My subject disperses the galaxies, but it unites the earth.

May no “cosmical repulsion” intervene to sunder us!

—SIR ARTHUR EDDINGTON

When I throw my keys up in the air, they reach some maximum height, and then they fall back into my hand. Only for an instant do the keys stay still, as they reach the highest point. Obviously, the gravitational pull of the Earth is responsible for this behavior. If somehow I could propel the keys to a speed exceeding about seven miles per second, they would escape the Earth altogether, as did, for instance, the Pioneer 10 spacecraft, with which communication was lost in 2003, when the probe was at a distance of more than seven billion miles from Earth. However, in the absence of an opposing force, the Earth’s gravity alone does not allow for the keys to float suspended in midair.