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Narrator: This demonstration explores what happens inside a large
star when fusion stops at the end of its life. You're going to need
an empty aluminum soda can, a hot
plate, some water,
something to measure the water with, like a tablespoon,
a bowl of ice water, and a pair of tongs
to flip the can over. First, place a small amount of water inside the aluminum
soda can, about a tablespoon or two. Set the can on the
hot plate, and heat until the water starts to boil. Listen for the sound
of the water boiling and look for steam coming out of the top. When plenty of
steam is coming out of the top of the soda can, quickly pick it up with the tongs and
flip it over, open side down, into the bowl of ice water. It helps to use
an underhand motion, so you can easily flip your wrist over and dunk the can.
The can will implode, just like the core of a large star.
This activity is all about balance, or equilibrium. When you
have an empty soda can, the air pressure on the inside and the air pressure outside
are in equilibrium. When the water boils and you have steam,
the steam on the inside is still in equilibrium with the air pressure on the outside.
But once that steam turns into liquid water, that equilibrium is broken and the can
collapses. Similarly, in a star, you have a balance between
the energy from fusion pushing outwards, and gravity holding the star together for the
majority of the star's life. But when fusion stops, all of a sudden that
equilibrium is broken and the star collapses, just like the can.
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