When we started class, Jared was browsing through images (artistic reproductions) of accretion disks being distorted by the strong gravitational fields of black holes (this is due to light-bending, not the actual distortion of the disks). So I thought to introduce him to the topic of 'gravitational lensing' and the Einstein Cross. This is a phenomenon whereby a massive object, e.g. a galaxy, sits between us and a distant quasar, and its gravitational field bends the light emanating from the quasar. More proof that Einstein was on the right track with his Theory of General Relativity! Then, to continue with catastrophes that may befall Earth (following on from Gamma-Ray Bursts yesterday) we watched a National Geographic documentary on the great scientist Eugene Shoemaker, and his growing understanding and lifelong commitment to studying impacts on Earth caused by asteroids, and the threat they pose to life on Earth. As always when we watch a documentary, we paused regularly to address scientific issues presented.