Renowned astrophysicist Neil deGrasse Tyson hosts this fast-paced science newsmagazine. Segments in this episode include the role of sleep in memory and learning; the attempt by physicists at CERN to find out what the universe if made of; an examination of "emergence"; and a profile of historical archaeologist Julie Schablitsky.

Renowned astrophysicist Neil deGrasse Tyson hosts this fourth installment of the fast-paced and provocative science newsmagazine, now in its second season on PBS. This episode includes:

Sleep and Memory - We spend about one third of our lives sleeping. Why? Scientists don't know for sure, but evidence is building that sleep plays a crucial role in strengthening memories and facilitating learning, not just in humans, but in all animals. Many scientists are convinced that learning and higher-level decision-making rely heavily on the unique experience sleep provides - and they worry about the state of our sleep-deprived culture.

CERN LHC - It could be the boldest experiment in all of science, one that could answer a profound question: What is the universe made of? CERN, the particle physics lab in Switzerland, is constructing a new particle accelerator, the Large Hadron Collider (LHC). With a 17-mile circumference, the structure is essentially a giant circular magnet with protons zipping around inside of it. Scientists are trying to detect the elusive Higgs, also known as the "God particle" for its essential role in particle physics, which supposedly accounts for the mass of all other particles - if only researchers could find it. With luck, the LHC will do just that and in the process answer unsettled questions about the nature of matter.

Emergence - In any large group of individuals, there is a leader with a plan, right? Well, not always. Scientists are finding that order doesn't necessarily spring from the top down. Complex group behaviors emerge spontaneously: thousands of starlings flock as one, schools of fish evade predators in what seems like a highly choreographed dance, neurons in our brains fire in rapid, coordinated succession. This phenomenon, called "emergence," is transforming math, biology, cognitive science and the way we perceive the world.

Julie Schablitsky profile - Julie Schablitsky is a historical archaeologist who focuses on the American West. She's now working in the town of John Day, Oregon, trying to tell the story of the Chinese laborers who went west in the late 1800s to work on the railroads and in the mines. Written records from or about these Chinese are scarce. Schablitsky works with a combination of written records and archaeological finds to piece together their history.