Horse riding played a key role in human expansion and civilization. But when and how did people first master these animals? Scientists use archaeology and genetics to uncover clues about the first horse riders and how they shaped the world.

Horse riding played a key role in human expansion and civilization. But when and how did people first master these animals? Scientists use archaeology and genetics to uncover clues about the first horse riders and how they shaped the world.

Bioarchaeologists investigate a ninth-century mass grave in a rural English village. Will the remains unlock the mystery of the "Great Heathen Army," a legendary Viking fighting force that once invaded England?

Bioarchaeologists investigate a ninth-century mass grave in a rural English village. Will the remains unlock the mystery of the "Great Heathen Army," a legendary Viking fighting force that once invaded England?

Retrace Einstein's thought experiments as NOVA reveals the simple but powerful ideas that reshaped our understanding of gravity, illuminating the theory of general relativity-and Einstein's brilliance-as never before.

Retrace Einstein's thought experiments as NOVA reveals the simple but powerful ideas that reshaped our understanding of gravity, illuminating the theory of general relativity-and Einstein's brilliance-as never before.

Retrace Einstein's thought experiments as NOVA reveals the simple but powerful ideas that reshaped our understanding of gravity, illuminating the theory of general relativity-and Einstein's brilliance-as never before.

Retrace Einstein's thought experiments as NOVA reveals the simple but powerful ideas that reshaped our understanding of gravity, illuminating the theory of general relativity-and Einstein's brilliance-as never before.

The asteroid that exploded in the skies over Siberia injuring more than 1,000 and damaging buildings in six cities was a shocking reminder that Earth is a target in a cosmic shooting range. From the width of a football field to the size of a small city, the space rocks called asteroids have the potential to be killers. But some asteroids are loaded with billions of dollars' worth of elements like iron, nickel and even platinum. While NASA plans an ambitious mission to return samples from a potentially hazardous asteroid, would-be asteroid miners are dreaming up their own program to scout for potentially profitable asteroids. Will asteroids turn out to be our economic salvation -- or instruments of extinction?

Diseases that were largely eradicated 40 years ago are returning. Across the world, children are getting sick and dying from preventable conditions because nervous parents are skipping their children's shots. How do parents decide whether to vaccinate or not, and what are the risks to the child and to society? Featuring research scientists, pediatricians, psychologists, anthropologists, and parents, this program travels the globe to look at the science behind vaccinations, track epidemics, and investigate the serious human costs of opting out.

The asteroid that exploded in the skies over Siberia injuring more than 1,000 and damaging buildings in six cities was a shocking reminder that Earth is a target in a cosmic shooting range. From the width of a football field to the size of a small city, the space rocks called asteroids have the potential to be killers. But some asteroids are loaded with billions of dollars' worth of elements like iron, nickel and even platinum. While NASA plans an ambitious mission to return samples from a potentially hazardous asteroid, would-be asteroid miners are dreaming up their own program to scout for potentially profitable asteroids. Will asteroids turn out to be our economic salvation -- or instruments of extinction?

Diseases that were largely eradicated 40 years ago are returning. Across the world, children are getting sick and dying from preventable conditions because nervous parents are skipping their children's shots. How do parents decide whether to vaccinate or not, and what are the risks to the child and to society? Featuring research scientists, pediatricians, psychologists, anthropologists, and parents, this program travels the globe to look at the science behind vaccinations, track epidemics, and investigate the serious human costs of opting out.

Bioarchaeologists investigate a ninth-century mass grave in a rural English village. Will the remains unlock the mystery of the "Great Heathen Army," a legendary Viking fighting force that once invaded England?

Retrace Einstein's thought experiments as NOVA reveals the simple but powerful ideas that reshaped our understanding of gravity, illuminating the theory of general relativity-and Einstein's brilliance-as never before.

Two intrepid pilots attempt to construct and fly the first solar-powered airplane around the world.