How are galaxies important to our existence?
A) Without galaxies, there could not have been a Big Bang.
B) Without galaxies, the universe could not be expanding.
C) Galaxies prevent planets from leaving their orbits around stars; e. g., our galaxy prevents Earth from leaving its orbit of the Sun.
D) Galaxies recycle heavy elements produced in stars into future generations of stars.
E) Galaxies provide the gravity that prevents us from falling off Earth.