Figure 1
Illustration: Alan Stonebraker, adapted from a NASA image

Figure 1: A small satellite moving under the influence of a sun-earth system will rotate in fixed relation to the sun-earth system if it is located near one of five Lagrange (L) points. The figure shows the equipotential lines of the effective potential in the rotating frame. In the atomic analog the effect of the earth is replaced by a circularly polarized microwave field so that the electronic wave packet moves without spreading around the nucleus following the direction of the microwave field. (Figure not to scale).