[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:07.12,0:00:08.77,Default,,0000,0000,0000,,All the material objects around you
Dialogue: 0,0:00:08.77,0:00:10.40,Default,,0000,0000,0000,,are composed of submicroscopic units
Dialogue: 0,0:00:10.40,0:00:12.15,Default,,0000,0000,0000,,we call molecules.
Dialogue: 0,0:00:12.15,0:00:13.40,Default,,0000,0000,0000,,And molecules in turn are composed
Dialogue: 0,0:00:13.40,0:00:15.15,Default,,0000,0000,0000,,of individual atoms.
Dialogue: 0,0:00:15.15,0:00:16.98,Default,,0000,0000,0000,,Molecules frequently break apart
Dialogue: 0,0:00:16.98,0:00:19.06,Default,,0000,0000,0000,,and then form new molecules.
Dialogue: 0,0:00:19.06,0:00:20.31,Default,,0000,0000,0000,,On the other hand,
Dialogue: 0,0:00:20.31,0:00:22.25,Default,,0000,0000,0000,,virtually all the atoms you come in to contact with
Dialogue: 0,0:00:22.25,0:00:23.81,Default,,0000,0000,0000,,through the course of your life,
Dialogue: 0,0:00:23.81,0:00:25.42,Default,,0000,0000,0000,,the ones in the ground beneath you,
Dialogue: 0,0:00:25.42,0:00:27.42,Default,,0000,0000,0000,,the air you breath, the food you eat,
Dialogue: 0,0:00:27.42,0:00:29.71,Default,,0000,0000,0000,,those that make up every living thing, including you,
Dialogue: 0,0:00:29.71,0:00:31.90,Default,,0000,0000,0000,,have existed for billions of years
Dialogue: 0,0:00:31.90,0:00:34.88,Default,,0000,0000,0000,,and were created in places very unlike our planet.
Dialogue: 0,0:00:34.88,0:00:38.35,Default,,0000,0000,0000,,How those atoms came about is what I want to share with you.
Dialogue: 0,0:00:38.35,0:00:39.93,Default,,0000,0000,0000,,It all started 14 billion years ago
Dialogue: 0,0:00:39.93,0:00:41.68,Default,,0000,0000,0000,,with an event we call The Big Bang,
Dialogue: 0,0:00:41.68,0:00:44.86,Default,,0000,0000,0000,,which resulted in a universe consisting of gas alone.
Dialogue: 0,0:00:44.86,0:00:46.90,Default,,0000,0000,0000,,There were no stars and no planets.
Dialogue: 0,0:00:46.90,0:00:48.48,Default,,0000,0000,0000,,The gas was made up only of atoms
Dialogue: 0,0:00:48.48,0:00:50.48,Default,,0000,0000,0000,,belonging to the simplest elements.
Dialogue: 0,0:00:50.48,0:00:52.31,Default,,0000,0000,0000,,It was about 75 percent hydrogen
Dialogue: 0,0:00:52.31,0:00:54.40,Default,,0000,0000,0000,,and almost all the rest was helium.
Dialogue: 0,0:00:54.40,0:00:57.31,Default,,0000,0000,0000,,No elements like carbon, oxygen or nitrogen existed.
Dialogue: 0,0:00:57.31,0:00:59.40,Default,,0000,0000,0000,,No iron, silver or gold.
Dialogue: 0,0:00:59.40,0:01:03.15,Default,,0000,0000,0000,,In some places, the density of this gas was slightly higher than in others.
Dialogue: 0,0:01:03.16,0:01:05.98,Default,,0000,0000,0000,,Due to gravity, those places attracted even more gas,
Dialogue: 0,0:01:05.98,0:01:07.98,Default,,0000,0000,0000,,which further strengthened the pull of gravity,
Dialogue: 0,0:01:07.98,0:01:10.67,Default,,0000,0000,0000,,which then drew more gas in, and so on.
Dialogue: 0,0:01:10.67,0:01:13.51,Default,,0000,0000,0000,,Eventually, large dense gas balls formed,
Dialogue: 0,0:01:13.51,0:01:15.31,Default,,0000,0000,0000,,shrinking under their own gravity
Dialogue: 0,0:01:15.31,0:01:18.06,Default,,0000,0000,0000,,and consequently heating up on the inside.
Dialogue: 0,0:01:18.06,0:01:19.64,Default,,0000,0000,0000,,At some point, the core of such a ball
Dialogue: 0,0:01:19.64,0:01:22.15,Default,,0000,0000,0000,,gets hot enough that nuclear fusion occurs.
Dialogue: 0,0:01:22.15,0:01:24.90,Default,,0000,0000,0000,,Hydrogen atoms smash together to form helium,
Dialogue: 0,0:01:24.90,0:01:27.06,Default,,0000,0000,0000,,accompanied by a great release of energy,
Dialogue: 0,0:01:27.06,0:01:30.56,Default,,0000,0000,0000,,strong enough to counteract the shrinking force of the gravity.
Dialogue: 0,0:01:30.56,0:01:32.56,Default,,0000,0000,0000,,When the energy pushing out from the fusion reactions
Dialogue: 0,0:01:32.56,0:01:35.11,Default,,0000,0000,0000,,matches the gravity pulling all the gas inwards,
Dialogue: 0,0:01:35.11,0:01:37.06,Default,,0000,0000,0000,,an equilibrium occurs.
Dialogue: 0,0:01:37.06,0:01:39.37,Default,,0000,0000,0000,,From this a star is born.
Dialogue: 0,0:01:39.37,0:01:40.37,Default,,0000,0000,0000,,Over its lifetime,
Dialogue: 0,0:01:40.37,0:01:42.48,Default,,0000,0000,0000,,the fusion reactions in the core of a massive star
Dialogue: 0,0:01:42.48,0:01:44.06,Default,,0000,0000,0000,,will produce not only helium,
Dialogue: 0,0:01:44.06,0:01:46.21,Default,,0000,0000,0000,,but also carbon, oxygen, nitrogen
Dialogue: 0,0:01:46.21,0:01:50.12,Default,,0000,0000,0000,,and all the other elements in the periodic table up to iron.
Dialogue: 0,0:01:50.12,0:01:52.15,Default,,0000,0000,0000,,But eventually, the core's fuel runs out,
Dialogue: 0,0:01:52.15,0:01:54.09,Default,,0000,0000,0000,,leaving it to collapse completely.
Dialogue: 0,0:01:54.09,0:01:56.26,Default,,0000,0000,0000,,That causes an unbelievably powerful explosion
Dialogue: 0,0:01:56.26,0:01:58.48,Default,,0000,0000,0000,,we call a supernova.
Dialogue: 0,0:01:58.48,0:01:59.60,Default,,0000,0000,0000,,Now there are two things to note
Dialogue: 0,0:01:59.60,0:02:01.56,Default,,0000,0000,0000,,about how supernovas create elements.
Dialogue: 0,0:02:01.56,0:02:04.31,Default,,0000,0000,0000,,First, this explosion releases so much energy
Dialogue: 0,0:02:04.31,0:02:05.94,Default,,0000,0000,0000,,that fusion goes wild
Dialogue: 0,0:02:05.94,0:02:08.56,Default,,0000,0000,0000,,forming elements with atoms even heavier than iron
Dialogue: 0,0:02:08.56,0:02:10.90,Default,,0000,0000,0000,,like silver, gold and uranium.
Dialogue: 0,0:02:10.90,0:02:12.73,Default,,0000,0000,0000,,Second, all the elements that had been accumulating
Dialogue: 0,0:02:12.73,0:02:14.14,Default,,0000,0000,0000,,in the core of the star,
Dialogue: 0,0:02:14.14,0:02:16.70,Default,,0000,0000,0000,,like carbon, oxygen, nitrogen, iron,
Dialogue: 0,0:02:16.70,0:02:19.56,Default,,0000,0000,0000,,as well as all of those formed in the supernova explosion,
Dialogue: 0,0:02:19.56,0:02:21.98,Default,,0000,0000,0000,,are ejected in to interstellar space
Dialogue: 0,0:02:21.98,0:02:24.40,Default,,0000,0000,0000,,where they mix with the gas that's already there.
Dialogue: 0,0:02:24.40,0:02:26.48,Default,,0000,0000,0000,,History then repeats itself.
Dialogue: 0,0:02:26.48,0:02:28.67,Default,,0000,0000,0000,,Gas clouds, now containing many elements
Dialogue: 0,0:02:28.67,0:02:31.08,Default,,0000,0000,0000,,besides the original hydrogen and helium,
Dialogue: 0,0:02:31.08,0:02:32.55,Default,,0000,0000,0000,,have higher density areas
Dialogue: 0,0:02:32.55,0:02:34.67,Default,,0000,0000,0000,,that attract more matter, and so on.
Dialogue: 0,0:02:34.67,0:02:37.55,Default,,0000,0000,0000,,As before, new stars result.
Dialogue: 0,0:02:37.55,0:02:40.30,Default,,0000,0000,0000,,Our sun was born this way about 5 billion years ago.
Dialogue: 0,0:02:40.30,0:02:42.23,Default,,0000,0000,0000,,That means that the gas it arose from
Dialogue: 0,0:02:42.23,0:02:44.27,Default,,0000,0000,0000,,had itself been enriched with many elements
Dialogue: 0,0:02:44.27,0:02:47.98,Default,,0000,0000,0000,,from supernova explosions since the universe began.
Dialogue: 0,0:02:47.98,0:02:50.65,Default,,0000,0000,0000,,So that's how the sun wound up with all the elements.
Dialogue: 0,0:02:50.65,0:02:52.86,Default,,0000,0000,0000,,It's still mostly hydrogen at 71 percent,
Dialogue: 0,0:02:52.86,0:02:55.56,Default,,0000,0000,0000,,with most of the rest being helium at 27 percent.
Dialogue: 0,0:02:55.56,0:02:56.48,Default,,0000,0000,0000,,But bear in mind
Dialogue: 0,0:02:56.50,0:02:57.81,Default,,0000,0000,0000,,that while the first stars were made up
Dialogue: 0,0:02:57.81,0:02:59.65,Default,,0000,0000,0000,,of hydrogen and helium alone,
Dialogue: 0,0:02:59.65,0:03:01.48,Default,,0000,0000,0000,,the remaining elements in the periodic table
Dialogue: 0,0:03:01.48,0:03:03.73,Default,,0000,0000,0000,,make up two percent of the sun.
Dialogue: 0,0:03:03.73,0:03:05.15,Default,,0000,0000,0000,,And what about Earth?
Dialogue: 0,0:03:05.15,0:03:07.100,Default,,0000,0000,0000,,Planets form as an incidental process to star formation
Dialogue: 0,0:03:07.100,0:03:11.13,Default,,0000,0000,0000,,out of the same gas cloud as the star itself.
Dialogue: 0,0:03:11.13,0:03:13.04,Default,,0000,0000,0000,,Small planets like ours don't have enough gravity
Dialogue: 0,0:03:13.04,0:03:15.59,Default,,0000,0000,0000,,to hold on to much hydrogen or helium gas
Dialogue: 0,0:03:15.59,0:03:17.67,Default,,0000,0000,0000,,since both of those are very light.
Dialogue: 0,0:03:17.67,0:03:20.31,Default,,0000,0000,0000,,So, even though carbon, nitrogen, oxygen and so on
Dialogue: 0,0:03:20.31,0:03:23.73,Default,,0000,0000,0000,,made up only two percent of the gas cloud from which Earth was formed,
Dialogue: 0,0:03:23.73,0:03:26.31,Default,,0000,0000,0000,,these heavier elements form the bulk of our planet
Dialogue: 0,0:03:26.31,0:03:28.27,Default,,0000,0000,0000,,and everything on it.
Dialogue: 0,0:03:28.27,0:03:29.52,Default,,0000,0000,0000,,Think about this:
Dialogue: 0,0:03:29.52,0:03:31.64,Default,,0000,0000,0000,,with the exception of hydrogen and some helium,
Dialogue: 0,0:03:31.64,0:03:33.14,Default,,0000,0000,0000,,the ground you walk on,
Dialogue: 0,0:03:33.14,0:03:35.23,Default,,0000,0000,0000,,the air you breath, you,
Dialogue: 0,0:03:35.23,0:03:36.81,Default,,0000,0000,0000,,everything is made of atoms
Dialogue: 0,0:03:36.81,0:03:38.73,Default,,0000,0000,0000,,that were created inside stars.
Dialogue: 0,0:03:38.73,0:03:40.81,Default,,0000,0000,0000,,When scientists first worked this out
Dialogue: 0,0:03:40.81,0:03:42.73,Default,,0000,0000,0000,,over the first half of the 20th Century,
Dialogue: 0,0:03:42.73,0:03:45.03,Default,,0000,0000,0000,,the famous astronomer Harlow Shapley commented,
Dialogue: 0,0:03:45.03,0:03:48.62,Default,,0000,0000,0000,,"We are brothers of the boulders, cousins of the clouds."