Decomposing geographical and universal aspects of human mobility

Driven by access to large volumes of detailed movement data, the study of human mobility has grown rapidly over the past decade. This body of work has argued that human mobility is scale-free, has proposed models to generate scale-free moving distance distribution, and explained how the scale-free distribution arises from aggregating displacements across scales. However, the field of human mobility has not explicitly addressed how mobility is structured by geographical constraints - such as the outlines of landmasses, lakes, rivers, the placement of buildings, roadways, and cities. Using unique datasets capturing millions of movements between precise locations, this paper shows how separating the effect of geography from mobility choices reveals a universal power law spanning five orders of magnitude (from 10 m to 1,000,000 m). We incorporate geography through the pair distribution function, a fundamental quantity from condensed matter physics that encapsulates the structure of locations on which mobility occurs. This distribution captures the constraints that geography places on human mobility across different length scales. Our description conclusively addresses debates between distance-based and opportunity-based perspectives on human mobility. By demonstrating how the spatial distribution of human settlements shapes human mobility, we provide a novel perspective that bridges the gap between these previously opposing ideas.