How to build a clock that detects gravity

Adapted from "THE BELLS OF OLD TOKYO: Meditations on Time and a City" by Anna Sherman. “We’re on the brink of realizing Dalí’s vision.” I glanced up at "The Persistence of Memory": eroded escarpments, barren plain, ants swarming over a watch’s case. My dream is to change that, to make everyone understand Einstein’s concept of time.” “How would you do that?” “If you put two of my clocks, far apart from each other, and something heavy moves, the two clocks could detect it — ” “ — because the clock nearer the heavy thing would run slower —” “Yes! “So in the future, one of the two clocks would be able to tell time before things happen; but yet, that clock would still be a clock, just… not a clock… of the present moment…” Katori smiled. But my clocks will show that we don’t share time: my clocks show that every person’s space-time is different.” “Your clock doesn’t sound like a clock anymore!” Katori grinned.