Part 8/10:
A powerful piece of evidence for the existence of dark matter comes from the Bullet Cluster, which consists of two galaxy clusters colliding at high speeds. This phenomenon has provided a unique snapshot of the contrasting behaviors between ordinary and dark matter during a collision. While the hot gas (ordinary matter) slows down due to friction, dark matter continues to move unhindered, creating a separation in their distributions.
The gravitational lensing studies conducted on the Bullet Cluster reveal that most of the mass lies in the regions dominated by dark matter, not in the hot gas. This clear distinction supports the hypothesis that dark matter interacts solely through gravity, further distinguishing it from ordinary matter.