95 Earth masses, held in a planet whose mean density is below that of water, make Saturn a rebuke to everyday intuition. It floats, in theory. Yet density is mass divided by volume, and Saturn's hydrogen and helium occupy such a huge volume that the average is about 0.69 grams per cubic centimeter.The floating line is less a party trick than a warning against trusting the eye. Looks lie here. Unli...More