So, maybe matter alone isn't what causes spacetime to curve. Maybe spacetime is already curved, to the equivalent of 5-times as much matter as what actually exists. This curvature manifests as the cosmic web, a complex mesh of interconnected tendrils of curved spacetime, around which galaxies tend to cluster.



This complex topology of curved spacetime might be similar to the dimpled surface of a golf ball. These spacetime dimples might trap galaxies of matter. As the universe expands, galaxies are carried along inside their local "dimple" of spacetime.