Estimate the mass of the gravitational field of the Earth. What would the size of a cube of water with the same mass?
Use the following info (the real info is complex, but the following is close enough):
Relative density of inner core = 13, radius = 400 km
Relative density of outer core = 11, radius = 3400 km
Relative density of outer layers = 4.5, radius = 6400 km