Cassandra is giving a class presentation that involves a demonstration where she sprinkles some glitter into a small shallow dish of water and circularly swirls the water around with her finger. When she removes her finger, she asks her classmates to notice how the glitter moves around like a whirlpool, spiraling around the spot where she had removed your finger. What is Cassandra modeling with this demonstration?
how two galaxies collide
how the Milky Way galaxy appears
how the arms in a galaxy interact
how the nuclear bulge of a galaxy moves