Of Gas And Dust

I had a question on my mind a couple of days ago - why do gas giants have shorter days as compared to the terrestrial planets?

Note: Pluto is no longer a planet.

It's perfectly understandable that the outer-most planet has the longest year. We can totally relate to that. Just imagine 8 children are taking part in a running competition and are placed on 8 lanes abreast of each other at the same starting line. Let's also assume that all 8 children run at the same speed. Of course, the child at the inner-most lane is going to finish first as he has the shortest distance to cover.

However, I found it most counter-intuitive that the biggest planet, Jupiter, a gas giant, has the shortest day among the rest. I mean, there's more surface area to contend with, take for example, if you spin both a basketball and a small marble at the same time and with the same strength, then by logic and science, the small marble is going to complete a full rotation first, right? That's also how the gear ratio in our vehicle transmission system works. 

That is true for the basketball and marble and gears. So, I was confused about why Jupiter rotates the fastest in our Solar System. Hence, I went to look for some answers on Google.

Bear in mind that I am still not quite sure of what I have read. It's just a basic understanding that I have formed. If you are reading this, please feel free to correct me if I am wrong or add on to the knowledge pool if you have something to share. At the meantime, take what I am about to write with a pinch of salt.

I think the keyword here is: Gas giant.

We can't use the same measurement on the gas planets like we do on the terrestrial planets. While the rocky planets rotate on their solid mass, gas planets rotate atmospherically and are very turbulent. Jupiter's atmosphere rotates at about 45,000km/h and its day lasting only 9.9 hours. The absence of landmass also contributes to the wind's breakneck speed as there is no friction to slow it down like how Earth's landmass saps the energy of a hurricane and slows it down once it comes ashore from the ocean,

All this business about solid and gas has led me to reminiscence the times at school when we had to learn about the different states of matter and their properties. I guess basing on the states of matter, that is how the planets work as well. In a sense, solids are packed tightly together and do not have much freedom to roam about, hence it has to rotate as one solid mass, taking more time. Gas molecules are far apart and are free to move about. When more mass comes into play, gravity causes it to be more turbulent and to rotate at a great speed, like the massive Jupiter.