There's a gravitational pull between each pair of celestial bodies. The pull increases with the mass of the objects. The
Sun's mass is 1,989,000,000,000,000,000,000,000,000,000 kilograms, and Earth's mass is
5,972,600,000,000,000,000,000,000 kilograms. The Sun has more mass than Earth, so the force between them draws the
smaller Earth toward the Sun. This makes Earth go around the Sun. The mass of Earth is
5,972,600,000,000,000,000,000,000
kilograms, and the mass of the Moon is 73,477,000,000,000,000,000,000 kilograms.
Earth has more mass than the Moon, so the force between them draws the smaller Moon toward Earth. This makes the
Moon go around Earth. The Sun keeps Earth in orbit, and Earth keeps the Moon in orbit.
Part C
What would happen to the Moon and Earth if the Sun did not exist?