What is the universe made of? - Dennis Wildfogel
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0:07 - 0:09All the material objects around you
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0:09 - 0:10are composed of submicroscopic units
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0:10 - 0:12we call molecules.
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0:12 - 0:13And molecules in turn are composed
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0:13 - 0:15of individual atoms.
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0:15 - 0:17Molecules frequently break apart
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0:17 - 0:19and then form new molecules.
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0:19 - 0:20On the other hand,
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0:20 - 0:22virtually all the atoms you come in to contact with
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0:22 - 0:24through the course of your life,
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0:24 - 0:25the ones in the ground beneath you,
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0:25 - 0:27the air you breath, the food you eat,
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0:27 - 0:30those that make up every living thing, including you,
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0:30 - 0:32have existed for billions of years
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0:32 - 0:35and were created in places very unlike our planet.
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0:35 - 0:38How those atoms came about is what I want to share with you.
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0:38 - 0:40It all started 14 billion years ago
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0:40 - 0:42with an event we call The Big Bang,
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0:42 - 0:45which resulted in a universe consisting of gas alone.
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0:45 - 0:47There were no stars and no planets.
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0:47 - 0:48The gas was made up only of atoms
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0:48 - 0:50belonging to the simplest elements.
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0:50 - 0:52It was about 75 percent hydrogen
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0:52 - 0:54and almost all the rest was helium.
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0:54 - 0:57No elements like carbon, oxygen or nitrogen existed.
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0:57 - 0:59No iron, silver or gold.
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0:59 - 1:03In some places, the density of this gas was slightly higher than in others.
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1:03 - 1:06Due to gravity, those places attracted even more gas,
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1:06 - 1:08which further strengthened the pull of gravity,
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1:08 - 1:11which then drew more gas in, and so on.
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1:11 - 1:14Eventually, large dense gas balls formed,
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1:14 - 1:15shrinking under their own gravity
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1:15 - 1:18and consequently heating up on the inside.
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1:18 - 1:20At some point, the core of such a ball
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1:20 - 1:22gets hot enough that nuclear fusion occurs.
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1:22 - 1:25Hydrogen atoms smash together to form helium,
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1:25 - 1:27accompanied by a great release of energy,
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1:27 - 1:31strong enough to counteract the shrinking force of the gravity.
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1:31 - 1:33When the energy pushing out from the fusion reactions
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1:33 - 1:35matches the gravity pulling all the gas inwards,
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1:35 - 1:37an equilibrium occurs.
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1:37 - 1:39From this a star is born.
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1:39 - 1:40Over its lifetime,
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1:40 - 1:42the fusion reactions in the core of a massive star
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1:42 - 1:44will produce not only helium,
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1:44 - 1:46but also carbon, oxygen, nitrogen
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1:46 - 1:50and all the other elements in the periodic table up to iron.
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1:50 - 1:52But eventually, the core's fuel runs out,
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1:52 - 1:54leaving it to collapse completely.
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1:54 - 1:56That causes an unbelievably powerful explosion
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1:56 - 1:58we call a supernova.
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1:58 - 2:00Now there are two things to note
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2:00 - 2:02about how supernovas create elements.
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2:02 - 2:04First, this explosion releases so much energy
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2:04 - 2:06that fusion goes wild
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2:06 - 2:09forming elements with atoms even heavier than iron
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2:09 - 2:11like silver, gold and uranium.
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2:11 - 2:13Second, all the elements that had been accumulating
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2:13 - 2:14in the core of the star,
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2:14 - 2:17like carbon, oxygen, nitrogen, iron,
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2:17 - 2:20as well as all of those formed in the supernova explosion,
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2:20 - 2:22are ejected in to interstellar space
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2:22 - 2:24where they mix with the gas that's already there.
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2:24 - 2:26History then repeats itself.
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2:26 - 2:29Gas clouds, now containing many elements
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2:29 - 2:31besides the original hydrogen and helium,
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2:31 - 2:33have higher density areas
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2:33 - 2:35that attract more matter, and so on.
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2:35 - 2:38As before, new stars result.
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2:38 - 2:40Our sun was born this way about 5 billion years ago.
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2:40 - 2:42That means that the gas it arose from
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2:42 - 2:44had itself been enriched with many elements
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2:44 - 2:48from supernova explosions since the universe began.
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2:48 - 2:51So that's how the sun wound up with all the elements.
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2:51 - 2:53It's still mostly hydrogen at 71 percent,
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2:53 - 2:56with most of the rest being helium at 27 percent.
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2:56 - 2:56But bear in mind
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2:56 - 2:58that while the first stars were made up
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2:58 - 3:00of hydrogen and helium alone,
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3:00 - 3:01the remaining elements in the periodic table
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3:01 - 3:04make up two percent of the sun.
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3:04 - 3:05And what about Earth?
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3:05 - 3:08Planets form as an incidental process to star formation
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3:08 - 3:11out of the same gas cloud as the star itself.
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3:11 - 3:13Small planets like ours don't have enough gravity
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3:13 - 3:16to hold on to much hydrogen or helium gas
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3:16 - 3:18since both of those are very light.
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3:18 - 3:20So, even though carbon, nitrogen, oxygen and so on
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3:20 - 3:24made up only two percent of the gas cloud from which Earth was formed,
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3:24 - 3:26these heavier elements form the bulk of our planet
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3:26 - 3:28and everything on it.
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3:28 - 3:30Think about this:
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3:30 - 3:32with the exception of hydrogen and some helium,
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3:32 - 3:33the ground you walk on,
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3:33 - 3:35the air you breath, you,
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3:35 - 3:37everything is made of atoms
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3:37 - 3:39that were created inside stars.
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3:39 - 3:41When scientists first worked this out
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3:41 - 3:43over the first half of the 20th Century,
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3:43 - 3:45the famous astronomer Harlow Shapley commented,
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3:45 - 3:49"We are brothers of the boulders, cousins of the clouds."
- Title:
- What is the universe made of? - Dennis Wildfogel
- Speaker:
- Dennis Wildfogel
- Description:
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View full lesson: http://ed.ted.com/lessons/what-is-the-universe-made-of-dennis-wildfogel
The atoms around you have existed for billions of years -- and most originated in the flaming, gaseous core of a star. Dennis Wildfogel tells the captivating tale of these atoms' long journeys from the Big Bang to the molecules they form today.
Lesson by Dennis Wildfogel, animation by Pew36 Animation Studios.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TED-Ed
- Duration:
- 04:05
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Leonardo Silva
Hi. I guess there's a minimal typo here: 0:45 - 0:47 ("stars", instead of "starts"). Best.