Figure 8
The illustration is a simple schematic on a white background. On the left is a large mound of yellow‑brown soil labeled “Mass m subscript 1”. In the center is a yellow haul truck facing to the right, positioned between the two piles. On the right is a smaller conical soil pile labeled “Mass m subscript 2”. Along the bottom of the image, a long horizontal arrow runs from beneath the left pile toward the right pile and is labeled “Distance d”, indicating the separation between the two masses.Earth mover's distance: energy required to move the mass over a distance