Parabolic free surface of water in a rotating tank (left) and Jupiter’s oblate spheroid (exaggerated on the right).
Water placed in a rotating tank and insulated from external forces (both mechanical and thermodynamic) eventually comes into solid body rotation in which the fluid does not move relative to the tank. In such a state the free surface of the water is not flat but takes on the shape of a parabola. For the same reason rotating planets, such as the earth and, even more so, large, rapidly rotating planets such as Jupiter, are not perfectly spherical, but bulge at the equator. In this project we study why.