Atomic clocks have gotten so accurate that the gravitational slowing of time can actually be observed. What this means is that two identical clocks at two different elevations won’t tell the same exact time (off by say two ten-thousandths of a second). Neither clock is wrong. They’re just telling time in a different kind of space. One of which is closer to the center of the earth and thus experiencing a stronger gravitational pull. Witnessing this “fourth dimension” as Jakob Flury calls it is truly seeing Albert Einstein’s theory of general relativity in action.
What makes this so useful is that it could help us better understand different geographical terrains. The scientific umbrella that this is under is called “Geodesy” which is the science of understanding the Earth’s geometric shape, orientation in space, and gravitational field.