Sorry to keep on asking these questions, but in the Jupiter scenario, why is Earth’s density 5.5 and not 1?
Because, Density is subjective to Mass and Volume.
Density=mass/volume
Density is based on the weight of water, about 62 pounds per cubic foot. A cubic foot of rocky earth is 5.5 times as heavy as an equal volume of water. You can check this out. Drop a rock in a bucket of water. If it sinks it is heavier than water.
Godspeed, The Dilg