These mysteries define the scientific forefront, the threshold of the unknown. To explore that threshold is to gain a deeper understanding of just how far science has progressed. In The Known Unknowns, internationally known theoretical physicist and bestselling popular science writer Lawrence Krauss explores cosmology's greatest known unknowns. Covering time, space, physical law, life and consciousness, Krauss introduces readers to the topics that will shape the state of science of the next few decades, and invites us to ponder and appreciate the universe in which we live.