Name: 【TED-Ed】What is the universe made of? - Dennis Wildfogel
Uploaded: 2014-08-14T04:48:46.000Z
Duration: 4 min 5 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

Basic passive voice

virtually all the atoms you come in to contact with

those that make up every living thing, including you,

and were created in places very unlike our planet.

How those atoms came about is what I want to share with you.

which resulted in a universe consisting of gas alone.

No elements like carbon, oxygen or nitrogen existed.

In some places, the density of this gas was slightly higher than in others.

Due to gravity, those places attracted even more gas,

which further strengthened the pull of gravity,

Eventually, large dense gas balls formed,

and consequently heating up on the inside.

gets hot enough that nuclear fusion occurs.

Hydrogen atoms smash together to form helium,

accompanied by a great release of energy,

strong enough to counteract the shrinking force of the gravity.

When the energy pushing out from the fusion reactions

matches the gravity pulling all the gas inwards,

the fusion reactions in the core of a massive star

and all the other elements in the periodic table up to iron.

But eventually, the core's fuel runs out,

That causes an unbelievably powerful explosion

First, this explosion releases so much energy

forming elements with atoms even heavier than iron

Second, all the elements that had been accumulating

as well as all of those formed in the supernova explosion,

where they mix with the gas that's already there.

besides the original hydrogen and helium,

Our sun was born this way about 5 billion years ago.

had itself been enriched with many elements

from supernova explosions since the universe began.

So that's how the sun wound up with all the elements.

It's still mostly hydrogen at 71 percent,

with most of the rest being helium at 27 percent.

the remaining elements in the periodic table

Planets form as an incidental process to star formation

out of the same gas cloud as the star itself.

Small planets like ours don't have enough gravity

to hold on to much hydrogen or helium gas

So, even though carbon, nitrogen, oxygen and so on

made up only two percent of the gas cloud from which Earth was formed,

these heavier elements form the bulk of our planet

with the exception of hydrogen and some helium,

the famous astronomer Harlow Shapley commented,