Dark matter and the Bullet Cluster

[mmcirvin]

John Baez explains the evidence for dark matter provided by a remarkable object called the "Bullet Cluster": two clusters of galaxies collide and the hot gas is slowed down, but an invisible component detectable by gravitational lensing just keeps on going.

Comments

[avitzur.livejournal.com]

Sean Carroll at Cosmic Variance has another wonderful explanation at http://cosmicvariance.com/2006/08/21/dark-matter-exists/