Watch NOVAs

Asteroid (Oct. 2006)

Will a doomsday rock the size of the Rose Bowl hit Earth in 2036? Watch now (12 mins.)

Hurricane Katrina (Oct. 2005)

Scientists' warnings proved sadly prescient about New Orleans' risk from hurricanes. Watch now (4 mins.)

Hurricanes (Jan. 2005)

Predicting a hurricane's intensity is notoriously difficult, but new tools may make it easier. Watch now (12 mins.)

Mass Extinction (Nov. 2006)

What caused the mother of all extinctions 250 million years ago? Watch now (13 mins.)

Mt. St. Helens: Back From the Dead (May. 2010)

Thirty years after the massive eruption, could it happen again? Watch now (50 mins.)

The Spy Factory (Feb. 2009)

Examine the high-tech eavesdropping carried out by the National Security Agency and the pitfalls of surveillance in an age of terrorism. Watch now (50 mins.)

Storm That Drowned a City (Nov. 2005)

Experts and eyewitnesses reconstruct the devastating floods that Hurricane Katrina unleashed on New Orleans. Watch now (49 mins.)