I missed a week last week for no good reason, but here is episode 4 of Cosmos, Heaven and Hell. Carl explores the hells on earth that can come from the heavens in the form of comet and meteor impacts on earth. He speculates on the cause of the Tunguska event in 1908, investigates the history of comet sightings and examines the impacts on our nearest celestial neighbor, the moon. This episode ends with Venus, with its hellish pressures, temperatures and sulfuric acid rain, our visits to the planet, and what Venus has to say about the greenhouse effect here on earth. Enjoy!