Historian: Two days ago we enjoyed a great talk (linked to below) by Marcus du Sautoy given at the Royal Institution. He is a mathematician and is the Charles Simonyi Professor for the Public Understanding of Science at Oxford University. The talk is based on his new book What We Cannot Know. The talk is about an hour long with the questions session taking another half hour. This is time very well spent with very important ideas about science.
Physicist: In the book he goes to the edge of seven areas of knowledge to find any parts we cannot know. In the talk he spends most of his time on consequences of chaos theory and quantum physics. Chaos theory teaches us that, because of inevitable error in our knowledge of any reality, the future of that reality is not knowable. What quantum physics teaches us about knowledge is less clear. Wrestling with these questions is fundamental and I second my historical friend to most highly recomend the talk.