Why do the Jovian planets have differential rotation and the Terrestrials do not?
It is a common error to mistake the observed rotation of Jupiter as rotation for the planet. What we are seeing is the rotation of a thick atmosphere, so thick that it makes up the majority of the planet’s size. The unseen solid core of Jupiter probably does rotate at something approximating a constant rate, but we can’t measure it. Saturn, on the other hand, may not have a solid core, though we have no way of being certain about that, either. There we may be seeing nothing but a rotating collection of gases. We observe differential rotation in Saturn’s atmosphere, too. One little thing of interest. Saturn’s mass/density is lower than water so, if we could find a body of water large enough, Saturn would float! The same holds for Uranus and Neptune. We are measuring the rotation rates of their atmospheres, not their solid cores. One tiny point of detail: If you measure the rotational rate of the thin skin of atmospheric gases surrounding Earth, you will get a differential, though slight
