Where are active satellites located? — The picture shows the distributions of apogee and perigee for man-made satellites orbiting the Earth, calculated using data from the Union of Concerned Scientists. Upper left: Distribution of perigee for all satellites. Upper right: Distribution of apogee for all satellites. Lower left: Distribution of perigee (gray bars with blue lining) and apogee (gray bars with red lining) for satellites in low-Earth orbit. Lower right: Distribution of perigee (gray bars with blue lining) and apogee (gray bars with red lining) for satellites in geostationary orbit.

Earth’s orbits are easily the largest physical commons humanity has ever used. But some orbits are more useful than others, leading to clustering. Space: the lonesome crowded frontier.