Astronomer Wendy Freedman sits down with Closer To Truth to discuss her work on the Hubble Constant, Standard Candles, the expansion of the universe, and the Giant Magellan Telescope.

Theoretical physicist Leonard Mlodinow, who spent nearly two decades collaborating with Stephen Hawking, joined Robert for a live discussion about his new book, Stephen Hawking: A Memoir of Friendship and Physics. Click here to buy the book. 

What if there is a single theory that can explain the physical universe? Theoretical physicist Michio Kaku discusses his new book, The God Equation: The Quest for a Theory of Everything.

Jill Tarter, former Director of the Center for SETI Research discusses the search for alien life, alien technology and technosignatures, the Fermi Paradox, risks from encountering alien civilizations, and the future of SETI and mankind.

Why, when most laws of physics allow for it to flow forward and backward, does it only go forward? What if time moves in two directions? Julian Barbour discusses his new book, The Janus Point: A New Theory of Time.

What will humanity look like 1,000 years? 10,000 years? One million years? Futurist and science fiction author David Brin discusses the future of humanity.

Roger Walsh, Professor of Psychiatry and Philosophy at UC Irvine talks consciousness, the search for wisdom, the science of meditation, the mystery of the universe and reality, and the merging of Eastern and Western philosophy.

Astrophysicist George Smoot discusses the history of precision cosmology, his work in gravitational lensing, the existence of dark matter, and the future of astrophysics.

Ken Olum, Research Professor at Tufts University talks cosmic inflation, gravitational waves, string theory, and the mystery of the Hubble Constant versus the measurements science has taken of our local universe.

Is free will an illusion? If not, how does this impact moral responsibility? Philosopher Daniel Dennett discusses his new book, Just Deserts: Debating Free Will, co-authored with Gregg D. Caruso.

Why do we dream? What is the purpose of sleep? Neuroscientist Robert Stickgold discusses his new book, When Brains Dream: Exploring the Science and Mystery of Sleep.

Donald Hoffman discusses the nature of reality, what is real, his theory of consciousness, and how this theory affects everything from artificial intelligence to alien life and the Fermi Paradox.