Music
Narrator: In this activity, you'll model and measure the collapse of a large star to
understand the important role of density in black holes. You'll need a
latex balloon, blown-up to 6-8 inches in diameter, a few
sheets of aluminum foil, a digital scale,
a flexible tape measure,
and a pair of scissors, or another sharp implement.
Completely wrap the balloon in the aluminum foil, when you're done wrapping, you don't
want to see any of the balloon peeking out. It may take a few sheets of foil to
do this, depending on the size of the balloon, so use whatever you need. This
foil-wrapped balloon represents a large star.
Measure the circumference of the balloon with the tape measure and weigh the balloon on the scale. Record your
baseline measurements. Gently squeeze the balloon, here
you are the giant "hands" of gravity and the balloon should resist being squeezed
because of the air pressure within the balloon. This is similar to what happens
during the normal life a star, when gravity is balanced by fusion energy
created at the core of the star. Now you're ready to simulate the end of the star's
life as it runs out of fuel and that balance is broken. Pop the balloon
carefully, trying not to crush the aluminum foil as you pop it.
Be the hands of gravity again and gently squeeze the aluminum ball.
This time, it doesn't push back. Make it about an inch smaller,
keeping it as round as possible. Again, measure its circumference and weight,
and record your new measurements. You'll repeat
those steps a few more times, crushing down the foil ball about an inch more between measurements.
For you final measurement, crush the ball as much as you possibly can,
while keeping it round. Take one final measurement of its circumference and weight.
You'll see that even though the size of the ball changed, its mass did not.
This means that it just got more and more dense, like when a star collapses
into a black hole.
Music