

00:40:44 until its atmosphere reaches and engulfs our dear Earth and its moon.

00:40:49 Our natural satellite, which is already moving away from Earth,

00:40:52 will be profoundly disturbed by the influence of the sun.

00:40:56 Its orbit will be so disturbed that it will end up closer to Earth

00:40:59 during the phase of the new moon than during the full moon.

00:41:02 And it's not the worst!

00:41:04 If we leave it alone, the moon will continue to move away from Earth

00:41:08 until it needs nearly 50 days to orbit us.

00:41:13 As the sun continues its own journey,

00:41:16 its atmosphere will impact the moon and cause its orbit to degrade.

00:41:20 In the end, the moon will be pulverized into a magnificent ring of debris

00:41:24 gravitating around the Earth.

00:41:27 We are talking here about all these mountains,

00:41:29 these craters, and even footprints,

00:41:32 and other flags that we left there,

00:41:34 all scattered through the field of debris.

00:41:36 There is a chance that the sun will lose enough mass

00:41:39 to spare the Earth and the moon from total annihilation.

00:41:42 Or, if we are really lucky,

00:41:44 the sun will lose 20% of its mass and we will be "safe and sound".

00:41:48 All this is only theory for the moment,

00:41:50 because we have never observed red giant stars during this phase.

00:41:55 The universe itself could one day become completely dark.

00:41:58 Scientists cannot predict it with absolute certainty,

00:42:02 but they can make some assumptions.

00:42:05 Currently, our universe is 13 times older than 77 billion years,

00:42:10 and it continues to produce new stars from right to left.

00:42:14 It is said that finally, after about a billion years,

00:42:18 the last star will be born.

00:42:21 This last star will be small, a red dwarf,

00:42:24 barely a fraction of the size of our sun.

00:42:27 These stars are champions in terms of longevity.

00:42:30 They slowly absorb their hydrogen to feed the fusion reaction of their nuclei.

00:42:36 But even these last stars cannot last as an element.

00:42:39 They quickly reach about 100 billion years,

00:42:43 and the last light is fading.

00:42:45 The universe will be dark and lonely.

00:42:48 But, curiously, we will not be there for all of you if we go.

00:42:52 The day of the announcement.

00:42:58 Hello everyone and welcome to my space-dedicated vlog.

00:43:02 I am very excited because I have a big announcement to make.

00:43:05 After years of training,

00:43:07 the day I have waited for all my life has finally arrived.

00:43:11 I have always dreamed of being one of the 350 people

00:43:14 sorted on the fly to become NASA astronauts.

00:43:17 And here is a funny fact.

00:43:19 The 7 original astronauts of the Mercury project

00:43:22 are the ones who have drawn this list.

00:43:25 So we can say that I am part of a very select club.

00:43:28 But the good news is that I have finally finished with the virtual reality workshops

00:43:33 and that I am really going to go into space.

00:43:35 There are so many things I have to accomplish to prepare for my first mission,

00:43:40 so I will make sure that today's vlog is short.

00:43:43 But wait to hear about my space adventures in the next few days.

00:43:48 The day before launch.

00:43:50 One might think that the day before the launch is very busy for the crew, right?

00:43:55 But in fact, it's a rather relaxed day in terms of things to do.

00:43:59 As the days to come are going to be tough,

00:44:02 NASA allows us to spend time with family members or close friends

00:44:07 who have been allowed to keep us company during our quarantine before the launch.

00:44:11 We can also stay in a beach house that belongs to the space agency.

00:44:16 Is it a dream job or what?

00:44:18 But the most important thing that we are advised to do on this day

00:44:21 is to have a good night's sleep.

00:44:23 Finally, as far as possible, but no pressure.

00:44:26 So that's what I'm going to try to do now.

00:44:29 So to bed.

00:44:30 Fortunately, we were forbidden to drink coffee 24 hours before the launch.

00:44:35 Otherwise, I bet that with all this caffeine, I would spend the night counting sheep.

00:44:40 The day before launch.

00:44:42 Today is day J.

00:44:45 First of all, although it is one of my favorite songs,

00:44:48 I try to avoid listening to Space Oddity by David Bowie

00:44:51 because no one wants to spoil everyone's morale.

00:44:55 Secondly, coffee is still not allowed for breakfast on the morning of the launch

00:45:00 due to its heuristic properties.

00:45:03 Having to go back and forth to the toilet can be a real problem

00:45:07 when you're strapped in a space-oriented cockpit.

00:45:10 You see?

00:45:11 It may seem surprising, but these precautions put aside,

00:45:16 astronauts have a fairly long time before the launch.

00:45:20 Before we go on the launch pad, we do a final check

00:45:25 and we go to the toilet for one last pee.

00:45:28 Then it's time to get in the cockpit.

00:45:31 Many of us take a nap inside

00:45:34 because the computer system performs thousands of tests before launch,

00:45:38 including air-ground vocal checks with the different control centers.

00:45:43 And here's another funny fact.

00:45:45 We all wear adult diapers during this period, just in case.

00:45:50 Okay, let's stop talking about our little commissions for the moment.

00:45:54 Now that everything is ready, it's time to start the main engine.

00:45:58 Get ready for takeoff.

00:45:59 5, 4, 3, 2, 1.

00:46:03 To infinity and beyond!

00:46:05 One day in space.

00:46:08 Welcome to space.

00:46:09 I would have taken you for a little tour of the owner.

00:46:13 But here it is already quite difficult to distinguish the top from the bottom.

00:46:17 Ha ha ha!

00:46:18 First of all, every minute and every second of an astronaut's day in space is planned.

00:46:23 Whether it's eating, brushing your teeth, working or sleeping,

00:46:27 each of our gestures is part of a strict schedule.

00:46:31 The tasks we have to accomplish are divided into 5-minute sections

00:46:35 by a team from the mission control center, also called Ops Planner.

00:46:40 This planning is crucial because it allows us to know exactly what is happening

00:46:45 and what is involved in what at a given moment on the space station.

00:46:49 But don't worry.

00:46:51 It's not all work, work, work.

00:46:53 Even if these activities are also part of our planning, we still have free time.

00:46:59 The concept of a day aboard a space ship in orbit is a little different

00:47:04 from what one might imagine.

00:47:07 Every 24 hours, astronauts aboard the International Space Station

00:47:11 watch 15 sunrises and sunsets as the station moves around the world.

00:47:17 But for millions of years, humans have been following a daily cycle of 24 hours.

00:47:22 Our brain and our body follow the circadian rhythm of waking and sleeping.

00:47:28 This is why astronauts work, sleep and work according to similar schedules

00:47:32 that correspond to these cycles.

00:47:34 Because any other rhythm would make us live in a state of permanent time lag.

00:47:39 A working day is about 6 to 9.30 hours, Greenwich time,

00:47:44 and includes 3 meals and 2.5 hours of exercise.

00:47:48 The morning ritual.

00:47:51 Our use of time in space is similar to that we have on Earth.

00:47:57 We are awakened by a ring and we wash ourselves with the products

00:48:01 provided by NASA in our toilet kits.

00:48:04 These are, in particular, shampoos without rinsing, which require very little water,

00:48:09 since there is no real shower in weightlessness.

00:48:12 What's funny is that the water we use floats throughout the process.

00:48:17 Each of us is allowed to carry the products of his choice in this bag,

00:48:22 including cosmetics and toothpaste.

00:48:25 There are razors to shave, shavers or scissors to cut your hair if necessary.

00:48:31 We just have to make sure to wash our hair

00:48:34 so that it won't fly everywhere later while we work.

00:48:38 Food.

00:48:40 We don't skip breakfast.

00:48:42 It's the first of our three meals, followed by lunch, then dinner.

00:48:47 The amount of food we ingest depends on the needs in calories of each.

00:48:52 What's good is that there is no need to cook or do the dishes,

00:48:56 because meals are already prepared on Earth and presented in disposable packages.

00:49:01 It should be noted that space food has considerably improved in terms of variety and taste

00:49:06 since the Apollo missions, during which astronauts have consumed

00:49:10 only lyophilized food for days.

00:49:13 Work in space.

00:49:15 After eating, it's time to get to work.

00:49:18 Each of us is assigned tasks for the day.

00:49:22 These range from experience supervision to daily maintenance of the station's equipment.

00:49:27 Our job is also to manage projects controlled from Earth

00:49:31 and to subject ourselves to experiments to determine to what extent

00:49:35 our body adapts to life in absenteeism for long periods.

00:49:40 The space gym.

00:49:43 Exercising is an essential part of our day.

00:49:46 We actually devote hours every day to our fitness.

00:49:50 Normally, on Earth, our body is constantly active

00:49:54 because it fights against gravity to move.

00:49:57 But in space, where gravity is almost non-existent,

00:50:00 movements are more comfortable and do not require much effort or energy.

00:50:04 Thus, astronauts who spend long periods in space without continuing to train physically

00:50:10 lose a lot of muscle mass, which weakens them once they return home.

00:50:15 This is why it is vital for us to stay active physically

00:50:19 to prevent these bone and muscle losses.

00:50:23 This also helps to mitigate what we call "space swelling",

00:50:27 which is caused by the accumulation of bodily fluids in the skull

00:50:31 because they are no longer attracted to the bottom by gravity.

00:50:34 Our options in terms of regular exercise include cardio on a treadmill or a bike,

00:50:39 we also do weight training.

00:50:43 And to get used to all this, we have to get attached to the exercise machines

00:50:47 because without them we would float like bumblebees and our efforts would be useless.

00:50:52 Free time.

00:50:54 The organizers of the Earth mission plan a little time every day

00:50:58 to allow us to relax and have fun in space.

00:51:01 This is the time when we write our emails, watch movies or play an instrument.

00:51:06 But to be honest, the most popular hobby in the station

00:51:10 is to watch the Earth scroll under our eyes through the window.

00:51:13 There are also the spectacular sunrises and sunsets

00:51:16 that occur every 45 minutes while we are in orbit.

00:51:20 So we can say that we don't have time to get bored.

00:51:23 Besides, just like the earthlings, we also have weekends to resource ourselves.

00:51:27 Everyone in bed.

00:51:30 It is important to sleep well in order to have energy for the tasks of the day after.

00:51:34 However, in space, we cannot climb in our little bedside beds.

00:51:39 Instead, we have sleeping bags that are fixed to the wall to protect us.

00:51:44 If it wasn't, we would float all night, which is neither safe nor relaxing.

00:51:49 Well, I have to go on that. See you next time.

00:51:53 Two images change quickly before your eyes.

00:51:57 Our huge planet and a black void.

00:52:00 The image of the Earth becomes smaller and smaller every second.

00:52:04 You fly from the space ship into the infinite void and you don't know what to do.

00:52:09 The International Space Station flies 400 km above the surface of the Earth.

00:52:16 A spacewalk is a routine activity for the astronauts who work there.

00:52:20 To date, they have already spent more than 11,000 hours in the abyssal space.

00:52:25 But, luckily, no one has ever flown there.

00:52:29 As we could see in the cinema.

00:52:31 Unfortunately, the astronauts are faced with other dangers, no less terrible,

00:52:35 when they go out into space.

00:52:38 One of these accidents occurred in 1966.

00:52:45 Eugene Cernin put on his back reactor and left the station to carry out repair work.

00:52:51 The reactor, which allowed our astronaut to fly in weightlessness, heated a lot.

00:52:56 Eugene had put on a special metal protective pants.

00:53:00 But this protection was not enough when he left.

00:53:04 Instead of removing the heat, the pants began to heat up.

00:53:09 The suit was heavy and uncomfortable, like an armor.

00:53:13 It rubbed against his skin and limited his movements.

00:53:17 Working in weightlessness is very tiring.

00:53:21 And that day, Eugene also had to face this suit problem.

00:53:25 Inside it, he felt like he was in a hot bath.

00:53:29 The high temperature and the intense work made him extremely tired, dehydrated,

00:53:34 and he lost a lot of weight.

00:53:36 His face was sweating and the sweat blinded him.

00:53:39 During this trip, our astronaut lost about 6 kg.

00:53:44 His comrades came to his rescue and brought him back aboard the shuttle.

00:53:50 To limit overheating, they sprinkled him with cold water using a pipe.

00:53:55 To go out into infinite space,

00:53:57 astronauts had to wear a suit that was like a cage for their bodies.

00:54:02 Another dangerous incident occurred in 1973.

00:54:11 Two astronauts, Pete Conrad and Joe Kerwin,

00:54:14 went out into space to repair a solar wing of the Space Station Skylab.

00:54:20 The wing was no longer spinning,

00:54:22 and the astronauts tried to move it manually.

00:54:25 Using force, they managed to unhook it, but the wing pushed them back.

00:54:30 And the thrust was so strong that it threw the two astronauts far away.

00:54:35 They didn't have time to cling to anything and flew into space.

00:54:40 Fortunately, they were equipped with safety cables.

00:54:43 Thanks to them, the astronauts were able to return to Bonport.

00:54:48 In an ordinary modern space suit, there are more than 10 layers of protection.

00:54:54 Such a suit protects against extremely cold and hot temperatures.

00:54:58 It is tear-resistant and does not allow moisture to pass.

00:55:02 This protection is necessary to avoid depressurization.

00:55:07 If there is any space between your body and the outside,

00:55:10 all oxygen will start to escape the suit.

00:55:13 The more oxygen the suit loses, the more the vacuum is felt.

00:55:17 This can have terrible consequences,

00:55:20 such as asphyxia and increased body volume.

00:55:23 It's like you're starting to swell from the inside.

00:55:27 In 2007, Rick Mastracchio went out into space to make some repairs.

00:55:33 But there was a hole in his left glove, near his thumb.

00:55:36 It was on the outside layer of the glove.

00:55:39 And the worst part is that the astronaut hadn't noticed it.

00:55:42 He continued to work normally.

00:55:44 But a damaged first layer can lead to the deterioration of the second,

00:55:49 and then that of the third.

00:55:51 And so on, until the vacuum reaches the astronaut's skin.

00:55:56 Rick had to work six hours in space.

00:56:01 But during the four-hour, he noticed the damage to his space suit.

00:56:06 The astronaut reported it to the command and received the order to return to the ship.

00:56:11 He never knew how the hole had appeared.

00:56:14 Inside the ISS, there are many chemical products necessary for space work.

00:56:22 For example, ammonia has the property of freezing almost any surface.

00:56:27 This chemical gel is used to cool some components in the event of overheating.

00:56:32 The escape of this substance in the ISS is practically impossible.

00:56:36 That's exactly what the experts had told Robert Curbiam during the training before his first flight into space.

00:56:43 And an accident happened on his first trip out in 2001.

00:56:47 Robert was working outside the space station when there was an ammonia leak.

00:56:54 The liquid splashed his suit.

00:56:57 A thick layer of ice quickly covered the glass of his helmet.

00:57:01 Robert couldn't see anything anymore.

00:57:03 He thought he had broken something, but the accident wasn't his fault.

00:57:08 Thanks to the protective layer of his suit, he couldn't freeze.

00:57:12 But the ammonia strongly limited his movements.

00:57:15 The main problem was that he couldn't return to the ship.

00:57:19 The substance could penetrate the station, which could cause an even more serious accident.

00:57:24 So he had to stay in space for an hour and a half, waiting for the leak to decrease.

00:57:29 After that, he was able to return to the station.

00:57:33 To realize the difficulty of working in space, you have to understand what a space suit is.

00:57:40 It weighs 120 kg, or as much as a scooter.

00:57:44 You won't feel its weight in absenteeism, but it will still make you sweat.

00:57:49 Astronaut Chris Hadfield described it as follows.

00:57:52 Each movement inside a space suit encounters a resistance.

00:57:56 The suit scratches your skin, compresses your bones and joints, and forces you to spend twice as much energy for simple movements.

00:58:04 In such conditions, you start to sweat and your eyes are wet.

00:58:08 This humidity floats in your helmet and blinds you, then it evaporates.

00:58:13 But if there is too much humidity, it can threaten the life of an astronaut.

00:58:18 Such a case occurred in 2013 with astronaut Luca Parmitano.

00:58:23 He went out into space to measure something outside the station.

00:58:27 At one point, he felt that the back of his head was wet.

00:58:31 He informed the others and received the order to return.

00:58:35 To return, Luca had to turn around, head down.

00:58:40 As soon as he did, water splashed into his helmet.

00:58:43 His face was almost entirely covered in it.

00:58:46 He could neither see nor hear.

00:58:49 He tried to report the problem to the base, but the water was also covering his mouth.

00:58:54 Fortunately, his comrades rescued him and brought him back to the station.

00:58:58 When they opened his helmet, nearly two liters of water spilled.

00:59:02 Cables are very effective in preventing astronauts from flying away.

00:59:08 But what would happen if one of them broke during a violent shake?

00:59:13 Or because it was not well attached?

00:59:16 For better protection, there is a system called "SAFER",

00:59:20 simplified for extravehicular exits.

00:59:23 It's like a dorsal reactor.

00:59:26 Gases escape from these small tubes to change the direction of your flight.

00:59:30 If you spin in space, this system stops and adjusts your movements.

00:59:34 You can control it with a special joystick.

00:59:37 The SAFER was first used in 1984.

00:59:43 But before the engineers created it, there was the MMU.

00:59:48 The Crew Maneuvering System.

00:59:51 In 1984, astronaut Bruce McKendless used it for the first time.

00:59:57 You may have seen this famous photo where he floats without a cable in space.

01:00:02 The problem is that Bruce was the first to test such a dorsal reactor.

01:00:06 He was not 100% sure it would work.

01:00:09 He went out into space and unplugged his cable.

01:00:12 Nothing held him back and he could fly into infinity.

01:00:15 His crew could not have saved him.

01:00:18 Imagine how scary it must have been.

01:00:20 Fortunately, the reactor worked.

01:00:22 However, after three missions, NASA decided not to use the MMU anymore.

01:00:27 Because there were risks.

01:00:29 After this experience, the engineers invented the SAFER.

01:00:33 The propellers and cables are very reliable.

01:00:36 But the best protection for an astronaut is his skills.

01:00:40 Astronauts study for six years, then spend several years following a specialized training.

01:00:46 They all spend many hours training thanks to simulation programs.

01:00:51 They train their body, their endurance and their mind because,

01:00:55 in a space as dangerous as it can be, it is essential to know how to keep calm.

01:01:07 Imagine a place where a single day lasts longer than a whole year.

01:01:11 On Venus, a day, that is to say a complete rotation on its axis,

01:01:15 is as long as 243 days on Earth.

01:01:18 And what is even stranger, despite the fact that Venus knows one day without end,

01:01:23 is that its year is shorter than that of Earth.

01:01:26 While Earth takes about 365 days to make a complete orbit around the sun,

01:01:31 Venus does it in only 225 days.

01:01:34 So, in a way, for Venus, a day is more significant than a whole year.

01:01:39 Venus is a strange planet in general.

01:01:42 It is nicknamed "the twin of the Earth" because of our similarities.

01:01:46 Although it is a little smaller than our planet,

01:01:49 there are also drastic differences.

01:01:52 For example, it rotates in the opposite direction,

01:01:55 which means that the sun rises in the west and sets in the east.

01:01:59 And Venus is not the only one to dance to its own rhythm.

01:02:03 Uranus does the same.

01:02:05 And finally, it's a bit of madness on Venus in terms of atmosphere.

01:02:08 When you are standing on Earth, you don't really feel the weight of the air around you.

01:02:13 Well, on Venus, this feeling would be comparable to an elephant sitting on your shoulders.

01:02:18 Venus has an atmospheric pressure 90 times higher than that of Earth.

01:02:23 The atmosphere there consists of a thick layer of toxic gases.

01:02:26 For example, the carbon dioxide that is released by all volcanoes.

01:02:30 It applies an incredible pressure.

01:02:32 This is translated by incredibly high temperatures.

01:02:35 It is therefore surprising that we still have to wait

01:02:38 before we can set foot on this planet one day.

01:02:41 Meanwhile, Mercury, the closest planet to the sun,

01:02:45 has an orbit even shorter than that of Venus.

01:02:48 It makes a full journey around the sun in only about 88 Earth days.

01:02:52 However, it has a slow rotation on its axis,

01:02:55 which means that one day on Mercury lasts about 176 Earth days.

01:03:00 Basically, half a year for us.

01:03:02 Just like with Venus, a day lasts much longer than a year.

01:03:06 As it is the closest planet to the sun,

01:03:08 it is not surprising that Mercury knows extremely high temperature variations.

01:03:13 During the day, these can exceed 420 ° C, enough to melt lead.

01:03:18 But wait for the sunset.

01:03:20 At night, it goes down to a glacial -180 ° C.

01:03:24 It's because Mercury doesn't have a thick atmosphere like ours,

01:03:27 so the heat doesn't spread evenly across the planet.

01:03:31 If one side is plunged into darkness, it will be extremely cold,

01:03:35 and the other side will be burning.

01:03:37 Just like if you left an ordinary big rock under the sun for a moment.

01:03:42 In fact, it's so cold that there could even be ice on it.

01:03:46 Look at the region of the northern pole of the planet.

01:03:48 Especially these yellow spots, lit by the sun inside the craters.

01:03:52 They may indicate the presence of water ice.

01:03:55 But it turns out that water is much more common in space than we thought.

01:03:59 Mars is often nicknamed "the red planet".

01:04:02 It owes its nickname to the abundance of iron oxide, or rust, which covers its surface.

01:04:07 The rich iron minerals create this reddish hue that colors the Martian landscape.

01:04:11 But it turns out that Mars is not just red.

01:04:14 If you stand on Mars, you will see a land similar to a desert of caramel colors,

01:04:19 bathed in a golden glow, a little bit of brown here and there, and even slight greenish reflections.

01:04:25 Mars also has the largest mountain in the entire solar system, Olympus, Mons.

01:04:30 At a dizzying height of about 22 km above sea level, it is much higher than Mount Everest.

01:04:35 It was formed by the eruption of a lava with low viscosity,

01:04:39 creating a structure similar to a shield.

01:04:42 Since Mars is covered with sand, it is also famous for its fantastic dust storms.

01:04:47 But it turns out that they are even more insane than we thought.

01:04:51 These storms can last months.

01:04:54 Although they may present challenges for future human missions,

01:04:58 they also contribute to the unreal aspect of the planet when it is observed from afar.

01:05:03 And it is not only the storms to take into account, but also the earthquakes of Mars.

01:05:07 Also known as seismic tremors, they were detected for the first time by NASA in 2019.

01:05:14 Unlike earthquakes, which are often triggered by tectonic plates,

01:05:20 we think that the tremors of Mars result from the cooling and contraction of the planet's interior.

01:05:26 It is interesting to see how similar and yet so different the two planets are.

01:05:32 Saturn's emblematic rings could hold a secret linked to the ancient past of the Earth.

01:05:37 These rings are mainly composed of ice particles and debris

01:05:41 and are estimated to be relatively young on a cosmic scale, only a few hundred million years old.

01:05:47 Now, some theories claim that they were born after a large-scale disaster.

01:05:52 The collision of two large moons or the disintegration of a comet, for example.

01:05:57 What is interesting is that this chronology coincides with the age of the extinction of dinosaurs on Earth.

01:06:03 Would there be a link? Who knows.

01:06:05 In fact, although Saturn wins the big prize for its rings,

01:06:08 it is not the only planet in our solar system to have them.

01:06:12 Jupiter, Uranus and Neptune also have their own sets of rings,

01:06:16 although they are perhaps not as visible and impressive as those of Saturn.

01:06:21 However, there is something by which Saturn really stands out.

01:06:25 The magnificent hexagon of its north pole.

01:06:28 It is a colossal figure with six sides.

01:06:30 And each side of this incredible structure measures about 14,500 km long.

01:06:36 That is 1,900 km more than the diameter of the Earth.

01:06:40 Scientists are not sure how this hexagon was formed or why.

01:06:45 They think that this could be due to variable wind speeds.

01:06:49 Or maybe it is shaped by a localized, slow and sinuous jet stream.

01:06:54 For the moment, it remains another of Saturn's mysteries.

01:06:58 Just like Saturn's hexagon, Jupiter also has its own strange spot.

01:07:02 It is called the Great Red Spot.

01:07:04 It is a storm that has been raging for at least 350 years and is larger than the Earth itself.

01:07:10 Despite its name, the color of this point has varied over the years,

01:07:14 ranging from brick red to pale salmon pink.

01:07:17 Scientists continue to study this tenacious storm,

01:07:20 unraveling the mysteries of its persistence and its changing volutes.

01:07:24 On the meteorological level, the Great Red Spot is a real epicenter.

01:07:29 It generates enormous pressure in the southern hemisphere of Jupiter.

01:07:33 During this time, Jupiter itself is not alone in terms of magnetic fields.

01:07:38 Its influence is colossal.

01:07:40 It extends far beyond the planet itself

01:07:43 and creates one of the most vast and powerful magnetic fields in our solar system.

01:07:48 Because of this, Jupiter is an intense source of radiation and fascinating auroras.

01:07:54 While the auroras of the Earth's Boreal are breathtaking, Jupiter also has something to offer.

01:08:00 Its magnetic field interacts with charged particles from the moons of Jupiter and solar wind.

01:08:06 This creates visually striking auroras at the level of its poles.

01:08:11 However, compared to the Earth, the scale of these auroras is phenomenal.

01:08:15 Nothing compares to what we observe on our planet.

01:08:19 But even this type of Great Red Spot is not a unique feature within our solar system.

01:08:25 The stormy giant Neptune, the eighth and farthest from the planets of the Sun,

01:08:31 also has its own Great Dark Spot.

01:08:34 Just like with Jupiter, it is a huge vortex in the middle of Neptune's atmosphere.

01:08:39 But unlike its Jupiterian counterpart, this spot tends to appear and disappear

01:08:44 due to Neptune's extremely changing and dynamic weather.

01:08:49 Neptune, like Uranus, is another frozen giant.

01:08:53 And just like the other giants, it has some of the most violent winds in our solar system.

01:08:59 Its supersonic currents can reach speeds of over 1,900 km/h.

01:09:05 Yes, it's not funny.

01:09:07 But this explains its thick cloud formations.

01:09:10 In fact, if you have ever dreamed of a planet where it rains diamonds,

01:09:13 you could be interested in this planet.

01:09:16 Deep in the atmosphere of Neptune, where the pressures are extreme,

01:09:19 scientists have hypothesized that carbon atoms would be so compressed that they would form diamonds.

01:09:26 These diamonds could then fall like rain.

01:09:28 What a unique touch for a beautiful storm!

01:09:31 The moons of Neptune inherited from their parents this strange weather.

01:09:36 For example, its largest moon, Triton, has a touch of cryovolcanism.

01:09:41 Instead of vomiting melting rocks like terrestrial volcanoes,

01:09:45 Triton's cryovolcanoes burst with a mixture of water, ammonia and nitrogen.

01:09:50 It looks like ice geysers projecting their matter into space.

01:09:54 It seems that in our only solar system, each planet has its own fascinating peculiarities.

01:10:00 Let's hope we'll discover other interesting things in the space that is near the future.

01:10:05 Aristotle once said that gold was only solidified water in the ground and mixed with sun rays.

01:10:12 Others were convinced that gold could be made using the Philosopher's Stone.

01:10:16 When the Incas saw gold for the first time,

01:10:19 they imagined that this falling metal was the tears of a deity.

01:10:24 But its true origin seems much more spectacular in itself.

01:10:29 Let's go back to a very distant past, to a time when there were no humans or animals.

01:10:35 A time when dinosaurs did not even exist yet.

01:10:38 A time when the simplest forms of life were just beginning to exist.

01:10:43 Our planet looked like a huge cauldron filled with chemical elements.

01:10:48 The elements, earthquakes and lightning, were constantly striking.

01:10:52 It was about 3.9 billion years ago.

01:10:56 During this period, huge asteroids crossed our solar system.

01:11:00 They hit Mercury, Venus, Earth and Mars.

01:11:04 It is possible that asteroids also fell on the Moon and left large craters.

01:11:09 A real apocalypse happened on our planet.

01:11:12 But fortunately, no one saw it happen because there was no life in it yet.

01:11:17 In parallel to this destruction, asteroids brought with them metals.

01:11:22 But were there any mines on Earth before that?

01:11:25 Of course.

01:11:26 The core of our planet is mainly made up of metals such as iron.

01:11:31 From there, it spreads in the Earth's crust, mixes with magma,

01:11:35 comes into contact with oxygen and combines with other elements.

01:11:39 But how did these elements end up in our core?

01:11:43 Simple atoms of hydrogen and helium fused and formed heavier elements inside giant stars.

01:11:50 Then supernovas occurred and formed large clouds of dust and gas.

01:11:56 These clouds reached our galaxy and began to rotate around the Sun.

01:12:01 Over time, this dust and its remnants of stars formed planets.

01:12:06 One of them was our Earth.

01:12:09 The metals that rest in the core of our planet are difficult to obtain.

01:12:14 And we would not have the technology we have today

01:12:17 without this meteor shower that has constellated the surface of the Earth with mines.

01:12:23 There are two theories.

01:12:25 One suggests that powerful supernova explosions far into our universe

01:12:28 formed most of the metals in our periodic table.

01:12:32 During the explosion, a nuclear fusion occurred, creating gold atoms.

01:12:38 Then the shock wave projected these incandescent pieces in different directions.

01:12:43 They flew for a long time, cooled in the ice and reached our solar system.

01:12:49 Another theory says that gold and other metals appeared as a result of the fusion of two neutron stars.

01:12:56 These are powerful stars whose size is several times smaller than that of the Sun,

01:13:01 but whose mass is several times greater than its own.

01:13:04 These are objects with a gravitational force and a colossal density.

01:13:08 Their collision would have generated an intense gamma radiation capable of synthesizing gold.

01:13:14 In 2017, astrophysicists observed for the first time the collision of two neutron stars.

01:13:21 They recorded traces of heavy metals, including gold, thanks to gravitational wave detectors.

01:13:28 This theory therefore seems more probable.

01:13:31 And if we went even further?

01:13:34 Where do the stars come from?

01:13:36 Dust and gas clouds are dispersed in the universe.

01:13:40 They mix, combine into one mass and grow like a huge snowball.

01:13:45 They press each other and generate a gravitational force.

01:13:49 When all matter collapses on itself, it begins to heat up.

01:13:52 And this energy boost then creates a star.

01:13:57 Some physicists suppose that stars, over their lifetime, can produce most of the elements of the periodic table.

01:14:04 If this theory is true, then our body is also made up of star particles.

01:14:09 We may be made up of a gigantic supernova that exploded billions of years ago, at the other end of the universe.

01:14:16 More than 50 years have passed since the appearance of this theory, but no one has proven or refuted it since.

01:14:24 Let's go back to our gold.

01:14:27 One of the largest gold deposits in the world is in South Africa.

01:14:31 Scientists believe that precious metal appeared there more than 2 billion years ago, after the fall of a gigantic meteorite.

01:14:40 Scientists are as convinced that gold lies at the bottom of the oceans of the entire world.

01:14:45 Between 10 and 20 million tons of this precious metal could be under the water.

01:14:49 But it's not big nuggets, but rather tiny particles dissolved in the liquid.

01:14:54 The extraction of this gold would therefore be far too expensive.

01:14:58 Let's now discover how people extract gold and turn it into jewelry.

01:15:03 First, you need to find gold deposits, large plots of land or rocks inside which the gold is hidden.

01:15:10 Miners then use pickaxes, shovels and machines to extract shiny splinters from the rock.

01:15:17 These pieces are then dissolved in a special acid that separates the gold from the other solids.

01:15:22 Then, other substances are extracted from the precious metal by fusion or gas injection.

01:15:28 When the gold is refined, its purity is checked.

01:15:32 99.9% is the reference value.

01:15:35 And that's the job. Your gold is ready to go.

01:15:38 It is possible to transform it into jewelry or electronic components.

01:15:43 The rarest metals on Earth also come from stars.

01:15:47 These are rhodium and iridium.

01:15:51 They are several times more expensive than gold, not because of their beauty, but because of their practical value.

01:15:58 For example, rhodium and iridium can make harmful gases harmless.

01:16:03 And 90% of the demand for this metal comes from the automotive market.

01:16:09 These metals are used in the manufacture of catalysts, which are necessary to reduce harmful exhaust gases.

01:16:15 When toxic substances produced during fuel combustion come in contact with these rare metals,

01:16:21 they also become safer, since a micro layer of rhodium and iridium is applied to the cylinder walls.

01:16:27 Gold, platinum, rhodium and iridium are the most expensive metals.

01:16:34 But what about the most durable metals?

01:16:37 It is a bit complicated to choose a winner, because the resistance of a metal depends on four criteria.

01:16:44 First of all, there is the resistance to traction.

01:16:47 It is the capacity of a metal to withstand the rupture.

01:16:50 For example, the modeling paste has a very low resistance to traction,

01:16:54 because you can easily stretch it in different directions.

01:16:57 Among metals, it may be tungsten, which is the most difficult to stretch.

01:17:01 Another criterion is the resistance to compression.

01:17:05 It is the capacity of a metal to withstand any pressure.

01:17:09 And in this field, it is chrome, which is one of the most resistant.

01:17:12 The third criterion of resistance of metals is the limit of elasticity.

01:17:17 To measure it, you have to make a rod or a beam from any metal,

01:17:22 then try to bend it and break it.

01:17:24 The metal with the greatest resistance will have a high limit of elasticity.

01:17:28 And titanium seems to indicate everything for that.

01:17:30 The fourth criterion is the resistance to shock.

01:17:34 This factor shows how resistant the metal is when it falls or when it is hit.

01:17:39 In this regard, iron records excellent results.

01:17:42 Each metal has its own strengths and weaknesses.

01:17:46 Chrome, for example, has a high resistance to compression,

01:17:49 but it resists traction poorly.

01:17:51 This is why the metallurgical industry makes alloys of metals to combine their strengths.

01:17:57 Well, we have learned to know the rarest and most expensive metals.

01:18:01 And what about other elements?

01:18:03 What is the rarest substance in the world?

01:18:06 Well, here is the state, the rarest element on our planet.

01:18:10 There are a total of about 25 grams of this substance in the whole world.

01:18:14 And its disintegration rate is equal to the speed of its formation.

01:18:18 Therefore, the amount of this substance in nature never changes.

01:18:22 This element was theorized at the end of the 19th century and discovered at the beginning of the 20th.

01:18:28 But even today, after so many years, we know little about it.

01:18:35 In 1869, the creator of the periodic table, Dmitri Mendeleev,

01:18:39 deduced that there was a certain substance corresponding to number 85 in the group of allogens.

01:18:44 This group of non-metallic elements includes substances such as fluorine, chlorine, bromine and iodine.

01:18:50 The state is therefore considered the heaviest of all known allogens and the most similar to metals.

01:18:57 It has a low melting point and poorly conducts heat and electricity.

01:19:02 It is brittle in solid state and dark in color.

01:19:05 Even today, scientists do not know all its properties.

01:19:09 It is almost impossible to find it in nature.

01:19:13 But chemists have learned to synthesize it artificially.

01:19:16 We do not know how to exploit this element either, because it is too radioactive.

01:19:21 But in some laboratories, researchers lead experiments

01:19:24 using the state to treat thyroid diseases.

01:19:30 "No one will hear you scream in space" or something like that.

01:19:34 We have all heard this sentence that is cold in the back.

01:19:37 And it's true, space is largely made up of a gigantic void.

01:19:41 There is a lot of space in space.

01:19:44 But that does not mean that there is no noise.

01:19:47 In fact, there is a lot of it.

01:19:49 And some of them could even make you shiver.

01:19:52 We are going to look at the scariest sounds in space.

01:19:55 First of all, how are cosmic noises recorded?

01:19:58 Sound is just the vibration of molecules.

01:20:01 When you scream, the molecules grow furiously from one another

01:20:04 until they reach the person's ear in front of you.

01:20:07 These vibrations are then transmitted to the brain

01:20:10 and we recognize them as something that we sometimes have to apologize for.

01:20:14 To hear something, we need molecules.

01:20:18 And that's where it gets complicated.

01:20:20 There is none in space.

01:20:22 The universe is almost entirely made up of voids.

01:20:26 Yes, of absolute void.

01:20:28 However, NASA's magicians still manage to record the sounds of space.

01:20:33 How do they do it?

01:20:35 Well, there are certain types of waves that have nothing to do with molecules.

01:20:39 We, ordinary people, cannot perceive them without certain devices.

01:20:43 Among these waves, there are, for example, radio waves.

01:20:46 We need a radio or a device of this type to recognize them.

01:20:50 And that's exactly what NASA satellites do.

01:20:53 They capture radio waves.

01:20:56 Thanks to them, we can recognize the sound of the cosmic bodies.

01:21:00 These satellites record a multitude of waves,

01:21:03 the fluctuation of plasmas, magnetic fields, and other things.

01:21:07 NASA scientists then transform all this into ordinary soundtracks.

01:21:12 And some of these things make a rather frightening sound,

01:21:15 if you can call it that.

01:21:17 Let's take, for example, our magnetic field.

01:21:19 It surrounds our planet like an invisible shield,

01:21:22 protecting us from all kinds of damage, like radiation or solar winds.

01:21:26 We can neither see nor feel it, but today we can hear it.

01:21:31 Researchers at the University of Denmark have collected magnetic waves

01:21:37 recorded by the SWARM satellite.

01:21:40 They then converted them into soundtracks,

01:21:42 and obtained a rather frightening result.

01:21:48 In fact, it sounds more like the noise of a frightening nocturnal creature.

01:21:52 And if you have the Earth's magnetic field map in mind,

01:21:56 you'll get the impression that a spider is crawling in the clouds.

01:21:59 And it's not the only strange sound we've captured on Earth.

01:22:03 Recently, we've captured another radio signal from space.

01:22:07 Scientists have discovered that it came from a very distant place,

01:22:11 billions of light years away from us.

01:22:15 These waves don't usually last more than a few milliseconds,

01:22:18 but this one was exceptional.

01:22:20 It lasted about three seconds,

01:22:22 which is thousands of times longer than usual.

01:22:25 At the same time, the signal was very precise,

01:22:28 to the point that scientists have even compared it to a heartbeat.

01:22:33 Scientists think this signal is caused by pulsars or neutron stars.

01:22:38 In the past, Nikola Tesla captured something similar.

01:22:42 Unfortunately, at the time, we didn't know about pulsars.

01:22:45 Tesla was therefore convinced that he had captured the message of extraterrestrial creatures.

01:22:50 But the truth turned out to be much less fascinating.

01:22:54 Let's now go from Earth to the Moon.

01:22:57 In 1969, the astronauts of the Apollo 10 mission,

01:23:01 the shuttle that made the last test flight to the Moon,

01:23:04 flew over its surface.

01:23:06 They then captured strange signals coming from the hidden side of our satellite.

01:23:11 We never see this side, because the Moon is in a gravitational lock state.

01:23:15 The sound was so strange that the astronauts didn't know if they should report it to NASA.

01:23:20 They feared not being taken seriously,

01:23:22 or even not being allowed to participate in the next space missions.

01:23:26 Here's what it looked like.

01:23:29 According to NASA, it's not at all an alien music.

01:23:36 It may simply be radio waves that have changed from one to the other because of their proximity.

01:23:42 But the astronauts who heard it for the first time were still a little scared.

01:23:46 What about other planets?

01:23:49 40 years ago, scientists explored the surface of Venus.

01:23:53 They sent dozens of probes to record sounds and images.

01:23:58 We now know what kind of noise Venus emits,

01:24:02 which could easily destroy us if we approached it.

01:24:06 We didn't expect anything else from the planet that is the most dangerous in the Solar System.

01:24:11 Unfortunately, Venus is even more toxic than the trolls who are on Twitter.

01:24:16 And these probes didn't last long.

01:24:19 They quickly went out of order after they arrived.

01:24:22 Then we have Jupiter.

01:24:25 This giant in space, which is 11 times larger than Earth, is absolutely terrifying.

01:24:30 One of the probes in the Solar System is the one that is the most dangerous.

01:24:34 One of NASA's probes, Juno, revolves around Jupiter every few weeks.

01:24:38 It moves at a phenomenal speed, at 209,214 km/h.

01:24:43 One day, Juno recorded one of the most powerful invisible signals it has ever encountered.

01:24:49 The violent solar winds had just entered into conflict with Jupiter's magnetic field.

01:24:53 It caused a huge cosmic boom.

01:24:57 The original sound lasted two hours, but was reduced to a few seconds.

01:25:03 In fact, it sounds a lot like the sound of a wave breaking on a rock.

01:25:07 But none of this is comparable to the horror of one of Jupiter's small moons, Ganymede.

01:25:14 In 2021, the space probe Galileo flew over it.

01:25:18 During its flight, it captured something quite strange.

01:25:22 These sounds are satellite radiation.

01:25:30 It sounds a bit like the noise of a jungle, or that of thousands of bats waiting to surprise you in the middle of the night.

01:25:36 Let's move on to Saturn.

01:25:39 This signal was captured by the Cassini-Huygens automatic interplanetary station, launched into space in 1997.

01:25:47 When passing in front of Saturn, Cassini recorded a rather frightening sound.

01:25:51 These screams straight out of hell are just simple radio waves.

01:25:58 And it's not very different from what the auroras of Boreal emit on Earth.

01:26:01 A little later, Cassini captured another signal.

01:26:04 The sound of lightning and storms on Saturn.

01:26:07 These sounds are quite interesting.

01:26:10 It sounds a bit like popping popcorn or a Geiger counter, doesn't it?

01:26:16 But it's simply because these lightnings are extremely fast.

01:26:19 We're now going to leave the solar system.

01:26:23 The famous Voyager 1 probe was launched in 1977 and continues to send us data 40 years after its take-off.

01:26:31 In 2012, it left the solar system to enter interstellar space.

01:26:36 That's when Voyager 1 recorded plasma waves.

01:26:41 The original recording lasted 7 months.

01:26:45 But scientists were kind to us and reduced it to 12 seconds.

01:26:52 It's not really that bad, but it's not very reassuring either.

01:26:55 And while it seems that nothing can outdo the horrors of Saturn,

01:26:59 we're now going to examine one of the most frightening objects in the universe.

01:27:03 A black hole.

01:27:05 This sound was recorded by the Chandra Space Telescope.

01:27:08 While studying a galaxy cluster in the Perseid constellation, we discovered something strange.

01:27:13 The oscillating movements in the center of the cluster.

01:27:19 They extend in all directions, like circles on water.

01:27:22 Scientists have declared that this phenomenon was due to a supermassive black hole.

01:27:27 But black holes don't always devour entire objects in space.

01:27:31 Sometimes they spit them out.

01:27:34 This causes gas vibrations that can be converted into sound waves.

01:27:39 What's interesting is that the oscillation of each of these waves lasts for about 10 million years.

01:27:47 This recording is therefore very fast.

01:27:49 Scientists have reduced the delay between oscillations by about 144 quadrillion times.

01:27:55 And this is what it sounds like.

01:27:57 It's probably the most sinister sound on our list.

01:28:01 It's neither very powerful nor very violent.

01:28:04 It has something rather dark and disturbing.

01:28:06 Here are the scariest spatial sounds captured by NASA.

01:28:10 As I said, most of them are just radio waves.

01:28:15 But it's always fun to be scared from time to time.

01:28:17 Astronomers have been asking themselves for decades.

01:28:21 Is space really as dark as we think it is?

01:28:25 Well, NASA's New Horizons space mission may have just given us the answer.

01:28:30 After exploring Pluto, the probe has continued its journey and is now billions of kilometers away from Earth.

01:28:38 This means it is far from all the light pollution from sources such as the sun and dust particles around our planet.

01:28:45 Scientists used the simple camera of the spacecraft to take images of what looked like an incredibly boring empty space,

01:28:54 devoid of bright stars or any other element likely to diffuse light into the camera.

01:28:59 They then processed these images to remove all known sources of visible light.

01:29:06 After eliminating the light from the stars and the light diffused by the Milky Way,

01:29:10 all that remained was the light coming from beyond our own galaxy.

01:29:14 And the most surprising part.

01:29:16 They discovered that there was still a lot of unexplained light.

01:29:19 In fact, there is about as much light that we do not know the source of as light coming from known galaxies.

01:29:26 This means that there is as much light outside the galaxies as there is inside.

01:29:31 So where does all this light come from?

01:29:34 It could come from sources that we have not yet discovered,

01:29:37 such as small, dimly lit galaxies, or be due to unknown phenomena in the universe.

01:29:43 It could also be associated with black matter, which remains a mystery to scientists.

01:29:47 Thanks to these innovative researches, we can say that space is not as dark as we think it is.

01:29:53 What happens if we take all the light from the stars and galaxies and add clouds of gas and dust to it?

01:30:00 What color do we get?

01:30:02 Beige.

01:30:03 This brings us to another question.

01:30:05 Would we still need the sun if our space was colored?

01:30:09 To sum up, yes.

01:30:11 The colors of space are the result of the interactions of light with different celestial objects,

01:30:16 such as stars, galaxies and gas clouds.

01:30:19 If these colors are fascinating to observe,

01:30:22 they do not provide the energy that life on Earth needs to survive.

01:30:25 At least, it's clear.

01:30:27 Do not expect to see the color of the sky and space.

01:30:32 When you think of the astronauts who go into space,

01:30:35 you probably imagine the great things they can do up there.

01:30:38 First of all, they fly like superheroes all the time.

01:30:41 The astronauts cling to rails and use the strength of their arms to move between the modules.

01:30:47 It takes a little time to get used to this way of moving,

01:30:51 but in a few months in space, they can become real acrobats.

01:30:55 They also read books, watch movies,

01:30:58 or take superb photos of the Earth through the cupola's windows,

01:31:02 a special observation area of the space station.

01:31:05 They also invent new games.

01:31:07 For example, they try to reach a target,

01:31:09 to run from one end to the other of the station as fast as possible.

01:31:13 And weightlifting sports, it must be great.

01:31:16 Can you imagine playing football up there?

01:31:18 It's the only way for me to get a good bike kick.

01:31:22 It's cool to see how they eat, or try to catch a bite from a floating spoon.

01:31:26 But in addition to all these fun things, they also need to sleep.

01:31:30 And it's not that easy in space.

01:31:33 The absence of weightlessness can be pleasant when you have fun and fly in your room.

01:31:37 But it's certainly not the case when you're tired and can't wait for your head to land on your pillow.

01:31:42 Because in space, this will not happen.

01:31:45 Astronauts must sleep in small sleeping bags fixed to the wall.

01:31:49 So they don't float and don't risk getting hit while they're asleep.

01:31:53 No sleeping bags up there, only floating sleepers.

01:31:56 In 1961, an astronaut went around our planet 17 times on board a space ship.

01:32:02 Proving that man could live, work and sleep in space.

01:32:06 But it's not because it's possible that it's easy.

01:32:09 Some astronauts have described their space capsule as a small "trash"

01:32:14 and the cabin itself as the size of a seat, before a Volkswagen cockpit.

01:32:19 Sleeping in space is very different from sleeping on Earth.

01:32:22 It's the least we can say.

01:32:24 There is no standing or lying down in space.

01:32:27 Astronauts can therefore choose the position that seems most comfortable to them.

01:32:32 On board the International Space Station,

01:32:34 the sleeping rooms are about the size of a telephone booth.

01:32:38 It's a small space that doesn't look as cool as the rest of the CE that's up there.

01:32:43 But astronauts are comfortable with it.

01:32:45 They have to sleep near an air intake to ensure good ventilation.

01:32:49 Breathing is more difficult in space because the carbon dioxide can form a bubble around the astronauts' heads.

01:32:56 This can be problematic because they don't have enough oxygen.

01:33:00 Astronauts cover the windows to block the sunlight

01:33:03 and can wear sleep masks, just like some people on Earth do to protect themselves from the light.

01:33:10 In space, the sun can be very bright, even with sunshades,

01:33:14 because there is no atmosphere to filter its rays.

01:33:17 Oh, what things we want to acquire down here!

01:33:21 In addition, the space station rotates around the Earth every 90 minutes,

01:33:25 which allows astronauts to see a new sunrise every hour and a half.

01:33:29 The station can also be noisy

01:33:31 because of the presence of all the fans and other equipment.

01:33:34 Astronauts sometimes wear earplugs to help them sleep.

01:33:38 We all become grumpy if we don't sleep enough, with or without gravity.

01:33:43 And that's not all.

01:33:44 Lack of sleep can affect our blood pressure,

01:33:47 our immune system, our balance and our health in general.

01:33:51 And it is much more difficult to feel sick in space than on Earth.

01:33:55 NASA predicts that S.A. astronauts sleep between 8 and 8.5 hours a day.

01:34:00 But those who work on board the ISS only sleep on average 6 hours,

01:34:05 because the space environment can disrupt their natural sleep rhythm.

01:34:09 This is why it is not uncommon to suffer from insomnia and lack of sleep when in space.

01:34:15 Temperatures are far from pleasant.

01:34:17 Astronauts sometimes have changes in their time schedule.

01:34:20 They must do long shifts or finish tasks that are assigned to them at night.

01:34:25 All this goes against a good sleep.

01:34:28 This is why NASA organizes sleep classes

01:34:31 and encourages special relaxation techniques to help crew members sleep better.

01:34:36 Dreams and nightmares are as frequent in space as on Earth.

01:34:40 It is impossible to prevent your mind from inventing different scenarios during sleep.

01:34:44 Some astronauts also snore in space.

01:34:48 And you know that feeling when you wake up all dizzy and lethargic?

01:34:52 It's like your body and your brain are still trying to catch up with lost time and wake up completely.

01:34:58 You can feel a little disoriented and have trouble thinking clearly or moving quickly.

01:35:04 This is what we call sleep inertia.

01:35:07 This feeling usually disappears after a while,

01:35:10 but it is probably much more difficult to get rid of it in space,

01:35:14 because many astronauts suffer from it.

01:35:16 And even if sleep conditions were perfect,

01:35:19 the simple fact of being in space would probably disrupt the natural sleep cycle of the body.

01:35:25 Two elements regulate this cycle.

01:35:28 The S process and circadian rhythms.

01:35:31 The S process determines whether we are asleep or awake throughout the day.

01:35:36 In space, the body sleeps less deeply,

01:35:39 which means that the S process undergoes modifications.

01:35:43 Circadian rhythms also help regulate our internal biological clock.

01:35:48 In space, where the markers such as exposure to light and darkness are completely disturbed,

01:35:54 it is impossible to set your alarm clock to 7 o'clock every morning.

01:35:58 At least up there, I would have a good excuse not to do it.

01:36:02 To help astronauts adapt,

01:36:04 NASA has added special lighting inside the space station,

01:36:08 which reproduces a normal day on Earth.

01:36:11 It tries to block the outside light at night

01:36:14 and provide enough light during the day to help astronauts stay awake

01:36:18 and sleep at the right time, as much as possible.

01:36:22 Astronauts must make sure not to expose themselves to the blue light of electronic devices,

01:36:26 which also disturb sleep.

01:36:28 This advice seems familiar to me.

01:36:30 We must find as many tricks as possible to sleep better,

01:36:33 because we do not want to go on a mission to Mars

01:36:36 and arrive in our new home all grumpy and in a bad mood.

01:36:39 In addition, the people who will participate in these special space missions

01:36:44 will not have as much space as the ISS astronauts.

01:36:47 Their cabins may not look like the comfortable bedrooms they have on Earth,

01:36:53 but they will always be dark, calm and especially private.

01:36:58 Besides, on the way to the Moon, we will have to say goodbye to privacy.

01:37:02 During these missions, the crew members will have less space to sleep.

01:37:07 It will be like camping with your friends, but with insufficient number of tents.

01:37:11 And imagine the time difference in space.

01:37:14 They usually hit the astronauts before they even reach the space station.

01:37:18 To remedy this, they begin to adapt their sleeping schedules a few days before their departure.

01:37:23 They modify their sleeping and waking hours

01:37:26 according to the time of day and the time zone of their starting point.

01:37:30 Once at the space station, or astronauts from different countries working together,

01:37:35 they all use a common hour called Greenwich Mean Time, GMT.

01:37:40 This allows everyone to synchronize their use of time,

01:37:43 because it is an intermediate hour that can be easily understood by people from different parts of the world.

01:37:49 To help the crew members sleep better, scientists have simulated space missions on Earth.

01:37:55 They have a special habitat called Hera at the Johnson Space Center,

01:38:00 whose size is almost identical to that of a lunar base or a space ship.

01:38:05 Crews live there for a while,

01:38:08 and researchers study their sleeping habits and their performance.

01:38:12 NASA is planning an interesting experiment called CHAPEA,

01:38:16 Crew Health and Performance Exploration Analog.

01:38:19 The first mission should begin soon with four crew members,

01:38:23 a commander, a doctor, a volume engineer and a scientist,

01:38:27 living in a habitat called Mars 1 Alpha at the Johnson Space Center.

01:38:32 They will live in this 3D-printed habitat and do exercise,

01:38:36 cook, clean, do other things,

01:38:39 and collect data as they would on the Red Planet.

01:38:42 We still have a decade or two before the first human missions to Mars,

01:38:47 but we'd better hurry up and get ready.

01:38:51 Hi friends, today we're going to unravel some myths about space.

01:38:56 Get on board our shuttle and clear it all up once and for all.

01:39:01 Imagine this.

01:39:04 You float in space drinking a cup of hot chocolate

01:39:08 when a strange thought comes to mind.

01:39:12 Can we scream in space?

01:39:14 And if so, would anyone hear this scream?

01:39:18 If you've seen Alien, you know the answer.

01:39:24 You can't hear sounds in space.

01:39:27 It's not that sounds don't exist,

01:39:29 it's just that you can't hear them.

01:39:32 There's no one better placed to unravel this myth than Chris Hadfield.

01:39:36 He's been to several spacewalks during his astronaut life.

01:39:40 Once in the darkness of space, you can't hear anything.

01:39:45 All you hear is silence.

01:39:48 Absolute silence.

01:39:50 But right next to it, there's a huge fireball, the sun.

01:39:56 We can't hear these explosions because there's nothing to carry the sounds.

01:40:00 But it probably wouldn't be very pleasant for astronauts

01:40:03 if they could hear all the sounds in space.

01:40:06 Imagine that you're sailing in space like a superhero of the future

01:40:12 when a shooting star passes by you.

01:40:15 But wait, is it really a star?

01:40:18 No, shooting stars are not stars at all.

01:40:22 They're little pebbles called meteoroids

01:40:25 that penetrate the Earth's atmosphere and create a beautiful luminous spectacle.

01:40:30 And since we're unraveling myths, here's another one.

01:40:35 You've probably heard that meteors only rarely crash on Earth.

01:40:40 Like when a violent apocalypse decimates all dinosaurs.

01:40:44 That's not true.

01:40:46 Scientists estimate that about 48 tons of meteorite material falls on Earth every day.

01:40:52 But almost all of this material evaporates in the atmosphere.

01:40:57 The luminous spectacle we see in the sky is what we call a shooting star.

01:41:02 The next time you make a wish, remember that it's actually a tiny space debris.

01:41:08 It's not that romantic after all.

01:41:11 Can we fly in the stratosphere in Montgolfière?

01:41:17 Apparently, it's possible.

01:41:19 The Earth's stratosphere starts relatively close to the ground.

01:41:23 It rises about 11 or 12 km above the surface of the Earth.

01:41:28 But it continues very high.

01:41:30 If you want to fly to the stratosphere with a Montgolfière,

01:41:34 you'll need a very good equipment.

01:41:37 You'll need a special suit and a respirator,

01:41:40 because the air is getting rarer as you rise.

01:41:44 Of course, if you go all the way, don't forget to photograph the curvature of the Earth.

01:41:49 So, get yourself a chest harness to hang a camera or a camera.

01:41:54 And if you broadcast all this live, it would be a first.

01:41:58 Imagine that 102 days ago you left Earth.

01:42:03 You've adapted well to life in space.

01:42:06 But something strange happens in your body.

01:42:09 You grow.

01:42:11 How is this possible?

01:42:13 Don't worry, it's perfectly normal.

01:42:16 In fact, you don't really grow.

01:42:18 It's just that your body no longer undergoes the effect of gravity.

01:42:22 Your body has a natural space between the vertebrae and the joints.

01:42:27 On Earth, this space is almost entirely compressed by the force of gravity.

01:42:32 But in space, the body, free of this force, starts to stretch.

01:42:37 So, yes, astronauts grow by 3% when they carry out long missions.

01:42:44 And here's a curiosity.

01:42:46 NASA doesn't forget this when it makes custom space suits.

01:42:50 So, astronauts will always have an extra space in their suits.

01:42:55 Once astronauts return to Earth, the anti-gravity effect will fade away.

01:42:59 They may spend a few days in a short-sleeved shirt before finding a normal size, but everything will be fine.

01:43:04 Have you ever imagined a fully-volume open-air aircraft door

01:43:10 and a group of passengers sucked into the atmosphere like simple feathers?

01:43:14 This is something we see quite often in disaster movies.

01:43:18 Now imagine that this happens in space.

01:43:22 We commonly believe that if an astronaut is sucked out of a sass, he will be burned alive, instantly.

01:43:28 But be careful, this is not only true.

01:43:31 In fact, the reality is much worse.

01:43:34 According to astronaut Chris Hadfield, this is what would happen.

01:43:38 The part of your body in the shade would be subjected to a temperature of -250°C.

01:43:44 And the part exposed to the sun would heat, it, at a temperature of 250°C.

01:43:50 Your lungs would suffocate and your blood would boil.

01:43:55 You would be burned, frozen, unable to breathe, and boiling.

01:44:01 Not recommended.

01:44:03 How many times have you heard that astronauts had to train every second of the day in order to faint?

01:44:11 It is a myth.

01:44:13 Do you remember what we said about gravity?

01:44:16 Because of the absence of gravity in space, our body does not have to work very hard.

01:44:22 Our torsos do not have to carry the weight of our heads.

01:44:25 And we do not have to make an effort to move our legs, because we do not really walk in space.

01:44:31 Imagine now that you lived like this for 6 months, or even a year.

01:44:36 Your muscles would quickly turn into ice.

01:44:40 This is why astronauts train.

01:44:42 They tie themselves up and run on a treadmill.

01:44:45 Or they do weight training on a special machine.

01:44:49 In this way, their muscles do not feel too much the absence of gravity.

01:44:54 However, they must hydrate.

01:44:57 If I were an astronaut, I would ask NASA if I could take my can of fresh water with me into space.

01:45:04 You may have heard that space smells like burnt steak or barbecue sauce.

01:45:09 Even if it seems absurd, this myth is more true than false.

01:45:14 Astronauts obviously cannot smell space when they are there, because they cannot take off their helmets.

01:45:21 They usually smell this once their vehicle has stalled and they have opened the sac.

01:45:27 Apparently, this smell is due to the presence of hydrocarbons floating in space.

01:45:32 Who would have thought?

01:45:33 Now let me ask you a question.

01:45:35 Do you really think that if astronauts could fly at the speed of light, they would not age for a second?

01:45:42 I knew you would say no.

01:45:44 Let's get this straight.

01:45:46 First of all, we have not yet found a way to travel at the speed of light.

01:45:50 This would require a huge amount of energy and we do not have the necessary technology.

01:45:56 Secondly, even if we managed to put a human inside a ship traveling at the speed of light,

01:46:02 this person would continue to age.

01:46:05 It would age differently from the people who remained on Earth.

01:46:08 It's a fact, but it would age anyway.

01:46:11 Do you really think immortality exists?

01:46:13 No.

01:46:15 If you have seen Avatar 1, you certainly remember that humans only managed to reach Pandora thanks to cryosleep.

01:46:22 They freeze their bodies, place them in cryogenic beds and travel for years without aging.

01:46:29 Yes, it seems incredible, but this technology does not yet exist.

01:46:33 Our body is mainly made up of water, right?

01:46:37 And when we freeze water, it expands.

01:46:39 That's why you should never leave a can of soda without monitoring in the freezer.

01:46:44 At present, if we freeze a person's body, the water it contains would spread,

01:46:49 and this would damage the tissues and organs.

01:46:52 So no, we can't cryosleep to travel in space, not yet at least.

01:46:57 Here is a crazy idea.

01:46:59 What would happen if an astronaut took a drone out into space?

01:47:04 Unless it's a drone designed by NASA, the device would freeze and probably burn without special protection.

01:47:11 But we can still dream, right?

01:47:14 Space travel has evolved a lot since the launch of Sputnik in 1957.

01:47:20 Since then, we have sent humans to the Moon, established the International Space Station,

01:47:26 and even sent robotic machines to explore other planets.

01:47:30 But we still have a lot to discover and accomplish.

01:47:34 What are our current projects?

01:47:36 What technologies are we developing and what is humanity waiting for in the next 100 years?

01:47:41 We'll see, okay?

01:47:43 First of all, artificial intelligence.

01:47:46 A little anecdote.

01:47:47 That's exactly how my history teacher described my intellect when I was in high school.

01:47:52 For a while, humanity has been engaged in the development of artificial intelligence.

01:47:57 And we have already made some great breakthroughs in this field.

01:48:01 With the help of artificial intelligence, we will be able to explore the cosmos like never before.

01:48:06 Think about it.

01:48:07 Artificial intelligence can automate tasks such as mission planning and data analysis.

01:48:12 Now, human astronauts can focus on more important things,

01:48:16 such as the research of non-human astronauts.

01:48:18 In addition, artificial intelligence can control space shuttles from a distance,

01:48:22 which reduces the risk of accidents.

01:48:25 And that's not all.

01:48:26 This technology also offers us incredible perspectives that humans may not have thought of on their own.

01:48:32 Artificial intelligence can also help us understand the data collected by space probes.

01:48:37 In short, using artificial intelligence in space exploration will allow us to learn more about the cosmos

01:48:43 and make the discipline more efficient and less expensive.

01:48:46 But that's not the only thing that will help us conquer space.

01:48:50 We also have reusable rockets.

01:48:53 Unique reusable rockets.

01:48:56 Today, these rockets are taking the lead in the space industry.

01:49:00 Not only do they save money,

01:49:03 but they also make travel accessible to a greater number of people and organizations.

01:49:08 SpaceX has already created a whole bunch of reusable rockets,

01:49:12 like the Falcon 9 and the Falcon Heavy.

01:49:15 And they have accomplished many missions to the International Space Station and even beyond.

01:49:20 Blue Origin has also made huge progress in the technology of reusable rockets with its New Shepard.

01:49:27 It even plans to bring tourists into space very soon.

01:49:31 Well, these great technologies will help us progress.

01:49:35 But what will we do next?

01:49:37 And why not a few colonies in the solar system?

01:49:40 Space colonization, what a great idea!

01:49:44 The possibility of establishing colonies on other planets, Mars for example,

01:49:49 is a dream that has captivated us for decades.

01:49:52 And now, it's within our reach.

01:49:55 But before we pack our bags, we have to solve a few problems.

01:49:59 To begin with, going to Mars is not an easy task.

01:50:03 It's a long journey that could take months, even years.

01:50:07 So we must first discover how to stay in good health during such a journey.

01:50:12 Once there, other challenges await us.

01:50:16 Radiation and temperature fluctuations are just a few examples among others.

01:50:21 Living and working in space is not easy.

01:50:24 We must ensure that everyone has what they need.

01:50:27 It's not like you can just go to the grocer to do your shopping.

01:50:31 We must therefore build systems that will provide food and water,

01:50:36 create means of transport, and maintain all this in good condition.

01:50:41 And let's not forget the most important thing.

01:50:43 Money. Building and maintaining a colony beyond Earth is far from easy.

01:50:48 We will need a lot of resources and a cooperation of all the instants to achieve this.

01:50:53 But living in space will bring us a lot.

01:50:56 Scientists will have a great field of study for research and exploration.

01:51:00 We will be able to learn more about the universe and our place in it.

01:51:05 We can therefore afford to dream.

01:51:08 The challenge is huge, but the gains are priceless for humanity.

01:51:12 This is why private companies and space agencies are working hard on the development of life on Mars.

01:51:18 They are already thinking about terraforming the Red Planet.

01:51:21 We will talk about that.

01:51:23 Terraforming is transforming a sterile and inhospitable planet into a habitable paradise.

01:51:30 It seems like a science fiction novel, doesn't it?

01:51:33 Well, believe it or not, with the help of advanced technologies and a lot of resources,

01:51:39 we could potentially transform the Martian deserts into beautiful welcoming territories.

01:51:44 But we will also have to overcome some obstacles.

01:51:47 Terraforming is not a fast process.

01:51:50 It takes a lot of time and resources to significantly change a planet.

01:51:56 There are also some ethical dilemmas.

01:51:59 If we start changing the Martian ecosystem,

01:52:02 we could potentially eliminate all forms of existing life.

01:52:06 Imagine if someone did that at home.

01:52:09 In fact, we are already doing it ourselves.

01:52:12 And finally, there is the cost.

01:52:14 Terraforming costs a lot of money, and we don't know yet who will pay the bill.

01:52:19 This will probably require the cooperation of several countries and organizations.

01:52:23 But even with these difficulties, it remains a beautiful dream.

01:52:27 And who knows, maybe one day we will be able to transform Mars into a superb holiday destination.

01:52:33 And this is just the beginning, because we will not stop in Mars.

01:52:37 Our next goal will be the asteroids and other celestial bodies.

01:52:42 Imagine that, you are floating in your space suit,

01:52:45 working on an asteroid to collect precious resources.

01:52:49 You fall on gold, or on a pretty platinum vein,

01:52:52 then return to Earth to sell it and make a fortune.

01:52:56 With this money, you finance even more expeditions,

01:52:59 and you become a space magnate.

01:53:02 More seriously, space mining could change the game for our development and our economy.

01:53:08 Imagine being able to extract water from asteroids and feed colonies throughout the solar system.

01:53:15 Or recover minerals for the high-tech industry.

01:53:19 The benefits would be immense.

01:53:22 Of course, there are also great challenges.

01:53:25 We will have to learn to extract the resources of these asteroids in a sustainable way.

01:53:29 And also ensure that this mining operation is done in an ethical way.

01:53:34 But, once these few points are settled, our lives will change forever.

01:53:39 So, let's get to work. And the day will come when we will have everything extracted.

01:53:43 What will we do then?

01:53:45 We could go and see what is beyond the solar system.

01:53:49 Travel to the stars in search of life.

01:53:53 We have already made incredible discoveries in this area.

01:53:57 For example, the Viking NASA landers and the Galileo space probe gave us some clues.

01:54:04 In addition, in 2022, we found traces of organic matter in ancient Martian lakes.

01:54:10 We are not yet sure, but Mars could well have been as fertile as the Earth one day.

01:54:15 But we all know that the real challenge is beyond our solar system.

01:54:20 We have already discovered thousands of exoplanets.

01:54:23 And some of them are in the habitable zone of their stars.

01:54:27 Which means that they could potentially shelter life.

01:54:31 Our next step is to send probes or even humans there.

01:54:35 Imagine being the first person to set foot on another planet.

01:54:39 Discover a microbial life or even an advanced civilization.

01:54:43 A whole new world.

01:54:45 And maybe one day, traveling to another stellar system will be like traveling from one country to another.

01:54:51 Except that instead of a minivan, you will be in a spaceship.

01:54:55 And instead of stopping for a rest, you will stop on a new planet.

01:55:01 Pretty cool, isn't it?

01:55:03 We have some ideas about how we could make interstellar travel a reality.

01:55:08 One possibility is the use of glass holes.

01:55:11 These hypothetical tunnels in space-time could allow us to travel long distances in a very short time.

01:55:18 A kind of shortcut, except that instead of cutting through a neighbor's garden, you would cut through the fabric of the universe.

01:55:24 Crazy, isn't it?

01:55:26 Another option is the propulsion by antimatter.

01:55:29 This implies the use of antimatter, which is a bit the opposite of our usual matter, as fuel for space ships.

01:55:37 When it comes in contact with normal matter, it releases a huge amount of energy.

01:55:42 Imagine the tank of your car filled with antimatter instead of gasoline.

01:55:47 This would be a really powerful travel.

01:55:50 Of course, we still have a lot of challenges to overcome before interstellar travel becomes a reality.

01:55:56 But we hope that one day we will all be able to pack our bags and board a spaceship that will take us to the stars.

01:56:03 Whatever it is, the future of space travel is promising.

01:56:07 Technology is advancing at a rapid pace, and we can't wait to see what the future holds for us.

01:56:16 Ah, space, the ultimate frontier.

01:56:19 A vast and mysterious expanse that has fascinated us for centuries.

01:56:23 But even though we have learned a lot about it,

01:56:27 know that some lies are still circulating today.

01:56:31 Let's take a look at some of the most obvious fictions and do the math.

01:56:36 First of all, we believe that space is a kind of neutral and intact territory.

01:56:41 But that's not exactly true.

01:56:43 We have been polluting space with our debris for decades.

01:56:47 There are old satellites, rocket parts.

01:56:50 In fact, more than 20,000 pieces of debris are currently orbiting the Earth,

01:56:56 and they cause all kinds of problems for future space missions.

01:57:00 So if you plan to visit space soon, be a little careful.

01:57:04 We never know what we might come across.

01:57:07 Did you know that the sun is not yellow?

01:57:12 It is green, in a way.

01:57:15 You see, scientists measure the temperature of a star by the spectrum of colors it emits.

01:57:20 The coldest stars give red, and the warmest give blue.

01:57:24 Our sun emits most of its energy on a wavelength close to green.

01:57:30 But as it also emits other wavelengths,

01:57:33 it ends up making a beautiful mixture that our eyes perceive as white.

01:57:38 On Earth, however, the sun seems yellow to us because our atmosphere is well dispersed by blue light.

01:57:44 If our star were really yellow, we would be polar bears on a glacial rock.

01:57:50 And the sun does not really burn.

01:57:54 It is a huge ball of gas made up mainly of hydrogen and helium,

01:57:58 and it works like a gigantic nuclear reactor,

01:58:01 constantly fusing hydrogen atoms to create helium inside its nucleus.

01:58:07 This process releases a huge amount of energy, and that is why the sun is so hot.

01:58:13 And speaking of burning things, explosions in space are not real.

01:58:18 Sorry, Star Wars fans.

01:58:21 A spaceship cannot explode violently because there is no air in space.

01:58:26 No air means no oxygen, and without oxygen, no fire.

01:58:32 You might think that there are too many stars in the night sky to count them,

01:58:37 but in reality, it is possible.

01:58:40 According to the catalog of bright stars of Yale,

01:58:43 we can see 9,110 stars with the naked eye from Earth.

01:58:47 So technically, you can count them,

01:58:50 but you still risk falling asleep before you finish.

01:58:54 You are worried about crossing an asteroid belt.

01:58:58 Don't be.

01:59:00 Although they contain billions of rocks,

01:59:02 which go from dust grains to a large quarter of the Moon,

01:59:05 they are very spaced.

01:59:07 The asteroid belt, located between Mars and Jupiter,

01:59:10 measures 225 million kilometers wide,

01:59:14 which is one and a half times the distance between the Earth and the Sun.

01:59:18 This divides the rocks over thousands of kilometers,

01:59:21 making it almost impossible to collide with a spaceship.

01:59:27 Would you freeze instantly in space without a suit?

01:59:30 No, you would not turn into ice right away.

01:59:33 It would take a little time,

01:59:35 because heat and cold do not move very quickly in the vacuum.

01:59:39 Unfortunately for you, there would be another problem.

01:59:43 You could not breathe.

01:59:45 After only 15 seconds, your brain would not receive enough oxygen,

01:59:49 and you would lose consciousness.

01:59:51 Then, after only 2 minutes,

01:59:53 it would be over for the rest of your organs.

01:59:56 So, in short, if you went out into space without a space suit,

02:00:00 your walk would not last long.

02:00:03 Did you know that space has no temperature at all?

02:00:08 It is because temperature is defined by the speed at which particles move,

02:00:12 and by the amount of energy they possess.

02:00:15 In the vacuum of space, there is no particle movement,

02:00:19 so no temperature.

02:00:21 Of course, some parts of space are very hot.

02:00:24 For example, the areas around the stars.

02:00:27 But the further you get away,

02:00:29 the more particles scatter,

02:00:31 and the colder it gets.

02:00:33 In number 9, we have the shape of our planet.

02:00:38 No, it is not flat,

02:00:40 but it is not a perfect sphere either.

02:00:43 Yes, it inflates at the equator because of its rotation.

02:00:46 It's a bit like the Earth was dancing.

02:00:49 And because of this inflation,

02:00:51 launching rockets from the equator is much easier than from the pole.

02:00:55 As for the sounds in space,

02:00:59 it's a bit complicated.

02:01:01 You might think that no one will hear you scream,

02:01:04 but it is not quite accurate.

02:01:06 Sounds need something to travel through,

02:01:10 like air or water.

02:01:12 In space, things are very scattered.

02:01:15 So, all these great space battles,

02:01:17 and these galactic explosions,

02:01:19 would be completely silent.

02:01:21 However, some areas contain enough particles

02:01:24 for the sound to spread.

02:01:26 For example, you can hear the black hole

02:01:28 in the center of Perseus' Lama.

02:01:30 Another myth is about zero gravity.

02:01:35 It does not exist.

02:01:37 There is always a little gravity

02:01:39 around the International Space Station,

02:01:41 about 90% of what we feel on our good old Earth.

02:01:46 And if astronauts float,

02:01:48 it's because they are essentially free-falling around the planet.

02:01:51 Let's be realistic.

02:01:53 The Hollywood version of space travel does not stand still.

02:01:56 Sure, orbits exist.

02:01:58 But with different altitudes,

02:02:00 we have different speeds.

02:02:02 So, going from one orbit to another

02:02:05 is not exactly a child's play.

02:02:08 You can't just launch in the right direction

02:02:11 hoping that it will go well.

02:02:14 You have to take orbital speeds into account.

02:02:17 I'm thinking of the 2013 film "Gravity",

02:02:20 in which Sandra Bullock

02:02:22 tries to survive in space.

02:02:25 The directors have somewhat transformed the effects,

02:02:28 but it's for the show.

02:02:31 In 1976,

02:02:33 the Viking 1 probe of NASA

02:02:35 took a picture of a strange rocky formation on Mars.

02:02:39 It looked a bit like a face.

02:02:41 Some have claimed that this was the proof

02:02:44 of extraterrestrial life on the Red Planet.

02:02:46 But NASA had another explanation.

02:02:49 According to the Space Agency,

02:02:51 this face was nothing more than a pile of rocks

02:02:54 stacked in such a way that the shadows it cast

02:02:57 created an illusion, a drawing.

02:03:00 It turns out that it is only an ordinary

02:03:03 and very photogenic hill.

02:03:06 The solar system does not move.

02:03:08 Lie.

02:03:09 It travels through space at a speed of 225 km per second,

02:03:13 which means that it travels through space

02:03:16 faster than a cheetah hunting its prey.

02:03:19 It takes 230 million years for the solar system

02:03:23 to make a complete orbit around the Milky Way.

02:03:27 A good thing that it does not receive a speed tax,

02:03:31 because it would be astronomical.

02:03:34 Without the sun,

02:03:36 the planets would be rather cold,

02:03:39 with temperatures that could go down to -270 ° C.

02:03:45 Brrr!

02:03:46 But thanks to the sun,

02:03:48 they benefit from much more pleasant temperatures.

02:03:50 Of course, not all planets are equal.

02:03:53 Mercury, for example, is the closest to the sun.

02:03:56 Venus, it is further away,

02:03:59 but it still manages to be even warmer than Mercury.

02:04:02 The distance from the sun

02:04:04 is not the only factor that affects the temperature of a planet.

02:04:08 Other factors, such as the size of the planet and its reflectivity,

02:04:11 also come into play.

02:04:13 So, to say that Mercury is the warmest planet in our solar system

02:04:17 is a false proposition.

02:04:19 No, it's not because it's the closest to the sun

02:04:22 that it's the warmest.

02:04:24 Even if we have been lied to about some things,

02:04:27 it does not make space less incredible.

02:04:30 It is still a vast, beautiful and absolutely fascinating part of our universe,

02:04:34 and we still have so many things to discover.

02:04:37 Who knows, maybe one day we will really discover little green men somewhere.

02:04:42 Or maybe we will find something even more wonderful.

02:04:46 In the meantime, we can continue to dream and explore.

02:04:50 So here are the 14 myths of the day.

02:04:52 Do you know others on the same subject?

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