The Nobel prize winning molecular biologist Venki Ramakrishnan explores how time affects our bodies, brains and emotions in his new book, Why We Die: The New Science of Ageing and the Quest for Immortality. As he explains the recent scientific breakthroughs to extend lifespan by altering our biology, he also considers the ethical questions such efforts raise. The neuroscientist Charan Ranganath asks a different question in his book, Why We Remember. Using case studies he unveils the principles behind how the brain retains information, and what and why we forget so much. He also looks at what happens to our memories as we age. In her new book, Nostalgia, the historian Agnes Arnold-Forster blends social history and psychology in a quest to understand this complex emotion. While it was thought of as an illness in the 17th century, it is now used as a widespread marketing tool impacting our choices from politics to food. But if nostalgia prompts us to glorify the past, Arnold-Foster asks how that impacts the present, and future. Producer: Katy Hickman