Sagan discusses comets and asteroids as planetary impactors, giving recent examples of the Tunguska event and a lunar impact described by Canterbury monks in 1178. It moves to a description of the environment of Venus, from the previous fantastic theories of people such as Immanuel Velikovsky to the information gained by the Venera landers and its implications for Earth's greenhouse effect. The Cosmos Update highlights the connection to global warming.
Prof Jim Al-Khalili tackles the biggest subject of all, the universe, through a series of critical observations and experiments that revolutionised our understanding of our world. Part 1: Beginning Professor Jim Al-Khalili takes us back in time to tackle the greatest question in science: how did the universe begin? Uncovering the origins of the universe is regarded as humankind's greatest intellectual achievement. By recreating key experiments Jim unravels the cosmic mystery of science's creation story before witnessing a moment, one millionth of a second, after the universe sprang into existence.