http://www.space.com/31290-gravitational-waves-lisa-pathfinder-launches.html

In 1915 Einstein predicted that there could be ripples in space time called gravitational waves.  The LISA Pathfinder mission hopes to find ripples in space time. This mission launched December fourth will take two weeks to reach a gradationally stable point between the earth and the sun.  Using two identical gold-platinum cubes that are released into free-fall.  With movement measured by lasers to determine their pure movement without external forces.  For this experiment to solely measure the cubes movements caused by gradational waves the cubes need to be away from any external movements such as space crafts.