You're ten years old and stumped for a fourth-grade science project, so you wheedle me for help. Here's what we come up with.
Inside an empty coffee can we hang a center weight, a solid bolt and a heavy nut; we suspend the load from two looped rubber bands. One band snakes through holes we've cut in the bottom of the can; the other does the same through slits in the plastic lid. When you roll this creation down the hall, the center weight anchors the rubber bands as they twist about themselves. Like whirling dervishes, they dance with their hands in the air while their feet remain mired in clay.
The tension generated by all this twisting eventually makes the can comes to a stop of its own accord; it hesitates, and then the bands inside unwind. As the energy caught inside overcomes the inertia of the can, it returns to you, the sender, coming to rest for a moment at your feet. But this journey home has wound it up again, and so the can does a short reprise of its flight, moving off to stop at last just beyond your reach.
You turn to me and beam with your delight.
As with any experiment, my darling daughter, more trial runs are now in order. I give you a push; you roll off merrily down the hall ahead of me. I hope I'm wound within you, a balanced inner combination: a solid core anchoring an elastic temperament. I want to help you find your own path out of here, but then I'll want to pull you almost all the way back to me. When you return, I know you’ll move off again on your own, but I hope it won't be so far away that we can't stay in touch.
C'mon, kid, let's see if our boomerang can.