Nous connaissons l'emplacement exact de la Terre dans l'univers grâce à un mélange d'astronomie et de technologie. D'abord, nous avons découvert que nous sommes la troisième planète en orbite autour du Soleil, qui fait partie de la galaxie de la Voie lactée—un immense spirale d'étoiles. Ensuite, les astronomes ont cartographié la Voie lactée elle-même, réalisant qu'elle se trouve dans un bras plus petit de la galaxie appelé le Bras d'Orion. Au-delà de cela, nous savons que la Voie lactée fait partie d'un groupe de galaxies appelé le Groupe Local, qui est dans une structure encore plus grande appelée le Superamas de la Vierge. En utilisant des télescopes et des satellites, les scientifiques suivent également la position de la Terre par rapport à d'autres étoiles, galaxies, et points de repère cosmiques comme les quasars. Mais pouvons-nous être vraiment sûrs d'avoir raison quant à la position de notre Terre ? 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
00:00A long time ago, we believed that the entire universe revolved around our little blue planet.
00:08This is what we call the geocentric model.
00:11We thought that the sun, the stars and all these sparkling celestial bodies danced around us.
00:17This theory was very popular in Greece and Ancient Rome.
00:21Famous geniuses like Aristotle and Ptolemy really loved this idea.
00:26But why did people believe that?
00:29Well, first of all, our ego is huge.
00:31Then, some elements seemed to support this idea.
00:34For example, if you stand on Earth and you look at the sun,
00:38it will seem to you that the sun revolves around you once a day.
00:42The moon and the planets seem to do the same thing.
00:45The obvious conclusion is, yes, all this is probably revolving around the Earth.
00:53Then there is the fact that the Earth seems relatively stable when you stand on it.
00:58You don't really feel like it's moving.
01:00And because of this stability under our feet, people thought the Earth was still.
01:06But at the same time, some Greek and Roman philosophers discovered something very interesting.
01:11They associated this geocentric model with the idea that the Earth was a sphere floating in space,
01:17and not a disc or something flat.
01:20And they started to see it more clearly.
01:22After a while, the astronomer and mathematician Harry Stark of Samos had a revolutionary idea.
01:28He thought that the Earth might not be the center of everything that existed.
01:33And he suggested that everything revolved around the sun.
01:35It is funny to note that at the time, this idea was considered nonsensical.
01:44This is why, for a long time, most people have remained faithful to their geocentric view.
01:49It took us several centuries to finally accept the heliocentric model
01:54where all the planets of our solar system revolve around the sun.
01:58This idea was highlighted by characters like Copernicus, Galileo and Kepler.
02:04This change was not easy for everyone.
02:06It was difficult to give up our centrality.
02:10But little by little, we gave up.
02:13And by giving up this idea, we discovered a whole new world.
02:17This journey led us to an amazing realization.
02:20Not only are we not the center of the universe,
02:23but we are only a small particle within it.
02:26We are a microscopic point in the immensity of the galaxy,
02:29which is called the Milky Way.
02:32The discovery of the Milky Way begins in our gardens.
02:35If you have already contemplated the stars by a clear night,
02:38you may have noticed a pale and luminous band stretching very far,
02:42like a sparkling celestial ribbon filled with stars.
02:46This is our galaxy.
02:47We named it the Milky Way,
02:49because it looks like milk spilled on a road.
02:59It was perfectly described in the 90s by Voyager 1.
03:03NASA's space probe took a picture called a pale blue dot.
03:08This tiny little pixel, almost impossible to see, is our planet.
03:13The picture was taken at a staggering distance of 5.86 billion kilometers from the sun.
03:19At the scale of the universe, this distance is nothing.
03:22But for us, it's unimaginable.
03:25Thus, when scientists discovered the Milky Way,
03:28they quickly equipped themselves with telescopes.
03:31Their goal was to map the unexplored territories of the night sky.
03:35And, of course, to find our place in this gigantic world.
03:41To do this, we first had to dig into the secrets of the structure of our galaxy.
03:45Well, we clearly see that it is in the form of a kind of elongated band.
03:50This means that our galaxy is not a big round ball like planets and stars.
03:55In reality, it looks more like a huge pancake or a flattened disc.
04:00And we can see that we are neither above nor below.
04:03We are well at the level of the disc.
04:06The next step is to travel the Milky Way to map it.
04:10However, there is a small problem.
04:12To do this, we would have to go through thousands of light years through this pancake-shaped object.
04:18To put things in perspective, let's go back to Voyager 1,
04:22the machine that took the picture of the pale blue dot.
04:25This space probe has been traveling in space for almost half a century.
04:29It left the solar system several years ago.
04:32Do you know how many light years it has traveled?
04:350.002.
04:37And how many light years does the Milky Way measure?
04:40100,000.
04:41You got it.
04:42But the absence of sophisticated technology did not stop us.
04:46In the 18th century, an audacious astronomer named William Herschel decided to explore our galaxy.
04:53With only a telescope, this Indiana Jones of astronomy began to map the stars in the sky.
05:00And he discovered Uranus, more than 2,000 nebulae,
05:04and created the first map of the Milky Way, which represented it as a disc.
05:08The map was not super-precise, but nevertheless very impressive.
05:15Unfortunately, he was not aware of what is called interstellar dust.
05:19It is like a space fog that can veil our view of the stars in the center of the Milky Way.
05:25This dust made the central region of the Milky Way appear less crowded than it really is.
05:30Let's move on to the 20th century.
05:32Henrietta Swan Leavitt, an American astronomer, was also very curious about the night sky.
05:38But she focused her attention on a particular type of star, the Cepheids.
05:43These stars had a unique peculiarity.
05:46They pulsated, that is to say that their burst varied according to a well-defined period.
05:51Leavitt's work at the observatory where she was employed was similar to that of a librarian.
05:57She cataloged these stars.
05:59And in doing so, she made an incredible discovery.
06:02She found a direct link between the brightness of these stars and the frequency of their pulsations.
06:07This discovery is now known as the Leavitt law.
06:11This means that by simply measuring the speed of the pulsations of these stars,
06:17astronomers can determine how far they are.
06:20These variable stars have then allowed to measure all kinds of distances.
06:30Before the 1920s, most scientists believed that our Milky Way was the only galaxy in the universe.
06:37But as telescopes improved, some astronomers began to realize that the Milky Way was not the only galaxy in the universe.
06:45We began to discover more and more galaxies.
06:48But if the Milky Way was only one galaxy among so many others, where were we exactly in all this?
06:54This is when a scientist named Arlo Chaplet came on stage.
06:58Armed with a powerful telescope, Chaplet turned his attention to globular clusters.
07:03These are groups of ancient stars that, densely gathered, form spherical clusters.
07:10By discovering them, he noticed something very interesting.
07:14The oldest stars around us were not scattered.
07:17They were grouped around the center of the Milky Way.
07:20And they pointed in the direction of certain constellations, such as Sagittarius and Scorpio.
07:26It turned out that our galaxy had started from the center.
07:30This was the heart of the Milky Way, and the oldest stars had settled there.
07:35This means that we are not even in the center of our own galaxy.
07:39It looks like our importance is decreasing more and more with each new discovery, doesn't it?
07:44Anyway, Chaplet discovered that we were located somewhere on the periphery of our galaxy.
07:50Chaplet's calculations were not perfectly accurate, but they were still quite precise.
07:56Fortunately, we now have very efficient and fascinating tools.
08:00Since then, we have been able to locate our location precisely.
08:04We are located near a partial arm of the Milky Way, called the Orion Arm.
08:08It is located about 26,000 light-years from the center of our galaxy.
08:12This is how we discovered where we are in the Milky Way.
08:20Do you think our story is over?
08:22No, absolutely not.
08:24Here is Gaia, the celestial cartographer of the Milky Way.
08:28Launched in 2013, Gaia embarked on a bold mission.
08:32She must map the Milky Way with an unprecedented level of detail.
08:37Not just a summary map, but a photograph of the most subtle nuances of our galaxy.
08:43Gaia assembles the positions and movements of about a billion stars.
08:47And that represents about 1% of all the stars of the Milky Way.
08:51But this tiny fraction is still a very important part of our galaxy.
08:56This tiny fraction is still a true masterpiece of cosmic cartography.
09:02What a great adventure!
09:04It led us from the belief that the Earth was the center of the universe
09:08to the realization that we are less than dust in the great order of things.
09:13But the most important thing is that this story shows how curious humanity is about the mysteries of the world.
09:19And there is always something new to explore.
09:23We never stop making new discoveries.
09:25So stay tuned and keep watching the night sky.