Systems like the bullet cluster (https://en.wikipedia.org/wiki/Bullet_Cluster https://en.wikipedia.org/wiki/Bullet_Cluster) are taken as evidence that most of t

Systems like the bullet cluster (https://en.wikipedia.org/wiki/Bullet_Cluster https://en.wikipedia.org/wiki/Bullet_Cluster) are taken as evidence that most of the matter in large-scale, gravitationally bound astrophysical systems does not behave like luminous matter.