Pratique du Shadowing: Black Holes Explained – From Birth to Death - Apprendre l'anglais à l'oral avec la vidéo
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74 phrases
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Black holes are one of the strangest things in existence.
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They don't seem to make any sense at all.
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Where do they come from?
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And what happens if you fall into one?
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Bye.
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Stars are incredibly massive collections of mostly hydrogen atoms that collapse from enormous gas clouds under their own gravity.
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In their core, nuclear fusion crushes hydrogen atoms into helium, releasing a tremendous amount of energy.
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This energy, in the form of radiation, pushes against gravity, maintaining a delicate balance between the two forces.
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As long as there is fusion in the core, a star remains stable enough.
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But for stars with way more mass than our own Sun, the heat and pressure at the core allow them to fuse heavier elements until they reach iron.
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Unlike all the elements that went before, the fusion process that creates iron doesn't generate any energy.
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Iron builds up at the center of the star until it reaches a critical amount, and the balance between radiation and gravity is suddenly broken.
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a fraction of a second, the star implodes, moving at about a quarter of the speed of light, feeding even more mass into the core.
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It's at this very moment
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that all the heavier elements in the universe are created as the star dies in a supernova explosion.
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This produces either a neutron star, or if the star is massive enough, the entire mass of the core collapses into a black hole.
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If you looked at a black hole, what you'd really be seeing is the event horizon.
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Anything that crosses the event horizon needs to be traveling faster than the speed of light to escape.
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In other words, it's impossible.
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So we just see a black sphere, reflecting nothing.
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But if the event horizon is the black part, what is the whole part of the black hole?
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The singularity.
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We're not sure what it is exactly.
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A singularity may be infinitely dense, meaning all its mass is concentrated into a single point in space, with no surface or volume.
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Or something completely different.
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Right now, we just don't know.
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It's like a dividing by zero error.
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things up like a vacuum cleaner.
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If we were to swap the Sun for an equally massive black hole, nothing much would change for Earth, except that we would freeze to death, of course.
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What would happen to you if you fell into a black hole?
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The experience of time is different around black holes.
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From the outside, you seem to slow down as you approach the event horizon, so time passes slower for you.
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At some point, you would appear to freeze in time, slowly turn red, and disappear.
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While from your perspective, you can watch the rest of the kind of like seeing into the future.
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Right now, we don't know what happens next, but we think it could be one of two things.
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One, the end.
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You die a quick death.
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A black hole curves space so much that once you cross the event horizon, there is only one possible direction.
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You can take this literally inside the event horizon.
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You can only go in one direction.
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It's like being in a really tight alley that closes behind you after each step.
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The mass of a black hole is so concentrated, at some point even tiny distances of a few centimeters,
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would mean that gravity acts with millions of times more force on different parts of your body.
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and more until you're a hot stream of plasma one atom wide.
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Two, you die a very quick death.
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Very soon after you cross the event horizon, you would hit a firewall and be terminated in an instant.
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Neither of these options are particularly pleasant.
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How soon you would die depends on the mass of the black hole.
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A smaller black hole would kill you before you even entered its event horizon, while you probably could travel inside a supermassive black hole for quite a while.
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As a rule of thumb, longer you live.
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Black holes come in different sizes.
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There are stellar mass black holes, with a few times the mass of the Sun and the diameter of an asteroid.
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And then there are these supermassive black holes, which are found at the heart of every galaxy and have been feeding for billions of years.
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Currently, the largest supermassive black hole known is S50014 +81,
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40 billion times the mass of which is 47 times the distance from the Sun to Pluto.
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As powerful as black holes are, they will eventually evaporate through a process called Hawking radiation.
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To understand how this works, we have to look at empty space.
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Empty space is not really empty, but filled with virtual particles popping into existence and annihilating each other again.
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When this happens right on the edge of a black hole, one of the virtual particles will be drawn into the black hole, and the other will escape and become a real particle.
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So the black hole is losing energy.
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This happens incredibly slowly at first, and gets faster as the black hole becomes smaller.
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When it has the mass of a mountain, it radiates with about the heat of our sun, and in the last second of its life, the black hole radiates away with the energy of billions of nuclear bombs in a huge explosion.
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But this process is incredibly slow.
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The biggest black holes we know might take up to a googol years to evaporate.
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This is so long that when the last black hole radiates away, nobody will be around to witness it.
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The universe will have become uninhabitable long before then.
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This is not the end of our story.
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There are loads more interesting ideas about black holes.
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We'll explore them in part two.
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A big thanks to Fraser Cain for help with this video.
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By the way, we've made some Kurzgesagt wallpaper in 4K for different screen sizes.
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You can get them on our Patreon page, which also helps us to make more videos.
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Like this December, the first month ever with 3 videos.
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Vocabulaire et conseils d’expression pour cette leçon
Cette vidéo contient 74 phrases et 1015 mots à répéter en shadowing. La partie parlée dure 5:54. Le locuteur parle à un rythme naturel d’environ 172 mots par minute, proche d’une conversation courante. 83 % des mots font partie des 3 000 mots les plus courants en anglais ; le reste mérite d’être vu avant de commencer.
Vocabulaire clé de cette vidéo
15 mots moins courants de la vidéo, avec leur prononciation et leur sens :
- horizon /həˈɹaɪ.zən/ (nom) — horizon, ligne d'horizon. The visible horizontal line (in all directions) where the sky appears to meet the earth in the distance.
- gravity /ˈɡɹævɪti/ (nom) — gravité. Of an activity such as a ceremony, a person's conduct, etc.: the quality of being deeply serious and solemn, especially in a dignified manner; seriousness…
- element /ˈɛləmənt/ (nom) — élément. One of the simplest or essential parts or principles of which anything consists, or upon which the constitution or fundamental powers of anything are based.
- incredibly /ɪŋˈkɹɛdɪbli/ (adverbe) — incroyablement. In an incredible manner; not to be believed.
- radiation /ˌɹeɪ.diˈeɪ.ʃən/ (nom) — radiation. The shooting forth of anything from a point or surface, like diverging rays of light.
- fusion /ˈfjuː.ʒən/ (nom) — fusion. The act of merging separate things, or the result thereof.
- particle /ˈpɑɹtək(ə)l/ (nom) — particule. A very small piece of matter, a fragment; especially, the smallest possible part of something.
- atom /ˈætəm/ (nom) — atome. The smallest possible amount of matter which still retains its identity as a chemical element, now known to consist of a nucleus surrounded by electrons.
- virtual /ˈvɜɹt͡ʃuəl/ (adjectif) — virtuel. In effect or essence, rather than in fact or reality; also, imitated, simulated.
- explosion /ɛkˈsploʊ.ʒən/ (nom) — explosion. A violent release of energy (sometimes mechanical, nuclear, or chemical); an act or instance of exploding.
- collapse /kəˈlæps/ (verbe) — s'effondrer. To break apart and fall down suddenly; to cave in.
- freeze /ˈfɹiːz/ (verbe) — geler, glacer. Especially of a liquid, to become solid due to low temperature.
- concentrate /ˈkɑn.sən.tɹeɪt/ (verbe) — concentrer. To bring to, or direct toward, a common center; to unite more closely; to gather into one body, mass, or force.
- hydrogen /ˈhaɪdɹəd͡ʒ(ə)n/ (nom) — hydrogène. The lightest chemical element (symbol H), with an atomic number of 1 and atomic weight of 1.008.
- stable /ˈsteɪ.bəl/ (nom) — étable, écurie. A building, wing or dependency set apart and adapted for lodging and feeding (and training) ungulates, especially horses.
Les verbes à particule que vous entendrez
- look at (verbe) — regarder. To observe or watch.
- slow down (verbe) — ralentir, décélérer. To decelerate.
Prononciation à surveiller
Le locuteur utilise 9 contractions et formes réduites, comme don't, doesn't, we'll. Prononcez-les sous leur forme courte, telles que vous les entendez.
- Les sons « sh » et « zh »: radiation /ˌɹeɪ.diˈeɪ.ʃən/, fusion /ˈfjuː.ʒən/, explosion /ɛkˈsploʊ.ʒən/, collections /kəˈlɛkʃənz/, crush /kɹʌʃ/
- Mots longs — placez bien l’accent: incredibly /ɪŋˈkɹɛdɪbli/, radiation /ˌɹeɪ.diˈeɪ.ʃən/, diameter /daɪˈæmɪdɚ/, infinitely /ˈɪnfɪnɪtli/, evaporate /ɪˈvæp.ə.ɹeɪt/
Comment s’entraîner avec cette vidéo
- Écoutez la vidéo en entier une fois sans parler et notez les mots que vous ne connaissez pas.
- Commencez à la vitesse 0,75×, répétez phrase par phrase, puis revenez à la vitesse normale quand cela devient facile.
- Enregistrez-vous et comparez avec l’original, en faisant attention à des mots comme horizon, gravity, element.
Qu'est-ce que la technique du Shadowing ?
Le Shadowing est une technique d'apprentissage des langues fondée sur la science, développée à l'origine pour la formation des interprètes professionnels. Le principe est simple mais puissant : vous écoutez de l'anglais natif et le répétez immédiatement à voix haute — comme une ombre suivant le locuteur avec un décalage de 1 à 2 secondes. Les recherches montrent une amélioration significative de la précision de la prononciation, de l'intonation, du rythme, des liaisons, de la compréhension orale et de la fluidité.