Take three masses two of them equal, with the two equal masses either

side of the other on a straigt line segment at a distance

from the

central mass. Then if the central mass is

and the other two are

both of mass

and (if I have done my sums correctly) the line segment

rotates about the central mass at an angular velocity of:

we will have a stable configuration.

(there should be a simpler configuration with just two masses but I

can't be bothered to look for it just now - I take that back, just let

. This is the simplest version of the rotating string of pearls

like configuration)

RonL