As the late, great astrophysicist Carl
Sagan put it, “we are made of star stuff.
We are a way for the cosmos to know itself.”
Whoa! It’s an amazing idea.
And its not a metaphor.
Many of the atoms that make up you and
everything else in the world were literally
forged in the nuclear cores of stars.
You’ve seen the periodic table in chemistry class.
But where did the elements on that table come from?
For centuries, the thinking was
that they didn’t come from anywhere.
They were as old as the universe.
They simply…existed.
Later, scientists reasoned that elements
originated from the big bang.
After all, they thought it made sense
that the explosive pinprick that started
everything 14 billion years ago would
also spew out all of the elements.
That is until about 60 years ago.
For more, we talked to best-selling author
and periodic table super-fan Sam Kean.
“A group of scientists came up
with an interesting alternative.
They suggested the universe was once a sea of
hydrogen, with a smattering of helium and lithium.
Eventually, hydrogen atoms clumped together
into stars, and the extreme gravitational
pressure inside these stars began fusing
hydrogen atoms into helium atoms, the reaction
that lights up every star in the sky. “
Alright cool.
We’ve got stars in our new universe.
But after a few billion years, those
stars begin to run out of hydrogen fuel.
Once this happens, stars lacking hydrogen
fuse helium in their cores instead.
Sometimes helium atoms stick together
and form even numbered elements.
Sometimes helium gets split up and
its protons and neutrons break off
to create odd numbered elements.
So our stars have switched to burning
off helium instead of hydrogen.
Why don’t we have Sam explain what happens next.
“After a few hundred million years,
stars deplete their helium supply.
Some die. But bigger, heavier stars
-- we’re talking at least eight
times more massive than the sun
– move on to crush carbon together
into six more elements up to magnesium.”
Alright by this point the stars are
burning hot and by hot i mean hot.
The biggest stars are burning around five billion degrees.
So as the stars burn,
this snowball effect where stars burn
off lighter elements and start fusing
heavier ones together keeps on rolling.
Eventually a stable version of
every element up to number 26,
iron is out there in the universe.
So where does that leave elements 27 through 92?
Scientists suspect they come from mini big bangs
that happen when those big heavy stars die.
“As they burn through elements such as
magnesium and silicon, extremely massive stars
at least 12 times the size of the sun burn
down to iron cores in about one Earth day.
But before perishing,
there’s an apocalyptic death rattle.
Burned-out stars implode under their
own immense gravity, collapsing
thousands of miles in just seconds.
Then, rebounding from this collapse,
they explode outward. And I mean explode.
For one glorious month, a supernova
stretches millions of miles and
shines brighter than a billion stars.
Every natural combination of element and
isotope spews from this particle blizzard.”
So why should you care where all this
stuff on that periodic table came from?
Well without the nuclear furnaces in the sky
to create carbon, oxygen, and nitrogren from
hydrogen and helium, and without those massive
explosions, earth, and you, would have
never been formed to watch this awesome video.
Do you love this video?
You want more?
Share it, like it, and subscribe!
And be sure to check out Sam’s
other video on mega sharks.
For more amazing videos about the elements,
head to teachchemistry.org and join the
American Association of Chemistry Teachers.
For 50 bucks, you get access to exclusive
videos, a magazine, a periodical
about teaching chemistry, and more.
It makes a great gift for your
favorite teacher or science geek…
Also check out Sam’s excellent book,
“the Disappearing Spoon,” available in
fine bookstores and internets everywhere.
Thanks to AACT and Sam Kean
for making these videos happen.