In 1986 a catastrophic blast, 400 times more potent than the Hiroshima bomb, blew the lid off Chernobyl's Reactor No. Four, igniting fires that burned for days and sending a radioactive cloud across Europe. Ill-equipped workers heroically sealed the smoldering reactor in a concrete sarcophagus, but the hastily constructed shelter was only built to last 30 years. Now, 30 countries have come together to pay for a 25,000-ton steel shelter which will...

Thousands of prehistoric footprints left by Ice Age humans and animals stretch for miles across the blinding white surfaces of New Mexico's White Sands National Park. The phenomenal collection of prints preserves a unique series of snapshots of life and behavior, capturing moments when humans crossed paths with extinct Ice Age beasts, including enormous ground sloths and mammoths.

Mighty, elemental forces, fiery eruptions, titanic floods, the grinding of great ice sheets, and massive impacts from space molded North America. This spectacular road trip through our nation's tumultuous past sets out to answer three fundamental questions: How was the continent built? How did life evolve here? And how has its spectacular landscape shaped human lives and destinies?

This two-part Nova special brings the history of cold to life with brilliant dramatic recreations of high moments in low-temperature research and the quest for ever-lower notches on the thermometer. "The conquest of cold" opens in the 1600s when the nature of cold and heat was a complete mystery. Were they different aspects of the same phenomenon? The experiments that settled those questions helped stoke the Industrial Revolution. "The race for absolute...