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].

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Dennis Veasley

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