And it turns out that there's energy produced by that process that's
released as light and heat.
So if a star gets compressed enough, at that point the star has this energy
coming out that provides pressure that can hold it up.
So there's a balance point.
If you look at any star, it's almost like it's a nuclear explosion
going on that's being contained by gravity.
So there's this delicate balance going on between those two forces.
One trying to blow it apart and one trying to pull it together.
And a star like our sun can live in that state for well,
something like 10 billion years staying roughly in balance and able to support
itself against gravity and shine due to this nuclear fusion that's going on.
>> And provided all the sources of life.
>> Which provides the source of life directly and it also other generations of
stars, this process, when you fuse two protons together and
then build on that, you go from hydrogen you can build helium.
Out of helium, you can build carbon and heavier and heavier elements.
So generation after generation of stars going through this process, in one way or
another, has made all of the elements that fill in our periodic table and
that make up, you know materials in your finger nails and your blood and your skin.
So the only reason we're able to be here,
the only reason the periodic table has anything basically other than hydrogen and
helium in it is because of the stars and that process.
>> Todd, give us this sense of the amazing emergence and
death of stars, and how the elements actually come out of this process.
>> Yeah if you really stop to think,
we should feel a lot of gratitude towards stars, I think, because for one thing,
they go through very much a life cycle just like we do.
They have a time that they're were born, they have an infancy, they have a early
youth, they have a middle age, and they have a death, essentially.
And the basic process is that stars collapse under gravity.
They reach a point where there's a balance between the gravitational
force trying to collapse them, the energy from nuclear fusion as they
turn on element into another helping to support it, so there's a balance.
And then, depending on the type of star,
depending on how much mass it has, at some point it runs out of fuel.
More massive stars run out of fuel more quickly, kind of like rockstars.
Sort of the same deal right?
I mean, they have shorter lives.
So, more massive stars run out of fuel more quickly.
Less massive stars can live a lot longer.
But eventually they run out of fuel.
And if they're a less massive star, what happens is that they create what's
called a planetary nebula, which are these beautiful images you see in Hubble and
elsewhere, of material that has just sort of quietly floated away from the star
while the middle part, the core of the star forms into a white dwarf star.
It's kind of the dying ember of a star.
And those elements are then available to make stars and
other planets and life like us.
If you're a more massive star, you end your life in a supernova explosion,
which more violently sprays all the rest of the elements in the periodic table
out into the medium between the stars.
And that material is than available to be recycled into
what's called the interstellar medium, the material between the stars.
That material can be recycled.
And so, when our sun came along hundreds or
thousands of generations of some kinds of stars had already done this processing.
So when our solar system formed, we formed out of this recycled material and
kind of the ecosystem of our galaxy.
And so, that material is now what makes up the carbon in your skin,
the gold in your jewelry, the iron in your blood.
All those things are literally star dust, either blown off violently or
blown off quietly, depending on the type of star.
But thanks to stars, we actually have all that material that enables life to exist.
>> It's an amazing lineage, isn't it?
>> It is. >> Our ancestry all of a sudden is
extended so vastly into the very elements of ourselves and life on Earth.
>> That's absolutely right.
If you think about tracing your ancestry back to your mother or
father and her mother and father, you can trace it all the way back through,
of course, all the different animals and organisms.
But you can completely trace it back to,
there was the carbon that is in your fingertip, lived in a star somewhere.
That's part of your lineage.
>> Which is why it makes sense in a way, doesn't it, to tell this as a story.
As our story.
>> It is our common cosmic story.
>> Yeah, give us a feel for how you might see that.
The significance of this lineage and story for humans.
>> The way I think of it, is we kind of crave wonder.
We crave a sense that what we're doing is part of a mystery,
part of something deep and meaningful.
Which is sometimes hard to see when you're studying for
a test or filling out income tax forms or whatever.
It's hard to see that as, it feels mundane, right?
It's hard to see that as part of a magical, mysterious origin.
But if you can understand your lineage, then you can really see
every action you do is in a way a frozen creation.
If you can picture in your minds eye the thread that
connects whatever you're doing right at this moment to that lineage and
then ultimately back to the ultimate question of, how did it all begin?
Where did this all come from?
Then every action, the test that you're taking, the driver that you're angry
at that just cut you off in traffic, is part of that cosmic lineage.
And it has sort of a mystery and a wonder to it that I think changes how you look at
life and how you look at other people and how you look at other points of view.
In a way that you don't have if you're very narrow and
you don't see that lineage.
>> I think that's so true and so beautifully put.
And if we extend that lineage, what about the early universe?
And give us a feel for what was emerging, and
again, how we're part of that, even this expansion of the universe.
>> We also owe our existence to the fact that the universe is expanding, and
so we can think of tracing back that lineage as we did through the stars.
The first stars were thought to have formed probably 100 million or a few 100
million years after the beginning of our current universe as we know it.
So there was time before there were stars, and
we can't trace it back to the very beginning, but we can trace it back to
a time when all we know that it was just extremely hot and dense.
And if you had a suit that would protect you from the heat and radiation,
it would be like looking at this glowing uniform soup.
And something started that out and we don't know.
But everything was expanding, which drove everything else that happened.
Because if it hadn't been expanding it wouldn't have cooled down.
So, there's this expansion that allows things to cool.
And as things cool, it's very much like watching ice freeze for example, right?
You put a tray of water in our freezer and it's very smooth in uniform.
As it freezes, little imperfections, little irregularities crystallize out of
the smooth water, and in a way the history of the universe has been that sort of
crystallization of structure out of the that.
>> So in the early universe that you're describing, and
with this wonderful image of ice freezing and so on, what about the factor of time?
And how did that help shape this universe in it's early emergence?
>> One of the interesting things about the timeline is that in the very
early universe things happened very,
very quickly >> So for
example, there was thought to have been a time, a tiny tiny fraction of a second
on the order of ten to the minus 30 seconds, where there was this
rapid period of inflation where there universe expanded very very rapidly.
That created a lot of the seeds for
the density regions that we talked about that form galaxies and ultimately stars.
And then, I guess a really significant event about a few minutes after
the beginning, is when the basic hydrogen and helium elements formed.
So we talked about our cosmic lineage in the stars, elements beyond hydrogen and
helium mostly formed in the stars, hydrogen and
helium are formed imprinted a few minutes after the beginning of the universe.
Another key event, much later on now, about a little less
than 400,000 years after the beginning, was when for the first time it was cool
enough that electrons and protons could stick together.
Before that it was too hot.
So if an electron was stuck to a proton to make a hydrogen atom, it would
fly away because there was too much energy bouncing around and it would stay free.
The reason that was so
significant is that that was the point when the universe became transparent.