Tamara Davis is an astrophysicist who observes space in order to learn more about the physics of the world we live in. With the Universe as her laboratory, she uses the stellar and galactic experiments that the universe naturally performs to learn about the nature of gravity, spacetime, and the fundamental laws of physics. As one of most highly cited astrophysicists in the world, she is the recipient of many prizes, including the Astronomical Society of Australia's award for the young researcher with the highest international impact. She works with international teams of astrophysicists searching for the elusive ‘dark energy’ that’s accelerating the universe. Brian Greene is a professor of physics and mathematics at Columbia University, and is recognised for a number of ground-breaking discoveries in superstring theory. His books have earned him a place on the New York Times bestseller list; a finalist position for the Pulitzer Prize; and a reputation as being the ‘single best explainer of abstruse ideas in the world today’. Greene has appeared on top rating television shows, and has won Emmy and Peabody awards for his NOVA TV specials. He is co-director of Columbia’s Institute for Strings, Cosmology, and Astroparticle Physics (ISCAP); and is the co-founder of the World Science Festival. Samir Mathur is a physicist who has spent over two decades working on the black hole information paradox. He has proposed that this paradox is resolved because the structure of black holes is radically altered in string theory: Instead of having all their mass at their center, black holes are “fuzzballs” with no regular horizon or singularity. Mathur is now applying these new insights to understanding the singularity at the origin of the Universe—the Big Bang. His background is in string theory, general relativity, and astrophysics. Samir Mathur obtained his Ph.D. at the Tata Institute in Bombay, held postdoctoral appointments at the Tata Institute and Harvard, was a junior faculty at MIT, and is now a professor at Ohio State. Norna Robertson is a lead scientist with the Laser Interferometric Gravitational-Wave Observatory (LIGO) run by the California Institute of Technology. She has worked in the field of gravitational wave detection for more than thirty-five years. Robertson’s recent work has focused on the development and implementation of ultra-low noise, multiple pendulum suspensions for Advanced LIGO. She is currently working on upgrades to Advanced LIGO and on future gravitational wave detectors. Michael Turner is a theoretical astrophysicist and the Bruce V. and Diana M. Rauner Distinguished Service Professor at the University of Chicago, and is Director of the Kavli Institute for Cosmological Physics at Chicago. Turner helped pioneer the interdisciplinary field of particle astrophysics and cosmology, and his contributions include predicting cosmic acceleration and coining the term "dark energy," showing how quantum fluctuations during inflation evolved into the seeds for galaxies, and several key ideas that underpin the cold dark matter theory of structure formation.