The core will collapse as density gets more and
more tightly packed as density increases dramatically.
And it keeps going, it doesn't go forever though.
And so the density reaches about two to three times
times ten to the 14 grams per CC.
200 to 300 trillion times the density of water, all of a sudden the rules change.
Before it was being governed to a first approximation by an ideal gas law, and
it's a little bit degenerate but it's mostly the ideal gas law.
When you reach a density of two to three times ten to the 14 grams per CC,
the star's core now has the density of an atomic nucleus and
now the strong nuclear force takes over.
Normally the strong nuclear force, which is what binds nuclei, binds protons and
neutrons into the nucleus.
Only occurs over the tiny, tiny, tiny space in the atomic nucleus,
but now the collapsing core is one big atomic nucleus in effect.
The radius is now ten kilometers, strong nuclear force comes into play.
So when we started a tenth of a second ago,
there were 3,000 kilometers across at ten billion times the density of water.
And just a little over a tenth of a second later we're ten kilometers across.
We've gone from the size of the Earth to the size of Columbus
in a tenth of a second.
The surface of that collapsing core is moving at one
tenth the speed of light, the strong nuclear force comes into play.
A strong nuclear force is a very strong property,
it's called the inner core force and it's repulsive, not attractive.
And so the thing is basically slamming down at a tenth the speed of light.
And all of a sudden the rules change,
the equation of state now suddenly becomes instantly repulsive.
And the collapse has to go from a tenth the speed of light to zero.
Well, it's not gonna stop on a dime, it's gonna collapse and it's gonna overshoot.
Spring is caught, know what happens when you let it loose?
[NOISE] Bounces back.
So the core is going from zero to a tenth the speed of light and then zero again.
It overshoots the strong nuclear force makes a spring and the core bounces.
The core in-falling envelope has also had the rug pulled out from underneath.
The core literally falls out from underneath the inside of the envelope and
[SOUND], where'd my core go?
What's he gonna do?
He's not going to stop it.
The outer envelope begins free-falling, chasing the core as it begins to collapse.
So we have him falling, free-falling envelope material.
We have the core collapsing, and it's speeding up and accelerating, and
suddenly, the core stops and bounces back, and smacks right into the gas.
What happens when the in-falling envelope gas hits that core
at a tenth the speed of light?
Well, we have to go back to the psyche of free fall.
Okay, the way free fall works is nothing impedes the fall of an object,
the fall of the parcel of gas.
But free fall has a rule, you start with the gravitational energy you began with,
and you turn that into kinetic energy as you fall.
When you bounce, you turn the direction of motion around, but
you don't get any more energy, in fact, you lose energy.
So I take this tennis ball, and I drop it from this height,
about my nose height, it loses some energy.
Where did some of that energy go?
Anybody got a guess where the energy went?
Let me do it again.
Pop [NOISE], made sound waves,
lost some of it's energy, where'd the rest of it go?
Someone carpeted the floor.
Okay, so a little bit of deformation energy.
So I free fall, I can only come back a little bit.
But I've also got the core falling, and the core springs back.
And when the in-falling gas hits the inner core, the core imparts
energy to the in-falling gas, and it robs some of that energy from the core.
So if I drop the basketball,
an NCAA regulation basketball with proper inflation, we're not the Patriots here.
>> [LAUGH] >> We go down, and it bounced back.
What if they come down and catch the bounce?
You all set there?
>> [LAUGH] >> Whoa.
>> You rob energy from the bouncing core and
you impart it [INAUDIBLE].
So the outflowing, no you can't keep that one.
>> [LAUGH] >> So, one more time just so
you can see that.
Your basic, now this is not exactly the physics that's going on.
It's a lot more complicated, as you might imagine.
But basically, you take energy from the bounce of the core and
you smash it into the envelope.
And you blast the envelope off.
That core bounce is what makes the kaboom.
That's what it happens with next [INAUDIBLE].