Edinburgh’s January sun sets by 4:30. Overcast skies and the sound effect of shoe soles on cobblestone exaggerate the slumber of winter. The streets are dreamy and tired. Insulated. Historical castles, squares, alleys, bridges, walking paths that go below the city streets and weave their way from center to suburbs, all grey and green and grey-green and new to me.


Do you understand potential energy? I remember the lesson in images from 12th grade physics class: a girl holding a ball, a car on a hill, an arrow in a flexed bow. The energy possessed by a body by virtue of its position relative to others. A pressure like water boiling in the muscles, restless energy that builds in the thighs, the calves, and the feet.


I’m in a hostel with dozens of other young travelers. We’re not sure what we’re looking for, but potential energy is what we find. Potential energy, when we ask ourselves why we keep moving, a matter of time and space from precipice to body at rest.