Dark energy is cosmology’s biggest mystery—an anti-gravitational force that confounds the conventional laws of physics. It makes up more than two-thirds of the cosmos, but science is still grappling to explain what dark energy actually is.

Meet Dr. Nora Volkow, whose research on drugs and the brain helped us understand addiction as a disease. Nora Volkow is the director of the National Institute on Drug Abuse. …

Lemurs, capuchin monkeys, and macaques help cognitive psychologist Laurie Santos understand how we think and are able to use tools, do math, and perform other tasks that make us human. …

Join Turing Prize winner Yann LeCun and other pioneers in artificial intelligence for a no-nonsense discussion of whether a truly intelligent machine can be created—and, if so, how and when. …

For all their historical tensions, scientists and religious scholars from a wide variety of faiths ponder many similar questions—how did the universe begin? How might it end? What is the origin of matter, energy, and life?

Though many animals display cooperative behavior, human cooperation is distinct. Alan Alda hosts E.O. Wilson, Sarah Hrdy and other leading evolutionary biologists, anthropologists and humanitarians as they examine the origins and evolution of human cooperative behavior.