Earth and moon, e.g.

• Music of the ___
• They lack edges
• Juggler's objects
• Ball bearings, e.g.
• Mercury and Saturn
• The sun and moon, for two
• "Music of the ---" (Kepler assertion)
• Areas of interest

Wikipedia Word definitions in Wikipedia
The Synchronized Position Hold Engage and Reorient Experimental Satellite (SPHERES) are a series of miniaturized satellites developed by MIT 's Space Systems Laboratory for NASA and US Military, to be used as a low-risk, extensible test bed for the development ...