Question

how can earth be the densest of the three when uranus and neptune have so much more mass than earth does?

Answer 1

Density is not defined by mass, but how compact the mass is of a given planet. Earth has lots of heavy metals in it's core.

Answer 2

Well first of all who said that earth is the densest ?

Answer 3

Luis, I am God. I said it was. Therefore I am right.

Answer 4

density is mass per unit volume.
so if the mass is greater but the volume is even greater, then the density would decline.