Even before it was finished 800 years ago, the Leaning Tower of Pisa - a masterpiece of medieval architecture - began to topple, shaken by earthquakes and sinking slowly into the unstable soil. Today, the top hangs just 16 feet over the base and collapse seems imminent. NOVA follows a decade-long search for a solution to correct the lean and save the unique building

In the program, leading physicists delve into the mystery of whether time travel is possible, and if so, how one might go about building a time machine

The death of Marilyn Sheppard in 1954 is one of the most famous unsolved murders in America. The indictment of her husband, Dr. Sam Sheppard, quickly became the "Trial of the Century," then the "Re-Trial of the Century," making a celebrity out of lawyer F

In the far north of Japan, thrust out into the north Pacific, is the remote island of Hokkaido. It's a land of towering volcanoes and steaming lakes, marshy valleys and fairy tale forests. Among this magical scenery, where summers are brief and winters are fierce, lives an extraordinary spectrum of life, found nowhere else in Japan

Most historians agree that by enabling Allied commanders to eavesdrop on German plans, Station X shortened the war by 2 or 3 years. Its decoded messages played a vital role in defeating the U-boat menace, cutting off Rommel's supplies in North Africa, and launching the D-Day landings. Now, for the first time on television, a 2-hour NOVA Special tells the full story of Station X, drawing on vivid interviews with many of the colorful geniuses and eccentrics who attacked the Enigma

Buried in mud beneath the shallow waters of Matagorda Bay in Texas, lay a glorious remnant of one of the most ill-fated voyages of the Age of Discovery. After years of searching the area, nautical archaeologists doing a magnetometer survey honed in on a promising site. And on the first day of diving, they were astounded to feel the distinctive outlines of a cannon, and sense the massive size of the wreck

The program tells the story of a handful of brilliant, obsessed surgeons and researchers who have pursued the target of a practical artificial heart for decades

NOVA chronicles a year in the life of a bee colony with stunning images that take viewers inside the innermost secrets of the hive. The documentary team spent a year developing special macro lenses and a bee studio to deliver the film's astonishing sequences. These include the "wedding flight" of the colony's virgin queen as it mates in mid-air with a drone; the life-and-death battle between two rival queens for the colony's throne; and the defeat and death of a thieving wasp at the entrance to the hive

The program chronicles a successful 1999 NOVA expedition to investigate the mysterious disappearance of George Mallory and Andrew Irvine high on Everest in 1924. During this expedition, which included a NOVA/PBS Online Adventure, Mallory's body was found, though the mystery only deepened

In the film, which is a part of the NOVA series Secrets of Lost Empires, a team of timber framers and other specialists design, build, and fire a pair of trebuchets, a devastating engine of war popular in the Middle Ages

The film documents the efforts of researchers around the world to create synthetic diamonds, some of which have become so indistinguishable from natural diamonds as to fool experts

In the film, which is a part of the NOVA series Secrets of Lost Empires, NOVA brings together a team of Egyptologists, engineers, stonemasons, and timber framers to probe the mystery of how the ancients shaped, transported, and erected their elegant obelisks

The film tells the fascinating story of the invention of the Black-Scholes Formula, a mathematical Holy Grail that forever altered the world of finance and earned its creators the 1997 Nobel Prize in Economics

The film, which is a part of the NOVA series Secrets of Lost Empires, showcases the efforts of a team of archeologists, engineers, and other experts to transport an Easter Island moai, or carved stone monolith, overland and successfully raise it onto a pedestal

In 1996, near Kennewick, Washington, a suspected murder victim is identified by forensic anthropologists as Caucasian - but turns out to be almost 10,000 years old. For fifty years our picture of prehistoric America has rested on the premise that the earliest inhabitants of the Americas were east Asians of mongoloid stock, the ancestors of today's Native Americans. But the discovery of the Kennewick Man, along with several other startling finds in recent years, has thrown that once widely accepted idea into question and revolutionized the science of paleo-anthropology

In the film, which is a part of the NOVA series Secrets of Lost Empires, an international crew of archeologists, engineers, and historians designs, builds, and tests a functioning Roman bath in the Turkish countryside

At the heart of Jewish tradition lies the haunting mystery of the Lost Tribes of Israel. Ever since their defeat and banishment by the Assyrians in 722 BC., the Lost Tribes fate has inspired countless claims to Jewish ancestry by groups scattered on every continent

The film, which is a part of the NOVA series Secrets of Lost Empires, documents a 1999 effort by a NOVA-assembled crew of scholars and timber framers to design and build a Chinese bridge known only from an ancient painting

In "What's Up with the Weather?" NOVA and FRONTLINE join forces to investigate the science and politics of one of the most controversial issues of the 21st century: the truth about global warming

The broadcast explores America's manned space program and the crisis caused by Russia's delay in delivering the critical third piece of the International Space Station

In this two-hour special, NOVA presents a dramatic investigation of a people who were much more than axe-wielding pirates. It features stunning camerawork in Scandinavia and the far-flung countries that the Vikings penetrated, while historians and archaeologists present us with an image of the Vikings that goes far deeper than their savage stereotype. The latest research shows that they were canny merchants, expert shipbuilders, superb artisans, and bold colonizers of lands that lay beyond the edge of the known world