  Louis Poinsot has shown in 1854 that the motion of a rigid body, with one of
its points fixed, can be described as the rolling without slipping of one cone,
the 'body cone', along another, the 'space cone', with their common vertex at
the fixed point. This description has been further refined by the second author
in 1996, relating the geodesic curvatures of the spherical curves formed by
intersecting the cones with the unit sphere in Euclidean $\mathbb{R}^3$, thus
enabling a reconstruction of the motion of the body from knowledge of the space
cone together with the (time dependent) magnitude of the angular velocity
vector. In this article we show that a similar description exists for a time
dependent family of unimodular $ 2 \times 2 $ matrices in terms of rolling
cones in 3-dimensional Minkowski space $\mathbb{R}^{2,1}$ and the associated
'pseudo spherical' curves, in either the hyperbolic plane $H^2$ or its
Lorentzian analog $H^{1,1}$. In particular, this yields an apparently new
geometric interpretation of Schr\"odinger's (or Hill's) equation $ \ddot x +
q(t) x =0 $ in terms of rolling without slipping of curves in the hyperbolic
plane.
