Prêt à plonger dans des anecdotes stupéfiantes sur l'espace ? Vous apprendrez la théorie selon laquelle notre Soleil pourrait avoir un jumeau lointain et invisible nommé Némésis, qui serait lié aux extinctions massives sur Terre. La vidéo aborde également des faits fascinants sur les univers parallèles et d'autres mystères cosmiques. C'est un moyen rapide et amusant d'élargir vos connaissances de l'univers. En seulement 20 minutes, vous serez étonné de voir combien il y a à découvrir sur notre cosmos ! Animation créée par Sympa.
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Musique par Epidemic Sound https://www.epidemicsound.com
Pour ne rien perdre de Sympa, abonnez-vous!: https://goo.gl/6E4Xna
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Nos réseaux sociaux :
Facebook: https://www.facebook.com/sympasympacom/
Instagram: https://www.instagram.com/sympa.officiel/
Stock de fichiers (photos, vidéos et autres):
https://www.depositphotos.com
https://www.shutterstock.com
https://www.eastnews.ru
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Si tu en veux encore plus, fais un tour ici:
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FunTranscript
00:00Let's look at the things in front of us. For a star, our sun is quite ordinary.
00:05And no, it has nothing exceptional. There are millions of similar yellow dwarfs in the universe.
00:11And yet we love them. After all, it's our only star, and it gives us life.
00:16However, it has not always been so.
00:19Once upon a time, the sun had a twin, and maybe even an evil twin.
00:24What happened to him? That's what we're going to find out.
00:28This is a giant molecular cloud. They are also sometimes called dark nebulae.
00:34There is a whole bunch of interstellar amas filled with gas, dust and tons of stars.
00:39These clouds have no precise limits and often take completely crazy shapes.
00:44Some are even visible to the naked eye.
00:47Look at the night sky. You will see as dark spots on our luminous milky way.
00:52And that's where our sun was born about 4.5 billion years ago.
00:57It comes from one of these molecular clouds.
01:00All these years ago, energy waves passed through there.
01:04They gathered all this matter and compressed these amas into dense cores.
01:09That's when a proto-star was born.
01:11This young proto-star was a ball of hydrogen and helium still warm.
01:16Then, millions of years later, the temperature and pressure inside the ball increased.
01:21And that's how our star was born. The sun.
01:24But all that was in this cloud did not contribute to its formation.
01:28A remnant began to revolve around the new star.
01:31And as you may have guessed, this matter gradually transformed into a planet.
01:36And our Earth was born.
01:39This is how our solar system was created.
01:42But it is possible that this is not all.
01:44And that when our star was born, another one was also born.
01:48The lost twin of the sun.
01:50Made from the same materials.
01:53But what tells us that it exists?
01:55Recently, scientists have created models to learn more about the birth of stars.
02:01And they have revealed that most of the stars are not born alone, but in amas.
02:06Or at least with a brother.
02:08After other research, our scientists have been able to confirm that the stars formed inside the molecular clouds
02:14were the most often accompanied.
02:16It happens that the two stars stay together.
02:19For example, the little one will revolve around the biggest one.
02:22They can even form double, triple and even more star systems.
02:26In other cases, their paths will diverge.
02:29Forever.
02:30This is probably what happened to our sun.
02:33But it could have had a brother or a sister too.
02:36Maybe even more than one.
02:38A whole fraternity.
02:40And even a great twin, with a mass and similar characteristics.
02:44But if that were the case, where would this second sun be?
02:48We have a hypothesis.
02:50And according to it, this twin may be more harmful than it seems.
02:54In the 80s, scientists began to notice that something was happening in the history of the Earth.
03:00Every 27 million years, large-scale extinctions seem to occur on our planet.
03:07Pretty strange, isn't it?
03:09Every 27 million years, a disaster has come to change our biosphere forever.
03:14Like something programmed.
03:17A kind of cycle.
03:19And then, the astrophysicist Richard Muller suggested that there may be something causing these events.
03:25A certain celestial body.
03:27According to him, it could be a dwarf star that we cannot see because of its low luminosity.
03:33It could be located about 1.5 light years from us.
03:37This star would revolve around the sun on an immense orbit.
03:41And it would take about 27 million years to make a full circle.
03:45And when it gets close to the sun, it's total chaos.
03:49When it gets close to us, this troublemaker changes the trajectory of the comets coming from the cloud of Oort or the belt of Kuiper.
03:56The result is that all these comets rush straight at us.
04:00And then they crash on Earth and cause major extinctions.
04:04As was the case for dinosaurs.
04:06This hypothetical star was named Nemesis.
04:09It is the name of the Greek deity of celestial punishment.
04:12But why is it taking revenge on us?
04:14No idea.
04:16Maybe it did not appreciate the fact that one day, the sun absorbed all the dust and gas from its molecular cloud.
04:22The sun became a fairly large star.
04:25But its twin remained dark and small.
04:28And in addition, it ended up in the middle of nowhere.
04:31We would all be a little bitter if it happened to us.
04:34Scientists have proposed different hypotheses about this mysterious Nemesis.
04:39Maybe it was a brown or red dwarf?
04:42The remains of a star that has completely exhausted its fuel?
04:46Or maybe it is not at all a star, but a wandering planet larger than Jupiter?
04:51Either way, its existence is not really a good thing for us.
04:55But our attempts to find it have unfortunately failed.
04:59At present, we have not found any trace of it yet.
05:03Recent studies have questioned the theory of regular extinctions.
05:07If you look closely at fossil archives,
05:10you will notice that these disasters occurred by chance, and not according to a specific calendar.
05:15Now, scientists doubt that Nemesis really exists.
05:20They also say that a star moving with such an orbit would be very unstable.
05:24It is therefore very unlikely that it could have survived for so long.
05:28But despite this lack of evidence, Nemesis has become quite famous online.
05:33Many journalists and bloggers still mention it in different contexts.
05:37They like to impute the responsibility of all our disasters,
05:41such as the fall of asteroids, tsunamis, etc.
05:46Once they have exploded,
05:48the stars are not supposed to come back to life.
05:51But some stars have somehow survived the great explosion of supernovas.
05:56These zombie stars are rather rare.
05:59Scientists have found a very large one called LP40365.
06:04It is a partially consumed white dwarf.
06:07A white dwarf is a star that burned all its hydrogen,
06:10which was previously its nuclear fuel.
06:13In this case, the final explosion was perhaps not powerful enough to destroy the star,
06:18which explains why some of the matter survived.
06:21Another of these zombie stars is an old white dwarf,
06:25a residue of an explosion that engulfed so much matter
06:28from another star that, surprisingly, it exploded again.
06:32If you go to the Moon one day and you see fresh footprints,
06:35it does not mean that there is someone else with you.
06:38Footprints or other similar marks can remain there for a million years,
06:43because the Moon has no atmosphere.
06:45So there is no wind that could slowly erase these footprints.
06:49In space, you would be strong enough to weld two pieces of metal together with your own hands.
06:54OK, it has nothing to do with strength.
06:57You would just have to press together and that's it.
07:00The oxygen of our atmosphere forms a thin layer on the surface of the metal that acts like a barrier.
07:06This is why this impossible turn of force on Earth is perfectly plausible in space.
07:12Besides, if you go there one day, do not take off your suit out of the spaceship.
07:17The air in your lungs would spread, as well as the oxygen in your whole body,
07:23and you would swell like a balloon.
07:25Good news, the skin is elastic enough to prevent you from exploding.
07:30Weak consolation.
07:32If you watch a moving movie in space and you start crying,
07:36your tears will not flow.
07:38They will accumulate around your eyeballs,
07:41your eyes will become too dry and you will have the impression that they are burning.
07:45All the liquid on the surface of your body will evaporate, including saliva on your tongue.
07:50Speaking of burning, you can't make a fire in space because it feeds on oxygen.
07:55And since there is no oxygen in space, if a fire breaks out in a sink,
07:59you just have to cut the ventilation system.
08:02It would be more complicated if smoke was produced
08:05and some materials melted in conditions of reduced gravity.
08:09Ordinary foam extinguishers, which we use on Earth, are useless here,
08:14because they disparately release the foam.
08:17Researchers are working on a fire extinguisher
08:20that would extinguish fires by using sound waves.
08:24The higher the intensity of the sound, the more it can extinguish large flames,
08:28but astronauts may become deaf if the frequency is too high.
08:33A black hole is not a hungry monster that wanders around
08:36and to the gravity of which nothing can escape.
08:39When something approaches the non-return point,
08:41which we also call the event horizon,
08:44it disappears without ever coming back.
08:47But according to quantum physics, nothing can really be reduced to nothing.
08:51It is therefore a paradox.
08:53It was Stephen Hawking who thought that black holes did not really have event horizons.
08:58Maybe they have apparent horizons that imprison things for a certain time
09:03and that the trapped energy ends up escaping in a different form.
09:08When an object enters a black hole, it changes shape and stretches like a spaghetti.
09:13This happens because the gravitational form tries to stretch an object in one direction
09:18while compressing it in another.
09:21Another paradox.
09:23Besides, a black hole as big as an atom has the mass of a huge mountain.
09:27There is one in the center of the Milky Way called Sagittarius A.
09:31It has a mass equivalent to a billion suns.
09:34But fortunately, it is very far from us.
09:38More than 23,000 bigger space debris than a baseball bat
09:41float above our planet, moving at more than 28,000 km per hour.
09:46And there are about 500,000 of them the size of a ball.
09:50Space debris is generally debris made up of natural particles
09:54called meteorites and artificial particles,
09:58like the ones we make on Earth.
10:02Meteorites orbit the Sun,
10:05while most of the human-made debris is orbiting the Earth.
10:10We have launched about 9,000 spacecraft around the world,
10:14satellites or rockets.
10:16Even the smallest pieces can damage a spacecraft with such high speeds.
10:21Galaxies, planets, comets, asteroids, stars,
10:26celestial bodies are things that we can actually see in space.
10:31But they represent less than 5% of the total universe.
10:35Black matter, one of the greatest mysteries of space,
10:38is the name we use to designate all the mass of the universe
10:42that is still invisible to us.
10:44It could make up 25% of the universe.
10:47Black energy makes up the rest of 70% of the universe.
10:53Scientists don't know much about it,
10:56but they think that black energy could be at the origin
10:59of the growing expansion of the universe,
11:01while black matter slows it down.
11:04Black matter does not interact with us or with itself.
11:08If that were the case, we would find galaxies of black matter,
11:12planets of black matter, or other objects of this type.
11:30The Sun
11:36The heat of the Sun is under our feet.
11:39Scientists have discovered that the core of the Earth
11:41is actually as hot as the surface of the Sun,
11:44about 6,000 degrees Celsius.
11:47One of the reasons it is so hot below
11:50is that the Earth still loses heat dating from its creation
11:54billions of years ago.
11:56In addition, when an object as big as Mars hit the young Earth,
12:00it not only created the Moon, according to a theory,
12:03but it also melted the surface of the planet.
12:06A large part of this additional heat
12:09is probably still stored inside the core.
12:12But there is no need to worry.
12:14It is more difficult for us to access the core of the planet
12:17than to probe the surface of Pluto.
12:20In fact, there is a good chance
12:22that we will never develop a technology
12:24that allows us to physically reach the core.
12:27There is no air on the Moon.
12:29But then how can there be rust?
12:32Scientists have discovered the presence of hematite on the Moon,
12:35which is a kind of rust.
12:37A NASA special research instrument
12:39examined the light reflected by the surface of the Moon.
12:42It turned out that the composition of the poles of our natural satellite
12:46was very different from the rest of the Moon.
12:49The surface is sprinkled with rocks rich in iron,
12:52but without oxygen or liquids,
12:54rust cannot appear.
12:56Solar winds add to the mystery.
12:59They bombard the Moon with hydrogen.
13:01However, hydrogen makes the formation of hematite much more difficult.
13:05Even if the Moon has no atmosphere,
13:07it still has traces of oxygen.
13:09Its source is the high atmosphere of our planet.
13:12The Earth also protects the Moon from almost 100% of solar winds,
13:16but not all the time.
13:18And even if our natural satellite is completely dry,
13:21there could be water ice in the shaded craters of its hidden face.
13:27A day on Uranus lasts 17 hours,
13:3014 minutes and 24 seconds.
13:32But the planet has an inclination of about 98 degrees,
13:36and this means that a season on the gas giant lasts 21 terrestrial years.
13:42Mars has two moons, Phobos and Deimos.
13:45In the 30 to 50 million years to come,
13:48the gravitational forces of Mars will tear Phobos,
13:51and this will probably lead to the formation of a ring around the planet.
13:57The Earth is the densest planet in the solar system.
14:00In the center of the Earth, the core occupies 15% of the planet's volume.
14:04It is made up of two parts,
14:06the external core and the internal core.
14:09The internal core is a solid ball made up of iron and nickel.
14:13Its radius is 1220 km,
14:17which represents 20% of the radius of the entire Earth
14:20and 80% of the radius of the Moon.
14:23The external core, 2,400 km thick, is liquid.
14:27It is also made up of iron and nickel,
14:30but it is not strong enough to be solid.
14:35Mars houses the largest volcano in the solar system.
14:38Although everything seems calm on Mars nowadays,
14:41in the past, a kind of force caused the formation and eruption of huge volcanoes.
14:46One of these volcanoes is Olympus Mons.
14:49It is 26 km high,
14:51which is three times the height of Everest,
14:53and 600 km wide,
14:55which is the size of Arizona.
14:57The volcano has reached such a size
14:59because of the low gravity on Mars
15:01and the lack of movement of the tectonic plates.
15:05Gravity is not the same everywhere.
15:08The rocks, metals and other minerals and substances
15:11that make up the planet are tighter in the ground
15:14in some places than in others.
15:16This has surprising consequences.
15:18Gravity varies slightly depending on where you are.
15:21You weigh 0.5% less at the equator than at the poles.
15:25In most cases, this represents a difference of less than a kilo.
15:29The altitude at which you are also has an effect.
15:32So if you were at the top of Mount Everest,
15:34you would also weigh slightly less.
15:37The most resilient living being on Earth
15:39is so small that you can't see it.
15:42Tardigrades, also known as water bears,
15:45are cute little creatures with eight legs and crushed heads
15:48that are less than one hundredth of a centimeter.
15:52Despite their microscopic size,
15:54they can survive almost everywhere.
15:56They prefer damp pieces of moss or the bottom of lakes,
15:59but they won't complain if you put them in a really uncomfortable place.
16:03They can withstand extreme cold and incredible heat
16:06and survive under enormous pressure and high radiation.
16:10Some of these bears have even managed to survive
16:12without protection in space for ten days.
16:15They manage all this by rolling in balls and hibernating,
16:19which reduces their need for oxygen and food.
16:23The gravity of the Moon is about 17% of that of the Earth.
16:26If you weighed 91 kilos on our planet,
16:29your lunar weight would be only 15 kilos.
16:32You could also carry objects six times heavier
16:34than what you can carry on Earth.
16:36It would also be easier to walk on the surface of the Moon.
16:40But it would also be more dangerous.
16:42Your feet, inside a heavy space suit,
16:45would sink into the lunar soil up to 15 centimeters deep.
16:49But let's imagine that you decide to avoid the tedious process of walking
16:52by jumping into the air.
16:54You would probably lose control of your jumps in a blink of an eye.
16:58In addition, the surface of the Moon is full of deep craters.
17:02Avoiding them all would be a feat.
17:05You can see solar eclipses,
17:07because even though the Moon is 400 times smaller than the Sun,
17:10it is also 400 times closer to the Earth.
17:13It is therefore perfectly capable of obscuring our star.
17:16But in 50 million years,
17:18the Moon will no longer be able to completely block the Sun
17:21because of its changing orbit.
17:23A complete space suit from NASA
17:26costs a staggering $12 million,
17:2970% of which is dedicated to the command module and the water bag.
17:33Venus was most likely covered by an ocean
17:36with a depth of 10 to 300 meters.
17:39In addition, a certain amount of water was trapped in the soil of the planet.
17:43It had stable temperatures of 20 to 50 degrees Celsius,
17:48which were therefore quite tolerable
17:50and not so different from the current temperatures on Earth.
17:54In short, for 3 billion years,
17:56until something unthinkable happened 700 million years ago,
18:01Venus could have been habitable.
18:03But today, it is no longer.
18:06The Moon is the second brightest object in our sky.
18:09However, among the other astronomical bodies,
18:12it is one of the darkest and least reflective.
18:15But our natural satellite seems bright because it is very close to us.
18:19In the same way, our planet seems much brighter
18:22when you look at it from space.
18:24It is because clouds, ice and snow reflect much more light
18:28than most rocks.
18:30Triton, the moon of Neptune,
18:32has its entire surface covered with several layers of ice.
18:35If this satellite replaced our current moon,
18:37the night sky would be seven times brighter.
18:42Neutron stars are among the smallest and most massive objects in space.
18:46They usually have a diameter of about 18 km
18:49but are several times heavier than the Sun.
18:51And they rotate themselves about 600 times per second,
18:54much faster than a professional skater.
18:58Saturn is the planet with the least density in the solar system.
19:01It has a density equivalent to one eighth of that of the Earth.
19:05And yet, because of its immense volume,
19:07the planet is 95 times more massive than the Earth.
19:11The transitory lunar phenomenon
19:13is one of the most enigmatic things that happens on the Moon.
19:16It is an ephemeral change of light,
19:18color or other, on the surface of the satellite.
19:21Most often, it is random light flashes.
19:24Astronomers have been observing this phenomenon since the 1950s.
19:28They noticed that flashes occurred unpredictably.
19:31Sometimes they can occur several times a week.
19:34Then they disappear for several months.
19:37Some of them do not last more than a few minutes,
19:40but some have lasted several hours.
19:43In 1969, one day before Apollo 11 landed on the Moon,
19:47one of the mission members noticed that part of the lunar surface
19:51was brighter than the surrounding landscape.
19:54It would have been said that this area had a kind of fluorescence.
19:57Unfortunately, we still do not know if this phenomenon
20:00was linked to the mysterious lunar flash.
20:02Waste is not just a problem in the oceans,
20:05cities and forests of the Earth.
20:07There is what is called spatial waste,
20:10that is, any object made by man
20:12that has been left in space and is no longer useful.
20:15There is also natural debris
20:17from meteorites and other cosmic objects.
20:20There are currently more than 500,000 spatial debris in orbit around the Earth,
20:24at speeds high enough to cause significant damage
20:27if they collide with a spaceship or a satellite.
20:31NASA does its best to track each object
20:33to ensure that missions outside the Earth
20:36can reach their destination safely.
20:39Our sun is incredibly massive.
20:41As proof, 99.86% of the entire mass of the solar system
20:46consists of the mass of the sun,
20:48in particular hydrogen and helium, of which it is composed.
20:51The remaining 0.14%
20:53is mainly the mass of the eight planets of the solar system.
20:57The atmosphere of the sun is warmer than its surface.
21:00The temperature of the surface reaches 5,500 degrees Celsius,
21:04but the high atmosphere reaches millions of degrees.
21:07If we could dig a tunnel directly in the center of the planet
21:10and go out on the opposite side,
21:12and you were adventurous enough to jump in,
21:15it would take you 42 minutes to cross it.
21:18You would accelerate as you fell
21:21to reach the maximum speed
21:23when you reached the core of the Earth.
21:25After half the journey,
21:27you would then fall up more and more slowly.
21:30When you reached the opposite surface,
21:32your speed would be back to zero.
21:34Unless you manage to get out of the hole,
21:36you would immediately start falling again
21:38to go back down, or go up,
21:40to the other side of the planet.
21:42This journey would last an eternity,
21:45because of the bizarre effects of gravity.
21:51There could be more metals,
21:53for example titanium or iron,
21:55in the lunar craters than astronomers thought.
21:58The biggest problem with this discovery?
22:00It contradicts the main theory
22:02about how the Moon was formed.
22:04This theory states that the natural satellite of the Earth
22:07detached itself from our planet
22:09after a collision with a massive space object.
22:11But then, why does the Earth's crust,
22:13poor in metals,
22:15contain much less iron oxide than the Moon's?
22:18This could mean that the Moon was formed
22:20from materials much deeper
22:22inside our planet.
22:24Or these metals could have appeared
22:26when the lunar surface, in fusion,
22:28cooled slowly.
22:30Or maybe, as it has been said for centuries,
22:32it is made of cheese.